Pediatric interventional cardiology was born 40 years ago in 1966, when William Rashkind developed balloon septostomy in neonates with transposition of the great arteries.1 Almost a decade later, Andreas Gruentzig developed coronary angioplasty (between 1972 and 1976), which heralded an explosive era of interventional therapy for adults with heart disease, overshadowing the advances in transcatheter therapy for congenital heart disease.2 However, in the last two decades, development of devices to close septal defects and extracardiac shunts, as well as techniques to open up stenosed valves and vessels, has revolutionized therapy for congenital heart disease. Transcatheter therapy has replaced open heart surgery for simple intra- and extra- cardiac lesions, but surgery still remains a necessity for many complex lesions. Interestingly, instead of developing as competing and conflicting specialties, cardiac surgeons and interventionists have been working together to develop hybrid techniques involving both modalities to improve overall outcomes in children with complex lesions. Recent advances in pediatric cardiology can be broadly subdivided into:
- device closures for septal defects and other vascular structures;
- balloon dilatation of valves, vessels and stenting of narrowed vessels, baffles, and conduits;
- percutaneous transcatheter valve implantation; and
- hybrid techniques involving transcatheter as well as surgical interventions.
Device Closure
The first attempt at device closure of atrial septal defect (ASD) was in 1976, by King and Miller, with limited success and popularity because of the cumbersome technique and use of very large delivery sheaths. In the modern era, the availability of devices with very low profile, ease of implantation, a very high success rate matching surgery with minimal morbidity has made ASD closure an ambulatory procedure, where the patient is discharged home within 24 hours.3 The Amplatzer Septal Occluder is the only device currently approved for ASD closure in the US, but other devices are being used in other countries.Ventricular septal defect (VSD) closure in the US is still not widely approved. The technique for VSD closure is more labor-intensive and requires more training and experience for successful outcomes than with ASDs.4 Both ASD and VSD closures are performed under transesophageal or intracardiac echocardiographic and fluoroscopic guidance. A combined interventional-surgical approach has been used in sick infants with apical muscular VSDs via the right ventricle through a median sternotomy, with improved outcome.5
These patients are poor surgical candidates because of the remoteness of the defect from the surgical field and difficulty in closing them. Closure of patent ductus arteriosus (PDA) has been performed successfully for over a decade using Gianturco coils, and now, with the availability of devices, even large PDAs can be closed easily as an ambulatory procedure with excellent success rates.6 Devices such as coils and detachable balloons have been variably used to occlude other vascular structures like aorto-pulmonary collaterals, arteriovenous malformations, coronary fistulae, Blalock Taussig shunts, and Fontan baffle fenestrations.7
Balloon Valvuloplasty and Angioplasty
Balloon dilatation of stenosed valves has been the procedure of choice for aortic pulmonary and mitral voice, except in very rare instances in neonates with diminutive left or right ventricles, and has excellent results. Use of a radio frequency ablation (RFA) catheter to open up an atretic pulmonary valve in pulmonary atresia with intact ventricular septum has also been very successful. Development of newer, low profile balloons has considerably reduced trauma to the femoral vessels. Angioplasty is also the procedure of choice in coarctation of aorta (beyond infancy) in many centers and for pulmonary artery stenosis (native or post-operative).The use of stents, when indicated, has improved immediate and long-term outcomes in both coarctation and branch pulmonary artery stenosis.
Transcatheter Valve Implantation
This is an exciting new development, with major experimental work being conducted in animal models and with limited experience in human subjects. Once perfected, this procedure may change the outlook for patients with failing valves who, until now, faced lifelong anticoagulation therapy after prosthetic valve implantation and may have had to undergo multiple open heart surgeries.8
Hybrid Techniques
Combined surgical and transcatheter techniques have been used in closure of VSDs, dilating and stenting branch pulmonary arteries in the operating room through an open chest, and as an alternative to the Norwood stage 1 procedure for hypoplastic left heart.9 In this procedure, as a first stage, the pulmonary arteries are banded to control pulmonary blood flow and the PDA is stented open to create a neo-aortic arch. The ASD may also be stented open if needed. As a second stage, bi-directional Glenn is performed via open heart surgery and as a third stage, again, a covered stent is used transcatheter to create a Fontan baffle and complete the cavo-pulmonary anastomosis. This reduces the number of exposures of the patient to cardio-pulmonary bypass; however, long-term follow-up and experience is needed before judging the outcome of this innovative procedure. Thus, despite a slow start, transcatheter interventional techniques have radically altered the outlook for children with congenital heart disease and close cooperation between surgeons and cardiologists has gone a long way in developing techniques to improve the morbidity and mortality rates in these young and often very sick patients.