Editorial for “Assessment of Myocardial Microvascular Function in Athletes Using Resting Cardiac Magnetic Resonance First‐Pass Perfusion”

Physical exercise is generally beneficial for human health [1-4]. Intense regular physical exercise, however, can promote significant structural, functional, and electrical remodeling of the heart that is referred to as “athlete's heart” [5]. While this remodeling of the heart—which includes ventricular enlargement and wall thickening—is generally beneficial to meet increased hemodynamic demand from intense exercise, it may also increase the risk of adverse conditions such as myocardial fibrosis and sudden cardiac death [6, 7]. A better understanding of the myocardial microcirculation in athletes may allow for improved prediction of adverse cardiac remodeling, myocardial fibrosis, and sudden cardiac death. In this issue of the Journal of Magnetic Resonance Imaging, Liu and coauthors [8] report the association of resting cardiac first-pass MRI perfusion parameters in athletes to cardiac remodeling and myocardial fibrosis. In 186 athletes prospectively recruited into their single-center study, Liu and coauthors [8] found that athletes demonstrated a reduced resting first-pass MRI perfusion upslope, decreased maximum signal intensity, and increased time-to-maximum signal intensity than a control group of sedentary office workers. The authors also found that male athletes with cardiac remodeling and/or myocardial fibrosis had a lower upslope and maximum signal intensity, and a larger time-to-maximum signal intensity than male athletes without such findings. Additionally, perfusion parameters within athletes demonstrated a negative correlation with myocardial T2 mapping, QRS interval, and corrected QT interval, suggesting an association with tissue and electrophysiologic changes. A prediction model for cardiac remodeling and myocardial fibrosis was constructed that provided a substantial area under the curve of 0.837. Lastly, the authors found no change in clinical symptoms or pathologic cardiac MRI findings over a 1-year follow-up period. The work of Liu and coauthors [8] has a number of strengths. First, the study involved a sizable number of athletes engaged in ≥ 6 h of exercise per week over a period of ≥ 3 years, as well as a sedentary control group. Second, two experienced cardiac MRI radiologists served as readers, and intra-observer and inter-observer variability revealed good-to-excellent agreement between readers. Third, the study used a 16-segment model based on three MRI slices, revealing which myocardial segments and perfusion parameters were independently associated with cardiac remodeling and myocardial fibrosis. Liu and coauthors [8] found that resting first-pass MRI perfusion upslope in mid-ventricular segments showed the strongest association with cardiac remodeling and myocardial fibrosis. Fourth, MRI perfusion parameters were correlated with myocardial and electrophysiological markers. Lastly, the nomographic model that was developed for predicting cardiac remodeling or myocardial fibrosis demonstrated relatively good area-under the curve, sensitivity, and specificity metrics (values of 0.837, 0.737, and 0.845, respectively). Study limitations include that no female athletes showed myocardial remodeling or myocardial fibrosis. The nomographic model that was presented was developed exclusively from data obtained in male athletes. In addition, no changes in clinical symptoms or cardiac pathology were found for over the one-year follow-up period. Consequently, the predictive potential of the evaluated first-pass MRI perfusion parameters for future pathologic changes could not be assessed. Moreover, the practical value of using first-pass rest perfusion parameters to predict the presence of adverse remodeling and myocardial fibrosis may be limited, given that both can be readily assessed using regular structural, cine, and delayed enhancement protocols that comprise the standard cardiac MRI examination. Quantitative myocardial perfusion (e.g., in units of milliliters of blood per minute per gram of tissue) was not assessed. The semi-quantitative perfusion measures evaluated in the study may vary with imaging protocol parameters. Future studies may benefit from the use of quantitative myocardial MRI perfusion methods, inclusion of stress perfusion, and additional myocardial tissue characterization via T1 mapping. In conclusion, the interesting study of Liu and coauthors [8] probed differences in the myocardial microcirculation of athletes versus sedentary controls, and identified resting first-pass MRI perfusion parameters that were associated with cardiac remodeling and myocardial fibrosis in male athletes. In particular, the study found that resting first-pass MRI perfusion upslope in mid-ventricular segments showed the strongest association with cardiac remodeling and myocardial fibrosis in male athletes. Future work will be needed to validate these findings and determine whether such resting first-pass myocardial perfusion parameters improve prognostic risk assessment in athletes.