The optimal management strategy of the neonate and young infant with native aortic coarctation (AC) is controversial. We reviewed our experience with balloon angioplasty (BA) in neonates and infants <= 3 months to test our thesis that BA provides successful palliation, defined as avoidance of surgery for >= 4 weeks along with control of presenting symptoms. We also compared the results of the transumbilical arterial (UA), transfemoral arterial (FA) and transfemoral venous anterograde (FVA) approaches we have used to accomplish BA. During a 6.5-year period ending June 2001, fifty-one neonates and infants <= 3 months presenting with heart failure, hypertension or both underwent UA (n = 16), FA (n = 26) and FVA (n = 9) balloon coarctation angioplasty. Immediate and follow-up results were evaluated. Acute reduction of peak-to-peak gradients across the coarctation (40 ± 17 mmHg vs. 5 ± 6 mmHg; p < 0.001), increase in diameter of the coarcted segment (2.2 ± 0.5 mm vs. 5.6 ± 0.8 mm; p < 0.001) and improvement in symptomatology occurred following BA. Surgical relief of aortic obstruction was required in 4 infants at 5, 21, 24 and 28 days after the procedure. Effective palliation was thus achieved in the remaining 47 infants (92%). During intermediate-term follow-up, twenty-two infants (50%) developed recoarctation requiring repeat balloon (n = 14) or surgical (n = 8) intervention 2–10 months (median, 3 months) after initial BA. The indication for reintervention was hypertension in all patients. At a median follow-up of 3 years (range, 0.5–5.5 years), blood pressures remained low (98 ± 11 mmHg) with an arm/leg blood pressure gradient of 4 ± 6 mmHg. Comparison of the groups revealed similar effectiveness both immediately and at follow-up. However, femoral artery complications were seen in only the FA group. Based on these data, we conclude that effective palliation is achieved with BA in all 3 groups, femoral artery complications are seen only in the FA group and BA is an excellent alternative to surgical intervention in the management of native AC in neonates and young infants.

Key words: aortic coarctation, balloon angioplasty, infants, neonates, transcatheter management

Treatment of native aortic coarctation (AC) by balloon angioplasty (BA) is a controversial issue,^1–6 but gradually the procedure is gaining acceptance in the management of children^7–12 with native coarctation. However, it remains controversial in neonates and young infants.^2,13,14 Because of the excellent results that we have been able to achieve with BA in neonatal and infant coarctations,^13,15–19 we have utilized this technique as a first-line therapeutic option to treat native coarctation in this subset of patients. In addition, we utilize transumbilical arterial^18,20 and anterograde²¹ approaches whenever possible to avoid femoral artery injury. We have reviewed our experience with BA of native coarctation in neonates and infants <= 3 months in an attempt to test our thesis that BA provides successful palliation, defined as non-requirement of surgical intervention for 4 weeks or longer, along with control of heart failure or the presenting symptoms. We also took this opportunity to compare and contrast immediate and follow-up results and complications of 3 different access routes via which the procedure was performed, namely, the transumbilical artery (UA), transfemoral artery (FA) and transfemoral venous anterograde (FVA) approaches.

Methods
Study subjects. During a 6.5-year period ending June 2001, fifty-one neonates and infants <= 3 months underwent BA of native coarctation at Cardinal Glennon Children’s Hospital and were the subjects of this study.

Inclusion/exclusion criteria. All symptomatic (congestive heart failure, hypertension or both) infants <= 3 months, irrespective of associated heart defects, were considered for BA. Discrete as well as long segment coarctation patients19 were included; however, if there was hypoplasia of the transverse aortic arch (n = 5), they were not considered to be suitable candidates for BA.

