Prognosis
Coarctation of the aorta is a lifelong disease with a guarded prognosis. Relief of obstruction, control of hypertension, follow-up monitoring for recurrent obstruction, and follow-up care of associated anomalies are imperative.
Continue subacute bacterial endocarditis prophylaxis indefinitely, even in the absence of associated abnormalities. Patients without residual obstruction who are normotensive both at rest and with exercise should lead normally active lives without restriction. They should be able to obtain health and life insurance.
Patients with persistent hypertension, untreated residual obstruction, or other complications have a variable prognosis related to the severity of these problems.
Data regarding long-term follow-up are limited. Available studies indicate that significant mortality rates are found at long-term follow-up after surgical correction of aortic coarctation.[16] The survival curve, while not approaching that in the healthy population, is significantly improved compared with Campbell's natural history data.[17] Death appears to be secondary to recoarctation repair, aneurysms at site of coarctation repair or at a remote site, congestive heart failure, bacterial endocarditis, and hypertension. Attempts to define factors that affect long-term survival have been made; age at operation and degree and duration of hypertension prior to surgery appear to affect the long-term survival.
A study by Oliver et al indicated that in young adults who underwent aortic coarctation repair in childhood, the greatest risk factor for heart failure or cardiovascular death is pulmonary hypertension related to restrictive LV physiology. The study involved 159 adults who underwent aortic coarctation repair at mean age 4.1 years. The investigators found that those individuals with a pulmonary artery systolic pressure of over 40 mm Hg were at the greatest risk of death or of being admitted to the hospital for heart failure. Using logistic regression analysis, they also found that pulmonary hypertension in the adults studied was predicted primarily by restrictive LV physiology.[18]
The study did not find heart failure or death to be statistically associated with recoarctation, systemic hypertension, intracardiac lesions, or aortic aneurysm or with treatment with beta blockers or ACE inhibitors/angiotensin receptor blockers.[18]
Morbidity/mortality
Past autopsy studies suggest that the mortality rate in patients in whom coarctation of the aorta is not surgically repaired is 90% by age 50 years, with a mean age of 35 years.[19] In the current era, coarctation of the aorta mortality is often determined by patient age, patient size, and associated major cardiovascular anomalies.
Associated problems that may contribute to death or morbidity include hypertension, intracranial hemorrhage, aortic rupture or dissection, endocarditis, and CHF.
Complications
Coarctation of the aorta is a lifelong disease with complications that may not be evident until many years following an initial and apparently successful repair.
Recurrent coarctation
Recurrence of coarctation is associated with patient size, age at surgery, and associated transverse arch or isthmic hypoplasia. Ductal tissue in the wall of the aorta may involute and contribute to recurrence, as might scarring at the repair site. Some surgeons believe that the use of interrupted sutures in the anterior portion of the anastomotic suture line improves aortic growth and reduces the risk of recurrence. Sometimes, the surgical repair site is unobstructed, yet obstruction develops at the transverse arch or isthmus because of the failure of these areas to grow proportionally to the rest of the arch. Such obstruction may not be detected for many years after initial repair.
Some patients who have undergone initial repair with left subclavian flap aortoplasty may have a tortuosity at the repair site that does not result in obstruction until rapid growth in adolescence.
Aortic aneurysm
Aneurysm of the aorta can occur in unrepaired coarctation of the aorta and has been described in patients with Turner syndrome and coarctation of the aorta. In addition, endocarditis can result in aortic arch aneurysm (mycotic aneurysm), usually distal to the site of obstruction.
Patch repair of coarctation of the aorta results in an increased incidence of aortic aneurysm (usually opposite the site of the patch), particularly if the shelf of coarcted tissue is excised. Patients with aortic aneurysm can be entirely asymptomatic. Hoarseness that results from stretching of the recurrent laryngeal nerve associated with aortic aneurysm has been described. Chest radiographs are unlikely to reveal the aortic aneurysm, but MRI is more useful in delineating the size and extent of aneurysms.
Hypertension
Hypertension may persist, even after successful repair of coarctation of the aorta, and usually relates to the duration and severity of preoperative hypertension. This is probably related to alterations in the renin-angiotensin system and baroreceptors. As with other forms of uncontrolled hypertension, patients may be at risk for premature atherosclerosis, ventricular dysfunction, and rupture of cerebral aneurysms.
Cerebral aneurysms
Berry aneurysms of the circle of Willis or other vessels are believed to occur in as many as 10% of patients with coarctation of the aorta and may be multiple. Aneurysm size tends to increase with age, as does the risk of rupture. Uncontrolled hypertension promotes the growth of the aneurysms and increases risk of rupture. Most patients are asymptomatic until rupture occurs, although some aneurysms may leak prior to rupture, resulting in warning symptoms of headache, photophobia, weakness, or other symptoms. Rupture of a cerebral aneurysm is associated with high mortality rates and should prompt repair of both the aneurysm and coarctation.
Paralysis
Although rare, paraplegia can occur from spinal cord ischemia, resulting from a compromised blood supply to the anterior spinal artery.[20, 21] Risk of paralysis is increased with reduced arterial collateral vessels, prolonged aortic cross-clamping time, and intraoperative sacrifice of intercostal arteries, as well as other factors.
Paralysis is uncommon in the presence of a well-developed arterial collateral supply, emphasizing the importance of assessing collateral arterial flow prior to surgical intervention. Methods to prevent cord ischemia include hypothermia, use of cardiopulmonary bypass, or insertion of a bypass graft (Gott shunt) with partial aortic clamping.
Cardiomyopathy
Cardiomyopathy is usually present in infants with critical coarctation, especially if additional levels of left heart obstruction, such as aortic stenosis or subaortic stenosis, are present. Some patients may have changes of endocardial fibroelastosis that result in chronic dilated cardiomyopathy, requiring medical management or, in rare cases, cardiac transplantation. Hypertrophic cardiomyopathic changes also may occur, predisposing the patient to subendocardial ischemia, arrhythmias, or congestive heart failure (CHF) related to diastolic dysfunction.
