Temporal relationship between hemodynamic changes and activation of Closed Loop Stimulation during tilt-induced vasovagal syncope.

AIMS: Dual-chamber pacemaker with Closed Loop Stimulation (CLS) mode is effective in reducing syncopal recurrences in patients with asystolic vasovagal syncope (VVS). In this study we explored hemodynamic and temporal relationship of CLS during tilt-induced vasovagal reflex.

METHODS: Twenty patients underwent tilt test under video recording 3.9 years after CLS pacemaker implantation.

RESULTS: Three patients were excluded from the analysis because of no VVS induced by tilt test (n=1) and protocol violation (n=2). In 14 of the remaining 17 patients, CLS pacing emerged during the presyncopal phase of circulatory instability when the mean intrinsic heart rate was 88±12 bpm and systolic blood pressure (SBP) was 108±19 mmHg. The CLS pacing rate thereafter rapidly increased to 105±14 bpm within a median of 0.1 minutes (IQR, 0.1-0.7 minutes) when the SBP was 99±21 mmHg. At the time of maximum vasovagal effect (syncope or presyncope), SBP was 63±17 mmHg and CLS rate was 95±13 bpm. The onset of CLS pacing was 1.7 minutes (IQR, 1.5-3.4) before syncope or lowest SBP. The total duration of CLS pacing was 5.0 minutes (IQR, 3.3-8.3). CLS pacing was not observed in three patients who had a similar SBP decrease from 142±22 mmHg at baseline to 69±4 mmHg at the time of maximum vasovagal effect, but there was no significant increase in HR (59±1 bpm).

CONCLUSION: The reproducibility of a vasovagal reflex was high. High-rate CLS pacing was observed early during the presyncopal phase in most patients and persisted, albeit attenuated, at the time of maximum vasovagal effect.