Electrocardiographic characteristics of pacing from the right atrial appendage during atrioventricular sequential pacing

Effect of pacing site on P wave parameters: Within-patient comparison of right atrial appendage and Bachmann's bundle

BACKGROUND

Conventional right atrial appendage pacing (RAAp) is associated with adverse clinical outcomes mediated in part by electromechanical atrial delays. Bachmann's bundle pacing (BBp) offers more physiologic atrial activation; however, detailed analysis of pacing site on paced P wave parameters is lacking.

METHODS

Intraprocedural electrocardiograms of 21 consecutive patients undergoing atrial lead implantation were retrospectively analyzed and within-patient comparisons of 7 P wave parameters (P wave duration, P wave voltage, P wave area, PR interval, PR segment, PTFV1 and P wave axis) during sinus rhythm, RAAp and BBp performed.

RESULTS

The median basal P wave duration was prolonged at 134.5 ms (Q1,Q3: 120.5, 150.5) and similarly prolonged during RAAp at 144.0 ms (127.0, 176.0) but was significantly reduced with BBp at 98.0 ms (93.0, 116.0; p = 0.005 and p < 0.001, respectively). The median basal P wave voltage in lead II was normal at 0.11 mV (0.08, 0.15) but significantly reduced during RAAp at 0.08 mV (0.04, 0.11) and greatest during BBp at 0.16 mV (0.09, 0.19; p < 0.001 and p = 0.003, respectively). The median basal PR interval was top normal at 185.0 ms (163.0, 213.0) and similarly prolonged during RAAp at 204.0 ms (166.5, 221.0) but was significantly shortened during BBp at 163.0 ms (142.0, 208.0; p = 0.03 and p = 0.001, respectively).

CONCLUSIONS

BBp has favorable effects on the paced P wave parameters including marked shortening in P wave duration, increase in P wave voltage in lead II and increase in PR segment which may offer significant hemodynamic advantages over conventional RAAp.

Alternative atrial pacing site to improve cardiac function: focus on Bachmann's bundle pacing

Pacing from the right atrial appendage (RAA) prolongs the P wave duration and can induce interatrial and especially left-sided atrio-ventricular dyssynchrony. Pacing from Bachmann's bundle closely reproduces normal physiology and has the potential to avoid the electromechanical dysfunction associated with conventional RAA pacing. Interatrial conduction delay is associated with an increased risk of stroke, heart failure, and death. In addition to a reduction in atrial fibrillation, Bachmann's bundle pacing has emerging applications as a hemodynamic pacing modality. This review outlines the pathophysiology of atrial conduction disturbances and their potential remedies and provides the reader with a practical guide to implementing Bachmann's bundle pacing with an emphasis on the recapitulation of normal electrical and mechanical function.

Alternate methods for the determination of atrial capture threshold utilizing the telemetered intracardiac electrogram

Periodic determination of pacemaker capture threshold is important to ensure appropriate pacemaker function. During dual chamber pacing, it is sometimes difficult to identify evidence of atrial depolarization on surface electrocardiography (ECG), and this can interfere with the ability to ascertain atrial capture. We describe new methods for determining atrial capture threshold using a standard telemetered endocardial atrial electrogram (AEGM). For the first method, the atrial output is decremented until loss of atrial capture is demonstrated by the appearance of native P wave activity on the AEGM. The atrial capture threshold can then be accurately determined as the point at which a stepwise increase in atrial output results in extinction of the native P wave activity. The second method uses the direct visualization of the AEGM recorded between the ring electrode and pacemaker generator during unipolar (lead tip electrode) pacing. This requires the presence of a bipolar lead. Using this method of recording, it is possible to identify a signal after the atrial stimulus artifact during atrial capture, which disappears with loss of capture. This signal is consistent with a paced "evoked atrial potential" and allows verification of atrial capture. After validating the methods in two sets of test patients with clearly identifiable atrial depolarization on surface ECG, one method was successfully applied to a patient in whom atrial depolarization could not be reliably ascertained on surface ECG. These methods promise to be useful in selected patients in whom confirmation of atrial capture would otherwise be difficult.