Ultrasound in the assessment of left ventricular performance
Echocardiography provides a noninvasive technique to evaluate dynamic cardiac anatomy. Thus, echocardiography provides a method for obtaining standard measurements reflecting cardiac performances such as left ventricular cavitary size and wall motion, and additionally enables the evaluation of relatively unique data such as wall thickness and wall thickening during systole. Therefore, ultrasound has been used for the evaluation of left ventricular performance almost from the first introduction of M-mode echocardiography. The recent development of two-dimensional or cross-sectional echocardiography has overcome some of the limitations of M-mode echo in the evaluation of left ventricular performance and further expanded the role of ultrasound in this area.
Various measurements have been obtained from M-mode echocardiograms of the heart in the evaluation of left ventricular performance. The intracavitary dimension or diameter of the left ventricle may be readily recorded by ultrasound in both systole and diastole, and has been shown to be an accurate reflection of the ventricular area measured. Subsequently, one may utilize the single dimensional, left ventricular internal diameter measurement to extrapolate mathematically an estimation of left ventricular volume in either systole or diastole, thereby enabling deductions regarding stroke volume and ejection fraction of this chamber. Unfortunately, although such extrapolations have been shown to provide reasonable estimates of actual left ventricular volumes in the presence of ventricles of normal geometry, distortions of left ventricular shape by either coronary disease or ventricular dilation invalidate the estimation of ventricular volumes by M-mode. Further, the presence of segmental left ventricular disease may be missed by M-mode . . .