Chylothorax
Extensive dissection at surgery may result in disruption of the thoracic duct, leading to chylothorax. Chylothorax is recognized when feedings are instituted postoperatively. Persistent chylous pleural effusions may necessitate long-term chest tube drainage. Some patients respond to dietary therapy with medium-chain triglyceride diet, fat restriction, and/or total parental nutrition. Patients with refractory chylothorax may require pleurodesis or thoracic duct ligation.
Postcoarctectomy syndrome
[22, 23, 24]
Restoring pulsatile blood flow to the mesenteric arteries may result in mesenteric arteritis, in which the arteries become distended and may rupture. Reflex arteriolar vasoconstriction occurs as part of autoregulation of blood flow and can result in ischemia.
Clinical manifestations may range from mild abdominal discomfort to an acute abdomen with severe abdominal distention, vomiting, ileus, and progression to intestinal wall hemorrhage or perforation. This syndrome may be related to early return to feeding after coarctation repair. Thus, feedings are usually delayed for 48 hours after surgery, and nasogastric tube decompression is continued until feedings are begun slowly and advanced as tolerated. Patients with severe postcoarctectomy syndrome may require exploratory laparotomy for treatment of bowel necrosis or perforation.
Careful monitoring and good control of BP in the postoperative period may reduce the risk of postcoarctectomy syndrome.
Valvar aortic stenosis, membranous subaortic stenosis, and mitral valve stenosis
These may develop during the follow-up period; if these are significant, transcatheter or surgical relief of the obstruction may become necessary.
Race
No definitive racial differences have been documented in coarctation of the aorta, although some authors have suggested that coarctation of the aorta is less common in Asians.[15]
Sex
The male-to-female ratio is 2:1, although this ratio is not valid in abdominal coarctation of the aorta, in which this rare lesion predominantly affects females. The ratio of abdominal-to-thoracic coarctation is approximately 1:1000. The male preponderance observed in older patients is not seen in infants with coarctation of the aorta.
Age
Generally, patients with coarctation of the aorta present early in life with CHF or later in life with hypertension. Studies continue to document that coarctation of the aorta is often missed in the first year of life,[25, 26] and the median age of referral to a pediatric cardiologist in one study was 5 years. Among 2192 patients reported to the Pediatric Cardiac Care Consortium from 1985-1993, 1337 were infants, 824 were children, and 31 were adults.[27]
Surgical Care
Significant hypertension or congestive heart failure (CHF) is an indication for intervention. Surgical relief of the aortic obstruction and catheter interventional techniques (balloon angioplasty and stents) are available alternatives. Symptomatic neonates and infants should undergo urgent intervention soon after the infant is stabilized. Asymptomatic infants, children, adolescents, and adults should undergo the procedure electively. If neither hypertension nor heart failure is present, elective surgical or balloon therapy in children aged 2-5 years is suggested. Waiting beyond age 5 years for surgery or balloon therapy to relieve aortic obstruction is not advisable because of the evidence of residual hypertension if intervention is performed after age 5 years.[41]
Since the introduction of surgical correction by Crafoord and Nylin (1945) and by Gross and Hufnagel (1945) in the early 1940s, surgical therapy has been the preferred treatment for aortic coarctation. Various surgical techniques have been used to treat patients with coarctation of the aorta, namely, resection and end-to-end anastomosis, patch aortoplasty, left subclavian flap aortoplasty, and tubular bypass grafts. The techniques are occasionally combined or modified to fit the individual patient's anatomy.[42]
For instance, a reverse left subclavian flap aortoplasty may be used, turning the left subclavian artery as a patch back toward the left carotid artery to enlarge an area of transverse arch hypoplasia. In addition, an extended end-to-end repair may be used, in which the segment of descending aorta is beveled and brought up to the underside of the transverse arch to enlarge areas of transverse arch hypoplasia. The exact technique used varies depending on the patient's age at presentation, size, associated abnormalities, and arch anatomy. A surgical approach from a median sternotomy, rather than the classic left lateral thoracotomy, is used commonly in complex arch repairs.
In a review of 1337 patients undergoing repair of coarctation in infancy, the following findings were reported[27] :
Subclavian flap aortoplasty was performed in 763 patients (57%). Resection in end-to-end anastomosis was used in 406 patients (30%), and patch aortoplasty was used in 133 patients (9.9%). In addition, 20 patients underwent placement of an interposition graft or bypass graft.
In the series, the mortality risk was highest in neonates in whom surgery was performed during the first week of life, whereas only 8 of 279 infants aged 3 months to 1 year who underwent surgery died. Mortality associated with surgery was also higher in smaller infants, particularly in infants who weighed less than 3 kg and infants with associated cardiac anomalies.
The presence of a ventricular septal defect (VSD) with or without minor associated anomalies increased the risk of death from 0.9% (no anomalies) to 6.8% (with VSD). Complex associated anomalies, such as a single ventricle or transposition of the great arteries, greatly increased the mortality rate to 16.6%. Similarly, the surgical mortality rate in neonates who required surgery early was high at 45%. Urgent surgery may be required if the patent ductus arteriosus cannot be opened and the patient continues to have poor urine output and acidosis.
In the presence of a hemodynamically significant VSD, historically, placement of a pulmonary artery band was performed to limit pulmonary blood flow at the time of left thoracotomy for coarctation repair. Current surgical approach uses a single-stage repair of the coarctation and VSD, usually through a sternotomy, even in the small neonate.
In severe transverse arch hypoplasia that results in significant residual obstruction following coarctation repair, an ascending-to-descending aortic conduit may be placed. This is usually a less favorable approach because the patient may be obligated to undergo subsequent surgeries for conduit replacement.
In most centers, associated defects may be addressed at the time of surgery for coarctation by proceeding with a median sternotomy to repair lesions such as mitral stenosis or subaortic obstruction or to accomplish left ventricular (LV) outflow tract enlargement. Occasionally, the adequacy of the LV volume is called into question, and the patient may require a modified Norwood repair. Decision making about this issue is addressed in Hypoplastic Left Heart Syndrome. However, note that hypoplasia of the left heart structures, particularly the LV, associated with isolated CoA usually improves following relief of aortic obstruction.[43]
Repair of coarctation in the asymptomatic child or adolescent is usually undertaken on an elective basis after assessment of associated anomalies and appropriate preoperative evaluation. The timing of intervention in the otherwise asymptomatic patient has been debated. The rationale for delaying surgery until age 3-5 years has been based on the size of the aorta in childhood relative to the anticipated adult size. Because significant obstruction occurs when the diameter of the aorta is reduced by 50% or more, delaying surgery until age 3-5 years allows the aorta to be larger than half the anticipated adult size at operation, theoretically reducing the risk of significant residual obstruction in the event that the surgical repair site does not grow over time. However, issues of hypertension, progressive LV hypertrophy, or LV dysfunction mandate earlier repair.
