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

Atrial fibrillation and anabolic steroids

A young male bodybuilder, consuming large doses of anabolic steroids (AS), presented to the Emergency Department (ED) with symptomatic rapid atrial fibrillation (AF). Echocardiogram revealed significant septal hypokinesis, and posterior and septal wall thickness at the upper limit of normal for highly trained athletes. The atrial fibrillation had not recurred at 10 weeks after discontinuation of AS use. Consumption of these agents in athletes has been associated with hypertension, ischemic heart disease, hypertrophic cardiomyopathy, and sudden death.

QT dispersion in exercise-induced myocardial hypertrophy

BACKGROUND

The measurement of QT dispersion in the surface electrocardiogram is a noninvasive method used for assessing inhomogeneity of myocardial repolarization. Elevated QT dispersion is found in myocardial disease and is associated with an increased incidence of arrhythmic events. QT dispersion is also increased in myocardial hypertrophy secondary to systemic hypertension. However, the relation between left ventricular (LV) enlargement in endurance trained subjects and QT dispersion is unknown.

METHODS AND RESULTS

In this study, LV mass (2-dimensional echocardiography) and QT dispersion (12-lead resting electrocardiogram) were assessed in 26 normotensive endurance trained subjects and 26 matched, less trained control subjects. Endurance trained subjects had a significantly greater LV mass (216 +/- 39 g vs 155 +/- 30 g, P <.001) but lower heart rate-corrected QTc dispersion (42 +/- 13 ms vs 51 +/- 15 ms, P =.012) than less trained control subjects. When all individuals were included, LV mass was inversely correlated with QT dispersion (r = -0.38; P =.002) and heart rate-corrected QTc dispersion (r = -0.53, P <.0001).

CONCLUSIONS

These data show that myocardial hypertrophy induced by exercise training is not associated with increased QT dispersion as observed in systemic hypertension. The reduced QT dispersion reflects homogeneous myocardial repolarization and may help to explain the reduced mortality rate in regularly exercising subjects. If confirmed in further studies, the measurement of QT dispersion could provide a simple and inexpensive screening method for differentiating between physiologic and pathologic myocardial hypertrophy.

Left ventricular morphology and function in endurance-trained female athletes

In this study, we investigated resting left ventricular dimensions and function in trained female rowers, canoeists and cyclists. In male populations, such athletes have demonstrated the largest left ventricular wall thicknesses and cavity dimensions. Echocardiograms were analysed from 24 athletes (rowers and canoeists, n = 12; cyclists, n = 12) and 21 age-matched controls to measure left ventricular end-diastolic dimension and volume, and septal (ST) and posterior wall (PWT) thicknesses. Left ventricular mass was calculated from M-mode data. Systolic and diastolic function were calculated from M-mode and Doppler echocardiography, respectively. Height, body mass, body surface area and fat-free mass were determined anthropometrically. The athletes were well matched with the controls for all anthropometric variables except fat-free mass (rowers and canoeists 49.7+/-3.6 kg, cyclists 48.0+/-3.8 kg, controls 45.0+/-5.4 kg; P < 0.05). The left ventricular end-diastolic dimension, mass and volume, and septal and posterior wall thicknesses, were all significantly greater in the athletes than the controls (P < 0.05). These differences persisted (except for left ventricular end-diastolic dimension) even after allometric adjustment for group differences in fat-free mass. Stroke volume was larger (rowers and canoeists 102+/-13 ml, cyclists 103+/-16 ml, controls 80+/-15 ml; P < 0.05) in both groups of athletes but all other functional data were similar between groups. As in male athletes, female rowers, canoeists and cyclists displayed significantly larger left ventricular cavity dimensions and wall thicknesses than controls.

Correlation of heart rate variability with cardiac functional and metabolic variables in cyclists with training induced left ventricular hypertrophy

OBJECTIVE

To examine the correlation between heart rate variability and left ventricular mass in cyclists with an athlete's heart.

METHODS

Left ventricular mass and diastolic function were determined at rest and myocardial high energy phosphates were quantified at rest and during atropine-dobutamine stress in 12 male cyclists and 10 control subjects, using magnetic resonance techniques. Ambulatory 24 hour ECG recordings were obtained, and time and frequency domain heart rate variability indices were computed.

RESULTS

In the cyclists, the mean of all RR intervals between normal beats (meanNN), the SD of the RR intervals, and their coefficient of variation were significantly greater than in control subjects (p < 0.01, p < 0.01, and p < 0.05, respectively). For cyclists and control subjects, only meanNN correlated with left ventricular mass (r = 0.48, p = 0.038). The heart rate variability indices that correlated with functional or metabolic variables were: meanNN v E/A peak (the ratio of peak early and peak atrial filling rate) (r = 0.48, p = 0.039); the root mean square of successive differences in RR intervals among successive normal beats v E/A area (ratio of peak early and peak atrial filling volume) (r = 0.48, p = 0.040); percentage of successive RR intervals differing by more than 50 ms v the phosphocreatine to ATP ratio at rest (r = 0.54, p = 0. 017); and the SD of the average RR intervals during all five minute periods v the phosphocreatine to ATP ratio during stress (r = 0.60, p = 0.007).

CONCLUSIONS

Highly trained cyclists have increased heart rate variability indices, reflecting increased cardiac vagal control compared with control subjects. Left ventricular mass has no major influence on heart rate variability, but heart rate variability is significantly correlated with high energy phosphate metabolism and diastolic function.

