RISK FOR ATRIAL-FIBRILLATION IN PATIENTS WITH HYPERTROPHIC CARDIOMYOPATHY ASSESSED BY SIGNAL-AVERAGED P-WAVE DURATION

Objective-To assess the relation between P wave duration and the occur rence of atrial fibrillation in hypertrophic cardiomyopathy (HCM). Des ign-High resolution signal averaged electrocardiography was used in 11 0 patients with HCM to determine whether patients at risk for paroxysm al atrial fibrillation could be detected during sinus rhythm by measur ing P wave duration. Filtered P wave duration was measured manually, o ver an average of 300 beats per patient. Results-During follow up, 18 patients (16%) had at least one one clinical episode of paroxysmal atr ial fibrillation, including four patients whose initial episode follow ed the signal averaged electrocardiogram. The 18 patients with overt a trial fibrillation had greater P wave duration than the 69 patients wh o did not develop atrial fibrillation: 150 (SD 20) v 126 (14) ms; P < 0.001. Another 23 patients without clinically evident atrial fibrillat ion had prolonged bursts of the arrhythmia on Holter recording, and sh owed a P wave duration (138 (15) ms) intermediate between patients wit h and without clinical atrial fibrillation. In assessing risk for atri al fibrillation, P wave duration greater than or equal to 140 ms was a ssociated with sensitivity, specificity, and positive predictive accur acy values of 56%, 83%, and 66%. Multivariate analysis showed that dur ation of the P wave was the only independent variable associated with occurrence of atrial fibrillation; if P wave duration greater than or equal to 140 ms was combined with left atrial enlargement > 40 mm, the specificity and positive predictive accuracy for atrial fibrillation increased to 93% and 78%. Conclusions-Measurement of P wave duration i n sinus rhythm by high resolution signal averaged electrocardiography may be a useful non-invasive clinical tool for identifying patients wi th HCM Likely to develop electrical instability and atrial fibrillatio n.