Dogs with left ventricular hypertrophy from long-standing volume overload functioned at a higher point on the ascending limb of the length-tension curve (76% Lmax vs 61% Lmax in normals).
Does long-standing volume overload alter the contractile state and length-tension relationship of the hypertrophied left ventricle in dogs?
In a canine model of long-standing volume overload, left ventricular adaptation is achieved through hypertrophy and a shift up the length-tension curve without depressing the intrinsic inotropic state.
Absolute Event Rate: 76% vs 61%
The purpose of this investigation was to evaluate the contribution of hypertrophy, the length-tension phenomenon, and inotropism to adaptation of the left ventricle (LV) to volume overload of up to 3 yr duration. Overload was produced in dogs by heart block, and contractile state was evaluated with a Walton-Brodie arch. Recording of contractile force (CF) in grams vs. muscle length from the LV indicated that dogs with hypertrophy were functioning at a higher point on the ascending limb of the length-tension curve than normals (76 percent Lmax in hypertrophy vs. 61 percent Lmax in normal). Additionally, in hypertrophy, all points on the length-tension curve above 80 percent Lmax were significantly elevated. None of these changes were seen in dogs in which block was induced on the day of the experiment. When CF was normalized for hypertrophy and expressed as CF/cm2, the length-tension curves were practically superimposable. These data suggest that adaptation was accomplished by hypertrophy, a shift up the length-tension curve without a depression of inotropic state.
Walter H. Newman (Sun,) conducted a other in Left ventricular hypertrophy from volume overload. Long-standing volume overload (hypertrophy) vs. Normal dogs and dogs with acute heart block was evaluated on Contractile force vs. muscle length (percent Lmax). Dogs with left ventricular hypertrophy from long-standing volume overload functioned at a higher point on the ascending limb of the length-tension curve (76% Lmax vs 61% Lmax in normals).