CARDIOLOGICAL OBSERVATIONS AT THE SIXTH BRITISH EMPIRE AND COMMONWEALTH GAMES

Symptomatic bradyarrhythmias in the athlete-Underlying mechanisms and treatments

Bradyarrhythmias including sinus bradycardia and atrioventricular (AV) block are frequently encountered in endurance athletes especially at night. While these are well tolerated by the young athlete, there is evidence that generally from the fifth decade of life onward, such arrhythmias can degenerate into pathological symptomatic bradycardia requiring pacemaker therapy. For many years, athletic bradycardia and AV block have been attributed to high vagal tone, but work from our group has questioned this widely held assumption and demonstrated a role for intrinsic electrophysiological remodeling of the sinus node and the AV node. In this article, we argue that bradyarrhythmias in the veteran athlete arise from the cumulative effects of exercise training, the circadian rhythm and aging on the electrical activity of the nodes. We consider contemporary strategies for the treatment of symptomatic bradyarrhythmias in athletes and highlight potential therapies resulting from our evolving mechanistic understanding of this phenomenon.

Morbidities in the ultra-athlete and marathoner

The cardiovascular benefits of habitual exercise are well documented. In the current era, more of the population is exceeding the recommendations for physical activity as the popularity of endurance events increases. Recent data have proposed a U-shaped relationship between exercise intensity and cardiovascular outcomes. Regular participation in endurance activities has been shown to result in structural and functional changes in the heart. This re-modelling may be the substrate for cardiac dysfunction or arrhythmias. The risk of sudden cardiac death may also be elevated; however, in most cases of sudden cardiac death, the cause can be linked to an underlying cardiac pathology where exercise acted as the trigger for a lethal arrhythmia. This article serves to review whether excessive exercise may result in harm in some athletes.

Predicting the rate of oxygen consumption from heart rate in barnacle geese Branta leucopsis: effects of captivity and annual changes in body condition

Quantifying a relationship between heart rate (f(H)) and rate of oxygen consumption (V(O(2))) allows the estimation of V(O(2)) from f(H) recordings in free-ranging birds. It has been proposed that this relationship may vary throughout an animal's annual cycle, due to changes in physiological status. Barnacle geese, Branta leucopsis, provide an ideal model to test this hypothesis, as they exhibit significant intra-annual variability in body mass, body composition and abdominal temperature, even in captivity. Heart rate data loggers were implanted in 14 captive barnacle geese, and at six points in the year the relationship between f(H) and V(O(2)) was determined. The f(H)/V(O(2)) relationship was also determined in seven moulting wild barnacle geese to examine whether relationships from captive animals might be applicable to wild animals. In captive barnacle geese, the f(H)/V(O(2)) relationship was significantly different only between two out of the six periods when the relationship was determined (late September-early October and November). Accounting for changes in physiological parameters such as body mass, body composition and abdominal temperature did not eliminate this difference. The relationship between f(H) and V(O(2)) obtained from wild geese was significantly different from all of the relationships derived from the captive geese, suggesting that it is not possible to apply calibrations from captive birds to wild geese. However, the similarity of the f(H) and V(O(2)) relationship derived during moult in the captive geese to those during the remainder of the annual cycle implies it is not unreasonable to assume that the relationship between f(H)/V(O(2)) during moult in the wild geese is indicative of the relationship throughout the remainder of the annual cycle.

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.

Cardiovascular evaluation of the athlete. Issues regarding performance, screening and sudden cardiac death

Recent studies have reported ECG anomalies and a high prevalence of exercise-related arrhythmias among well trained, apparently healthy endurance athletes with superior levels of cardiorespiratory fitness. The occurrence of sudden and premature cardiac deaths in amateur and professional athletes, who appear to embody all of the virtues of health and fitness, ahs raised our consciousness regarding the underlying atherosclerotic or nonatherosclerotic causes, and the need for, and extent of, preparticipation screening in competitive athletes. It appears that strenuous physical activity may trigger acute cardiovascular events in some athletes. Coronary artery disease is the most frequent autopsy finding in those over the age of 35 years who die suddenly. In contrast, structural cardiovascular abnormalities, including hypertrophic cardiomyopathy and malformations of the coronary arteries, are the major cause of sudden death in younger athletes. This article reviews these issues, with specific reference to the assessment of cardiorespiratory fitness, legal and prohibited performance-altering medications, the pathophysiological basis of exertion-related untoward events, the athlete at risk, limitations of conventional screening programmes and contemporary recommendations to identify latent cardiovascular disease in athletic populations.

Electrocardiographic findings in male veteran endurance athletes

Twenty male veteran endurance runners and 20 controls underwent resting, exercise, and ambulatory electrocardiography. Four athletes and three controls satisfied voltage criteria for left ventricular hypertrophy. The PR interval was longer in the athletes and they had longer mean (SD) treadmill exercise times (19 (4) v 16 (2) min) than the controls. Four athletes but no controls had greater than 2 mm downsloping ST segment depression during exercise. During 48 hour ambulatory electrocardiography the athletes had a consistently lower heart rate but maintained a circadian variation. Profound bradycardia (less than 35 beats/min) occurred in eight athletes but only one control. Eight athletes and two controls had asystolic pauses ranging from 1.8 to 15 seconds. Six athletes had first degree heart block, four had Mobitz II second degree block, and three had complete heart block. Most conduction abnormalities occurred at night and resolved during exercise. Ventricular ectopic activity was not significantly different between the groups. Thus heart block patterns and profound bradycardia are more frequent in older athletes than their youthful counterparts.

