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Persistent but reversible coronary microvascular dysfunction after bypass grafting
Insights
Coronary artery bypass grafting (CABG) improves myocardial blood flow and coronary vasodilator reserve. This study shows slow recovery of microvascular function after CABG surgery.
Area of Science:
- Cardiology
- Nuclear Medicine
- Vascular Physiology
Background:
- Coronary artery bypass grafting (CABG) is a common procedure for severe coronary artery disease.
- The impact of CABG on absolute myocardial blood flow (MBF) and coronary microvascular function remains incompletely understood.
Purpose of the Study:
- To investigate the effects of CABG on absolute myocardial blood flow (MBF) at rest and during hyperemia.
- To assess changes in coronary vasodilator reserve and coronary resistance post-CABG.
Main Methods:
- Positron emission tomography (PET) with H(2)(15)O was used to measure MBF in eight patients with three-vessel disease.
- Measurements were taken at rest and during pharmacologic hyperemia (dipyridamole) before, and 1 and 6 months after CABG.
Main Results:
- CABG significantly increased resting and hyperemic MBF at 6 months post-surgery compared to pre-operative values.
- Coronary vasodilator reserve progressively increased, while minimal coronary resistance significantly decreased after CABG.
- These improvements suggest a slow but progressive recovery of microvascular function post-CABG.
Conclusions:
- CABG enhances coronary vasodilator reserve through a reduction in minimal coronary resistance.
- The findings indicate persistent microvascular dysfunction that gradually improves over 6 months following CABG surgery.
Abstract:
The effect of coronary artery bypass grafting (CABG) on absolute myocardial blood flow (MBF) has not been investigated previously. MBF (ml. min(-1). g(-1)) was measured at rest and during hyperemia (0.56 mg/kg iv dipyridamole) using H(2)(15)O and positron emission tomography in eight patients with three-vessel disease before surgery and 1 and 6 mo after full revascularization. Baseline MBF was 0.87 +/- 0.12 preoperatively and 1.04 +/- 0.14 and 0.95 +/- 0.13 at 1 and 6 mo after CABG, respectively (P < 0.05, 6 mo vs. preoperatively). Hyperemic MBF was 1.36 +/- 0.28 preoperatively and increased to 1.98 +/- 0.50 and 2.45 +/- 0.64 at 1 and 6 mo after CABG, respectively (P < 0.01, 6 mo vs. preoperatively). Coronary vasodilator reserve (hyperemic/baseline MBF) increased from 1.59 +/- 0.40 preoperatively to 1.93 +/- 0.13 and 2.57 +/- 0.49 at 1 and 6 mo, respectively (P < 0.05, 6 mo vs. preoperatively). Minimal (dipyridamole) coronary resistance (mmHg. min. g(-1). ml(-1)) fell progressively from 59.37 +/- 14.56 before surgery to a nadir of 35. 76 +/- 10.12 at 6 mo after CABG (P < 0.01 vs. preoperatively). The results of the present study confirm that CABG improves coronary vasodilator reserve progressively as a result of reduction in minimal coronary resistance. These data suggest persistent microvascular dysfunction that recovers slowly after surgery.