Diverse patterns of myocardial fibrosis in lifelong, veteran endurance athletes

The U-shaped relationship between exercise and cardiac morbidity

Exercise confers a plethora of health benefits that are well documented, whereas physical inactivity is a leading risk factor for cardiovascular morbidity and mortality. The dose of physical activity required to achieve these benefits is relatively modest and equates to jogging at a pace of 15min per mile for 20-30min daily. In the current era, most athletes engage in a volume and intensity of exercise that is at least 5-10-fold greater than the general recommendations for physical activity. Such practice is evidenced by the fact that many sportsmen have achieved athletic feats that were considered impossible only 2 decades ago. Numerous studies in retired athletes have consistently shown a reduced incidence of heart disease and an increased longevity of life. Occasionally, however, intense exercise is associated with sudden deaths in athletes harboring quiescent yet potentially sinister cardiac diseases. Despite the visibility afforded by such catastrophes, the reputation of exercise remains unscathed because most deaths can be accounted for by an underlying cardiac abnormality where exercise is a mere trigger for a fatal arrhythmia rather than the actual cause of death. More recently, there have been an emerging number of reports suggesting that intense exercise may have an adverse impact on an otherwise normal heart. This article will review the morbidity and mortality associated with sport and pose the question whether one can have "too much of a good thing."

Cardiovascular Adaptation and Remodeling to Rigorous Athletic Training

Exercise-induced cardiac remodeling is a complex process by which the cardinal hemodynamic stresses of pressure and volume lead to a host of structural or functional adaptations. In aggregate, the constellation of changes that accompany this process serve to facilitate athletic performance by minimizing the cardiac work inherent in athletic activity. Although several key determinants of athletic cardiac adaptation have been described, observed variability across athlete cohorts remains an incompletely understood area. Ongoing and future work are required to further understand this process and ultimately to determine where the boundary lies between adaptive physiology and maladaptive disease.

Sex differences in cardiac function after prolonged strenuous exercise

OBJECTIVE

To evaluate sex differences in left ventricular (LV) function after an ultramarathon, and the association of vascular and training indices with the magnitude of exercise-induced cardiac fatigue.

DESIGN

Descriptive field study.

SETTING

Fat Dog 100 Ultramarathon Trail Race, Canada.

PARTICIPANTS

Thirty-four (13 women) recreational runners (aged 28-56 years).

INTERVENTIONS

A 100-km or 160-km mountain marathon.

MAIN OUTCOME MEASURES

Baseline baroreceptor sensitivity, heart rate variability, and arterial compliance; Pre-exercise and postexercise echocardiographic evaluations of LV dimensions, volumes, Doppler flow velocities, tissue velocities, strain, and strain rate.

RESULTS

Finishers represented 17 men (44.8 ± 6.6 years) and 8 women (45.9 ± 10.2 years; P = 0.758). After ultraendurance exercise, significant reductions (P < 0.05) in fractional shortening (men: 40.9 ± 6.9 to 34.1 ± 7.6%; women: 42.5 ± 6.5 to 34.6 ± 7.9%) diastolic filling (E/A, men: 1.28 ± 0.68 to 1.26 ± 0.33; women: 1.55 ± 0.51 to 1.30 ± 0.27), septal and lateral tissue velocities (E'), and longitudinal strain (men: -21.02 ± 1.98 to -18.44 ± 0.34; women: -20.28 ± 1.90 to -18.44 ± 2.34) were observed. Sex differences were found for baseline cardiac structure and global function, peak late transmitral flow velocity, and estimates of LV filling pressures (P < 0.05). Regression analysis found that higher baseline arterial compliance was associated with lower reductions in cardiac function postexercise, to which sex was a significant factor for E' of the lateral wall. Faster race pace and greater lifetime ultramarathons were associated with lower reductions in LV longitudinal strain (P < 0.05).

CONCLUSIONS

Cardiac responses after an ultramarathon were similar between men and women. Greater evidence of exercise-induced cardiac fatigue was found to be associated with lower baseline arterial compliance and training status/experience.

CLINICAL RELEVANCE

These findings suggest that vascular health is an important contributor to the degree of cardiovascular strain incurred as the result of an acute bout of prolonged strenuous exercise.

Physiologic and pathophysiologic changes in the right heart in highly trained athletes

Exercise causes changes in the heart in response to the hemodynamic demands of increased systemic and pulmonary requirements during exercise. Understanding these adaptations is of great importance, since they may overlap with those caused by pathological conditions. Initial descriptions of athlete's heart focused mainly on chronic adaptation of the left heart to training. In recent years, the substantial structural and functional adaptations of the right heart have been documented, highlighting the complex interplay with left heart. Moreover, there is evolving evidence of acute and chronic cardiac damage, mainly involving the right heart, which may predispose subjects to atrial and ventricular arrhythmias, configuring an exercise-induced cardiomyopathy. The aim of this article is to review the current knowledge on the physiologic and pathophysiologic changes in the right heart in highly trained athletes.

