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Low-Tech Screen for Heart Disease
Abstract & Commentary
By Allan J. Wilke, MD , Associate Professor of Family Medicine, University of Alabama at Birmingham School of MedicineHuntsville Regional Medical Campus, Huntsville. Dr. Wilke reports no financial relationship to this field of study.
Synopsis: An elevated resting heart rate is a risk factor for heart disease.
Source: Hsia J, et al. Resting heart rate as a low tech predictor of coronary events in women: Prospective cohort study. BMJ 2009;338:b219; doi: 10.1136/bmj.b219.
Using the Women's Health Initiative database, these authors examined the predictive role that resting heart rate (RHR) plays in heart disease. The WHI is a very large study with 161,808 postmenopausal women enrolled. This study gathered data from women enrolled in the WHI's randomized trials and from its observational study. After excluding women with a history of myocardial infarction, stroke, or coronary revascularization and those using beta-blockers, digoxin, or calcium channel blockers, 129,135 women were left for analysis. The outcomes of interest were myocardial infarction, coronary death, and stroke. The first two outcomes were grouped as coronary events.
The RHRs were divided into quintiles: ≤ 62 beats per minute (bpm), 63-66 bpm, 67-70 bpm, 71-76 bpm, and > 76 bpm. The women were followed for almost 8 years, during which they suffered 2281 coronary events and 1877 strokes.
Several interesting (and statistically significant) trends emerged when single variables were examined. As RHR increased, so did age at baseline and the percentage of women with hypertension, diabetes mellitus, current smoking status, hypercholesterolemia requiring drug therapy, depression, nervousness, and body mass index. Physical activity, alcohol use, and postmenopausal hormone therapy use all declined with increasing RHR. Using the lowest quintile as the reference, the hazard ratio (HR) for coronary events trended upward, and became statistically significant at 1.68 when comparing the highest to the lowest quintile. It remained statistically significant in multivariate analysis at 1.26. The same was not true for stroke. Although RHR was associated with stroke in univariate analysis, this association disappeared in multivariate analysis. Other more commonly recognized risk factors for coronary events and stroke were also examined. To place RHR in perspective, the hazard ratios for hypertension, diabetes mellitus, and smoking were 1.69, 2.68, and 2.32 for coronary event and 1.87, 1.94, and 1.95 for stroke, respectively.
Ever since this study came out, I've been paying more attention to RHR in my patients, and it seems like they're all greater than 76! However, the first thing to remember with this study is its population: healthy, postmenopausal women who weren't taking medications that might slow their heart rates. The women sat quietly for 5 minutes before having their pulse taken. In my office, all patients are marched to the vitals station and have their pulse, blood pressure, temperature, and respiratory rate measured without a rest period.
This study's strengths are its large size and prospective nature. Its main limitation is its population lacked younger women and men. What is the link between elevated RHR and coronary events? The authors speculate about high sympathetic or autonomic tone, but since this was not a randomized trial, only associations can be inferred. Elevated RHR in prehypertensives (either 120-139 mm Hg systolic or 80-89 mm Hg diastolic) has been previously shown to be a risk factor for coronary heart disease in the Atherosclerosis Risk in Communities (ARIC) study1 and a risk factor for death in hypertensives in a primary care setting.2 In the first study, prehypertensives with a RHR ≥ 80 bpm had a HR of 1.49 for a coronary event or revascularization, compared to the group whose RHR was 60-69 bpm. This is similar to the HR in this study.
Faithful readers will recall that Internal Medicine Alert3 reviewed a related study4 also derived from the WHI database that associated elevated white blood cell counts and four types of cancer in women. Back then our advice was to perform follow-up testing of any woman with an unexplained WBC elevation, "based on her risk factors and any previous testing." The same approach holds here. If you have a generally healthy, postmenopausal woman with no known heart disease who is not taking a medication that could slow her heart rate, it would be in her best interest for you to review her cardiovascular risk factors closely and aggressively work to reduce them.
1. King DE, et al. Long-term prognostic value of resting heart rate in subjects with prehypertension. Am J Hypertens 2006;19:796-800.
2. Tierney WM, et al. Quantifying risk of adverse clinical events with one set of vital signs among primary care patients with hypertension. Ann Fam Med 2004;2: 209-217.
3. Wilke AJ. A simple screen for cancer? Intern Med Alert 2008;30:1-2.
4. Margolis KL, et al. Prospective study of leukocyte count as a predictor of incident breast, colorectal, endometrial, and lung cancer and mortality in postmenopausal women. Arch Intern Med 2007;167: 1837-1844.