Abnormal cardiac enzyme responses after strenuous exercise: alternative diagnostic aids

Coronary and skeletal muscle enzyme changes during a 14 km run

Increasing coronary enzyme values have previously been demonstrated after physical exercise. In the present study serum values of aspartate aminotransferase (ASAT), lactate dehydrogenase (LDH), LDH isoenzymes, creatinine kinase (CK), and the myocardial-bound fraction of this enzyme (CK-MB) were measured in a random sample of healthy non-smoking, physically fit men before and immediately after a competitional 14 km run. All enzyme values increased during the run, ASAT by 7%, LDH by 25%, CK by 38%, and CK-MB by 53%. Measurement of LDH isoenzymes showed special increments of the non-cardiac fractions. However, absolute increments of the cardiac fractions of the LDH isoenzymes together with other serum enzyme elevations do not exclude a cardiac source of enzyme release during and following physical exercise.

Evaluation of myocardial alterations using the enzymatic profile of elderly long-distance runners

Elderly population often is encouraged to practice sports in preventing cardiovascular diseases. However, evidences exist that intense physical efforts are related with a higher risk for acute myocardial infarction and sudden death. Biological markers for myocardial injury was analyzed in a group of 15 elderly athletes without a history of coronary artery disease, who participated in the 77th International Sao Silvestre race (15,000 m) in Sao Paulo City. A statistical difference was observed between total CPK activity levels before the run, immediately after the run, and some time later. Similar results were observed in the concentration of CK-MB mass. The cardiac troponin I (TnI-c) levels remained unchanged and within normal limits during the same time periods. The results of the present study showed no evidence of myocardial injury in elderly subjects without a history of coronary artery disease after participating in long-distance runs, as confirmed by the analysis of TnI-c levels. The increase in total CPK activity levels and the concentration of CK-MB mass do not represent myocardial injury in these subjects.

Left ventricular systolic function and diastolic filling after intermittent high intensity team sports

BACKGROUND

Prolonged steady state exercise can lead to a decrease in left ventricular (LV) function as well as promote the release of cardiac troponin T (cTnT). There is limited information on the effect of intermittent high intensity exercise of moderate duration.

OBJECTIVES

To determine the effect of intermittent high intensity exercise of moderate duration on LV function.

METHODS

Nineteen male rugby and football players (mean (SD) age 21 (2) years) volunteered. Assessments, before, immediately after, and 24 hours after competitive games, included body mass, heart rate (HR), and systolic blood pressure (sBP) as well as echocardiography to assess stroke volume (SV), ejection fraction (EF), systolic blood pressure/end systolic volume ratio (sBP/ESV), and global diastolic filling (E:A) as well as to indirectly quantify preload (LV internal dimension at end diastole (LVIDd)). Serum cTnT was analysed using a 3rd generation assay. Changes in LV function were analysed by repeated measures analysis of variance. cTnT data are presented descriptively.

RESULTS

SV (91 (26) v 91 (36) v 90 (35) ml before, after, and 24 hours after the game respectively), EF (71 (8) v 70 (9) v 71 (7)%), and sBP/ESV (4.2 (1.8) v 3.8 (1.9) v 4.1 (1.6) mm Hg/ml) were not significantly altered (p>0.05). Interestingly, whereas LVIDd was maintained after the game (50 (5) v 50 (6) mm), sBP was transiently but significantly reduced (131 (3) v 122 (3) mm Hg; p<0.05). E:A was moderately (p<0.05) reduced after the game (2.0 (0.4) v 1.5 (0.4)) but returned to baseline within 24 hours. No blood sample contained detectable levels of cTnT.

CONCLUSIONS

In this cohort, LV systolic function was not significantly altered after intermittent activity. A transient depression in global diastolic filling was partially attributable to a raised HR and could not be explained by myocyte disruption as represented by cTnT release.

Impact of marathon running on cardiac structure and function in recreational runners

