Interventional Cardiac Catheterization in Children
Charles Baker, M.D.
Catheterization has been a routine part of treatment of patients with congenital heart disease for the past 30 years. Initially it was used as a diagnostic modality. More recently (since the early 1980's) "interventional" catheterization has become increasingly important and more common. "Interventional" catheterization includes performance of a corrective or therapeutic procedure during the catheterization either complementing surgical therapy or treating a congenital or acquired defect without surgery.
The majority of cardiac catheterizations performed in children are now performed solely for correction or treatment of a defect, or include an interventional procedure during a diagnostic catheterization.
When cardiac defects are diagnosed and meet criteria for intervention (these criteria vary over time and from defect to defect) the treatment plan must be defined. This plan may include diagnostic or therapeutic (interventional) catheterization. What follows is a summary of the congenital and acquired heart defects that currently can be treated via interventional catheterization.
Native Defects Treated via Catheterization
Valvar Pulmonary Stenosis (PS)
Valvar Aortic Stenosis (AS)
Pulmonary Artery Stenosis
Coarctation of the Aorta
Patent Ductus Arteriosus (PDA)
Atrial Septal Defect (ASD)
Patent Foramen Ovale (PFO)
Ventricular Septal Defect (VSD)
Arterio-venous Fistulae
Coronary Artery Fistulae
Wolff-Parkinson White (WPW) or other accessory electrical connections that can cause SVT
Acquired/Postoperative Defects Treated via Catheterization
Pulmonary Artery Stenosis
Residual/Recurrent Pulmonary Stenosis
Residual/Recurrent Valvar Aortic Stenosis
Residual/Recurrent Coarctation of the Aorta
Residual Ventricular Septal Defect
Fontan Fenestration (surgically created defect for right to left shunt)
Systemic Venous Obstruction
General Methods of Intervention
Balloon Valvuloplasty
Balloon valvuloplasty was the first reported in pediatrics in the early 1980s. Patients who have isolated valvar aortic (AS) or pulmonary stenosis (PS) will likely be appropriate candidates for balloon valvuloplasty. Patients may present at birth with "critical" aortic or pulmonary stenosis requiring immediate ICU care and prostaglandin administration, or may present as a child outside of the newborn period.
The general technique involves placement of a balloon catheter across the affected valve. The pulmonary and aortic valves are most commonly affected although rheumatic mitral stenosis is also treated this way in countries with endemic rheumatic fever. The balloons are introduced through the femoral artery, femoral vein, or internal jugular vein and are positioned across the valves using guide wires. The balloon is inflated, deflated, and then removed. The hemodynamic and angiographic evaluation is then repeated and the need for further therapy is assessed.
The results are excellent with about 90% success rate for pulmonary stenosis and about 80-85% immediate success for aortic stenosis. Conscious sedation is used for most while general anesthesia is applied in critically ill or high-risk patients. Outside of the neonatal period balloon valvuloplasty is usually accomplished as an outpatient procedure and is associated with rapid recovery.
Balloon Angioplasty
Balloon angioplasty can be used to treat native or recurrent coarctation of the aorta, native or postoperative peripheral pulmonary artery stenosis, or more rarely acquired systemic venous obstruction [i.e. superior vena cava obstruction following extra corporeal membrane oxygenation (ECMO) therapy].
The general technique is similar to valvuloplasty and involves placement of a balloon catheter across the narrow portion of the affected blood vessel. The balloons are introduced through the femoral artery, femoral vein, or internal jugular vein and are positioned across the narrowed vessel using guide wires. The balloon is inflated, deflated, and then removed. The hemodynamic and angiographic evaluation is then repeated and the need for further therapy is assessed.
The rate of success for recurrent or residual obstructions is the highest, although the long-term success rates in native lesions can be quite variable. Even when a long-term cure is not achieved during the catheterization, the procedure can benefit the patient greatly by allowing definitive therapy (either surgical or trans-catheter) to be delayed until the patient has grown significantly or is more medically stable.
