Salbutamol and the conditioning of latissimus dorsi for cardiomyoplasty.

BACKGROUND

Cardiomyoplasty is a new surgical alternative therapy for CHF. Although conditioning of muscle for cardiomyoplasty has a positive effect on fatigue resistance it also produces negative effects. In this study we assessed the effect of salbutamol, a beta2-agonist, on both the positive and the negative effects of conditioning.

METHODS

In a control group of six animals one latissimus dorsi was subject to chronic, 1 Hz, low-frequency stimulation (CLFS) while the other served as a control. The experimental group of seven dogs received a continuous SC infusion of salbutamol and one latissimus dorsi was subjected to CLFS. The other muscle demonstrated the effects of salbutamol per se. After 42 days the animals were anesthetized and fatigue resistance, muscle mass, and mechanical properties of the muscles were evaluated.

RESULTS

Salbutamol increased muscle mass, tetanic tension, and rate of rise and fall of tetanic tension. It diminished fatigue resistance and had no effect on shortening velocity. Chronic stimulation decreased muscle mass, tetanic tension, rate of rise and fall of tetanic tension, and muscle shortening velocity in both groups of dogs. Salbutamol diminished the declines in muscle mass, rate of tension development, and rate of muscle shortening due to CLFS, but did not change the effects of CLFS on tetanic tension and the rate of fall of tetanic tension. Salbutamol did not alter the increase in fatigue resistance induced by CLFS.

CONCLUSIONS

The favorable effect of CLFS on fatigue resistance was unaffected by salbutamol. The unfavorable effects of CLFS on loss of muscle mass, rate of tension development, and decline in shortening velocity were partially blocked by salbutamol, improving the ability of the latissimus dorsi to augment cardiac systole.