title: End-systolic myocardial stiffness is a load-independent index of contractility in stage 24 chick embryonic heart.
abstract: Cardiac morphogenesis and function are interrelated during cardiovascular development. We evaluated the effects of acute alteration of loading condition to chick embryonic ventricular contractility using end-systolic myocardial stiffness based on the incremental elastic modulus concept. End-systolic stress-strain relations including geometric factor and end-systolic myocardial stiffness were determined from the simultaneous measurement of ventricular pressure and chamber dimension in the following four groups of stage 24 White Leghorn chick embryos: volume infusion (n = 9), conotruncal occlusion (n = 9), calcium suffusion (n = 10), and verapamil suffusion (n = 8). The end-systolic stress-strain relationship was linear in each embryo. There was no correlation between end-systolic myocardial stiffness and end-systolic stress. End-systolic myocardial stiffness increased with calcium suffusion (P < 0.05 vs. volume infusion). The geometric factor increased after verapamil suffusion (P < 0.05). End-systolic myocardial stiffness normalized by geometric factor was not changed by alteration of preload or afterload, increased after calcium suffusion, and decreased after verapamil administration (P < 0.05). These results suggest that normalized end-systolic myocardial stiffness is a load-independent index of ventricular contractility in the developing embryonic chick ventricle.
authors.affiliation: Division of Pediatric Cardiology, Department of Pediatrics, University of Kentucky, Lexington, Kentucky 40536-0298, USA. ktobi0@pop.uky.edu
authors.forename: K
authors.initials: K
authors.lastname: Tobita
authors.forename: B B
authors.initials: BB
authors.lastname: Keller
mesh_terms: D000818:Animals; D002642:Chick Embryo / Q000502:physiology; D004548:Elasticity; D006321:Heart / Q000196:embryology*; D006439:Hemodynamics / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology*; D013314:Stress, Mechanical; D013599:Systole