Hemodynamics changes after tilting and the efficacy of preventive drugs

Background: We investigated whether hemodynamics changes during head-up tilt test (HUT) predict the efficacy of preventive drugs in neurally mediated syncope (NMS) patients, in order to clarify the differences between drug responders and nonresponders.
Method: In 402 patients with syncope, we examined HUT. In 66 patients with induced NMS, we administered propranolol when heart rate (HR) > 60 and systolic blood pressure (SBP) > 100 mmHg. When HR ≤ 60 or SBP ≥ 100, we administered disopyramide. After administration of each drug we examined HUT test again.
Results: Propranolol prevented NMS in 9/20 patients (propranolol responder group (pro-res group)). In pro-res group, systolic blood pressure (SBP), diastolic BP (DBP), and total peripheral resistance (TPR) at upright position (UP) before propranolol were significantly increased as compared to those at supine position (SP) (P < 0.05). But in propranolol nonresponder (pro-nonres group) SBP was not increased. After propranolol, DBP and TPR at UP was not increased in pro-nonres group. Propranolol inhibited the increase of low-frequency/high-frequency ratio (LF/HF) after tilting in pro-res group. Disopyramide prevented NMS in 14/32 patients (disopyramide responder group (dis-res group)). In dis-res group, DBP and TPR at UP before disopyramide was significantly increased as compared to that at SP (DBP P < 0.0001, TPR P < 0.05). But in disopyramide nonresponder group (dis-nonres group), DBP and TPR were not increased. After disopyramide, DBP and TPR at SP were significantly increased as compared to that before disopyramide in dis-res group (P < 0.05).
Conclusion: The hemodynamics changes after tilting during HUT predict the efficacy of two preventive drugs for NMS induced by HUT.