Musculoskeletal rehabilitation and sports medicine. 4. Miscellaneous sports medicine topics

This self-directed learning module highlights new advances in this topic area. It is part of the chapter on musculoskeletal rehabilitation and sports medicine in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article discusses physiatric duties as a team physician, preparticipation physical examinations, ergogenic aids, heat-related illness, pediatric sports injuries, female sports injuries, and sports medicine topics pertinent to geriatric and physically or mentally challenged athletes. New advances covered in this section include use of creatine, guidelines for the preparticipation examination, sudden cardiac athletic death, pediatric and female anterior cruciate ligament injuries, the female athlete triad, spine screening in Down syndrome athletes, and "boosting" in athletes with spinal cord injury.

Range of tricuspid regurgitation velocity at rest and during exercise in normal adult men: implications for the diagnosis of pulmonary hypertension

OBJECTIVES

The aim of this study was to explore the full range of tricuspid valve regurgitation velocity (TRV) at rest and with exercise in disease free individuals. Additionally we examined the relationship of stroke volume (SV), cardiac output (CO) and TRV to exercise capacity.

BACKGROUND

Doppler evaluation of TRV can be used to estimate pulmonary artery systolic pressure (PASP). Most studies have assumed TRV < or = 2.5 m/s as the upper limits of normal. The full range of TRV with exercise has been incompletely defined.

METHODS

Highly conditioned athletes (n = 26) and healthy, active, young male volunteers (n = 14) underwent standardized recumbent bicycle exercise. Exercise parameters included: TRV, SV, CO, systolic (SBP) and diastolic (DBP) systemic blood pressure.

RESULTS

Tricuspid valve regurgitation, SV, HR and CO were significantly higher in athletes than in nonathletes over all workloads, including rest. Systolic blood pressure and DBP did not show significant differences between the two groups.

CONCLUSIONS

This study defines the upper physiologic limits of TRV at rest and during exercise in normals and provides a noninvasive standard for the diagnosis of pulmonary hypertension.

Echocardiographic examination of cardiac structure and function in elite cross trained male and female Alpine skiers

OBJECTIVE

To assess cardiac structure and function in elite cross-trained male and female athletes (Alpine skiers).

METHODS

Sixteen athletes (10 male, six female) and 19 healthy sedentary control subjects (12 male, seven female) volunteered to take part in the study. Basic anthropometry determined height, body mass, body surface area, and fat free mass. Cardiac dimensions and function were determined by two dimensional, M mode, and Doppler echocardiography. Absolute data and data corrected for body size (allometrically determined) were compared by two way analysis of variance and post hoc Scheffé tests.

RESULTS

Absolute left ventricular internal dimension in diastole (LVIDd), septal and posterior wall thickness and left ventricular mass were larger in athletes than controls (p < 0.05) and also increased in the men (p < 0.05) compared with women (except for septal thickness in controls). An increased LVIDd, septal thickness, posterior wall thickness, and left ventricular mass in athletes persisted after correction for body size except when LVIDd was scaled by fat free mass. Cardiac dimensions did not differ between the sexes after correction for body size. All functional indices were similar between groups.

CONCLUSION

There is evidence of both left ventricular chamber dilatation and wall enlargement in cross trained athletes compared with controls. Differences in absolute cardiac dimensions between the sexes were primarily due to greater body dimensions in the men.

Why is left ventricular hypertrophy so predictive of morbidity and mortality?

The prevalence, prognosis, and predictors of left ventricular hypertrophy (LVH) are reviewed, and theories of the pathogenesis of the relation between LVH and poor prognosis are summarized to highlight controversies in the field. In the Framingham Heart Study, which consists largely of white people, echocardiographic LVH has a prevalence of 14% in men and 18% in women. The prevalence of LVH is reported to be elevated in African Americans compared with whites, although the higher prevalence has been attributed to the increased prevalence of hypertension and obesity. Echocardiographic LVH is independently associated with a variety of cardiovascular endpoints, including coronary heart disease and stroke. Furthermore, after adjusting for other cardiovascular disease risk factors, LVH is associated with a doubling in mortality in both white and African American cohorts. Despite the intensive investigation of LVH, there remain many unanswered questions: To what extent do genetic or other factors account for the large portion of the variance in LVH that remains unexplained? What is the prognosis of LVH and left ventricular geometry in a population-based African American cohort? How does the development and progression of LVH relate to other risk factors and their treatment? What is the relation of LVH to poor prognosis? The proposed Jackson Heart Study will help address many important unanswered questions regarding LVH.

Cardiovascular disease in athletes

As a physician, coach, or trainer, we see athletes as healthy, physically fit, and able to tolerate extremes of physical endurance. It seems improbable that such athletes may have, on occasion, underlying life-threatening cardiovascular abnormalities. Regular physical activity promulgates cardiovascular fitness and lowers the risk of cardiac disease. However, under intense physical exertion and with a substrate of significant cardiac disease--whether congenital or acquired--athletes may succumb to sudden cardiac death. The deaths of high-profile athletes receive much attention through the national news media, but there are also deaths of other athletes. With repetitive, intense physical exercise, the heart undergoes functional and morphologic changes. Knowledge of those changes may help one identify cardiovascular abnormalities that can cause sudden death from the heart known as an "athlete's heart." This article will review cardiovascular diseases that may limit an athlete's participation in sports and that may put an athlete at risk for sudden cardiac death. It also reviews the extent and limitations of the cardiovascular preparticipation screening examination. Team physicians, coaches, and trainers must understand the process of evaluation of a symptomatic athlete that may indicate significant cardiac abnormalities. Finally, guidelines to determine eligibility of athletes with cardiovascular disease to return to sports will be reviewed.

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.

