Author + information
- Received August 2, 1989
- Revision received October 13, 1989
- Accepted October 26, 1989
- Published online March 15, 1990.
- Israel Mirsky, PhD, FACC∗,a,b,
- Teruhiko Aoyagi, MDa,b,
- Valerie Marion Crocker, MSa,b and
- Alan M. Fujii, MDa,b,1
- ↵∗Address for reprints: Israel Mirsky, PhD, Brigham and Women's Hospital, 75 Francis Street, Boston, Massachusetts 02115.
Employing the new concept of systolic myocardial stiffness, this study addresses the questions of linearity of the end-systolic stress-strain relations in left ventricular hypertrophy and the preload dependence of fiber shortening rate. Pressure overload hypertrophy was induced in six puppies by banding the ascending aorta. Ultrasonic crystals were implanted for measurement of short axis and wall thickness in the six dogs with hypertrophy and in five control dogs. A pressure catheter was inserted through the apex for left ventricular pressure measurement. Load was altered by graded infusions of phenylephrine in the setting of betaadrenergic blockade.
Linearity of the end-systolic stress-strain relations was observed in all cases, and preload-corrected shortening rate-afterload relations were derived from these stress-strain relations. Without preload correction, mid wall and endocardial shortening rate were depressed (p < 0.05 and p < 0.005, respectively) in the hypertrophy group. However, with preload correction at 35 g/cm2, there was no significant difference in shortening rate between the control and hypertrophy groups at afterloads of 150, 200 and 250 g/cm2. Endocardial shortening rate at a preload of 25 versus 35 g/cm2demonstrated a preload dependence in both the control (p < 0.04) and the hypertrophy group (p < 0.01). Mid wall shortening rate displayed a preload dependence only in the hypertrophy group (p < 0.05).
It is concluded that end-systolic stress-strain relations are linear in control conditions and in hypertrophy, fiber shortening rate is preload-dependent and, thus, shortening rate-afterload relations currently used to assess myocardial contractility need to be modified to account for these preload effects.
↵1 Dr. Fujii's current address is The Children's Hospital, Boston, Massachusetts.
☆ This work was supported by Grants HL 34596 and BRSG S07 RR 05950-05 from the National Heart, Lung, and Blood Institute. National Institutes of Health Bethesda, Maryland.
- Received August 2, 1989.
- Revision received October 13, 1989.
- Accepted October 26, 1989.