Non-invasive evaluation of cardiac function in professional cyclists

Cardiac Structure and Cardiorespiratory Fitness in Young Male Japanese Rugby Athletes

Limited data are available on athlete's heart for rugby athletes. This study aimed to investigate cardiac structure and its relationship with cardiorespiratory fitness in young Japanese rugby athletes. A prospective cross-sectional study using echocardiography and cardiopulmonary exercise testing (CPET) was conducted on 114 male collegiate rugby players. There was a higher prevalence of increased left ventricular (LV), atrial, and aortic dimensions in the young athletes than that in previously published reports, whereas the wall thickness was within the normal range. Anthropometry and CPET analyses indicated that the forwards and backs presented muscular and endurance phenotypes, respectively. Indexed LV and aortic dimensions were significantly larger in the backs than in the forwards, and the dimensions significantly correlated with oxygen uptake measured by CPET. On the four-tiered classification for LV hypertrophy, abnormal LV geometry was found in 16% of the athletes. Notably, the resting systolic blood pressure was significantly higher in athletes with concentric abnormal geometry than in the other geometry groups, regardless of their field positions. Japanese young athletes may exhibit unique phenotypes of cardiac remodeling in association with their fitness characteristics. The four-tiered LV geometry classification potentially offers information regarding the subclinical cardiovascular risks of young athletes.

Differentiating Physiology from Pathology: The Gray Zones of the Athlete's Heart

Routine vigorous exercise can lead to electrical, structural, and functional adaptations that can enhance exercise performance. There are several factors that determine the type and magnitude of exercise-induced cardiac remodeling (EICR) in trained athletes. In some athletes with pronounced cardiac remodeling, there can be an overlap in morphologic features with mild forms of cardiomyopathy creating gray zone scenarios whereby distinguishing health from disease can be difficult. An integrated clinical approach that factors athlete-specific characteristics (sex, size, sport, ethnicity, and training history) and findings from multimodality imaging are essential to help make this distinction.

Impact of endurance exercise on the heart of cyclists: A systematic review and meta-analysis

OBJECTIVE

To compare heart structure and function in endurance athletes relative to participants of other sports and non-athletic controls in units relative to body size. A secondary objective was to assess the association between endurance cycling and cardiac abnormalities.

PATIENTS AND METHODS

Five electronic databases (CINAHL, Cochrane Library, Medline, Scopus, and SPORTdiscus) were searched from the earliest record to 14 December 2019 to identify studies investigating cardiovascular structure and function in cyclists. Of the 4865 unique articles identified, 70 met inclusion criteria and of these, 22 articles presented 10 cardiovascular parameters in units relative to body size for meta-analysis and five presented data relating to incidence of cardiac abnormalities. Qualitative analysis was performed on remaining data. The overall quality of evidence was assessed using GRADE. Odds ratios were calculated to compare the incidence of cardiac abnormality.

RESULTS

Heart structure was significantly larger in cyclists compared to non-athletic controls for left ventricular: mass; end-diastolic volume, interventricular septal diameter and internal diameter; posterior wall thickness, and end-systolic internal diameter. Compared to high static and high dynamic sports (e.g., kayaking and canoeing), low-to-moderate static and moderate-to-high dynamic sports (e.g., running and swimming) and moderate-to-high static and low-to-moderate dynamic sports (e.g., bodybuilding and wrestling), endurance cyclists end-diastolic left ventricular internal diameter was consistently larger (mean difference 1.2-3.2 mm/m²). Cardiac abnormalities were higher in cyclists compared to controls (odds ratio: 1.5, 95%CI 1.2-1.8), but the types of cardiac abnormalities in cyclists were not different to other athletes.

CONCLUSION

Endurance cycling is associated with a larger heart relative to body size and an increased incidence of cardiac abnormalities relative to controls.

Metabolic Mechanisms of Exercise-Induced Cardiac Remodeling

Exercise has a myriad of physiological benefits that derive in part from its ability to improve cardiometabolic health. The periodic metabolic stress imposed by regular exercise appears fundamental in driving cardiovascular tissue adaptation. However, different types, intensities, or durations of exercise elicit different levels of metabolic stress and may promote distinct types of tissue remodeling. In this review, we discuss how exercise affects cardiac structure and function and how exercise-induced changes in metabolism regulate cardiac adaptation. Current evidence suggests that exercise typically elicits an adaptive, beneficial form of cardiac remodeling that involves cardiomyocyte growth and proliferation; however, chronic levels of extreme exercise may increase the risk for pathological cardiac remodeling or sudden cardiac death. An emerging theme underpinning acute as well as chronic cardiac adaptations to exercise is metabolic periodicity, which appears important for regulating mitochondrial quality and function, for stimulating metabolism-mediated exercise gene programs and hypertrophic kinase activity, and for coordinating biosynthetic pathway activity. In addition, circulating metabolites liberated during exercise trigger physiological cardiac growth. Further understanding of how exercise-mediated changes in metabolism orchestrate cell signaling and gene expression could facilitate therapeutic strategies to maximize the benefits of exercise and improve cardiac health.

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.

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.

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.

