Myocardial infarction after aortocoronary saphenous vein bypass. Vectorcardiographic study

Vectorcardiography is superior to conventional ECG for detection of myocardial injury after coronary surgery

OBJECTIVE

The reliability of conventional scalar ECG for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery has been questioned. For the diagnosis of myocardial infarction in general vectorcardiography (VCG) is superior to ECG. Therefore, the usefulness of conventional VCG and computerized analysis of spatial VCG changes for diagnosis of PMI were studied.

DESIGN

VCG registrations were obtained from 218 patients undergoing coronary surgery. The spatial QRS vector loop area of each VCG registration was calculated and the loop area before surgery compared with the loop area after surgery. Conventional VCG criteria for myocardial infarction and set values for loop area reduction were related to sustained elevation of plasma troponin-T and clinical course.

RESULTS

Both conventional VCG criteria and spatial changes translated better than Q-waves on scalar ECG into elevation of biochemical markers of myocardial injury and impaired clinical course.

CONCLUSION

VCG appears superior to conventional ECG as regards detection of myocardial injury in coronary surgery. Computerized programs have facilitated the registration and the interpretation of VCG and this methodology deserves further evaluation in cardiac surgery.

Survival in subgroups of patients with left main coronary artery disease. Veterans Administration Cooperative Study of Surgery for Coronary Arterial Occlusive Disease

This report presents the 42-month survival experience of 91 patients with a significant lesion of the left main coronary artery in the Veterans Administration Cooperative Study of Coronary Bypass Surgery. Survival in surgical patients was significantly better than that in the medical group (p = 0.016), even after adjustments were made for two important differences in baseline characteristics--duration of angina and high risk by angiographic criteria--between the two groups (p = 0.019). Subgroups based on severity of left main stenosis and on left ventricular (LV) function showed significant trends in favor of surgery in patients with more than 75% left main stenosis and in those with abnormal LV function. A similar but nonsignificant trend was seen in the two subgroups with 50-75% stenosis or with normal LV function. The surgical benefits were not significantly different between the categories of the subgroups defined separately by stenosis and LV function. Low-, middle- and high-risk subgroups based on four noninvasive clinical predictors also showed significantly improved survival with surgery in the high-risk group. The low-risk groups showed a slight, nonsignificant disadvantage with surgical treatment. These data support the view that patients with left main disease are not a homogeneous group. High- and low-risk subgroups with different outcomes and responses to treatment can be delineated by angiographic or clinical criteria. For most patients with left main disease, coronary artery bypass grafting offers improved longevity.