Echocardiographic assessment of left ventricular performance before and after marathon running

The value of perioperative biomarker release for the assessment of myocardial injury or infarction in cardiac surgery

OBJECTIVES

Cardiac biomarkers are indicators of irreversible cell damage. Current myocardial infarction (MI) definitions require concomitant clinical characteristics. For perioperative MI, a correlation of biomarker elevations and mortality has been suggested. Definitions emerged relying on cardiac biomarker release only. This approach is questionable as several clinical and experimental scenarios exist where relevant biomarker release can occur apart from MI.

METHODS

We reviewed the clinical and basic science literature and revealed important aspects regarding the use and interpretation of cardiac biomarker release with special focus on their interpretation in the perioperative setting.

RESULTS

Ischaemic biomarkers may be released without cell death in multiple conditions, such as after endurance runs in athletes, temporary inotropic stimulation in animal models and flow variations in in vitro cell models. In addition, access through atrial tissue during cannulation or concomitant valve procedures adds sources of enzyme release that may not be related to ventricular ischaemia (i.e. MI). Such non-cell death-related mechanisms may explain the lack of poor correlations of enzyme release and long-term outcomes in recent trials. In addition, the 3 main biomarkers, troponin T, I and creatine kinase myocardial band, differ in their release kinetics, which may differentially trigger MI events in trial patients.

CONCLUSIONS

The identification of irreversible myocardial injury in cardiac surgery based only on biomarker release is unreliable. Cell death- and non-cell death-related mechanisms create a mix in the perioperative setting that requires additional markers for proper identification of MI. In addition, the 3 most common ischaemic biomarkers display different release kinetics adding to the confusion. We review the topic.

SUBJ COLLECTION

120, 123.

Acute effects of long-distance races on heart rate variability and arterial stiffness: A systematic review and meta-analysis

This study systematically reviewed and quantified the effects of running a long-distance race (LDR) on heart rate variability (HRV) and arterial stiffness (AS). All types of races of a distance equal to or greater than a marathon (≥42.2 km) were included. A total of 2,220 articles were identified, 52 were included in the qualitative analysis, and 48 were meta-analysed. The standardised mean difference pre- and post-race of various time-domain and frequency-domain indices of HRV, mean arterial blood pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP) and carotid-femoral pulse wave velocity (cfPWV) was calculated. Regarding HRV, there was a significant decrease in most of the variables considered as markers of parasympathetic activity, indicating a shift of autonomic balance towards a reduced vagal tone. Regarding vascular variables, there was a significant drop in blood pressure and reduced AS. In conclusion, running an LDR seems to have a considerable acute effect on the autonomic nervous system, haemodynamics, and vascular properties. The observed effects could be categorised within the expected acute responses to long-lasting, strenuous exercise.

Post-exertional increase in first-phase ejection fraction in recreational marathon runners

OBJECTIVES

Running a marathon has been equivocally associated with acute changes in cardiac performance. First-phase ejection fraction is a novel integrated echocardiographic measure of left ventricular contractility and systo-diastolic coupling which has never been studied in the context of physical activity. The aim of this study was to assess first-phase ejection fraction following recreational marathon running along with standard echocardiographic indices of systolic and diastolic function.Design and participants: Runners (n = 25, 17 males), age (mean ± standard deviation) 39 ± 9 years, were assessed before and immediately after a marathon race which was completed in 4 h, 10 min ± 47 min.

MAIN OUTCOME MEASURES

Central hemodynamics were estimated with applanation tonometry; cardiac performance was assessed using standard M-mode two-dimensional Doppler, tissue-doppler imaging and speckle-tracking echocardiography. First-phase ejection fraction was calculated as the percentage change in left ventricular volume from end-diastole to the time of peak aortic blood flow.

RESULTS

Conventional indices of systolic function and cardiac performance were similar pre- and post-race while aortic systolic blood pressure decreased by 9 ± 8 mmHg (P < 0.001) and first-phase ejection fraction increased by approximately 48% from 16.3 ± 3.9% to 22.9 ± 2.5% (P < 0.001). The ratio of left ventricular transmitral Doppler early velocity (E) to tissue-doppler imaging early annular velocity (e') increased from 5.1 ± 1.8 to 6.2 ± 1.3 (P < 0.01).

