A Statistical Technique to Assess Overall Cardiac Ventricle Contraction Dyssynchrony

Dyssynchrony between patterns of strain developed by different cardiac ventricular regions can indicate an activation abnormality or the failure of activated tissue to contract. To quantify overall chamber dyssynchrony with one number, we implemented a cross-correlation technique first developed with Doppler velocity images [1- 2], and applied the method to calculate time delays between strain (σ) waveforms of paired tissue regions [3]. We then derived one average time delay (TD avg) from all region strain pairs distributed through an image. The method acquired a long axis two-dimensional echocardiographic view from a Philips ultrasound scanner. Image acquisition was followed by strain calculation at seven adjacent regions of the myocardium by Philip's QLAB software. From each region x and y pairing, a cross-correlation function Rxy(j) = Σ
_i=0
^M-1
σx(i) * σy(i+j) between σ waveforms was assessed over M samples spanning the RR interval, and normalized time delay (TD xy) was computed based on the correlation's index of maximum (jmax). With strain measured from all seven regions of the myocardial wall, the TD xy results collected from 42 possible region pair combinations were combined to form the TD avg.