Comparison of Efficacy, Pattern of Response, Occurrence of Arrhythmias, and the Tolerability of Nitroglycerine and Isoprenaline as Provocative Drugs During Head-Up Tilt Test

Background: Various protocols exist for performing head-up tilt test (HUTT). Serious ventricular arrhythmias have been reported during HUTT using Isoprenaline (ISO) provocation and their incidence with sublingual Nitroglycerine provocation is unknown. This study aims to assess the efficacy, pattern of response, tolerability, and frequency of arrhythmias during head-up tilt test with sublingual Nitroglycerine (NTG) provocation compared to ISO) provocation.

Methods: This is a retrospective observational study.

Result: From 2007 to 2015, a total of 816 patients (68% men, median age 49 IQR 25.75-65 years) underwent head-up tilt testing using sublingual NTG provocation whereas ISO was used in 189 patients (66.1% men, median age 48 IQR 36-60 years). A positive response was more frequently observed in the NTG group than the ISO group (48.4% vs 35.9%, p=0.002), with more frequent type II b (cardio-inhibition with >3sec asystole) and type III (vasodepressor) responses ([15. 9% vs 4.1%, p=0.001] and 0% vs 29.4%, p=0.004) respectively. Bradyarrhythmias occurring always as a part of a positive HUTT response were the commonest arrhythmias (29% in NTG group vs 25.4% in ISO group, p=0.31). Tachyarrhythmias (or premature beats) were more frequent in the ISO group (12.7% vs 7.9%, p=<0.005). The use of NTG was significantly associated with a positive response (OR 1.775, 95% CI 1.269-2.483, p=0.001), whereas the use of ISO predicted the occurrence of premature beats/tachyarrhythmias (OR 3.06, 95% CI 2.195-4.267, p<0.005). Intolerance needing termination of the test was significantly more frequent in the ISO group than NTG group (1.6% vs 0.12%, p= 0.02).

Conclusion: Head-up tilt test with NTG provocation has a higher yield of a positive response, lower incidence of unwanted arrhythmias and better tolerability compared to ISO. The occurrence of VASIS type II b and type III response was more with Nitroglycerine than Isoprenaline.