Improvements in surgical techniques have led most cardiologists to recommend surgery at the time of diagnosis, especially in patients with hypertension. In patients with only mild obstruction, especially those diagnosed in the first year of life, surgery may safely be delayed and the patient monitored for worsening obstruction or development of hypertension prior to recommending surgery.
Pseudo-coarctation of the aorta refers to abnormal tortuosity of the aorta that does not result in significant obstruction or hypertension and is noted for the lack of development of collateral vessels. This abnormality does not require surgical intervention.
Surgical repair of coarctation of the aorta is accomplished in children and adolescents with generally good results and low mortality. Of 824 patients who underwent coarctation repair in childhood, 431 (52%) underwent end-to-end anastomosis, whereas patch aortoplasty was performed in 214 patients (26%) and only 109 patients (13%) underwent subclavian flap aortoplasty. Death occurred in only 6 of 824 patients for a total mortality rate of 0.73%.[27] The surgical era of this cohort does not reflect the current surgical strategy for aggressive complete arch repair or the aorta and all associated lesions. The trend is toward the less frequent use of patch aortoplasty because of concerns regarding the development of aortic aneurysm at the site of repair.[44, 45, 46, 47]
Operative mortality rates in neonates and infants are high (4-50%), whereas the operative mortality rates in older children are low (0-5%). The high mortality in the young infant appears to be related to the condition of the infant at the time of surgery and the associated defects.
Significant recoarctation (6-33% in infants, 0-18% in older children)[37, 48] ; formation of aneurysms in all types of coarctation repair,[44] particularly well-documented following prosthetic patch angioplasty[48, 49] ; development of paraplegia[20, 21, 50] ; paradoxical hypertension[22, 23, 24] ; and vascular complications related to subclavian flap repair[51, 52, 53, 54, 55] continue to be problems.
In a study examining long-term results of surgery by MRI of 247 patients aged 33.0 ± 12.8 years, restenosis (mild in 31% and significant in 9%) and dilatation of the aortic segment (13%), with discrete aneurysm at the repair site in 9%, was observed. However, antihypertensive therapy was required, which controlled the blood pressure in 93% patients.[56] Mortality rate was low, but significantly higher than age-matched healthy controls.
Late hypertension continues to be a problem.[57]
Despite these problems, surgical repair is considered by many to be the therapeutic option of choice in the treatment of aortic coarctation. Some groups of workers, including the authors' group, consider balloon angioplasty the initial therapy of choice and reserve surgical intervention for the following coarctations:
Coarctations that involve the long segment of the aorta
Coarctations that are completely or almost completely occluded so that no catheter or guide wire can be passed across the coarcted segment
Coarctations that are associated with a large patent ductus arteriosus and ventricular septal defect that requires prompt surgical intervention for the primary cardiac problem.
Balloon angioplasty
Gruntzig's technique of balloon angioplasty was adopted by Sos et al (1979), Singer et al (1982), and Sperling et al (1983) for enlargement of coarcted aortic segments in a postmortem specimen, postsurgical recoarctation, and native coarctation, respectively. Other cardiologists then used this technique to treat native coarctation of the aorta. Numerous investigators reported their experiences with balloon angioplasty of native aortic coarctations. However, the use of balloon angioplasty for treatment of native aortic coarctation is controversial.[1, 58] This section describes the technique and the results of balloon angioplasty.
Technique
[15, 48, 59]
Cardiac catheterization and selective cineangiography are performed to confirm the clinical diagnosis, to exclude other cardiac defects, and to assess suitability for balloon angioplasty. Once balloon angioplasty is chosen, a 4F-6F multi-A2 (Cordis) catheter is introduced into the femoral artery percutaneously and is positioned across the aortic coarctation. Then, a 0.021-0.035 in J-tipped guide wire is passed through the catheter into the ascending aorta and the tip of the wire positioned in the ascending aorta. A 4F-7F balloon angioplasty catheter is then positioned across the aortic coarctation. The balloon is inflated with diluted contrast material to approximately 3-5 atm of pressure or higher, depending on the manufacture's recommendations.
Monitoring pressure of inflation via any of the commercially available pressure gauges is recommended. The balloon is inflated for 5 seconds. A total of 2-4 balloon inflations are performed 5 minutes apart. Aortography and measurement of pressure gradients across the coarctation of the aorta are performed. The heart rate, systemic pressure, and cardiac index are recorded prior to and 15 minutes after balloon dilatation to ensure that the change in pressure gradient is related to balloon dilation rather than changes in patient status.
The author generally performs this procedure with the patient under conscious sedation, whereas others advocate general anesthesia. Most cardiologists use percutaneous femoral artery approach for cardiac catheterization and balloon angioplasty. Occasionally, femoral artery cutdown or left axillary artery cutdown is necessary if the percutaneous approach is unsuccessful. The authors and others have used a transumbilical approach in neonates in an attempt to avoid the use of the femoral arteries.[15, 60] In patients in whom the aorta can be entered from the right ventricle (either directly in patients with transposition of the great arteries or double outlet right ventricle or indirectly through a ventricular septal defect), balloon angioplasty may be performed transvenously.