Balloon angioplasty technique. The BA technique that we have used has been described in detail in our prior publications.13,15,18,22–24 Here we reiterate some important technical aspects. 1) Balloon size: the diameter of the balloon selected for balloon dilatation was >= 2 times the size of the coarcted segment, but no larger than the diameter of the descending aorta at the level of the diaphragm. We initially select a balloon size equal to an average of the diameter of the isthmus or transverse aortic arch and descending aorta at the level of the diaphragm. If there was inadequate relief of obstruction (pressure gradient and angiographic improvement), a balloon as large as the descending aorta at the level of the diaphragm was used.²² 2) Balloon inflation: the pressure of balloon inflation was monitored and was not allowed to exceed balloon burst pressure as stated by the manufacturer, thus preventing inadvertent balloon rupture. 3) Heparin: heparin, 100 units/kg, was administered before introducing the balloon catheter and activated clotting times were monitored and kept between 200–250 seconds. 4) Balloon catheters: in UA cases, we initially used Proflex-5 catheters (Peripheral Systems Group, Mountain View, California);¹⁸ subsequently, we used Ultrathin and Diamond (Meditech, Watertown, Massachusetts) and most recently Tyshak-II catheters (Braun, Bethlehem, Pennsylvania). In FA and FVA cases, Ultrathin and Diamond catheters were initially used followed later by Tyshak-II catheters; the latter were introduced via 4 French (Fr) sheaths. In the last 2 cases of the FA group, Mini-Tyshak catheters introduced via 3 Fr sheaths were utilized. 5) Post-dilatation catheter manipulation: tips of the guidewires or catheters were not manipulated over the freshly dilated coarctation segment to avoid aortic perforation.²⁵

Data collection. The data acquired and analyzed were detailed in our previous publications^24,26 and will not be reviewed. Information collected included the timing and type of reintervention following angioplasty.

Statistical analysis. Data are expressed as means ± standard deviations for normally distributed variables. Medians and ranges are given for data that are not normally distributed. Comparisons of data prior to and following intervention were made by 2-tailed t-tests, while comparisons between groups were made by analysis of variance. Comparisons of data that were not normally distributed were made by appropriate non-parametric analogues.

Categorical values were compared by Chi-square or Fisher exact tests. A p-value < 0.05 was considered statistically significant. Bonferroni correction was made when multiple comparisons were undertaken.

Results
Study subjects. Fifty-one neonates and infants less than 3 months old underwent BA of native AC during a 6.5-year period ending June 2001. They were 1–90 days in age (mean age, 36–34 days). Twenty-six were neonates (<= 30 days) and 25 were infants between 1–3 months. Forty-one infants were in moderate to severe heart failure, twenty-nine were hypertensive (systolic blood pressure greater than 95th percentile for age) and 20 were found to have both. Seven neonates presented to the emergency room with symptoms of shock-like syndrome requiring endotracheal intubation and aggressive inotropic support, similar to that previously described.¹⁸ Five infants presented with severe left ventricular dysfunction, the so-called “hypertensive cardiomyopathy”, similar to a case that we previously reported.¹⁷ The data of 2 patients previously reported elsewhere19 are also included in this analysis. However, none of the other neonates and infants reported in our previous studies^{13,15–18,23,24,26–28} are included in this analysis.

Of the 18 neonates in whom transumbilical BA was attempted, the balloon catheter could not be negotiated via the umbilical artery in 2 neonates (11%) and the remaining 16 neonates constituted Group I. These 2 neonates, along with 24 other infants, underwent transfemoral artery BA; these 26 infants formed Group II. Nine infants had anterograde transvenous balloon dilatation and will be referred to as Group III. The age, weight and gender data are listed in Table 1 and associated cardiac defects are listed in Table 2.

Balloon angioplasty. Balloon dilatation was performed using 6 mm (n = 35), 7 mm (n = 12) or 8 mm (n = 4) diameter balloons, all 2 cm long. In Groups I and II, the balloon catheter was positioned across the coarcted aortic segment from the descending aorta. In the anterograde femoral venous patients (Group III), the catheter was advanced from the right ventricle through the ventricular septal defect into the aorta in 5 patients, directly from the single (double-inlet left) ventricle into the aorta in 1 patient and directly from the right ventricle into the neo-aorta in 3 post-Norwood, hypoplastic left heart syndrome patients. Balloon aortic valvuloplasty was performed concurrently in 2 infants, reducing aortic valve gradients significantly.