Rationale and design of the Measuring Athlete's Risk of Cardiovascular events (MARC) study : The role of coronary CT in the cardiovascular evaluation of middle-aged sportsmen

Background

More than 90 % of exercise-related cardiac arrests occur in men, predominantly those aged 45 years and older with coronary artery disease (CAD) as the main cause. The current sports medical evaluation (SME) of middle-aged recreational athletes consists of a medical history, physical examination, and resting and exercise electrocardiography. Coronary CT (CCT) provides a minimally invasive low radiation dose opportunity to image the coronary arteries. We present the study protocol of the Measuring Athlete’s Risk of Cardiovascular events (MARC) study. MARC aims to assess the additional value of CCT to a routine SME in asymptomatic sportsmen ≥45 years without known CAD.

Design

MARC is a prospective study of 300 asymptomatic sportsmen ≥45 years who will undergo CCT if the SME does not reveal any cardiac abnormalities. The prevalence and determinants of CAD (coronary artery calcium score ≥100 Agatston Units (AU) or ≥50 % luminal stenosis) will be reported. The number needed to screen to prevent the occurrence of one cardiovascular event in the next 5 years, conditional to adequate treatment, will be estimated.

Discussion

We aim to determine the prevalence and severity of CAD and the additional value of CCT in asymptomatic middle-aged (≥45 years) sportsmen whose routine SME revealed no cardiac abnormalities.

Electronic supplementary material

The online version of this article (doi:10.1007/s12471-014-0630-0) contains supplementary material, which is available to authorized users.

The response of the pulmonary circulation and right ventricle to exercise: exercise-induced right ventricular dysfunction and structural remodeling in endurance athletes (2013 Grover Conference series)

There is unequivocal evidence that exercise results in considerable health benefits. These are the result of positive hormonal, metabolic, neuronal, and structural changes brought about by the intermittent physiological challenge of exercise. However, there is evolving evidence that intense exercise may place disproportionate physiological stress on the right ventricle (RV) and the pulmonary circulation. Both echocardiographic and invasive studies are consistent in demonstrating that pulmonary arterial pressures increase progressively with exercise intensity, such that the harder one exercises, the greater the load on the RV. This disproportionate load can result in fatigue or damage of the RV if the intensity and duration of exercise is sufficiently prolonged. This is distinctly different from the load imposed by exercise on the left ventricle (LV), which is moderated by a greater capacity for reductions in systemic afterload. Finally, given the increasing RV demand during exercise, it may be hypothesized that chronic exercise-induced cardiac remodeling (the so-called athlete's heart) may also disproportionately affect the RV. Indeed, there is evidence, although somewhat inconsistent, that RV volume increases may be relatively greater than those for the LV. Perhaps more importantly, there is a suggestion that chronic endurance exercise may cause electrical remodeling, predisposing some athletes to serious arrhythmias originating from the RV. Thus, a relatively consistent picture is emerging of acute stress, prolonged fatigue, and long-term remodeling, which all disproportionately affect the RV. Thus, we contend that the RV should be considered a potential Achilles' heel of the exercising heart.

Right Ventricular Changes in Highly Trained Athletes: Between Physiology and Pathophysiology

Several studies have described the adaptive remodeling of the heart during exercise. In some more practiced endurance athletes, there is a disproportionate load on the right ventricle (RV), at least during exercise, and this might be the basis for a chronic pro-arrhythmic RV remodeling. Especially, in these kinds of athletes the recovery after detraining might be incomplete, in particular for RV changes. The observation of acute myocardial injury based on transient elevation of biomarkers and chronic myocardial scar, not completely reversible changes of the RV and an increased prevalence of some arrhythmias support the existence of an “exercise-induced cardiomyopathy.” The aim of this paper is to review current knowledge about changes in the right heart in highly trained athletes and how these change influence cardiac function.

What do we know about the cardiac benefits of exercise?

Exercise has long been considered an essential element for sustaining cardiovascular health. A vast literature of clinical studies suggests that exercise serves as an effective intervention for the primary and secondary prevention of cardiovascular disease, although the optimal nature, intensity, and duration of exercise for maximizing these cardiovascular benefits remain unclear. On a molecular level, exercise induces physiologic growth of the heart primarily by driving cardiomyocyte hypertrophy, notably through the interconnected IGF-1-PI3K-AKT1 and C/EBPβ-CITED4 pathways. Here, we explore the range of clinical evidence supporting the cardiovascular benefits of exercise and outline the molecular pathways that play major roles in regulating these protective effects.

Endurance sport and "cardiac injury": a prospective study of recreational ironman athletes

BACKGROUND

Participation in triathlon competitions has increased in recent years. Many studies have described left or right ventricular injury in endurance athletes. The goal of this study was to examine the right and left ventricular cardiac structures and function and dynamic cardio-pulmonary performance in a large cohort of middle- and long-distance triathletes.

METHODS

87 triathletes (54 male and 33 female) were examined using spiroergometry and echocardiography. The inclusion criterion was participation in at least one middle- or long distance triathlon.