CONCLUSION

In recreational marathon runners, there is a marked increase in first-phase ejection fraction after the race despite no other significant change in cardiac performance or conventional measure of systolic function. More detailed physiological studies are required to elucidate the mechanism of this increase.

Relation of biomarkers and cardiac magnetic resonance imaging after marathon running

Although previous studies including endurance athletes after marathon running have demonstrated biochemical evidence of cardiac injury and have correlated these findings with echocardiographic evidence of cardiac dysfunction, particularly of the right ventricle, a study of marathon athletes incorporating biomarkers, echocardiography, and cardiac magnetic resonance (CMR) imaging has not been performed to date. The aim of this study was to demonstrate the cardiac changes associated with participation in a marathon using serial cardiac biomarkers, echocardiography, and CMR imaging. Fourteen participants (mean age 33 +/- 6 years, 8 men) completed the full marathon. Myoglobin, creatine kinase, and troponin T were elevated in all athletes after the race. There was a strong linear correlation between right ventricular (RV) fractional area change as assessed by echocardiography and the RV ejection fraction as assessed by CMR imaging (r = 0.96) after the marathon. RV function, using echocardiography, transiently decreased from before to after the race (RV fractional area change 43 +/- 4% vs 33 +/- 5%, p <0.05). There were also postrace changes in left ventricular and RV diastolic filling. Although RV systolic changes were transient, left ventricular and RV diastolic abnormalities persisted up to 1 week after the marathon. No evidence of delayed enhancement of the left ventricular myocardium was found on CMR imaging, suggesting that the increase in cardiac biomarkers after the marathon may not have be due to myocardial necrosis. In conclusion, RV systolic dysfunction transiently occurs after a marathon and has been validated for the first time by CMR imaging. The increase in cardiac troponin after marathon running is likely due to the cytosolic release of the biomarker, not to the true breakdown of the myocyte, as confirmed by delayed enhancement CMR imaging.

Alterations in autonomic function and cerebral hemodynamics to orthostatic challenge following a mountain marathon

We examined potential mechanisms (autonomic function, hypotension, and cerebral hypoperfusion) responsible for orthostatic intolerance following prolonged exercise. Autonomic function and cerebral hemodynamics were monitored in seven athletes pre-, post- (<4 h), and 48 h following a mountain marathon [42.2 km; cumulative gain ∼1,000 m; ∼15°C; completion time, 261 ± 27 (SD) min]. In each condition, middle cerebral artery blood velocity (MCAv), blood pressure (BP), heart rate (HR), and cardiac output (Modelflow) were measured continuously before and during a 6-min stand. Measurements of HR and BP variability and time-domain analysis were used as an index of sympathovagal balance and baroreflex sensitivity (BRS). Cerebral autoregulation was assessed using transfer-function gain and phase shift in BP and MCAv. Hypotension was evident following the marathon during supine rest and on standing despite increased sympathetic and reduced parasympathetic control, and elevations in HR and cardiac output. On standing, following the marathon, there was less elevation in normalized low-frequency HR variability ( P < 0.05), indicating attenuated sympathetic activation. MCAv was maintained while supine but reduced during orthostasis postmarathon [−10.4 ± 9.8% pre- vs. −15.4 ± 9.9% postmarathon (%change from supine); P < 0.05]; such reductions were related to an attenuation in BRS ( r = 0.81; P < 0.05). Cerebral autoregulation was unchanged following the marathon. These findings indicate that following prolonged exercise, hypotension and postural reductions in autonomic function or baroreflex control, or both, rather than a compromise in cerebral autoregulation, may place the brain at risk of hypoperfusion. Such changes may be critical factors in collapse following prolonged exercise.

