Relationship between global myocardial index and automatic left ventricular border detection pattern to identify biventricular pacing candidates.

Objective Of The Study: to evaluate the relation between global myocardial index (GMI) and the pattern of left ventricular (LV) volume curves variation, using automatic border detection (ABD), and their role in assessing LV asynchrony.

Methods: We studied 52 patients (mean age = 55 +/- 17 years) with dilated cardiomyopathy. QRS duration (QRSd) and GMI were measured. Currently accepted TDI and M-mode parameters were used to indicate LV dyssynchrony. On-line continuous LV volume changes were recorded using ABD. Ejection time (ET ABD) was measured from the ABD wave-forms as time interval between maximal and minimal volume variation during LV electromechanical systole. We derived the ejection time index (ETiABD) as the ratio between ET ABD and RR interval (ETiABD = ET/RR).

Results: 31 patients had a QRSd > 120 ms and 21 patients had a QRSd < 120 ms. Ventricular dyssynchrony was observed in 39 patients (29 patients had a QRSd > 120 ms). GMI was significantly higher in patients with, than in patients without ventricular dyssynchrony (1.06 +/- 0.18 vs 0.73 +/- 0.13, P = 0.0001), while ETABD was significantly smaller (233 +/- 39 ms vs 321 +/- 28 ms, P = 0.0001). The corresponding difference for ETiABD was 26.9 +/- 6.8% vs 6.3 +/- 4%, P < 0.0001. By simple regression analysis an inverse linear correlation was observed between GMI and ETiABD (r(2) = -0.51, P < 0.0001). The pattern of ABD waveforms showed increased isovolumic contraction and relaxation times in patients with LV asynchrony, similar to the GMI pattern.

Conclusions: Regional delays in ventricular activation cause uncoordinated and prolonged ventricular contractions, with lengthening of the isovolumic contraction and relaxation times and shortening of the time available for filling and ejection. GMI explores these parameters and together with ABD might be useful to identify patients with ventricular asynchrony.