Does echocardiography accurately reflect CMR-determined changes in left ventricular parameters following exercise training? A prospective longitudinal study

Cardiac adaptation in response to exercise has historically been described using echocardiography. Cardiac magnetic resonance (CMR), however, has evolved as a preferred imaging methodology for cardiac morphological assessment. While direct imaging modality comparisons in athletes suggest that large absolute differences in cardiac dimensions exist, it is currently unknown whether changes in cardiac morphology in response to exercise training are comparable when using echocardiography and CMR. Twenty-two young men were randomly assigned to undertake a supervised and intensive endurance or resistance exercise-training program for 24 wk. Echocardiography and CMR assessment of left ventricular (LV) mass, LV end-diastolic volume, internal cavity dimensions, and wall thicknesses were completed before and after training. At baseline, pooled data for all cardiac parameters were significantly different between imaging methods, while LV mass (r = 0.756, P < 0.001) and volumes (LV end-diastolic volume, r = 0.792, P < 0.001) were highly correlated across modalities. Changes in cardiac morphology data with exercise training were not significantly related when echocardiographic and CMR measures were compared. For example, posterior wall thickness increased by 8.3% (P < 0.05) when assessed using echocardiography, but decreased by 2% when using CMR. In summary, echocardiography and CMR imaging modalities produce findings that differ with respect to changes in cardiac size and volume following exercise training.

Exercise-induced cardiac remodeling

Early investigations in the late 1890s and early 1900s documented cardiac enlargement in athletes with above-normal exercise capacity and no evidence of cardiovascular disease. Such findings have been reported for more than a century and continue to intrigue scientists and clinicians. It is well recognized that repetitive participation in vigorous physical exercise results in significant changes in myocardial structure and function. This process, termed exercise-induced cardiac remodeling (EICR), is characterized by structural cardiac changes including left ventricular hypertrophy with sport-specific geometry (eccentric vs concentric). Associated alterations in both systolic and diastolic functions are emerging as recognized components of EICR. The increasing popularity of recreational exercise and competitive athletics has led to a growing number of individuals exhibiting these findings in routine clinical practice. This review will provide an overview of EICR in athletes.

The association of left ventricular mass with blood pressure, cigarette smoking and alcohol consumption; data from the LARGE Heart study

BACKGROUND

Left ventricular mass is a risk factor for cardiovascular morbidity and mortality. Although factors associated with elevated left ventricular mass have been sought and studied extensively in elderly and in diseased subjects, few studies have examined the young and healthy. The aim of this study was to examine the possible influence of lifestyle on left ventricular mass in a large group of young men.

METHODS

Left ventricular mass was assessed using cardiovascular magnetic resonance in 541 healthy Caucasian male army recruits. Anthropometric, lifestyle and blood pressure data were collected.

RESULTS

Mean unadjusted left ventricular mass and left ventricular mass indexed to body surface area were 163.8+/-24.9 g and 86.6+/-10.2 g m(-2) respectively. In univariate analysis, age, height, weight, alcohol consumption, systolic blood pressure, diastolic blood pressure and indices of physical activity were positively associated with unadjusted left ventricular mass (all P<0.02). By contrast, smoking was associated with lower mean left ventricular mass; never smoked 167.5+/-25.8 g vs ex-smokers 159.1+/-25.2 g vs current smokers 161.0+/-23.1 g (P=0.007). Multivariate analysis revealed weight, systolic blood pressure, smoking status and indices of physical activity to be independent predictors of left ventricular mass.

CONCLUSIONS

Our data confirm an association of age, body weight, height, physical activity, diastolic and systolic blood pressure with left ventricular mass. In addition, unexpectedly, we have found smoking is associated with lower left ventricular mass in a large sample of young healthy men. Although the latter association may result from confounding effects, such an interesting observation deserves further investigation.

Peak aerobic performance and left ventricular morphological characteristics in university students

OBJECTIVE

To determine whether a relationship exists between left ventricular morphology and aerobic capacity in large numbers of male university students with a physically inactive and active life style.

DESIGN

A prospective study.

SETTING

Sports medicine research center.

PARTICIPANTS

Eleven sedentary normal-weight university students, 17 sedentary overweight university students, and 215 university athletes.

MAIN OUTCOME MEASURES

After the echocardiographic examination, an incremental treadmill exercise test until exhaustion was performed to measure peak oxygen uptake (VO2).

RESULTS

In sedentary students, absolute peak VO2 in the overweight students was slightly higher than that in normal-weight students (3,024 vs. 2.912 ml/min). Relative peak VO2 (ml/min/kg) was highly negatively correlated with body mass index (kg/m2) in a total of 28 sedentary students. The correlation between absolute peak VO2 and left ventricular dimension was weak in the sedentary overweight students; however, a correlation coefficient of 0.55 was obtained in athletic students. A stepwise multiple regression showed significant determinants of absolute peak VO2 in athletic students for body surface area (45%), left ventricular dimension (7%), and certain sports (6%).

CONCLUSIONS

A physically active life style plays a role in increasing both aerobic capacity and left ventricular enlargement. Body size appeared to be a potent stimulus to left ventricular enlargement.

Cardiac responses to exercise in competitive child cyclists

PURPOSE

Cardiovascular responses to exercise in highly trained child endurance athletes have not been well-defined. This study compared hemodynamic responses with progressive cycle exercise in seven competitive child cyclists (mean age 11.9 yr) compared with 39 age-matched untrained boys.

METHODS

Doppler echocardiography and gas exchange variables were utilized to assess cardiovascular changes during submaximal and maximal exercise.