RESULTS

Male triathletes showed a maximum oxygen absorption of 58.1 ± 8.6 mL/min/kg (female triathletes 52.8 ± 5.7 mL/min/kg), maximum ergometer performance of 347.8 ± 49.9 W (female triathletes 264.5 ± 26.1 W). Left ventricular ejection fraction (EF) was normal (male triathletes EF: 61.9% ± 3%, female triathletes EF: 63.0% ± 2.7%) and systolic right ventricular area change fraction (RV AFC%) showed normal values (males RV AFC%: 33.5% ± 2.2%, females 32.2% ± 2.8%). Doppler indices of diastolic function were normal in both groups. With respect to the echocardiographic readings the left ventricular mass for males and females were 217.7 ± 41.6 g and 145.9 ± 31.3 g, respectively. The relative wall thickness for males was 0.50 ± 0.07, whereas it was 0.47 ± 0.09 for females. The probability of left ventricular mass >220 g increased with higher blood pressure during exercise (OR: 1.027, CI 1.002-1.052, p = 0.034) or with higher training volume (OR: 1.23, CI 1.04-1.47, p = 0.019).

CONCLUSIONS

Right or left ventricular dysfunction could not be found, although the maximal participation in triathlon competitions was 29 years. A left ventricular mass >220 g is more likely to occur with higher arterial pressure during exercise and with a higher training volume.

Increased cardiovascular disease mortality associated with excessive exercise in heart attack survivors

OBJECTIVE

To test whether greater exercise is associated with progressively lower mortality after a cardiac event.

PATIENTS AND METHODS

We used Cox proportional hazard analyses to examine mortality vs estimated energy expended by running or walking measured as metabolic equivalents (3.5 mL O2/kg per min per day or metabolic equivalent of task-h/d [MET-h/d]) in 2377 self-identified heart attack survivors, where 1 MET-h/d is the energy equivalent of running 1 km/d. Mortality surveillance via the National Death Index included January 1991 through December 2008.

RESULTS

A total of 526 deaths occurred during an average prospective follow-up of 10.4 years, 376 (71.5%) of which were related to cardiovascular disease (CVD) (International Statistical Classification of Diseases, 10th Revision codes I00-I99). CVD-related mortality compared with the lowest exercise group decreased by 21% for 1.07 to 1.8 MET-h/d of running or walking (P=.11), 24% for 1.8 to 3.6 MET-h/d (P=.04), 50% for 3.6 to 5.4 MET-h/d (P=.001), and 63% for 5.4 to 7.2 MET-h/d (P<.001) but decreased only 12% for ≥7.2 MET-h/d (P=.68). These data represent a 15% average risk reduction per MET-h/d for CVD-related mortality through 7.2 MET-h/d (P<.001) and a 2.6-fold risk increase above 7.2 MET-h/d (P=.009). Relative to the risk reduction at 7.2 MET-h/d, the risk for ≥7.2 MET-h/d increased 3.2-fold (P=.006) for all ischemic heart disease (IHD)-related mortalities but was not significantly increased for non-IHD-CVD, arrhythmia-related CVD, or non-CVD-related mortalities.

CONCLUSION

Running or walking decreases CVD mortality risk progressively at most levels of exercise in patients after a cardiac event, but the benefit of exercise on CVD mortality and IHD deaths is attenuated at the highest levels of exercise (running: above 7.1 km/d or walking briskly: 10.7 km/d).

Exercise-induced arterial hypertension - an independent factor for hypertrophy and a ticking clock for cardiac fatigue or atrial fibrillation in athletes?

Background : Exercise-induced arterial hypertension (EIAH) leads to myocardial hypertrophy and is associated with a poor prognosis. EIAH might be related to the "cardiac fatigue" caused by endurance training. The goal of this study was to examine whether there is any relationship between EIAH and left ventricular hypertrophy in Ironman-triathletes.

METHODS

We used echocardiography and spiroergometry to determine the left ventricular mass (LVM), the aerobic/anaerobic thresholds and the steady-state blood pressure of 51 healthy male triathletes. The main inclusion criterion was the participation in at least one middle or long distance triathlon.

RESULTS

When comparing triathletes with LVM <220g  and athletes with LVM >220g there was a significant difference between blood pressure values (BP) at the anaerobic threshold (185.2± 21.5 mmHg vs. 198.8 ±22.3 mmHg, p=0.037). The spiroergometric results were: maximum oxygen uptake (relative VO 2max) 57.3 ±7.5ml/min/kg vs. 59.8±9.5ml/min/kg (p=ns). Cut-point analysis for the relationship of BP >170 mmHg at the aerobic threshold and the probability of LVM >220g showed a sensitivity of 95.8%, a specificity of 33.3%, with a positive predictive value of 56.8 %, a good negative predictive value of 90%. The probability of LVM >220g increased with higher BP during exercise (OR: 1.027, 95% CI 1.002-1.052, p= 0.034) or with higher training volume (OR: 1.23, 95% CI 1.04 -1.47, p = 0.019). Echocardiography showed predominantly concentric remodelling, followed by concentric hypertrophy.

CONCLUSION

Significant left ventricular hypertrophy with LVM >220g is associated with higher arterial blood pressure at the aerobic or anaerobic threshold. The endurance athletes with EIAH may require a therapeutic intervention to at least prevent extensive stiffening of the heart muscle and exercise-induced cardiac fatigue.

