Athlete's heart

Cardiovascular disease risk and associated physical activity factors in gastrointestinal cancer survivors

INTRODUCTION

Although the risk of CVD is increased in cancer survivors, few studies have investigated the CVD risk in survivors of gastrointestinal (GI) cancer. Therefore, we evaluated the CVD risk using the 10-year atherosclerotic cardiovascular disease (ASCVD) risk score for GI cancer survivors and associated physical activity factors.

METHODS

Using the 2014-2019 Korean National Health and Nutrition Examination Surveys, data were collected for 262 GI cancer survivors and 1,310 cancer-free controls matched at a 1:5 ratio based on age and sex. The International Physical Activity Questionnaire Short-Form was used to assess physical activity, and the Euro QoL Questionnaire 5-Dimensional Classification (EQ-5D) was used to assess the health-related quality of life.

RESULTS

A multiple logistic regression analysis demonstrated a lower risk of ASCVD in GI cancer survivors than in controls (adjusted odds ratio [aOR] = 0.73, 95% confidence interval [CI] = 0.55-0.97). Moreover, the risk of having a high ASCVD score was significantly lower in individuals who performed sufficient aerobic physical activity (aOR = 0.59, 95% CI = 0.47-0.75) and those with an EQ-5D score 1 or 2 (aOR = 0.36, 95% CI = 0.20-0.65 and aOR = 0.31, 95% CI = 0.16-0.58, respectively).

CONCLUSIONS

This population-based study demonstrated that engaging in sufficient physical activity can reduce the ASCVD risk among GI cancer survivors.

The associations of leukocyte telomere length and intermediary cardiovascular phenotype with adverse cardiovascular outcomes in the white population

The evidence about the associations of leukocyte telomere length (LTL) and intermediary cardiovascular phenotypes with adverse cardiovascular outcomes is inconclusive. This study assessed these relationships with cardiovascular imaging, electrocardiography, and the risks of sudden cardiac death (SCD), coronary events, and heart failure (HF) admission. We conducted a cross-sectional analysis of UK Biobank participants enrolled between 2006 and 2010. LTL was measured using quantitative polymerase chain reactions. Electronic health records were used to determine the incidence of SCD, coronary events, and HF admission. Cardiovascular measurements were made using cardiovascular magnetic resonance imaging and machine learning. The associations of LTL with SCD, coronary events, and HF admission and cardiac magnetic resonance imaging, electrocardiogram parameters of 33,043 and 19,554 participants were evaluated by multivariate regression. The median (interquartile range) follow-up period was 11.9 (11.2-12.6) years. Data was analyzed from January to May 2023. Among the 403,382 white participants without coronary artery disease or HF, 181,637 (45.0%) were male with a mean age of 57.1 years old. LTL was independently negatively associated with a risk of SCD (LTL third quartile vs first quartile: hazard ratio [HR]: 0.81, 95% confidence interval [CI]: 0.72-0.92), coronary events (LTL third quartile vs first quartile: HR: 0.88, 95% CI: 0.84-0.92), and HF admission (LTL fourth quartile vs first quartile: HR: 0.84, 95% CI: 0.74-0.95). LTL was also independently positively associated with cardiac remodeling, specifically left ventricular mass index, left-ventricular-end systolic and diastolic volumes, mean left ventricular myocardial wall thickness, left ventricular stroke volume, and with electrocardiogram changes along the negative degree of T-axis. Cross-sectional study results showed that LTL was positively associated with heart size and cardiac function in middle age, but electrocardiography results did not show these associations, which could explain the negative association between LTL and risk of SCD, coronary events, and HF admission in UK Biobank participants.

Moderate Endurance Exercise Increases Arrhythmia Susceptibility and Modulates Cardiac Structure and Function in a Sexually Dimorphic Manner

BACKGROUND

Although moderate endurance exercise has been reported to improve cardiovascular health, its effects on cardiac structure and function are not fully characterized, especially with respect to sexual dimorphism. We aimed to assess the effects of moderate endurance exercise on cardiac physiology in male versus female mice.

