Left ventricular endocardial pacing is less arrhythmogenic than conventional epicardial pacing when pacing in proximity to scar

Abstract

Background Epicardial pacing increases risk of ventricular tachycardia (VT) in patients with ischemic cardiomyopathy (ICM) when pacing in proximity to scar. Endocardial pacing may be less arrhythmogenic as it preserves the physiological sequences of activation and repolarization. Objective The purpose of this study was to determine the relative arrhythmogenic risk of endocardial compared to epicardial pacing, and the role of the transmural gradient of action potential duration (APD) and pacing location relative to scar on arrhythmogenic risk during endocardial pacing. Methods Computational models of ICM patients (n = 24) were used to simulate left ventricular (LV) epicardial and endocardial pacing 0.2–3.5 cm from a scar. Mechanisms were investigated in idealized models of the ventricular wall and scar. Simulations were run with/without a 20-ms transmural APD gradient in the physiological direction and with the gradient inverted. Dispersion of repolarization was computed as a surrogate of VT risk. Results Patient-specific models with a physiological APD gradient predict that endocardial pacing decreases VT risk (34%; P <.05) compared to epicardial pacing when pacing in proximity to scar (0.2 cm). Endocardial pacing location does not significantly affect VT risk, but epicardial pacing at 0.2 cm compared to 3.5 cm from scar increases it ( P <.05). Inverting the transmural APD gradient reverses this trend. Idealized models predict that propagation in the direction opposite to APD gradient decreases VT risk. Conclusion Endocardial pacing is less arrhythmogenic than epicardial pacing when pacing proximal to scar and is less susceptible to pacing location relative to scar. The physiological repolarization sequence during endocardial pacing mechanistically explains reduced VT risk compared to epicardial pacing.

Endocardial left ventricular pacing

“…In a canine LBBB model study, biventricular epicardial pacing, but not endocardial pacing, created a significant transmural dispersion of repolarization [ 16 ]. This is supported by a computational modeling study where the high repolarization gradients observed during epicardial pacing in close proximity to scar were not found during endocardial pacing [ 21 ]. How the observed effects on repolarization translate into risk of ventricular arrhythmia in clinical practice remains unclear; however, they suggest that endocardial LV pacing may be less arrhythmogenic than epicardial pacing, particularly in patients with ischemic cardiomyopathy.…”

“…Epicardial LV pacing reverses the physiological pattern of activation and repolarization within the myocardial wall, and has been demonstrated to increase the QT interval and transmural dispersion of repolarization in animal studies [ 19 , 20 ]. Increased local dispersion of repolarization has also been demonstrated during epicardial pacing in close proximity to scar in computational modeling studies [ 21 , 22 ]. However, while CRT-induced ventricular tachycardia has been reported [ 23 ], conventional CRT appears to have a significantly beneficial effect on the risk of ventricular arrhythmia, most likely due to the associated reverse LV remodeling.…”

Leadless left ventricular endocardial pacing in nonresponders to conventional cardiac resynchronization therapy

“…This may have also resulted in underrepresentation of ischemic patients who are generally regarded as more unwell than nonischemic patients as evidenced by only 45.5% of ischemic patients in this study, similar to the ALSYNC study that included 42.9% 8 . Ischemic patients have a greater potential to benefit from targeted endocardial pacing 14,16 . An accurate Simpson's biplane was not possible for all patients and a change in LVEF ≥5% was, therefore, used but it is appreciated that this is a less reliable estimate of outcome than reduction in LV systolic volume ≥15%.…”

“…8 Ischemic patients have a greater potential to benefit from targeted endocardial pacing. 14,16 An accurate Simpson's biplane was not possible for all patients and a change in LVEF ≥5% was, therefore, used but it is appreciated that this is a less reliable estimate of outcome than reduction in LV systolic volume ≥15%.…”

Leadless Left Ventricular Endocardial Pacing and Left Bundle Branch Area Pacing for Cardiac Resynchronisation Therapy

“…[ 6 – 9 ] Endocardial pacing is less arrhythmogenic than epicardial pacing and is less affected by myocardial scar location. [ 18 ] It is also less likely to result in phrenic nerve stimulation such as in epicardial pacing. The greatest potential benefit of endocardial pacing is the ability to pace anywhere inside the left ventricle, enabling the operator to select the optimal pacing site unrestricted by the coronary sinus anatomy.…”