Effect of endurance training on cardiac morphology in Alaskan sled dogs

The cardiac morphology of 77 conscious Alaskan sled dogs before and after 5 mo of endurance training (20 km/day team pulling a sled and musher) was studied using two-dimensional and M-mode echocardiography. Subgroups included dogs with at least one season of previous training ("veterans") and dogs undergoing their first season of training ("rookies"). Training resulted in a significant (P < 0.05) decrease in resting heart rate (-15%) and significant increases in interventricular septal thickness (systole, 15%; diastole, 13%), left ventricular (LV) internal dimension in diastole (LVIDd, 4%), LV free wall thickness in systole (9%) and diastole (LVWd, 9%), and left atrial diameter (5%) in all dogs, but the increase in LVWd was greater in rookies (16%) than in veterans (7%). Training increased end-diastolic volume index (8%), LV mass index (24%), and heart weight index (24%) and decreased the LVIDd-to-LVWd ratio (-6%) but did not alter cardiac index. We conclude that increased LV mass attributable to LV dilation and hypertrophy is associated with endurance training in Alaskan sled dogs. Disproportionate LV wall thickening accompanying LV dilation suggests that cardiac morphological changes are due to volume and pressure loading. These training-induced changes are similar to those documented in human athletes undergoing combined isometric and isotonic training and differ from studies of dogs trained on treadmills.

Screening for hypertrophic cardiomyopathy in young athletes

BACKGROUND

For more than 20 years in Italy, young athletes have been screened before participating in competitive sports. We assessed whether this strategy results in the prevention of sudden death from hypertrophic cardiomyopathy, a common cardiovascular cause of death in young athletes.

METHODS

We prospectively studied sudden deaths among athletes and nonathletes (35 years of age or less) in the Veneto region of Italy from 1979 to 1996. The causes of sudden death in both populations were compared, and the pathological findings in the athletes were related to their clinical histories and electrocardiograms. Cardiovascular reasons for disqualification from participation in sports were investigated and follow-up was performed in a consecutive series of 33,735 young athletes who underwent preparticipation screening in Padua during the same period.

RESULTS

Of 269 sudden deaths in young people, 49 occurred in competitive athletes (44 male and 5 female athletes; mean age, 23+/-7 years). The most common causes of sudden death in athletes were arrhythmogenic right ventricular cardiomyopathy (22.4 percent), coronary atherosclerosis (18.4 percent), and anomalous origin of a coronary artery (12.2 percent). Hypertrophic cardiomyopathy caused only 1 sudden death among the athletes (2.0 percent) but caused 16 sudden deaths in the nonathletes (7.3 percent). Hypertrophic cardiomyopathy was detected in 22 athletes (0.07 percent) at preparticipation screening and accounted for 3.5 percent of the cardiovascular reasons for disqualification. None of the disqualified athletes with hypertrophic cardiomyopathy died during a mean follow-up period of 8.2+/-5 years.

CONCLUSIONS

The results show that hypertrophic cardiomyopathy was an uncommon cause of death in these young competitive athletes and suggest that the identification and disqualification of affected athletes at screening before participation in competitive sports may have prevented sudden death.

Echocardiographic parameters in training compared with non-training greyhounds

Echocardiographic parameters were compared between training and non-training greyhound dogs. When indexed to body weight there was a statistically significant increase (p < 0.05) in the interventricular septal thickness (systole) and when indexed to body surface area there were increased interventricular septal (systole) and left ventricular free wall measurements (systole) in training compared with non-training greyhounds. When each gender was analyzed separately and echocardiographic parameters were indexed to body size, both genders had an increase in the interventricular septal thickness (diastolic in the female, systolic in the male) in the training compared with non-training greyhounds. In male training greyhounds there was additionally an increase in the left ventricular internal dimension (systole) and free wall thickness (systole) when echocardiographic parameters were indexed to body surface area compared with non-training greyhounds (p < 0.05). The results indicate that certain training greyhound echocardiographic parameters are larger than non-training greyhound echocardiographic parameters. The potential effects of training, body size and gender should be considered when interpreting echocardiographic parameters in populations of greyhounds.

The cardiac toxicity of anabolic steroids

Anabolic steroids are synthetic derivatives of testosterone that were developed as adjunct therapy for a variety of medical conditions. Today they are most commonly used to enhance athletic performance and muscular development. Both illicit and medically indicated anabolic steroid use have been temporally associated with many subsequent defects within each of the body systems. Testosterone is the preferred ligand of the human androgen receptor in the myocardium and directly modulates transcription, translation, and enzyme function. Consequent alterations of cellular pathology and organ physiology are similar to those seen with heart failure and cardiomyopathy. Hypertension, ventricular remodeling, myocardial ischemia, and sudden cardiac death have each been temporally and causally associated with anabolic steroid use in humans. These effects persist long after use has been discontinued and have significant impact on subsequent morbidity and mortality. The mechanisms of cardiac disease as a result of anabolic steroid use are discussed in this review.

Are insulin metabolism and night-time blood pressure related to left ventricular hypertrophy?

Essential hypertensives in whom blood pressure does not fall during sleep (non-dippers) are thought to be at greater risk of cardiovascular morbidity. Insulin resistance is also suggested to be a risk factor for cardiovascular morbidity. The purpose of the present study was to evaluate the relationship of insulin metabolism to left ventricular hypertrophy in dippers and non-dippers. Thirty male, non-diabetic out-patients with newly diagnosed arterial hypertension were included in the study: 21 dippers (mean age 45+/-13 years; body mass index 28.2+/-4.0 kg/m2) and nine non-dippers (mean age 48+/-10 years, body mass index 28.6+/-3.9 kg/m2). Patients were subdivided into dippers and non-dippers on the basis of 24-h ambulatory blood pressure monitoring. Insulin and glucose responses to an oral glucose load have been evaluated. C-peptide levels were determined. Left ventricular mass was assessed by echocardiography. Non-dippers had significantly higher mean night-time systolic (non-dippers: 148+/-9; dippers: 123+/-16 mmHg; P<0.001), diastolic blood pressure (non-dippers: 90+/-8; dippers: 77+/-8 mmHg; P<0.001) and non-significantly higher left ventricular mass (279+/-92 g) and left ventricular mass index (135+/-46 g/m2). No significant difference was found between C-peptide, insulin, glucose levels and incremental areas between the two groups. Night-time blood pressure, insulin, C-peptide and glucose did not correlate with left ventricular mass in non-dippers. Dippers showed a positive correlation between fasting C-peptide and left ventricular mass (r=0.48, P=0.02) and between glucose and left ventricular mass (r=0.42, P=0.05). Our data indicate that night-time blood pressure and insulin are not related to left ventricular hypertrophy in patients with essential hypertension.

