CHRONIC STIMULATION ENHANCES EXTRAMYOCARDIAL COLLATERAL BLOOD-FLOW AFTER A CARDIOMYOPLASTY

We have previously demonstrated that collateral blood flow can be established between skeletal muscle and myocardium in animals that have undergone a latissimus dorsi cardiomyoplasty. We have also shown that 5 minutes after the thoracodorsal nerve is electrically stimulated at 1.25 Hz, there is a sixfold increase in the collateral blood flow between the latissimus dorsi and the heart. In this experiment, we hypothesized that chronic stimulation of a latissimus dorsi cardiomyoplasty would result in a sustained increase in the latissimus-derived collateral blood flow. In 24 adult male goats, an ameroid constrictor was placed around a branch of the circumflex coronary artery, and a latissimus dorsi cardiomyoplasty was performed. After a rest period of about 1 week, the latissimus dorsi cardiomyoplasties were stimulated continuously at a 2-Hz frequency for 6 weeks. Collateral blood flow between the muscle and the heart was then measured with colored microspheres. Sixteen animals survived to the final experiment, and collaterals developed in 10. In these 10 animals, the latissimus collaterals continuously delivered 0.17 +/- 0.03 mL . g-1 . min-1 (mean +/- the standard error) of blood to ischemic myocardium. This flow represents 24.0% +/- 3.9% of the flow measured to normal myocardium. These results demonstrate that in an animal model of coronary artery disease, chronic electrical stimulation of a latissimus dorsi cardiomyoplasty maintains an elevated level of latissimus-derived collateral blood flow to the myocardium.