A new study reveals that individuals who were admitted to hospital following a first heart attack without previous cardiovascular disease, who had reduced coronary heart disease risk factors, such as hypertension (high blood pressure) and smoking had an associated increased risk of dying in the hospital. The investigation is published in the Nov. 16 issue of JAMA, a theme issue on cardiovascular disease, released early online to accompany the American Heart Association Scientific Sessions. Prior investigations have analyzed the incidence of CHD risk factors, such as smoking, high blood pressure, diabetes and dyslipidemia, in individuals with myocardial infarction (MI; heart attack). According to background data in the study:
“Most of these studies did not focus on inpatient mortality during hospitalization for first MI. However, a recent study from a quality improvement initiative reported a modest but surprising inverse association between number of CHD risk factors and mortality in patients with non-ST-segment elevation MI (a certain pattern on an electrocardiogram following a heart attack) only.”
John G. Canto, M.D., M.S.P.H., of the Watson Clinic LLP, Lakeland, Fla., and his team carried out an investigation using data from the National Registry of Myocardial Infarction (1994-2006) in order to assess the absence and presence of five leading traditional CHD risk factors:
- Family history of CHD
They also measured hospital mortality rates among 542,008 individuals with first MI and without previous cardiovascular disease.
They discovered that at hospitalization, 14.4% of participants in the investigation had no risk factors identified, 81% of participants had 1 to 3 CHD risk factors, and 4.5% of study participants had 4 to 5 CHD risk factors. The most prevalent risk factor among participants with primary MI was hypertension (52.3%), followed by smoking (31.3%) family history of CHD (28.0%), dyslipidemia (28.0%), and diabetes (22.4%). Age among participants varied inversely with the number of CHD risk factors, from an average age of 56.7 years with 5 risk factors to 71.5 years with 0 risk factors.
50,788 was the total number of in-hospital all-cause deaths. Examination of the data revealed that there was an opposite association between the number of CHD risk factors and overall crude mortality determined at presentation to the hospital:
- For 0 risk factors the mortality rate was 14.9%
- for 1 risk factor – 10.9%
- for 2 risk factors – 7.9%
- for 3 risk factors – 5.3%
- for 4 risk factors – 4.2%
- and for 5 risk factors – 3.6%
The investigators explain:
“After adjusting for age and other important outcome-associated factors at presentation, there was a significant inverse relationship between adjusted mortality and number of CHD risk factors present at hospitalization.”
This connection was consistent among several patient subgroups and age strata.
According the to the investigators the absence of CHD risk factor exposure should not necessarily be seen as a guarantee for a good prognosis. They state:
“There may be multiple explanations for our finding of an inverse association between number of risk factors and mortality. These explanations can be grouped into methodological issues of ascertainment and other biases that limit useful inferences regarding causality vs. real differences in pathophysiology, medical management, or both across groups with different numbers of risk factors.
Future studies should seek to gain insight into the possible explanations of such an association.”
Written by Grace Rattue