Coronary artery bypass

Autor: Philip B. Dobrin, Roque Pifarré, Henry J. Sullivan, John F. Moran, Thomas Canfield
Rok vydání: 1977
Předmět:
Zdroj: The Journal of Thoracic and Cardiovascular Surgery. 74:445-454
ISSN: 0022-5223
DOI: 10.1016/s0022-5223(19)41361-5
Popis: Thirty-nine saphenous veins (SV’s) and nine internal mammary arteries (IMA’s) were obtained from patients at operation. The vessels were mounted in a tissue bath and pressurized while diameter and length were measured. Measurements of wall volume were obtained radiologically. IMA’s increased gradually in diameter up to 200 mm. Hg; SV’s increased sharply in diameter up to 50 mm. Hg and then exhibited constant diameter. At 100 mm. Hg, IMA diameter was 2.7 ± 0.2 mm. and SV diameter was 4.7 ± 0.2 mm. Mean wall thicknesses of IMA’s and SV’s were 0.26 and 0.39 mm., respectively. Based on these data, at any volume flow, flow velocities in IMA’s were computed to be three times those in SV’s. Reynolds numbers computed for IMA and SV diameters indicated that flow in bypass grafts probably is nonturbulent. At 100 mm. Hg, activation of the vascular muscle elicited a 15 percent decrease in diameter of IMA’s, but only a 3 percent decrease in diameter of SV’s. In related studies, steel tubes 0.84 to 4.39 mm. inner diameter were perfused with human blood to measure the pressure drop with flow. For flows up to 200 c.c. per minute, pressure drop was minimal with decreasing diameter until 2 to 3 mm. was encountered. At this diameter, pressure loss increased sharply. Integration of flow-pressure loss data for IMA and SV diameters showed that the cumulative pressure loss along the course of IMA’s results in decreased exit pressure to perfuse native coronary vessels. This provides a quantitative physiological explanation for the lower coronary flows obtained clinically with IMA’s as compared with SV’s.
Databáze: OpenAIRE
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