Preload maintenance and the left ventricular response to prolonged exercise in men

This study examined whether left ventricular function was reduced during 3 h of semi-recumbent ergometer cycling at 70% of maximal oxygen uptake while preload to the heart was maintained via saline infusion. Indices of left ventricular systolic function (end-systolic blood pressure-volume relationship, SBP/ESV) and diastolic filling (ratio of early to late peak filling velocities into the left ventricle, E:A) were calculated during recovery and compared with baseline resting data. During exercise in seven healthy, trained male subjects, an arterial catheter allowed continuous assessment of arterial pressure, stroke volume (SV), cardiac output ( ) and an index of contractility (dP/dt(max)). A venous catheter assessed that central venous pressure (CVP) was maintained throughout rest, exercise and 10 min into recovery. Both systolic blood pressure and heart rate (HR) increased with the onset of exercise (from 132 +/- 5 to 185 +/- 19 mmHg and from 66 +/- 9 to 135 +/- 23 beats min(-1); increases from rest to the end of the first 5 min of exercise in SBP and HR, respectively) but systolic blood pressure did not change from 30 to 180 min of exercise ( approximately 150 mmHg), while heart rate only increased by 8 +/- 9 beats min(-1) (means +/- s.d.; P > 0.05). The attenuated increase in HR compared with other studies suggests that the maintained CVP ( approximately 5 mmHg) helped to prevent cardiovascular drift in this protocol. Stroke volume, and dP/dt(max) were all increased with the onset of exercise (from 85 +/- 8 to 120 +/- 18 ml, from 5.4 +/- 1.3 to 16.5 +/- 3.3 l min(-1) and from 14.4 +/- 4 to 28 +/- 8 mmHg s(-1); values from rest to the end of the first 5 min of exercise for SV, and dP/dt(max), respectively) and were maintained during exercise. There was no difference in the SBP/ESV ratio from pre- to postexercise. Conversely, E:A was reduced from 2.0 +/- 0.4 to 1.6 +/- 0.5 postexercise (P < 0.05), returning to normal values at 24 h postexercise. This change in diastolic filling could not be fully explained (r(2) = 0.39) by an increased heart rate and, with CVP unchanged, it is likely to represent some depression of intrinsic relaxation properties of left ventricular myocytes. Three hours of semi-supine cycling resulted in no evidence of a depression in left ventricular systolic function, while left ventricular diastolic function declined postexercise.

Cardiac Manifestations of Exhaustive Exercise in Nonathletic Adults: Does Cardiac Fatigue Occur?

The aim of the study was to examine the impact of prolonged exercise leading to physical exhaustion on left ventricular (LV) systolic and diastolic function in untrained healthy subjects, and to examine cardiovascular determinants of exercise performance. Twenty-four nonathletic healthy adults (14 males, 10 females; mean age 42 +/- 11 years) were exercised on a treadmill at 70% of maximal oxygen consumption until physical exhaustion occurred after an average of 84 +/- 39 minutes. Two-dimensional and Doppler echocardiography was performed before and 15 minutes after exercise to assess LV function and geometry, and right ventricular (RV) systolic function. After prolonged exercise, LV ejection fraction and geometry were unchanged, but LV end-diastolic volume, end-systolic volume, and stroke volume decreased. However, due to a higher heart rate (HR), cardiac output increased at 15 minutes post exercise. RV fractional shortening was unchanged. LV peak early to atrial filling velocity ratio decreased post exercise, with an increase in percent atrial contribution. However, less preload-dependent variables of LV diastolic function such as deceleration time, LV inflow propagation rate, mitral annular tissue Doppler and myocardial performance index were unchanged. Preexercise stroke volume and HR were the only predictors (r = 0.86, P < 0.01) of exercise duration. However, age, resting blood pressure, indices of systolic and diastolic function, and LV geometry were not predictors. Prolonged exercise leading to physical exhaustion is not associated with systolic or diastolic dysfunction. Reduced early LV diastolic filling and the relative increase in left atrial contribution seen with prolonged exercise are likely due to preload reduction rather than true diastolic dysfunction.

Left Ventricular Function Immediately following Prolonged Exercise

PURPOSE

Evidence supporting cardiac fatigue following prolonged endurance exercise remains equivocal. The purpose of this meta-analysis was to quantify all data fulfilling the specified inclusion criteria, examining the short-term effect of prolonged endurance exercise on left ventricular function.

