Surgery for acute coronary syndromes

This thesis comprises two observational retrospective and three prospective studies of patients with acute coronary syndromes undergoing urgent coronary bypass surgery. All included patients underwent coronary artery bypass surgery at the Karolinska Hospital in Stockholm.

Patients: During 1980-1995, a total of 6728 patients underwent a first coronary artery bypass operation. Early and late mortality after the operation were studied in relation to the severity of unstable angina before the operation. For those operated on 1990-95 (n=853) the combined events death or the rate of acute myocardial infarction within 30 days of the operation were studied and related to risk factors and time period of surgery.

In the prospective studies peri-operative troponin-T levels and postoperative blood loss were related to the early clinical course in 200 patients, 100 of whom had unstable angina at the time of the operation. In 50 unstable patients, pre-operative levels of coagulation and fibrinolytic system markers and platelet activity were studied in relation to the severity of unstable angina.

Results: Patients with an acute myocardial infarction within two weeks, and angina within two days before the operation (Braunwald class IIIC) had an almost five-fold increase in the risk of death within 30 days of the operation after multivariate correction for confounding factors than in patients operated on for stable angina (6.2% versus 1.6%). In Braunwald class IIIC patients there seemed to be an increased risk of death also within six months after the operation (odds ratio 2.4, 95% confidence limit 0.8-7.1). There was a 50% reduction in early death or acute myocardial infarction rate in unstable patients operated on during 1994-95 than if the operation was performed during 1990-91. The early mortality declined from 9.7% in 1990 to 2.6% in 1995. The improvement could not be explained by changes in patient risk factors during the study period.

A troponin-T level higher than 0.10[my]g/1 before the operation was present in 67% of the Braunwald class IIIC unstable patients but in none of the stable patients. The Braunwald class IIIC patients had significantly higher incidence of peri-operative myocardial infarction than stable patients (27% versus 2%), postoperative use of inotropic support (27% versus 4%) and need for an intra-aortic balloon pump (20% versus 1%).

Median blood loss was 500 in] during the operation and 600 ml after the operation in both unstable and stable patients. Antithrombotic treatment with acetylsalicylic acid and dalteparin did not increase the postoperative blood loss. Female gender and a large body mass index were associated with less postoperative bleeding.

The pre-operative levels of antithrombin HI were lower, and the levels of fibrinogen and plasminogen activator inhibitor-1 were higher in unstable than in stable patients. There were signs of activated coagulation immediately before coronary artery bypass surgery in about half of Braunwald class IIIC unstable patients, and in about one third of patients undergoing elective surgery for stable angina.

Conclusion: The risk of death or acute myocardial infarction within 30 days after coronary artery bypass surgery declined substantially during the 1990s. The risk of early death was higher in Braunwald class IIIC unstable patients than in patients undergoing elective coronary artery bypass surgery. These patients frequently had an elevated troponin-T level before the operation. The postoperative blood loss was similar in stable and unstable patients, regardless of ongoing antithrombotic treatment. There were signs of activated coagulation immediately before the operation in about half of Braunwald class IIIC unstable patients, and in about one third of the stable patients undergoing elective surgery.

List of scientific papers

I. Bjessmo S, Ivert T, Flink H, Hammar N (2001). "Early and late mortality after surgery for unstable angina in relation to Braunwald class." Am Heart J 141(1): 9-14
https://pubmed.ncbi.nlm.nih.gov/11136481

II. Bjessmo S, Hammar N, Sandberg E, Ivert (2000). "Reduced risk of coronary artery bypass surgery for unstable angina during a 6-year period. " Eur J Cardiothorac Surg 18(4): 388-92
https://pubmed.ncbi.nlm.nih.gov/11024373

III. Bjessmo S, Ivert T (2000). "Troponin-T in patients with unstable and stable angina pectoris undergoing coronary bypass surgery. " Thorac Cardiovasc Surg 48(3): 140-4
https://pubmed.ncbi.nlm.nih.gov/10903059

IV. Bjessmo S, Ivert T (2000). "Blood loss after coronary artery bypass surgery: relations to patient variables and antithrombotic treatment. " Scand Cardiovasc J 34(4): 438-45
https://pubmed.ncbi.nlm.nih.gov/10983681

V. Bjessmo S, Ivert T, Egberg N (2000). "Coagulation system activity before coronary bypass surgery for unstable angina." (Submitted)