Age-related differences in in-hospital mortality and the use of thrombolytic therapy for acute myocardial infarction

Abstract

Background: Recent guidelines have acknowledged that thrombolysis decreases mortality from acute myocardial infarction (AMI) independently of age. The purpose of this study was to determine the age-related rates of thrombolytic administration and in-hospital mortality and the variables related to the use of thrombolytic therapy for patients with AMI.

Methods: A prospective cohort analysis involved a registry of 44 acute care Quebec hospitals that enrolled 3741 patients with AMI between January 1995 and May 1996. The main outcomes of interest were crude and adjusted age-related in-hospital mortality rates and rates of use of thrombolytic therapy.

Results: In-hospital mortality rates increased dramatically with age from 2.1% in patients with AMI who were less than 55 years of age to 26.3% in those who were 85 years of age or older. Overall, 35.8% of the patients received thrombolysis. There was a pronounced inverse gradient in the use of thrombolysis with age, ranging from 46.2% in the youngest age group (< 55 years) to 9.5% in the oldest group (> or = 85 years). After adjustment for potential confounders, the older patients remained significantly less likely to receive thrombolytic therapy. Compared with patients who were less than 55 years of age, the odds ratio of receiving thrombolytic therapy was 0.68 (95% confidence interval [CI] 0.52-0.89) for patients aged 65-74 years, 0.48 (95% CI 0.35-0.65) for patients aged 75-84 years and 0.13 (95% CI 0.06-0.26) for patients aged 85 years or more. Other variables related to thrombolytic therapy were diabetes (odds ratio [OR] 0.77, 95% CI 0.59-1.00), cerebrovascular disease (OR 0.46, 95% CI 0.30-0.72), angina (OR 0.73, 95% CI 0.56-0.95), typical chest pain (OR 2.56, 95% CI 1.88-3.47); ST elevation (OR 8.93, 95% CI 7.24-11.00), Q wave MI (OR 5.26, 95% CI 4.20-6.60) and increased length of time between onset of symptoms and arrival at hospital.

Interpretation: Age is an important independent predictor of in-hospital mortality and lower thrombolytic use following AMI. Other studies are required to further evaluate the appropriateness of thrombolytic therapy for elderly patients.

Fig. 1: Patients who were ideal candidates for thrombolytic therapy (ST elevation, no history of cerebrovascular disease and no contraindication to thrombolytic therapy, and time between onset of symptoms and arrival at hospital was less than 12 hours) (top). Patients among those ideal candidates who received thrombolytic therapy (bottom).