The present study examined the relationship between LV (left ventricular) function, markers of cardiac-specific damage and markers of oxidative stress in recreational runners following a marathon. Runners (n=52; 43 male and nine female; age, 35±10 years; height, 1.74±0.08 m; body mass, 75.9±8.9 kg) were assessed pre- and immediately post-marathon. LV function was assessed using standard M-mode two-dimensional Doppler echocardiography and TDI (tissue-Doppler imaging) echocardiography. Serum was analysed for cTnT (cardiac troponin-T), TEAC (Trolox equivalent antioxidant capacity; a measure of total antioxidant capacity), MDA (malondealdehyde) and 4-HNE (4-hydroxynonenal). A strong relationship was observed between standard and TDI echocardiography for all functional measures. Diastolic function was altered post-marathon characterized by a reduction in E (peak early diastolic filling: 0.79±0.11 compared with 0.64±0.16 cm/s; P<0.001), an increase in A (peak late diastolic filling: 0.48±0.11 compared with 0.60±0.12 cm/s; P<0.001) and a resultant decrease in E/A (ratio of E to A; 1.71±0.48 compared with 1.10±0.31; P<0.001). Ejection fraction remained unchanged post-marathon. Thirty-two runners presented with cTnT values above the lower limit of detection for the assay (0.01 μg/l), and 20 runners presented post-marathon with cTnT values above the acute myocardial infarction cut-off value (0.05 μg/l). No significant correlations were observed between cTnT and any functional measurements. MDA (2.90±1.58 compared with 3.59±1.47 μmol/l) and TEAC (1.80±0.12 compared with 1.89±0.21 mmol/l) were significantly increased post-marathon, but were unrelated to changes in function or cTnT. In conclusion, the present study demonstrated a reduction in diastolic function and widespread evidence of minimal cardiac damage following a marathon in recreational runners. The mechanism(s) underpinning the altered function and appearance of cTnT appear unrelated to reactive oxygen species.

Postexercise Left Ventricular Function and cTnT in Recreational Marathon Runners

PURPOSE

To assess the impact of prolonged exercise on left ventricular (LV) function and the appearance of cardiac troponin T (cTnT) in older and recreational athletes.

METHODS

Heart rate (HR), blood pressures, and cTnT were recorded in 35 subjects (age range 22-57 yr, finishing time 157-341 min) pre- and postrace. Echocardiograms (N = 26) assessed stroke volume (SV), ejection fraction (EF), sBP/LV end-systolic volume (sBP/ESV), diastolic filling (E:A ratio) as well as preload (LV internal dimension at end-diastole [LVIDd]) and afterload (LV wall stress). HR and core temperature were recorded in-event. Prepost changes in LV function were analyzed by repeated measures t-test. Delta scores for LV function and cTnT data were correlated with each other, age, finishing time, alterations in loading, and in-event data.

RESULTS

SV was significantly decreased postrace (109 +/- 31 vs 85 +/- 25 mL, P < 0.05) likely due to a significant decrease in LVIDd (5.3 +/- 0.4 vs 4.9 +/- 0.5 cm, P < 0.05; r = 0.80, P < 0.05). LV wall stress was unchanged postrace (90 +/- 25 vs 89 +/- 27 g x cm(-2), P > 0.05). EF (70 +/- 12 vs.70 +/- 10%, P > 0.05) and sBP/ESV (3.7 +/- 2.9 vs 4.0 +/- 2.0, P > 0.05) did not change prepost race and were not related to age or finishing time (P > 0.05). E:A ratio was significantly reduced postrace (1.73 +/- 0.38 vs 1.41 +/- 0.25, P < 0.05) and could not be explained by an increased HR (56 +/- 9 vs 84 +/- 10, P < 0.05; r = 0.08, P > 0.05), a reduced LVIDd (r = 0.11, P > 0.05), age, finishing time, or in-event data. Postrace 26/33 subjects presented cTnT values in the range 0.024-0.080 microg x L(-1) that were not related to changes in LV function, loading, age, finishing time, or in-event data.

CONCLUSION

No evidence of load-independent depression in LV systolic function was reported. Changes in cTnT and E:A were not related, and their etiology is uncertain.

Does the human heart fatigue subsequent to prolonged exercise?

A reduction in left ventricular systolic and diastolic function subsequent to prolonged exercise in healthy humans, often called exercise-induced cardiac fatigue (EICF), has recently been reported in the literature. However, our current understanding of the exact nature and magnitude of EICF is limited. To date, there is no consensus as to the clinical relevance of such findings and whether such alterations in function are likely to impact upon performance. Much of the existing literature has employed field-based competitions. Whilst ecologically valid, this approach has made it difficult to control many factors such as the duration and intensity of effort, fitness and training status of subjects and environmental conditions. The impact of such variables on EICF has not been fully evaluated and is worthy of further research. To date, most EICF studies have been descriptive, with limited success in elucidating mechanisms. To this end, the assessment of humoral markers of cardiac myocyte or membrane disruption has produced contradictory findings partially due to controversy over the validity of specific assays. It is, therefore, important that future research utilises reliable and valid biochemical techniques to address these aetiological factors as well as develop work on other potential contributors to EICF such as elevated free fatty acid concentrations, free radicals and beta-adrenoceptor down-regulation. In summary, whilst some descriptive evidence of EICF is available, there are large gaps in our knowledge of what specific factors related to exercise might facilitate functional changes. These topics present interesting but complex challenges to future research in this field.

