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 t he signal-averaged P wave corresponding to the electrical activity of the perinodal atrial myocardial cells. Background. In sick sinus syndr ome, pathophysiologic abnormalities have been shown not only in the si nus node, but also in the atrial muscle, especially the perinodal port ion. Methods. The study included 41 patients with sick sinus syndrome and 140 age-matched control subjects, Eighteen of 41 patients with sic k sinus syndrome had paroxysmal atrial fibrillation. Signal-averaged P wave electrocardiograms (ECGs) were recorded through a bandpass filte r of 40 to 300 Hz with a P wave-triggering technique. Signals of the o rthogonal bipolar leads were combined into a spatial magnitude. The ro ot mean square voltage for the initial 30 ms (EP30) and the duration o f initial low amplitude signals <4 mu V (ED4) of the filtered P wave w ere measured. The root mean square voltage For the last 20 ms (LP20) a nd the duration of the filtered P wave were also measured. Results. EP 30 was significantly lower and ED4 was significantly longer in patient s with sick sinus syndrome than in the control subjects (EP30 [mean +/ - SD]: 2.18 +/- 0.90 vs. 3.94 +/- 1.45 mu V, p < 0.0001; ED4: 31.7 +/- 14.5 vs. 14.0 +/- 7.4 ms, p < 0.0001), although there was no signific ant difference in LP20 between patients with sick sinus syndrome witho ut paroxysmal atrial fibrillation and the control subjects. The durati on of the filtered P wave was significantly but minimally longer in pa tients with sick sinus syndrome than in the control subjects (139.8 +/ - 15.8 vs. 127.3 +/- 13.6 ms, p < 0.0001). The criteria of EP30 <3.0 m u V and ED4 >22 ms as atrial early potential gave a sensitivity of 76% , a specificity of 98%, a positive predictive value of 74% and a negat ive predictive value of 93% for identification of patients with sick s inus syndrome. Conclusions. These results suggest that the long, low a mplitude signals early in the filtered P wave on the signal-averaged E CGs are characteristic of sick sinus syndrome. Thus, the atrial early potential could be a useful marker to identify patients with sick sinu s syndrome.