Comparison of Calculations of Left Ventricular Wall Stress in Man from Thin-Walled and Thick-Walled Ellipsoidal Models

Using angiocardiographic data from 50 human subjects, a comparison was made of calculations of circumferential wall stress in the left ventricle based on the thin-walled ellipsoidal model of Sandler and Dodge and the thick-walled ellipsoidal model of Wong and Rautaharju. The Sandler and Dodge formula consistently overestimated mean stress as determined from the Wong and Rautaharju model. The degree of overestimation in terms of percent error usually varied between 5% and 15% and overall averaged about 10% at endsystole as well as at end-diastole. Analysis of the various factors influencing the discrepancy between calculations indicated that the expected increase in error associated with an increase in wall thickness during systole tended to be mitigated by a concomitant change in chamber geometry, specifically, an increase in the ratio of major to minor semiaxis. This study, then, offers an estimate of the error introduced by employing the Sandler and Dodge or similar thin-walled ellipsoidal models for computation of mean circumferential stress.