[Biological markers of myocardial necrosis]

New biological markers of myocardial injury have improved the management of patients with acute coronary syndromes. Among these markers, the most relevant are the cardiac troponins (troponin I and troponin T) because of their cardiospecificity, and myoglobin because of its combination of diagnostic sensitivity and usefulness for an early diagnosis. The serial analysis and combined use of both markers fulfill all diagnostic and prognostic requirements, and are helpful in indicating therapeutic strategies for acute coronary syndromes. However, these markers also have limitations, and their concentrations should always be interpreted in the light of the patient's clinical status.

Human alpha-1-glycoprotein and its interactions with drugs

For about half a century, the binding of drugs to plasma albumin, the "silent receptor," has been recognized as one of the major determinants of drug action, distribution, and disposition. In the last decade, the binding of drugs, especially but not exclusively basic entities, to another plasma protein, alpha 1-acid glycoprotein (AAG), has increasingly become important in this regard. The present review points out that hundreds of drugs with diverse structures bind to this glycoprotein. Although plasma concentration of AAG is much lower than that of albumin, AAG can become the major drug binding macromolecule in plasma with significant clinical implications. Also, briefly reviewed are the physiological, pathological, and genetic factors that influence binding, the role of AAG in drug-drug interactions, especially the displacement of drugs and endogenous substances from AAG binding sites, and pharmacokinetic and clinical consequences of such interactions. It can be predicted that in the future, rapid automatic methods to measure binding to albumin and/or AAG will routinely be used in drug development and in clinical practice to predict and/or guide therapy.

Cardiac fatigue following prolonged endurance exercise of differing distances

PURPOSE

Recent echocardiographic studies have reported cardiac dysfunction following ultra-endurance exercise in trained individuals. The duration of exercise required to elicit cardiac dysfunction and the mechanisms underlying this phenomenon have not been fully elucidated. The aim of the present study was to examine the presence of cardiac dysfunction following a half-Ironman and Ironman triathlon in trained individuals.

METHODS

14 male triathletes (age: 32 +/- 5 yr; height: 180 +/- 8 cm; body mass: 75 +/- 9 kg) completed a half-Ironman triathlon. Following a 4-wk period, 10 of the original 14 triathletes completed an Ironman triathlon. All triathletes were assessed using ECG, echocardiography, and blood analysis pre-, immediately post-, and 48 h postrace for both distances.

RESULTS

Echocardiographic results indicated diastolic and systolic left ventricular dysfunction, for both race distances, which were associated with altered relaxation characteristics and a reduced inotropic contractility, respectively. Following 48-h recovery, all echocardiographic measures were similar to resting values. Creatine kinase MB (CKMB) was significantly elevated immediately postrace for both distances; however, it accounted for less than 5% of the total CK value and in the presence of an elevated total CK and CKMM implied that the elevated CKMB was noncardiac in origin. Troponin-T, however, was significantly elevated immediately postrace for both distances and returned to normal following 48-h recovery indicating myocardial damage.

CONCLUSIONS

Ironman and half-Ironman competition resulted in reversible abnormalities in resting left ventricular diastolic and systolic function. Results suggest that myocardial damage may be, in part, responsible for cardiac dysfunction, although the mechanisms responsible for this cardiac damage remain to be fully elucidated.

Short-term effects of marathon running: no evidence of cardiac dysfunction

PURPOSE

The purpose of this study was to analyze the short-term effects of a marathon race (Madrid Marathon) on both markers of cardiac damage and echocardiographic parameters in a group of 22 runners (17 male and 5 female; 34 +/- 5 yr; VO2max: 55.7 +/- 9.1 mL x kg(-1) x min(-1) with a wide range of fitness levels.

METHODS

Venous blood samples were collected from each subject 48 h before the race, at race finish, and 6, 24, and 48 h postexercise for the determination of myoglobin, total creatine kinase catalytic activity (total CK), mass concentration of creatine kinase isoenzyme MB (CK-MB mass), and cardiac isoforms of troponin T and I (TnT-c and TnI-c, respectively). In addition, echocardiographic parameters (M-mode two-dimensional and Doppler analysis) indicative of both left ventricular (LV) systolic and diastolic function were obtained three times from each runner: 2-5 d before the race, at race finish, and 24-36 h after exercise.

RESULTS

Except in one subject, levels of TnT-c and TnI-c were within normal limits (<0.1 ng x mL(-1)) in all the samples collected before or after the race. Overall LV systolic function was not altered by marathon running. Finally, LV diastolic function was transiently altered after the race since the ratio between peak early and late transmitral filling velocities (E/A) was significantly reduced at race finish (P < 0.01) and returned to resting levels after 24-36 h.