Immediate results. Significant reduction (p < 0.001) in peak-to-peak systolic pressure gradient (Figure 1) and increase in size of the coarcted segment occurred in the entire cohort as well as in all 3 groups (Table 3).

One patient (2%) in Group II had a residual gradient > 20 mmHg (reduced from 72–26 mmHg), but the infant had remarkable symptomatic improvement and therefore it was felt that no immediate reintervention was necessary. One neonate (2%) from Group I required surgical repair of coarctation 5 days after BA. At the same time, banding of the pulmonary artery was performed in this neonate with double-inlet left ventricle with L-transposition of the great arteries. Three infants (6%), two from Group II and 1 from Group III, rapidly developed recoarctation requiring surgical repair 3, 3.5 and 4 weeks after balloon angioplasty, respectively. The remaining infants improved symptomatically and did not require intervention within the first 4 weeks following BA. Thus, successful palliation, as defined above, was achieved in 47 of 51 infants (92%).

Complications. There was no mortality related to the procedure. Blood loss (during catheter/guidewire exchanges) requiring transfusion occurred in 5 of 51 patients (10%). Three (11.5%) were from Group II and 2 (11%) were from Group I (p < 0.1). None of the Group III patients had significant blood loss. Six of 51 (12%) had decreased femoral pulses with cool extremity, and all 6 were from Group II in whom femoral artery was used for BA. Warming of the contralateral extremity alone (in 4 infants) and/or additional administration of heparin (in 2 infants) improved the pulse and perfusion prior to discharge from the hospital. No aneurysms or dissections were seen. No other complications were encountered. Inability to position the balloon catheter across the coarctation site in 2 neonates in the UA cohort (Group I) has already been mentioned. Both neonates underwent successful transfemoral artery BA at the same sitting.

Follow-up. Follow-up data were available in all infants for >= 1 month. However, three infants were lost to follow-up after their 1-month visit. At that visit, no evidence for coarctation was present in these 3 infants. The remaining 44 infants were followed for 5 months to 5.5 years (median, 3 years).

Recurrence and its management. Recoarctation (peak gradient > 20 mmHg)^24,27 was observed in 22 of the 44 patients (50%). There was no clinical or echocardiographic evidence for recoarctation in the remaining patients. Recoarctation developed 2–10 months (median, 3 months) after BA. Surgical repair was undertaken in 8 infants without any complications. Repeat balloon angioplasty was performed in the remaining 14 infants. The diameter of the balloon used for repeat BA is generally larger by 1–3 mm (median, 2 mm) than that used at the time of initial BA. Following BA, the peak-to-peak gradients across the coarctation were reduced from 54 ± 20 mmHg to 9 ± 7 mmHg (p < 0.001). The indication for reintervention was hypertension and the procedures (both surgery and balloon) were performed electively and infants were otherwise asymptomatic. A second recurrence was observed in 3 children, two in the BA group and 1 in the surgical group. Surgical intervention in the 2 balloon recurrence patients and balloon angioplasty in the surgical recurrence patient were undertaken successfully.

Other procedures and events. During follow-up, a number of catheter interventional and surgical procedures were undertaken and include balloon aortic valvuloplasty (n = 3), blade atrial septostomy (n = 1), surgical resection of fixed subaortic stenosis (n = 4), bi-directional Glenn anastomosis (n = 4), repair of ventricular septal defect (n = 3), Ross procedure (n = 2), Damus-Kaye-Stansel (n = 1), mitral valve replacement (n = 1) and Fontan operation (n = 2). Also, three large ventricular septal defects closed spontaneously and 2 defects became very small so that surgery was not required. All 12 infants who presented with left ventricular dilatation and poor function gradually improved; the size and function of the left ventricle returned to normal 3–6 months following BA.

Complications during follow-up. Careful review of follow-up angiograms performed in 24 patients did not reveal aneurysms. Femoral artery blockage was observed in 4 patients, but there was good collateral circulation. No evidence for leg length discrepancy²⁹ was observed. There were no other complications.

