Myocardial fatigue in recreational marathon runners: A speckle-tracking echocardiography study

Abstract

BackgroundProlonged aerobic exercise such as marathon running produces supraphysiological hemodynamic stress that can potentially affect the athlete's cardiac homeostasis. While cardiac structural and functional adaptations in professional athletes are well characterized, only a limited information is available for recreational runners undergoing this supraphysiological stress.MethodsPremarathon and post-marathon echocardiography was performed in 50 recreational marathon runners [age 40.8 ± 7.5 years, 44 (88%) males; running distance 42.195 km]. All the runners received 4-month training for the marathon. The baseline echocardiogram and N-terminal B-type natriuretic peptide (NT-proBNP) were obtained before training, whereas the post-marathon study was performed within 10 days (7.27 ± 0.92 days) of completion of marathon. Two-dimensional speckle-tracking echocardiography was used for characterizing the changes in myocardial mechanics.ResultsThere was a significant reduction in heart rate post-marathon, whereas the levels of NT-proBNP increased significantly (86.0 ± 9.5 pg/ml vs 106.5 ± 24.2 pg/ml, p = 0.001). The left ventricular (LV) end-diastolic volume (61.8 ± 16.5 ml vs 72.8 ± 5.1 ml, p < 0.001), LV mass (120.2 ± 30.0 gm vs 160.3 ± 43.0 gm, p < 0.001), and LV ejection fraction (64.9 ± 5.6% vs 72.0 ± 5.7%, p < 0.001) also increased significantly. However, there was a significant attenuation in LV global longitudinal (−19.3 ± 2.71% vs −16.5 ± 4.6%, p = 0.003) and circumferential strain (−17.2 ± 2.41% vs −15.2 ± 2.6%, p = 0.001) post-marathon. The LV global radial strain showed a nonsignificant reduction.ConclusionRecreational marathon runners have reduced longitudinal and circumferential shortening of the left ventricle with elevation of NT-proBNP. However, the LV ejection performance remains maintained because of an increase in the LV end-diastolic volume and mass. These changes suggest the possibility of “myocardial fatigue” occurring in response to supraphysiological hemodynamic stress of marathon running.

Post-exertional increase in first-phase ejection fraction in recreational marathon runners

“…In line with previous observations reporting changes in LV diastolic function in the absence of a change in conventional measures of systolic function, 6,7,9,26 we observed a decrease in E wave, E/A ratio and E 0 , while E/E 0 increased. This may suggest an attenuation of early LV filling although this alone may not represent a diastolic impairment in otherwise normal heart.…”

Reversible left ventricular diastolic dysfunction—Overview and clinical implications

“…The effect of exercise on diastolic function has also been reported in recreational runners 53,57,58 . These studies have consistently demonstrated transient impairment in LV diastolic function (a variable combination of reduced mitral E velocity, increased A and E / A ratio, and reduced or unchanged e ′ velocity) after prolonged exercise (ie, more than 2 hours).…”

“…There have been reports suggesting that intense exercise can result in a transient deterioration of LV systolic and diastolic function in subjects with an otherwise normal heart. 53,54 The duration of these changes is variable, ranging from a few days to 1 month and the reversal of these alterations during recovery has suggested the term “cardiac fatigue” 55 …”

“…It has been suggested that reduced LV preload associated with acute volume loss (eg, postexercise dehydration) might explain the decrease in early diastolic flow velocity after prolonged exercise, which may be reversed by rehydration. However, other investigators challenged this hypothesis and indicated myocardial dysfunction as a key player in this setting 53 …”

“…Clinical implications The increasing popularity of recreational marathon running, exposing subjects with different levels of physical training to supraphysiological stress requires better characterization of cardiac structural and functional alterations occurring in response to such forms of stress. 53 Since an impairment in LV myocardial mechanics has been demonstrated in healthy individuals participating in strenuous or prolonged exercise, future studies are needed to understand the duration of training required for recreational runners 53 . Further studies are also needed to clarify the mechanisms and reversibility of such myocardial dysfunction.…”