CONCLUSIONS

Our findings suggest that marathon running does not adversely affect the hearts of healthy individuals independently from their training status.

The diagnosis of acute myocardial infarction

Changes in the economic and therapeutic environment have altered the time frame in which an accurate diagnosis of acute myocardial infarction (AMI) must be made. The advent of effective reperfusion therapies and the increasing emphasis on reducing cost produce an environment in which rapid diagnosis can reduce morbidity and mortality while simultaneously reducing overall cost by avoiding unnecessary hospitalization and intervention. The first element of a diagnostic strategy remains a brief, directed history and physical examination. The orientation of this phase is to identify important causes of symptoms other than AMI, while rapidly leading to more definitive evaluation for myocardial ischemia when another diagnosis is not found. The ECG provides the most rapid definitive diagnosis, but the diagnosis remains equivocal in many patients with nondiagnostic ECGs. In this group, the use of cardiac enzyme measurements early in the course holds promise in directing intensive care at high-risk patients while avoiding unnecessary intervention in low-risk patients. A protocolized approach to patient evaluation should become a part of standard practice patterns in every hospital.

Acute metabolic effects of exercise in bodybuilders using anabolic steroids

Four male bodybuilders who had started taking anabolic steroids were monitored during exercise. Most metabolic indicators were similar to bodybuilders not taking steroids; i.e. metabolic acidosis with little change in glucose. However, there is a marked elevation of creatine kinase.

Comparison of serum cardiac specific troponin-I with creatine kinase, creatine kinase-MB isoenzyme, tropomyosin, myoglobin and C-reactive protein release in marathon runners: cardiac or skeletal muscle trauma?

Problems arise in distinguishing skeletal from cardiac muscle trauma on the basis of serum enzyme tests following severe muscle exercise. The contributions of cardiac and skeletal sources have been assessed in eleven marathon runners by measuring pre- and post-race serum levels of cardiac-specific myofibrillar troponin-I together with total creatine kinase, creatine kinase-MB isoenzyme, myoglobin, myofibrillar tropomyosin and C-reactive protein. Total creatine kinase, creatine kinase-MB isoenzyme, tropomyosin and myoglobin were significantly elevated above pre-race levels in all runners between 1 h and 128 h post-race. Neither mean cardiac troponin-I nor C-reactive protein was elevated post-race. Nine out of sixty-three samples fulfilled conventional positive criteria for cardiac muscle damage on the basis of combined creatine kinase and creatine kinase-MB isoenzyme levels. Six runners had one or more positive samples. No samples had levels above twice the upper normal limit for either cardiac troponin-I or C-reactive protein. Correlation analysis of levels in each sample indicated skeletal and not cardiac muscle as the source of raised serum protein.

Effect of exercise on serum enzyme activities in humans

Increased serum enzyme activity after exercise was first reported in 1958; subsequent studies have established that many factors determine the degree to which the serum activities of a variety of enzymes increase during and after exercise. The serum activities of those enzymes found especially in muscle, particularly creatine kinase, increase in proportion to the intensity and duration of the preceding exercise, peaking 24 hours after exercise; the effect of duration is dominant, so that the highest postexercise serum enzyme activities are found after very prolonged competitive exercise such as ultradistance marathon running or triathlon events. Weight-bearing exercises which include eccentric muscular contractions such as bench stepping and downhill running induce the greatest increases in serum enzyme activities; serum enzyme activities increase very little even after prolonged participation in those non-weight-bearing activities such as swimming and cycling which do not include eccentric muscular contractions. Prolonged (greater than 2 hours) daily training or competition in weight-bearing activities produces chronically elevated serum enzyme activities. Serum enzyme activities increase more with exercise in males, Blacks and the untrained than they do in females, Whites and the trained, respectively; age does not appear to influence the degree to which serum enzyme activities increase with exercise. There is a remarkable individual variability in the degree to which serum enzyme activities increase with exercise; a 50-fold difference in post-race serum creatine kinase activities has been found in healthy and equally trained athletes completing the same 90km ultramarathon footrace. The biochemical explanation for this degree of individual variability is not currently understood; possibly persons who show abnormally large increases in serum enzyme activities with exercise may have as yet unrecognised subclinical myopathies. No circadian rhythms have been identified for serum enzyme activities; activities rise during the day because of increased physical activity. The rise in serum enzyme activities is greater after exercise at altitude or in the heat than after equivalent exercise at sea level or in the cold. The most likely explanation for the increased serum enzyme activities that follow prolonged weight-bearing activities that also cause marked muscle soreness, is myofibrillar damage in particular sarcomeric Z-disk disruption.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiac-specific troponin-I radioimmunoassay in the diagnosis of acute myocardial infarction

