Infarct Mortality Lower in Unhealthy Patients

Researchers at the Watson Clinic (Lakeland, FL, USA), the University of Massachusetts Medical School (Worcester, USA), and other institutions conducted an observational study involving mortality among 542,008 patients with a first myocardial infarction (MI) registered with the US National Registry of MI between 1994-2006, who had no prior cardiovascular disease (CVD). The researchers examined the presence and absence of five major traditional coronary heart disease (CHD) risk factors--hypertension, smoking, dyslipidemia, diabetes, and family history of CHD. The main outcome measure was all-cause in-hospital mortality.

The results showed that the total number of in-hospital deaths for all causes was 50,788. In all, 85.6% of patients who presented with initial MI had at least one of the five CHD risk factors, and 14.4% had none of the risk factors. Age varied inversely with the number of CHD risk factors, from a mean age of 71.5 years with no risk factors to 56.7 years with five risk factors. Unadjusted in-hospital mortality rates were 14.9%, 10.9%, 7.9%, 5.3%, 4.2%, and 3.6% for patients with 0, 1, 2, 3, 4, and 5 risk factors, respectively. After adjusting for age and other clinical factors, there was an inverse association found between the number of CHD risk factors and hospital mortality; this association was consistent among several age strata and important patient subgroups. The study was published in the November 16, 2011, issue of the Journal of the American Medical Association (JAMA).

“One reason [for this association] appeared to be that traditional risk factors triggered better care, with greater use of evidence-based medications within the first 24 hours after MI and more angiograms and revascularization procedures,” concluded lead author John Canto, MD, MSPH, of the Watson Clinic, and colleagues. “Another possibility was that individuals with more risk factors also got more aggressive management with aspirin and other medications before their MI that improved their prognosis.”

The study also showed that a first MI with few or no risk factors was more likely to happen at an older age (mean 71.5 years with no risk factors, versus 56.7 years with five), suggesting that patients with many conventional risk factors died younger. However, the researchers added, ascertainment bias could not be ruled out, and confounding was also likely, as the study did not have data on blood pressure, lipid control, and glucose control, and had only limited data on comorbidities.

Related Links:
Watson Clinic
University of Massachusetts Medical School