Scintigraphic comparison of graft patency between the left internal thoracic artery and saphenous vein graft after coronary bypass surgery

Graft patency after coronary bypass surgery (CABG) was evaluated with stress 201-thallium scintigraphy (stress 201Tl) in 26 cases, including 13 cases using the left internal thoracic artery (LITA group) in situ and 13 cases with saphenous vein graft (SVG group). All of them had effort or unstable angina caused by LAD lesion without apparent infarction. Stress 201Tl using a symptom-limited, graded bicycle exercise test was performed before CABG and 1 month, 6 months to 1 year, and 1 year to 1.5 years after surgery. Five tomographic images including the apical side of the area fed by the bypass anastomosed to LAD in short axial sections were picked out and piled up. Fan-shaped ROI was made on this area and % Tl uptake was calculated using the following formula. 201Tl counts in ROI-Background counts / Maximum counts-Background counts x 100 (%). The normal % Tl uptake calculated in the control group (n=11) in this ROI was 68.2±4.8%. Preoperative % Tl uptake showed 49.3±0.2% in the LITA group and 54.3±13.2% in the SVG group. % Tl uptake of the SVG group 1 month after CABG was slightly higher than that of the LITA group, (62.0±7.0% vs. 56.3±7.6%). However 6 months to 1 year after CABG, % Tl uptake of the LITA group increased to 60.8±6.4%, in spite of a tendency on the decrease of that in the SVG group, (59.0±8.5%), and furthermore, 1 year to 1.5 years after CABG, increased to 62.3±5.1% near the normal % Tl uptake of the control group and the SVG group decreased to 58.8±6.8%. This result suggested that arterial in situ bypass graft might have an auto-regulation and 'growth property' corresponding to flow demand, and this helps the excellent long-term patency of arterial bypass grafts. (author)