The cardiac isotype of the myofibrillar contractile protein, troponin-I, is located specifically in the mammalian heart. A sensitive radioimmunoassay has been developed to detect human and nonhuman primate cardiac troponin-I in serum down to 10 ng/ml. Immunochemical cross reactivity with skeletal troponin-I was only 2% and was species nonspecific. Normal patient levels of cardiac troponin-I are about 10 ng/ml. In patients with acute myocardial infarction (n = 32), serum cardiac troponin-I was elevated within 4 to 6 hours, reached a mean peak level of 112 ng/ml (range 20 to 550 ng/ml) at 18 hours, and remained above normal for up to 6 to 8 days following infarction. Peak cardiac troponin-I correlated with peak creatine kinase (CK) MB isoenzyme (r = 0.75). In subjects (n = 34) with skeletal muscle damage (total CK = 338 to 5384 IU/L), cardiac troponin-I levels were not elevated above normal, although CK-MB isoenzyme was elevated in some patients. Cardiac troponin-I levels were normal or slightly elevated in patients with ischemic heart disease and were normal in patients with chest pain of noncardiac origin. Immunoassay of cardiac troponin-I could be a valuable diagnostic aid in the cardiac-specific detection of cell necrosis.

Use of topical minoxidil in the treatment of male pattern baldness

This 12-month, double-blind, randomized study evaluated the safety and efficacy of topical minoxidil in the treatment of male pattern baldness. Three formulations were compared: 2% minoxidil solution, 3% minoxidil solution, and placebo. After 4 months all placebo patients crossed over to treatment with the 3% solution. Of the 96 patients randomized into the study, 79 were evaluable at month 12; 25 of these were in the 2% minoxidil group, 24 were in the 3% minoxidil group, and 29 were in the placebo-to-3% solution switchover group. At monthly intervals a hair count was obtained within a 1-inch diameter area on the scalp vertex. In addition, a gross visual estimate of the degree of new hair growth over the entire balding area was made independently by the investigator and the patient. At the end of 4 months there was significant regrowth of nonvellus (terminal and indeterminate) hairs in the patients using the 2% and 3% solutions (p = 0.0001). The mean nonvellus hair count at month 4 was 162.8 in the 2% minoxidil group, 155.4 in the 3% minoxidil group, and 107.1 in the placebo group. The mean increase in the 2% and 3% treatment groups was 58.2 and 48.8, respectively, whereas the mean increase in the placebo group was 4.0. Total hair counts at month 4 demonstrated significantly more growth of hair in the 2% minoxidil group than in the placebo group (p = 0.013), with no significant difference between the 3% minoxidil group and the other two treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of increased serum creatine kinase as an indicator of irreversible myocardial damage in dogs

To evaluate the relationship between creatine kinase (CK) elevation and irreversible myocardial damage, a coronary artery branch was occluded for periods of 5 to 40 min in ten dogs. In five other dogs the coronary vessel was occluded for 480 min, and five dogs underwent the same operative procedure but without occlusion of the artery. The serum CK was monitored for 8 hours postoperatively in all dogs. Elevation of the CK levels occurred in all groups, but the area under the time-enzyme activity curve showed no statistically significant difference between the group with 480-min occlusion, in which transmural myocardial infarction occurred in all dogs, and the group with temporary occlusion, in which no infarction could be histologically or histochemically demonstrated. Contrastingly, a statistically significant difference was found between the group with temporary occlusion and the control group with no occlusion. The results suggest that CK elevation is of no value as an indicator of irreversible myocardial damage during heart surgery that involves temporary myocardial ischaemia.

Echocardiographic assessment of left ventricular performance before and after marathon running

Echocardiography was used to indirectly assess the effects of marathon running on myocardial performance. Thirteen marathon runners (mean +/- SEM:30 +/- 1.6 years) were submitted to a resting echocardiographic examination before racing and during early recovery from marathon racing. Indices of left ventricular performance were computed from M-mode recordings of left ventricular dimensions and aortic valve motions. Comparison of basal and post-marathon indices of left ventricular performance showed no significant differences in either pre-ejection period (PEP), left ventricular ejection index (LVEI), fractional shortening (% delta D), ejection fraction (EF), or mean rate of circumferential fiber shortening (mVcf). Cardiac output (Qc) computed from left ventricular end-diastolic (LVEDV) and end-systolic volumes (LVESV) were significantly higher following marathon running (4.9 +/- 0.4 to 6.7 +/- 0.7 L/min) because of a marked increase in resting heart rate (HR) (58 +/- 3 to 76 +/- 3 bpm). A significant decrease in systolic blood pressure (118 +/- 4 to 108 +/- 3 mm Hg), associated with a slight reduction in calculated total peripheral resistance was also observed after the race. These circulatory adjustments probably reflect thermoregulatory activity that allows a greater blood flow to the skin for heat dissipation, as well as persistence of reactive muscle hyperemia. Echocardiographic evidence suggests that marathon running does not lead to marked impairments in left ventricular performance. However, the absence of change in the end-systolic volume, despite a marked reduction in cardiac afterload, may suggest a slight alteration in contractility that could not be detected with the use of echocardiography.

