The Lead Podcast - Episode 89: A Discussion of Vasovagal Responses to Human Monomorphic Ventricular Tachycardia...

Dr. Jason T. Jacobson, MD, FHRS, Westchester Medical Center, New York Medical College is joined by Melissa Robinson, MD, FHRS, Providence Heart Institute of Montana, and Dr. Sei Iwai, MD, FHRS, Westchester Medical Center, New York Medical College to discuss: BACKGROUND Factors determining hemodynamic stability during human ventricular tachycardia (VT) are incompletely understood. OBJECTIVES This study aimed to characterize sinus rate (SR) responses during monomorphic VT in association with hemodynamic stability and prospectively assess the effects of vagolytic therapy on VT tolerance. METHODS This is a retrospective analysis of patients undergoing scar-related VT ablation. Vasovagal responses were evaluated by analyzing sinus cycle length before VT induction and during VT. SR responses were classified into 3 groups: increasing ($5 beats/min, sympathetic), decreasing ($5 beats/min, vagal), and unchanged, with the latter 2 categorized as inappropriate SR. In a prospective cohort (n . 30) that exhibited a failure to increase SR, atropine was administered to improve hemodynamic tolerance to VT. RESULTS In 150 patients, 261 VT episodes were analyzed (29% untolerated, 71% tolerated) with a median VT duration of 1.6 minutes. A total of 52% of VT episodes were associated with a sympathetic response, 31% had unchanged SR, and 17% of VTs exhibited a vagal response. A significantly higher prevalence of inappropriate SR responses was observed during untolerated VT (sustained VT requiring cardioversion within 150 seconds) compared with tolerated VT (84% vs 34%; P < 0.001). Untolerated VT was significantly different between groups: 9% (sympathetic), 82% (vagal), and 32% (unchanged) (P < 0.001). Atropine administration improved hemodynamic tolerance to VT by 70%. CONCLUSIONS Nearly one-half of VT episodes are associated with failure to augment SR, indicative of an underrecognized pathophysiological vasovagal response to VT. Inappropriate SR responses were more predictive of hemodynamic instability than VT rate and ejection fraction. Vagolytic therapy may be a novel method to augment blood pressure during VT.   https://www.hrsonline.org/education/TheLead https://www.jacc.org/doi/10.1016/j.jacc.2023.06.033 Host Disclosure(s): J. Jacobson: Honoraria/Speaking/Consulting: Zoll Medical, Abbott Medical, Vektor Medical, Stocks, Privately Held: Atlas 5D, Research: CardioFocus, Inc.   Contributor Disclosure(s): M. Robinson: Honoraria/Speaking/Consulting: Biosense Webster, Inc., Boston Scientific, Abbott, Membership on Advisory Committees: Medtronic Inc. S. Iwai: Honoraria/Speaking/Consulting: Alta Thera Pharmaceuticals, Biotronik