[Perioperative management of atrial fibrillation]

Atrial fibrillation is a frequent complication in the perioperative period. When it appears there is an increased risk of perioperative morbidity due to stroke, thromboembolism, cardiac arrest, myocardial infarction, anticoagulation haemorrhage, and hospital readmissions. The current article focuses on the recommendations for the management of perioperative atrial fibrillation based on the latest Clinical Practice Guidelines on atrial fibrillation by the European Society of Cardiology and the Spanish Society of Cardiology. This article pays special attention to the preoperative management, as well as to the acute perioperative episode. For this reason, the latest recommendations for the control of cardiac frequency, antiarrhythmic treatment and anticoagulation are included.

Arterial stiffness results from eccentrically biased downhill running exercise

OBJECTIVES

There is increasing evidence that select forms of exercise are associated with vascular changes that are in opposition to the well-accepted beneficial effects of moderate intensity aerobic exercise. To determine if alterations in arterial stiffness occur following eccentrically accentuated aerobic exercise, and if changes are associated with measures of muscle soreness.

DESIGN

Repeated measures experimental cohort.

METHODS

Twelve (m=8/f=4) moderately trained (VO₂max=52.2 ± 7.4 ml kg(-1)min(-1)) participants performed a downhill run at -12° grade using a speed that elicited 60% VO₂max for 40 min. Cardiovascular and muscle soreness measures were collected at baseline and up to 72 h post-running.

RESULTS

Muscle soreness peaked at 48 h (p=<0.001). Arterial stiffness similarly peaked at 48 h (p=0.04) and remained significantly elevated above baseline through 72 h.

CONCLUSIONS

Eccentrically accentuated downhill running is associated with arterial stiffening in the absence of an extremely prolonged duration or fast pace. The timing of alterations coincides with the well-documented inflammatory response that occurs from the muscular insult of downhill running, but whether the observed changes are a result of either systemic or local inflammation is yet unclear. These findings may help to explain evidence of arterial stiffening in long-term runners and following prolonged duration races wherein cumulative eccentric loading is high.

Long-term follow-up of former world-class swimmers: evaluation of cardiovascular function

There is some evidence that long-term high-intensity endurance training might be associated with deterioration in cardiac function and might impose a potential risk for cardiovascular events. Thus, the intention was to retrospectively evaluate the cardiac status in former endurance athletes, particularly right ventricular (RV) dimension and function, to reveal potential cardiac damage. A group of 12 former world-class swimmers (45 ± 1.5 years) was examined 24.9 ± 4.3 years after cessation of high-intensity endurance training. They underwent history taking, physical examination, ECG, exercise testing and echocardiography. Furthermore, functional and echocardiography data that were also available from former evaluations were included in the analysis. There was a significant decline in exercise capacity. LV function was normal with a decrease in septal thickness to 9.1 ± 1.3 (p < 0.05) and LV diastolic diameter to 48.9 ± 5.6 (p < 0.05). Still, there was a remaining septal hypertrophy. RV function was 55.3 ± 4.2% and there were normal RV dimensions adjusted for body surface area. 25 years after the cessation of endurance training there was a normal RV and LV function with a normalization of almost all diameters, still there was a mild LV hypertrophy in some athletes. Consequently, no relevant long-term cardiac remodeling after intensive endurance training was depicted in this group of athletes.

Ventricular structure, function, and focal fibrosis in anabolic steroid users: a CMR study

PURPOSE

Anabolic steroid (AS) misuse is widespread amongst recreational bodybuilders; however, their effects on the cardiovascular system are uncertain. Our aim was to document the impact of AS use on cardiac structure, function and the presence of focal fibrosis using the gold standard cardiovascular magnetic resonance imaging (CMR).

METHODS

A cross-sectional cohort design was utilised with 21 strength-trained participants who underwent CMR imaging of the heart and speckle-tracking echocardiography. Thirteen participants (30 ± 5 years) taking AS for at least 2 years and currently on a "using"-cycle were compared with age and training-matched controls (n = 8; 29 ± 6 years) who self-reported never having taken AS (NAS).

RESULTS

AS users had higher absolute left ventricular (LV) mass (220 ± 45 g) compared to NAS (163 ± 27 g; p < 0.05) but this difference was removed when indexed to fat-free mass. AS had a reduced right ventricular (RV) ejection fraction (AS 51 ± 4 % vs. NAS 59 ± 5 %; p < 0.05) and a significantly lower left ventricular E':A' myocardial tissue velocity ratio [AS 0.99(0.54) vs. NAS 1.78(0.46) p < 0.05] predominantly due to greater tissue velocities with atrial contraction. Peak LV longitudinal strain was lower in AS users (AS -14.2 ± 2.7 % vs. NAS -16.6 ± 1.9 %; p < 0.05). There was no evidence of focal fibrosis in any participant.

CONCLUSIONS

AS use was associated with significant LV hypertrophy, albeit in-line with greater fat-free mass, reduced LV strain, diastolic function, and reduced RV ejection fraction in male bodybuilders. There was, however, no evidence of focal fibrosis in any AS user.