METHODS AND RESULTS

C57BL/6J mice of both sexes were run on a treadmill for 6 weeks. ECG and echocardiography were performed every 2 weeks. After 6 weeks of exercise, mice were euthanized, and triple parametric optical mapping was performed on Langendorff perfused hearts to assess cardiac electrophysiology. Arrhythmia inducibility was tested by programmed electrical stimulation. Left ventricular tissue was fixed, and RNA sequencing was performed to determine exercise-induced transcriptional changes. Exercise-induced left ventricular dilatation was observed in female mice alone, as evidenced by increased left ventricular diameter and reduced left ventricular wall thickness. Increased cardiac output was also observed in female exercised mice but not males. Optical mapping revealed further sexual dimorphism in exercise-induced modulation of cardiac electrophysiology. In female mice, exercise prolonged action potential duration and reduced voltage-calcium influx delay. In male mice, exercise reduced the calcium decay constant, suggesting faster calcium reuptake. Exercise increased arrhythmia inducibility in both male and female mice; however, arrhythmia duration was increased only in females. Lastly, exercise-induced transcriptional changes were sex dependent: females and males exhibited the most significant changes in contractile versus metabolism-related genes, respectively.

CONCLUSIONS

Our data suggest that moderate endurance exercise can significantly alter multiple aspects of cardiac physiology in a sex-dependent manner. Although some of these effects are beneficial, like improved cardiac mechanical function, others are potentially proarrhythmic.

Body Surface Potential Mapping during Ventricular Depolarization in Athletes with Prolonged PQ Interval after Exercise

BACKGROUND

Prolongation of the PQ interval, generally associated with an atrioventricular conduction delay, may be related to changes in intraventricular impulse spreading.

OBJECTIVE

To assess, using body surface potential mapping (BSPM), the process of ventricular depolarization in athletes with prolonged PQ intervals at rest and after exercise.

METHODS

The study included 7 cross-country skiers with a PQ interval of more than 200 ms (Prolonged-PQ group) and 7 with a PQ interval of less than 200 ms (Normal-PQ group). The BSPM from 64 unipolar torso leads was performed before (Pre-Ex) and after the bicycle exercise test (Post-Ex). Body surface equipotential maps were analyzed during ventricular depolarization. The significance level was 5%.

RESULTS

Compared to Normal-PQ athletes, the first and second periods of the stable position of cardiac potentials on the torso surface were longer, and the formation of the "saddle" potential distribution occurred later, at Pre-Ex, in Prolonged-PQ athletes. At Post-Ex, the Prolonged-PQ group showed a shortening of the first and second periods of stable potential distributions and a decrease in appearance time of the "saddle" phenomenon relative to Pre-Ex (to the values near to those of the Normal-PQ group). Additionally, at Post-Ex, the first inversion of potential distributions and the total duration of ventricular depolarization in Prolonged-PQ athletes decreased compared to Pre-Ex and with similar values in Normal-PQ athletes. Compared to Normal-PQ athletes, the second inversion was longer at Pre-Ex and Post-Ex in Prolonged-PQ athletes.

CONCLUSION

Prolonged-PQ athletes had significant differences in the temporal characteristics of BSPM during ventricular depolarization both at rest and after exercise as compared to Normal-PQ athletes.

Exercise induces tissue-specific adaptations to enhance cardiometabolic health

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

Phenotypic and Genetic Factors Associated with Absence of Cardiomyopathy Symptoms in PLN:c.40_42delAGA Carriers

The c.40_42delAGA variant in the phospholamban gene (PLN) has been associated with dilated and arrhythmogenic cardiomyopathy, with up to 70% of carriers experiencing a major cardiac event by age 70. However, there are carriers who remain asymptomatic at older ages. To understand the mechanisms behind this incomplete penetrance, we evaluated potential phenotypic and genetic modifiers in 74 PLN:c.40_42delAGA carriers identified in 36,339 participants of the Lifelines population cohort. Asymptomatic carriers (N = 48) showed shorter QRS duration (- 5.73 ms, q value = 0.001) compared to asymptomatic non-carriers, an effect we could replicate in two different independent cohorts. Furthermore, symptomatic carriers showed a higher correlation (rPearson = 0.17) between polygenic predisposition to higher QRS (PGSQRS) and QRS (p value = 1.98 × 10-8), suggesting that the effect of the genetic variation on cardiac rhythm might be increased in symptomatic carriers. Our results allow for improved clinical interpretation for asymptomatic carriers, while our approach could guide future studies on genetic diseases with incomplete penetrance.

