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Graft patency in patients with coronary artery bypass operation complicated by perioperative myocardial infarction
Insights
Most perioperative myocardial infarctions after coronary artery bypass graft surgery are not due to graft occlusion. Patent grafts with severe native coronary stenosis suggest inadequate intraoperative myocardial preservation.
Area of Science:
- Cardiology
- Cardiac Surgery
- Medical Imaging
Background:
- Perioperative myocardial infarction (MI) is a serious complication after coronary artery bypass graft (CABG) surgery.
- Graft occlusion is often suspected as the primary cause of perioperative MI.
Purpose of the Study:
- To investigate the role of coronary artery bypass graft occlusion in perioperative myocardial infarction.
- To determine the relationship between native coronary artery disease, graft patency, and perioperative MI.
Main Methods:
- Contrast-enhanced computed tomography (CT) was used to assess graft patency in 18 patients with perioperative MI.
- Preoperative coronary angiograms were reviewed to evaluate native coronary disease and collateral circulation.
- Diagnosis of perioperative MI was based on elevated creatine kinase-MB, electrocardiographic changes, and positive pyrophosphate scans.
Main Results:
- Coronary artery bypass graft patency was observed in 14 out of 18 patients (78%) experiencing perioperative MI.
- In patients with patent grafts, severe native coronary stenosis (80%) in the grafted vessel's territory was significantly higher than in bypassed non-infarcted territories (55%).
- Only 4 patients had occluded grafts associated with perioperative MI.
Conclusions:
- The majority of perioperative MIs following CABG are not caused by graft occlusion.
- Patent grafts with significant native coronary artery disease suggest that inadequate intraoperative myocardial preservation may lead to infarction.
- A jeopardized myocardium, due to severe native vessel stenosis and lack of collaterals, is susceptible to perioperative infarction even with patent grafts.
Abstract:
Coronary artery bypass graft patency was examined by contrast-enhanced computed tomography in 18 patients with perioperative myocardial infarction soon after surgery to determine the role of graft occlusion. Preoperative coronary angiograms were reviewed to assess native coronary disease and visible collateral channels in the distribution of the myocardial infarction. Perioperative myocardial infarction was diagnosed if creatine kinase-MB was elevated, characteristic electrocardiographic changes occurred and, in the majority of cases, the pyrophosphate scan was positive. Fourteen patients (78%) had patent grafts and perioperative myocardial infarction in the distribution of the grafted vessel. Four patients had an occluded graft with infarction in the distribution of the grafted vessel. Among the 14 patients with patent grafts, there was a significant difference (p less than 0.0005) in the degree of the mean (+/- standard deviation) diameter stenosis of 80 +/- 11% in native coronary vessels supplying the perioperatively infarcted myocardium versus a 55 +/- 12% mean diameter stenosis in the 23 bypassed native coronary vessels supplying noninfarcted myocardium. It is concluded that the majority of perioperative myocardial infarcts associated with coronary artery bypass operations are not caused by graft occlusion. The severity of coronary obstruction in the grafted vessel and the lack of collateral vessels to the region of perioperative infarction in patients with patent grafts suggests that an island of jeopardized myocardium exists that is subject to inadequate intraoperative preservation.