Detection of patients with sick sinus syndrome by use of low amplitude potentials early in filtered P wave

Objectives. This study sought to determine whether patients with sick sinus syndrome could be detected by analyzing the initial portion of the signal-averaged P wave corresponding to the electrical activity of the perinodal atrial myocardial cells. Background. In sick sinus syndrome, pathophysiologic abnormalities have been shown not only in the sinus node, but also in atrial muscle, especially the perinodal portion. Methods. The study included 41 patients with sick sinus syndrome and 140 age-matched control subjects. Eighteen of 41 patients with sick sinus syndrome had paroxysmal atrial fibrillation. Signal-averaged P wave electrocardiograms (ECGs) were recorded through bandpass filter of 40 to 300 Hz with P wave-triggering technique. Signals of the orthogonal bipolar leads were combined into spatial magnitude. The root mean square voltage for the initial 30 ms (EP30) and the duration of initial low amplitude signals <4 μV (ED4) of the filtered P wave were measured. The root mean square voltage for the last 20 ms (LP20) and the duration of the filtered P wave were also measured. Results. EP30 was significantly lower and ED4 was significantly longer in patients with sick sinus syndrome than in the control subjects (EP30 [mean ± SD]: 2.18 ± 0.90 vs. 3.94 ± 1.45 μV, p < 0.0001; ED4: 31.7 ± 14.5 vs. 14.0 ± 7.4 ms, p < 0.0001), although there was no significant difference in LP20 between patients with sick sinus syndrome without paroxysmal atrial fibrillation and the control subjects. The duration of the filtered P wave was significantly but minimally longer in patients with sick sinus syndrome than in the control subjects (139.8 ± 18.8 vs. 127.3 ± 13.6 ms, p < 0.0001). The criteri of EP30 <3.0 μV and ED4 > 22 ms as atrial early potential gave sensitivity of 76%, specificity of 91%, positive predictive value of 74% and negative predictive value of 93% for identification of patients with sick sinus syndrome. Conclusions. These results suggest that the long, low amplitude signals early in the filtered P wave on the signal-averaged ECGs are characteristic of sick sinus syndrome. Thus, the atrial early potential could be useful marker to identify patients with sick sinus syndrome.