What are the risks of myocardial infarction and death in someone with unstable angina during hospital admission, at six months and one year?

The risks of myocardial infarction (MI) and death following the diagnosis of unstable angina (UA) depend on the accuracy of the diagnosis. Braunwald’s classification categorises patients according to the severity of the pain (new onset/accelerated and pain at rest, either within the last 48 hours or >48 hours) and to the clinical circumstances (primary, secondary (e.g. to anaemia) and post-infarction). Using this classification, one study showed an in-hospital AMI/death rate of 11% for patients with rest pain within the last 48 hours, 4% for patients with rest pain >48 hours previously and 4% for patients with new onset/accelerated angina.1 The in-hospital AMI/death rate was markedly raised in patients with post-infarct angina (46%) compared with patients with “primary” unstable angina.

The event rate is highest at and shortly following presentation, falling off rapidly in the first few months to a level similar to stable angina patients after one year. Patients with new onset angina have a better prognosis than those with acceleration of previously stable angina or patients with rest pain. Patients with accelerated or crescendo angina have an in-hospital mortality of 2-8% and a 1 year survival of 90%. Although patients with non- Q wave MI, also considered within the umbrella term UA, have a more benign in-hospital course than Q-wave MI patients, they have higher readmission, reinfarction and revascularisation rates subsequently. Infarct extension in-hospital is associated with a far worse prognosis in non-Q wave MI (43% mortality, vs 15% in Q wave MI). The following are also associated with a worse prognosis in unstable angina: ST segment deviation on the ECG (but not T wave changes), elevated cardiac enzymes, transient myocardial ischaemia on Holter monitoring, an abnormal predischarge exercise test, extensive coronary artery disease and impaired left ventricular function.

The OASIS registry,2 gave 7 day death/MI rates of 3.7–5.6% and 6 month rates of 8.8–11.9%. Similarly, the VANQWISH trial3 gave the following rates of death/non-fatal MI: 3.2–7% at hospital discharge, 5.7–10.3% at 1 month and 18.6–24% at 1 year.