Perventricular Approach to Pulmonary Valve Placement: Geometric Remodeling of the Outflow Tract
With an increasing number of adult patients diagnosed with congenital heart disease (CHD), novel treatment strategies are required using a multi-disciplinary team. The following Expert Analysis article describes the use of a heart team consisting of congenital heart surgeon, interventional cardiologist, pediatric cardiac anesthesiologists, noninvasive cardiologists and specialized nursing teams to place a pulmonary valve in the native outflow tract using a hybrid transcatheter approach.
Presently, there are over 100,000 patients with tetralogy of Fallot (TOF) alive in the U.S. with a majority of patients having some degree of pulmonary regurgitation. Indications for requiring pulmonary valve replacement are continually being redefined as more is understood about right ventricular failure as a result of chronic volume load from the pulmonary regurgitation. It was once believed that a patient with repaired TOF would not need another operation. Congenital heart specialists began realizing that a portion of these patients would require placement of a pulmonary valve in order to prevent the negative effects of chronic regurgitation of blood into the right ventricle, and symptom-free survival.1 The chronic regurgitation is caused by resecting the abnormal pulmonary valve and, in most cases, placing a patch to increase the size of the right ventricular outflow tract (RVOT patch). Congenital heart specialists are now finding that much greater numbers of patients with repaired TOF and significant pulmonary insufficiency will benefit from placement of a competent valve.2,3,4,5
There are two primary approaches to placement of a pulmonary valve. The “gold standard” is surgical replacement of the valve. The main benefits of this approach are that the valve can be placed with very little morbidity and mortality but requires open-heart surgery and being placed on cardiopulmonary bypass. Other medical issues can also be addressed, such as pulmonary artery stenosis, arrhythmia ablations, and closure of residual shunts. Recently there has been the development of percutaneous valve replacement, with the benefit of not requiring open-heart surgery, and overall decreased impact to the patient.6 Patients can return home the next day; they do not have to have a “redo” surgery. This approach is only for patients with previous conduit placement during their repair, approximately 15% of all TOF patients. Also during this approach other issues cannot be addressed.
Combining the benefits of both procedures is the “hybrid” approach that the authors of this article are using for patients with CHD. For us a “Hybrid thought process” is an overall arching tenant for concurrent management of our patients with CHD by multidisciplinary members, combining the expertise of the interventional congenital cardiologist, the noninvasive cardiologist, the anesthesiologist, the perfusionist, other allied medical professionals and a congenital heart surgeon (Figure 2).
We can develop a novel “hybrid” approach to place a pulmonary valve. In order to be able to place a pulmonary valve via a perventricular approach (placing a large sheath via the apex of the right ventricle), we develop a three-dimensional (3-D) model, as shown in Figures 3a, b, and c. With the 3-D, model, physicians can determine the exact catheter positions and stent needs to build an appropriate landing zone for a stented valve that is placed through the sheath in the right ventricular apex.
In order to make this “hybrid” approach a more feasible option for all patients, better delivery sheaths that will be steerable and can be easily anchored in the right ventricle need to be developed. We are in the process of developing such sheathes and will want to develop an animal model to test these principles. The best 3-D models produced have some compliance and show both systole and diastole. These models are best produced with CT scans. Most patients, though, undergo magnetic resonance imaging (MRI). Health care professionals need to develop a process that can take the MRI data and make better more realistic models.
An animal model can be used to obtain cardiac MRIs with functional sequences from which more realistic 3-D models can be made to develop customized stenting to reduce the right ventricular outflow to allow for stented valve placement. We can then use customized sheaths to deploy the stents and the stented valve. This will allow us to develop a reproducible process and ability to teach others the technique, expanding the role of the “hybrid” valve placement.
- Shimazaki Y, Blackstone EH, Kirklin JW. The natural history of isolated congenital pulmonary valve incompetence: surgical implications. Thorac Cardiovasc Surg 1984;32:257–59.
- Therrien J, Provost Y, Merchant N, Williams W, Colman J, Webb G. Optimal timing for pulmonary valve replacement in adults after tetralogy of fallot repair. Am J Cardiol 2005;95:779-82.
- Geva T. Indications and timing of pulmonary valve replacement after tetralogy of fallot repair. Semin Thorac Cardiovasc Surg Pediatr Card Surg Ann 2006:11-22.
- Lee C, Kim YM, Lee C, et al. Outcomes of pulmonary valve replacement in 170 patients with chronic pulmonary regurgitation after relief of right ventricular outflow tract obstruction implications for optimal timing of pulmonary valve replacement. J Am Coll Cardiol 2012;60:1005-14.
- Geva T. Indications for pulmonary valve replacement in repaired tetralogy of fallot: the quest continues. Circulation 2013;128:1855-7.
- Zahn E, Hellenbrand W, Lock J, McElhimmey D. Implantation of the melody transcatheter pulmonary valve in patients with a dysfunctional right ventricular outflow tract conduit: early results from the U.S. clinical trial. J Am Coll Cardiol 2009;54:1722–9.
< Back to Listings