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Predictive value of myocardial perfusion imaging for aortocoronary bypass surgery
Insights
Myocardial perfusion scans accurately identify patients who will benefit from autologous coronary bypass (ACB) surgery. Normal scans indicate good capillary beds, predicting improved left ventricular function post-surgery, even with occluded arteries.
Area of Science:
- Cardiology
- Nuclear Medicine
- Cardiovascular Surgery
Background:
- Autologous coronary bypass (ACB) surgery evaluation relies on cardiac catheterization.
- Left ventricular angiography cannot differentiate reversible from irreversible myocardial dysfunction.
Purpose of the Study:
- To evaluate the utility of myocardial perfusion imaging in predicting outcomes after autologous coronary bypass surgery.
- To determine if preoperative myocardial perfusion scans can identify patients with reversible myocardial dysfunction.
Main Methods:
- 82 patients undergoing ACB surgery were injected with iodine-131 labeled albumin macroaggregates and technetium-99m labeled microspheres.
- Injections were performed into native and grafted coronary arteries pre- and post-operatively.
- Myocardial distribution of particles was visualized using a rectilinear scanner.
Main Results:
- 67 patients had normal preoperative myocardial perfusion scans; 34 of these had abnormal wall motion but showed significant improvement in left ventricular function post-surgery (ejection fraction increased from 56% to 65%).
- 15 patients with abnormal preoperative scans only improved if the bypass graft supplied an area with normal preoperative perfusion.
- Normal myocardial scans indicate an adequate capillary bed, regardless of coronary artery stenosis severity.
Conclusions:
- Preoperative myocardial perfusion imaging is a valuable tool for selecting patients for autologous coronary bypass surgery.
- Normal myocardial scans predict successful outcomes and improved left ventricular function after ACB surgery, even in cases of completely occluded coronary arteries.
- This technique helps identify patients likely to benefit from improved myocardial contractility post-ACB surgery.
Abstract:
Evaluation of patients for aotocoronary bypass (ACB) surgery is dependent on the findings at cardiac catheterization. Left ventricular angiography cannot distinguish between reversible and irreversible myocardial dysfunction. In 82 patients macroaggregates of human serum albumin, labelled with iodine-131, were injected before operation into the right coronary artery and technetium-99m labelled microspheres were injected into the left coronary artery. Two weeks after operation similar technetium-99m and iodine-131 injections were made into the native vessels and grafted vessels, respectively. Myocardial distribution of the 20 mu particles was visualized with a rectillinear scanner. Sixty-seven patients had normal myocardial perfusion scans preoperatively even though wall motion was abnormal in 34. There was substantial improvement in the left ventricular function of these 34 patients; the mean ejection fraction increased from 56 to 65%. Fifteen patients had abnormal myocardial perfusion scans; improvement in left ventricular function in this group occurred only if the bypass graft was made to an area with normal regional perfusion preoperatively. It is certain that an adequate capillary bed is present if the myocardial scan is normal, regardless of the degree of critical stenosis in either coronary artery. The patient with a completely occluded coronary artery and normal myocardial scan is a good candidate for ACB and will show improved left ventricular contraction if the ACB is patent,