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Resting heart rate as a low tech predictor of coronary events in women: prospective cohort study

BMJ 2009; 338 doi: https://doi.org/10.1136/bmj.b219 (Published 04 February 2009) Cite this as: BMJ 2009;338:b219

Rapid Response:

So what about heart rate variability.....?

I propose short-term assessment of heart rate variability (HRV) as a
more reliable measure of autonomic nervous system function than
measurement of resting heart rate.

Whilst heart rate is an easy variable to measure it is dependent on a
multitude of factors and inherently dynamic. Consequently, the assumption
of the authors that heart rate is a good marker of sympathetic tone can in
certain circumstances be misleading (1). The authors mention HRV only
briefly in their discussion of their findings in relation to depression.
HRV is largely determined by vagally mediated beat to beat variability,
conventionally known as respiratory sinus arrhythmia. HRV is primarily a
marker of activity in cardiac vagal motor neurons originating from the
nucleus ambiguus within the brainstem. It is a powerful and independent
predictor of an adverse prognosis in patients with heart disease as well
as in the general population (2). Along with heart rate, it too is easy to
measure, inexpensive and only minimally more invasive. HRV analysis has
recently been reviewed and reliability indexes tend to improve during
paced breathing (3).

It is more than likely that those women with higher resting heart
rates would have exhibited reduced HRV and so predict myocardial infarct
or coronary death. As with heart rate, it is still unclear whether the
relationship between measures of cardiac vagal control and mortality is
causative or mere association.

Mechanisms by which cardiac vagal activity may enhance prognosis
include a decrease in myocardial oxygen demand, an attenuation in
sympathetic activity and a reduced susceptibility of the myocardium to
ventricular tachycardia. In animals, augmentation of cardiac vagal control
by nerve stimulation or by drugs is associated with a reduction in sudden
death in susceptible models. In humans, a number of drugs including ACE
inhibitors and beta-blockers which have evidence for reducing mortality
and sudden death in large randomised trials can also be demonstrated to
increase HRV (1).

References.

1. Resting heart rate as a low tech predictor of coronary events in
women: prospective cohort study. Hsia J, Larson JC, Ockene JK et al. BMJ
2009; 338: b219.

2. Heart rate variability – a therapeutic target? Routledge HC,
Chowdhary S, Townend JN. J Clin Pharm Ther. 2002;27: 85-92. Review.

3. Heart rate variability measures: a fresh look at reliability.
Pinna GD, Maestri R, Torunski A et al. Clin Sci (Lond). 2007; 113: 131-40.

Competing interests:
None declared

Competing interests: No competing interests

19 March 2009
William E Moody
Cardiology ST2 Trainee
Solihull Hospital, B91 2JL