Noninvasive Assessment of Acute Changes in Atrial Electrophysiology After Cardioversion by Signal-Averaged P-Wave Electrocardiography

Usefulness of P-wave signal averaging to predict atrial fibrillation recurrences after electrical cardioversion

BACKGROUND

Accurate markers of atrial fibrillation (AF) recurrences after electrical cardioversion (ECV) are lacking. This study was conducted to assess the value of P-wave signal averaging (SAPW) for predicting AF recurrences in a nonselected patients population submitted to ECV.

METHODS

A total of 133 patients (107 males, 26 females, mean age 66 ± 9 years) were included after successful ECV for persistent AF (mean duration of AF 3.6 ± 2.2 months). The mean ejection fraction (EF) was 60 ± 9%, and left atrial (LA) diameter was 44 ± 6 mm. SAPW ECG was obtained immediately after ECV and patients were prospectively followed.

RESULTS

During a mean follow-up of 8.9 ± 5.2 months, AF recurrences occurred in 40.6% (54/133). No SAPW parameters was statistically different between the group of patients with and the group without recurrences. Recurrences were less often observed in patients with a total P-wave duration <150 ms (16/52 or 31% vs 38/81 or 47% in patients with total P-wave duration ≥150 ms) but the difference was not statistically different (P = 0.07). P-wave duration was correlated with age (r = 0.32; P < 0.001) and left atrial diameter (r = 0.19; P = 0.02). Age, sex, structural heart disease, amiodarone therapy, or hypertension were not associated with AF recurrences but patients without recurrences had a shorter AF duration (P = 0.001) and more often had a history of previous ablation (P = 0.027).

CONCLUSION

In this unselected "real-life" group of patients submitted to ECV for persistent AF, none of the SAPW parameters, including total filtered P-wave duration, was able to predict AF recurrences.

Reverse Electrical Remodeling of the Atria Post Cardioversion in Patients Who Remain in Sinus Rhythm Assessed by Signal Averaging of the P-Wave

OBJECTIVES

This study was designed to determine whether the signal-averaged electrocardiogram of the P-wave (SAPW) is an independent predictor of recurrence of atrial fibrillation (AF) post cardioversion (CV), and to assess atrial remodeling using SAPW.

BACKGROUND

There are limited electrophysiologic data to predict the recurrence of AF post-CV. The electrical remodeling that occurs post-CV is poorly understood.

METHODS

Sixty-four patients with persistent AF undergoing CV were prospectively enrolled. SAPW parameters were measured the day of CV and repeated at 1 month. These SAPW parameters were compared to other baseline indices for the recurrence of AF.

RESULTS

Sixty patients (94%) had successful CV. At 1 month, 22 (37%) maintained sinus rhythm (SR). The SAPW total duration decreased significantly in those who remained in SR (159 ms +/- 19 to 146 ms +/- 17; P < 0.0001). Only the duration of AF (46 +/- 50 days vs 147 +/- 227 days, P = 0.03) and the presence of left ventricular hypertrophy (LVH, 12% vs 65%, P = 0.0006) were significantly associated with recurrence of AF. Atrial size strongly correlated with the SAPW duration in patients who remained in SR (R(2)= 0.67, P = 0.003) but not in those who returned to AF (R(2)= 0.11, P = 0.65).

CONCLUSIONS

Atrial electrical reverse remodeling occurs in patients with AF who maintain SR post-CV. This remodeling is likely inversely related to the duration of AF and LVH. SAPW duration does not predict recurrence of AF post-CV.

Electrophysiological Properties of the Atrium After Cardioversion of Chronic Atrial Fibrillation Relation to the Plasma Brain Natriuretic Peptide Level

BACKGROUND

Brain natriuretic peptide (BNP) level has been shown to increase in patients with chronic atrial fibrillation (CAF) without overt heart failure (HF). Although atrial electrical remodeling associated with CAF has been described, little is known about the effects of the BNP level on the electrophysiological properties in CAF patients.

METHODS AND RESULTS

In 42 CAF patients without overt HF, the atrial monophasic action potential duration (MAPD) at pacing cycle lengths (CLs) of 300-800 msec and P-wave signal-averaged electrograms were recorded after cardioversion. The MAPDs for all CLs were significantly longer in patients with a BNP concentration greater than the 50th percentile (group 1, BNP = 215 +/- 118.2 pg/mL) than in patients with a concentration less than the 50th percentile (group 2, BNP = 68.3 +/- 20.9 pg/mL), resulting in a similar value in the MAPDs at CLs of 350 and 600 msec for group 1 and the control patients (n = 8). The slope value of the MAPDs between CLs of 350 and 600 msec was normal in group 1, but slightly lower in group 2 than in group 1 and control patients. The filtered P-wave duration did not differ between the two groups.

CONCLUSIONS

These electrophysiological characteristics related to the BNP level suggest that the atrial repolarization may be affected by a latent ventricular dysfunction.

Signal-Averaged P Wave Reflects Change in Atrial Electrophysiological Substrate Afforded by Verapamil Following Cardioversion from Atrial Fibrillation

BACKGROUND

Detailed analysis of signal-averaged P waves (SAPW) can provide insights into atrial electrophysiology. Abbreviated dosing of verapamil prior to cardioversion improves outcome at 1 week postcardioversion. The mechanism by which verapamil manifests benefit is uncertain. We hypothesized the SAPW would reflect any change in atrial electrophysiologic substrate afforded by verapamil when compared with controls.

METHODS

We investigated 23 patients attending external cardioversion of persistent atrial fibrillation (AF) (6 female; mean age 68 years). Patients were randomized to verapamil 240 mg daily in three divided doses 3 days before cardioversion and 1 week after, or usual medication. SAPW recordings were performed during sinus rhythm (SR) immediately after cardioversion, at 24 hours and 1 week.

RESULTS

The groups were comparable in terms of age, gender, left atrial size, and duration of AF. Eight of nine patients prescribed verapamil maintained SR at 1 week postcardioversion compared with 6 of 14 controls (P = 0.027). SAPW spectral analysis delivered higher energy for patients prescribed verapamil (median (IQ range)); 40.8 (33.4-95.1) versus 25.7 (19.0-38.0) for energy within 20-150 Hz, P20 (microV(2)x s; P = 0.03). There was no difference in P-wave duration (PWD) or root mean square of the terminal 30 ms between the two groups. Early reinitiation occurred in patients with significantly lower P-wave energy 19.6 (12.9-24.6) versus 39.9 (24.0-47.0) (P = 0.017).

CONCLUSIONS

Verapamil 240 mg daily for 3 days prior to cardioversion and 1 week after reduces early recurrence of AF. The SAPW observations indicate change in atrial electrophysiologic substrate might be responsible for benefit afforded by verapamil.