Baroreflex Sensitivity Predicts the Head-Up Tilt Test Induced Asystole Among Patients With Suspected Vasovagal Syncope

The impairment of baroreflex sensitivity (BRS) has been hypothized in patients with vasovagal syncope (VVS). The aim of our study was to assess the baroreflex sensitivity in patients with suspected vasovagal syncope who underwent head up tilt test (HUTT) and its role in predicting the HUTT response. Baroreflex sensitivity (BRS) was calculated using the sequence method in 224 consecutive patients (mean age 40.2 ± 22.6 years, 47.3% males) with suspected VVS who underwent NTG potentiated HUTT and 20 consecutive controls (mean age 37.5 ± 22.6 years, 66% males) with no history of syncope. BRS values at rest and during HUTT were compared across the subgroups of study population. A ROC curve analysis was performed to a BRS cutoff value for HUTT positivity and HUTT induced asystole. Multivariable analysis was performed to independent association of BRS cutoff values with HUTT results. At baseline, VVS patients showed higher BRS values compared to controls (7 ± 3.5 vs 4.4 ± 1.9 ms/mmHg; p = 0.0013). BRS values were higher (8.1 ± 3.7 vs 4.8 ± 2.1 ms/mmHg; p = 0.0001) among 145 patients with HUTT positivity (64.73%) compared with those with negative result. A BRS value > 6.95 ms/mmHg served as independent predictor of HUTT positivity; a BRS value > 8.2 ms/mmHg showed a sensitivity of 66.7% and specificity of 82.1% in predicting HUTT induced asystole. In conclusion VVS patients showed an enhanced baroreflex sensitivity compared to those with no history of syncope. Among VVS patients, BRS served as independent predictor of positive HUTT response and asystole.