Cardiac imaging in evaluating patients prone to sudden death

Identifying subjects who are at risk for SCD and stratifying them correctly into low or high-risk groups is the holy grail of Cardiology. While imaging shows a lot of promise, it is plagued by the fact that most SCD occurs in relatively healthy subjects, a massive group who would not ordinarily be subjected to imaging. Left ventricular ejection fraction (LVEF) currently is our primary parameter for risk stratification for sudden cardiac death but is a poor marker with low sensitivity and specificity. Current data shows that sophisticated imaging with techniques, mainly Cardiac magnetic resonance Imaging (CMR), have the potential to identify novel high-risk markers underlying SCD, beyond ejection fraction. Imaging seems to further refine risk in patients with low LVEF as well as in those with normal EF; this is a major strength of advanced imaging. Clinical application has been slow and not fully prime time. It is important to remember that while promising, imaging techniques including CMR, have not been tested in rigorous prospective studies and thus have not as yet replaced EF as the gatekeeper to ICD implantation.

Effect of antioxidant supplementation on exercise-induced cardiac troponin release in cyclists: a randomized trial

Background

Cardiac troponin is the biochemical gold standard to diagnose acute myocardial infarction. Interestingly however, elevated cardiac troponin concentrations are also frequently observed during and after endurance-type exercise. Oxidative stress associated with prolonged exercise has been proposed to contribute to cardiac troponin release. Therefore, the aim of this study was to assess the effect of 4 week astaxanthin supplementation (a potent cartenoid antioxidant) on antioxidant capacity and exercise-induced cardiac troponin release in cyclists.

Methods

Thirty-two well-trained male cyclists (age 25±5, weight 73±7 kg, maximum O₂ uptake 60±5 mL·kg⁻¹·min⁻¹, W_max 5.4±0.5 W·kg⁻¹; mean ± SD) were repeatedly subjected to a laboratory based standardized exercise protocol before and after 4 weeks of astaxanthin (20 mg/day), or placebo supplementation in a double-blind randomized manner. Blood samples were obtained at baseline, at 60 min of cycling and immediately post-exercise (≈ 120 min).

Results

The pre-supplementation cycling trial induced a significant rise of median cardiac troponin T concentrations from 3.2 (IQR 3.0–4.2) to 4.7 ng/L (IQR 3.7–6.7), immediately post-exercise (p<0.001). Four weeks of astaxanthin supplementation significantly increased mean basal plasma astaxanthin concentrations from non-detectable values to 175±86 µg·kg⁻¹. However, daily astaxanthin supplementation had no effect on exercise-induced cardiac troponin T release (p = 0.24), as measured by the incremental area under the curve. Furthermore, the elevation in basal plasma astaxanthin concentrations was not reflected in changes in antioxidant capacity markers (trolox equivalent antioxidant capacity, uric acid, and malondialdehyde). Markers of inflammation (high-sensitivity C-reactive protein) and exercise-induced skeletal muscle damage (creatine kinase) were equally unaffected by astaxanthin supplementation.

Conclusion

Despite substantial increases in plasma astaxanthin concentrations, astaxanthin supplementation did not improve antioxidant capacity in well-trained cyclists. Accordingly, exercise-induced cardiac troponin T concentrations were not affected by astaxanthin supplementation.

Trial registration

ClinicalTrials.gov NCT01241877

Galectin-3 increase in endurance athletes

BACKGROUND

Galectin-3 is a new and promising biomarker for heart failure and myocardial fibrosis. Although endurance exercise is a crucial element in cardiovascular disease prevention, the relationship between exercise and plasma levels of galectin-3 is still unknown. To date, the relationship between regular exercise and myocardial fibrosis is not fully understood. This study investigates the relationship between endurance exercise and plasma levels of galectin-3.

METHODS

Twenty-one male, healthy non-elite marathon runners were examined before and within 1 hour after a strenuous run of 30 km after 4-day training abstinence. Examination included blood samples for galectin-3, echocardiography, and cardiac magnetic resonance imaging (CMR). In addition, to distinguish between cardiac or skeletal muscular origin of galectin-3, 27 C57Bl/6 J mice performing voluntary wheel running and 25 sedentary mice were analysed.

RESULTS

Plasma galectin-3 in endurance athletes increased from baseline to post exercise (12.8 ± 3.4 ng/ml to 19.9 ± 3.9 ng/ml, p < 0.001) while the systolic left and right ventricular function remained unchanged. Interestingly, baseline plasma levels of galectin-3 were in normal range but higher than in healthy sedentary controls. However, in CMR there was no correlation between baseline galectin-3 levels and the detection of myocardial fibrosis. In animal studies, the relative level of mRNA for galectin-3 in active mice was significantly higher compared to sedentary mice. This increase was most pronounced in skeletal muscle (98.0% higher, p < 0.001) and not in the myocardium of the left ventricle (19.9% higher, p = 0.043).

CONCLUSIONS

Plasma galectin-3 is substantially elevated in endurance athletes after running but does not correlate with cardiac function, other biomarkers, or myocardial fibrosis. In mice, we demonstrate that galectin-3 increase during endurance exercise originates primarily from skeletal muscle.

Losartan prevents heart fibrosis induced by long-term intensive exercise in an animal model

Rationale

Recently it has been shown that long-term intensive exercise practice is able to induce myocardial fibrosis in an animal model. Angiotensin II is a profibrotic hormone that could be involved in the cardiac remodeling resulting from endurance exercise.

