ELECTROCARDIOGRAMS OF MARATHON RUNNERS IN 1962 COMMONWEALTH GAMES

Electrocardiograms of mice selectively bred for high levels of voluntary exercise: Effects of short-term exercise training and the mini-muscle phenotype

Changes in cardiac function that occur with exercise training have been studied in detail, but those accompanying evolved increases in the duration or intensity of physical activity are poorly understood. To address this gap, we studied electrocardiograms (ECGs) of mice from an artificial selection experiment in which four replicate lines are bred for high voluntary wheel running (HR) while four non-selected lines are maintained as controls (C). ECGs were recorded using an ECGenie (Mouse Specifics, Inc.) both before and after six days of wheel access (as used in the standard protocol to select breeders). We hypothesized that HR mice would show innate differences in ECG characteristics and that the response to training would be greater in HR mice relative to C mice because the former run more. After wheel access, in statistical analyses controlling for variation in body mass, all mice had lower heart rates, and mice from HR lines had longer PR intervals than C lines. Also after wheel access, male mice had increased heart rate variability, whereas females had decreased heart rate variability. With body mass as a covariate, six days of wheel access significantly increased ventricle mass in both HR and C males. Within the HR lines, a subset of mice known as mini-muscle individuals have a 50% reduction in hindlimb muscle mass and generally larger internal organs, including the heart ventricles. As compared with normal-muscled individuals, mini-muscle individuals had a longer QRS complex, both before and after wheel access. Some studies in other species of mammals have shown correlations between athletic performance and QRS duration. Correlations between wheel running and either heart rate or QRS duration (before wheel running) among the eight individual lines of the HR selection experiment or among 17 inbred mouse strains taken from the literature were not statistically significant. However, total revolutions and average speed were negatively correlated with PR duration among lines of the HR selection experiment for males, and duration of running was negatively correlated with PR duration among 17 inbred strains for females. We conclude that HR mice have enhanced trainability of cardiac function as compared with C mice (as indicated by their longer PR duration after wheel access), and that the mini-muscle phenotype causes cardiac changes that have been associated with increased athletic performance in previous studies of mammals.

Impact of ethnicity on cardiac adaptation to exercise

The increasing globalization of sport has resulted in athletes from a wide range of ethnicities emerging onto the world stage. Fuelled by the untimely death of a number of young professional athletes, data generated from the parallel increase in preparticipation cardiovascular evaluation has indicated that ethnicity has a substantial influence on cardiac adaptation to exercise. From this perspective, the group most intensively studied comprises athletes of African or Afro-Caribbean ethnicity (black athletes), an ever-increasing number of whom are competing at the highest levels of sport and who often exhibit profound electrical and structural cardiac changes in response to exercise. Data on other ethnic cohorts are emerging, but remain incomplete. This Review describes our current knowledge on the impact of ethnicity on cardiac adaptation to exercise, starting with white athletes in whom the physiological electrical and structural changes--collectively termed the 'athlete's heart'--were first described. Discussion of the differences in the cardiac changes between ethnicities, with a focus on black athletes, and of the challenges that these variations can produce for the evaluating physician is also provided. The impact of ethnically mediated changes on preparticipation cardiovascular evaluation is highlighted, particularly with respect to false positive results, and potential genetic mechanisms underlying racial differences in cardiac adaptation to exercise are described.

ECG aberrations, latent coronary heart disease and cardiopulmonary fitness in various age groups of Norwegian cross-country skiers

To assess the prevalence of possible, latent coronary heart disease (CHD) among physically active men, 149 elite cross-country skiers in three age groups (26-33, 43-50 and 58-64 years) were invited for an examination which included clinical examination, Vitalogram, resting ECG, and a near maximal bicycle test. Of the invited men, 122 participated, i.e. 81.8%. The following findings were made: Normal clinical findings in all except 2, low resting heart rate, lung function parameters of about normal mean; voltage signs of left ventricular hypertrophy in resting ECG in 61/122, incomplete right bundle branch block in 14/122, codable Q waves (Minnesota Code, MC) in 5/87 from the highest age groups, ischaemic exercise ECG changes of MC 4.1 or 4.2 types in 11/87 vs. 1/35 in the two oldest vs. the youngest age group. Physical performance was very high in all age groups, but regular training did not seem to inhibit the normal age-dependent decline in physical performance. The resting and exercise ECG data in the two oldest age groups did not differ favourably from similar data obtained in sedentary men of the same age from approximately the same geophraphic area. Thus, it is possible that regular strenuous exercise and training may not protect against the development of CHD. The implications of such a view are briefly discussed.