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.

Pathological versus physiological left ventricular hypertrophy: a review

Left ventricular hypertrophy is recognized as an independent risk factor for cardiovascular morbid events. The primary mechanisms responsible for stimulating it are unknown. Epidemiological theories suggest that left ventricular hypertrophy is a continuous variable with no threshold, while morphological studies argue that it is the structure, or quality, and function of the myocardium (and therefore non-continuous), not the quantity of the myocardial mass, that poses the cardiovascular risk. Although left ventricular hypertrophy has been classically viewed as an adaptive response of the cardiovascular system to an imposed load, it has been demonstrated that haemodynamic overloading in selected hypertensive patients is not the sole determinant of left ventricular structure and function. Pathological and physiological states of left ventricular hypertrophy have been described primarily using criteria focusing on normal chamber performance and oxygen delivery as well as the reversibility of the hypertrophy once the overload is removed. Both states are also defined by the nature of the imposed load and the resulting myocardial adaptations. This review addresses the pathological and physiological states of left ventricular hypertrophy, the hypertrophy patterns, and the corresponding structural and functional characteristics, together with some of the biochemical factors thought to influence remodelling.

Comparison of coronary vasodilator reserve in elite rowing athletes versus hypertrophic cardiomyopathy

Compared to normal volunteers, coronary vasodilation reserve is reduced in patients with hypertrophic cardiomyopathy but not in rowing athletes with left ventricular hypertrophy. Positron emission tomography can provide complementary information to distinguish between the athlete's heart and hypertrophic cardiomyopathy.

Left ventricular hypertrophy in athletes

Left ventricular wall thickness >1.3 cm, septal-to-posterior wall ratios > 1.5, diastolic left ventricular size >6.0 cm, and eccentric or concentric remodeling are rare in athletes. Values outside of these cutoffs in an athlete of any age probably represent a pathologic state.

Differences in myocardial velocity gradient measured throughout the cardiac cycle in patients with hypertrophic cardiomyopathy, athletes and patients with left ventricular hypertrophy due to hypertension

OBJECTIVES

We sought to compare the myocardial velocity gradient (MVG) measured across the left ventricular (LV) posterior wall during the cardiac cycle between patients with hypertrophic cardiomyopathy (HCM), athletes and patients with LV hypertrophy due to systemic hypertension and to determine whether it might be used to discriminate these groups.

BACKGROUND

The MVG is a new ultrasound variable, based on the color Doppler technique, that quantifies the spatial distribution of transmyocardial velocities.

METHODS

A cohort of 158 subjects was subdivided by age into two groups: Group I (mean [+/-SD] 30 +/- 7 years) and Group II (58 +/- 8 years). Within each group there were three categories of subjects: Group Ia consisted of patients with HCM (n = 25), Group Ib consisted of athletes (n = 21), and Group Ic consisted of normal subjects; Group IIa consisted of patients with HCM (n = 19), Group IIb consisted of hypertensive patients (n = 27), and Group IIc consisted of normal subjects (n = 33).

RESULTS

The MVG (mean [+/-SD] s-1) measured in systole was lower (p < 0.01) in patients with HCM (Group Ia 3.2 +/- 1.1; Group IIa 2.9 +/- 1.2) compared with athletes (Group Ib 4.6 +/- 1.1), hypertensive patients (Group IIb 4.2 +/- 1.8) and normal subjects (Group Ic 4.4 +/- 0.8; Group IIc 4.8 +/- 0.8). In early diastole, the MVG was lower (p < 0.05) in patients with HCM (Group Ia 3.7 +/- 1.5; Group IIa 2.6 +/- 0.9) than in athletes (Group Ib 9.9 +/- 1.9) and normal subjects (Group Ic 9.2 +/- 2.0; Group IIc 3.6 +/- 1.5), but not hypertensive patients (Group IIb 3.3 +/- 1.3). In late diastole, the MVG in patients with HCM (Group Ia 1.3 +/- 0.8; Group IIa 1.4 +/- 0.8) was lower (p < 0.01) than that in hypertensive patients (Group IIb 4.3 +/- 1.7) and normal subjects (Group IIc 3.8 +/- 0.9). An MVG < or = 7 s-1, as a single diagnostic approach, differentiated accurately (0.96 positive and 0.94 negative predictive value) between patients with HCM and athletes when the measurements were taken during early diastole.

CONCLUSIONS

In both age groups, the MVG was lower in both systole and diastole in patients with HCM than in athletes, hypertensive patients or normal subjects. The MVG measured in early diastole in a group of subjects 18 to 45 years old would appear to be an accurate variable used to discriminate between HCM and hypertrophy in athletes.

Association of angiotensin-converting enzyme gene I/D polymorphism with change in left ventricular mass in response to physical training

BACKGROUND

The absence (deletion allele [D]) of a 287-base pair marker in the ACE gene is associated with higher ACE levels than its presence (insertion allele [I]). If renin-angiotensin systems regulate left ventricular (LV) growth, then individuals of DD genotype might show a greater hypertrophic response than those of II genotype. We tested this hypothesis by studying exercise-induced LV hypertrophy.