RESULTS

Mean VO2max was 60.0 (+/-6.0) and 47.0 (+/-5.8) mL x kg(-1) x min(-1) in the cyclists and nonathletes, respectively. At rest and maximal exercise, the cyclists demonstrated greater stroke index than the untrained subjects (resting mean 59 (+/-6) vs 44 (+/-9) mL x m(-2); maximal mean 76 (+/-6) vs 60 (+/-11) mL x m(-2)), but the ratio of maximal:rest stroke index was similar in both groups (1.31 for cyclists, 1.41 for nonathletes). Both groups showed a plateau in stroke volume beyond low-intensity work levels. No significant difference was observed in maximal arteriovenous oxygen difference.

CONCLUSIONS

These findings indicate that 1) maximal stroke volume is the critical determinant of the high VO2max in child cyclists and 2) factors that influence resting stroke volume are important in defining VO2max differences between child endurance athletes and untrained boys.

The athlete's heart. A meta-analysis of cardiac structure and function

BACKGROUND

It has been postulated that depending on the type of exercise performed, 2 different morphological forms of athlete's heart may be distinguished: a strength-trained heart and an endurance-trained heart. Individual studies have not tested this hypothesis satisfactorily.

METHODS AND RESULTS

The hypothesis of divergent cardiac adaptations in endurance-trained and strength-trained athletes was tested by applying meta-analytical techniques with the assumption of a random study effects model incorporating all published echocardiographic data on structure and function of male athletes engaged in purely dynamic (running) or static (weight lifting, power lifting, bodybuilding, throwing, wrestling) sports and combined dynamic and static sports (cycling and rowing). The analysis encompassed 59 studies and 1451 athletes. The overall mean relative left ventricular wall thickness of control subjects (0.36 mm) was significantly smaller than that of endurance-trained athletes (0.39 mm, P=0.001), combined endurance- and strength-trained athletes (0.40 mm, P=0.001), or strength-trained athletes (0.44 mm, P<0.001). There was a significant difference between the 3 groups of athletes and control subjects with respect to left ventricular internal diameter (P<0. 001), posterior wall thickness (P<0.001), and interventricular septum thickness (P<0.001). In addition, endurance-trained athletes and strength-trained athletes differed significantly with respect to mean relative wall thickness (0.39 versus 0.44, P=0.006) and interventricular septum thickness (10.5 versus 11.8 mm, P=0.005) and showed a trend toward a difference with respect to posterior wall thickness (10.3 versus 11.0 mm, P=0.078) and left ventricular internal diameter (53.7 versus 52.1 mm, P=0.055). With respect to cardiac function, there were no significant differences between athletes and control subjects in left ventricular ejection fraction, fractional shortening, and E/A ratio.

CONCLUSIONS

Results of this meta-analysis regarding athlete's heart confirm the hypothesis of divergent cardiac adaptations in dynamic and static sports. Overall, athlete's heart demonstrated normal systolic and diastolic cardiac functions.

Vascular and cardiac remodeling in world class professional cyclists

BACKGROUND

Numerous studies have demonstrated that left ventricular (LV) hypertrophy is often associated with conditioning.

METHODS AND RESULTS

The aim of the study was to evaluate cardiac and carotid artery changes induced by professional cycling. We collected M-mode left ventricle and B-mode right common carotid artery data from 149 male professional cyclists before the 1995 "Tour de France" race and 52 male control subjects. LV mass indexed to body surface area in cyclists was double that in control subjects, with no overlap of 95% confidence intervals (cyclists 100.9 to 187 g/m2 and control subjects 51.8 to 96.3 g/m2). Both mean arterial diameter and mean arterial diastolic intima-media thickness (IMT) were 13% higher in cyclists than in control subjects, with overlap of 95% confidence intervals (for arterial IMT 0.45 to 0.65 mm in cyclists and 0.38 to 0.60 mm in control subjects).

CONCLUSIONS

Our results suggest that intense cycling has an effect on the cardiovascular system, more pronounced on the left ventricle and less pronounced on large arteries. Nevertheless, athletic training should be considered as a potential determinant of carotid modification.

Functional and metabolic evaluation of the athlete's heart by magnetic resonance imaging and dobutamine stress magnetic resonance spectroscopy

BACKGROUND

The question of whether training-induced left ventricular hypertrophy in athletes is a physiological rather than a pathophysiological phenomenon remains unresolved. The purpose of the present study was to detect any abnormalities in cardiac function in hypertrophic hearts of elite cyclists and to examine the response of myocardial high-energy phosphate metabolism to high workloads induced by atropine-dobutamine stress.

METHODS AND RESULTS

We studied 21 elite cyclists and 12 healthy control subjects. Left ventricular mass, volume, and function were determined by cine MRI. Myocardial high-energy phosphates were examined by 31P magnetic resonance spectroscopy. There were no significant differences between cyclists and control subjects for left ventricular ejection fraction (59+/-5% versus 61+/-4%), left ventricular cardiac index (3.4+/-0.4 versus 3.4+/-0.4 L x min(-1) x m[-2]), peak early filling rate (562+/-93 versus 535+/-81 mL/s), peak atrial filling rate (315+/-93 versus 333+/-65 mL/s), ratio of early and atrial filling volumes (3.0+/-1.0 versus 2.6+/-0.6), mean acceleration gradient of early filling (5.2+/-1.4 versus 5.8+/-1.9 L/s2), mean deceleration gradient of early filling(-3.1 +/- 0.9 versus -3.2 +/- 0.7 L/s2), mean acceleration gradient of atrial filling (3.6+/-1.8 versus 4.5+/-1.7 L/s2), and atrial filling fraction (0.23+/-0.06 versus 0.26+/-0.04, respectively). Cyclists and control subjects showed similar decreases in the ratio of myocardial phosphocreatine to ATP measured with 31P magnetic resonance spectroscopy during atropine-dobutamine stress (1.41+/-0.20 versus 1.41+/-0.18 at rest to 1.21+/-0.20 versus 1.16+/-0.13 during stress, both P=NS).

