Longitudinally and circumferentially directed movements of the left ventricle studied by cardiovascular magnetic resonance phase contrast velocity mapping.

Ion Codreanu,Cameron J Holloway,Bernd A Jung,Kieran Clarke,Matthew D Robson,Stephen J Golding

doi:10.1186/1532-429x-12-48

Abstract

ObjectiveUsing high resolution cardiovascular magnetic resonance (CMR), we aimed to detect new details of left ventricular (LV) systolic and diastolic function, to explain the twisting and longitudinal movements of the left ventricle.MethodsUsing CMR phase contrast velocity mapping (also called Tissue Phase Mapping) regional wall motion patterns and longitudinally and circumferentially directed movements of the left ventricle were studied using a high temporal resolution technique in healthy male subjects (n = 14, age 23 ± 3 years).ResultsPreviously undescribed systolic and diastolic motion patterns were obtained for left ventricular segments (based on the AHA segmental) and for basal, mid and apical segments. The summation of segmental motion results in a complex pattern of ventricular twisting and longitudinal motion in the normal human heart which underlies systolic and diastolic function. As viewed from the apex, the entire LV initially rotates in a counter-clockwise direction at the beginning of ventricular systole, followed by opposing clockwise rotation of the base and counter-clockwise rotation at the apex, resulting in ventricular torsion. Simultaneously, as the entire LV moves in an apical direction during systole, the base and apex move towards each other, with little net apical displacement. The reverse of these motion patterns occur in diastole.ConclusionLeft ventricular function may be a consequence of the relative orientations and moments of torque of the sub-epicardial relative to the sub-endocardial myocyte layers, with influence from tethering of the heart to adjacent structures and the directional forces associated with blood flow. Understanding the complex mechanics of the left ventricle is vital to enable these techniques to be used for the evaluation of cardiac pathology.

Highlights

Left ventricular (LV) function is geometrically and mechanically complex
By the end of isovolumetric relaxation, the entire ventricle was rotating in a counter-clockwise direction (Figure 1, arrow g), with peak rotational velocities reached from the LV base towards the apex
Ventricular repolarization was followed by a sudden drop in longitudinal shortening (Figure 5, arrow b), with a subsequent peak of longitudinal lenthening in early diastole (Figure 5, arrow c). These results demonstrate regional variations in circumferential and longitudinal motion within the left ventricular during systole and diastole. We believe this complex pattern of LV segmental motion, demonstrated using cardiac phase contrast velocity mapping, can be largely explained by the anatomical orientation of cardiomyocytes within the left ventricle and their attachments to adjacent structures

Summary

Introduction

Left ventricular (LV) function is geometrically and mechanically complex. Advances in cardiac imaging techniques have accompanied ongoing efforts to define the mechanisms of three dimensional ventricular motion [1,2,3,4,5,6,7]. The “myocardial band model” divides the myocardium into two distinct helicoids [6,7], but fails to explain the mechanisms of myocardial contraction after. Cardiovascular magnetic resonance (CMR) has allowed detailed evaluation of LV wall motion throughout the cardiac cycle, using myocardial velocity encoding techniques [13,14]. We have used results from CMR phase contrast velocity mapping with high temporal resolution, to characterise longitudinal and rotational movements of the left ventricle in healthy human subjects

Methods

Results

Conclusion