Cardiac assessment mechanics: 1 Left ventricular mechanomyocardiography, a new approach to the detection of diseased myocardial elements and states

Abstract

The inadequacies of currently employed methods for assessment of cardiac mechanics are discussed, and the need for development of more intrinsic assessment parameters is emphasised. To this end, a new technique is presented to enable determination of regional mechanical constitutive properties of the myocardium during diastole; this technique has been originally named left-ventricular mechanomyocardiography (or l.v.-m.m.c.g.). The data required for implementation of the techniques consist of left-ventricular sequential dynamic geometry and associated recorded chamber pressure. The method entails matching of the inner-boundary deformations of the instantaneous finite-element model of the left ventricle (which is loaded by the recorded instantaneous incremental pressure) with the actual instantaneous endocardial deformations (as derived from either cineangiocardiography or 2-dimensional echocardiography), to determine the regional distribution of the Young's modulus E_ne and the incremental stresses Δσ_ne (and hence the total stress σ_ne=∑_nΔσ_ne) of the myocardial elements. The mechanical constitutive properties of the myocardial elements can be then characterised by the constitutive relation E_ne=a+bσ. The constitutive parameters a and b have typical ranges for normal and pathological (ischaemic and infarcted) myocardial elements and hence can be employed to distinguish diseased elements. The values of a and b are calculated for normal and pathological subjects and their normal and pathological ranges are presented.