Clinical validation of new pacing-sensing configurations for atrial automatic capture verification in pacemakers

Atrial Automatic Pacing Capture Verification. Introduction: This study evaluated an atrial automatic capture verification scheme based on atrial evoked response (AER). Atrial pacing was between At,p and Can (A(tip)-Can) using different coupling capacitances (CCs). Independent pairs of sensing electrodes between A(ring) and V-tip (A(ring)-V-tip) or between A(ring) and a separate indifferent electrode (A(ring)-Indiff) were used to reduce pacing-induced afterpotentials. Methods and Results: A custom-made external pacing system was used to perform automatic step-up and step-down pacing (0.1 to 7.1 V at 0.5 msec, step size of 0.1 V) using different CCs (2 or 15 muF). Intracardiac signals from A(ring)-Indiff and A(ring)-V-tip were independently recorded and analyzed both in real time and off-line to detect AER. Every paced beat also was visually inspected and compared with surface ECG to verify the captures. With the intracardiac signals properly filtered, AER detection was based on the signal within a window of 12 to 65 msec after the stimulus. Data from 27 patients (4 chronic and 23 acute implantations; age 65.6 +/- 13.9 years) were analyzed. Bipolar atrial lead measurements using a standard pacing system analyzer were as follows (mean +/- SD): impedance 695 +/- 227 Omega, P wave amplitude 4.2 +/-2.3 mV, slew rate 1.1 +/-0.9 V/sec, and pacing threshold at 0.5 msec 1.0 +/-0.5 V. The results with CC = 2 muF showed that of 9,500 atrial paced beats, correct capture verification rates were 99.8% (A(ring)-Indiff) and 99.4% (A(ring)-V-tip)- Similar results were achieved with CC = 15 muF (99.7% and 99.5%, respectively). Conclusion: AER can be reliably detected using independent pacing (A(tip)-Can) and sensing (A(ring)-V-tip or A(ring)-Indiff) electrodes. Therefore, atrial automatic capture verification by AER detection is feasible.