Value of the P-Wave Signal-Averaged ECG for Predicting Atrial Fibrillation After Cardiac Surgery

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Atrial fibrillation (AF) is a commonly encountered arrhythmia in clinical practice, and it occurs rquently after cardiac surgery. The P-wave signal-averaged (SA) ECG noninvasively detects atrial conduction delay. Prior studies have described greater P-wave prolongation in patients with a history of AF, but prospective studies have not been performed. Methods and Resuls. Consecutive patients undergoing cardiac surgery were enrolled. The P-wave SAECG was recorded before surgery from three orthogonal leads using a sinus P-wave template and a cross-correlation function. The averaged P wave was filtered with a least-squares-fit filter and combined into a vector magnitude, and total P-wave duration was measured. Patients were observed after cardiac surgery for the development ofAF. One hundred thirty patients were enrolled, and 33 (25%) developed AF 2.6±2.0 days after surgery. Patients with AF more often had left ventricular hypertrophy on ECG (P<.05) and had a lower ejection fraction (P<.05). The P-wave duration on the SAECG was significantly longer in the AF patients than in those without AF: 152±18 versus 139±17 milliseconds (P<.001). An SAECG P-wave duration >140 milliseconds predicted AF with sensitivity of 77%, specificity of 55%, positive predictive accuracy of 37%, and negative predictive accuracy of 87%. The likelihood of experiencing AF was increased 3.9-fold if the SAECG P-wave duration was prolonged. P-wave SAECG results were independent of other clinical variables by multivariate analysis.


The P-wave duration recorded with the SAECG is a potent, accurate, and independent predictor of AF after cardiac surgery.

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