Novel electrocardiographic dyssynchrony criteria improve patient selection for cardiac resynchronization therapy

We hypothesized that the greater the intra- or interventricular dyssynchrony (intraD, interD), the more effective cardiac resynchronization therapy (CRT) is. We sought to improve patient selection for CRT by using novel ECG dyssynchrony criteria.

Left ventricular (LV) intraD was estimated by the absolute time difference between the intrinsicoid deflections (ID) in leads aVL and aVF divided by the QRS duration (QRSd): [aVLID − aVFID]/QRSd (%). InterD was estimated from the formula: [V₅ID − V₁ID]/QRSd (%). Their >25% value indicated electrical dyssynchrony present (ED+) and ≤25% value electrical dyssynchrony absent (ED−) diagnoses. Using the intraD + interD criteria (intra + interDC) together, if at least one of them indicated ED+ diagnosis, a final ED+ diagnosis, if both indicated ED− diagnosis, a final ED− diagnosis was made. Two authors, blinded to CRT response, retrospectively analysed pre-CRT ECGs of 124 patients with known CRT outcome. CRT response was defined as improvement of ≥ 1 NYHA class, being alive and having no hospitalizations for heart failure during 6 months of follow-up. 35/124 (28%) patients were non-responders (NRs), using the traditional criteria (TC) correct diagnosis was made in the remaining 89/124 (72%) responder (R) cases. The test accuracy (TA) of intra + interDC + TC [100/124 (81%), P < 0.001] was superior to that of TC [89/124 (72%)] due to its superior TA [36/43 (84%) vs. 29/43 (67%), respectively, P = 0.0156] in the non-specific intra-ventricular conduction disturbance (NICD) subgroup [43/124 (35%)]. In the left bundle branch block subgroup [70/124 (56%)] there was no between-criteria difference in TA.

The intra + interDC + TC predicts clinical response after CRT more accurately than TC alone, due to greater TA in the NICD subgroup.