METHODS

A random effects meta-analysis of the weighted mean change in ejection fraction (EF), systolic blood pressure/end systolic volume (SBP/ESV) ratio, and early-to-late diastolic filling (E/A) was conducted on 23 studies using the SE of the between-subjects SD. HR, SBP, and left ventricular internal diameter during diastole (LVIDd) were also analyzed. Studies were coded according to exercise duration and training status: moderate duration trained (MDt) and untrained (MDu), 60-150 min; long duration (LD), 166-430 min; and ultra duration (UD), 640-1440 min. Relationships were assessed via Pearson's product-moment correlation.

RESULTS

A significant (P < 0.05) overall decrease in EF (mean, confidence interval (CI): -1.95%, -1.03 to -2.88%), SBP/ESV (mean, CI: -0.8, -0.63 to -0.97), and E/A (mean, CI: -0.45, -0.39 to -0.51) was observed. Only UD and MDu subgroups demonstrated a reduction in EF. All subgroups demonstrated significant (P < 0.05) decreases in E/A. Alterations in LVIDd and SBP were related to respective decreases in EF and SBP/ESV, but not to E/A.

CONCLUSION

The decrease in EF and SBP/ESV observed in UD and MDu indicates a reduction in systolic function, partially explained by altered cardiac loading. A decrease in E/A in all subgroups, unrelated to changes in loading, suggests an intrinsic impairment of left ventricular relaxation. Future investigators should employ load-independent indices of cardiac function and attempt to uncover the mechanisms of this phenomenon.

Persistent and reversible cardiac dysfunction among amateur marathon runners

AIMS

Transient systolic and diastolic abnormalities in ventricular function have previously been documented during endurance sports. However, these described alterations may be limited by the techniques applied. We sought, using less load-dependent methods, to characterize both the extent and the chronology of the cardiac changes associated with endurance events.

METHODS AND RESULTS

Transthoracic echocardiography (TTE) was performed prior to, immediately after, and approximately 1 month after completion of the 2003 Boston Marathon in 20 amateur athletes. TTE included two-dimensional, spectral and tissue Doppler (TD) and flow propagation velocity (V(p)). After completion of the marathon, global measures of left ventricular (LV) systolic function were unchanged (EF 59 +/- 6 vs. 61 +/- 4% post, P = 0.14), whereas TD-derived measures of LV systolic function [septal strain -23 +/- 5 vs. -17 +/- 4%, P = 0.007; septal strain rate (SR) -1.5 +/- 0.3 vs. -1.1+/- 0.2 s(-1), P = 0.007] and right ventricular (RV) systolic function (RV apical strain -33 +/- 4 vs. -27 +/- 5%, P = 0.001; RV apical SR -2.4 +/- 0.7 vs. -1.8 +/- 0.5, P = 0.002) were reduced. Significant changes in transmitral velocity (E/A ratio 2.0 +/- 0.5 vs.1.3 +/- 0.3, P = 0.005) and TD indices of LV and RV diastolic function (E(a) septal 9.5 +/- 1.8 vs. 8.1 +/- 1.2 cm/s post-marathon, P = 0.01) were also observed, indicating an inherent alteration in LV relaxation. Although all indices of LV and RV systolic function had returned to normal on follow-up, there were persistent diastolic abnormalities (RV E(a), 11.5 +/- 1.5 cm/s pre-marathon vs. 10.0 +/- 1.6 cm/s follow-up, P = 0.01).

CONCLUSION

Marathon running leads to transient systolic and more persistent diastolic dysfunction of both the LV and the RV.

Preload maintenance protects against a depression in left ventricular systolic, but not diastolic, function immediately after ultraendurance exercise

OBJECTIVE

To investigate indices of left ventricular (LV) function before and after a 224 km Ironman triathlon, specifically in the presence of unaltered haemodynamic loading.

METHOD

LV loading and function were assessed before and after the race using M mode and Doppler echocardiography in 39 (mean (SD) age 33 (8) years, body mass 77.6 (8.6) kg; 36 male) triathletes in the Trendelenburg position. Specifically left ventricular end diastolic volume (LVEDV) was assessed to estimate preload, and systolic blood pressure to estimate afterload as well as heart rate (HR). Systolic functional indices included ejection fraction (EF) and the end systolic pressure/volume ratio (ESPV), and diastolic functional indices included peak mitral flow velocity in early (E) and atrial (A) filling as well as the ratio E/A. Data obtained before and after the race were compared by t tests, and delta LV functional indices were correlated with delta heart rate.