CONCLUSIONS

Left ventricular hypertrophy in cyclists is not associated with significant abnormalities of cardiac function or metabolism as assessed by MRI and spectroscopy. These observations suggest that training-induced left ventricular hypertrophy in cyclists is predominantly a physiological phenomenon.

Exercise and heart disease: cardiac findings in fatal cycle accidents

BACKGROUND

Regular cyclists have been found to have a lower incidence of coronary events (CHD) than the general public. Non-invasive studies have found that competitive cyclists develop a cardiac hypertrophy that is physiological and reversible.

METHODS

To obtain pathological support for these observations, the postmortem findings of 32 cyclists killed in accidents have been compared with those in a control group of 32 other road traffic accidents, which were matched with the cyclists by sex, age, and year of death.

FINDINGS

Large myocardial scars and complete blockage of a coronary artery were only found in the controls; serious stenoses of coronary arteries (> 50%) were found in eight controls but in only one of the cyclists. Of the cyclists, 25 had normal coronary arteries as compared with 14 of the controls. The mean age of the cyclists with evidence of CHD was greater than that of similarly affected controls. The heart weights of the two groups were almost the same but heart weight varied with the degree of CHD. The heart weight of the healthy cyclists (389 g) was greater than that of the healthy controls (371 g) but this was not statistically significant.

INTERPRETATION

The results are in keeping with the concept that regular exercise provides some protection from the development of CHD and that cycling may be a valuable form of exercise in this respect. This may be of importance as the number of physically active occupations declines.

Impact of different sports and training on cardiac structure and function

There is overwhelming evidence, particularly from echocardiography, that the heart of competitive athletes may differ from that of nonathletes, matched for age, gender, and body size. A larger left ventricular mass has been shown in athletes performing predominantly dynamic aerobic and anaerobic sports, in athletes engaged in static training, and in players of ball sports. Enlargement of the left ventricular internal diameter was most pronounced and reached about 10% in athletes performing predominantly dynamic sports; mainly strength training athletes had a lesser increase of the internal dimension, which was limited to 2.5%. Also the left ventricular wall appeared to be thickened in all types of athletes compared with controls. In sports with high dynamic and low static demands, wall thickness was proportionate or slightly disproportionate to the size of the internal diameter so that relative wall thickness was not different from controls or slightly increased (predominantly eccentric hypertrophy). In strength athletes, the disproportionate increase of wall thickness averaged about 12% (predominantly concentric hypertrophy). In sports with high dynamic and high static demands and requiring prolonged training, such as cycling, the increases of absolute and relative wall thickness reached 29% and 19% and were more pronounced than in runners (mixed hypertrophy). A plausible interpretation of these results is that the development of so-called eccentric or concentric left ventricular hypertrophy according to the type of sports cannot be regarded as an absolute or dichotomous concept because training regimens and sports activities are not exclusively dynamic or static and because the load on the heart is not purely of the volume or the pressure type. Most studies agree that left ventricular systolic and diastolic function is normal in the athlete at rest, whereas diastolic function seems to be enhanced in the exercising endurance athlete. The consistency of the results of studies on athletes in the competitive and the resting season, of training of sedentary subjects, and of spinal cord-injured patients suggests that variations in physical activity can alter left ventricular structure; genetic factors do not seem to be involved in the size of the left ventricular internal diameter but have to be taken into account to interpret wall thickness.

Seasonal variation in fitness parameters in competitive athletes

In many sports, training for successful competition has become virtually a year-round endeavour. To assist in better preparation, a competitor's year may be divided into phases such as off-season and in-season, indicating reduced or increased competition commitments, respectively. A number of studies have described the effects of seasons or periods of competition, training, detraining and reduced training on aspects of physical fitness. Depending on performance level, the type of sport and the fitness parameter in question, the swings in fitness variables reported may be as high as 18% from one season to another. In elite competitors, anaerobic parameters, heart frequencies, subcutaneous fat, flexibility and haemoglobin levels remain relatively unchanged throughout the year. Aerobic metabolism and muscular strength may demonstrate noticeable (mostly unfavourable) changes, and plasma hormonal levels normally follow changes in training intensities. Aspects related to long term fatigue and genetics, and to appropriate training are just a few explanations for these observations. It is still not known whether greater fitness gains attainable with longer off-season training programmes can be successfully maintained over the duration of the competition season. However, the consensus would seem to be that specialised training (based on technique and competition tactics only) is inadequate for fitness maintenance and/or improvements. This is perhaps supported by the general trends found in the literature regarding muscular strength: while supervised off-season conditioning programmes may result in significant improvements for both recreational and competitive athletes, no such changes are normally observed after competition seasons. These findings may reflect, amongst other factors, a lack of optimal training intensity to bring about strength increases during in-season periods. In novices and in athletes at low competitive levels, training seasons may lead to considerable functional improvements of the cardiorespiratory system, coupled with occasional increases in muscular strength and decreases in body fat. Relatively low fitness levels at the beginning of training have been put forward as an explanation for these improvements. Seasons of training and competition result in no significant changes in flexibility measurements. Similar changes to those found in novices and in athletes at low competitive levels may also be seen in children and adolescents engaged in sport, although their fitness improvements are consistent with normal patterns of growth and development. No differences have been identified between male and female athletes participating at different competition levels.