Five-year follow-up of ECG aberrations, latent coronary heart disease and cardiopulmonary fitness in various age groups of Norwegian cross-country skiers

A cross-sectional sample of 122 middle-aged and elderly long-time active, well-trained male cross-country skiers were studied in 1976 to assess the prevalence of possible latent coronary heart disease (CHD). One hundred and seventeen skiers were reexamined five years later to assess the prognostic significance of a number of ECG aberrations encountered in 1976, and to assess the CHD incidence among athletes. One had died and four did not participate in the restudy, but none of these five men had had cardiac disease. The findings at the time of the two surveys were remarkably similar. All had excellent physical performance and a stable life habit pattern. Only three had given up regular training in the observation period. There was a very high prevalence of sinus bradycardia, first degree AV blocks, left ventricular hypertrophy (LVH) and incomplete right bundle branch block. Pathologic exercise ECGs were found on both occasions. Of 23 men with "pathologic" exercise ECG, 21 had LVH. Five had codable Q waves according to the Minnesota code, but none had symptoms of CHD. Two developed angina pectoris during the follow-up and none had had myocardial infarction. It is concluded that the large number of ECG aberrations found in middle-aged and elderly athletes are mainly related to physiological adaptation to training and that training seems to protect against CHD.

Electrocardiographic changes induced by physical exercise in the jumper horse

The authors conducted an electrocardiographic investigation on eight jumpers of Sella Italiana breed to evaluate cardiovascular changes associated with specific competitions. Electrocardiographic recordings were carried out using an electrocardiograph with a deflection of 10 mm/mV and a paper speed of 25 mm/sec. Recordings were conducted under the following experimental conditions: at rest, after warm up, after a jumping trial, and 15 and 30 minutes after the end of the trial. Significant reductions were observed in the duration of the P wave, of the P-Q interval, and of the R-R intervals immediately after the test. Significant elevations were observed immediately after the test in the range of the T and P waves of the heart rate. The observed changes can be attributed mainly to increase of the sympathetic tone connected with increase of heart rate necessary to satisfy the elevation of the cardiac range. These results are useful to plan and monitor specific training programmes.

Clinical significance of abnormal electrocardiographic patterns in trained athletes

BACKGROUND-The prevalence, clinical significance, and determinants of abnormal ECG patterns in trained athletes remain largely unresolved. METHODS AND RESULTS-We compared ECG patterns with cardiac morphology (as assessed by echocardiography) in 1005 consecutive athletes (aged 24+/-6 years; 75% male) who were participating in 38 sporting disciplines. ECG patterns were distinctly abnormal in 145 athletes (14%), mildly abnormal in 257 (26%), and normal or with minor alterations in 603 (60%). Structural cardiovascular abnormalities were identified in only 53 athletes (5%). Larger cardiac dimensions were associated with abnormal ECG patterns: left ventricular end-diastolic cavity dimensions were 56. 0+/-5.6, 55.4+/-5.7, and 53.7+/-5.7 mm (P<0.001) and maximum wall thicknesses were 10.1+/-1.4, 9.8+/-1.3, and 9.3+/-1.4 mm (P<0.001) in distinctly abnormal, mildly abnormal, and normal ECGs, respectively. Abnormal ECGs were also most associated with male sex, younger age (<20 years), and endurance sports (cycling, rowing/canoeing, and cross-country skiing). A subset of athletes (5% of the 1005) showed particularly abnormal or bizarre ECG patterns, but no evidence of structural cardiovascular abnormalities or an increase in cardiac dimensions. CONCLUSIONS-Most athletes (60%) in this large cohort had ECGs that were completely normal or showed only minor alterations. A variety of abnormal ECG patterns occurred in 40%; this was usually indicative of physiological cardiac remodeling. A small but important subgroup of athletes without cardiac morphological changes showed striking ECG abnormalities that suggested cardiovascular disease; however, these changes were likely an innocent consequence of long-term, intense athletic training and, therefore, another component of athlete heart syndrome. Such false-positive ECGs represent a potential limitation to routine ECG testing as part of preparticipation screening.

Electrocardiographic changes in 1000 highly trained junior elite athletes

OBJECTIVES

To evaluate the spectrum of electrocardiographic (ECG) changes in 1000 junior (18 or under) elite athletes.