RESULTS

Preload (LVEDV: 143 (34) ml before v 147 (34) ml after) and afterload (systolic blood pressure 121 (13) v 115 (20) mm Hg) were not significantly altered after the race (p>0.05), nor were EF (61 (8)% v 58 (10)%) and ESPV (2.4 (0.9) v 2.1 (0.8) mm Hg/cm(3)). The diastolic filling ratio E/A was significantly reduced after the race (1.73 (0.25) v 1.54 (0.23); p<0.05) due primarily to a reduction in E. HR was significantly higher after the race (57 (9) v 75 (8) beats/min; p<0.05), but delta HR was not related to delta E/A (p>0.05).

CONCLUSION

When preload and afterload are unaltered after the race, because of the adoption of a unique assessment posture, LV systolic function is not depressed. A depression in LV diastolic function persists which is not explained by an increase in heart rate after the race.

Mitral annular myocardial velocity assessment of segmental left ventricular diastolic function after prolonged exercise in humans

We assessed segmental and global left ventricular (LV) diastolic function via tissue-Doppler imaging (TDI) as well as Doppler flow variables before and after a marathon race to extend our knowledge of exercise-induced changes in cardiac function. Twenty-nine subjects (age 18-62 year) volunteered to participate and were assessed pre- and post-race. Measurements of longitudinal plane TDI myocardial diastolic velocities at five sites on the mitral annulus included peak early myocardial tissue velocity (E'), peak late (or atrial) myocardial tissue velocity (A') and the ratio E'/A'. Standard pulsed-wave Doppler transmitral and pulmonary vein flow indices were also recorded along with measurements of body mass, heart rate, blood pressures and cardiac troponin T (cTnT), a biomarker of myocyte damage. Pre- to post-race changes in LV diastolic function were analysed by repeated measures ANOVA. Delta scores for LV diastolic function were correlated with each other and alterations in indices of LV loading. Diastolic longitudinal segmental and mean TDI data were altered post-race such that the mean E'/A' ratio was significantly depressed (1.51 +/- 0.34 to 1.16 +/- 0.35, P < 0.05). Changes in segmental and global TDI data were not related to an elevated post-race HR, a decreased post-race pre-load or an elevated cTnT. The pulsed wave Doppler ratio of peak early transmitral flow velocity (E)/peak late (or atrial) flow velocity (A) was also significantly reduced post-race (1.75 +/- 0.46 to 1.05 +/- 0.30, P < 0.05); however, it was significantly correlated with post-race changes in heart rate. The lack of change in E/E' from pre- to post-race (3.4 +/- 0.8 and 3.3 +/- 0.7, respectively) suggests that the depression in diastolic function is likely to be due to altered relaxation of the left ventricle; however, the exact aetiology of this change remains to be determined.

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.

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.

Effects of prolonged exercise to exhaustion on left-ventricular function and pulmonary gas exchange

The purpose of this study was to simultaneously examine left-ventricular (LV) function and pulmonary gas exchange during prolonged constant-rate cycling in an attempt to explain the exercise-induced impairment in gas exchange. Eleven competitive cyclists rode their racing bicycles on a computerized cycle trainer at 25 W below the lactate threshold until exhaustion (exercise time = 2.51 +/- 0.86 h). LV systolic function was evaluated with two-dimensional echocardiography while arterial blood gases were used to assess pulmonary gas exchange. All variables were assessed concurrently before, during, and after exercise. LV function and cardiac output increased at the onset of exercise and were maintained until exhaustion. The alveolar-arterial P(O(2)) difference (A-a D(O(2))) increased within 15 min of the onset of exercise, was unchanged through to exhaustion, and returned to baseline 5 min post-exercise. Gas exchange was not related to cardiovascular function at the onset, or at end exercise. The results indicate that the widening A-aD(O(2)) during exercise is due to a readily reversible change in gas exchange function.

