WITHIN-PATIENT AND BETWEEN-PATIENT VARIATION OF THE SIGNAL-AVERAGED P-WAVE IN CORONARY-ARTERY DISEASE

Objectives: To estimate interobserver, within-patient and between-pati ent variation of the signal-averaged P wave. To determine whether demo graphic, clinical, conventional ECG information, and coronary angiogra phic data are associated with the signal-averaged P wave duration in p atients with documented coronary artery disease. Background: A prolong ed signal-averaged P wave may indicate the presence of a substrate for atrial tachyarrhythmias and may predict subsequent development of atr ial fibrillation. However, information on variation, reproducibility, and determinants of the signal-averaged P wave are sparse. Methods: On e hundred ninety-three patients with angiographically documented coron ary artery disease underwent two consecutive procedures of signal-aver aging of P waves (SAECG1 and SAECG2). Interobserver, within-patient, a nd between-patient variation of the signal-averaged P wave was estimat ed (coefficient of variation: SD/mean). Multiple linear regression ana lysis was applied to identify parameters independently associated with signal-averaged P wave duration ISA-P). Atrial late potentials were c onsidered if SA-P > 140 ms, and logistic regression analysis was appli ed to identify parameters associated with the presence of atrial late potentials. Results: The interobserver, within-patient, and between-pa tient coefficients of variation for the signal-averaged P wave duratio n were 7.5%, 6.0%, and 8.4%, respectively. The:signal-averaged P wave duration correlated significantly with standard ECG P wave duration an d height of the patient (r = 0.59). Forty-nine percent of the patients had atrial late potentials. P wave duration in the standard ECG corre ctly classified 73% (140/188) of the patients with respect to atrial l ate potential positivity or negativity. The sensitivity was 67% and th e specificity was 78%. Agreement on the presence or absence of atrial late potentials between two observers was present in 71% (136/193) of the patients, and in 78% (151/193) between SAECG1 and SAECG2. Conclusi ons: The signal-averaged P wave has limited reproducibility in patient s with coronary artery disease, and a normal or abnormal signal-averag ed P wave can be predicted from the conventional ECG with high accurac y. It is recommended that the signal-averaged P wave be compared with the standard ECG P wave duration in follow-up studies with the aim of predicting atrial fibrillation.