Left ventricular function in hypertension

The evaluation of left ventricular systolic function is based on endocardia l fractional shortening measured by M mode or left ventricular ejection fra ction measured by M mode and 2D echocardiography. The interpretation of the results is difficult: fractional shortening and e jection fraction may change if the intrinsic contractility of the LV is mod ified but also when the conditions of load are different when the intrinsic contractility is unchanged. In hypertensives, the after-load may be increa sed, especially when the increased pressure is not "correctly" compensated by geometrical changes of the left ventricle (Laplace's law). Therefore, to interpret the indices of UV contractility of the hypertensive patient correctly, several approaches are possible. At the least, it is important to calculate end-systolic stress (from parame ters available from M mode recordings of the LV and systolic blood pressure ); using the values of stress, it is possible to calculate a range of norma l endocardial fractional shortening for a given patient and compare it with the measured fractional shortening. It is also useful to measure not only the endocardial but the midwall fract ional shortening because this is where the circumferential fibres which sho rten the LV short axis are found. Normal midwall fractional shortening is l ess than normal endocardial fractional shortening because the circumferenti al fibres have a relatively more epicardial than endocardial migration. For a reliable estimation of the quality of LV contraction, the best approa ch is to calculate automatically the expected theoretical endocardial and m idwall fractional shortening and to compare them with the measured values. In certain cases, it is possible to conclude that LV contractility is abnor mal despite normal endocardial fractional shortening or, on the other hand, that LV contractility is normal despite low values of fractional shortenin g.