METHODS AND RESULTS

Echocardiographically determined LV dimensions and mass (n=140), electrocardiographically determined LV mass and frequency of LV hypertrophy (LVH) (n=121), and plasma brain natriuretic peptide (BNP) levels (n=49) were compared at the start and end of a 10-week physical training period in male Caucasian military recruits. Septal and posterior wall thicknesses increased with training, and LV mass increased by 18% (all P<.0001). Response magnitude was strongly associated with ACE genotype: mean LV mass altered by +2.0, +38.5, and +42.3 g in II, ID and DD, respectively (P<.0001). The prevalence of electrocardiographically defined LVH rose significantly only among those of DD genotype (from 6 of 24 before training to 11 of 24 after training, P<.01). Plasma brain natriuretic peptide levels rose by 56.0 and 11.5 pg/mL for DD and II, respectively (P<.001).

CONCLUSIONS

Exercise-induced LV growth in young males is strongly associated with the ACE I/D polymorphism.

The morphologic consequences of systemic training

The development of echocardiography in the 1970s led to the flourishing of the study of the athlete's heart. From the earliest studies, it was apparent that athletes develop enlargement of the left ventricular cavity and thickening of myocardium in response to prolonged repetitive training. The changes in echocardiographic measurements are small and often within quoted normal ranges. By comparison to sedentary controls, however, left ventricular end-diastolic dimension is increased by approximately 10%, posterior wall dimension by 15% to 20%, and calculated mass by up to 45%.

The athlete's heart. Historical perspectives--solved and unsolved problems

Clinicians are coming back to Henschen's assessment of the athlete's heart as a physiologic and positive phenomenon. An athlete's heart may be affected by clinical conditions. Regarding the extreme performance of the athlete's heart in training and competition, conditions that may be harmless in sedentary people can be fatal for the athlete. The athlete's heart therefore deserves the particular interest and care of the sports cardiologist.

The power athlete

A number of normal daily and athletic activities require isometric or static exercise. Sports such as weight lifting and other high-resistance activities are used by power athletes to gain strength and skeletal muscle bulk. Static exercise, the predominant activity used in power training, significantly increases blood pressure, heart rate, myocardial contractility, and cardiac output. These changes occur in response to central neural irradiation, called central command, as well as a reflex originating from statically contracting muscle. Studies have demonstrated that blood pressure appears to be the regulated variable, presumably because the increased pressure provides blood flow into muscles whose arterial inflow is reduced as a result of increases in intramuscular pressure created by contraction. Thus, static exercise is characterized by a pressure load on the heart and can be differentiated from the hemodynamic response to dynamic (isotonic) exercise, which involves a volume load to the heart. Physical training with static exercise (i.e., power training) leads to concentric cardiac (particularly left ventricular) hypertrophy, whereas training with dynamic exercise leads to eccentric hypertrophy. The magnitude of cardiac hypertrophy is much less in athletes training with static than dynamic exercise. Neither systolic nor diastolic function is altered by the hypertrophic process associated with static exercise training. Many of the energy requirements for static exercise, particularly during more severe levels of exercise, are met by anaerobic glycolysis because the contracting muscle becomes comes deprived of blood flow. Power athletes, training with repetitive static exercise, derive little benefit from an increase in oxygen transport capacity, so that maximal oxygen consumption is increased only minimally or not at all. Peripheral cardiovascular adaptations also can occur in response to training with static exercise. Although the studies are controversial, these adaptations include modest decreases in resting blood pressure, reduced increases in blood pressure and sympathetic nerve activity during a given workload, enhanced baroreflex function, increases in muscle capillary-to-fiber ratio, possible improvements in lipid and lipoprotein profiles, and increases in glucose and insulin responsiveness. Some of these adaptations can occur in cardiac or hypertensive patients with no concomitant cardiovascular complications. In both healthy individuals and those with cardiovascular disease, the manner in which resistance training is performed may dictate the extent to which these adjustments take place. Specifically, training that involves frequent repetitions of moderate weight (and hence contains dynamic components) seems to produce the most beneficial results.

Mechanics of left ventricular systolic and diastolic function in physiologic hypertrophy of the athlete's heart

As a result of a number of factors, there is tremendous diversity in the pattern of cardiac mechanics encountered in athletes. Nevertheless, several trends can be identified, and several conclusions are possible. Hypertrophy of a mild to moderate degree and out of proportion to body size is a common finding. Some athletes experience ventricular dilation with appropriate hypertrophy and preservation of the ventricular mass-to-volume ratio, whereas others manifest concentric hypertrophy with an increased mass-to-volume ratio. The functional changes that are encountered appear to be secondary to the structural alterations, and there is no evidence of altered myocardial systolic or diastolic properties. Some athletes with hypertrophy have reduced wall stress when they are evaluated at rest, and velocity of shortening is augmented because of the reduced afterload. As a result of adaptation to a high-output state, some athletes appear preload reduced when evaluated at rest. Although velocity of shortening is not affected by preload status, fractional shortening is inversely related to preload. The magnitude of systolic shortening is therefore the net result of altered preload and afterload and cannot be understood without assessing both of these parameters. When the various determinants of systolic shortening are included, contractility appears to be normal. There have been several reports of depressed contractility immediately after extreme exertion. Although the mechanism remains uncertain, several intriguing possibilities have been proposed.

Outer limits of the athlete's heart, the effect of gender, and relevance to the differential diagnosis with primary cardiac diseases

Two concepts from pathologic descriptions of myocardial hypertrophy in trained individuals merit consideration: (1) The heart of the trained athlete can be twice the normal size, but histologic structure remains intact, and (2) the weight of the trained heart does not usually surpass the limit of 500 g, defined as the critical heart weight. Even though this threshold cannot be accepted dogmatically, the concept of an upper limit for physiologic cardiac remodeling is nevertheless relevant to the clinical question of distinguishing extreme expressions of athlete's heart from primary pathologic conditions. This morphologic distinction depends on whether the magnitude of cardiac remodeling in athletes exceeds that expected as a result of athletic conditioning alone. There has also been a great interest in understanding the impact that types of athletic conditioning and gender have on defining the upper limits to which such physiologic hypertrophy may extend.

