BOSTON — Relatively small changes in heart rate over time, even within the normal range, are associated with a higher risk for adverse CV and non-CV outcomes in the general population, a new study shows.[1]
For each 5-beat-per minute (bpm) increase in heart rate from the preceding office visit, the risk increased 12% for all-cause mortality, 13% for incident heart failure, 9% for MI, and 6% for stroke.
Similarly, risk rose 13% for CV death, 12% for non-CV death, and 8% for cancer with each 5-bpm increase in heart rate, according to the study, published January 24 in JAMA Cardiology.
“One of the most important lessons from this is that even in relatively healthy community-based cohorts, this particular biomarker, which is both easy to measure and essentially free, is extremely potent and extremely powerful as a predictor,” senior author, Scott D. Solomon (Brigham and Women’s Hospital, Boston), said. “I think it will reinforce the need to pay attention to those changes.”
The results are in keeping with longitudinal studies in individuals without known CV disease and a recent report by the team, in which higher resting heart rate and temporal changes in heart rate were associated with worse outcomes in patients with heart failure with preserved ejection fraction in the TOPCAT trial.
“The new data extends this concept not just to patients with heart failure but to a much more general community of patients,” he said.
The investigators, led by Dr Ali Vazir (Brigham and Women’s Hospital), used electrocardiogram data from 15,680 participants in the multiethnic Atherosclerosis Risk in Communities (ARIC) study to assess resting baseline heart rate, time-updated heart rate, and changes in heart rate from the preceding visit. Changes in heart rate were calculated—not just between two points, as is typically done, but between four office visits, with a median interval between visits of 3 years. Outcome events were tracked over 28 years of follow-up.
At the first office visit, roughly a third of participants had hypertension, one quarter smoked, and use of heart rate-limiting drugs, such as β-blockers, calcium antagonists, and digoxin, was reported by 10.5%, 3.4%, and 1.6%, respectively. More than half (55.2%) of participants were women, 26.9% were African American, and the mean heart rate was 67 bpm.
As a continuous covariate in adjusted analyses, increases in heart rate from the preceding visit were associated with all outcomes. The results also showed a near-linear relationship between change in heart rate and all-cause mortality and incident heart failure, such that any rise in heart rate greater than 1 bpm from the preceding office visit appears to increase the risk significantly, the authors write.
Although heart rate is an integral part of the physical exam, “I think we tend not to pay tremendous attention to it unless it falls dramatically outside the normal rate,” Solomon said.
“A resting heart rate that has gone from 60 to 75 over a period of a year or two, we might not pay attention to at all but if there has been a change over that time, these data suggest that kind of a change would portend worse prognosis for those patients,” he added.
Notably, any drop in heart rate from the preceding visit was significantly associated with lower risk for all-cause mortality, while a drop of more than 12 bpm was significantly associated with lower heart failure risk.
Temporal increases in heart rate over time may reflect increased sympathetic activity, while lower heart rate may reflect improved cardiac function, physical fitness, or lower sympathetic tone, the authors suggest.
That said, “I don’t want to give the impression that it’s just elevation in heart rate that’s bad; sometimes reduction in heart rate can be bad,” Solomon remarked. “There can certainly be people who have heart rates that are too low, and that’s a measure of conduction system disease and in extreme cases can require pacemaker therapy.”
The authors also point out that heart rate–limiting drugs may explain reductions in heart rate, especially as β-blocker use was more frequent over the study. By visit 4, the percentage of patients reporting use of β-blockers, calcium antagonists, and digoxin increased to 12.8%, 13.2%, and 2.5%, respectively.
β-Blocker use at any time during the study attenuated the relationship between change in heart rate and time-updated heart rate and all-cause mortality, so that it was no longer significant.
The reason for this is not clear. “This finding is not in keeping with results in our group’s previous analyses of patients with HF with preserved or reduced ejection fraction,” the authors write.
As with other epidemiology studies, the analysis cannot determine causality, Solomon said. Nevertheless, it does make a case for improving CV fitness through exercise and tracking results with wearable devices, such as the Apple Watch and Fitbit devices.
“The exciting thing about this whole area is that we now have all these devices that are becoming both inexpensive and accurate that can look at heart rate over time and in relation to activity,” he said. “I suspect that it’s only a very short period of time when this kind of information will be available to our physicians, and we’ll be able to actually look at real trends in heart rate in patients and use this biomarker in a more meaningful way.”
The ARIC study was supported by National Heart, Lung, and Blood Institute. Solomon reports Amgen research grants. Vazir was funded by the Royal Brompton and Harefield Hospital National Health Service Foundation Trust and Brigham and Women’s Hospital.
Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.
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