Echocardiographic assessment of left ventricular function. With special reference to normalized velocities
The concept of 'normalized velocity' has been applied in this study to the echocardiographic (echo) assessment of left ventricular (LV) function in 87 patients. The following normalized velocities were calculated from the ultrasound recording of LV wall motion: the mean circumferential fiber shortening rate [mean V (CF)]; the mean normalized posterior wall velocity [V (PW)]; and the mean normalized interventricular septal velocity [V (IVS)]. Systolic ejection fraction (SEF), and mean (non normalized) posterior wall velocity (PWV) were also determined. There were 19 patients with normal LV function, 5 with atrial septal defect (mean V (CF), V (IVS) and SEF were not calculated in these patients), 16 with LV volume overload, 29 with myocardial disease, 6 with hypertrophic cardiomyopathy and 12 with coronary artery disease (CAD). Single plane cineangiographic (angio) determinations of mean V (CF) and SEF were obtained in 50 of the 87 patients (including all 12 patients with CAD). Mean V (CF) and SEF done by echo correlated very well with mean V (CF) and SEF done by angio in the patients without CAD (r = 0.94 and 0.91, respectively). Mean V (CF) (by echo or by angio) adequately separated normal from abnormal LV function. Although correlation between mean V (CF) and SEF was good, mean V (CF) was reduced while SEF was well preserved in several patients. In spite of LV asynergy, most of the patients with CAD had good correlation between echo and angio measurements of mean V (CF) and SEF. Although PWV correlated with echo and angio mean V (CF) in the patients without CAD, the overlap of normal and abnormal values made PWV an unreliable index of LV function. In contrast, V (PW) proved to be a reliable indicator of LV performance in patients without LV asynergy. Agreement between V (PW) and mean V (CF) (by echo or angio) was seen in 94% of the patients; in the presence of CAD, however, greater discrepancy was seen between these two measurements. Agreement between V (IVS) and V (PW) was present in 90% of the patients without CAD, but in only 58% of the patients with CAD. The analysis of LV wall motion by echocardiography utilizing the 'normalized velocity' concept appears to be a rational and practical method for evaluation of LV performance. In the absence of asynergy, V (PW) provides a reliable index of LV performance which may be of particular value when abnormal septal motion precludes the determination of SEF and mean V (CF). In the presence of asynergy, however, mean V (CF), V (PW) and V (IVS) may reflect only the performance of the visualized segment of myocardium.