Twist mechanics of the left ventricle: principles and application.

Left ventricular (LV) twist or torsion represents the mean longitudinal gradient of the net difference in clockwise and counterclockwise rotation of the LV apex and base, as viewed from LV apex. Twist during ejection predominantly deforms the subendocardial fiber matrix, resulting in storage of potential energy. Subsequent recoil of twist deformation is associated with the release of restoring forces, which contributes to LV diastolic relaxation and early diastolic filling. Noninvasive techniques such as magnetic resonance imaging and echocardiography are useful for understanding LV twist dynamics in clinical settings, and data regarding their relative merits and pitfalls are rapidly accumulating. This review is a focused update on the current and evolving applications of LV twist mechanics in clinical cardiology. First, the theoretical framework for understanding the physiological sequence of LV twist during a cardiac cycle is presented. Second, variations in LV twist encountered in different experimental and clinical situations are discussed. Finally, the review presents an algorithm for routine application of LV twist in clinical differentiation of patterns of LV dysfunction encountered in day-to-day practice.