Percutaneous pulmonary valve implantation in India: Quo Vadis?

Surgical treatment of tetralogy of Fallot (TOF) represents the triumph of modern medicine. Long-term follow-up data, in general, have shown excellent survival and quality of life, but the survival is less than that of the general population as heart failure and sudden death may occur in some of these patients. An annual mortality of 0.24%–0.5% in the initial 20 years, and nearly 1% beyond 25 years have been observed in the long-term follow-up studies. [1-4] Mortality in a favorable subset of TOF may even be equal to that of the general population. In others, progressive right ventricular outflow tract (RVOT) stenosis and/or pulmonary regurgitation, worsening ventricular function, and arrhythmias may pose problems. In a multicenter study of postoperative adult patients followed up for 10 years, 2% incidence of sudden cardiac death, 1% heart failure, and 5% incidence of ventricular tachycardia (VT) or atrial flutter/fibrillation were found. [5] These and other data have convincingly shown that late age at initial operation, dysfunctional RVOT (severe regurgitation or stenosis), ventricular dysfunction (right [RV] as well as left ventricle[LV]), wide QRS complex (>180 ms), and presence of arrhythmias increase the risks of adverse events on follow-up in these patients. [1-6] The RVOT obstruction and/or pulmonary regurgitation tend to progress with time and need to be tackled before the ventricle is irreversibly damaged. Based on this paradigm, several guidelines have suggested the appropriate time to intervene relying on ventricular volumes, ejection fraction, QRS duration, and presence of arrhythmias even in asymptomatic patients. [7-10] In patients with RVOT gradient >64 mm Hg (or >80 mm Hg), RV systolic pressure >2/3 systemic pressure, or moderate-to-severe pulmonary regurgitation (regurgitation fraction >25% or more), pulmonary valve replacement (PVR) is indicated if the patient has symptoms due to these, or is asymptomatic but has one or more indicators of RV dysfunction namely RV end diastolic volume (RVEDV) >140–160 ml/m2, RV end systolic volume (RVESV) >80 ml/m2, (RVESV more important than RVEDV), progressive decline in RV ejection fraction, or RV ejection fraction <47%, QRS duration >180 ms, sustained atrial or ventricular arrhythmia, or exercise intolerance (<60% maximal oxygen consumption). Others have recommended PVR in patients with RV/LV EDV >2 or LV ejection fraction <55% or in patients requiring open heart surgery for other reasons with less stringent criteria. [11,12] Following PVR, symptomatic improvement, improved exercise performance, reduction in RV volumes, and in QRS duration is reported in some, but not in all studies. [13,14] However, there may be no change in QRS duration if it was >160 ms preoperatively. [15] Reversion of RV volumes to preoperative status during follow-up has been reported in some studies. [16] It may be that we are performing PVR too late, or alternatively we are chasing the wrong targets in trying to improve the long-term outcomes. [17] It may be too simplistic to think that complex question of sudden death may be predicted by one QRS duration, or the ventricular remodeling that has numerous variables in an individual patient can be predicted by any particular ventricular volumes. In fact, hard endpoints of death have not been shown to be altered by PVR. [18-20] In a more recent multicentric cohort follow-up, the RV volumes did not even correlate with adverse events, but RV mass/volume ratio, and LV ejection fraction were important correlates of VT and sudden cardiac death. [6] Thus, a refinement of our tools to identify the predictors of sudden cardiac death and heart failure in postoperative TOF patients are needed. Whether myocardial fibrosis on cardiac magnetic resonance imaging, mass/volume ratio, or other indicators such as global ventricular function index on echocardiography, or any biomarker may yield better results remains to be investigated. [21,22]