Background Low resting heart rate and premature atrial contractions (PACs) predict incident atrial fibrillation (AF) and could be interdependent, since PACs occur in the gaps between normal beats.
Objective To study the association between low heart rate at 24hECG, PACs and incident AF in a prospective population-based cohort.
Methods In the Malmö Diet and Cancer study, 24hECGs were performed in 377 AF-free subjects. The endpoint was clinical AF retrieved from national hospital (mean follow-up 17 years). The interaction between increased supraventricular activity (SVA) top quartile of either PACs/hour or supraventricular tachycardias/hour) and mean heart rate (mHR) as regards AF risk was assessed in multivariable Cox regression analyses adjusted for age, sex, height, BMI, systolic blood pressure, antihypertensive medication, smoking and homeostasis model assessment of insulin resistance.
Results There were 80 (21%) incident cases of AF. Below median mHR (80 bpm/75 bpm for women/men) was associated with increased AF incidence (HR: 1.89, 95% CI 1.18 to 3.02, p=0.008). There was no correlation between mHR and SVA (p=0.6) or evidence of a multiplicative interaction between these factors for AF risk (p for interaction=0.6) In the group with both increased SVA and below median mHR (17% of the population) the relative risk of AF was very high (HR 4.5, 95% CI 2.2 to 9.1, p=0.001).
Conclusion Low mHR at 24hECG independently predicts AF, but there is no association between mHR and SVA, and these factors are independent as regards AF risk. Subjects with both low mHR and increased SVA have high AF risk.
- atrial fibrillation
- supraventricular ectopy, premature atrial contraction
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Contributors APP has performed analyses and drafted the manuscript. LSBJ has conceived of the study, supervised analyses and critically revised manuscript. GE, BH and AF have supervised analyses and critically revised manuscript. SJ-M and MP have participated in data collection and revised the manuscript.
Funding LSBJ is supported by governmental funding within the Swedish National Health Services. AF, GE and LSBJ are supported by the Swedish Heart and Lung Foundation.
Competing interests SJ-M is a previous medical director of Cardiome Inc.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No data are available.