METHODS

A total of 1000 (73% male) junior elite athletes (mean (SD) age 15.7 (1.4) years (range 14-18); mean (SD) body surface area 1.73 (0.17) m2 (range 1.09-2.25)) and 300 non-athletic controls matched for gender, age, and body surface area had a 12 lead ECG examination.

RESULTS

Athletes had a significantly higher prevalence of sinus bradycardia (80% v 19%; p<0.0001) and sinus arrhythmia (52% v 9%; p<0.0001) than non-athletes. The PR interval, QRS, and QT duration were more prolonged in athletes than non-athletes (153 (20) v 140 (18) milliseconds (p<0.0001), 92 (12) v 89 (7) milliseconds (p<0.0001), and 391 (27) v 379 (29) milliseconds (p = 0.002) respectively). The Sokolow voltage criterion for left ventricular hypertrophy (LVH) and the Romhilt-Estes points score for LVH was more common in athletes (45% v 23% (p<0.0001) and 10% v 0% (p<0.0001) respectively), as were criteria for left and right atrial enlargement (14% v 1.2% and 16% v 2% respectively). None of the athletes with voltage criteria for LVH had left axis deviation, ST segment depression, deep T wave inversion, or pathological Q waves. ST segment elevation was more common in athletes than non-athletes (43% v 24%; p<0.0001). Minor T wave inversion (less than -0.2 mV) in V2 and V3 was present in 4% of athletes and non-athletes. Minor T wave inversion elsewhere was absent in non-athletes and present in 0.4% of athletes.

CONCLUSIONS

ECG changes in junior elite athletes are not dissimilar to those in senior athletes. Isolated Sokolow voltage criterion for LVH is common; however, associated abnormalities that indicate pathological hypertrophy are absent. Minor T wave inversions in leads other than V2 and V3 may be present in athletes and non-athletes less than 16 but should be an indication for further investigation in older athletes.

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.

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.

Prevalence and possible mechanisms of ventricular arrhythmias in athletes

To investigate the prevalence and nature of ventricular arrhythmias in athletes, 40 well trained healthy endurance athletes (20 cyclists and 20 runners) and 40 healthy sedentary subjects as controls were studied. Twenty four-hour continuous ECG monitoring showed a higher, even though not significant prevalence of ventricular ectopy in athletes (70% vs 55%). Complex forms of ventricular ectopy were also more prevalent in the athletes than in the controls (25% vs 5%; p less than 0.05). A prolongation of both measured QT interval and QT corrected for heart rate was observed at the ECG. Echocardiograms showed higher dimensional indices in the athletes, while functional indices were similar in athletes and controls. No correlation was found between any ECG or echocardiographic finding and the grade of ventricular arrhythmia. The comparison between the cyclists and the runners did not show any significant difference in the prevalence of ventricular arrhythmias or in the QT interval duration.

The electrocardiogram and the athlete

Physiological adaptations of the heart to prolonged, intense physical training produce electrocardiographic changes considered abnormal in untrained persons. Increased vagal tone, anatomical changes in the heart, and other less understood mechanisms are thought to cause a spectrum of surface ECG changes characteristic of trained athletes. Arrhythmias frequently seen include sinus bradycardia, sinus pauses, and supraventricular ectopic beats. Conduction abnormalities such as prolonged P-R interval, first degree AV heart block, Wenckebach type I AV heart block, non-sinus escape rhythms, and intraventricular conduction delays of right bundle branch type are also found. Other commonly seen abnormalities include right axis deviation, increased right and left ventricular voltage, ST segment elevation, diphasic and inverted T waves, and prominent U waves. Changes in ECG parameters with exercise include a shortening of the P-R interval with a concomitant increase in the P wave/P-R interval ratio, improved AV conduction with cessation of Wenckebach phenomenon, and normalisation of ST segment and other T wave changes. Thallium scintigraphy and radionuclide angiography have been very useful in ruling out ischaemic heart disease in athletes with rest- and exercise-induced repolarisation abnormalities. Racial differences in QRS voltage and repolarisation changes have been documented. In summary, it is important to consider the type of physical activity, intensity of training, race of athlete, body habitus, and the time the ECG was obtained in relation to training in order to better understand the "normal' spectrum of ECG changes in athletes.

