Vasovagal syncope is the most common cause of syncope. Upright tilt table test is commonly performed for the evaluation of syncope, although the test has limited specificity, sensitivity, and reproducibility. The most frequent mechanism for vasovagal syncope is a cardioinhibitory response. Alterations in autonomic activation are responsible for cardioinhibitory syncope. Objective of our preliminary study is to investigate the potential diagnostic role of a maneuver previously described by Un et al. in patients with syncope. We hypothesize that maneuver significantly lowers heart rate in cardioinhibitory syncope patients with altering autonomic activation. Mentioned maneuver is consisted of quickly lying the subject backward from a seated to supine position (Figure1a). We enrolled 20 patients (10 syncope patients,10 healthy control) to this preliminary study. Study groups were constructed with sex and age matched participants. Median age was 25 years old in both groups.

All syncope patients were diagnosed with cardioinhibitory syncope during upright tilt table test. Maneuver was applied to patients under continuous electrocardiographic (ECG) monitoring. Because of small sample size we used bootstrapped confident events. We compared basal heart rates between groups with Mann-Whitney U test. Basal and after maneuver heart rates compared within groups with Wilcoxon Signed Rank Test. Median basal heart rate in control and syncope patients were 90 bpm(95% Bootstrap CI 70-102), 94 bpm (95% Bootstrap CI 75-100) respectively. There was no difference in basal heart rates between groups(p=0.836). Median heart rate after maneuver was 75 bpm (%95 Bootstrap CI 55-88) in syncope patients and 90 bpm (%95 Bootstrap CI 70-102) in control group. On Figure 1b and 1c basal and after maneuver ECGs of a patient are seen respectively. We did not find difference in heart rate of control group patients butthere was a statistically significant decrease in heart rate after the maneuver in syncope patients(p=0.480 vs. p=0.028). As a result this maneuver may be a potential diagnostic tool for identification of cardioinhibitory syncope patients.