Inferior MI greater risk for CABG than anterior

Among patients undergoing coronary artery bypass graft surgery (CABG), those with a history of previous myocardial infarction (PMI) have poorer post-operative cardiovascular outcomes than those without. However it remains unclear whether there are differences in outcomes after CABG between patients with anterior PMI versus those with inferior PMI.

Fukui et al. retrospectively reviewed the medical records of 310 patients with a history of PMI whom underwent CABG without valve replacement. PMI was defined as myocardial infarction occurring more than 30 days before surgery. PMI was confirmed most commonly by scintigraphy, although ECG, echocardiography, and MRI were also used. Patients with lateral MI or a combination of anterior and inferior MI were excluded. 151 patients with anterior PMI and 159 patients with inferior PMI were included in the study.

Investigators found that patients with inferior PMI were older (68.3 ± 9.2 vs 65.5 ± 11.0, p = 0.015), had a greater number of diseased vessels per patient (2.9 ± 0.3 vs 2.8 ± 0.5, p = 0.009), had a lower incidence of diabetes (44.0% vs 58.3%, p = 0.02) and a higher rate of mitral regurgitation (18.2% vs 8.6%, p = 0.02) as compared to patients with anterior PMI. There were no differences between groups with respect to operative technique, number of grafts and completeness of revascularisation.

Patients with a history of inferior PMI were observed to have a higher incidence of respiratory failure, requirement for haemodialysis, increased operative mortality and a combined clinical endpoint of operative death and major complications (table).

Inferior PMI

Anterior PMI

p value

Operative mortality

5.0 %

0%

0.007

Respiratory failure

6.9%

0.7%

0.019

Haemodialysis

5.7%

0.7%

0.006

Combined endpoint

18.9%

6.6%

0.002

Multivariate analysis revealed inferior PMI to be the only independent predictor of major postoperative complications including death (p = 0.007). The mechanistic explanation for this remains unclear, however potential right ventricular dysfunction following prior inferior MI may adversely affect respiratory function and renal perfusion. Further large scale randomised control trials may help to explain this observation which, if reproduced, may assist pre-operative risk stratification algorithms.

Fukui T, Shimokawa T, Manabe S et al. Prior Inferior Myocardila Infarction Has Worse Early Outcomes in Patients Undergoing Coronary Artery Bypass Grafting Than Prior Anterior Myocardial Infarction. Ann Thorac Surg 2009;87:475-80

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