Exercise-Induced Arrhythmia or Munchausen Syndrome in a Marathon Runner?

A 36-year-old professional marathon runner reported sudden irregular palpitations occurring during competitions, with heart rates (HR) up to 230 bpm recorded on a sports HR monitor (HRM) over 4 years. These episodes subsided upon the cessation of exercise. Electrocardiograms, echocardiography, and cardiac magnetic resonance imaging results were borderline for athlete's heart. Because an electrophysiology study and standard exercise tests provoked no arrhythmia, doctors suspected Munchausen syndrome. Ultimately, an exercise test that simulated the physical effort of a competition provoked tachyarrhythmia consistent with the HRM readings. This case demonstrates the diagnostic difficulties related to exercise-induced arrhythmia and the diagnostic usefulness of sports HRMs.

Echocardiography and strain analysis in Malaysian elite athletes versus young healthy adults

Background

Athletes have changes that can mimic pathological cardiomyopathy.

Methods

Echocardiographic study of 50 male, female athletes (MA, FA) and non-athletes (MNA, FNA) age 18 to 30 years. These athletes participate in sports with predominantly endurance component. All participants exhibit no known medical illnesses or symptoms.

Results

MA have thicker wall (IVSd) than MNA. No MA have IVSd > 1.2 cm and no FA have IVSd > 1.0 cm. Left ventricle internal dimension (LVIDd), left ventricle end diastolic volume index (LVEDVi) is bigger in athletes. None have LVIDd > 5.8 cm. Right ventricle fractional area change (FAC) is lower in athletes. (MA vs MNA, p = 0.013, FA vs FNA, p = 0.025). Athletes have higher septal and lateral e' (Septal e'; MA 13.57 ± 2.66 cm/s vs MNA 11.46 ± 2.93 cm/s, p < 0.001, Lateral e'; MA 17.17 ± 3.07 cm/s vs MNA 14.82 ± 3.14 cm/s, p < 0.001), (Septal e'; FA 13.46 ± 2.32 cm/s vs FNA 12.16 ± 2.05 cm/s, p = 0.04, Lateral e'; FA 16.92 ± 2.97 cm/s vs FNA 15.44 ± 2.29 cm/s, p = 0.006).No difference in Global longitudinal (GLS), Right ventricle free wall (RVFWS) and Global circumferential strain (GCS). Left atrial reservoir (LArS) and left atrial booster strain (LAbS) is smaller in athletes. (LArS, MA 44.12 ± 9.55% vs MNA 52.95 ± 11.17%, p < 0.001 LArS, FA 48.07 ± 10.06% vs FNA 53.64 ± 8.99%, p = 0.004), (LAbS, MA 11.59 ± 5.13% vs MNA 17.35 ± 5.27%, p < 0.001 LAbS FA 11.77 ± 4.65% vs FNA 15.30 ± 4.19%, p < 0.001).

Conclusion

Malaysian athletes have thicker wall and bigger left ventricle than controls. No athletes have IVSd > 1.2 cm and/or LVIDd > 5.8 cm. There is no difference in GLS, RVFWS and GCS but athletes have smaller LArS and LAbS.

Körperliche Aktivität/Sport – Auswirkung unterschiedlicher Trainingsformen und -intensitäten auf das Herz

„Das Sport-Paradox“ beschreibt die Ambivalenz zwischen einerseits klar evidenzbasierten gesundheitlichen Vorteilen des regelmäßigen Sporttreibens und andererseits der ebenso unumstrittenen gesundheitlichen Nachteile, die der Sport mit sich bringen kann.

Mindestens 30 Minuten moderate körperliche Belastung (bei Kindern 60 Minuten), an mindesten 5 Tagen pro Woche sind notwendig, um die gesundheitlichen Vorteile zu erreichen. Das Herz-Kreislaufsystem unterliegt dabei, bei regelmäßigem intensiven, vor allem dynamischem Ausdauertraining physiologischen Adapationen, welche von verschiedenen weiteren Faktoren abhängen. Während die exzentrische Hypertrophie des linken Ventrikels, in der Regel, reversibel ist, zeigt sich die „right ventricular fatigue“, bei entsprechender genetischer Belastung teilweise progredient. Dilatation und Fibrosierung der Vorhöfe führen zu einem erhöhten Risiko für ein Vorhofflimmern und auch eine häufig klinisch asymptomatische Dilatation der Aorta oder eine durch chronischen Stress bedingte Koronarsklerose können potenziell schwerwiegende Folgen mit sich bringen. Umso entscheidender sind individuelle und spezifische Trainingsempfehlungen.

