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

<bold>Background: </bold>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.<bold>Objective: </bold>To determine whether distinct morphologic changes on the surface electrocardiogram indicate loss of left ventricular capture.<bold>Design: </bold>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.<bold>Setting: </bold>University hospital.<bold>Patients: </bold>54 patients with a cardiac resynchronization device and underlying left bundle-branch block.<bold>Measurements: </bold>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).<bold>Results: </bold>The sensitivity of the algorithm to correctly identify loss of left ventricular capture was 94% (95% CI, 88.2% to 97.7%), and the specificity was 93% (CI, 86.3% to 95.8%). The likelihood ratio of a positive test result was 12.8 (CI, 6.443 to 23.310), and the likelihood ratio of a negative test result was 0.06 (CI, 0.024 to 0.137).<bold>Limitations: </bold>The algorithm was tested in patients in whom the right ventricular electrode was placed in the apex of the right ventricle only.<bold>Conclusion: </bold>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. [ABSTRACT FROM AUTHOR]