Prediction of early recurrence of atrial fibrillation after external cardioversion by means of P wave signal-averaged electrocardiogram

BACKGROUND

Therapy of atrial fibrillation by electrical cardioversion (CV) is limited by the high rate of recurrences. Early recurrence of atrial fibrillation (ERAF) occurs in a subgroup of patients whose characteristics are poorly defined. This prospective study was performed to evaluate if the P wave signal-averaged ECG (PSAECG) is able to identify patients with an increased risk of ERAF after CV.

METHODS

Patients with an indication for elective external CV were enrolled. After successful CV, PSAECGs were recorded at 0.5, 1, 24 h and 1 week. The ability of PSAECG parameters (signal-averaged P wave duration, PWD; root-mean-square of the voltage of the terminal 20, 30, and 40 ms of the signal-averaged P wave; RMS20, RMS30, RMS40) to predict ERAF (prospectively defined as AF recurrence within 4 h after CV) was assessed.

RESULTS

Of 111 consecutive patients, 7 experienced ERAF, 30 patients had AF recurrence later during the 1-week follow-up. Patients with ERAF had a significantly prolonged signal-averaged PWD compared to patients who remained in SR (194+/-16 ms vs 139+/-3 ms at 0.5 h, p<0.001). As ROC analysis revealed, a PWD >/=154 ms at 30 min after CV had the highest predictive accuracy for ERAF (sensitivity 100%, specificity 82%, positive predictive value 33%, negative predictive value 100%). Other parameters of the PSAECG did not reveal significant differences between patients with and without ERAF.

CONCLUSIONS

The PSAECG provides a sensitive noninvasive tool for detection of patients at risk of ERAF. Thus identified, tailored pharmacological therapy is conceivable to prevent ERAF.

Relationship between clinical and echocardiography-derived parameters and atrial activation as measured by the P-wave signal-averaged electrocardiogram

P-wave signal averaging is used in an attempt to detect patients at risk of atrial arrhythmias, particularly atrial fibrillation. Although many studies utilized this method, data on the relationship between clinical and echocardiographic variables and signal averaged P-wave parameters are sparse. Thus, we performed a prospective study to evaluate the influence of important clinical and echocardiographic variables on P-wave parameters. The study included 100 probands without demonstrable cardiac disease. P-wave signal averaging was performed after echocardiographic examination in all subjects. Overall P-wave duration averaged 122 +/- 16 ms and correlated significantly with age, left atrial and left ventricular end-diastolic diameter on univariate analysis (r = 0.287, 0.393 and 0.375; p = 0.004, < 0.0001 and < 0.0001, respectively). On multivariate analysis, however, age was the only independent factor affecting signal averaged P-wave duration (p = 0.02). There were statistically significant differences in left atrial size and P-wave duration if probands were grouped according to their age.

CONCLUSION

There is a significant relationship between signal averaged P-wave duration and age. This may be due to increased atrial fibrosis in elderly subjects. These data should be considered when signal-averaged P wave duration is used as a risk stratifier in patients prone to atrial fibrillation.