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Factors influencing the contribution of myocardial laminar sheets to ventricular wall thickening
Author(s) -
Coppola Benjamin,
Covell James,
Omens Jeffrey
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.970.13
Subject(s) - thickening , ventricle , systole , diastole , afterload , laminar flow , cardiology , dilatant , anatomy , medicine , materials science , composite material , blood pressure , physics , mechanics , polymer science
The myocardium is composed of laminar sheets of myofibers (oriented at angle β from radial), which shear during systole and account for >50% of wall thickening (E 33 ). The sheet strains (E ss , E nn , E sn ) are related to wall thickening by E 33 = E ss *cos 2 β + E nn *sin 2 β + 2*E sn *cosβ*sinβ. We hypothesized that the contribution of each term to wall thickening was determined primarily by anatomic structure, and independent of load. To test this hypothesis, we imaged transmural columns of beads implanted into the left ventricle of open‐chest dogs (n=15) using biplane cineradiography. Strains were expressed in terms of a histologically measured fiber‐sheet coordinate system. At 20% depth, the sheet extension (E ss ) term was the primary contributor to end‐systolic wall thickening, with an average of 68%. At 52 and 81% depths, the sheet shear (E sn ) term was the predominant factor, contributing 49 and 48% respectively. This transmural trend held during diastolic wall thinning (EDP from 3 to 18 mmHg), with E ss term = 78%, and E sn term = 79 and 127% corresponding to the 3 depths. Increasing afterload (LV pressure from 119 to 169 mmHg) also gave a similar transmural result. We conclude that the transmural deformation of the myocardial wall is a property of the local anatomical orientation, with laminar structures contribution similarly during diastole and systole with varying loads. Supported by NIH grant HL32583.