Cross-correlation quantification of dyssynchrony: a new method for quantifying the synchrony of contraction and relaxation in the heart.

BACKGROUND Quantification of left ventricular dyssynchrony using Doppler tissue imaging may improve selection of patients who will benefit from cardiac resynchronization therapy. Most methods used to quantify dyssynchrony use a time-to-peak analysis, which is quantitatively simplistic and requires manual identification of systole and selection of peak velocities. METHODS We developed and tested a new, highly automatable dyssynchrony parameter, cross-correlation delay (XCD), that does not require identification of systole or manual selection of peak systolic velocities. XCD uses all velocity data points from 3 consecutive beats (approximately 420 points). We tested XCD on 11 members of a positive control group (responders to cardiac resynchronization therapy with a >or=15% reduction in left ventricular end-systolic volume) and 12 members of a negative control group (normal 12-lead electrocardiogram and 2-dimensional echocardiogram findings). We compared XCD to septal-to-lateral delay in time-to-peak (SLD), maximum difference in the basal 2- or 4-chamber times to peak (MaxDiff), and SD of the 12 basal and midwall times-to-peak (Ts-SD). RESULTS XCD and Ts-SD were significantly different between the positive and negative control groups (both P <or= .0001). SLD and MaxDiff demonstrated no difference between the positive and negative control groups. XCD and Ts-SD were superior to SLD and MaxDiff in discriminating between positive and negative control groups (both P < .01 by receiver operating characteristic comparison). XCD, SLD, MaxDiff, and Ts-SD demonstrated dyssynchrony in 0%, 50%, 58%, and 50% of the negative control group, respectively. XCD was the only parameter that decreased after resynchronization in the positive control group (from 160 +/- 88-69 +/- 61 milliseconds, P = .003). CONCLUSION XCD is superior to existing parameters at discriminating patients with left ventricular dyssynchrony from those with normal function.