Intravascular Stent Placement
Stents are tubular, metallic, balloon expandable devices that can be delivered using techniques similar to balloon angioplasty, however the stent remains within the vascular space providing a more rigid framework to expand the affected vessel. The stents used in pediatrics are designed for use in the bile ducts and peripheral arteries of adults and are similar to but larger than the stents used to treat adult coronary artery disease.
When used in conjunction with balloon angioplasty to treat peripheral pulmonary artery stenosis, coarctation of the aorta and rarely systemic venous obstruction stent use has been associated with improved short-term and long-term rates of success compared to balloon angioplasty alone. Stent use in pediatrics has less follow-up data than balloon valvuloplasty and the true long-term results have yet to be defined, however the short and midterm results would suggest that stent placement is an important and successful adjunct to current therapy. Balloon angioplasty and stent placement have been uniquely useful in treating stenoses, such as distal branch pulmonary artery stenosis, not approachable by surgical techniques.
Most patients with newly placed or dilated stents will spend a single night in the hospital for close monitoring and empiric anticoagulation.
Embolization Coil Placement
Stainless steel or platinum coils (most dacron covered) can be used to occlude a variety of unwanted blood vessels or structures. PDAs, coronary artery fistulae, pulmonary arterio-venous fistulae, and a variety of undesirable collateral blood vessels that are usually found in patients with complex heart disease, can all be effectively treated using coils or one of the many modified coils available on the market.
The technique involves identification and measurement by angiography of the structure to be closed or occluded. A catheter, usually quite small in caliber (4-5 french), is then threaded into the structure and the coil is then delivered through the catheter. The size of the structure to be occluded determines the choice of coils, which are available in multiple loop diameters and lengths. The angiograms and hemodynamics are then repeated and the need for further intervention is assessed.
When used in stable patients during an uncomplicated catheterization, the procedure is usually performed as an outpatient.
Septal Occluder Placement
Atrial septal defects (ASD), patent foramen ovale (PFO), and ventricular septal defects (VSD) can all be closed non-surgically using trans-catheter techniques. The FDA approved the Amplatzer Septal Occluder in November 2001 for closure of uncomplicated ASDs. The CardioSEAL device as well as the Amplatzer PFO device have a limited approval from the FDA under humanitarian device exemption (HDE) guidelines to close PFOs. The CardioSEAL device also has HDE approval to close muscular VSDs or residual VSDs. The anatomy of the ASD or VSD determine whether the patient is good candidate for trans-catheter closure. Some ASDs will still require surgical closure and surgery remains an option for all patients with an uncomplicated ASD.
The techniques used are similar to above but generally involve larger introducing sheaths and catheters. This limits the use of these devices to patients out of the newborn age range and usually greater than 3 years of age. Transesophageal echocardiography is utilized to continuously guide device placement, and for this reason most cases are completed with general anesthesia. After placement of a septal occluder, an overnight inpatient stay is currently required to allow assessment of the device position and effectiveness by echocardiography the morning following the procedure.
Radio Frequency Catheter Ablation
Patients with reciprocating supraventricular tachycardia (most common form of SVT) or with WPW are candidates a trans-catheter curative procedure. Catheters tipped with electrodes are introduced through the femoral veins and are used to identify the unwanted accessory connections that cause SVT. Once identified these "pathways" can be eliminated using radio frequency energy (heat) applied through the same types of catheters used to identify the short circuits (accessory pathways).
This procedure has a greater than 90% success rate and is nearly always curative when used in patients with accessory pathway mediated SVT. The procedure is done as an outpatient and is accompanied by a rapid recovery.
*The information above was meant as a brief overview of pediatric interventional catheterization. Indications, patient selection criteria, detailed results and potential complications were not discussed in detail and are beyond the scope of this document.
Below is a list of helpful website links and references for 2 review articles.
http://www.pediheart.org/parents/defects/
http://www.amplatzer.com/physicians/ http://216.185.112.5/presenter.jhtml?identifier=158
(American Heart Association site)
References:
1) Pediatr Clin North Am 1999 Apr;46(2):441-64
Interventional Cardiac Catheterization.
Pihkala J, Nykanen D, Freedom RM, Benson LN.
2) J Pediatr 1998 Sep;133(3):324-33
Inroads in transcatheter therapy for congenital heart disease.
Mendelsohn AM, Shim D.