Special Feature
Cardiac Catheterization in Pediatrics
By Alan Friedman, MD, FAAP
Innovative procedures, along with the development of novel intracardiac and intravascular devices, have led to dramatic improvements in the care of patients with congenital heart disease. No discussion of interventional pediatric cardiology can begin without recognizing its pioneer, William Rashkind, MD, of Philadelphia. Since he performed the first balloon atrial septostomy, interventional cardiac catheterization has served as a paradigm for the collaborative working relationship of the pediatric cardiologist and the cardiothoracic surgeon. Pediatric Cardiology is a symposium on interventional cardiology that outlines and reviews the non-surgical techniques and devices that are used to treat children with heart disease.1 In today's cardiac catheterization laboratory, the pediatric cardiologist can create shunts, open stenotic valves, relieve vascular obstruction, and close shunting defects, often with low-risk, outpatient procedures.
Creating an Atrial Shunt: Balloon Atrial Septostomy
In 1966, Raskind and Miller described a technique to create an atrial septal defect to palliate patients born with Transposition of the Great Arteries.2 A specially designed balloon catheter is inserted into either the umbilical or femoral vein, up the inferior vena cava into the right atrium, across the foramen ovale and into the left atrium. Once there, the balloon is inflated and then briskly pulled back into the right atrium and then deflated. As the inflated balloon traverses the atrial septum, it creates an atrial septal defect, allowing oxygenated blood to enter the right heart and transposed aorta. The clinical results are dramatic as the patient's oxygen saturation often climbs by 20% or more into the 70-80% range-allowing these critically ill neonates to be stabilized and survive until a definitive surgical therapy can be undertaken. This procedure alone is undoubtedly responsible for the survival of thousands of children throughout the last 35 years. In addition, this procedure may be used for other congenital heart diseases that may be complicated by atrial outlet obstruction (i.e., Tricuspid Atresia and the Hypoplastic Left Heart Syndrome).
Relieving Stenosis: Balloon Valvuloplasty, Angioplasty, and Stent Implantation
In 1982, Kan and associates reported the successful percutaneous technique for treating pulmonary valve stenosis.3 Since then, this technique has changed little, and its general principle has been applied to the stenotic aortic and mitral valve as well. After angiography to assess the annular or vascular dimensions, specialized balloon catheters are passed over a wire until the balloon is appropriately positioned across the stenotic valve. The balloon is then inflated to dilate the often partially fused valve leaflets. This procedure is safe, effective, and the standard-of-care for the patient with significant pulmonary valve stenosis. Long-term results have shown that at least 75% of patients are left with either no or only mild residual stenosis and require no subsequent procedures. In many centers, balloon valvuloplasty is also the first-line therapy for significant aortic stenosis. Similarly, balloon angioplasty has become standard therapy for the management of pulmonary artery stenosis, which can be particularly difficult for the surgeon to reach as these lesions often extend beyond the hilum of the lung.
Pulmonary artery stenosis is commonly seen in patients with tetralogy of Fallot, pulmonary atresia, and truncus arteriosus. While most centers continue to surgically treat neonatal aortic coarctation, many interventional cardiologists successfully treat the child, adolescent, and adult patient with native aortic coarctation or recurrent coarctation with balloon angioplasty. Most recently, implantable, metallic stents have been used to treat both pulmonary artery stenosis and aortic coarctation in the older pediatric patient. These stents are delivered over a balloon catheter that, when inflated, expands the stent to the desired diameter. Stents have the advantage of providing rigid support to the vessel wall that otherwise might re-stenose. In addition, the interventionalist can return later to further dilate some stents to "keep-up" with vessel growth. A recent report has demonstrated that intravascular stents for the treatment of vascular stenoses provide excellent immediate and long-term results.4
Closing Shunting Defects: Septal Occlusion Devices and Intravascular Coils
The last 15 years have witnessed tremendous advances in the non-surgical closure of shunting lesions. Interventionalists have developed and deployed devices to occlude atrial septal defects and the patent ductus arteriosus. Currently, there are a number of studies investigating novel devices to close secundum atrial septal defects.
These devices are placed from specialized delivery sheaths and catheters across the atrial septal defect. The distal (left atrial) aspect of the device is then deployed and anchored on the septum. Often, with the assistance of transesophageal echocardiographic guidance, the proximal aspect (right atrial) is then deployed, and the device is released. Results of these outpatient procedures appear encouraging.
Perhaps the most common transcatheter intervention is the coil occlusion of the patent ductus arteriosus. Having been performed in thousands of patients, this procedure involves the placement of a metal coil with dacron fibers across the ductus, such that the coil straddles the ductus, and its filaments obstruct flow across it. The procedure can safely and quickly be performed in infants, children, and adults with excellent results. Large studies have reported complete closure in 90-95% of patients at follow-up. Patients are usually discharged 4-8 hours after the procedure, saving valuable inpatient resources.
In summary, numerous advances in transcatheter intervention have been made in recent years. These procedures have decreased the need for thoracotomy, as well as both closed and open heart surgical procedures with their attendant morbidity and mortality. Many of these interventions can be performed on an outpatient basis, which will help contain medical costs, shorten recovery time, and improve the quality of life for the patient with congenital heart disease.
References
1. Pediatric Cardiology 1998;19:1-93.
2. Rashkind WJ, Miller WW. Creation of an atrial septal defect without thoracotomy: A palliative approach to complete transposition of the great arteries. JAMA 1966;196:991-992.
3. Kan JS, Percutaneous balloon valvuloplasty: A new method for treating congenital pulmonary valve stenosis. N Engl J Med 1982;307:540-542.
4. Shaffer, Intravascular stents in congenital heart disease: Short- and long-term results from a large single center experience. J Am Coll Cardiol 1998;31:661-667.
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