Objective

This study examined the antifibrotic effect of losartan, an angiotensin II type 1 receptor antagonist, in an animal model of heart fibrosis induced by long-term intense exercise.

Methods and Results

Male Wistar rats were randomly distributed into 4 experimental groups: Exercise, Exercise plus losartan, Sedentary and Sedentary plus losartan. Exercise groups were conditioned to run vigorously for 16 weeks. Losartan was orally administered daily before each training session (50 mg/kg/day). Time-matched sedentary rats served as controls. After euthanasia, heart hypertrophy was evaluated by histological studies; ventricular collagen deposition was quantified by histological and biochemical studies; and messenger RNA and protein expression of transforming growth factor-β1, fibronectin-1, matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1, procollagen-I and procollagen-III was evaluated in all 4 cardiac chambers. Daily intensive exercise caused hypertrophy in the left ventricular heart wall and originated collagen deposition in the right ventricle. Additionally long-term intensive exercise induced a significant increase in messenger RNA expression and protein synthesis of the major fibrotic markers in both atria and in the right ventricle. Losartan treatment was able to reduce all increases in messenger RNA expression and protein levels caused by exercise, although it could not completely reverse the heart hypertrophy.

Conclusions

Losartan treatment prevents the heart fibrosis induced by endurance exercise in training animals.

Arrhythmias in the athlete

Regular exercise provides substantial health benefits, mostly by reducing cardiovascular risk factors. However, it may also trigger acute cardiac events and cause sudden cardiac death in individuals with a pre-existing condition. In an otherwise healthy population, intense regular exercise may lead to morphological and electrical cardiac adaptations commonly referred as "athlete's heart." Recent data suggest that this may itself produce structural changes of atrial and ventricular myocardium with enlargement and fibrosis, creating the substrate for development of arrhythmias in apparently healthy athletes. The state of the art in this controversial issue is reviewed.

[ECG diagnostics in competitive athletes. Current implications for preparticipation screening]

In young competitive athletes sudden cardiac death frequently occurs as a tragic first manifestation of clinically inapparent underlying structural or electrical cardiac disorders. An increased risk may be reflected by typical electrocardiogram (ECG) alterations preceding symptoms but a correct interpretation is often challenging due to a high prevalence of training-related ECG alterations in competitive athletes mimicking such disorders. Misinterpretation may thus result in either unnecessary disqualification from competitive sports or continuation despite an increased risk or extensive diagnostic work-ups yielding additional equivocal findings. However, as observed in large athlete cohorts in recent years a variety of ECG alterations, such as isolated increased QRS voltage, early repolarization, sinus bradycardia, first degree AV block or incomplete right bundle branch block, represent common variants of ECGs of athletes reflecting physiological and training-related cardiac adaptations. These alterations do not usually require further diagnostic evaluation. In contrast, alterations such as repolarization abnormalities, complete bundle branch block, prolonged QT intervals or pathological Q waves, are strongly suggestive of underlying disorders and require further evaluation even in asymptomatic athletes. Thus, the ECG plays a pivotal role in the prevention of sudden cardiac death in competitive athletes. The present article summarizes current recommendations for the interpretation of athlete ECGs regarding the differentiation between physiological or pathological cardiac adaptation.

Vigorous-intensity leisure-time physical activity and risk of major chronic disease in men

PURPOSE

Although studies have shown health benefits for moderate-intensity physical activity, there is limited evidence to support beneficial effects for high amounts of vigorous activity among middle-age and older men. The objective of this study was to examine the relationship between vigorous-intensity physical activity, compared with moderate-intensity activity, and risk of major chronic disease in men.

METHODS

We prospectively examined the associations between vigorous- and moderate-intensity physical activity and risk of major chronic disease among 44,551 men age 40-75 yr in 1986. Leisure-time physical activity was assessed biennially by questionnaire. During 22 yr of follow-up, we documented 14,162 incident cases of major chronic disease, including 4769 cardiovascular events, 6449 cancer events, and 2944 deaths from other causes.

RESULTS

The HR of major chronic disease comparing ≥ 21 to 0 MET.h.wk(-1) of exercise was 0.86 (95% confidence interval (CI), 0.81-0.91) for vigorous-intensity activity and 0.85 (95% CI, 0.80-0.90) for moderate activity. For cardiovascular disease (CVD), the corresponding HRs were 0.78 (95% CI, 0.70-0.86) and 0.80 (95% CI, 0.72-0.88), respectively. When examined separately, running, tennis, and brisk walking were inversely associated with CVD risk. Furthermore, more vigorous activity was associated with lower disease risk; the HR comparing >70 to 0 MET.h.wk(-1) of vigorous-intensity exercise was 0.79 (95% CI, 0.68-0.92; P < 0.0001 for trend) for major chronic disease and 0.73 (95% CI, 0.56-0.96; P < 0.0001 for trend) for CVD.

CONCLUSIONS

Vigorous- and moderate-intensity physical activities were associated with lower risk of major chronic disease and CVD. Increasing amounts of vigorous activity remained inversely associated with disease risk, even among men in the highest categories of exercise.

