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Etiology

An increased heart rate was associated with increased ischemic heart disease and sudden cardiac death in men

ACP J Club. 1994 Mar-April;120:48. doi:10.7326/ACPJC-1994-120-2-048


Source Citation

Shaper AG, Wannamethee G, Macfarlane PW, Walker M. Heart rate, ischaemic heart disease, and sudden cardiac death in middle-aged British men. Br Heart J. 1993 Jul;70:49-55.


Abstract

Objective

To study the association between resting heart rate and new major ischemic heart disease (IHD) in middle-aged men with and without preexisting IHD.

Design

8-year cohort study (British Regional Heart Study).

Setting

24 towns in England, Wales, and Scotland.

Participants

7735 men aged 40 to 59 years at baseline were chosen randomly from 1 group general practice in each town.

Assessment of risk factors

Baseline questionnaires and clinical and biochemical assessments were used to collect data on smoking habits, alcohol intake, serum lipid levels, body mass index, lung function, breathlessness, physical activity, preexisting IHD, and resting heart rate. IHD was divided into 3 categories using electrocardiographic findings and World Health Organization criteria (no evidence, evidence suggestive of IHD but not myocardial infarction [MI], and previous MI). Heart rate was divided into 5 categories (< 60, 60 to 69, 70 to 79, 80 to 89, and ≥ 90 beats/min).

Main outcome measures

Sudden cardiac death and other fatal and nonfatal major IHD events, obtained from death certificates and medical records and confirmed using physician questionnaires.

Main results

At baseline, 25% of the men had evidence of IHD, and 5.5% had had an MI. 488 major IHD events occurred during follow-up (217 fatal, including 117 sudden deaths, and 271 nonfatal). Men with a higher heart rate tended to be older and heavier, with higher blood pressure, blood cholesterol, blood glucose, and triglyceride levels (P < 0.01 for each). For men with a resting heart rate ≥ 90 and no baseline evidence of IHD, the relative risk (RR) was increased for all IHD events (age-adjusted RR 1.7, 95% CI 1.1 to 2.5), for IHD mortality (age-adjusted RR 3.2, CI 1.9 to 5.5; RR adjusted for all other factors 2.0, CI 1.2 to 3.6), and for sudden cardiac death (age-adjusted RR 4.4, CI 2.2 to 8.7; RR adjusted for all other factors 2.7, CI 1.3 to 5.4). Men with preexisting evidence of IHD and a resting heart rate ≥ 90 had a higher risk for all IHD events (age-adjusted RR 1.5, CI 1.0 to 2.2) and for IHD mortality (age-adjusted RR 2.1, CI 1.3 to 3.3; RR adjusted for all other factors 2.0, CI 1.2 to 4.9).

Conclusions

Middle-aged men with a high resting heart rate had an increased risk for fatal and nonfatal ischemic heart disease events. Men with a high heart rate and no baseline evidence of ischemic heart disease also had an increased risk for sudden cardiac death.

Sources of funding: British Heart Foundation; Department of Health; The Stroke Association.

For article reprint: Dr. A.G. Shaper, Department of Public Health and Primary Care, Royal Free Hospital School of Medicine, Rowland Hill Street, London NW3 2PF, England, United Kingdom. FAX 44-181-959-8742.


Commentary

Prospective studies have shown an association between resting heart rate and cardiovascular morbidity and all-cause mortality. This relation persists after adjustment for known risk factors for IHD and death. The increased risk is most consistently seen among middle-aged and elderly white men. This British study provides additional evidence that elevated resting heart rate is an independent risk factor for IHD and sudden cardiac death in middle-aged men.

Shaper and colleagues provide follow-up data on morbidity and mortality for men 40 to 59 years of age who were divided into 5 groups using their baseline resting heart rate. This prospective design allows standardization of the outcome assessments. The study groups, however, may not be comparable regarding all the important prognostic factors because heart rate was not under the control of the investigators. Although men known to be taking antihypertensive therapy were analyzed separately, little is known about baseline medications. The lower rates of mortal and morbid events in those with lower heart rates could have been caused by heart-slowing medications.

As yet, no experimental evidence exists suggesting that lowering the heart rate reduces the frequency of IHD or sudden death in persons without preexisting IHD. The results of this and similar studies published over the past 30 years, however, indicate that the association between resting heart rate and IHD is strong and consistent among studies. In addition, the association exhibits a dose-response gradient and makes biological sense. Although the implications of this association for the management of patients are uncertain, it will be interesting to follow investigators in their attempts to determine the mechanisms by which elevated heart rate predisposes to fatal and nonfatal IHD.

Allan D. Kitching, MSc, MD
The Toronto HospitalToronto, Ontario, Canada


Authors' Response

Heart rate was measured using standardized conditions and adjusting for several confounding factors. The suggestion that heart-slowing drugs may have been responsible for lower event rates is unlikely because men with preexisting IHD were excluded from this analysis and those on antihypertensive medication were classified as having hypertension.