Assessment of Systolic Ejection Time as a Hemodynamic Marker of Incipient Bradycardic Vasovagal Syncope. A Pilot Study

Abstract

Detection of markers of incipient syncope in patients with vasovagal syncope (VVS), without prodromal symptom, is still an open issue. The aim of this study was to assess the behavior of heart rate (HR) and ejection time, expressed as the percentage of the corresponding cardiac cycle (ET%), in patients with bradycardic VVS with a view to providing an alarm before the event. In 33 patients with syncope and positive tilt testing and in 33 control patients, we collected beat-to-beat data on HR, ET%, stroke volume (SV), and blood pressure (BP). The trends of HR and ET% were analyzed. A set of combined changes of HR and ET% were tested in order to select the most appropriate algorithm for detecting the incipient syncope within the 3 minutes preceding the event. In patients with positive tilt testing, BP significantly decreased at 3 minutes before and at the time of syncope (P < 0.0001). HR slowly rose at 3 minutes before syncope and then suddenly decreased at the time of syncope (P < 0.0001). The correlation between SV and ET% was r = 0.79 (P < 0.0001). SV and ET% significantly decreased throughout tilt testing (P < 0.0001). The selected setting for the algorithm provided sensitivity of 97% and specificity of 73%. The theoretical alarm was generated at least 9 and 5 seconds before syncope, respectively, in 76% and 85% of the subjects. The combined trends in HR and ET% may provide a marker of incipient bradycardic VVS in the majority of patients.