Exercise-Induced Cardiac Remodeling: Competitive Athletes Are Just the Tip of the Iceberg.

Aaron L Baggish

doi:10.1161/circimaging.116.005321

Aaron L Baggish

Open Access

https://doi.org/10.1161/circimaging.116.005321

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Abstract

Cardiac enlargement among trained athletes was first documented more than a century ago. Since the pioneering work of Henschen and Darling,1,2 both visionary investigators who independently and nearly simultaneously described enlarged cardiac silhouettes among Nordic skiers and rowers, respectively, much has been learned about the relationship between vigorous exercise and cardiac structure and function. Several decades of cross-sectional studies using multimodality noninvasive imaging techniques have established characteristic features of the athlete’s heart including balanced biventricular dilation,3,4 mild-to-moderate increases in left ventricular wall thickness,5 and biatrial dilation.6,7 More recently, carefully conducted longitudinal studies have established a cause and effect relationship between exercise training and cardiac remodeling.8–11 The term exercise-induced cardiac remodeling (EICR), now in widespread use, encompasses the many structural and functional adaptations that occur in response to routine exercise training.12 In clinical practice, findings consistent with EICR are the norm, not the exception, and should be viewed as adaptive physiology rather than subclinical disease among asymptomatic competitive athletes. It must, however, be emphasized that exercise, the stimulus for EICR, is not a binary factor but rather a continuous and complex variable that is defined by the cross product of intensity, frequency, and duration.13 In between sedentary living, perhaps our greatest contemporary public health threat, and competitive athletics exists a broad exercise dose range. To date, the vast majority of previous EICR studies have examined elite or subelite athlete cohorts with individuals who exercise at a minimum of 10 hours per week and routinely include high-intensity efforts to prepare for competitions. As such, comparatively little is known about cardiac adaptation among the much larger segment of the general population that exercises at less extreme doses. To what degree …

Highlights

The opinions expressed in this article are not necessarily those of the editors or of the American Heart Association
Using models that adjusted for age, sex, ethnicity, systolic blood pressure, and ethnicity, increasing physical activity was significantly associated with increasing left ventricular mass index, increasing left and right ventricular end-diastolic volume index, and increasing left and right ventricular indexed stroke volume
Clinical cut points defining left ventricular hypertrophy and biventricular dilation were exceeded by significant numbers of participants in the highest 2 exercise dose categories with 42% and 22.2% of category IV participants meeting criteria for right and left ventricular dilation, respectively

Summary

Introduction

In this issue of Circulation: Cardiovascular Imaging, Dawes et al[14] present a valuable data set that begins to examine the relationship between intermediate doses of exercise (ie, exercise doses less than those typical of competitive athletes) and cardiac variable. Using a sizable cohort of healthy adult volunteers (n=1096; 54% female; median age: 39.2 years; ≈ 80% white) recruited through the UK Digital Heart Project, the investigators measured conventional parameters of left and right ventricular structure using cardiac magnetic resonance imaging. These findings remain consistent using models that excluded participants in the highest exercise quintile (ie, exercise >5 hours per week) to ensure that they were not exclusively driven by the inclusion of any true competitive athletes.

Results

Conclusion