Young athlete's growing heart: sex differences in cardiac adaptation to exercise training during adolescence

BACKGROUND

Athlete's heart is a condition of exercise-induced cardiac remodelling. Adult male endurance athletes more often remodel beyond reference values. The impact of sex on remodelling through adolescence remains unclear. Paediatric reference values do not account for patient sex or exercise history. We aimed to study the effect of sex on cardiac remodelling throughout adolescence.

METHODS

We recruited 76 male (M) and female (F) 12-year-old cross-country skiers in a longitudinal cohort study. Echocardiography was performed and analysed according to guidelines at age 12 (48 M, 28 F), 15 (34 M, 14 F) and 18 (23 M, 11 F). Repeated echocardiographic measurements were analysed by linear mixed model regression.

RESULTS

Males displayed greater indexed left ventricular end-diastolic volumes (LV EDVi) from age 12 (M 81±7 vs F 76±7, mL/m², p≤0.01), and progressed further until follow-up at age 18 (M 2.3±9.7 vs F -3.9±4.5 ΔmL/m², p≤0.01). LV EDVi remained above adult upper reference values in both groups. Males increased LV Mass Index from age 12 to 18 (M 33±27 vs F 4±19, Δg/m², p≤0.01). Males displayed LV mass above paediatric reference values at ages 15 and 18. A subset of males (35%) and females (25%) displayed wall thickness above paediatric reference values at age 12. Cardiac function was normal. There was no sex difference in exercise hours.

CONCLUSION

Sex-related differences in athlete's heart were evident from age 12, and progressed throughout adolescence. Remodelling beyond reference values was more frequent than previously reported, particularly affecting males. Age, sex and exercise history may assist clinicians in distinguishing exercise-induced remodelling from pathology in adolescents.

Guide to the Female Student Athlete ECG: A Comprehensive Study of 3466 Young, Racially Diverse Athletes

OBJECTIVES

The 12-lead electrocardiogram (ECG) is used in the preparticipation screening examination for athletes. Despite known differences in ECG findings by sex, only QTc prolongation is given a sex-specific threshold. We hypothesize that our large dataset-with diversity in age, race, and sport participation-can be utilized to improve ECG screening in female student athletes.

METHODS

Computerized 12-lead ECGs were recorded and analyzed in female athletes who underwent preparticipation screening examination between June 2010 and September 2021. The quantitative, empirical 2017 international criteria for electrocardiographic interpretation were compared with either the 99th percentile in our cohort or the percentile that corresponded to the known disease prevalence.

RESULTS

Of 3466 female athletes with ECGs as part of preparticipation screening examination, the 2017 international criteria classified 2.1% of athletes with at least one ECG abnormality requiring cardiological evaluation. Rates were similar across age, race/ethnicity, and sporting discipline. Using ranges based on our population, 2.7% of athletes would require additional workup. Surprisingly, ST depression up to 0.03 mV was a normal finding in this cohort. If RS voltage extremes were considered findings requiring follow-up, an additional 9.6% of the athlete population would be flagged using current definitions. This number decreases to 2.7% if using the 99th percentile in this cohort.

CONCLUSION

These results highlight a difference in the reported prevalence of ECG abnormalities when comparing empirically derived thresholds to statistically derived ranges. Consideration of new metrics specific to the female athlete population has the potential to further refine athlete ECG screening.

Soldiers' Heart: A Prospective Study of Cardiac Remodeling in Soldiers Undergoing Progressive Intensity Exercise Training

PURPOSE

Most studies reporting cardiac changes with exercise have been cross sectional. The few available longitudinal studies have lacked standardization for environmental confounders. We prospectively assessed the relationship between increasing exercise intensity and cardiac remodeling in a highly standardized cohort of healthy young army soldiers.