Myocardial perfusion after marathon running

We investigated the effects of acute prolonged exercise (marathon running) on cardiac function and myocardial perfusion. Cardiac dimensions and function were measured in seven endurance-trained men using echocardiography before and repeatedly after marathon (42.2 km) running (at 10 min, 150 min, and 20 h). Myocardial perfusion and perfusion resistance were measured using positron emission tomography and 15O-H2O before and 85-115 min after running. Echocardiographic indices showed only mild and clinically non-significant changes in cardiac function after running. Rate-pressure-corrected basal myocardial perfusion (0.89+/-0.13 vs. 1.20+/-0.32 mL min(-1) g(-1), P=0.04) was increased after running. Also, adenosine-stimulated perfusion tended to be higher (3.67+/-0.81 vs. 4.47+/-0.52 mL min(-1) g(-1), P=0.12) and perfusion resistance during adenosine stimulation was significantly lower after running (26+/-6 vs. 18+/-3 mmHg min g mL(-1), P=0.03). Plasma free fatty acid (FFA) concentration was significantly increased after running. These results show that marathon running does not cause marked changes in cardiac function in healthy men. Basal perfusion was increased after exercise, probably reflecting changes in fuel preferences to increased use of FFAs. Strenuous exercise also seems to enhance coronary reactivity, which could thereby serve as a protective mechanism to vascular events after exercise.

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.

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.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

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.

Left ventricular performance during prolonged exercise and early recovery in healthy subjects

The effect of semi-supine long lasting exercise to exhaustion [61 (SD 10) min] on left ventricular systolic performance was studied by echocardiography in 16 young healthy volunteers. During the incremental phase of exercise, the ejection fraction increased from 65.2 (SD 4.1)% to 80.1 (SD 4.8)% (P < 0.0001), then it levelled off up to the end of exercise [81.7 (SD 4.4)%, P < 0.0001 vs rest]. During recovery, the ejection fraction rapidly and steadily decreased to a value similar to that at rest [66.1 (SD 5.0)%, n.s.). A similar pattern was shown by the systolic blood pressure/end-systolic volume coefficient, which rose from 3.2 (SD 0.8) mmHg.ml-1 to 7.5 (SD 2.7) mmHg.ml-1 (P < 0.0001) in the initial phase and subsequently did not change until the end of exercise [7.0 (SD 2.2) mmHg.ml-1, P < 0.0001 vs rest], to fall sharply after the cessation of exercise [2.9 (SD 1.1) mmHg.ml-1 at the 10th min, n.s. vs rest]. Exercise and recovery indices of left ventricular performance were not correlated with exercise duration, maximal heart rate and increase in free fatty acids. The present results indicated that, after the initial increase, left ventricular performance remained elevated during prolonged high intensity exercise and that conclusions on exercise cardiac performance drawn from postexercise data can be misleading.

Peak exercise left ventricular performance in normal subjects and in athletes assessed by first-pass radionuclide angiography

The role of Frank-Starling law of the heart in determining the increase in cardiac output during exercise in humans is still controversial (e.g., the mechanisms responsible for the enhancement of left ventricular [LV] filling during the shortened diastolic interval). Ten weight lifters, 12 swimmers and 12 sedentary subjects who underwent maximal upright bicycle exercise testing were studied. First-pass radionuclide angiography was performed both at rest and at peak exercise using a multicrystal gamma camera. Compared with resting values, heart rate and cardiac index at peak exercise increased by 101 +/- 16 beats/min (p less than 0.001) and 6.7 +/- 2.8 liters/min/m2 (p less than 0.001) in weight lifters, by 96 +/- 9 beats/min (p less than 0.001) and 9.5 +/- 2 liters/min/m2 (p less than 0.001) in swimmers, and by 103 +/- 9 beats/min (p less than 0.001) and 7.3 +/- 1.8 liters/min/m2 (p less than 0.001) in sedentary subjects. Stroke volume increased by 20.5 +/- 9.8 ml/m2 (p less than 0.001) in swimmers only. End-diastolic volume at peak exercise did not change in weight lifters and in swimmers; it decreased by 8.2 +/- 8.6 ml/m2 (p less than 0.01) in sedentary subjects. A significant correlation was found between the decrease in end-systolic volume and the increase in peak rapid filling rate at peak exercise in all 3 groups (r = 0.65, p less than 0.05 in weight lifters; r = 0.59, p less than 0.05 in swimmers; r = 0.67, p less than 0.05 in sedentary subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Different effects of prolonged exercise on the right and left ventricles

