Effect of passive tilting duration on the outcome of head-up tilt testing

OBJECTIVE: We sought to compare the results of head-up tilt test (HUT) using the most common protocols, namely the Italian and Westminster prolonged by nitroglycerin (modified Westminster) protocols. We also investigated the role of passive tilting duration on HUT outcome. METHODS AND RESULTS: From 478 syncopal patients 306 (64%) individuals showed positive tilting results (HUT+), whereas the remaining 172 (36%) were negative (HUT-). A total of 277 patients were tilted using the Italian protocol (20-min passive tilting), while the remaining 201 underwent the modified Westminster (45-min passive tilting) protocol. Univariate analysis showed significant differences (P < 0.001) in the time for syncope induction and number of HUT+ between the Italian (153/277, 55%) and modified Westminster protocols (153/201, 76%). A reduced rate (P < 0.01) of cardioinhibitory responses was observed in the Italian (16/153, 10%) compared to the modified Westminster (31/153, 20%) protocol. The presence of HUT+ was positively associated with the use of the modified Westminster protocol (76%, P < 0.001) and typical vasovagal history (83%, P < 0.001), and negatively with body mass index (BMI) (P < 0.05) and hypertension (P < 0.01). With the use of the Italian protocol, HUT+ negatively associated with BMI (P < 0.05) and hypertension (P < 0.05), and positively with typical vasovagal history (71%, P < 0.01). With the use of the modified Westminster protocol, HUT+ strongly correlated with typical vasovagal history (78%, P < 0.001), but not with either BMI or hypertension. CONCLUSIONS: The HUT protocol may influence tilting outcome. The modified Westminster protocol seems to be more useful than the Italian protocol for syncope diagnosis, especially to avoid underestimation of the cardioinhibitory responses.