The size of the balloon chosen for angioplasty is 2 or more times the size of the coarcted segment, but no larger than the size of the descending aorta at the level of the diaphragm, as measured from a frozen video recording. The authors usually choose a balloon that is midway between the size of the aortic isthmus (or transverse aortic arch) and the size of the descending aorta at the level of diaphragm. If the relief of obstruction is not adequate (pressure gradient reduction to < 20 mm Hg and angiographic improvement), a balloon as large as the diameter of the descending aortic at the level of diaphragm is chosen for additional dilatation.[48, 61]
The authors usually give 100 U of heparin per kilogram prior to introducing the balloon-angioplasty catheter. Activated clotting times should be measured every 30 minutes and maintained between 200 and 250 seconds. The heparin effect is neither reversed nor continued after the procedure. Administering adequate doses of heparin to prevent thromboembolism is important.[48, 62]
The balloon inflation pressure should be monitored and attempts should be made not to exceed that stated by the manufacturer; this is to prevent balloon rupture and its adverse effects.[37, 48]
A catheter or a guide wire must not be manipulated over the site of a freshly dilated coarctation of the aorta. A guide wire should always be left in place across the coarctation segment, and all angiographic and balloon-dilatation catheters should be exchanged over the guide wire.
Balloon size should be carefully chosen to prevent aneurysm.
Use of large-caliber angioplasty catheters may result in significant femoral artery compromise. Availability of balloon catheters that can be introduced through 4F sheaths appears to reduce the femoral artery injury. Even these may injure the femoral artery in the young infant; in such situations, the authors use 3F sheaths through which the more recently available balloon dilatation catheters (eg, Mini-Tyshak [Braun] catheters) can be introduced, which may further reduce such complications.
Short-term results
Despite an initial report of poor results,[63] subsequent experience with balloon angioplasty appears encouraging and has been detailed elsewhere.[32, 37, 48, 64, 65, 66] A reduction of pressure gradient across the coarctation and an increase in the size of the coarcted segment have been observed. The collateral vessels promptly diminish. The femoral pulses, which had been either absent or markedly reduced and delayed (when compared with brachial pulses) become palpable with increased pulse volume after balloon angioplasty.
The infants who were in heart failure improved, as did their hypertension. The infants who were ventilator dependent could be weaned off of the ventilator support and were extubated. Most infants (beyond the neonate period) and children are discharged from the hospital within 24 hours after balloon angioplasty. None of the authors' patients required immediate surgical intervention.
Intermediate-term follow-up results
Several investigators have reported 1-year to 2-year follow-up results, and these studies suggest continued improvement. From the authors' study, 60 patients (58 catheterization, 2 clinical) were observed; the residual gradients 14 ± 11 (mean ± standard deviation [SD]) months following angioplasty remained low at 16 ± 15 mm Hg.[67] These gradients continue to be lower (P< .001) than those prior to angioplasty (46 ± 17 mm Hg) and are slightly higher (P< .05) than the gradients (11 ± 9 mm Hg) immediately following angioplasty. The angiographically measured coarctation segment remained wide. Only a modest increase is found (11 ± 9 vs 16 ± 15 mm Hg; P< .05) in peak gradients for the group as a whole, but, when individual patient values are examined, 15 (25%) of the 60 patients had evidence of recoarctation, defined as a peak-to-peak systolic pressure gradient in excess of 20 mm Hg.
The incidence of recoarctation is higher in neonates (5 [83%] of 6; P< .01) and infants (7 [39%] of 18; P =.011) than in children (3 [8%] of 36). Ten of these children underwent repeat balloon angioplasty, and their gradients were reduced (P< .001) from 39 ± 11 mm Hg to 10 ± 6 mm Hg.[67] Early in the authors' experience, 2 patients underwent surgical resection with good results. The final 3 children had no discrete narrowing and had no hypertension; therefore, no intervention was recommended. Aneurysms developed in 3 (5%) of 58 patients who underwent follow-up angiography; one of these patients required surgical excision of the aneurysm and the other 2 are observed clinically.
Similar high recoarctation rates were documented by our group[68, 69] in neonates and infants less than three months of age, but balloon angioplasty provided successful and effective palliation in 92% infants.
Long-term follow-up results
Only scant data can be found on long-term follow-up after balloon angioplasty of native coarctation. Despite recoarctation and aneurysms, some requiring repeat intervention at intermediate-term follow-up, the long-term follow-up results (5-9 y) appear encouraging, in that minimal incidence of late recoarctation and no late aneurysm formation was found.[58, 70, 71]
Event-free survival curves following initial balloon angioplasty suggest that the event-free rates are better (P< .001) in children than in infants and neonates. In most children, the arm blood pressure remained normal and the blood pressure–determined gradient between arms and legs remained low.[67]
Applicability in adult patients
Although balloon angioplasty of aortic coarctation has most frequently been used in neonates, infants, and children, it can also be used in adult patients.
Lababidi et al (1984) were the first to apply this technique in a 27-year-old man, resulting in reduction of peak systolic pressure gradient across the coarctation (from 70 to 15 mm Hg), angiographic improvement, and reduced hypertension (190/124 mm Hg vs 130/80 mm Hg). They subsequently reported their experience with balloon dilatation of native coarctation in 8 consecutive adults, aged 19-30 years (25 ± 5 y).[72] The systolic pressure gradient across the coarctation was reduced from 48 ± 19 mm Hg to 7 ± 5 mm Hg. The size of the coarcted segment increased from 6.8 ± 2.2 mm to 15.2 ± 5 mm. No complications were encountered. Clinical and echo-Doppler follow-up one year after the procedure revealed good results, with no more than 15 mm Hg peak systolic blood pressure difference between the arms and the legs (measured by cuff). They concluded that results in young adults are similar to those observed inchildren,balloonangioplastyshouldbeconsideredasanoptiontosurgicalintervention, and follow-up studies (>1 y) are required.
Other reports followed, which revealed equally good results.[73] Based on a review of these studies, aortic perforation during the procedure and aneurysmal formation at follow-up are also apparent in adults. In addition, intimal dissection that persisted at 6-month follow-up was seen in one patient. Therefore, (1) avoiding manipulation to the tips of the catheters and guide wires in the region of freshly dilated coarctation, (2) choosing an appropriate-sized balloon (no larger that the diameter of the descending aorta at the level of the diaphragm), and (3) monitoring for the development of aneurysms and, if found, closely following the progression of aneurysms with repeated angiography or MRI are prudent guidelines. Twenty-year follow-up for discrete coarctations appear encouraging.[74]
Surgery compared with balloon therapy
Scant data are available to compare surgical intervention with balloon angioplasty. In an attempt to compare the safety and efficacy of balloon angioplasty with surgical correction of aortic coarctation, the authors scrutinized 49 papers (published from 1980-1991) that reported on results of surgery in infants younger than 1 year and 9 papers that compared the results of balloon angioplasty in children.[37, 48] These data showed that recoarctation rates are similar, whereas the mortality rates are slightly higher in the surgical than the balloon angioplasty series. Similar comparison of results in children older than 1 year showed identical results.