The impact of repeated marathon running on cardiovascular function in the aging population

BACKGROUND

Several studies have correlated elevations in cardiac biomarkers of injury post marathon with transient and reversible right ventricular (RV) systolic dysfunction as assessed by both transthoracic echocardiography (TTE) and cardiovascular magnetic resonance (CMR). Whether or not permanent myocardial injury occurs due to repeated marathon running in the aging population remains controversial.

OBJECTIVES

To assess the extent and severity of cardiac dysfunction after the completion of full marathon running in individuals greater than 50 years of age using cardiac biomarkers, TTE, cardiac computed tomography (CCT), and CMR.

METHODS

A total of 25 healthy volunteers (21 males, 55 ± 4 years old) from the 2010 and 2011 Manitoba Full Marathons (26.2 miles) were included in the study. Cardiac biomarkers and TTE were performed one week prior to the marathon, immediately after completing the race and at one-week follow-up. CMR was performed at baseline and within 24 hours of completion of the marathon, followed by CCT within 3 months of the marathon.

RESULTS

All participants demonstrated an elevated cTnT post marathon. Right atrial and ventricular volumes increased, while RV systolic function decreased significantly immediately post marathon, returning to baseline values one week later. Of the entire study population, only two individuals demonstrated late gadolinium enhancement of the subendocardium in the anterior wall of the left ventricle, with evidence of stenosis of the left anterior descending artery on CCT.

CONCLUSIONS

Marathon running in individuals over the age of 50 is associated with a transient, yet reversible increase in cardiac biomarkers and RV systolic dysfunction. The presence of myocardial fibrosis in older marathon athletes is infrequent, but when present, may be due to underlying occult coronary artery disease.

The right heart in athletes. Evidence for exercise-induced arrhythmogenic right ventricular cardiomyopathy

Although 'athlete's heart' usually constitutes a balanced dilation and hypertrophy of all four chambers, there is increasing evidence that intense endurance activity may particularly tax the right ventricle (RV), both acutely and chronically. We review the evidence that the high wall stress of the RV during intense sports may explain observed B-type natriuretic peptide (BNP) elevations immediately after a race, may lead to cellular disruption and leaking of cardiac enzymes, and may even result in transient RV dilatation and dysfunction. Over time, this could lead to chronic remodelling and a pro-arrhythmic state resembling arrhythmogenic RV cardiomyopathy (ARVC) in some cases. ARVC in high-endurance athletes most often develops in the absence of underlying desmosomal abnormalities, probably only as a result of excessive RV wall stress during exercise. Therefore, we have labelled this syndrome 'exercise-induced ARVC'. Sports cardiologists should be aware that excessive sports activity can lead to cardiac sports injuries in some individuals, just like orthopaedic specialists are familiar with musculoskeletal sports injuries. This does not negate the fact that moderate exercise has positive cardiovascular effects and should be encouraged.

Potential adverse cardiovascular effects from excessive endurance exercise

A routine of regular exercise is highly effective for prevention and treatment of many common chronic diseases and improves cardiovascular (CV) health and longevity. However, long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries. Emerging data suggest that chronic training for and competing in extreme endurance events such as marathons, ultramarathons, ironman distance triathlons, and very long distance bicycle races, can cause transient acute volume overload of the atria and right ventricle, with transient reductions in right ventricular ejection fraction and elevations of cardiac biomarkers, all of which return to normal within 1 week. Over months to years of repetitive injury, this process, in some individuals, may lead to patchy myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, creating a substrate for atrial and ventricular arrhythmias. Additionally, long-term excessive sustained exercise may be associated with coronary artery calcification, diastolic dysfunction, and large-artery wall stiffening. However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity. Notwithstanding, the hypothesis that long-term excessive endurance exercise may induce adverse CV remodeling warrants further investigation to identify at-risk individuals and formulate physical fitness regimens for conferring optimal CV health and longevity.

Exercise-induced cardiac injury: evidence from novel imaging techniques and highly sensitive cardiac troponin assays

Prolonged endurance exercise in humans has been associated with an acute impairment in diastolic and systolic cardiac function and the release of cardiac troponin. In this chapter, we review recent evidence from studies using novel echocardiographic parameters and highly sensitive cardiac troponin assays. We demonstrate that the mechanics of left and right ventricular functions are acutely impaired after completion of prolonged exercise and that this reduction in function is likely multifactorial in etiology. However, we highlight that exercise-induced cardiac troponin release is not a marker of exercise-induced pathology but likely a physiologic response to exercise. Finally, we discuss the potential link between prolonged exercise and the increased incidence of cardiac pathology in veteran athletes.

NEW EAE/ASE recommendations for the use of echocardiography in new transcatheter interventions for valvular heart disease

The new full and detailed recommendations later in this issue are summarized here by Jose L. Zamorano, MD, FESC, chair EAE writing group.

Exercise-induced right ventricular dysfunction and structural remodelling in endurance athletes

AIMS

Endurance training may be associated with arrhythmogenic cardiac remodelling of the right ventricle (RV). We examined whether myocardial dysfunction following intense endurance exercise affects the RV more than the left ventricle (LV) and whether cumulative exposure to endurance competition influences cardiac remodelling (including fibrosis) in well-trained athletes.

