The aims of the proposed research program are (a) to develop a mathematical model describing the mechanical behaviour of aneurysms, (b) to write a review paper on the assessment of passive elastic stiffness of isolated and intact heart muscle and (c) to conduct pilot studies in relation to noninvasive methods of assessing cardiac function employing the displacement cardiograph. A spherical model is assumed for the mechanical behaviour of left ventricular aneurysms and furthermore, we assume that early after the infarction, a fluid layer separates the endocardial and epicardial layers in the infarcted zone. Elastic-stiffness -stress relations are to be evaluated in the infarcted and noninfarcted regions and stress factors in the normal and infarcted zones will be computed for various angles of damage. This model should provide a basis for estimating infarct size and may also provide a means for predicting whether or not an infarct develops into an aneurysm. Several important conclusions can be drawn from the review studies on elastic stiffness of heart muscle: (i) elastic stiffness of muscle per se can indeed be assessed from pressure-volume data and LV wall mass. (ii) the degree of muscle stiffness is represented by the slope of the linear stiffness-stress relation. (iii) stiffness constants tend to be normal in volume overload muscle but elevated in pressure overload muscle. (iv) animal studies indicate that age-stiffness relations are species dependent. (v) simple indices dP/dV etc. do not quantitate muscle stiffness but do quantitate ventricular stiffness. Systolic time intervals can be recorded with the displacement cardiograph. BIBLIOGRAPHIC REFERENCES: Mirsky, I., Janz, R.F., Kubert, B.R., Korecky, B., Taichman, G.C. Passive elastic wall stiffness of the left ventricle: A comparison between linear theory and large deformation theory. Bull. Math. Biology 38: 219, 1976. Janz, R.F., Kubert, B.R., Mirsky, I., Korecky, B., Taichman, G.C. The effect of age on passive elastic stiffness of rat heart muscle. Biophysical J. 16: 281, 1976.
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