Analysis of cardiac assistance by latissimus dorsi cardiomyoplasty with a time varying elastance model.
OBJECTIVE
The clinical use of skeletal muscle cardiomyoplasty is limited because of its inadequate haemodynamic benefits. To facilitate experimental and clinical efforts to improve the efficacy of this technique, a mathematical model was proposed and its validity was tested in acute experiments.


METHODS
The model was based on the assumption that the skeletal muscle wrapped around the heart behaves as a time varying elastance that is connected in series with another time varying elastance representing the native heart. From this model two predictions were made: (1) Skeletal muscle augments the contractility of the heart by increasing the slope (Ees) of the end systolic pressure-volume relation; (2) time varying elastance of the skeletal muscle chamber (Es(t)) can be estimated from that of the assisted heart. These predictions were examined in experiments. In nine anaesthetised, open chest dogs, preconditioned latissimus dorsi muscle was transposed to wrap the heart. Left ventricular pressure (catheter tipped micromanometer), and volume (conductance catheter) were measured while reducing the preload by vena caval occlusion to evaluate Ees with 1:2 (stimulation:heart beat ratio) stimulation of the skeletal muscle.


RESULTS
With the stimulation of latissimus muscle, the end systolic pressure-volume relation was linear and Ees increased from 8.6(SEM 2.4) to 11.9(SEM 3.4) mm Hg.ml-1. Estimated Es(t) reflected the stimulation pattern and could account for the mechanism of the cardiac assistance.


CONCLUSIONS
Skeletal muscle cardiomyoplasty improved the haemodynamic variable (Ees) as predicted by a mathematical model.
Sugiura
S
S
2nd Department of Internal Medicine, School of Medicine, University of Tokyo, Japan.
Harada
K
K
Yokoyama
I
I
Momomura
S
S
Naruse
Y
Y
Maku-uchi
H
H
Serizawa
T
T
Matsunaga
H
H
Iizuka
M
M
Furuse
A
A
D000818:Animals; D001243:Assisted Circulation / Q000379:methods*; D004285:Dogs; D006321:Heart / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology* / Q000601:surgery; D006439:Hemodynamics; D008433:Mathematics; D008955:Models, Cardiovascular; D009132:Muscles / Q000637:transplantation*; D009200:Myocardial Contraction / Q000502:physiology