METHODS AND RESULTS

Forty athletes were studied at baseline, immediately following an endurance race (3-11 h duration) and 1-week post-race. Evaluation included cardiac troponin (cTnI), B-type natriuretic peptide, and echocardiography [including three-dimensional volumes, ejection fraction (EF), and systolic strain rate]. Delayed gadolinium enhancement (DGE) on cardiac magnetic resonance imaging (CMR) was assessed as a marker of myocardial fibrosis. Relative to baseline, RV volumes increased and all functional measures decreased post-race, whereas LV volumes reduced and function was preserved. B-type natriuretic peptide (13.1 ± 14.0 vs. 25.4 ± 21.4 ng/L, P = 0.003) and cTnI (0.01 ± .03 vs. 0.14 ± .17 μg/L, P < 0.0001) increased post-race and correlated with reductions in RVEF (r = 0.52, P = 0.001 and r = 0.49, P = 0.002, respectively), but not LVEF. Right ventricular ejection fraction decreased with increasing race duration (r = -0.501, P < 0.0001) and VO(2)max (r = -0.359, P = 0.011). Right ventricular function mostly recovered by 1 week. On CMR, DGE localized to the interventricular septum was identified in 5 of 39 athletes who had greater cumulative exercise exposure and lower RVEF (47.1 ± 5.9 vs. 51.1 ± 3.7%, P = 0.042) than those with normal CMR.

CONCLUSION

Intense endurance exercise causes acute dysfunction of the RV, but not the LV. Although short-term recovery appears complete, chronic structural changes and reduced RV function are evident in some of the most practiced athletes, the long-term clinical significance of which warrants further study.

Hypertrophic cardiomyopathy and ultra-endurance running - two incompatible entities?

Regular and prolonged exercise is associated with increased left ventricular wall thickness that can overlap with hypertrophic cardiomyopathy (HCM). Differentiating physiological from pathological hypertrophy has important implications, since HCM is the commonest cause of exercise-related sudden cardiac death in young individuals. Most deaths have been reported in intermittent 'start-stop' sports such as football (soccer) and basketball. The theory is that individuals with HCM are unable to augment stroke volume sufficiently to meet the demands of endurance sports and are accordingly 'selected-out' of participation in such events. We report the case of an ultra-endurance athlete with 25 years of > 50 km competitive running experience, with genetically confirmed HCM; thereby demonstrating that these can be two compatible entities.

Dilatation and Dysfunction of the Right Ventricle Immediately After Ultraendurance Exercise

Background—

Running an ultramarathon has been shown to have a transient negative effect on right ventricular (RV) and left ventricular (LV) function. Additionally, recent findings suggested that ultraendurance athletes may be more at risk of developing a RV cardiomyopathy. The standard echocardiographic assessment of RV function is problematic; however, the introduction of ultrasonic speckle tracking technology has the potential to yield a comprehensive evaluation of RV longitudinal function, providing new insights into this phenomenon. Thus, the primary aim of this exploratory study was to evaluate comprehensively RV structure and function after a 161-km ultramarathon and establish whether changes in the RV are associated with alterations in LV function.

Methods and Results—

Myocardial speckle tracking echocardiograms of the RV and LV were obtained before and immediately after a 161-km ultramarathon in 16 healthy adults. Standard echocardiography was used to determine RV size and function and LV eccentricity index. Speckle tracking was used to determine the temporal evaluation of indices of RV and LV function. RV size was significantly increased postrace (RV outflow, 32 to 35 mm, P =0.002; RV inflow, 42 to 45 mm, P =0.027) with an increase in LV eccentricity index (1.03 to 1.13, P =0.006). RV strain (ε) was significantly reduced postrace (−27% to −24%, P =0.004), but there was no change in the rates of ε. Peak ε in all planes of LV motion were reduced postrace (longitudinal, −18.3 to −16.3%, P =0.012; circumferential, −20.2% to −15.7%, P =0.001; radial, 53.4% to 40.3%, P =0.009). Changes in RV size and function correlated with diastolic strain rates in the LV.

Conclusions—

This exploratory study demonstrates RV dilatation and reduction in function after an ultramarathon. Further research is warranted to elucidate the mechanisms responsible for these findings. It is not clear what clinical impact might result from consecutive bouts of postexercise RV dysfunction.

Mitochondrial DNA mutators

In this article we review our current knowledge of the mechanisms by which point mutations arise in the mitochondrial DNA (mtDNA) of Saccharomyces cerevisiae and discuss to what extent these mechanisms operate in human mtDNA mutagenesis. The 3'-5' exonuclease proofreading activity of Pol gamma ensures accuracy of mtDNA replication in both yeast and humans, while the role of base excision repair in mtDNA error avoidance remains debated. The mitochondrial mismatch repair Msh1 protein, which removes transitions in yeast, is absent in humans, a particularity that might cause accumulation of transitions, while the most frequent substitution in yeast mtDNA is A:T to T:A transversion. Proofreading-deficient mutator human cell lines and knockin mice have been created. They will be useful for studying the mechanisms by which mtDNA mutations accumulate in diseases, ageing, malignancy and drug therapy.