Left ventricular twist angle: echocardiographic assessment of amplitude and timing in normal and disease conditions

Abstract

Purpose: The current concept of myocardial function incorporates complex rotational mechanics. Speckle Tracking Echocardiography (STE) allows for left ventricular (LV) twist deformation assessment, but quantitative data are often variable and little is known of torsional timing. The aim was to evaluate the LV twist angle and sequence of rotation in severe systolic dysfunction, less pronounced disease and in normal conditions. Methods: 101 subjects were studied (mean age 48.1±15 years, 46% women). Of these, 33 patients (PTS) demonstrated severe LV systolic dysfunction with EF ranging from 14 to 34%, mean 26.7% (Group 3); 33 PTS showed LV EF ranging from 37 to 69%, mean 55.5% (Group 2); and 35 subjects were healthy volunteers with EF between 62 and 67%, mean 65.2% (Group 1). Concurrent net LV twist angle was calculated using two-dimensional STE short axis images as the absolute apex-to-base difference in LV rotation at time of aortic valve closure (AVC). Time to peak apical and basal rotation was also measured as well as AVC independent peak LV twist angle, indicating the maximal torsional deformation without isochronal occurrence. Results: LV twist angle at AVC was significantly lowest in Group 3, showing a mean value of 5.6±5.0° (p<0.001), but no difference was found between Group 1 and 2, with measurements of 13.3±4.7° and 16.1±6.3°, respectively. In general, peak rotation was different from the values measured at AVC and did not occur simultaneously at basal and apical level. Therefore, LV twist angle at AVC was lower than peak twist angle in 96% of subjects. However, both measurements showed good correlation, with coefficients of 0.87, 0.9 and 0.87 in Group 3, 2 and 1, respectively. The absolute difference between time to peak apical and basal rotation was significantly larger in Group 3 as compared to Group 1, showing mean values of 96.8±81.2 ms and 44.3±41.0 ms, respectively (p=0.01). Conclusions: LV twist angle at aortic valve closure shows significant decrease in patients with severe LV systolic dysfunction, but due to a potential compensatory mechanism is comparable between patients with less pronounced disease and healthy subjects. Measurements of LV twist angle at aortic valve closure and at maximal amplitude show good correlation, though there is a temporal gradient of LV peak rotation between basal and apical level. This absolute timing difference is larger in patients with severe LV systolic dysfunction as compared to healthy subjects.