Normal results of post-race thallium-201 myocardial perfusion imaging in marathon runners with elevated serum MB creatine kinase levels

Elevated cardiac enzyme values in asymptomatic marathon runners after competition can arise from skeletal muscle through exertional rhabdomyolysis, silent injury to the myocardium, or a combined tissue source. Peak post-race levels of the MB isoenzyme of creatine kinase are similar to values in patients with acute myocardial infarction. Previously reported normal results of infarct-avid myocardial scintigraphy with technetium 99m pyrophosphate in runners after competition suggest a non-cardiac source but cannot exclude silent injury to the myocardium. Therefore, thallium 201 myocardial perfusion imaging was performed in runners immediately after competition together with determination of sequential cardiac enzyme levels. Among 15 runners tested, the average peak in serum MB creatine kinase 24 hours after the race was 128 IU/liter with a cumulative MB creatine kinase release of 117 IU/liter; these values are comparable to those in patients with acute transmural myocardial infarction. Thallium 201 myocardial scintigraphic results were normal in five runners randomly selected from those who volunteered for determination of sequential blood levels. Serum lactate dehydrogenase isoenzymes showed only a peripheral pattern of release. It is concluded that elevations of serum MB creatine kinase in marathon runners arise from a skeletal muscle source and that thallium 201 myocardial scintigraphy is useful to assess runners for myocardial injury when clinical questions arise.

Serum lactate dehydrogenase and creatine kinase during marathon training

Serum total creatine kinase (CK) and the lactate dehydrogenase (LDH) isoenzymes were studied in 38 sedentary middle-aged men (aged 35-50 yrs) during a 30 week marathon training programme. Basal CK activity rose by 33% after 15 weeks but a significant rise (27%) in LDH activity took 30 weeks to occur. Post-exercise (maximum test on a bicycle ergometer) CK and LDH activities were higher than pre-exercise levels but the increment in enzyme activity following exercise did not change. LDH1 and LDH2 isoenzyme activity increased by 2.5% and 4% of total LDH respectively while LDH3 and LDH5 decreased by 3.9% and 2.4% respectively over 30 weeks. Post marathon total CK did not correlate with finishing time at 30 mins or 30 hrs post race. The range of CK MB isoenzyme activity at 30 mins post race was 1.8-9.8% of total CK with 11 subjects having a value above 6%. The training programme appears not to have affected muscle CK and LDH release during exercise but isoenzyme distribution changes reflect the adaptations known to occur in muscle during endurance training. Unfortunately only 16 subjects were available for all the investigations, and it is these upon whom most of the data were obtained.

Creatine kinase and creatine kinase MB in endurance runners and in patients with myocardial infarction

Following a 100 km race creatine kinase (CK) creatine kinase MB (CKMB) activities were serially measured in well trained athletes and compared with enzyme activities in patients with acute myocardial infarction (AMI). The half-time of disappearance of CK (CKt1/2) was 1.75 +/- 0.70 days in runners who trained within the 1st week after the race, and was 0.81 +/- 0.18 days in patients with AMI, P less than 0.005. CKt1/2 in runners was shorter (1.17 +/- 0.28 days) when no training was performed in the first postrace week. CKt1/2 was linearly correlated with age (P less than 0.01) in the runners but not in the patients. CKMBt1/2 was 1.30 and 1.11 days in two runners and 0.56 +/- 0.10 days in patients with AMI (P less than 0.05). In line with histologic and enzymatic findings in skeletal muscle of long distance runners as reported by other workers, our kinetic data provide further evidence that CK and CKMB are released from muscular compartments in runners other than those in patients with AMI.