Comparison of athletes with life-threatening ventricular arrhythmias with two groups of healthy athletes and a group of normal control subjects

Sudden cardiac death in well-trained athletes is most often superimposed on the presence of structural heart disease. However, some athletes die suddenly in the absence of overt heart disease. To improve identification of athletes at high risk for ventricular tachycardia (VT), ventricular repolarization, the signal-averaged electrocardiogram (ECG), and the echocardiogram from 13 male athletes with symptomatic VT and without evidence of manifest cardiac disease were compared with data obtained in 3 matched control groups (15 apparently healthy professional road cyclists, 10 professional basketball players, and 15 normal control subjects without any sports activity). All patients had apparently normal QRS duration on the routine ECG, and none were taking antiarrhythmic drugs. Echocardiography and signal-averaged electrocardiography were useful in distinguishing the group of athletes with tachyarrhythmias from the group of normal nonsporting controls, but not from both groups of normal athletes. The QT interval (V4) and the QT interval corrected with the cubic root were shorter for the nonsporting controls. Three parameters for QT dispersion showed significant differences (p < 0.003) between athletes with disease and all other groups. It is concluded that although significant differences were detected between normal subjects and the 3 groups of athletes by routine ECG, the signal-averaged ECG, and echocardiography, only an increased QT dispersion from the 12-lead ECG was helpful in distinguishing athletes with VT from other athletes.

Morphology of the "athlete's heart" assessed by echocardiography in 947 elite athletes representing 27 sports

In the present study, we used echocardiography to investigate the morphologic adaptations of the heart to athletic training in 947 elite athletes representing 27 sports who achieved national or international levels of competition. Cardiac morphology was compared for these sports, using multivariate statistical models. Left ventricular (LV) diastolic cavity dimension above normal (> 54 mm, ranging up to 66 mm) was identified in 362 (38%) of the 947 athletes. LV wall thickness above normal (> 12 mm, ranging up to 16 mm) was identified in only 16 (1.7%) of the athletes. Athletes training in the sports examined showed considerable differences with regard to cardiac dimensions. Endurance cyclists, rowers, and swimmers had the largest LV diastolic cavity dimensions and wall thickness. Athletes training in sports such as track sprinting, field weight events, and diving were at the lower end of the spectrum of cardiac adaptations to athletic training. Athletes training in sports associated with larger LV diastolic cavity dimensions also had higher values for wall thickness. Athletes training in isometric sports, such as weightlifting and wrestling, had high values for wall thickness relative to cavity dimension, but their absolute wall thickness remained within normal limits. Analysis of gender-related differences in cardiac dimensions showed that female athletes had smaller LV diastolic cavity dimension (average 2 mm) and smaller wall thickness (average 0.9 mm) than males of the same age and body size who were training in the same sport.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic findings in 104 professional cyclists with follow-up study

To assess the effect of long-term athletic training on the heart, 104 professional cyclists and 40 sedentary controls (69 younger cyclists and 26 controls aged 20 to 39 and 35 older cyclists and 14 controls aged 40 to 60) were examined by using M-mode and pulsed Doppler echocardiography. Cyclists had larger and more hypertrophied left ventricle than did controls (p < 0.001) and had normal percentages of fractional shortening (%FS). The ratio of left ventricular late-to-early diastolic peak filling velocity (A/R) of younger cyclists was normal, but the A/R of older cyclists was larger than that of controls (p < 0.001). Of the 104 cyclists, 95 continued cycling and were reexamined 2 years later; 9 of 40 older cyclists retired and were reexamined 20 +/- 8 months after retirement. During the follow-up period for the active cyclists, left ventricular dilatation, hypertrophy, and %FS of both younger and older cyclists and the A/R of younger cyclists did not change. However, the A/R of older cyclists increased (p < 0.01). For the nine retired cyclists, left ventricular dimension decreased (p < 0.001), left ventricular wall thickness and %FS did not change, and A/R increased (p < 0.05) after retirement. We concluded that (1) cyclists had large and hypertrophied left ventricles with normal systolic function, and (2) some cyclists with long-term athletic training may have partly irreversible left ventricular hypertrophy with impaired left ventricular diastolic filling.

How to Recognize 'Athlete's Heart'

In brief Chronic endurance exercise inbrief duces various cardiac adapta- JHHHM tions, including an enlarged left ventricular cavity and an appropriate increase in wall thickness (eccentric hypertrophy), greater ability to increase stroke volume during exercise, and bradycardia at rest. Strength athletes have thicker left ventricular walls with no increase in cavity size (concentric hypertrophy). In the past, chest x-rays and ECG have suggested some of these changes, however, echocardiograms have clearly established the syndrome of the athlete's heart. In addition, these adaptations seldom exceed the range of normal variation seen in the general population. Understanding these alterations helps distinguish healthy adaptations to exercise from signs of disease.

The upper limit of physiologic cardiac hypertrophy in highly trained elite athletes

BACKGROUND

In some highly trained athletes, the thickness of the left ventricular wall may increase as a consequence of exercise training and resemble that found in cardiac diseases associated with left ventricular hypertrophy, such as hypertrophic cardiomyopathy. In these athletes, the differential diagnosis between physiologic and pathologic hypertrophy may be difficult.