Late follow-up. Long-term follow-up, defined as > 2 years, was available in 31 of 48 study subjects (65%). No late recurrences were detected. Arm-leg blood pressure gradients were 4 ± 6 mmHg (range, 0–15 mmHg). Right arm systolic blood pressures were 98 ± 11 mmHg (range, 82–114 mmHg). Four patients (8%) had systolic pressure greater than 95th percentile for age. Two children (4%) were receiving propranolol for control of blood pressure. None of the other children are on medication for treatment of aortic coarctation.

Group differences. The age of the UA patients (Group I) was lower (p < 0.001) than that of the other 2 groups (Table 1). Relief of obstruction as evaluated by gradient reduction was similar (Table 4). Effective palliation, as defined previously, was achieved to a similar degree in all 3 groups (Table 3). Femoral artery complications were present in only the FA (Group II) cohort, understandably so. The incidence of blood loss requiring transfusion was similar (p < 0.05) between Groups I and II (11% vs. 11.5%, respectively) and none in Group III.

Recoarctation rate was 71% in Group I, 50% in Group II and 12.5% in Group III. The recoarctation rate in Group I (10 of 14; 71%) appears higher than that seen in Group II (11 of 22; 50%), but this did not attain statistical significance (p > 0.05). This trend may be related to differences in age at angioplasty, 6 ± 3 days in Group I vs. 57 ± 32 days in Group II; p < 0.001). To test the effect of age on recurrence, the entire cohort was divided into neonates <= 30 days and infants 31–90 days. Recoarctation rate was higher (p < 0.001) in neonates (16 of 22; 73%) than in infants (6 of 22; 24%), thus attesting to the influence of age on recoarctation (Figure 2). Long-term follow-up data pertaining to blood pressure gradient and arm systolic blood pressure were similar between the 3 groups (Table 4).

Discussion
While the controversy in utilizing BA for native AC in children is seemingly resolved, there continues to be reluctance in using BA in the management of neonates and young infants with AC. Since our experience over the years is favorable,^{13,15–19,28} we have, at our institution, adopted a policy to apply BA as a first-line therapeutic option in the management of sick neonates and infants with AC. Similar experiences were also reported by other investigators.^30,31 The purpose of this study is to determine if effective palliation is indeed achieved. With the exception of 4 infants (8%) who required surgical relief of AC within 4 weeks of BA, effective palliation, as defined above, was achieved in the remaining infants (92%). However, reintervention either by surgery (n = 8) or by repeat BA (n = 14) was necessary in 22 infants (50%); such reintervention was undertaken electively when the infant was stable, mainly to treat systemic hypertension. The high incidence of recurrence that we observed in this group of patients is similar to that previously reported by us^24,28 and others.^14,30,31 However, as we have emphasized since our very first report on balloon angioplasty more than 15 years ago,¹⁵ “the important feature of balloon angioplasty in the neonate and young infant is that it produces abatement of symptoms of heart failure and hypertension and helps avoid immediate surgery. Should recurrence ensue, it can be treated by repeat balloon angioplasty or even surgery, if one prefers, when the infant is stable and less acutely ill.” Early failures can be effectively managed by surgical intervention. Late failures (recurrence) can be managed either by surgical intervention³² or repeat balloon angioplasty.³³

Failure to advance a balloon angioplasty catheter via the umbilical arteries to the coarctation site occurred in 2 of 16 patients (11%). This problem occurred in our early experience while we were using Proflex-5 and Meditech catheters and has not occurred since we began using highly trackable, low profile Tyshak-II catheters. Therefore, we use/recommend only the Tyshak catheters for transumbilical arterial balloon dilatation procedures.

Despite the younger age of Group I patients, the immediate relief of obstruction was similar in all groups, as was the recurrence rate. However, when recurrence in neonates (age <= 30 days) was compared to that in infants (ages 31–90 days), it was higher in neonates. These data indicate that the effect of age is more than the route of BA on recoarctation rate. The transumbilical artery and transvenous anterograde approaches, however, have the advantage over the transfemoral arterial route in that they are unlikely to have femoral arterial complications. Whenever feasible, transumbilical arterial and transvenous anterograde routes are, therefore, preferred.

