An algorithm for verifying biventricular capture based on evoked-response morphology

Cardiac resynchronization therapy relies on consistent beat-by-beat myocardial capture in both ventricles. A pacemaker ensuring right (RV) and left ventricular (LV) capture through reliable capture verification and automatic output adjustment would contribute to patients' safety and quality of life. We studied the feasibility of an algorithm based on evoked-response (ER) morphology for capture verification in both the ventricles. RV and LV ER signals were recorded in 20 patients (mean age 72.5 years, range 64.3-80.4 years, 4 females and 16 males) during implantation of biventricular (BiV) pacing systems. Leads of several manufacturers were tested. Pacing and intracardiac electrogram (IEGM) recording were performed using an external pulse generator. IEGM and surface-lead electrocardiogram (ECG) signals were recorded under different pacing conditions for 10 seconds each: RV pacing only, LV pacing only, and BiV pacing with several interventricular delays. Based on morphology characteristics, ERs were classified manually for capture and failure to capture, and the validity of the classification was assessed by reference to the ECG. A total of 3,401 LV- and 3,345 RV-paced events were examined. In the RV and LV, the sensitivities of the algorithm were 95.6% and 96.1% in the RV and LV, respectively, and the corresponding specificities were 91.4% and 95.2%, respectively. The lower sensitivity in the RV was attributed to signal blanking in both channels during BiV pacing with a nonzero interventricular delay. The analysis revealed that the algorithm for identifying capture and failure to capture based on the ER-signal morphology was safe and effective in each ventricle with all leads tested in the study.