Dynamic Changes of P‐Wave Duration and P‐Wave Axis During Head‐Up Tilt Test in Patients with Vasovagal Syncope

Abstract

The exact role of venous pooling in the pathogenesis of vasovagal syncope (VVS) is not fully elucidated. P-wave duration on an electrocardiogram can serve as a measure of atrial volume. Sixty-six patients (15 men, 51 women, mean age 32 years) with unexplained syncope were enrolled in the study.P-wave duration and the P-wave axis (PWA) were measured during passive head-up tilt test (HUT) in order to evaluate dynamic changes of atrial filling in patients with VVS. HUT was positive in 40 patients (6 men, 34 women, mean age 32 +/- 9 years) and negative in 26 patients (9 men, 17 women, mean age 33 +/- 8 years). The P-wave duration was significantly reduced in HUT-positive patients at the onset of symptoms as compared to 5 minutes (88.8 +/- 11.9 vs 96.2 +/- 12.0 ms, P = 0.008), and baseline (88.8 +/- 11.9 vs 96.8 +/- 13.8 ms, P = 0.005). The P-wave duration was significantly shorter at the onset of presyncope in HUT-positive patients as compared to HUT-negative patients (88.8 +/- 11.9 vs 100.3 +/- 11.2 ms, P = 0.0002). In HUT-positive patients, a significant increase in PWA was found at the onset of symptoms when compared to baseline (67.7 +/- 22.1 degrees vs 47.9 +/- 14.9 degrees, P < 0.0001) and 5 minutes of HUT (67.7 +/- 22.1 degrees vs 54.4 +/- 14.9 degrees, P = 0.005). At the time of syncope, PWA was more inferior in HUT-positive patients than in HUT-negative patients (67.7 +/- 22.1 degrees vs 51.8 +/- 13.8 degrees, P = 0.015). VVS is associated with the reduction in P-wave duration and the increase in PWA, which can be a result of exaggerated venous pooling and reduction in atrial volume.