Observation and basis of improved blood flow to the distal latissimus dorsi muscle: a case for electrical stimulation prior to grafting.

Abstract

Dynamic cardiomyoplasty, using a functional graft of the latissimus dorsi muscle, has shown promise as a treatment for selected patients with advanced heart failure. The success of this approach depends on maintaining the viability of the muscle, whose distal portion is susceptible to ischaemic damage. We investigated the effects of surgical mobilization on regional muscle blood flow and the influence of electrical stimulation of the muscle. Ten sheep were randomly assigned to two equal groups. In one group, the latissimus dorsi muscle was stimulated continuously in situ at 2 Hz for two weeks; in the other group, the muscle was not stimulated. Regional blood flows in the muscles were determined by a fluorescent microsphere technique. Serial measurements were made (a) under baseline conditions before intervention, (b) with the thoracodorsal artery occluded and (c) after interruption of the perforating collateral arteries. Surgical mobilization of the unstimulated latissimus dorsi muscles had little effect on blood flow in the proximal region, which remained at 93.1 +/- 16.9% of baseline (mean +/- SEM). The distal region was rendered significantly more ischaemic (55.8 +/- 13.5% of baseline, p < 0.002 compared to the proximal region). Electrical prestimulation abolished any significant proximodistal gradient in blood flow and improved distal muscle perfusion following mobilization (proximal vs. distal: 75.0 +/- 8.8 vs. 63.0 +/- 10.9%; p > 0.4). Distal muscle ischaemia occurred when the entire latissimus dorsi muscle was acutely elevated on the thoracodorsal pedicle alone. Electrical prestimulation of the muscle in situ improved the thoracodorsal perfusion of the distal muscle by abolishing the proximal-to-distal gradient in flow, with a substantial benefit to distal flow after mobilization. Although electrical stimulation is known to induce vascular proliferation, we argue that this effect of stimulation is brought about mainly by enhancement of the flow through anastomotic connections between proximal and distal arterial territories.