Wall thickness referenced to myocardial volume: a new noninvasive framework for cardiac mechanics

Wall thickness referenced to myocardial volume: a new noninvasive framework for cardiac mechanics. J. Appl. Physiol. 87(1). 211-221, 1999. -Dimensiona l variables measured for study of left ventricular mechanics are subject to errors arising from difficulty in determining zero-stress dimensions for u se as a reference. Based on a method validated for measurements within. ind ividuals, we have devised an approach that facilitates comparison between i ndividuals while minimizing random scatter. We define an exact mathematical index of strain, In(h(0)/h), using wall thickness (h) referenced to extrap olated wall thickness at zero-luminal volume (h(0)). Noninvasive data from rabbits, pigs, and humans all yielded highly similar myocardial stress, In( h(0)/h), and work values. The stress-ln(h(0)/h) relationship during afterlo ad variation was constant among individual pigs with a twofold variation in ventricular mass. Stress-ln(h(0)/h) data from our analysis displayed lower scatter than either pressure-volume data normalized to myocardial mass or stress-ln(h(0)/h) data referenced to end-diastolic dimensions. A Frank-Star ling-like curve with high correlation (r(2) = 0.96) was constructed from si ngle points from different pigs, suggesting a low level of size and intersu bject scatter. This method offers high precision for noninvasive characteri zation of ventricular and myocardial mechanics and for comparisons between subjects and between species.