To examine the functional consequences of the greater increase in right ventricular work with exercise, the effects of prolonged exercise on the right and left heart chambers were compared in 41 athletes before, at the finish (13 min) and after recovery (28 h) from the Hawaii Ironman Triathlon (3.9 km swim, 180.2 km bike ride, 42.2 km run). Two-dimensional and Doppler echocardiograms were analyzed for left and right atrial and ventricular areas at end-diastole and end-systole, right and left ventricular inflow velocities and mitral and tricuspid regurgitation. After exercise, left ventricular and left and right atrial sizes were reduced, whereas right ventricular size increased (diastole: 21.4 to 24.2 cm2; systole: 15.8 to 18.2 cm2; p less than 0.01). The emptying fraction of all chambers was unchanged. Left but not right ventricular inflow showed an increase in peak velocity of rapid filling, whereas both atrial systolic velocities increased (26 to 38 cm/s tricuspid; 38 to 54 cm/s mitral; both p less than 0.01). Overall, the right ventricular early to atrial velocity ratio was reduced after exercise (1.56 to 1.17; p less than 0.05) and the left ventricular pattern was unchanged. The prevalence of tricuspid regurgitation was statistically unchanged (86% to 52%), although that of mitral regurgitation was greatly reduced (76% to 0%). Changes in all variables returned toward prerace values during recovery. Thus, in highly trained athletes, prolonged exercise causes differing responses of the right and left ventricles. These differences may be due to changes in right ventricular function, shape or compliance.

Applied physiology of a triathlon

The triathlon is an endurance contest in which contestants must compete in 3 consecutive events, usually swimming, cycling and running. Success in a triathlon depends upon the ability of the triathlete to perform each of the sequential events at optimal pace without creating fatigue that will hinder performance in the next event. The successful triathlete must, therefore, have highly developed oxygen transport and utilisation systems as well as the ability to efficiently produce a high energy output for prolonged periods without creating metabolic acidosis. Accordingly, mean VO2max values for groups of triathletes during treadmill running have been reported to range from 52.4 to 72 ml/kg/min in men; 58.7 to 65.9 ml/kg/min in women. VO2max values during cycle ergometry were 3 to 6% less than treadmill running values; tethered swimming maximums 13 to 18% less. Predictable and well-known adaptations occur in the cardiovascular systems of triathletes. Structural adaptations of the heart that have been documented in triathletes include increased left ventricular cavity size or wall thickness, or both. Morphological characteristics of the triathlete's heart appear to be unrelated to success in triathlon races. Following the acute stress of triathlon competition, alterations in both systolic and diastolic function have been observed. Heart muscle fatigue is the most likely reason for these changes, since there is a rapid return to normal with rest. Like the cardiovascular system, the musculoskeletal system responds to triathlon training. Peripheral adaptations occur that lead to increased muscle respiratory capacity and to modifications in substrate utilisation. The musculoskeletal system is the site of most injuries to triathletes, and non-traumatic overuse injuries account for 80 to 85% of the musculoskeletal injuries. Maintenance of fluid and electrolyte balance is of primary importance for the triathlete both in day-to-day training and during races. Water may be an adequate replacement fluid for short distance triathlons, but some combination of carbohydrate, electrolyte and fluid replacement is necessary for longer races. Although the physiological bases for success in a triathlon are not well understood at present, the ability to maintain minimal alterations in the homeostasis of cardiovascular, haemodynamic, thermal, metabolic, and musculoskeletal functions are of obvious importance.