Shaddy and associates (1993) prospectively randomized 36 patients aged 3-10 years to undergo either balloon angioplasty (20 patients) or surgery (16 patients) and found similar immediate pressure gradient relief in both groups.[75] The risks of aneurysm formation and restenosis were higher in the balloon angioplasty group, whereas risks of neurologic complications were higher in the surgical group. They concluded that balloon angioplasty in coarctation of the aorta may provide an effective initial alternative to surgery in children beyond infancy and suggested that further follow-up is needed to evaluate the long-term risks of aneurysms following angioplasty.
The senior author compared the efficacy and safety of balloon angioplasty with those of surgical correction in infants younger than 3 months.[38] Data on 29 infants who underwent intervention for aortic coarctation from 1982-1992 were examined. Fourteen infants underwent surgical repair, and 15 underwent balloon angioplasty. The data indicated that the degree of relief of aortic obstruction and the frequency with which reintervention is needed are similar in both groups. However, balloon angioplasty carries lower morbidity rates and complications than with surgical therapy. Based on these data, the we suggested that balloon angioplasty may be an acceptable alternative to surgery in the treatment of symptomatic aortic coarctation in infants younger than 3 months.
Shim and colleagues (1997) compared hospital charges and found lower charges for patients who underwent balloon therapy compared to surgery.[76]
Complications such as paraplegia[20, 21, 50] and paradoxical hypertension[22, 23] are seen following surgical repair, although such complications are rare and, if present, very mild and inconsequential following balloon angioplasty. Aneurysms following balloon angioplasty[48, 77, 78] are of concern and need further study, although such aneurysms are also seen with surgical repair.[44] The femoral artery occlusion rate following balloon angioplasty may be higher than that seen with surgical therapy. However, vascular complications can occur in the left upper limb following coarctation repair with subclavian flap aortoplasty; these complications include gangrene, reduction in the length and muscle mass of upper arm and forearm, and abnormal Doppler blood flow velocities in brachial arteries, suggesting potential for symptoms of ischemia.[51, 52, 53, 54]
Cowley et al (2005) compared long-term (mean, 10-11 y) results of balloon angioplasty with those of surgery for patients with native aortic coarctation who were randomized at entry into the study and found similar resting blood pressures, residual gradients across the coarctation, exercise performance, aortic arch anatomy based on MRI angiography, and reintervention rates.[79] However, the incidence of aneurysms and greater arm-to-leg blood pressure difference during exercise was higher in the balloon group than in the surgery group.
Cowley et al suggested that surgery is preferable to balloon angioplasty in the management of aortic coarctation in children. Although randomization is a virtue of the study, the study involves only 36 children, with only 21 (58%) returning for reevaluation. Furthermore, other studies in which a larger number of balloon angioplasty procedures were evaluated at long-term follow-up revealed 5% aneurysm formation. Aneurysm formation was also detected in surgical patients. Consequently, a multi-institutional randomized study with a larger number of subjects is in order to resolve the issues brought out by this paper.[73]
Rodés-Cabau et al (2007) compared transcatheter and surgical treatment and concluded that immediate results were similar, but with reduced morbidity and duration of hospitalization with transcatheter intervention.[80] However, angioplasty was associated with a higher rate of reintervention and aneurysm formation.
Wong and associates (2008) used decision analysis to compare preferences for balloon angioplasty versus surgery and concluded that balloon angioplasty is preferred over surgery as the initial treatment for native aortic coarctation in children; however, this type of decision analysis approach was questioned.[81]
Based on the above review, the effectiveness of balloon angioplasty appears to be comparable with that of surgery; the mortality rates are similar (and are probably related to the associated cardiac defects, not related to type of intervention performed), and morbidity and complication rates are lower with balloon angioplasty than with surgical therapy. Balloon angioplasty may be an effective alternative to surgery for the relief of aortic coarctation.
Recoarctation
Residual and recurrent obstructions cannot be easily distinguished, and the term recoarctation may be used to describe both entities. Recoarctation is defined as a peak-to-peak systole pressure gradient in excess of 20 mm Hg with or without angiographically demonstrable narrowing.[82] Recoarctation following both surgical correction and balloon angioplasty has been described.
Recoarctation following surgery does not depend on the type of surgical repair[44, 48] ; it has been observed following resection with end-to-end anastomosis, subclavian flap angioplasty, prosthetic patch repair, subclavian artery turn-down procedure, and interposition tube grafts. The reported incidence of recoarctation has varied depending on the study. The average recoarctations rates were 11-17% in neonates and infants younger than 1 year and 5.6% in children older than 1 year. In a large cohort of patients studied by Pinzon et al (1991), recoarctation occurred in 23%.[44] Recent reports demonstrate similar recoarctation rates.[83, 84] The younger the child at surgery, the higher the chance for recoarctation.
Although no consensus has been reached in regard to the method of intervention (surgery vs balloon angioplasty) for native aortic coarctation, both cardiologists and cardiovascular surgeons generally agree that balloon angioplasty is the treatment of choice for postsurgical aortic coarctations.[48, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94] The immediate and follow-up results of balloon angioplasty for postsurgical recoarctation are essentially similar to those of native coarctations and have been reviewed in detail elsewhere.[71]
Restenosis following balloon angioplasty also appears to be age dependent; the younger the child, the greater the chance for recoarctation.[58] The authors[58, 64] and others[70] recommend repeat balloon dilatations in such cases, whereas others[95] prefer surgical intervention.
The technique of balloon angioplasty for the management of both postsurgical and post–balloon angioplasty recoarctations is similar to that described above for native coarctation.[64]
Conclusions
Based on an extensive review of the literature and personal experience with the procedure for more than 25 years, some generalizations with regard to balloon therapy may be made, as follows.
