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Does coronary artery bypass surgery restore normal maximal coronary flow reserve? The effect of diffuse
Insights
Coronary artery bypass graft surgery may not fully restore blood flow in bypassed vessels due to underlying atherosclerosis. However, grafts to normal heart muscle show normal flow reserve, indicating successful restoration in select cases.
Area of Science:
- Cardiovascular Surgery
- Interventional Cardiology
- Vascular Physiology
Background:
- Aortocoronary vein bypass surgery aims to restore blood flow to coronary arteries.
- Residual diffuse atherosclerosis can limit maximal hyperemia and coronary flow reserve (CFR).
- Focal stenosis at the graft-coronary anastomosis may also impede flow.
Purpose of the Study:
- To investigate the impact of diffuse atherosclerosis and anastomosis stenosis on CFR in bypass grafts.
- To assess CFR in bypass grafts supplying angiographically normal coronary vessels.
- To compare CFR in bypass grafts with CFR in normal coronary arteries.
Main Methods:
- Measured CFR using a subselective Doppler catheter in 35 bypass grafts across 24 patients.
- Assessed graft, anastomosis, and distal coronary vessel dimensions via quantitative coronary angiography.
- Compared CFR and dimensions with 13 patients with normal coronary vessels.
Main Results:
- Bypass grafts with unobstructed anastomoses (<50% stenosis) perfusing normal myocardium had normal CFR (5.0 ± 0.4), similar to normal arteries (5.1 ± 0.6).
- Native coronary arteries distal to bypass insertion were 40% smaller in cross-sectional area than normal vessels.
- Bypass grafts supplying hypertrophied or infarcted myocardium showed significantly reduced CFR (2.7 ± 0.3) compared to normal vessels.
Conclusions:
- Aortocoronary vein bypass surgery can restore normal CFR to bypassed vessels if the anastomosis is unobstructed and the myocardium is normal.
- Diffuse atherosclerosis and anastomosis stenosis may limit CFR, but are not the sole determinants.
- Myocardial status (hypertrophy, infarction) significantly impacts CFR in bypassed vessels, even with patent grafts.
Abstract:
Aortocoronary vein bypass surgery might not restore normal maximal coronary flow reserve to bypassed coronary vessels because residual diffuse coronary atherosclerosis might limit maximal hyperemia. To investigate the effect of diffuse atherosclerosis and a focal stenosis at the graft-coronary anastomosis, we measured coronary flow reserve with an extensively validated subselective Doppler catheter in 24 patients with 35 bypass grafts perfusing angiographically normal coronary vessels. The Doppler catheter was positioned in the midportion of the graft, and coronary flow reserve was measured as the peak/resting velocity ratio after selective graft injection of a maximally vasodilating dose of papaverine. Luminal dimensions of the bypass graft, graft-coronary insertion, and bypassed coronary vessel were measured by quantitative coronary angiography (Brown/Dodge method). Measurements of coronary flow reserve and coronary dimensions of vein bypass grafts were compared with similar measurements obtained from 13 patients with normal coronary vessels and normal myocardium. Seventeen of the 35 bypass grafts perfused unobstructed coronary-vein graft anastomoses (less than 50% area stenosis) and normal myocardium. The coronary flow reserve of these 17 bypass grafts was normal (5.0 +/- 0.4, mean +/- SEM) and not significantly different from that measured in normal arteries (5.1 +/- 0.6), even though the cross-sectional area of the native coronary artery just distal to the bypass insertion was 40% smaller than in matched normal vessels. Bypass grafts perfusing hypertrophied (n = 2) or infarcted (n = 6) myocardium had significantly reduced coronary flow reserve compared with normal vessels (2.7 +/- 0.3; p less than .01), even when the infarcted wall had only minimal hypokinesis.(ABSTRACT TRUNCATED AT 250 WORDS)