Left ventricular desynchronization assessment using global myocardial index in patients with dilated cardiomyopathy

Abstract

Global myocardial index (GMI) is a sensitive indicator of overall cardiac function. to assess the relation between GMI and currently used echocardiographic parameters of ventricular desynchronization in order to predict the value in the assessment the severity of systolic asynchrony for biventricular pacing indication. 47 patients (pts) aged 58.3±18.3 years with dilated cardiomyopathy (DCM) were analyzed. The following parameters were measured: QRS duration (QRSd); septal (S), posterior (P), lateral (L) and posterolateral (PL) wall delays, as the time from QRS onset to maximal wall contraction, and the derived parameters: left ventricular mechanical delays (LVD) as the time interval from maximal contraction between interventricular septum and posterior (LVDp), lateral (LVDl) and posterolateral wall (LVDpl), using parasternal, 4 chamber view and subcostal incidence both in time-movement and Tissue Doppler imaging (TDI). TDI measurements were performed using both color and pulsed TDI (from QRS onset to the end of S wave for each wall). 32 pts presented QRSd>120ms; evidence of significant left ventricular desynchronization with at least one LVD>70ms was found in 37 pts (7 pts with QRS<120ms); in this group GMI was significantly higher than in the rest of the pts (1.19±0.27 vs 0.74±0.17, p=0.0001). LVD was significantly higher in QRSd>120ms pts (p>0.0001 in each LVDp,1,pl). The simple regression analysis demonstrated a statistically significant linear correlation between GMI and maximal LVD in each patient (r=0.53, p<0.0001). Using a GMI > 0.87 (and QRS>120ms) as cut point, left ventricular desynchronization can be detected with a sensitivity of 94% (81%) and specificity of 70% (80%); positive predictive value was 92% (93 %), and negative predictive value was 77% (53 %). A trend toward correlation was found between GMI and QRSd (r=0.31). There was no correlation between QRSd and timing echocardiographic parameters (r<0.3 each). Regional ventricular delayed activation results in an uncoordinated and prolonged ventricular contraction with lengthening of the isovolumetric contraction and relaxation time and decrease of the time available for filling and ejection. GMI explore all this parameters and may be considered a global indicator of ventricular desynchronization.