The Separate Effects of Wall-Thickening and Epicardial Volume as Determinants of Left Ventricular Ejection Fraction

Abstract

Ventricular torque magically pushes systolic ejection fraction, and such torsional moments originate in the Frenet frame of a curve of cardiac muscle. Since surgical treatments involve preoperative anatomy calculations of the cardiac muscle, the understanding of chamber geometric effects may guide left ventricular chamber-reduction surgery. We decomposed ejection fraction for an interpretation of geometric parameters in restoration and optimization of cardiac function. Three systolic geometric parameters--sphericity, contractility, ventricular torsion--were extracted for the ejection fraction from an epicardial view. The decomposing approach allowed us to estimate each factor’s contribution to the total ejection fraction with the exception of the myocardium-to-chamber volume ratio, which represented the thickening effect during systole. All other effects took parts in ‘shrinkage factor’ (β), which corresponded the ejection fraction with an infinitesimal layer of muscle. Through comparing parameters for left ventricular ejection fraction, geometrical rearrangement of muscle bands for ventricular torsion is the most effective mechanical axis during partial left ventriculectomy, while ventricular shape factor only plays a less important role during systole in dilated cardiomyopathy, which often misleads the surgeon’s assessment.