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The signal averaged P wave in atrioventricular block--evidence for abnormal atrial conduction?
P J Stafford1, J Cooper, S Baker
1Academic Department of Cardiology, Glenfield General Hospital, Leicester, UK.
Insights
Patients with atrioventricular block (AVB) and pacemakers show abnormal atrial activation, increasing atrial fibrillation risk. This suggests intrinsic atrial issues, not just pacing, contribute to fibrillation incidence.
Area of Science:
- Cardiology
- Electrophysiology
- Biomedical Engineering
Background:
- Atrial fibrillation (AF) incidence is higher in patients with atrioventricular block (AVB), even with dual-chamber pacing.
- The role of concurrent atrial activation abnormalities in AF development in AVB patients requires further investigation.
Purpose of the Study:
- To assess if atrial activation abnormalities contribute to the increased incidence of atrial fibrillation in patients with AVB and pacemakers.
- To compare signal-averaged P wave (SAPW) recordings in paced AVB patients versus unpaced controls.
Main Methods:
- Signal-averaged P wave (SAPW) recordings were performed in 15 patients with dual-chamber pacemakers for AVB and 21 unpaced controls.
- Measurements included P wave duration, spatial velocity, and spectral energy (Fourier transformation).
- Analysis focused on differences in these parameters between the AVB and control groups.
Main Results:
- Patients with AVB exhibited significantly increased P wave duration (144 ms vs. 134 ms).
- Mean spatial velocity was higher in AVB patients (5.6 mV/s vs. 4.6 mV/s).
- Lower frequency spectral energy (20-150 Hz) was significantly greater in the AVB group (57.4 μV².s vs. 36.3 μV².s).
Conclusions:
- Intrinsic abnormalities in atrial activation are suggested in patients paced for AVB.
- These findings indicate that atrial fibrillation in this population may stem from underlying atrial issues, not solely pacing mode.
- Sequential atrioventricular pacing might not fully mitigate the elevated risk of atrial fibrillation.
Abstract:
The incidence of atrial fibrillation in patients with atrioventricular block (AVB) appears increased over that for the unpaced population even if atrioventricular synchrony is maintained by dual chamber pacing. To assess whether atrial fibrillation in these patients might be due to concurrent abnormality in atrial activation we performed signal averaged P wave (SAPW) recordings in 15 patients with dual chamber pacemakers implanted for AVB and compared the results to those from 21 unpaced controls. The median (range) age was 69 (53-89) years for patients and 60 (51-78) years for controls. Eleven patients and 12 controls were male. All patients were pacing in VDD mode at the time of study. SAPW recordings were obtained using our previously reported selective P wave averaging system. We measured P wave duration after high pass filtering at 40 Hz, the rate of change of P wave voltage over time (spatial velocity) and low and high frequency spectral energy after Fourier transformation of the P wave signal. We found increased P wave duration, mean spatial velocity and lower frequency energy in patients with AVB compared to controls [duration, 144 (5) vs. 134 (2) ms, p<0.05; mean spatial velocity, 5.6 (0.4) vs. 4.6 (0.1) mV/s, p<0.05; energy 20-150 Hz, 57.4 (8.2) vs. 36.3 (2.8) muV2.s, p<0.01. All values mean (SEM)]. These results suggest that the increased incidence of atrial fibrillation in patients paced for AVB may be related to intrinsic abnormalities of atrial activation and not solely to the pacing mode. Ensuring sequential atrioventricular pacing in these patients may not completely abolish the increased incidence of atrial fibrillation.