Electrocardiogram of the athlete: an analysis of 289 professional football players

The electrocardiogram (ECG) of athletes reflects physiologic cardiovascular adaptations that occur in well-conditioned individuals. To more clearly define electrocardiographic changes seen in predominantly power-trained athletes, the ECGs of 289 apparently healthy professional football players were analyzed in detail. The players, aged 21 to 35 years, one-third of whom were black, had a mean body surface area of 2.24 m2, a mean heart rate at rest of 56 +/- 9 beats/min (with 77% (223) having a rate of less than 60 beats/min), and a mean P axis of 30 +/- 25 degrees. A wide QRS-T angle (greater than 60 degrees) was present in 14% (41 players) of the group. The mean PR interval was 0.18 +/- 0.02 second (greater than 0.21 in 9% [26 players]). Although two-thirds of the players had a QRS duration of 0.10 second, only 1 had right bundle branch block and none had left bundle branch block. The sum of S in lead V1 plus R in lead V5 averaged 37 +/- 9 mm, with 35% (101 players) demonstrating voltage criteria for left ventricular hypertrophy. The S + R value varied inversely with weight (r = -0.27, p less than 0.002). The maximum T height in any lead had a mean of 8.6 +/- 3 mm, with 22% (64 players) having a T height greater than or equal to 11 mm. U waves were universally present. ST-T changes mimicking ischemia were noted in 39 of 289 players (13%), 22 (58%) of whom were black (p less than 0.001). The maximal J-point elevation in any lead averaged 1.9 +/- 0.9 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Twenty-four-hour continuous electrocardiography during exercise and free activity in 80 apparently healthy runners

To determine the incidence of arrhythmias and conduction disturbances in trained athletes and the level of physical training at which they occur, 24-hour ambulatory electrocardiographic recordings were obtained in 80 healthy runners during both exercise and free activity. Subjects were grouped according to the number of miles per week (mpw) they had regularly run during the previous 3 months: Group I--0 to less than or equal to 5 mpw (less than or equal to 8 km); Group II--greater than 5 to less than or equal to 15 mpw (greater than 8 to less than or equal to 24 km); Group III--greater than 15 to less than or equal to 30 mpw (greater than 24 to less than or equal to 48 km); and Group IV--greater than 30 mpw (greater than 48 km). Ectopic ventricular complexes occurred in 41 of 80 subjects (50%) and ectopic supraventricular complexes occurred in 33 (41%). There were 2 episodes of paired ventricular ectopic activity and a 5-beat run of ventricular tachycardia with exercise. The study revealed no significant differences in the occurrence of arrhythmias or conduction disturbances in the different groups, although the 2 episodes of paired ventricular ectopic activity and 5-beat run of ventricular tachycardia are of concern.

Ambulatory electrocardiographic recording in endurance athletes

Data from ambulatory electrocardiographic recording in 35 highly trained endurance athletes and in 35 non-athletic controls of similar ages are given. The minimal, mean hourly, and maximal heart rates were significantly lower in the athletes. Thirteen athletes (37 . 1%) but only two controls (5 . 7%) had sinus pauses exceeding 2 . 0 seconds. First degree atrioventricular block was observed in 13 athletes (37 . 1%) and five controls (14 . 3%), second degree Wenckebach type block in eight athletes (22 . 9%) and two controls (5 . 7%), and second degree block with Mobitz II-like pattern in three athletes (8 . 6%) and no control. All athletes with Mobitz II-type pattern also had first degree and Wenckebach-type second degree atrioventricular block. The behavior of sinus rate on development of atrioventricular block varied, not only interindividually but also intraindividually, from absence of change to an increase or decrease in most subjects in both study groups. A decrease in sinus rate on appearance of atrioventricular block was found constantly in only two athletes and one control. Atrioventricular dissociation with junctional rhythm occurred in seven athletes (20%) and with ventricular rhythm in one athlete. Neither of these phenomena was seen in the group of controls. The athletes had slightly fewer ventricular extrasystoles than controls, and no athlete had ventricular tachycardia, whereas two controls had ventricular tachycardia.

Noninvasive assessment of T-wave abnormalities on precordial electrocardiograms in middle-aged professional bicyclists

Six middle-aged, active, professional bicyclists with T-wave abnormalities on precordial ECGs were studied noninvasively. Twenty-five aged-matched bicyclists without T-wave abnormalities served as the control subjects. Increased voltage of SV1 + RV5 was demonstrated in all subjects. A 5-year follow-up study revealed that these abnormalities of T-wave inversion became more pronounced with age, except in one case. VCGs showed enlargement of anterior QRS loop and discordant T loop, in all cases. On echocardiography, thickness of both the interventricular septum and the left ventricular posterior wall, and left ventricular mass were significantly increased compared with the control group. 201Tl myocardial scintigraphy at rest and during exercise revealed no regional perfusion defects of the tracer in either case. We conclude that: (1) T-wave abnormalities of precordial ECGs in six middle-aged athletes were progressive in nature; and (2) these electrocardiographic abnormalities seem to be related to left ventricular hypertrophy induced by steady and strenuous training rather than to coronary artery disease.

