An electrocardiogram-based algorithm to detect loss of left ventricular capture during cardiac resynchronization therapy.

Background: Loss of left ventricular capture in patients with cardiac resynchronization devices may account for worsening heart failure and can be difficult to diagnose without a programmer. Objective: To determine whether distinct morphologic changes on the surface electrocardiogram indicate loss of left ventricular capture. Design: After analysis of the R-S spike ratio in the 12-lead electrocardiogram during right ventricular and biventricular pacing in 10 patients, an algorithm to detect loss of left ventricular capture was developed. Setting: University hospital. Patients: 54 patients with a cardiac resynchronization device and underlying left bundle-branch block. Measurements: Leads V1 and I of a 12-lead electrocardiogram were assessed after biventricular pacing was confirmed and after the device was programmed to right ventricular pacing only (simulating loss of left ventricular capture). Results: The sensitivity of the algorithm to correctly identify loss of left ventricular capture was 94% (95% Cl, 88.2% to 97.7%), and the specificity was 93% (Cl, 86.3% to 95.8%). The likelihood ratio of a positive test result was 12.8 (Cl, 6.443 to 23.310), and the likelihood ratio of a negative test result was 0.06 (Cl, 0.024 to 0.137). Limitations: The algorithm was tested in patients in whom the right ventricular electrode was placed in the apex of the right ventricle only. Conclusion: Presence of biventricular capture-the prerequisite for successful cardiac resynchronization therapy-and loss of left ventricular capture can be accurately detected by an algorithm based on analysis of the R-S ratio on leads V1 and I of the surface electrocardiogram.