Catheter Ablation -> Ventricular Arrhythmias -> Physiology-Pharmacology D-PO06 - Poster Session VI (ID 26) Poster

D-PO06-114 - Vasovagal Responses During Human VT:Autonomic Determinant Of Hemodynamic Stability (ID 673)

 J.M. du Fay de Lavallaz: Nothing relevant to disclose.


Background: Rates of tachycardia and ejection fraction are central determinants of hemodynamic tolerance during ventricular tachycardia (VT).
Objective: While prior research showed increased sympathetic nerve activity during tolerated VT, the impact of vagally-mediated reflexes have not been studied during induced monomorphic VT.
Methods: We evaluated the adequacy of a sympathetic response to VT by assessing the sinus rate (SR) cycle length (CL) during induced monomorphic VT. The SR was measured before VT induction and compared at 5, 10, 15, 30, 60, 90, 120 and 150s into the VT episode. Responses were classified into 3 groups: decreasing (<5 bpm at 5s, vagal response), unchanged (lack of sympathetic gain), and increasing (>5bpm at 5s, sympathetic response). VT CL and VT intolerance (defined as the need for shock despite pressors) were recorded.
Results: Amongst 17 patients, 39 episodes of VT were assessed. The median duration of VT was 6.3min with a median TCL of 343.0ms. 21% of VTs were associated with a vagal (median SR 75 to 57.5 bpm), 38% with a sympathetic (median SR 83 to 102 bpm) and 41% with an unchanged response. A vagal/unchanged response was observed in 75% of the 8 untolerated VTs that required defibrillation at a median time of 2.3min (IQR 1.2-8.5) but only in 58% of tolerated VT episodes.
Conclusion: A spectrum of autonomic responses was observed during sustained monomorphic VT with the majority demonstrating a failure to augment SR. These data support the notion that vagal responses and lack of sympathetic gain may be important determinants of hemodynamic tolerance to VT. Inhibition of vagal responses may improve the ability to map VT during ablation procedures.