Outer contour and radial changes of the cardiac left ventricle: a magnetic resonance imaging study

Earlier studies have shown a +/-5% end-systolic decrease in the volume encompassed by the pericardial sack, manifesting as a radial diminution of the pericardial/epicardial contour of the left ventricle (LV). The aim of this study was to measure this radial displacement at different segmental levels of the LV and try to find out were it is as greatest and to calculate regional myocardial volume changes as a reference in healthy subjects. Eleven healthy subjects were examined by magnetic resonance imaging. Images were acquired using an ECG-triggered balanced fast field echo pulse sequence. The epicardial borders of the LV wall were delineated in end-diastole (ED) and end-systole (ES). Regional changes of the LV wall were analysed at three different levels (base, mid and apex) by dividing the myocardium into segments. The volumes obtained as the differences between the outer volume of the left ventricle at ED and ES at different slice levels were found to be greatest at the base of the heart and lowest at apex. The relative inward motion, that is the motion in short-axis direction of the epicardial border of the myocardium from ED to ES towards the centre of the LV, was greatest at the base and lowest at the mid level, something that has to be taken into account when measuring the LV during clinical exams. There was a significant difference in the relative inward motion between the segments at apex (p < 0.0001), mid (p = 0.036) and at base level (p < 0.0001).