While comparison of BA with surgical therapy is fraught with problems, detailed analyses of comparison published in several reviews^5,6,23,26,28 indicate that both modes of therapy are comparable in terms of effectiveness and safety. Balloon dilatation, however, has less morbidity and a lower complication rate.^5,28 Based on the current study and the review of comparative data, we conclude that BA has an important role in the management of sick neonates and infants with aortic coarctation and that BA is an effective and safe alternative to surgical therapy of native coarctation. BA is particularly useful in situations where avoidance of anesthesia and/or aortic cross-clamping is beneficial, such as infants presenting in shock-like syndrome,¹⁸ poor left ventricular function with “hypertensive cardiomyopathy” associated with coarctation,¹⁷ prior cerebrovascular accidents⁶ and severe liver dysfunction.⁶

Study limitations. This is a retrospective analysis of our experience and has the limitations of any retrospective study. Some variability of selection of patients and selection of mode of therapy, particularly for reintervention, exists and is related to bias of the primary cardiologist directing the therapy. However, since we have researched BA of native coarctation since mid-1980, a methodical process of data collection and patient selection has been incorporated into the continuing clinical practice and negates some of the limitations mentioned above. The inclusion of post-Norwood patients (n = 3 in Group II) may be critiqued, but because these coarctations are distal to the site of aortic arch reconstruction during the Norwood procedure, we felt justified in including these 3 patients as native coarctations.

Speculations/future directions. Although prompt relief of obstruction and effective palliation is achieved, some problems remain and include recoarctation and femoral artery compromise.

Causes of recoarctation. Causes of recoarctation following balloon angioplasty have been extensively investigated,^27,34,35 and factors predictive of recoarctation have been identified; these 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.³⁶ This may be related to cystic medial necrosis^37,38 or to extension of the ductal tissue into the aortic wall.^39–41 However, the fundamental cellular mechanisms responsible for recoarctation remain elusive.

Prevention of recoarctation. The 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 by stents is an attractive option.⁴² Unfortunately, the stents, which are metallic, do not grow with the child, and therefore could not routinely be used in neonates and infants. Biodegradable stents43 may offer a solution; the stents will keep the coarcted aortic segment open for a 3–6 month period, when the stents would dissolve. By that time, the ratio of the normal aortic tissue vs. abnormal tissue may be in favor of the infant, thus preventing recurrence of significant narrowing. However, testing this hypothesis in appropriate animal models and miniaturization of stent delivery systems such that they can be used in neonates and young infants should be undertaken in the future.

Femoral artery obstruction. Use of large-caliber angioplasty catheters resulted in significant femoral artery compromise.^44–46 Availability of balloon catheters that can be introduced through 4 Fr sheaths appears to reduce the femoral artery injury. More recent availability of balloon dilatation catheters that can be introduced through 3 Fr sheaths (for example, Mini-Tyshak catheters) may further reduce such complications. Detailed immediate and follow-up studies29 to confirm this thesis should also be organized in the future.

Summary and conclusions
Analysis of data on 51 consecutive BA procedures in neonates and infants <= 3 months at our institution revealed that effective palliation, defined as avoidance of surgery for 4 weeks or longer, along with improvement of presenting symptoms, was achieved in 92% of cases. Recurrence of coarctation was high, but was managed successfully by repeat BA in most cases and by surgery in others. Based on these data, it may be concluded that BA is an effective alternative to surgical intervention of native aortic coarctation in neonates and young infants.

Acknowledgment. The authors thank the members of the Divisions of Neonatology and Pediatric Cardiac Surgery at Saint Louis University School of Medicine/Cardinal Glennon Children’s Hospital, St. Louis, Missouri, for their contribution to the care of the patients in the study group including placement of umbilical artery catheters by the neonatologists. Thanks are also due to Kay Thompson for her assistance in preparing the manuscript.

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