Vascular resistance in human muscle flaps

Important differences in free muscle flap survival have been reported in th e setting of long arterial and venous vein grafts. The authors provide insi ght into the etiology of flap failure by addressing the following question: Do differences in flap type result in clinically significant different vas cular resistances and consequently anastomotic patency? A total of 15 human flaps were studied intraoperatively: 9 gracilis, 3 rectus abdominis, and 3 latissimus dorsi. The muscle was isolated on a single pedicle and hemodyna mic stability was ensured. The venous pedicle was then divided. A timed col lection of effluent was used to determine flow. Vascular resistance was cal culated by dividing the change in pressure by the flow, and standardizing t his for temperature and hematocrit. Average vascular resistance and standar d deviation for the gracilis, rectus, and latissimus flaps was 10.34 +/- 7. 77 mmHg per milliliter per minute, 2.79 +/- 1.50 mmHg per milliliter per mi nute, and 3.17 +/- 1.05 mmHg per milliliter per minute respectively. An inv erse relationship between muscle vascular resistance and flap mass was foun d (p < 0.001). This indicates that larger muscles have less vascular resist ance. The decreased resistance gives rise to higher flow rates and, as a re sult, potentially improved vein graft patency. The clinical implication is that a larger flap should be used when high flow-through is critical. The r ole of flap vascular territory makeup continues to be pursued.