Skeletal muscle injury and repair in marathon runners after competition

Elevated serum creatine kinase MB isoenzyme (CK-MB) activity in marathon runners after competition may arise from injury to skeletal muscle, myocardium, or a combined tissue source. Normal radionuclide myocardial scintigraphy and the selective increase in skeletal muscle CK-MB reported in such runners strongly suggest a peripheral source. To understand this biochemical finding, the authors examined gastrocnemius muscles by electron microscopy from 40 male marathon runners at intervals after competition and from 12 male nonrunners. Muscle from runners showed post-race ultrastructural changes of focal fiber injury and repair: intra- and extracellular edema with endothelial injury; myofibrillar lysis, dilation and disruption of the T-tubule system, and focal mitochondrial degeneration without inflammatory infiltrate (1-3 days). The mitochondrial and myofibrillar damage showed progressive repair by 3-4 weeks. Late biopsies showed central nuclei and satellite cells characteristic of the regenerative response (8-12 weeks). Muscle from veteran runners showed intercellular collagen deposition suggestive of a fibrotic response to repetitive injury. Control tissue from nonrunners showed none of these findings. The sequential morphologic changes in runners suggest that the increase in skeletal muscle CK-MB is a marker of cellular regeneration.

Plasma creatine kinase after the marathon--a diagnostic dilemma

The mechanism of the protein leak from exercised muscle remains obscure, but may be related to depletion of intracellular high-energy phosphate and/or to mechanical disruption. The high levels of creatine kinase (CK) and other muscle proteins found in plasma for several days after marathon running, especially downhill running, are due to protein efflux from skeletal muscle. There is no evidence that marathon running damages the healthy, well-perfused myocardium, despite the fact that the plasma levels of total creatine kinase (CK), the isoenzyme CK-MB, CK-MB/total CK (%), myoglobin, aspartate transaminase, lactate dehydrogenase and tropomyosin may be the same as after myocardial infarction. These indices must be interpreted with the greatest caution when found in anyone who habitually undertakes strenuous exercise, especially if they have done so within the previous week.

C reactive protein concentrations during long distance running

Long distance runners competing in events ranging from 15 to 88 km showed a distance related acute phase response as indicated by significantly raised serum C reactive protein concentrations. In trained athletes only a small rise in C reactive protein concentrations was seen after races of less than 21 km. After an 88 km ultramarathon concentrations comparable to those found in patients with small myocardial infarctions were detected. Indomethacin did not affect the increases in C reactive protein after the ultramarathon. This study has established serial C reactive protein concentrations for given race distances. These data may help in diagnosing myocardial infarction during long distance running. The acute phase response should be measured in untrained people running shorter distances to provide comparative data for the physically untrained population.

Creatine kinase levels after jogging in patients with cardiac disease

Acute muscle injury is a well-documented complication of strenuous exercise, but milder forms of exertion have not been studied in detail. This report describes a patient undergoing cardiac rehabilitation in whom atypical chest pain developed and who was treated for a myocardial infarction only because of an elevated creatine kinase level. Serum creatine kinase levels were determined before and after exercise in 27 patients undergoing cardiac rehabilitation. In 21 patients who jogged less than three miles, creatine kinase levels were not appreciably changed. In six patients who jogged more than three miles, the mean creatine kinase level rose from 41 to 54 mU/ml, an increase of 31 percent. In four of these six patients, creatine kinase levels rose to abnormal levels, but MB creatine kinase levels remained normal, with no clinical evidence of myocardial ischemia. Serum creatine kinase levels should be interpreted with caution in the setting of even modest exercise.

Evidence of impaired left ventricular performance after an uninterrupted competitive 24 hour run

The effect of extremely exhaustive exercise on left ventricular performance was studied echocardiographically in 13 experienced male ultramarathon runners who took part in a competitive 24 hr run, completing distances of 114 to 227 km. Although the left ventricular end-diastolic dimension (EDD) was reduced by 7% (54 +/- 5 to 50 +/- 7 mm; p less than .005), the end-systolic dimension (ESD) increased slightly (33 +/- 5 to 34 +/- 6 mm; NS). As a consequence, the stroke dimension (21 +/- 2 to 16 +/- 2 mm; p less than .005) and fractional shortening (38 +/- 5% to 32 +/- 5%; p less than .005) declined by 24% and 16%, respectively. The reduction in fractional shortening was related to delta ESD (r = -.66; p less than .05) but not to delta EDD (r = .22; NS). In spite of reduced afterload, the mean velocity of circumferential fiber shortening also decreased by an average of 9% (p less than .01) in proportion to the distance completed (r = -.69; p less than .01). The systolic blood pressure/ESD ratio was 21% lower after the race (4.2 +/- 0.9 to 3.3 +/- 0.6; p less than .005). Body weight loss was not related to any alterations in left ventricular dimensions or ejection phase indexes. The stroke dimension and ejection phase indexes continued to decline within the last 6 hr of the race but returned to the prerace level 2 to 3 days after the race. Total serum creatine kinase peaked at 3917 to 64740 U/liter (mean 27427) and its MB percentage peaked at 2% to 6%.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of serum creatine kinase and creatine kinase MB activities post marathon race versus post myocardial infarction

