SUBJCETS AND METHODS: One hundred and forty patients, with CHF and left ventricular ejection fractions < or =40%, were enrolled. DTI was performed on 5-basal and 5-mid segments to assess the time from the R-wave to the peak systolic velocity (RS time). A QRS duration >130 msec, standard deviation (SD) of the RS time >40 msec, or a difference in the maximal and minimal RS times (RS time-diff) >100 msec were indicators of'Dsyn'.

RESULTS: The prevalence of myocardial Dsyn, by QRS duration, SD of the RS time and the RS time-diff were 19, 43 and 47%, respectively. The SD of the RS time (49.8±23.6 vs. 36.6±20.7, p<0.01) and the RS time-diff (139.2±63.2 vs. 98.0±54.3, p<0.01) were prolonged in the wide (>130 msec) compared with the narrow QRS group. There was also a weak positive correlation between the QRS duration and the SD of the RS time (R=0.34, p<0.001) and the RS time-diff (R=0.38, p<0.001). However, from a cross-tabulation analysis, more than one third of patients had a discrepancy between QRS duration and DTI assessed mechanical Dsyn. From a multivariate analysis, a major determinant of the SD of the RS time was the QRS duration.

CONCLUSION: Although a major determinant of the DTI assessed Dsyn was the QRS duration, more than one-third of patients had a discrepancy between electrical and mechanical Dsyn. Therefore, not only the QRS duration, but the DTI assessed Dsyn, should be measured when considering cardiac resynchronization therapy.