Left ventricular rotation and twist: why should we learn?

Abstract

The left ventricle twists in systole storing potential energy and untwists (recoils) in diastole releasing the energy. Twist aids left ventricular ejection and untwist aids relaxation and ventricular filling. Therefore, rotation and torsion are important in cardiac mechanics. However, the methodology of their investigations is limited to invasive techniques or magnetic resonance imaging. With the advent of speckle tracking echocardiography, however, rotation and torsion (twist) become familiar to echocardiographers. In this review, I outline the mechanism and influencing factors of rotation and torsion with the anticipation of the routine use of these measurements in clinical practice.

Keywords: Cardiac mechanics; Myocardial fiber; Relaxation; Speckle tracking echocardiography; Torsion; Wringing.

Fig. 1

Myocardial fiber orientation and direction of rotation. Myocardial fibers in the subepicardium helically run in a left-handed direction, fibers in the mid layer run circumferentially, and fibers in the subendocardium helically run in a right-handed direction.

Fig. 2

Myocardial contraction and rotation. When myocardial fibers on the subepicardial side contract, clockwise rotational torque is produced at the base and counterclockwise rotational torque at the apex. When myocardial fibers on the subendocardial side contract, counterclockwise rotational torque is produced at the base and clockwise rotational torque at the apex.

Fig. 3

Opposite rotation at the base and apex. Subepicardial radius is larger than subendocardial radius (r2 > r1). Therefore, subepicardial rotational torque is larger than subendocardial rotational torque (R2 > R1).

Fig. 4

Tagged magnetic resonance imaging of a canine heart. Arrows at the apex mark the initial positions of two tags. By the end of isovolumic relaxation, tags have recoiled almost completely to their starting position indicating that recoil is largely an isovolumic event.

Fig. 5

Relationship between dP/dt and net twist angle.

Fig. 6

Hyper-rotation in the presence of subendocardial dysfunction. Apical rotation is shown as in Fig. 3. When there is subendocardial dysfunction, RT1' becomes smaller than RT1. Then, because of RT2 >> RT1', hyper-rotation is produced.

Fig. 7

Assessment of diastolic dysfunction based on mitral inflow, mitral annular velocity and left ventricular rotation and torsion. E: peak velocity of the early diastolic filling wave, A: peak velocity of the late diastolic filling wave, E': peak early diastolic annular velocity, A': peak late diastolic annular velocity.

Fig. 8

Relationship between left ventricular shape and torsion. Left ventricular shape is expressed by the sphericity index that is the ratio of the long-axis diameter and the short-axis diameter in end-diastole (left). A parabolic relationship is found between the sphericity index and the torsion (twist angle) (right).