Atrial synchronous ventricular pacing with a single lead: reliability of atrial sensing during physical activities, and long-term stability of atrial sensing.

A VDD pacing system with bipolar single-pass leads, were implanted in 36 consecutive patients (average age 72 +/- 2 years) with high degree atrioventricular block and normal sinus node function. At implant the atrial signal amplitude was 2.6 +/- 0.2 mV measured by a pacing system analyser (PSA), 1.8 +/- 0.1 mV measured peak-to-peak from the telemetered calibrated electrogram, and 1.3 +/- 0.1 mV measured from the sensing threshold. At one month follow-up the peak-to-peak amplitudes (mV) of the telemetered atrial electrograms were not significantly different measured continuously during resting supine with quiet breathing (1.4 +/- 0.1), sitting (1.6 +/- 0.2), standing (1.5 +/- 0.1), arm swinging (1.4 +/- 0.2), hyperventilation (1.3 +/- 0.1), Valsalva manoeuvre (1.4 +/- 0.1), and treadmill exercise (1.9 +/- 0.6). The telemetered atrial electrogram amplitude and the atrial sensing threshold varied between 1.2 +/- 0.09 mV and 1.8 +/- 0.1 mV, and between 0.95 +/- 0.07 mV and 1.3 +/- 0.01 mV, respectively at 0.5, 1, 3, 6 and 12 months follow-up, but the changes were statistically non-significant. The Event Summary showed sensing of 98% to 99% of the atrial events at the different follow-up periods.