METHODS

To address this issue, we measured left ventricular dimensions with echocardiography in 947 elite, highly trained athletes who participated in a wide variety of sports.

RESULTS

The thickest left ventricular wall among the athletes measured 16 mm. Wall thicknesses within a range compatible with the diagnosis of hypertrophic cardiomyopathy (greater than or equal to 13 mm) were identified in only 16 of the 947 athletes (1.7 percent); 15 were rowers or canoeists, and 1 was a cyclist. Therefore, the wall was greater than or equal to 13 mm thick in 7 percent of 219 rowers, canoeists, and cyclists but in none of 728 participants in 22 other sports. All athletes with walls greater than or equal to 13 mm thick also had enlarged left ventricular end-diastolic cavities (dimensions, 55 to 63 mm).

CONCLUSIONS

On the basis of these data, a left-ventricular-wall thickness of greater than or equal to 13 mm is very uncommon in highly trained athletes, virtually confined to athletes training in rowing sports, and associated with an enlarged left ventricular cavity. In addition, the upper limit to which the thickness of the left ventricular wall may be increased by athletic training appears to be 16 mm. Therefore, athletes with a wall thickness of more than 16 mm and a nondilated left ventricular cavity are likely to have primary forms of pathologic hypertrophy, such as hypertrophic cardiomyopathy.

Preseason cardiovascular examination: a review

The responsibility of the physician performing a preseason sports physical examination includes identifying cardiac disease and giving appropriate guidance about participation in competitive sports. This article reviews the leading causes of sudden cardiac death in young athletes, discusses other common cardiac conditions, assesses recommendations for competitive sports, and discusses the preseason examination as a mechanism for detecting a cardiac problem that should exclude an athlete from competition.

ECG variants and cardiac arrhythmias in athletes: clinical relevance and prognostic importance

These findings permit the following conclusions on cardiac changes induced by high-performance sports and high levels of training. Sinus bradycardia and AV block can frequently be observed in athletes, but they do not require attention as long as they are asymptomatic or do not produce pauses exceeding 4 seconds. Persistent rather than transient second-degree AV block or Mobitz second- or third-degree AV block is an extremely unusual finding even in athletes and should be considered a sign of organic lesions until proved otherwise. Supraventricular and AV node ectopic beats are not more frequent in athletes than in the general population except for atrial fibrillation. WPW syndrome is of particular importance, since rapid conduction to the ventricle via the accessory AV pathway is possible, especially if there is a tendency toward atrial fibrillation. Likewise caution is required in athletes with hypertrophic cardiomyopathy. Here hemodynamic deterioration must be anticipated with the occurrence of supraventricular tachycardia. Simple ventricular arrhythmias occur among athletes with the same frequency as in the general population, but they usually disappear with exercise. The occurrence of complex ventricular forms of arrhythmia should always prompt cardiologic examination in search of underlying cardiac disease, particularly hypertrophic or dilated cardiomyopathy. The presence of ventricular arrhythmias without evidence of underlying heart disease does not indicate a special or increased risk of sudden cardiac death. A higher incidence of right and/or left ventricular hypertrophy, exercise-reversible ST elevation, and exercise-reversible changes in T waves (T negativity, sharp and/or excessive T waves) can be considered physiologic changes in the ECGs of athletes. These changes correlate closely with the type of sports activity and degree of training and are reversible when the activity is stopped. Horizontal ST segment depression are by contrast very rare in athletes and should always be clarified by cardiologic examination. Exercise-induced sudden cardiac death in athletes is unusual without preexisting heart disease. The cause of sudden cardiac death among athletes less than 40 years of age can be predominantely ascribed to congenital heart diseases (such as hypertrophic cardiomyopathy or coronary anomalies). In athletes more than 40 years of age and with increasing age, coronary heart disease is the most frequent autopsy finding. A corresponding risk stratification should take these partial dangers into account.

Left ventricular dynamics during exercise in elite marathon runners

To assess left ventricular structure and function at rest and during exercise in endurance athletes, 10 elite marathon runners, aged 28 to 37 years, and 10 matched nonathletes were studied by echocardiography and supine bicycle ergometry. Each athlete's best marathon time was less than 2 h 16 min. Echocardiography was performed at rest, at a 60 W work load and at an individually adjusted work load, at which heart rate was 110 beats/min (physical working capacity 110 [PWC110]). Oxygen uptake at PWC110 averaged (+/- SD) 1.14 +/- 0.2 liters/min in the nonathletes and 2.0 +/- 0.2 liters/min in the runners (p less than 0.001). The left ventricular internal diameter at end-diastole was similar at the three activity levels in the control subjects but increased significantly from rest to exercise in the runners (p less than 0.001). Left ventricular systolic meridional wall stress remained unchanged during exercise in the nonathletes but was significantly higher at PWC110 in the athletes (p less than 0.05). Both the systolic peak velocity of posterior wall endocardial displacement and fractional shortening of the left ventricular internal diameter increased with exercise; at PWC110 the endocardial peak velocity was higher in the runners than in the control subjects (p less than 0.01). The endocardial peak velocity during relaxation was comparable in athletes and control subjects at rest, increased similarly at a 60 W work load, but was higher in the runners at PWC110 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular mass as determined by magnetic resonance imaging in male endurance athletes

