Regional perfusion and oxygenation in the pedicled latissimus dorsi muscle flap: the effect of mobilisation and electrical stimulation

Background: The pedicled latissimus dorsi muscle flap is dependent upon an adequate blood supply via a single nutrient artery arising at its most proximal point. It has been suggested that when the latissimus dorsi muscle is used for cardiomyoplasty there is a risk of ischaemic damage to the distal regions of the flap under the additional metabolic stress of repeated electrical stimulation. Methods: A rabbit model was developed in which the latissimus dorsi muscle was raised as a pedicled flap (n=10). Needle microelectrodes were used to measure oxygenation and perfusion simultaneously in different regions of the muscle. Perfusion was measured using a gas tracer technique in which nitrous oxide was used as the marker. Muscle performance was measured by electrical stimulation of the mobilised flap. Results: The mean (standard error) perfusion of the distal muscle fell significantly from 19.5 (6.2) to 11.9 (3.8) ml. min(-1) 100 g(-1) (P < 0.05) as a consequence of mobilisation, although tissue oxygenation was maintained. Perfusion and pO(2) of the proximal regions of the flap were unchanged. During electrical stimulation perfusion increased by 72 (12)% from resting levels in the proximal region, but by only 39 (8)% in the distal muscle. Tissue pO(2) decreased during stimulation by 5.7 (1.8) mmHg proximally compared to 11.7 (3.7) mmHg distally P < 0.05). During: recovery the pO(2) remained below baseline for 24 minutes in the proximal muscle compared to 32 minutes in the distal muscle. Conclusions: Mobilisation results in a reduction in the perfusion of distal areas of the latissimus dorsi muscle flay. During repeated contraction the perfusion remains reduced and is unable to maintain tissue oxygen requirements. This has implications for dynamic applications of the latissimus dorsi muscle flap and supports the suggestion that ischaemia is the cause of distal muscle atrophy and fibrosis in cardiomyoplasty. Combined perfusion and pO(2) data provide a new insight into muscle viability studies.