Fifteeen Years of Cardiac Resynchronization Pacing for Heart Failure Among Congenital Heart Patients: Direct Contractility not Guidelines Determines Responders

Abstract

Many patients (pts) with congenital heart disease (CHD) will be listed for heart transplant (HT) for refractory heart failure (HF) (NYHA class 3-4). However success is not assured. Cardiac resynchronization pacing therapy (CRT) has been applied to improve HF in adults with normal cardiac anatomy and without pacemakers. However, based on published guidelines for CRT implant (<35% ejection fraction (EF), QRS >120ms, QRS with left bundle branch block (BBB)), “responder” (R) success is still equivocal with “success” often defined as only a 5-10% EF improvement. Unfortunately, these guidelines do not apply to CHD pts with post repair right BBB QRS, pacemakers and when EF measurement is often inaccurate due to anatomy. In effect, there are no CRT selection guidelines for CHD pts. The purpose of this study was to evaluate efficacy of pre-implant direct contractility screening to determine CRT response among CHD pts with refractory HF to delay HT. From 1999-2014, 103 CHD pts were considered for HT (NYHA 3-4). During HT listing evaluation, 37 of these (mean age 22y) agreed to additional cardiac catheterization (Cath) studies with temporary biventricular (Bi-V) paced hemodynamics, including V contractility indices (dP/dt, dP/dt/p) to determine any acute CRT benefit, defined as a ≥15% increase in dP/dt indices over baseline. CHD included tetralogy of Fallot, transposition of great arteries (Mustard), single V (Fontan), and septal defects. Based on the acute evaluation, pts either did or did not receive CRT and all have been followed up to 144 months (mean 38) after initial CRT evaluation. Of 37 pts, 26 (79%) had preexisting V pacemakers. An accurate EF (mean 31%) could be measured in only 24 (65%). None had left BBB. A positive acute CRT response (mean dP/dt 586 vs 828mm Hg-sec, p<0.006) was found in 25 (68%) and these pts received CRT implant without complications. There were no differences (p=NS) between R vs non-R pts in age, baseline dP/dt, EF, QRS duration, V pressures or pre-existing pacemakers. During follow-up, all R pts improved in NYHA class with less HF symptoms. Repeat Cath 6-24m later, showed stable normal contractility (dP/dt 828 vs 948mmHg-sec (p=NS)). Of these 25 R-pts, 4 underwent eventual HT (mean 56 mos later), 4 died (2 medical noncompliance (MNC)) and 17 remain clinically stable off the transplant list (NHYA class 1-3), 2-108 mos (mean 36) later. Of the 12 non-R pts with a negative acute CRT response (mean dP/dt 635 vs 662mm Hg-sec, p=NS), 2 received HT within 24 mos of listing, 3 died awaiting HT (2 MNC), and 7 remain on the HT list (NYHA 3-4), 2-36 mos (mean 12) later. Pt response to CRT is often equivocal. CHD pts are unique with diverse cardiac morphologies that are not included in published selection criteria guidelines. Pre-selecting individual CHD pts with HF for CRT pacing by directly measuring contractility beforehand assures greater responder efficacy, can delay need for HT and can improve pt well-being.