Tachyarrhythmias in young athletes

Nineteen young athletes with documented symptomatic tachyarrhythmia were systematically evaluated. There were 15 men and 4 women, aged 14 to 32 years (mean 22 +/- 6). Documented tachyarrhythmias were paroxysmal atrial fibrillation in five patients, paroxysmal supraventricular tachycardia in five, paroxysmal ventricular tachycardia in eight (sustained in five, nonsustained in three) and ventricular fibrillation in one patient. Abnormal substrates were demonstrated in 15 (79%) of the 19 athletes: 5 had an anomalous atrioventricular (AV) pathway and 10 had heart disease (mitral valve prolapse in 9 patients and dilated cardiomyopathy in 1 patient). In 13 (68%) of the 19 athletes, all spontaneous attacks of tachyarrhythmia had started during strenuous exercise. Tachyarrhythmia that closely resembled clinical arrhythmia was induced by programmed cardiac stimulation in 13 athletes (68%) and was reproducibly provoked by treadmill exercise in 8 athletes (42%). In four of seven athletes with ventricular tachycardia, tachycardia closely resembling clinical arrhythmia was provoked by infusion of isoproterenol. In summary: young athletes can have any of several tachyarrhythmias; abnormal substrates can be demonstrated in many athletes with symptomatic tachyarrhythmia; and tachyarrhythmias in young athletes frequently occur during exercise.

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.

Abnormal cardiac enzyme responses after strenuous exercise: alternative diagnostic aids

Serial estimations of activities of creatine kinase and its MB isoenzyme, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase and of concentrations of alpha(1)-acid glycoprotein were performed in 15 healthy well-trained male marathon runners. Estimations were made initially within three days before a race and then one, 24, and 96 hours after the race. Technetium-99m pyrophosphate myocardial scintigraphy was carried out at the initial prerace assessment and repeated 48 to 96 hours after the race. None of the subjects developed cardiac symptoms during or after the race.Activities of creatine kinase and creatine kinase MB became maximal 24 hours after the race. One and 96 hours after the race two and five subjects, respectively, showed amounts of creatine kinase MB totalling 5% or more of total creatine kinase. Lactate dehydrogenase activity peaked at one hour after the race, and activities of aspartate and alanine aminotransferases peaked at 24 and 96 hours after the race, respectively. Activities of all these enzymes showed a significant increase from prerace values during the rest of the study. Electrocardiographic features noted were similar to those reported elsewhere in athletes under similar conditions. They included first-degree heart block, incomplete right bundle-branch block, left ventricular hypertrophy, pseudoischaemic T-wave changes, and early repolarisation of variant ST-segment elevations in precordial leads. Technetium-99m pyrophosphate myocardial scintigraphy did not show evidence of myocardial damage before or after the race. Alpha(1)-acid glycoprotein concentrations were normal throughout.These data suggest that reliance on standard enzyme estimations and electrocardiographic criteria may yield false-positive indicators of myocardial injury during prolonged strenuous exercise. Technetium-99m pyrophosphate scintigraphy and alpha(1)-acid glycoprotein measurements offer additional information and may usefully be employed in evaluating circulatory collapse associated with such exercise.

Twenty-four hour continuous ECG recordings in long-distance runners

Twenty-four hour ambulatory ECG recordings were performed on 20 male long-distance runners, aged 19 to 28 years, during normal activities other than running. Average, maximum, and minimum waking heart rates, respectively, ranged from 58 to 108 (mean +/- SD, 73 +/- 15), 90 to 164 (120 +/- 19), and 34 to 53 (43 +/- 5) beats/min. Longest waking sinus pauses ranged from 1.35 to 2.55 (1.7 +/- 0.3) seconds. Average, maximum, and minimum sleeping heart rates, respectively, ranged from 38 to 58 (47 +/- 6), 69 to 114 (83 +/- 14), and 31 to 43 (36 +/- 3) beats/min. Longest sleeping sinus pauses ranged from 1.60 to 2.81 (2.0 +/- 0.3) seconds. All 20 runners had atrial premature beats, but only one (5 percent) had more than 100/24 hours. Fourteen runners (70 percent) had ventricular premature beats, but only two (10 percent) had more than 50/24 hours, and none had ventricular couplets or ventricular tachycardia. Eight runners (40 percent) had one or more episodes of type 1 second-degree atrioventricular (A-V) block. Compared with untrained males of similar age, the runners had slower heart rates (by approximately 10 beats/min), longer sinus pauses, and a higher prevalence of A-V block. Runners and untrained males did not differ with respect to prevalence of ventricular premature beats, R on T phenomenon, ventricular couplets, or 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.

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.

The noninvasive cardiac evaluation of long-distance runners

Twelve long-distance runners were evaluated by physical examination, electrocardiogram, vectorcardiogram, chest x-ray film, and echocardiogram; and the results were compared to the findings in 12 normal control subjects. The athletes showed a significantly higher frequency of gallop rhythms with a third or fourth heart sound. Electrocardiographic and vectorcardiographic abnormalities consisting of right or left ventricular hypertrophy, bradycardia, and alterations in the ST-T wave were also present in the runners. Echocardiographic examination of the athletes revealed increased wall thickness, left ventricular muscular mass, diastolic volume, and ventricular function. It is essential that the physician who examines athletes be aware of the spectrum of apparently abnormal findings in this group. Echocardiographic studies should prove useful in establishing the presence or absence of some forms of cardiac disease in athletes.

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.

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.

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

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