Serial total creatine kinase (CK) and CK MB activities were determined in the serum of seven runners following a marathon race and compared to enzyme activities in the sera from five patients following acute myocardial infarction (AMI). In the runner's sera, total CK and CK MB activities were significantly elevated at 1, 24, 48 and 72 hours post marathon race when compared to the 1 hour pre-marathon samples (p less than 0.01). Serum CK MB activities peaked at 24 hours in both groups of subjects. The MB activities 24 hours following the marathon were substantially higher (91 +/- 30 U/l; mean +/- SD) than the MB activities 24 hours following AMI (46 +/- 38 U/l). However, the percentages of CK MB 24 hours following the marathon and AMI were almost identical (7.0 +/- 2.4% and 7.2 +/- 2.3%, respectively). Furthermore, CK and CK MB clearances were significantly prolonged (p less than 0.02 and p less than 0.001, respectively) following the marathon race (T 1/2 CK, 49 hours; T 1/2 CK MB, 29 hours) as compared to following AMI (T 1/2 CK, 27 hours; T 1/2 CK MB, 12 hours). These results suggest release of CK MB from the skeletal muscle of marathon runners. Therefore, we recommend that elevation of CK MB in the range indicative of myocardial damage be interpreted with caution in long-distance runners.

Plasma MB creatine kinase after vigorous exercise in professional athletes

Plasma MB creatine kinase (CK) activity was quantitatively evaluated by several independent methods in 9 young professional athletes after vigorous exercise in competitive football games. Seven of the 9 had elevated total plasma CK activity. None had clinical findings of myocardial injury. However, 4 of the 7 with total CK elevations also had elevated MB-CK. MB-CK elevations occurred in players with the highest elevations of total CK activity. It is known that well-trained athletes liberate less conventionally measured muscle enzyme into the blood after exertion than do untrained individuals. These results indicate that a substantial fraction of professional athletes who engage in unusually vigorous exercise have elevations of plasma MB-CK that should not be interpreted as necessarily indicative of myocardial ischemic injury.

Significance of elevated MB creatine kinase in patients after cardiac catheterization

To clarify the etiology of elevations in plasma MB creatine kinase (CK) in patients after cardiac catheterization, we studied 32 consecutive patients undergoing cardiac catheterization and coronary arteriography. Total CK and MB CK were within the normal range in all patients prior to catheterization. Total CK activity rose from a mean of 61.46 +/- 33.8 IU/1 (SD) to 141 +/- 105 in the first sample after catheterization (p less than .005) and 121.6 +/- 92.4 in the second catheterization sample (p less than .0005). The MB CK activity also rose from a mean of 3.2 +/- 1.6 IU/1 prior to catheterization to a maximum value of 5.0 +/- 2.9. The mean increase in MB CK, though statistically significant (p less than .005), was only 1.8 IU/1. Only one patient's value for MB CK rose to outside of the normal range (greater than 12) likely due to cardiac injury. Thus, our data document that marked elevations in MB CK after cardiac catheterization are unusual. They likely represent cardiac muscle injury rather than MB CK released due to skeletal muscle injury induced by the catheterization itself.

Effect of exercise on plasma pyruvate kinase and creatine kinase activity

Plasma pyruvate kinase (PK) and creatine kinase (CK) were measured in healthy subjects engaging in (a) mild exercise, 30 min on an exercise cycle maintaining a pulse rate of 150/min, (b) moderate exercise, squeezing a ball until exhaustion with a sphygmomanometer cuff inflated above systolic pressure around the arm (max. 2 min) and (c) severe exercise, completing a marathon race. Mild exercise resulted in no change in enzyme levels over 24 h. Moderate exercise produced a small increase in PK but no change in CK. PK activity rose from 35.3 +/- 10 U/l pre-exercise to 41.3 +/- 13 U/l 15 min post-exercise (n = 8, p less than 0.025). Severe exercise (completing a marathon race) resulted in a 3-fold increase in PK from 26 (4-87) U/l pre-race to 69 (21-156) U/l immediately post-race, and also, as expected, an increase in CK from 60 (15-164) U/l to 257 (72-1535) U/l (results are means and ranges, n = 69, p less than 0.001 for both enzymes). Runners showed parallel increases in PK and CK (p less than 0.05 by Spearman rank correlation). The mean post-race activity of CK-MB was less than 5% of total CK but 18 runners had values greater than 6% (mean 4.8, range 1-18). We conclude that PK, like CK, is increased following exercise due to liberation of muscle enzyme. However, only severe exercise is likely to lead to a substantial increase in plasma PK activity and therefore prejudice its clinical usefulness as a diagnostic test.