[Atrial lead placement in cases of intraoperative atrial fibrillation]

Evaluating the efficiency of a prescribed concept for atrial lead placement in cases of intraoperative atrial fibrillation (AF).

Over the period from 11/1998 to 5/2000, we carried out a prospective study on 40 patients with AF. After implantation of the screw electrode into the lateral wall of the atrium, an amplitude of the intracardial ECG of > or = 1.4 mV was arbitrarily defined as tolerable. At amplitudes of < 1.4 mV, atrial overdrive-stimulation occurred at 400 to 800 ppm in order to convert the AF to sinus rhythm (SR). Following successful overdrive-stimulation, the atrial electrode was positioned according to standard values (P-wave > 3 mV, pacing threshold < 0.5 V at 0.5 ms). In the case of unsuccessful intraoperative atrial stimulation, the electrode was repositioned until an amplitude of > or = 1.4 mV was reached. In all cases bipolar atrial screw electrodes (Model 4068, Medtronic Inc., Minneapolis, MN, USA) were implanted. The intraoperative measurements were carried out via the atrial channel of a 5311 PSA (Medtronic Inc., Minneapolis, MN, USA). In follow-up after 6 weeks, the atrial stimulation threshold was measured in [V] at 0.5 ms and the signal amplitude of the P-wave in [mV], or in the case of AF detection with successful mode switch activation.

In 31/40 patients (77.5 %) with intraoperative persistent AF, fibrillation amplitudes of 1.4 to 3.1 mV (mean value 1.9 +/- 0.4 mV) were measured. In 9/40 patients (22.5 %) with intraoperative AF, 4 cases of conversion to SR using burst stimulation were documented. Atrial lead placement was performed using standard values. After 6 weeks, 33/40 patients (82.5 %) had SR, while intermittent AF episodes with successful mode switch activation were documented in 21 patients (52.5 %). The P-wave amplitude was 3.63 +/- 0.69 mV (range 1.8 to 4.9 mV), the atrial stimulation threshold was 1.3 +/- 0.4 mV (range 0.4 to 1.9 mV). Atrial lead adjustment due to sensing defects was not required for any patients.

The results show that all atrial leads implanted in accordance with this concept demonstrate proper sensing at SR as well as under AF, with successful mode switch episodes and acceptable stimulation thresholds.