Introduction: The primary treatment for patients with long QT syndrome (LQTS) is beta blocker therapy. However, some patients still experience breakthrough cardiac events or intolerable side effects. Left cardiac sympathetic denervation (LCSD) provides a significant anti-fibrillatory, protective effect in LQTS. However, LCSD’s effects on heart rate, shown previously to increase in canine models, and cardiopulmonary fitness have not been evaluated.
Methods: An IRB-approved retrospective analysis was performed on all patients [N = 55, 39 (71%) female, mean age at LCSD 22 ± 12 years, mean follow-up 5.1 ± 2.5 years; 36 (65%) with LQT1; 15 (27%) with LQT2] with LQTS and LCSD performed between 2006 and 2017 who had both pre- and post-LCSD exercise stress tests (minimum post-LCSD duration = 2.5 months). Forty patients (73%) were on beta blockers pre-LCSD. Pre- and post-LCSD exercise stress test results were compared using paired student t-test for continuous values.
Results: Of the patients on beta blockers pre-LCSD, 32 (82%) remained on them post-LCSD, and 12 (38%) had no change in beta blocker dose. Ten patients had no exposure to beta blockers during pre- or post-LCSD exercise stress test (LCSD monotherapy), most commonly due to intolerance of beta blocker side effects. Overall, there was no significant difference in percent predicted peak heart rate during exercise testing (72% predicted pre-LCSD vs 71% predicted post-LCSD, mean diff -1%, p = 0.5). However, to evaluate the isolated effect of LCSD, we performed a subset analysis of patients treated with either LCSD monotherapy (N = 10) or those with an unchanged beta blocker dose (N=12). Patient matched pre- and post-LCSD exercise testing and echocardiography showed no difference in peak heart rate (mean difference 5 ± 2.5 bpm, p = 0.07), peak VO2 (mean difference 0.43 ± 1.5 mL/kg/min, p = 0.8), or left ventricular function following LCSD (pre-operative LVEDD = 47 mm and LVEF = 63% vs post-operative LVEDD = 48 mm and LVEF 63%, p = 0.5).
Conclusions: LCSD provides increased protection from a LQTS-triggered faint, seizure, or sudden cardiac arrest without negatively impacting peak heart rate, cardiopulmonary fitness, or cardiac contractility as assessed by treadmill exercise stress testing and echocardiography.