Clinical characteristics and outcome of patients with acute myocardial infarction and preinfarction angina.

OBJECTIVES/
BACKGROUND: Preinfarction angina is associated with reduced myocardial infarct size in patients treated with thrombolysis. Our objective was to assess the relation between preinfarction angina and infarct size, left ventricular function and clinical outcome in patients treated with primary angioplasty (PTCA) and compare this with patients treated with thrombolysis.
METHODS: In the Zwolle Infarction Study, 953 patients were treated for acute myocardial infarction between 1990 and 1996; 761 patients underwent primary PTCA and 192 patients received thrombolysis as reperfusion therapy.
RESULTS: Preinfarction angina was present in about 50% of the patients, who were categorised into angina ≤24 hours and angina >24 hours before infarction. Patients in both treatment groups have a longer ischaemic time when preinfarction angina is present. In patients treated with thrombolysis, preinfarction angina ≤24 hours results in a smaller enzymatic infarct. Thrombolysis seems to be more effective when preinfarction angina occurs within the 24 hours prior to myocardial infarction. Collateral filling of the infarct-related artery is more often seen in patients with preinfarction angina. In the primary PTCA group, a longer ischaemic time in patients with preinfarction angina does not result in increased infarct size, and this effect remains after excluding patients with collateral filling.
CONCLUSIONS: The protective effect of preinfarction angina is likely to be due to better collateral filling of the infarct-related artery and to ischaemic preconditioning of the myocardium.