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.
Denslow
S
S
The Children's Heart Center of South Carolina, Medical University of South Carolina, Charleston, South Carolina 29425, USA. denslows@musc.edu
Balaji
S
S
Hewett
K W
KW
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