Electrophysiological features in patients with sinus node dysfunction and vasovagal syncope

INTRODUCTION: Syncope is a common presentation of sinus node dysfunction (SND). Some patients who receive a permanent pacemaker due to SND do not benefit from it and further diagnostic workup leads to the diagnosis of vasovagal syncope (VVS). The aim of the study was to identify electrophysiological criteria that can be used for identification of patients with SND and concurrent VVS. MATERIAL AND METHODS: Transoesophageal atrial pacing (TAP) was performed in 100 patients divided into four groups depending on symptoms and TAP results. Standard electrophysiological parameters of sinus node function and their variability were obtained in the basal state and after pharmacological autonomic blockade (AB). RESULTS: Patients with concurrent SND and VVS had a greater variability of sinoatrial conduction time assessed by Strauss' method than patients without incidents of syncope (83.2 ±53.9 vs. 34.1 ±19.6, 47.8 ±33.6 and 32.1 ±22.99). Apart from abnormal sinus node recovery time and second pause, patients with SND had bigger basal state variability of these parameters. In patients with SND and concurrent vasovagal syncope the variability of sinus node recovery time (SNRT), corrected SNRT (cSNRT) and second pause (IIP) decreased after autonomic blockade. CONCLUSIONS: Patients with concurrent SND and VVS have distinct electrophysiological features - greater sinoatrial conduction time (SACT) variability and the decrease of SNRT, cSNRT and IIP variability after AB. However, further studies in larger study groups are needed to validate our findings. Transoesophageal atrial pacing is a useful procedure in patients with syncope, especially when the coexistence of more than one cardiac cause is suspected.