Considerations for racial differences in the athlete's heart and related cardiovascular disease

Athletic training is often associated with modest increases in left ventricular chamber size, wall thickness, and mass, which appear to be related to the level and intensity of training as well as the type of activity performed. It appears that for given levels and types of training, some individuals show more marked morphologic changes. It has been speculated that the cardiac alterations that occur with athletic conditioning may be due, in part, to genetic factors that exist independent of training. Related to this issue is the possibility that racial (or biologic) differences in cardiac response to exercise may also exist. This article reviews the available data that address racial differences in the cardiac response to exercise and to left ventricular pressure overload and the implications of these findings.

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.

Risk profiles and cardiovascular preparticipation screening of competitive athletes

There has been heightened interest in the design and role of preparticipation screening for high school and college athletes. An American Heart Association consensus panel, composed of cardiovascular specialists and other physician experts having extensive clinical experience with athletes of all ages as well as a legal expert, assessed the benefits and limitations of preparticipation screening for early detection of cardiovascular abnormalities in competitive athletes. The panel addressed cost-efficiency and feasibility issues as well as the medicolegal implications of screening; and developed consensus recommendations and guidelines for the most prudent, practical, and effective screening procedures and strategies.

An echocardiographic study comparing male Swedish elite orienteers with other elite endurance athletes

Between 1979 and 1992, there were 16 known cases of sudden unexpected cardiac death among young Swedish orienteers, whose autopsies showed myocarditis to be a common finding. Therefore, 96 elite orienteers and 47 controls underwent echocardiography, showing left ventricular wall motion abnormalities in 9% of the orienteers compared with 4% in the controls.

Echocardiographic criteria of physiological left ventricular hypertrophy in combined strength- and endurance-trained athletes

In combined strength- and endurance-trained athletes who are showing both unusual large body dimensions as well as a high physical fitness, the dimensions of the 'athlete's heart' are expected to reach physiological limits. Therefore we investigated 75 male and 77 female competitive rowers by means of doppler-echocardiography. The absolute "critical" heart weight of 500 g was exceeded by 61% of the male and 10% of the female rowers. Maximal values of the left ventricular (LV) muscle mass were measured at 170 (men) and 133 (women) g.m-2 body surface area, respectively. The LV end-diastolic internal diameter was measured to be above the upper clinical limit of 55 mm in 55% of the male and 17% of the female rowers. A LV wall thickness of 13 and 12 mm was only exceeded by 3 male and 1 female athlete, respectively (maximal values: 14 and 12.5 mm). The LV wall/internal diameter ratio did not exceed 48-50%. The systolic LV function as well as ECG and blood pressure did not reveal any pathological finding, the diastolic LV function was always measured within the normal range. The LV wall thicknesses, internal diameter and hypertrophic index (relation between wall thickness and internal diameter) of the rowers were significantly higher than those of 62 non-endurance trained athletes (pairwise matched according to the body dimensions) and similar to 28 male 'pure' endurance athletes (pairwise matched according to the absolute heart volume). In conclusion, upper limits of echocardiographic volume measurements that are considered critical may be clearly exceeded by healthy strength-endurance trained athletes with simultaneously high body dimensions. The clinical limits, however, are still valid in subjects with a body mass up to approximately 70 kg. The LV wall thickness only exceptionally exceed the clinical limits. A specific influence of the strength elements in training on the LV hypertrophy had not be found.

New diagnostic options in hypertrophic cardiomyopathy

The pathophysiologic features and clinical manifestations of HCM have been elucidated by the introduction of several new diagnostic options. Knowledge of the molecular defects of HCM has advanced rapidly, and genetic screening studies have reemphasized the value of the standard electrocardiogram as an initial screening tool. Analysis of heart rate variability, late potentials, and QT dispersion were not found to be reliable prognostic markers in HCM. However, measurement of dispersion of conduction is probably a sensitive technique in identifying a high risk for sudden cardiac death. Significant developments include transthoracic and transesophageal echocardiography and their role in studying the mitral valve, early detection of left ventricular chamber dilatation, analysis of coronary flow, and intraoperative echocardiography. Finally, advances in the application of magnetic resonance imaging and positron-emission tomography are underway.

One year of exercise training does not alter resting left ventricular systolic or diastolic function

Few studies have examined the effect of prolonged exercise training on left ventricular diastolic function in previously sedentary subjects. We performed M-mode, 2-D, and Doppler echocardiography on 16 previously sedentary men before and after 1 yr of exercise training. Six men served as controls. Exercise subjects participated in four 1-h supervised sessions weekly at 60-80% of their measured maximal heart rate. Maximal oxygen uptake, maximal exercise cardiac output, and resting left ventricular systolic and diastolic function were determined before and after training. Maximal oxygen uptake and peak cardiac output increased 27.3% and 8.5% in the trainers (P < 0.001 for both) and 1.3% and 1.0% in the controls. Left ventricular diastolic and systolic dimensions changed slightly in both groups. Maximal early inflow velocity decreased in both trainers (-9.9 +/- 14.0 cm.s-1, mean +/- SD, P < or = 0.01) and controls (-7.2 +/- 10.2 cm.s-1). Maximal atrial inflow velocity decreased (-7.8 +/- 10.9 cm.s-1, P < or = 0.01) only in the trainers possibly because of a reduction in resting heart rate (-6 +/- 11 beats.m-1, P < or = 0.05). Acceleration and deceleration times were unchanged in both groups. These results demonstrate that substantial increases in exercise performance and exercise cardiac output can occur without detectable changes in resting cardiac dimensions or left ventricular systolic and diastolic function.