Non-invasive evaluation of cardiac function in professional cyclists

Cardiac dimensions and left ventricular function were investigated at rest with non-invasive methods in 14 professional road race cyclists and in 11 age-matched sedentary control subjects. The electrocardiographic findings were in agreement with previous studies in endurance athletes and the vectocardiographic data showed anterior displacement of the electrical forces. Echocardiographic dimensions at end-diastole showed higher values in the cyclists for left ventricular internal diameter, left ventricular posterior wall thickness, and interventricular septal thickness. Derived values for left ventricular volume and left ventricular mass were also much larger in the cyclists and there was excellent agreement between total heart volume measured with radiology and total measured by echocardiography. There was a significant correlation between maximal oxygen consumption and end-diastolic left ventricular diameter.

Wenckebach second-degree A-V block in top-ranking athletes: an old problem revisited

The occurrence of Wenckebach second-degree (Mobitz I) A-V block in apparently normal persons still provides a puzzle for the cardiologist, as the benign nature of this event has been recently questioned. This problem becomes more intriguing when Wenckebach A-V block is encountered in asymptomatic top-ranking athletes, because of medico-legal implications. We report 10 cases of highly-trained athletes, including three with mitral valve prolapse (MVP) features, with a spontaneous or induced Wenckebach second-degree A-V block. Previous ECGs of six subjects, dating from a maximum of 6 years to a minimum of 18 months, were available. Deterioration of A-V conduction has never been documented and all six cases have remained asymptomatic for the whole follow-up period. Athletes have been submitted to a protocol study consisting of ECG recording at rest, during, and after vagal and sympathetic reflex maneuvers, drug administration (isoproterenol and atropine), submaximal and maximal exercise. Nine subjects have been considered to have "normal" responses of the A-V node to provocative tests, since conduction disturbances were improved or normalized by reflex sympathetic stimulations and were completely normalized by autonomic drug administration and exercise. One athlete showed "abnormal" responses to tests. In order to give a conclusive prognostic and medico-legal assessment, we advised him to submit to an invasive electrophysiological investigation. Wenckebach second-degree A-V block in athletes may be a more common finding than so far described, especially when a systematic search is made. In our opinion, this event can still be considered a vagally-induced benign feature of athlete's heart, provided that an immediate improvement of A-V conduction is obtained in response to reflex sympathetic maneuvers, and that a complete normalization after sympathomimetic and vagolytic drug administration and physical exercise is observed. The clinical histories of our athletes and the observed complete disappearance of conduction disturbances after detraining, strongly support this opinion. Wenckebach second-degree A-V block in asymptomatic athletes with MVP features probably does not affect the prognosis if similar favorable responses to the aforesaid tests are observed.

T wave abnormalities in top-ranking athletes: effects of isoproterenol, atropine, and physical exercise

Eight cases of top-ranking athletes with "repolarization disorders" are reported. All subjects were asymptomatic and were otherwise suited for excellent cardiovascular performances. Seven athletes did not show any evidence of heart disease. Seven had MVP (mitral valve prolapse). Umprompted variability of ECG tracings was observed in three cases. Both isoproterenol infusions (IS) and maximal physical effort (EX) normalized T wave (abnormalities in 100% of cases, while atropine (AT) was ineffective despite an increase in heart rate greater than that caused by IS. The authors emphasize the usefulness of combined use of the EX and IS tests in ascertaining the clinical significance of T wave changes in healthy athletes. A "neurogenic" mechanism is proposed by the authors for the pathogenesis of these T wave abnormalities. This hypothesis may explain the umprompted variability of ECG tracings and T wave normalization after maximal physical effort and isoproterenol infusion.

Blood Lipid and ECG Responses to Carbohydrate Loading

Carbohydrate loading is so popular that spaghetti is now the premarathon meal. Dr. Blair studied whether this practice has adverse effects on cardiovascular function.

The athlete's heart syndrome: a new perspective

Although earlier electrocardiographic and roentgenographic studies suggested that the heart of trained athletes differed from that of nonathletes, little was known of the cardiac dimensions of the athlete's heart until the advent of echocardiography. Echocardiographic studies have demonstrated that trained athletes may have increased left ventricular mass and that the structural change accounting for this increase is related to the type of physical conditioning. Athletes participating primarily in isotonic exercise have an increase in left ventricular end-diastolic volume with little or no increase in left ventricular wall thickness whereas those athletes participating primarily in isometric exercise have an increase in left ventricular wall thickness associated with normal left ventricular end-diastolic volume. Comparisons between echocardiographically determined cardiac changes in college and world class athletes were made, and the electrocardiographic and chest roentgenographic changes present in the athlete's heart syndrome were reviewed.