Children older than 1 year and adults with discrete native coarctation are candidates for balloon dilatation. Most cardiologists agree on this issue. Long-segment coarctations or those associated with significant isthmic hypoplasia may be candidates for stent placement, especially in adolescents and adults.
Recurrent coarctation following previous balloon angioplasty may be treated with repeat balloon angioplasty; others prefer surgery. If the recoarcted segment is long, surgical treatment in younger children and stents in adolescents and adults seem appropriate.
Treatment of coarctation in neonates and infants is perhaps the most controversial issue. Many cardiologists prefer surgical intervention, whereas a few cardiologists may opt for balloon angioplasty.
Balloon angioplasty is useful in the treatment of extremely ill neonates and infants with severe coarctation; in this subset of patients, the balloon angioplasty has a significant advantage over a surgical approach.
Most cardiologists and surgeons agree that balloon angioplasty is the treatment of choice for postsurgical recoarctations.
Aortic stents
Vascular stenotic lesions can be opened with balloon angioplasty, but, because of the elastic recoil of the vessel wall, the vessel lumen may return to the predilation size following withdrawal of the balloon catheter. Such recoil and vascular dissection following balloon dilatation can be circumvented with implantation of endovascular stents. Dotter (1969), in the late 1960s, suggested this concept and implanted spiral coil-spring prostheses into the experimentally produced peripheral artery stenotic lesions. The stent concept and technology were dormant until the early 1980s, when the balloon-expandable and self-expanding stents were designed and used.[96] Initially, stents were used in the treatment of peripheral arterial disease and coronary artery stenotic lesions in adults. The technique was then extended to the treatment of other stenotic vessels, including aortic coarctation.[61, 97]
Despite reasonably good short-term and long-term results of balloon angioplasty, some problems remain, including restenosis, probability of aortic rupture, formation of aneurysms, and inability to effectively treat long-segment tubular narrowing. Because of these and other reasons, endovascular stenting of aortic coarctation has gained acceptance over the last decade.[60, 91, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119]
The following are perceived advantages of stents over balloon angioplasty:
The ability to expand tubular long-segment coarctation, hypoplastic isthmus, and the distal transverse aortic arch
The ability to increase the coarcted segment diameter independently of the intimal tear
The ability to decrease the probability of restenosis
The ability to prevent dissection of the torn intimal flap by facilitating apposition of the intima against the media
The ability to prevent aneurysms because of the support of the weakened aortic wall with the stent and neointima
O'Laughlin et al (1991) were the first to use a stent for the treatment of aortic coarctation, although the results in a 12-year-old child were marginal. Subsequently, numerous others reported the use of a stent in aortic coarctation with encouraging results.[61, 64, 91, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 117, 118, 119]
Because of growth issues and the need for large sheaths for implantation, most cardiologists limit stent usage to adolescents and adults. The following are indications for using stent:
Long-segment coarctation
Associated hypoplasia of the isthmus or aortic arch
Tortuous coarctation with malalignment of the proximal and distal aortic segment
Recurrent aortic coarctation or an aneurysm following prior surgical or balloon therapy
Technique
The procedure may be performed under conscious sedation or under general anesthesia. Cardiac catheterization is performed to confirm the clinical and echocardiographic diagnosis and to exclude other cardiac defects. Pressure gradients across the coarctation and selective cineangiography in multiple angiographic projections are initially performed to demonstrate the stenotic lesions.[60]
The following measurements are made: (1) the diameter of the stenotic lesion, (2) the diameter of the aorta proximal and distal to the obstructive segment, and (3) the length of the vessel that can be stented. All the measurements are made in 2 orthogonal views and averaged. Foreshortening of the vessel length is taken into account based on the anatomy. These measurements are used in the selection of expanded diameter and length of the stent. Heparin (100 U/kg) is administered, and activated clotting times are monitored and maintained between 200-250 seconds by giving additional doses of heparin, as needed.
An end-hole catheter (5F-6F multi-A2) is positioned across the coarctation with the help of a soft-tipped 0.035-in Bentson guide wire. The guide wire and catheter are advanced into the ascending aorta. The tip of the catheter may also be placed in the right or left subclavian arteries, depending on the location and angulation of the coarcted segment. The catheter is left in place, and the guide wire is removed and replaced with either an extra-stiff exchange-length 0.035-in Amplatz or a super-stiff, short tip, Amplatz guide wire. The catheter is then removed.
If the approach to the lesion is tortuous or difficult to reach, the authors select a 0.038-in super-stiff Amplatz wire. An appropriate-sized long blue Cook sheath with a multipurpose curve and a radiopaque marker at the tip is introduced over the stiff wire. Once the tip of the sheath is past the site intended to be stented, the dilator is removed and the sheath flushed. Sometimes, the dilator has to be withdrawn slightly to position the tip of the sheath at the desired location.
The selection of the sheath diameter obviously depends on the size of the stent delivery catheter. The authors have always attempted to select a balloon delivery system that would allow the smallest possible sheath diameter. Initially, when other workers were using Meditech PE-MT balloon catheters, which required 11F sheaths, the authors were using Olbert balloon catheters, which can be introduced through 8F or 9F sheaths for mounting the stent. Subsequently, the authors have used Bridge stents, which can also be delivered via 8F or 9F sheaths.[60] Most recently, the authors used IntraStent DoubleStrut stents and Palmaz Genesis.[116] The latter stents are mounted on balloon-in-balloon (BIB) catheters. The size of the sheath used is 1F larger than the sheath size needed for the BIB catheter.
The selected stent is hand crimped onto a BIB catheter; the authors use a sterile umbilical tape to further crimp the stent onto the balloon.
The balloon catheter, with the stent mounted on it, is advanced over the stiff guide wire but within the sheath and positioned across the coarctation segment. The tip of the sheath is withdrawn distal to the aortic coarctation based on bony landmarks. Contrast is also injected via the side arm of the blue Cook sheath, and the position of the stent is adjusted as necessary. Some cardiologists place catheters into the ascending aorta via trans-septal route or from radial artery for angiography during stent placement.[120] Although this may provide better visualization, the authors do not routinely recommend it to avoid additional time in the catheterization laboratory and morbidity associated with such additional procedures.