Although many studies of the effect of dynamic exercise training on left ventricular (LV) mass have been reported, controversy continues to exist. Previous work has been criticized because of the techniques used for measuring LV mass, the variable level of training of the subjects recruited and the methods used to normalize the data. In an attempt to resolve this controversy, LV mass was determined using the very accurate and reproducible technique of magnetic resonance imaging (MRI). Highly trained competitive athletes including cross-country skiers, endurance cyclists and long distance runners (VO2max = 77 +/- 1, 72 +/- 2 and 75 +/- 2 ml (kg X min)-1, respectively) were examined. The data were normalized for body weight, body surface area and lean body mass. LV mass was significantly greater in skiers (239 +/- 9 g), runners (244 +/- 10 g) and cyclists (258 +/- 11 g) when compared with nonathletic control subjects (189 +/- 6 g) (p less than 0.001), which represents percent differences of 26, 29 and 37%, respectively. LV mass remained greater in the athletes, regardless of the method used to normalize the data. In addition, there was a good correlation between LV mass and VO2max (r = 0.80, p less than 0.001). It was concluded that LV mass is significantly greater in highly trained competitive endurance athletes and that normalizing LV mass with respect to body weight, body surface area or lean body mass does not alter this relation.

Assessment of stiffness of the hypertrophied left ventricle of bicyclists using left ventricular inflow Doppler velocimetry

Sixteen male bicyclists and 16 control subjects were studied to assess whether the left ventricular hypertrophy of athletes is associated with changes in diastolic left ventricular function. The cyclists had a larger left ventricular internal diameter on echocardiography (55.2 versus 47.9 mm; p less than 0.001) and a disproportionate increase in wall thickness relative to the internal diameter (0.48 versus 0.41; p less than 0.01), indicating a mixed eccentric-concentric type of hypertrophy. Left ventricular inflow Doppler velocimetry showed similar results in athletes and control subjects for peak flow velocities in the atrial contraction phase (30 versus 32 cm/s; p = NS) and in the early diastolic rapid filling phase (71 versus 67 cm/s; p = NS). The similar ratio of both velocities, that is, 0.43 in the cyclists and 0.49 in the control subjects, suggests that left ventricular distensibility is unaltered in cyclists. It is concluded that the left ventricular hypertrophy observed in cyclists is not associated with changes in ventricular stiffness, as estimated from left ventricular inflow Doppler velocimetry.

Physiologic hypertrophy: effects on left ventricular systolic mechanics in athletes

Physiologic hypertrophy resulting from intense athletic participation has been reported to result in normal, reduced and augmented overall left ventricular performance. Rather than representing true differences in left ventricular contractility, these data may reflect the variable degree of ventricular dilation and increased wall thickness that occur with different types of exercise. As such, the resultant altered loading conditions may diminish the ability of the usual indexes of left ventricular function to accurately assess the left ventricular contractile state. Therefore, three groups of elite athletes with distinct patterns of myocardial hypertrophy were investigated utilizing recently developed load-independent contractility indexes. Age-matched control subjects (n = 33) were compared with 11 swimmers, 11 long-distance runners and 11 power lifters. Rest echocardiogram, phonocardiogram and calibrated carotid pulse tracing were used to calculate left ventricular dimensions, wall thickness, mass, fractional shortening, velocity of shortening and mean, peak and end-systolic wall stresses and the stress-time and minute stress-time integrals. Compared with control subjects, all athletes had increased left ventricular mass, even when values were normalized for body surface area. Runners had a dilated left ventricular and normal wall thickness, swimmers had a mildly dilated ventricle with increased wall thickness and power lifters had normal cavity size with markedly increased wall thickness. Peak systolic wall stress was normal in runners and swimmers and reduced in power lifters, whereas end-systolic stress was low in swimmers and power lifters and normal in runners. The minute stress-time integral, a measure of myocardial oxygen consumption, was normal in runners and swimmers but was significantly reduced in lifters.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural features of the athlete heart as defined by echocardiography

The morphologic concepts of the "athlete heart" have been enhanced and clarified over the last 10 years by virtue of M-mode echocardiographic studies performed on more than 1,000 competitive athletes. Long-term athletic training produces relatively mild but predictable alterations in cardiac structure that result in an increase in calculated left ventricular mass. This increase in mass observed in highly trained athletes is due to a mild increase in either transverse end-diastolic dimension of the left ventricle or left ventricular wall thickness, or both. Cardiac dimensions in athletes compared with matched control subjects show increases of about 10% for left ventricular end-diastolic dimension, about 15 to 20% for wall thickness and about 45% for calculated left ventricular mass. Furthermore, there is evidence that the modest degree of "physiologic" left ventricular hypertrophy (both the cavity dilation and wall thickening) observed in athletes is dynamic in nature, that is, it may develop rapidly within weeks or months after the initiation of vigorous conditioning and may be reversed in a similar time period after the cessation of training. Several echocardiographic studies also suggest that the precise alterations in cardiac structure associated with training may differ depending on the type of athletic activity undertaken (that is, whether training is primarily dynamic [isotonic] or static [isometric]). Although the ventricular septal to free wall thickness ratio (on M-mode echocardiogram) is almost always within normal limits (less than 1.3), occasionally an athlete will show mild asymmetric thickening of the anterior basal septum (usually 13 to 15 mm). This circumstance may mimic certain pathologic conditions characterized by primary left ventricular hypertrophy such as nonobstructive hypertrophic cardiomyopathy. The long-term significance of increased left ventricular mass in trained athletes has not been conclusively defined. However, there is no evidence at this time suggesting that this form of hypertrophy is itself deleterious to the athlete or predisposes to (or prevents) the natural occurrence of cardiovascular disease later in life.