The heart of the senior oarsman: an echocardiographic evaluation

We evaluated left ventricular mass and function in 15 oarsmen aged 78 (65-82) yr (median and range) and in 15 sedentary males aged 72 (65-81) yr by 2-D and M-mode echocardiography and cycle ergometry. The weekly time spent exercising among the oarsmen was 6 (2-18) h and two of the oarsmen were former national and international champions. The two groups of subjects had similar weight, height, and resting blood pressure. The oarsmen reached a maximal work rate of 142 (117-174) vs 113 (75-150) W for the sedentary group (P < 0.01). The internal diameters of the left ventricle were not significantly different, but the septum and posterior wall thicknesses were larger in the oarsmen (11 (8-20) vs 9 (7-11) mm, and 9 (8-13) vs 8 (7-19) mm, respectively, P < 0.023). Thus, the left ventricular mass index of the oarsmen was 19% larger (127 (101-284) vs 103 (74-134) g.m-2, P < 0.01). Also, the systolic function appeared to be superior in the oarsmen as the fractional shortening was 0.45 (0.28-0.55) vs 0.36 (0.18-0.49) in the controls (P < 0.05). In conclusion, we found that long-term rowing in the senior oarsman is associated with enlarged myocardial wall thickness, a normal systolic function, and a high work capacity.

Resistance trained athletes using or not using anabolic steroids compared to runners: effects on cardiorespiratory variables, body composition, and plasma lipids

OBJECTIVE

To determine whether there is a difference in cardiac size and function as well as in body composition, aerobic capacity, and blood lipids between resistance trained athletes who use anabolic steroids and those who do not, and to compare them to university cross country athletes.

METHODS

Four groups of men were evaluated: recreational lifters, n = 11, lifting < 10 h.week-1; heavy lifters, n = 16, lifting > 10 h.week-1; steroid users, n = 8, same as heavy lifters and used steroids; runners, n = 8, university track members. Echocardiograms, body composition (hydrostatic weighing), maximum oxygen consumption (Vo2), and lipids were studied.

RESULTS

As expected, Vo2 (ml.kg-1.min-1), was greatest in the runners, with no difference among the lifting groups. High density lipoprotein cholesterol in the steroid user group was lower than in heavy lifters or runners. Left ventricular internal diastolic dimension was similar among the groups. The left ventricular mass index of the steroid user group was significantly greater than recreational lifters, at 161 v 103. There was no difference among heavy lifters (127), runners (124), and steroid users. There was no compromise in diastolic function in any group. There were no differences among groups in resting or exercise blood pressure.

CONCLUSIONS

Resistance training in the absence of steroid use results in the same positive effects on cardiac dimensions, diastolic function, and blood lipids as aerobic training.

Left ventricular volume and mass in children on growth hormone therapy compared with untreated children

The myotropic effects of growth hormone (GH) have long been known. An excess of GH as in acromegaly, causes various problems within the circulatory system including cardiac hypertrophy. Although the latter has not been reported as a complication of GH therapy in children, we assessed this possibility in 54 children. Ninety-six echocardiographic studies were performed, in which bisectional images were analysed by Simpson's rule to determine left ventricular volume and mass. Of special interest were 47 results obtained from girls with Ullrich-Turner-syndrome (UTS) treated with supraphysiological doses of GH. Our results showed a significant increase of the myocardial mass in children on GH therapy compared with untreated children, as well as a dose related effect of GH on cardiac mass in girls and cardiac volume in boys. No cardiac hypertrophy, however, could be observed; the increase in muscular mass merely amounting to a normalization of previously low values.

Increase of LDL susceptibility to oxidation occurring after intense, long duration aerobic exercise

The effect of heavy, long duration aerobic exercise on low density lipoprotein (LDL) susceptibility to oxidation and on distribution of LDL subfractions was studied. Six well-trained runners, previously fasted, ran continuously for 4 h. Controlled intake of liquid and food was permitted during exercise. Total plasma and LDL triglyceride increased significantly. LDL susceptibility to oxidation, measured as conjugated dienes formation, was modified significantly (P < or = 0.05) after running (14% reduction in lag phase time, and 8% increase in maximal curve slope). The percentage of electronegative LDL form (named LDLB) also increased significantly (P < or = 0.05) after exercise both basally (from 7.3% to 11%) and after 2h of induced oxidation (from 40.6% to 52.3%). Neither LDL susceptibility to oxidation nor increase of LDLB was statistically associated with food consumed during the race or modifications of triglycerides suggesting that this effect was due to exercise rather than food-related. The pattern of LDL subfractions was type A in all athletes before and after running. The oxidative LDL changes, seen in exercise conditions similar to those of hard training or competition, demonstrated an unfavourable effect of very intense exercise on lipoprotein metabolism.

