Combined algorithm using a poor increase in inferior P-wave amplitude during sympathetic stimulation and sinus node recovery time for the diagnosis of sick sinus syndrome

Background: This study sought to evaluate whether a poor increase in inferior P-wave amplitude during sympathetic stimulation might be a helpful diagnostic tool for sick sinus syndrome (SSS). Methods and Results: Three-dimensional electroanatomic mapping of the right atrium, inferior P-wave amplitude and conventional corrected sinus node recovery time (CSNRT) were compared in 112 consecutive atrial fibrillation (AF) patients with (n=21) and without SSS (n=91). The significant cranial shift of earliest activation site (EAS) (the distance from the superior vena cava to the EAS: 11.1 vs. 5.9 mm, P<0.001) and the increases of inferior P-wave amplitudes during isoproterenol infusion (all P<0.001) were observed in patients without SSS. However, cranial shift of EAS (16.5 vs. 14.2 mm, P=0.375) and P-wave amplitude increases were not observed in those with SSS. Although CSNRT >550 ms showed a sensitivity of 50% and specificity of 84% for diagnosing SSS, poor increases of P-waves amplitude in lead aVF (<0.1 mV) during isoproterenol infusion showed an improved sensitivity of 71% and specificity of 89%. Finally, the combined algorithm using CSNRT >550 ms and poor increase of P-waves amplitude in lead aVF showed more improved diagnostic accuracy (sensitivity 89%, specificity 75%). Conclusions: A combined algorithm using inferior P-wave amplitude showed improved performance for the diagnosis of SSS compared with CSNRT >550 ms alone.