Longitudinal Change of Electrophysiological Characteristics in Patients with Sick Sinus Syndrome

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Introduction: Previous studies have showed stable AV conduction in patients with sick sinus syndrome (SSS) during long-term follow-up. However, detailed electrophysiological (EP) data is not clearly enucleated. Methods: Fifty-six patients (30 males, mean age: 68±10 years) with SSS were enrolled. EP study was performed at the time of pacemaker implantation and replacement. Mean followed-up duration was 8.5±2.3 years. Results: Sinus node recovery time (SRNT) (2431±1630 vs. 3390±2368 ms), 1:1 AV conduction (484±160 vs. 548±161 ms), point of AV block (AVB) (453±153 vs. 502±152 ms) and ventricular effective refractory period (265±27 vs. 296±50 ms) were significant prolonged (p<0.05). VA conduction and VA block did not demonstrate significant change. Although SRNT was prolonged, comparison of atrial pacing percentage at the year 1 and year 8, pacing percentage was constant (72±28 vs. 81±28%). Eleven of 56 patients (20%) presented with initial AVN dysfunction but only 3 patients (5.4%) developed advanced AVB (>800 ms). Six of 45 patients (13%) with intact AVN function developed new onset AVN dysfunction but none has advanced AVB. Conclusion: Panconduction system was degenerated in the SSS patients during long-term followed-up. AV conduction was relative stable but advanced AVB would occur in the patients with initial AVN dysfunction. Pre-implantation EPS may be useful to predict the risk of advanced AVB.