RELATION OF LEFT-VENTRICULAR LONGITUDINAL AND CIRCUMFERENTIAL SHORTENING TO EJECTION FRACTION IN THE PRESENCE OR IN THE ABSENCE OF MILD HYPERTENSION

Objectives To study left ventricular longitudinal shortening in arteri al hypertension and the relative contribution of longitudinal and circ umferential fiber shortening to ventricular ejection. Methods Two-dime nsional and M-mode echocardiograms were obtained for 50 normotensive s ubjects (aged 49 +/- 12 years) and 50 never-treated mild hypertensive patients (aged 49 +/- 11 years), to measure the minor-axis endocardial and midwall shortening, long-axis shortening and ejection fraction, R esults The midwall shortening was lower in hypertensive than:it was in normotensive subjects (P< 0.001) and was related inversely to the cir cumferential wall stress for both groups (P< 0.04 and 0.0001, respecti vely). The long-axis shortening in hypertensive patients (22.2 +/- 4.2 %) and in normotensives (23.6 +/- 5.4%) was not statistically differen t, and was not related either to the meridional or to the circumferent ial wall stress, The ejection fraction was also similar for the two gr oups (68.2 +/- 6.3 versus 68.6 +/- 5.6%). Both for normotensive and fo r hypertensive subjects, the ejection fraction was influenced mainly b y the midwall shortening (61 and 40% of the variance for normal and hy pertensive individuals, respectively), with a minor contribution from the long-axis shortening, which was 7% for normotensive subjects and 1 8% for hypertensive patients, a statistically significant difference ( P < 0.001), The combined effect of midwall and longitudinal shortening s on the ejection fraction was regulated by the relative wall thicknes s, and was maximal for hypertensive patients with an ejection fraction greater than that predicted by the midwall shortening Conclusions Lef t ventricular ejection is produced principally by circumferential shor tening and is related independently to the relative wall thickness. In the presence of arterial hypertension and an altered cardiac toad, lo ngitudinal shortening becomes an important mechanism by which to augme nt ejection, thereby offsetting the reduction in midwall shortening.