Influence of structural heart disease on characteristics of atrial fibrillation recurrence in patients with dual-chamber pacemakers.

AIMS: The aim of the study was to prospectively examine the influence of structural heart disease (SHD) and sinus node dysfunction (SND) on the frequency and duration of atrial fibrillation (AF) episodes in patients with implanted pacemakers. METHODS: We examined episodes of AF in 207 patients (93 with SHD; 165 with SND) with known or suspected paroxysmal AF who underwent dual-chamber pacing. RESULTS: Seventy-one percent of all patients experienced at least one episode of AF during follow-up, with a mean burden of 3.3 +/- 6.4 h/d (median, 0.2 hours) and a mean frequency of 11.7 +/- 26.0 episodes per day (median, 1.4). The proportion of episodes longer than 6 hours was greater in patients with SHD when compared to patients without SHD. In a logistic regression model adjusted for SND, gender, and the 2-way interactions of SND, sex, and SHD, SHD was a significant factor (P = .0188) with the odds ratio of having an episode longer than 6 hours 3.4 times higher for patients with SHD than for patients without SHD. Older patients with SHD had less frequent but longer episodes compared to younger patients. In patients without SHD, there was no comparable age difference. Burden, frequency, and average episode length were not influenced by the presence or absence of SND. CONCLUSIONS: Patients with SHD have longer episodes of AF supporting the concept that SHD influences the underlying substrate to favor perpetuation.

Form analysis using digital signal processing reliably discriminates far-field R waves from P waves.

The correct detection of atrial arrhythmias by pacemakers is often limited by the presence of far-field R waves (FFRWs) in the atrial electrogram. Digital signal processing (DSP) of intracardiac signals is assumed to provide improved discrimination between P waves and FFRWs when compared to current methods. For this purpose, 100 bipolar and unipolar intracardiac atrial recordings from 31 patients were collected during pacemaker replacement and used for the off-line application of a novel DSP algorithm. Digital processing of the atrial intracardiac electrogram (IEGM) signals (8 bit, 800 samples/s) included filtering and calculation of the maximum amplitude and slope of the detected events. The form parameter was calculated, being the sum of the most negative value of the amplitude and that of the slope of the detected event. The algorithm collects form parameter data of P waves and FFRWs and composes histograms of these data. A sufficiently large gap between the FFRW and P wave histograms allows discrimination of these two signals based on form parameters. Three independent observers reviewed the reliability of classification with this algorithm. Sensitivity and specificity of FFRW detection were 99.63% and 100%, respectively, and no P waves were falsely classified. It can be concluded that this novel DSP algorithm shows excellent discrimination of FFRWs under off-line conditions and justify the implementation of this algorithm in future pacemakers for real-time discrimination between P waves and FFRWs. This method prevents false mode switching and allows correct and immediate intervention pacing for atrial tachyarrhythmias.