Athletic dysrhythmias. A case report and review of the phenomenon of the 'athlete's heart'

A 36-year-old athlete was anaesthetised for a minor surgical procedure. His heart rate fell to 30 beats/minute during the operation, the electrocardiogram showed A-V junctional rhythm. Sinus rhythm of 58 beats/minute was restored by atropine 1.2 mg. His resting 12-lead electrocardiogram showed sinus bradycardia and features consistent with a diagnosis of 'athlete's heart'. A review is presented of the physiological and electrocardiographical features of this phenomenon. The current popularity of running as a leisure pursuit makes it important that anaesthetists recognise the peculiarities of the trained athletic heart.

Cardiac structure and function in cyclists and runners. Comparative echocardiographic study

Twelve cyclists and 12 long distance runners matched for age, height, and weight with two control groups of 12 non-athletes were studied echocardiographically to evaluate cardiac structure and function. Runners weighed 8 kg less than cyclists, but age and height were similar. Peak oxygen uptake per kg body weight was higher in athletes than in the control subjects but was similar in the cyclists and in the runners. The athletes' hearts had a larger end diastolic left ventricular internal diameter, mean wall thickness, and cross sectional area of the left ventricular wall than those of the respective control subjects. Nevertheless, whereas the left ventricular internal diameter was not different between the cyclists and runners, mean wall thickness and cross sectional area of the left ventricular wall were greater in the cyclists even after adjustment for weight. The ratio of wall thickness to left ventricular internal radius was significantly larger in cyclists than in their control group, but the ratio was similar in runners and their control group. The echocardiographic indices of left ventricular function were similar in the athletes and the control groups. Systolic left ventricular meridional wall stress was lower in the cyclists than in the runners. The data suggest that runners develop an increase in left ventricular wall thickness which is proportionate to the internal diameter but that in cyclists the increase is disproportionate because of the isometric work of the upper part of the body during cycling.

Physiological left ventricular hypertrophy

Echocardiograms were recorded in 154 active athletes (from various sports) and 21 ex-athletes and compared with those in 40 normal control subjects (non-athletes). Diastolic cavity dimension and posterior wall and septal thickness were measured and left ventricular mass and the ratio of posterior wall thickness to cavity radius and of septum to posterior wall thickness calculated. As a group athletes had a significantly increased diastolic cavity dimension, posterior wall and septal thickness, and left ventricular mass. The ratio of posterior wall thickness to cavity radius was distributed as a single continuous variable with a significantly increased mean, and there was no separate subgroup of shot putters or weight lifters with inappropriate hypertrophy. The mean ratio of septum to posterior wall thickness was normal, but there was a wide range of values up to 2.1:1. Ex-athletes had entirely normal left ventricular dimensions and wall thickness. When athletes are categorised by their standard of competition national standard competitors had a significantly increased posterior wall and septal thickness and left ventricular mass compared with university and non-competitive sportsmen. In conclusion, strenuous activity results in left ventricular hypertrophy which is appropriate to the body size of the athlete and the degree of activity but not to its type.

Increased left ventricular function as an adaptive response in vibration disease

Vibration disease results from the long-term use of vibrating tools. Vibration, noise, and cold are stressors that impair the human body, inducing vibration disease. From echocardiographic methods, the left ventricular ejection fraction in vibration disease was 79 +/- 4%, a significantly higher value than that in control subjects (75 +/- 6%) (p less than 0.01). The increase in ejection fraction appeared to be due mainly to an increase in left ventricular end-diastolic dimension. The value of the ejection fraction was proportional to the activity of the autonomic nerves. The stroke volume index in patients with vibration disease was also significantly larger than that in the control subjects (p less than 0.001). Electrocardiograms revealed a significantly lower heart rate at rest and an increase in the ratio of T waves to R waves in precordial lead V6. These data suggest that the cardiovascular system in patients with vibration disease provides an adaptive response to the stressors.

Resting ECG in athletic and non-athletic adolescent boys: correlations with heart volume and cardiorespiratory fitness

Resting ECG was recorded in 59 endurance trained athletic and 81 non-athletic boys aged 10-17 years and the findings were correlated with heart volume and cardiorespiratory fitness. The two groups were physically similar, but the athletes had significantly higher maximal oxygen uptake and the 15-17-year-old athletes had larger heart volumes. ECG findings were rather similar in both groups, the major differences being a lower heart rate in the athletes than in the controls (71 vs 82 beats/min) and a longer PQ interval (0.151 vs. 0.140 s) and a greater sum of SV2 and RV4 (59 vs. 50 mm) in the 15-17-year-old athletes. In the controls no correlation existed between precordial voltage criteria for ventricular hypertrophy and heart volume or between heart volume and cardiorespiratory fitness. Contrary to this, in the athletes both SV2 + RV5 and SV2 + RV4 correlated significantly (r about 0.40) with relative heart volume, and relative heart volume with both maximal oxygen uptake per kg (r = 0.41) and calculated work at heart rate 170 beats/min expressed per kg (r = 0.61). Our findings seem to indicate that as a consequence of endurance training the high level of cardiorespiratory fitness becomes related to a large heart volume. It is obvious that ECG changes due to relative vagal dominance develop earlier in the adolescent athletes than those attributable to anatomical changes.