Alteration of growth responses in established cardiac pressure overload hypertrophy in rats with aortic banding

We examined the acute effects of elevated wall stress, norepinephrine, and angiotensin II on cardiac protein synthesis as well as protooncogene expression in hearts with established pressure overload left ventricular hypertrophy. Isolated rat hearts with chronic hypertrophy (LVH) were studied 12 wk after ascending aortic banding when systolic function was fully maintained. New protein synthesis (incorporation of [3H]phenylalanine [Phe]) was analyzed in isolated perfused rat hearts after a 3-h protocol; c-fos, c-jun, c-myc, and early growth response gene-1 (EGR-1) mRNA levels (Northern blot) were studied over a time course from 15 to 240 min of perfusion. Under baseline conditions (i.e., before mechanical or neurohormonal stimulation), [3H]-Phe-incorporation (280 nmoles/gram protein/h) and protooncogene mRNA levels were similar in age-matched control and LVH hearts. However, hearts with chronic LVH were characterized by a markedly blunted or absent [3H]-Phe-incorporation after acute imposition of isovolumic systolic load (90 mmHg/gram left ventricle), as well as norepinephrine (10(-6)M), or angiotensin II infusion (10(-8)M plus prazosin 10(-7)M) compared with nonhypertrophied control hearts. Similarly, stimulation of LVH hearts with acute systolic load or norepinephrine was associated with a significantly blunted increase of protooncogene mRNA levels relative to control hearts. The blunted induction of c-fos mRNA in LVH hearts was not due to feedback inhibition, since cycloheximide perfusion of hearts exposed to elevated wall stress further increased the differences between age-matched control and LVH hearts. The data suggest that acute molecular growth responses to mechanical or neurohormonal stimulation are altered in rat hearts with established LVH relative to nonhypertrophied control hearts. This alteration of molecular adaptations in hearts with compensatory hypertrophy may prevent inappropriate excess cardiac growth in response to mechanical and neurohormonal stimuli.

Effects of regular exercise on blood pressure and left ventricular hypertrophy in African-American men with severe hypertension

BACKGROUND

The prevalence of hypertension and its cardiovascular complications is higher in African Americans than in whites. Interventions to control blood pressure in this population are particularly important. Regular exercise lowers blood pressure in patients with mild-to-moderate hypertension, but its effects in patients with severe hypertension have not been studied. We examined the effects of moderately intense exercise on blood pressure and left ventricular hypertrophy in African-American men with severe hypertension.

METHODS

We randomly assigned 46 men 35 to 76 years of age to exercise plus antihypertensive medication (23 men) or antihypertensive medication alone (23 men). A total of 18 men in the exercise group completed 16 weeks of exercise, and 14 completed 32 weeks of exercise, which was performed three times per week at 60 to 80 percent of the maximal heart rate.

RESULTS

After 16 weeks, mean (+/- SD) diastolic blood pressure had decreased from 88 +/- 7 to 83 +/- 8 mm Hg in the patients who exercised, whereas it had increased slightly, from 88 +/- 6 to 90 +/- 7 mm Hg, in those who did not exercise (P = 0.002). Diastolic blood pressure remained significantly lower after 32 weeks of exercise, even with substantial reductions in the dose of antihypertensive medication. In addition, the thickness of the interventricular septum (P = 0.03), the left ventricular mass (P = 0.02), and the mass index (P = 0.04) had decreased significantly after 16 weeks in the patients who exercised, whereas there was no significant change in the nonexercisers.

CONCLUSIONS

Regular exercise reduced blood pressure and left ventricular hypertrophy in African-American men with severe hypertension.

Gender-specific reference M-mode values in adults: population-derived values with consideration of the impact of height

OBJECTIVES

The purpose of this investigation was to derive population-based reference values for M-mode echocardiographic dimensions that can be applied in epidemiologic studies, clinical trials and clinical practice and to determine optimal methods for adjusting these dimensions for body size.

BACKGROUND

M-mode echocardiography remains an important modality for studying cardiovascular disease; this is especially true with regard to detecting target organ damage in systemic hypertension. Most previously published reference values were derived from hospital-based series or relatively small samples and were not gender specific.

METHODS

Using a sample of 288 men and 524 women who were between 20 and 45 years of age and who were free of cardiovascular disease, reference values were derived for end-diastolic and end-systolic left ventricular internal dimensions, left ventricular wall thickness and left atrial dimension. The relations between these dimensions and height, a measure of body size relatively independent of obesity, were investigated using various regression models.

RESULTS

Nomograms for mean and 95th percentile values in men and women were constructed on the basis of linear regression models relating echocardiographic dimensions to height. Adjustment for body surface area greatly attenuated associations between obesity and cardiac dimensions in a separate healthy but less restricted sample of 411 men and 503 women.

CONCLUSIONS

Gender-specific M-mode reference values and nomograms, with mean and 95th percentile values for echocardiographic dimensions as a function of height, are reported. The use of body surface area as means of body size adjustment is called into question.

Prevalence and upper limit of cardiac hypertrophy in professional cyclists

The term athlete's heart refers to an increased left ventricular mass. Few studies have assessed the prevalence and normal upper limit of cardiac hypertrophy in highly trained cyclists and this was the aim of this study. A group of 40 professional road cyclists [mean age 26 (SD 3) years] who had participated in European competitions for 3-10 years, were evaluated at the beginning of the 1992-93 season. Evaluation included a clinical history and physical examination, one and two-dimensional echocardiography, 12-lead resting electrocardiogram and a graded exercise test. Determination of the left ventricular mass index (LVMI) was performed using Devereux's formula with correction for the body surface area. Systolic and diastolic blood pressure were measured at rest and at peak exercise. Of the group 23 cyclists (58%) presented a LVMI greater than 130 g.m-2, 21 cyclists presented a diastolic ventricular thickness equal to or greater than 13 mm, with a superior limit of 19 mm; 3 cyclists presented asymmetrical septum hypertrophy; and the relationship between posterior wall and left ventricular diastolic radius was equal to or greater than 0.45 in 14 cases (35%). Electrocardiographic abnormalities of ST-T segment were seen in only 1 subject. No correlation was found between the degree of ventricular hypertrophy and arterial blood pressure. We concluded that these professional cyclists showed a high prevalence of cardiac hypertrophy (58%). The distribution of this hypertrophy was concentric in 20/33 and asymmetric in 3/23 of the subjects with left ventricular hypertrophy. The electrocardiograms were normal in 98% of the subjects.