Wall thickness referenced to myocardial volume: a new noninvasive framework for cardiac mechanics.
Dimensional variables measured for study of left ventricular mechanics are subject to errors arising from difficulty in determining zero-stress dimensions for use as a reference. Based on a method validated for measurements within individuals, we have devised an approach that facilitates comparison between individuals while minimizing random scatter. We define an exact mathematical index of strain, ln(h(0)/h), using wall thickness (h) referenced to extrapolated wall thickness at zero-luminal volume (h(0)). Noninvasive data from rabbits, pigs, and humans all yielded highly similar myocardial stress, ln(h(0)/h), and work values. The stress-ln(h(0)/h) relationship during afterload 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-Starling-like curve with high correlation (r(2) = 0.96) was constructed from single points from different pigs, suggesting a low level of size and intersubject scatter. This method offers high precision for noninvasive characterization of ventricular and myocardial mechanics and for comparisons between subjects and between species.
The Children's Heart Center of South Carolina, Medical University of South Carolina, Charleston, South Carolina 29425, USA. denslows@musc.edu
S
S
Denslow
S
S
Balaji
K W
KW
Hewett
D000818:Animals; D001696:Biomechanical Phenomena; D005260:Female; D006321:Heart / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D011817:Rabbits; D013552:Swine; D013599:Systole / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology