Surgical and medical treatment of congenital heart disease has progressed remarkably over the past 50 years. Corrective surgery for many intracardiac defects began at Mayo Clinic and the University of Minnesota in the 1950s, with the introduction of the first cardiopulmonary bypass machines. Use of this technology allowed delicate intracardiac surgical procedures to be performed, even on small infants. Over the subsequent 5 decades, more complex surgical procedures have been performed in younger and smaller infants. Currently, even low-birth-weight neonates benefit from successful complex intracardiac procedures.
In the 1980s and 1990s, catheter-based techniques evolved so that many simple congenital cardiac lesions could be successfully addressed with intravascular procedures rather than through surgical incisions. This approach obviates the use of cardiopulmonary bypass with its inherent risks. Examples of these procedures include transcatheter device closure of:
In the 2000s, surgical and intravascular catheter techniques have been merged to perform procedures generically known as hybrid operations. Hybrid techniques have been applied to multiple congenital heart lesions. These lesions and procedures include:
"In the past 5 years at Mayo Clinic, the interventional congenital cardiac catheterization group has teamed with congenital cardiac surgeons to perform these procedures on a routine basis," according to Allison Cabalka, M.D., chief of pediatric cardiac catheterization at Mayo Clinic.
HLHS is a spectrum of disease related to hypoplasia or atresia of the left-sided cardiac structures. If untreated, this lesion is usually fatal within the first weeks of life. Neonates with HLHS have traditionally required either a Norwood operation or cardiac transplant.
Although improvements have been made to the Norwood operation, surgical management of HLHS remains challenging. Cardiac transplant in small infants is limited by donor organ availability. The Norwood operation entails reconstruction of the aortic outflow tract using the RV and PA for systemic perfusion. Flow to the PA is created through either a modified Blalock-Taussig shunt (systemic-to-PA connection) or a Sano shunt (RV-to-PA valveless conduit).
A hybrid procedure for patients with HLHS described in 2002 is gaining wider acceptance. (See Figure 1 for more information.)
During this procedure, the surgeon performs a pulmonary arteriotomy via a sternotomy. Cardiopulmonary bypass is not used and the heart beats throughout the procedure. An interventional cardiologist inserts a delivery sheath to deploy a stent through the arteriotomy in the ductus arteriosus to ensure long-term patency. (See Figure 2 for more information.)
In this manner, antegrade flow to the descending aorta and retrograde flow to the aortic arch and cerebral and coronary vessels can be maintained. To restrict pulmonary blood flow, a band is placed by the surgeon on each PA. (See Figure 3 for more information.)
"At Mayo Clinic, this hybrid approach is reserved for neonates with HLHS who are considered high risk for standard Norwood-Sano surgery," says Frank Cetta, M.D., chair of the Division of Pediatric Cardiology. Preterm infants or those judged to be unsuitable for a prolonged cardiopulmonary bypass are selected for the hybrid pathway.
Some institutions now use this approach more liberally for all patients with HLHS. Long-term data regarding outcomes of the HLHS hybrid procedure are limited. "Thus far, the hybrid approach is promising, especially because it obviates a long cardiopulmonary bypass run in a fragile neonate," says Dr. Cetta.
Cardiopulmonary bypass and cardiotomy were the standard methods for closure of muscular VSDs until the development of the percutaneous muscular VSD closure device. The device's effectiveness and the ease of use compared to direct surgical patch closure have prompted its use in the operating room. It offers an ideal approach for closure of moderate-sized muscular VSDs in early infancy when clinical heart failure is present.
Perventricular device closure is a hybrid of operative and catheterization techniques. It is accomplished with a limited sternal incision to expose the lower portion of the RV. (See Figure 4 for more information.)
The surgeon then punctures the RV to insert the delivery catheter. Cardiopulmonary bypass is avoided. Transesophageal echocardiography (TEE) clearly defines the VSD location and the size of the shunt. Midmuscular defects are ideal for this approach, but even more apical defects (below the moderator band) may be closed.
"Inlet VSDs, near the atrioventricular (AV) valves at the crux of the heart, generally cannot be closed with this technique because the device may interfere with AV valve function with resultant regurgitation," says Donald J. Hagler, M.D., an interventional pediatric cardiologist at Mayo Clinic.
The TEE operator assists the surgeon and interventional cardiologist by identifying a position on the anterior surface of the RV where a direct line to the muscular VSD is possible. The RV anterior surface is punctured by the surgeon, and the cardiologist works a smooth guide wire through the defect and into the LV. The delivery sheath can then be advanced over the guide wire to thread the sheath through the VSD and into the LV.
Based on the 2-dimensional echocardiographic defect size, a muscular VSD occluder is selected that has a waist diameter approximately 2 mm larger than this measurement. "The TEE guides placement of the device so that the distal disk is delivered in the LV cavity away from the mitral apparatus," says Dr. Hagler. "TEE is used to determine appropriate positioning of the device disks and to ensure that there is no interference with AV valve or ventricular function." (See Figure 5 for more information.)
Patients with complex RV outflow tract stenosis frequently require transcatheter placement of stents in the branch pulmonary arteries. These procedures may have a long duration of radiation exposure and become technically quite complex, especially when catheters are required to navigate multiple turns.
The advantage of hybrid placement of stents is that it is performed with direct visualization by the surgeon during pulmonary valve replacement or RV outflow tract reconstruction with the assisting interventional cardiologist participating in the stent deployment.
The experience at Mayo Clinic with intraoperative PA stent placement has demonstrated safety and efficacy. Proper sizing of the PA stent is determined by a preoperative angiogram. The surgeon usually places a stitch on the proximal stent to prevent distal migration. (See Figure 6 for more information.)
This technique successfully relieves branch PA stenosis while saving the patient from excess radiation exposure.
"In the 1960s and 1970s, patients born with transposition of the great arteries underwent Senning and Mustard operations to reroute blood flow at the atrial level to relieve cyanosis," according to Harold M. Burkhart, M.D., a cardiovascular surgeon at Mayo Clinic. "Most of these patients have reached adulthood, but there are consequences of these surgical techniques that have resulted in long-term residual problems."
One issue is progressive pulmonary venous baffle obstruction. (See Figure 7 for more information.)
These obstructions may be addressed in the catheterization laboratory with stent placement, but the procedures are lengthy and require multiple 180° turns of catheter systems that are prone to kinking, with unsatisfactory results.
Similar to the perventricular muscular VSD technique described above, the surgeon begins the hybrid procedure to relieve pulmonary venous baffle obstruction by making a small atriotomy via a minimal anterior thoracotomy. Cardiopulmonary bypass is not used, and the heart beats throughout the procedure. TEE guidance is used to pass an exchange wire from the native right atrium (pulmonary venous atrium) through the pulmonary venous pathway into the superior portion of the native left atrium. A stent is deployed with TEE guidance. (See Figure 8 for more information.)
Patients are typically discharged from the hospital within 48 hours after successful hybrid stent placement for pulmonary venous baffle obstruction.
Great advances in surgical and catheter-based techniques for patients with congenital heart disease have merged into hybrid procedures. These procedures have expanded the therapeutic options for patients with various forms of congenital heart disease. Hybrid procedures have reduced the number and duration of interventions for these patients.
Many hybrid procedures are performed with the heart beating, eliminating the need for cardiopulmonary bypass. The future holds great promise for expansion of collaboration between heart surgeons and interventional cardiologists in the treatment of patients with congenital disorders.