In cases in which the BIB catheter is used, the inner balloon is inflated at the manufacturer's recommended pressure and the position of the stent adjusted, if needed, followed by inflation of the outer balloon, thus implanting the stent. The balloon catheter is then advanced slightly, centering the balloon across the proximal end of the stent, and the outer balloon is re-inflated to ensure apposition of the stent against the vessel walls. The balloon catheter is then centered over the distal end of the stent. This is performed by advancing the tip of the sheath over the deflated balloon into the stent to prevent inadvertent displacement of the stent.[121] The outer balloon is then re-inflated to ensure apposition of the distal stent against the vessel walls.
If the outer balloon diameter is not as large as the desired diameter of the stent, additional balloon expansion with larger diameter balloons is performed. The author always tries to avoid this step by using an outer balloon of the BIB catheter at the desired diameter. Following the removal of the balloon catheter, a multitrack catheter[122] is positioned over the wire, and pressure pullback tracings and angiography are performed to assess the results of stent implantation.
The effect of heparin is not reversed, and no additional doses of heparin are administered. Intravenous cefazolin 25 mg/kg/dose (maximum of 1 g) is started in the catheterization laboratory, and 2 additional doses are administered at 6- to 8-hour intervals. Aspirin in platelet-inhibiting doses (5-10 mg/kg/d) is started on the day following the procedure and continued for 6 weeks. Use of heparin overnight on the day of procedure and more potent platelet-inhibiting drugs or anticoagulation with warfarin (Coumadin) have been undertaken in the past. At present, the data do not indicate the need for intensive anticoagulation. Aspirin alone appears to suffice. However, more potent platelet-inhibiting drugs, such as clopidogrel, may be used in adults.
To avoid potential balloon rupture, the tip of the guide wire is placed in the right subclavian artery instead of the ascending aorta, which is the usual practice for balloon angioplasty. Try not to position the stent across the origins of left common carotid artery and left subclavian artery. However, on occasion, avoiding the subclavian artery is impossible. In such situations, the authors have carefully traversed the stent cells (in between the struts) with a soft guide wire followed by a multi-A2 catheter. The stent cell is then dilated with an angioplasty balloon of a diameter equal to that of the proximal left subclavian artery; uncompromised flow to the left subclavian artery was found in these patients. Predilation of the coarcted segment with balloon angioplasty prior to stenting is no longer recommended.
Immediate results
The reduction of peak systolic pressure gradients and an increase in the diameter of the coarcted segment have been demonstrated following stent implantation.[60, 73, 88, 99, 100, 101, 102, 103, 104, 105, 106, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 123] Stenting was found to be effective in postsurgical and postballoon recoarctations, as well as in native coarctations. The ratio of diameters of coarcted segment to the descending aorta at the level of the diaphragm increased to unity in many patients who undergo aortic stenting. Improvement in the size of hypoplastic isthmus or transverse aortic arch and exclusion of the aneurysm, if present, also occurred after stent placement.
In the first series of 10 patients published by Suarez de Lezo et al in 1995,[100] the peak systolic pressure gradient across the coarctation decreased from 43 ± 12 to 2 ± 3 mm Hg (P< .001). The ratio of isthmus/descending aorta increased from 0.65 ± 0.14 to 1 ± 0.08 following the procedure. Similar results have been reported subsequently by other investigators.[68, 73]
Complications
Vessel disruption,[100] displacement of stent,[100, 106, 108, 113, 124] stent fracture,[125] and aneurysms[104, 106] are rare but do occur. Balloon rupture that results in inadequate stent expansion and stent migration has been reported but may be prevented by avoiding curvature of the balloon or stent assembly, the use of newer stents with less injurious ends, and the use of BIB catheters.[99, 113]
Because of the large size of the sheath required, loss of pulse and bleeding from a puncture site may occur. Use of vascular closure devices may help circumvent this problem. Rare complications included myocardial infarction and retroperitoneal hemorrhage.
Follow-up results
Most studies had only a short-term and incomplete follow-up in a limited number of patients. However, a few studies examined results of more than 20 patients at a mean follow-up of 2 years or longer.[106, 109, 112, 113, 123] The pressure gradients across the coarctation site (blood pressure, Doppler, or catheterization) remained low, and systemic hypertension decreased both in degree and frequency with the consequent decrease in the need for antihypertensive medications. No evidence for recoarctation, aneurysmal formation, or stent fracture or displacement was observed in most studies, although no systematic or complete follow-up was achieved in most studies. In some studies new aneurysms (in 6% of patients), stent fractures and jailed or partially covered brachiocephalic vessels were seen.[126]
Residual or recurrent obstruction was present in a few patients, and, in these, successful redilatation with larger balloons was accomplished. Detailed angiographic studies by Suarez de Lezo et al (1999) revealed no detectable neointimal proliferation in 75% of patients; in the remaining patients, focal neointimal ridge formation was observed at the ends of the stent, causing minimal restenosis.[106] Segmental analysis of the aorta revealed an increase in nonstented segments of the aorta, consistent with normal growth. Two young patients (7%) developed small new aneurysms that were obliterated by coil placement following angiographic detection. However, the overall follow-up results were encouraging.
Comments
Note the following:
Stent therapy appears to be an attractive method for the treatment of recurrent coarctation or aneurysm formation following prior surgical or balloon intervention and for long-segment hypoplasia. Most cardiologists use stents in adolescents and adults, although a few have advocated their use in younger children.[106, 127, 128] The selection of the type of stent and the type of balloon catheter used for stent deployment appears to be evolving. Balloon-expandable stents are preferred over self-expandable stents. However, some workers used self-expandable stents successfully.[129]
The use of a BIB catheter for stent delivery appears to be gaining momentum in an attempt to prevent balloon ruptures and perforation of other cardiovascular structures.
Positioning the guide wire into the right or left subclavian artery may avoid excessive curvature and, thus, may prevent balloon rupture.
Flexible instead of rigid Palmaz stents are being used.
Selected stent diameter at implantation should be at least twice the diameter of the narrowest aortic segment to prevent stent displacement during implantation.
The issues related to placement of the stent across the mouths of the arch vessel still need to be resolved.
