Fitness Linked to Lower Ventricular Arrhythmia Risk Later

April 26, 2019

Objectively measured cardiorespiratory fitness (CRF) in middle-aged men is inversely related to their risk for serious ventricular arrhythmias over the subsequent decades, independent of other cardiovascular risk factors, conclude researchers based on a prospective longitudinal cohort study.

Previous studies have demonstrated links between CRF and acute myocardial infarction (MI), stroke, heart failure, and mortality in general, but the current analysis is likely the first to prospectively show the association with ventricular tachycardia (VT) or ventricular fibrillation (VF), notes their report, published online March 29 in Mayo Clinic Proceedings.

That better aerobic fitness apparently protects against potentially fatal arrhythmias in the future, and that it can be easily assessed clinically during an exercise test, supports respiratory gas exchange measurement of CRF as a routine part of patient assessments, lead author Jari A. Laukkanen, MD, PhD, University of Jyväskylä, Finland, told theheart.org | Medscape Cardiology.

"Cardiorespiratory fitness should be considered a vital sign and should be measured in clinical practice, because it can provide health professionals with further information to improve the management of patients and encourage lifestyle strategies that can reduce cardiovascular disease risk," he and his colleagues write.

It's a limitation of the analysis, Laukkanen acknowledged, that the cohort, consisting of 2299 men initially aged 42 to 61 years in the Kuopio Ischemic Heart Disease Risk Factor Study, was not ethnically diverse, nor did it include women, shortfalls that should be explored in future studies.

Maximal oxygen uptake was measured at baseline at a mean participant age of 53; their mean age-adjusted CRF was 30.2 mL/kg per min.

A randomly selected subset of 576 men underwent CRF evaluation 11 years after their baseline assessment, which allowed the analysis to correct for within-person variability in CRF levels over time, the report states.

Over a median 25.3 years through the end of 2013, 73 serious ventricular arrhythmias, that is, episodes of sustained or nonsustained VT or VF, were detected for an annual rate of 1.44 per 1000 person-years.

Association Between CRF and Risk for Serious Ventricular Arrhythmias, by Standard Deviation (SD) and by CRF Tertile
  Hazard Ratio (95% CI) P Value
Comparison Multivariate Model 1 Multivariate Model 2
Per 1-SD increase in baseline CRF 0.68 (0.51–0.91) .009 0.67 (0.51–0.88) .004
Tertile 3 vs tertile 1 for baseline CRF 0.33 (0.16–0.69) .003 0.32 (0.15–0.65) .002
Per 1-SD increase in usual CRF 0.52 (0.32–0.85) .009 0.50 (0.31–0.80) .004
Tertile 3 vs tertile 1 for usual CRF 0.15 (0.04–0.53) .009 0.14 (0.04–0.48) .002
Usual CRF accounts for CRF variation across two assessments 11 years apart in a randomly selected subset of 576 participants.
Multivariate model 1: adjusted for age, systolic blood pressure, prevalent coronary heart disease, smoking status, and history of diabetes.
Multivariate model 2: adjusted for age, history of hypertension, total cholesterol level, alcohol consumption, and physical activity.

To be included in the analysis, the arrhythmias had to be electrocardiographically documented in the hospital or clinic, or recorded by an implanted rhythm-management device, Laukkanen explained in an interview.

In multiple adjusted models, increasing CRF was associated with reduced risk for VT/VF over the follow-up, and participants in the highest CRT tertile showed a significant drop in risk compared with those in tertile 1. That was true whether or not the analysis was further adjusted for within-person variability in CRF over time.

In general, ventricular arrhythmia risk was not significantly lower for patients in CRT tertile 2 compared with tertile 1.

Laukkanen and the other authors reported no conflicts.

Mayo Clin Proc. Published online March 29, 2019. Abstract

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