When limited by cost in CRT-be a leftist!

Cardiac resynchronization therapy (CRT) over last two decades has transformed the management expectations of diligently selected patients with systolic heart failure. While the true inception of the idea dates back to 1925 when Wiggers showed that surface stimulation of the caninemyocardium reduced themaximal LV pressure derivative (LV dP/dtmax) and lengthened isometric contraction, the observation in the 1980s by Grines et al. that LBBB reduces diastolic filling time and the septal contribution to LV ejection was sentinel to further developments. By 1990s a link emerged between electrical dyssynchrony and LV function and in 1987, Mower devised and was granted a patent for the concept of “biventricular pacing,” explicitly aimed at heart failure (HF) treatment [2]. However, the Achilles' heel for widespread benefit of this notion of biventricular (BiV) pacing remained the overall 30% nonresponders and prohibitive cost in countries with no insurance backups for the masses. The latter has been a key issue in developing countries like India. The concept of LV (only) pacing emerged over last decade, has found some doubtful utility in non-responders to biventricular pacing and has been proven to be equal or non inferior to biventricular pacing in some studies. This led ESC guidelines to include it as an alternate to biventricular pacing in 2013 [3]. The algorithms like RV sense triggered LV pacing further pushed these developments. Theoretically, LV mode may have some advantages over the BiV mode including increased longevity of the device and hence decreased cumulative costs. At times if the RV lead performance is compromised, a repeat surgery can be avoided by switching to changing the pacing mode from BiV to LV only [4]. But the cost reduction would be attended in real sense only when reasonably sufficient evidence arises for customizing an A-V Sequential/dual chamber pacing to deliver RA sense and LV only pacing. Another reason in favor of LV-only pacing regards specific categories of patients (patients with indication for CRT and frequent hospitalizations for HF, not requiring implantable cardioverter defribrillator back-up) in whom atrial-synchronous LV-only pacing can be achieved with cheaper solutions (i.e. a coronary sinus lead connected to a conventional DDD device) [5,8]. The present issue of this journal presents interesting data on application of customized dual chamber or VDD pacing to deliver optimized LV only pacing with electrical and mechanical fusion with intrinsic QRS [1]. However, AV conduction is variable is largely unpredictable due to circadian cycle, autonomic tone and drug therapy. Pacing algorithms like dynamic sense AV delays or negative AV hysteresis traditionally in CRT devices may prove helpful