The Changing Heart Rate May Hold the Key to Life
Abstract & Commentary
By Rahul Gupta, MD, MPH, FACP, Clinical Assistant Professor, West Virginia University School of Medicine, Charleston, WV. Dr. Gupta reports no financial relationships relevant to this field of study.
Synopsis: In people without known cardiovascular disease, an increase in resting heart rate with age was associated with an increased risk of death.
Source: Nauman J, et al. Temporal changes in resting heart rate and deaths from ischemic heart disease. JAMA 2011;306: 2579-2587.
Several large epidemiologic studies have demonstrated that resting heart rate (RHR) is an independent predictor of cardiovascular and all-cause mortality in men and women with and without diagnosed cardiovascular disease.1,2 Similar to blood pressure, heart rate shows a clear circadian rhythm, being substantially higher during waking hours as well as being about 3 beats/minute higher in sitting compared with the supine position. Bottom line is that tachycardia at rest is prognostically unfavorable. Furthermore, heart rate reduction itself may be an important mechanism of action for certain groups of drugs, including beta-blockers, that have proven mortality benefits in coronary artery disease and heart failure. However, RHR is an adaptable factor that may change over time or in response to physical activity, external environment, or medical therapy. A better understanding of this modifiable risk factor may allow us to influence it positively. Past studies on the subject have not been conclusive as to the effect of age on heart rate changes. Therefore, it is important to understand the temporal changes associated with RHR that may influence the risk of death, especially from ischemic heart disease (IHD).
In their prospective cohort study of 29,325 Norwegian men and women without known cardiovascular disease, RHR was measured on two separate occasions approximately 10 years apart. The second measurement was obtained between 1995 and 1997 and subsequent mortality follow-up was conducted until December 31, 2008. The researchers found that an increase in RHR was associated with an increase in risk of death from IHD and all-cause mortality. Specifically, compared with study patients with a RHR less than 70 beats/min at both of the measurements, in patients with a RHR of less than 70 beats/min at the first measurement but greater than 85 beats/min at the second measurement, the adjusted hazard ratio (AHR) was 1.9 for IHD-related and 1.5 for all-cause mortality. This would mean that if a patient's heart rate increased from less than 70 beats/min to greater than 85 beats/min over a decade, the risk of death from IHD was 90% higher and a risk of death from all causes was 50% higher. Similarly, for patients with RHR between 70 and 85 beats/min at the first measurement and greater than 85 beats/min at the second measurement, the associated AHR was 1.8 for IHD-related and 1.4 for all-cause mortality. Thus, if a patient's heart rate increased from being between 70 beats/min and 85 beats/min to greater than 85 beats/min over a decade, the risk of death from IHD was 80% higher and a risk of death from all causes was 40% higher. However, the association of change in RHR with IHD mortality was not linear, suggesting that a decrease in RHR with age demonstrated no general mortality benefit.
Commentary
Heart rate is a simple and easily measurable clinical parameter and yet we may not fully understand its wide ranging clinical implications. Historically, being a poor reproducible clinical sign as well as being labeled a mere marker of sympathetic activity, little attention has been paid to the measurement of RHR for cardiovascular risk assessment in routine clinical practice, in spite of a large body of evidence showing that higher RHR is a risk factor for total and cardiovascular mortality. It is also important to understand that while heart rate lowering may not be a target for treatment in most patients, cardiovascular mortality lowering effects of agents such as beta-blockers may be linked in part to their ability to lower the RHR as demonstrated in a meta-regression analysis.3 In this study, a statistically significant relationship was found between RHR and decreases in cardiac and all-cause mortality from beta-blockers and calcium channel blockers, strongly suggesting that RHR reduction could be a major determinant of the clinical benefits seen in those clinical trials. RHR should, therefore, be more carefully evaluated at each visit in every patient, especially those with cardiovascular disease. For those without cardiovascular disease, identifying such individuals and lowering their RHR by physical activity, diet, weight management, and not smoking may delineate the cornerstone of primary prevention.
References
1. Fox K, et al. Resting heart rate in cardiovascular disease. J Am Coll Cardiol 2007;50:823-830.
2. Palatine P, Julius S. Elevated heart rate: A major risk factor for cardiovascular disease. Clin Exp Hypertens 2004;26:637-644.
3. Cucherat M. Quantitative relationship between resting heart rate reduction and magnitude of clinical benefits in post-myocardial infarction: A meta-regression of randomized clinical trials. Eur Heart J 2007;28:3012-3019.
In people without known cardiovascular disease, an increase in resting heart rate with age was associated with an increased risk of death.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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