4D left ventricular resultant wall motion and blood flow assessed by phase-shift velocity mapping at high-field 3T MRI.

Abstract

Contractility and elasticity of the myocardium are important variables for detecting anomalies that may influence pump function. It is important to assess both wall motion and blood flow to detect regional left ventricular (LV) dysfunction and abnormal flow patterns. This study discusses four-dimensional (4D) phase-contrast magnetic resonance imaging (MRI) for simultaneous quantification and visualization of LV wall motion and blood flow. In thirteen healthy subjects, a three-directional retrospective cardiac triggered phase-shift velocity mapping technique was used to acquire velocity data of the LV throughout the cardiac cycle. All short-axis slices of the LV wall were segmented in six sectors of 60° starting from the anterior hinge point between the right and left ventricles, from base to apex. Velocity data in resultant, radial, circumferential and longitudinal directions were calculated and presented as coloured three-directional vectors. Our findings showed a reduction in maximum wall velocities from base to apex, whereas for the radial and circumferential directions no significant differences were noted (13·1±2·7 and 13·0±2·9cms-1 , respectively. P=0·9). The longitudinal maximum velocities (21·0±0·6cms-1 ) were significantly higher than the radial and circumferential components (P=0·002). We found that the inclination angle of the resultant blood flow was changed towards the left ventricular outflow tract during systole. Using this 4D MRI velocity mapping technique, we present an improved method for quantification and visualization of ventricular wall velocities in the radial, circumferential and longitudinal directions, as well as for the intracavity blood flow.