METHODS

Sixty-three male army recruits (22 ± 3 yr) underwent a 12-wk moderate-intensity mixed strength and endurance exercise program, followed by a further 15-wk high-intensity exercise program, with highly controlled exercise, diet, and sleep patterns. Fitness (multistage fitness test), anthropometry, and 2D echocardiography were assessed.

RESULTS

Moderate-intensity exercise was associated with increased fitness and decreased body fat % (both P < 0.01). There was no significant incremental change in these parameters after high-intensity exercise. By contrast, both moderate- and high-intensity exercises were associated with dose-dependent increases in left atrial and left ventricular (LV) volumes, LV mass, and right ventricular (RV) size (all P < 0.01). At the end of high-intensity training, 51% had a dilated LV and 59% had a dilated RV compared with published normal ranges. Almost all had normal LV systolic function and strain before and after exercise training. A small number of soldiers had mildly decreased RV systolic function at baseline and after moderate-intensity exercise (3% and 6%, respectively).

CONCLUSIONS

We describe "soldiers' heart," which is characterized by balanced chamber dilatation, normal LV mass, and largely normal systolic function and myocardial strain. This prospective and highly controlled longitudinal study also found that increasing intensity exercise was associated with increasing chamber dimensions, which paralleled an increase in fitness after moderate-intensity exercise. After high-intensity exercise, however, cardiac chamber size continued to increase, but fitness did not increase further.

Electrocardiographic phenotype of exercise-induced arrhythmogenic cardiomyopathy: A retrospective observational study

Introduction

The right ventricle can be susceptible to pathologic alterations with exercise. This can cause changes to the ECG. Our aim was to identify the electrocardiographic phenotype of exercise induced (ExI) arrhythmogenic cardiomyopathy (ACM).

Methods

A retrospective analysis of ECGs at rest, peak exercise and 1 min of recovery in four groups of individuals was performed: Arrhythmogenic Cardiomyopathy with genetic confirmation (Gen-ACM; n = 16), (genetically negative) ExI-ACM (n = 15), control endurance athletes (End; n = 16) and sedentary individuals (Sed; n = 16). The occurrence of ventricular arrhythmias (VA) and, at each stage, QRS duration, Terminal Activation Delay (TAD), the ratio of the sum of the QRS durations in the right precordials (V1-V3) over that in the left precordials (V4-V6; R/L duration ratio), the presence of complete RBBB and T-wave inversion (TWI) beyond lead V2 were evaluated.

Results

At rest, complete RBBB was exclusively found in Gen-ACM (6%) and ExI-ACM (13%). No epsilon waves were identified. TWI beyond V2 was uniquely present in Gen-ACM (73%) and ExI-ACM (38%; p < 0.001). VA was present in Gen-ACM (88%); ExI-ACM (80%), End (25%) and Sed (19%; p < 0.001). The presence of R/L duration ratio of >1.2 and TAD ≥ 55 ms were not significantly different over the four groups (p = 0.584 and p = 0.218, respectively). At peak exercise the most striking finding was a significant decrease of the R/L duration ratio in individuals with ACM, which was the result of lateral precordial QRS prolongation.

Conclusion

ExI-ACM shares important ECG-features with Gen-ACM, suggesting a similar underlying pathogenesis regardless of the presence or absence of desmosomal mutations.

Training intensity influences left ventricular dimensions in young competitive athletes

Background

In young athletes, exercise causes changes in the heart that include growth in wall thickness and mass of the left ventricle and expansion of the heart’s chambers. The heart’s function is either preserved or enhanced, but this may change to the opposite over time.

Objective

This study aimed to assess structural and functional cardiac adaptations in relation to exercise training time, intensity, and performance in young competitive athletes.

Methods

A total of 404 children and adolescents (14.23 ± 2.0 years, 97 females) were enrolled in the Munich Cardiovascular Adaptations in Young Athletes Study (MuCAYA-Study). Eighty-five participants were examined two times a year. Two-dimensional echocardiography was performed to assess left ventricular structure and function. Training time and intensity was measured with the MoMo physical activity questionnaire, maximum aerobic capacity by cardiopulmonary exercise testing, and strength with the handgrip strength test.

Results

Maximum aerobic capacity significantly influenced interventricular septal thickness in diastole. Training intensity significantly influenced left ventricular internal diameter in diastole and systole, and left ventricular mass indexed to body surface area. