Inadvertent QRS prolongation by an optimization device-based algorithm in patients with cardiac resynchronization therapy

Background Device-based algorithms offer the potential for automated optimization of cardiac resynchronization therapy (CRT), but the process for accepting them into clinical use is currently still ad-hoc, rather than based on pre-clinical and clinical testing of specific features of validity. We investigated how the QuickOpt-guided VV delay (VVD) programming performs against the clinical and engineering heuristic of QRS complex shortening by CRT. Methods A prospective, 2-center study enrolled 37 consecutive patients with CRT. QRS complex duration (QRSd) was assessed during intrinsic atrioventricular conduction, synchronous biventricular pacing, and biventricular pacing with QuickOpt-proposed VVD. The measurements were done manually by electronic calipers in signal-averaged and magnified 12-lead QRS complexes. Results Native QRSd was 174 +/- 22 ms. Biventricular pacing with empiric AVD and synchronous VVD resulted in QRSd 156 +/- 20 ms, a significant narrowing from the baseline QRSd by 17 +/- 27 ms, P = 0.0003. In 36 of 37 patients, the QuickOpt algorithm recommended left ventricular preexcitation with VVD of 42 +/- 18 ms (median 40 ms; interquartile range 30-55 ms, P < 0.00001). QRSd in biventricular pacing with QuickOpt-based VVD was significantly longer compared with synchronous biventricular pacing (168 +/- 25 ms vs. 156 +/- 20 ms; difference 12 +/- 11ms; P < 0.00001). This prolongation correlated with the absolute VVD value (R = 0.66, P < 0.00001). Conclusions QuickOpt algorithm systematically favours a left-preexcitation VVD which translates into a significant prolongation of the QRSd compared to synchronous biventricular pacing. There is no reason to believe that a manipulation that systematically widens QRSd should be considered to optimize physiology. Device-based CRT optimization algorithms should undergo systematic mechanistic pre-clinical evaluation in various scenarios before they are tested in large clinical studies.