Physiologic Determinants of Left Ventricular Systolic Torsion Assessed by Speckle Tracking Echocardiography in Healthy Subjects

BACKGROUND: The associations of left ventricular (LV) systolic torsion with clinical and echocardiographic variables in physiological conditions have not been fully investigated. We explored the independent determinants of LV systolic torsion in a population of normal subjects. METHODS: In 119 healthy subjects, peak twist angle (LVtw) and torsion (LVtor) during ejection, and the QRS-LVtw interval (time-to-peak LVtw) were measured by speckle tracking. LV twisting rate and rotational deformation delay were also determined. RESULTS: Stepwise multiple regression showed that LVtw was independently associated with indexed end-systolic volume (β=-0.200, P < 0.0001), peak early diastolic mitral annulus velocity (β=-0.186, P = 0.0001), heart rate (β= 0.178, P = 0.0003), and male gender (β=-0.174, P = 0.0004). Similar results were found for LVtor. Age was the only parameter, which has demonstrated an independent correlation with time-to-peak LVtw (β= 0.329, P < 0.0001). Despite significance of these associations, the proportions of variability explained by regression models were relatively low (range 11-26%), and no accurate predictive models were identifiable for LV twisting rate and rotational deformation delay. CONCLUSION: In normal individuals, indexed end-systolic LV volume, LV relaxation, heart rate, gender, and age correlate independently with LV torsion mechanics. However, conventional echocardiographic and clinical variables are not able to predict LV torsion mechanics.