Blood pressure and plasma catecholamine responses to various challenges during exercise-recovery in man

The purpose of this study was to assess the effects of a 2 h cycle exercise (50% VO2max) on heart rate (HR) and blood pressure (BP), and on plasma epinephrine (E) and norepinephrine (NE) concentrations, during the recovery period in seven normotensive subjects. Measurements were made at rest in supine (20 min) and standing (10 min) positions, during isometric exercise (hand-grip, 3 min, 25% maximal voluntary, contraction), in response to a mild psychosocial challenge (Stroop conflicting color word task) and during a 5-min period of light exercise (42 +/- 3% VO2max). Data were compared to measurements taken on another occasion under similar experimental conditions, without a previous exercise bout (control). The results showed HR to be slightly elevated in all conditions following the exercise bout. However, diastolic and systolic BP during the recovery period following exercise were not significantly different from the values observed in the control situation. Plasma NE concentrations in supine position and in response to the various physiological and/or psychosocial challenges were similar in the control situation and during the recovery period following exercise. On the other hand plasma E (nmol.1-1) was about 50% lower at rest (0.11 +/- 0.03 vs 0.23 +/- 0.04) as well as in response to hand-grip (0.21 +/- 0.04 vs 0.41 +/- 0.20) and the Stroop-test (0.21 +/- 0.05 vs 0.41 +/- 0.15) following the exercise bout.(ABSTRACT TRUNCATED AT 250 WORDS)

Endurance exercise in the presence of heart disease

Although patients with heart disease have successfully completed marathon runs, the immediate cardiac effects of similar and greater distance endurance exercise competition are unknown. Two such cases are presented, demonstrating that vigorous exercise and extreme levels of fitness are not precluded in the cardiac patient.

Cardiac fatigue after prolonged exercise

To determine the effects of prolonged exercise on systolic and diastolic left ventricular function, we studied 21 athletes before, at the finish (within 11 +/- 5 min), and during recovery (28 +/- 9 hr) after the Hawaii Ironman Triathlon (2.4 mile swim, 112 mile bike, 26.2 mile run). Two-dimensionally guided M mode echocardiograms were digitized for wall thickness, cavity dimension, fractional shortening, and peak rates of cavity enlargement and wall thinning. Pulsed Doppler left ventricular inflow recordings were analyzed for peak early and late velocities and their ratio. Left ventricular diastolic dimension was reduced at race finish (5.4 +/- 0.6 to 5.1 +/- 0.6 cm) and remained reduced after 1 day of recovery (5.2 +/- 0.6 cm, p less than .05). Fractional shortening fell at race finish (39 +/- 5% to 35 +/- 5%), although systolic blood pressure was unchanged, and rose to 40 +/- 4% after recovery (p less than .05). The return to prerace shortening values after recovery occurred despite continued reduction in diastolic size. Peak circumferential shortening did not change significantly. Individual reductions in fractional shortening were correlated with increases in systolic cavity size (r = -.64, p less than .01), but not with decreases in diastolic size. The stress-shortening relationship was displaced downward at race finish, but returned toward baseline after 1 day of recovery, despite a persistent reduction in cavity size. This suggests that the decrease in shortening was due to impaired contractility as well as altered preload.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic exercise echocardiography in children with congenital heart disease affecting the left heart

Thirty-five children (male 22, female 13) with congenital heart disease resulting in volume and pressure overload of the left ventricle were investigated echocardiographically during supine bicycle exercise. The children had to follow a test-protocol with increasing workload. Left ventricular function parameters were measured from M-mode-echocardiography, electrocardiography and phonocardiograms before, during and after exercise and were expressed as fractional shortening (FS), velocity of circumferential fiber shortening (VcF) and the frequency corrected parameters: FScorr. = FS X 100/HR and VcFcorr. = VcF X 100/HR (HR = heart rate). The data of this group of children under study were compared to those obtained from 140 healthy children examined under similar conditions. In children with pressure overload, values for fractional shortening, velocity of circumferential fiber shortening and the frequency corrected parameters were significantly higher than in normals throughout exercise testing. In some children with moderate to severe aortic stenosis or coarctation the frequency corrected parameters showed a decrease at higher exercise levels instead of an increase as seen in the majority of cases. In these cases cardiac output was increased by an abnormal rise in heart rate. This was considered as a diminished left ventricular reserve. After aortic valve replacement in two cases with aortic stenosis, parameters of left ventricular function were still elevated at rest and during exercise testing. In two children with hypertrophic cardiomyopathy the almost maximally elevated rest values did not change during exercise. In children with mild volume overload (small ventricular septal defect or aortic incompetence) the left ventricular function parameters were within the normal range or slightly below.