Relief of obstruction both short-term and at follow-up with a low incidence of major complications is well demonstrated in several studies.
Meticulous attention to the technique and adoption of new technology, when it becomes available, may further reduce the incidence of complications.
Recoarctation rate at follow-up appears to be low. Re-expansion of the stent to treat residual or recoarctation and growth-related narrowing appears feasible, safe, and effective, although this is based on limited experience.[130]
The few studies that have compared balloon angioplasty with stents suggest that stents may be more effective.[117, 131, 132] Similar comparison between surgery and stents indicate stenting for native coarctation of the aorta is an effective alternative to surgical intervention in older children.[133, 134]
Based on the available data, stenting aortic coarctation appears to be the preferred alternative to surgical or balloon therapy in adolescents and young adults.
Covered stents
Experience in the use of covered stents to manage aortic coarctation is limited.[126, 135, 136, 137, 138, 139, 140, 141] Different types of stents to treat aortic coarctation have been used and include Jostent grafts, C-P stents, and AneuRx. Although these stents are available outside the United States, none are yet approved for clinical use by the US Food and Drug Administration (FDA). However, customizing and off-label use of available endoluminal grafts are feasible, when necessary.[142] The indications for intervention are similar to those used for balloon angioplasty and deployment of the standard stent.
The indications for use of covered stents include postangioplasty aneurysm, tortuous aortic arch and isthmus, associated patent ductus arteriosus, prior surgical conduit, Takayasu arteritis, and extremely narrow (subatretic) coarcted segment. When the assessed risk for development of aneurysm or dissection is high, a covered stent should be used. The results of the limited use of covered stents appear to be good.[126, 135, 136, 137, 138, 139, 140, 141] Some of the stents can be expanded to only an 18-mm diameter. In addition, the stent shortens when expanded to larger diameters. Use of covered stents has another disadvantage in that the vessels that arise from the aorta are blocked.
Aortic rupture remains an important, though an infrequent, complication following primary stenting for aortic coarctation. Covered stents have been used to reduce this risk. However, aortic rupture has been reported even with covered stents.[143]
Renarrowing of covered stents has been reported, and data in limited number of patients suggest Covered Cheatham-Platinum stents can redilated.[144]
A comparison between bare and covered Cheatham-platinum stents in a randomized clinical trial of 120 patients, aged 23.60 ± 10.99 years at a follow-up duration of 31.1 ± 19.2 months revealed a higher prevalence of recoarctation in bare metal stents and greater occurrence of pseudoaneurysm in covered stents; neither of these achieved statistical significance, however. Number of subjects with normal blood pressure increased in both groups.[145] Collapse and infolding of the covered stents can occur with the use of covered stents, requiring placement of additional stents.[146, 96]
Based on the currently available data, the covered stents may be useful in highly selected patients with aortic coarctation.
Comparison of different treatment modalities
In a multi-institutional study of 350 patients, Forbes et al[147] compared surgery, balloon angioplasty, and stent implantation for treatment of native aortic coarctation and demonstrated improvement in all 3 groups both acutely and at follow-up. However, the stent group had fewer complications (compared with surgical and balloon angioplasty patients), shorter hospitalization (compared with surgical patients), and lower coarctation gradients at follow-up (compared with balloon patients), but had higher “planned” reintervention (compared with surgical and balloon patients).
The study[147] is flawed in that there were a disproportionally large number of patients in the stent group (217, stent; 61, balloon angioplasty; 72, surgery), small number of patients followed (35.7%, with less than 75% of these patients having had imaging studies), and presumed noninclusion of all eligible patients into the study. Significant age and weight differences (P< .001) between study groups were found, although the authors attempted to address this issue by including an analysis of a subgroup of patients aged 6-12 years. Equally disturbing is the nonrandomized nature of the study. The authors, however, correctly concluded that these results should be interpreted with caution, which could be amended to “great” caution.
Instead of debating which treatment is better, it is prudent to tailor the treatment depending on the age of the patient and the pathology (anatomy) of the coarctation and the surrounding region. Most cardiologists prefer surgical intervention for treatment of neonatal and infant (< 1 y) coarctations. Children older than 1 year with discrete native coarctation are candidates for balloon dilatation. If the coarctation segment is long, surgical treatment in younger children and stents in adolescents and adults would seem appropriate.
Future directions
Causes of recoarctation following balloon angioplasty have been extensively investigated,[82, 148, 149] and factors predictive of recoarctation have been identified and include young age and severely narrowed isthmus and coarcted segment. More recently, studies of biophysical characteristics of the coarcted segment revealed less recoil in the subset of recoarctation patients, implying that the elastic properties of the aortic wall are not preserved.[150] This may be related to cystic medial necrosis[151, 152] or to extension of the ductal tissue into the aortic wall.[152, 153, 154]
However, the true cellular pathophysiologic mechanisms responsible for recoarctation have not been identified. Once they are identified, appropriate treatment algorithms to prevent recoarctation could be developed to address the pathophysiology. Until such time, keeping coarcted segments open with stents is an attractive option. Unfortunately, the stents, which are metallic, do not grow with the child and cannot be used routinely in neonates and infants.
Biodegradable stents[155, 156] may offer a solution; these stents keep the coarcted aortic segment open for a 3-month to 6-month period, after which the stents dissolve. By then, the ratio of the normal aortic tissue to abnormal tissue may be in favor of the infant, thus preventing recurrence of significant narrowing. However, this hypothesis should be tested in appropriate animal models and stent delivery systems miniaturized so that they can be used in neonates and young infants. Similarly growth stents[157] may allow re-dilatation at a later date.
Summary of treatment
At initial presentation, if cardiac failure or hypertension is the presenting problem, it should be addressed to stabilize the patient. Subsequently, the aortic obstruction should be relieved. The available options include surgical and catheter interventional procedures; the latter procedures include balloon angioplasty and bare or covered stents.
In general, surgical intervention in neonates and young infants (extremely ill babies with poor left ventricular function may benefit from balloon angioplasty), balloon angioplasty in children, and stent deployment in adolescents and adults appear to be appropriate options. Of course, the anatomy of the coarcted aortic segment and the aortic arch would greatly influence the method of therapy in a given patient.
){kind=link}
){kind=link}