A quantitative echocardiographic study of champion childhood swimmers

An echocardiographic evaluation of 77 members of a championship childhood swim team showed dimensional variations from normal in most athletes. Cardiac walls were thicker than the 95th percentile of normal: right ventricular anterior wall exceeded the 95th percentile in 100%, interventricular septum in 83% and left ventricular posterior wall in 91%. The left ventricular and left atrial cavities in diastole had mean values at the 50th percentile of normal but showed considerable scatter. The left ventricular cavity in systole had a mean value less than the 5th percentile of normal and also showed wide scatter. The aortic root and the aortic intercusp dimension exceeded the 95th percentile of normal in most subjects, 74% and 77%, respectively. No correlation existed between the coach's estimate of championship ability and echocardiographic wall or chamber sizes. Children who participate extensively in athletic training programs such as swimming may have echocardiograms which are quantitatively different from those of nonathletic younsters.

Noninvasive evaluation of ventricular hypertrophy in professional athletes

Athletes often exhibit ECG findings which are considered to be abnormal. Therefore, we used noninvasive graphic methods to study 42 active professional male basketball players, ranging in age from 21 to 31 years, without clinically evident heart disease. Of the 42, 11 (25%) met the Romhilt-Estes ECG voltage criteria for left ventricular hypertrophy, and 12 (29%) satisfied VCG criteria for left ventricular enlargement; nine (21%) had left ventricular hypertrophy by both methods. In 33 subjects (79%) the 0.04 sec vector in the horizontal plane was anterior, and 29 of these exhibited one or more standard criteria for right ventricular enlargement; the ECG and VCG were concordant for right ventricular hypertrophy in 16 subjects (38%). Submaximal treadmill exercise tests (Bruce protocol) were normal in eight athletes, while in one subject ventricular premature beats occurred during the test. In 24 of 25 athletes (96%) from whom phonocardiograms were obtained a third heart sound was recorded, while in 14 (56%), a fourth heart sound was present. Of the 14 athletes who had a fourth heart sound, 12 (86%) had either ECG or VCG evidence of ventricular hypertrophy. Only four of 23 athletes had an increased cardiothoracic ratio (greater than .50) on routine chest X-ray. Ten athletes and ten control subjects matched for height, weight and body surface area had echocardiograms satisfactory for analysis. The left ventricular end-diastolic dimension in the athletes averaged 53.7 +/- 1.3 (SE) mm compared with a value of 49.9 +/- 0.7 mm in the control subjects (P less than 0.02), and was increased (greater than or equal to 56 mm) in four. Left ventricular posterior wall thickness averaged 11.1 +/- 0.6 mm, compared with a value of 9.8 +/- 0.5 mm in the control subjects (P less than 0.05), and was increased (greater than or equal to 11 mm) in six athletes. The right ventricular end-diastolic dimension averaged 20.8 +/- 1.1 mm compared with a value of 12.9 +/- 2.2 mm in the controls (P less than 0.004), and was increased (greater than or equal to 23 mm) in four athletes. No athlete or control subject exhibited paradoxical septal motion. In the athletes, ejection fraction (cube method) averaged 79 +/- 2.0% and mean Vcf averaged 1.13 +/- 0.04 circ/sec; these values did not differ from those of the control subjects. Thus, both right and left ventricular enlargement ("physiological hypertrophy") are often present in the well-trained athlete, but left ventricular performance remains normal in the basal state in such individuals. We condlude that these individuals represent a selected subgroup of subjects who are variants of normal.

The electrocardiogram of athletes. Comparison with untrained subjects

The resting electrocardiograms of 30 cyclists currently involved in competitive sport were compared with those of an equal number of healthy controls matched for age, height, and weight. The cyclists had significantly lower heart rates, longer PQ,QRS, and QTc intervals, higher T waves in lead II, left axis deviation of the T wave, higher R waves in the right and deeper S waves in the left praecordial leads, and deeper S waves in the right and higher R waves in the left praecordial leads.The possible significance of these findings should be assessed by prolonged prospective studies in athletes and untrained control subjects.

Six cases of congenital complete heart block followed for 34-40 years

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