A series of 16 cases of postoperative myocardial. infarction between the years 1966-1968 is presented. Fifteen of the 16 cases died in the postoperative stage. The remaining one had cardiac arrest during operation, was resuscitated successfully and went on to full recovery. The diagnosis in all cases were confirmed by ECG or at autopsy.
The average age incidence was 66.4 years. There was a slightly high incidence in the male which comprise 56% of the total. There is no predilection among the races which were composed of the following; Chinese, Indian, Malays, Eurasian and others.
Forty-four % of the patients had pre-operative cardiovascular pathology which included previous myocardial infarction, coronary arteriosclerosis, hypertension, cardiac dilatation, angina pectoris, and rheumatism etc.
Other pathology which occurred before operation in 81% of the series were BUN increase, anemia, old pulmonary tuberculosis, metabolic acidosis, lung emphysema, diabetes mellitus, and obstructive jaunuary.
Twenty-five % of the series had previous myocardial infarction. The time intervals between the previous myocardial infarct and operation range from 6 months to 8 years, indicating that myocardiar infarction which occured more than 6 months ago also gave rise to recurrence at operation.
Shock and cardiac arrest occuring during anesthesia of elderly patients with previous myocardial infarction should always raise the question as to whether a fresh infarct has occurred.
Previous reports indicate that major operations and prolonged operations are associated with postoperative myocardial infarction. But in this series average duration of operation is 49.5 minutes and some operations were of a minor nature e.g. sigmoidoscopy, esophagoscopy, and incision of mammary abscess.
All cases occurred after general anesthesia. In this series 75% had hypotension (systolic blood pressure 10 mm Hg fall below). This indicate that the most important factor contributing to postoperative myocardial i nfarction was hypotension.
During the postoperative phase important contrifactors were hypotension, anemia, metabloc acidosis, and arrhythmias.
Fifty % of postoperative myocardial infarction. occurred during the first week following operation. and 50% occurred during the second to fourth week. Almost all deaths occurred within one week of the fresh infarction.
Most cases do not give the typical clinical features, of myocardial infarction. Typical chest pains occurred in 31% of cases while hypotension occurred in 50%, Hypotension appears to be a more important presentation.
During anesthesia and the postoperative period, important predisposing factors are hypotension or shock, anemia, dehydration, electrolyte imbalance´ and arrhythmias. Reduction of the incidence of postoperative infarction would depend on correction, of the above factors..
It should be emphasised that pre-operative assessment of elderly patients should include asking for a previous history of myocardial infarction, physical´ examination, and ECG. Hypotension occurring during operation or recovery period should be corrected´ and myocardial infarction can be detected early by the use of the ECG..
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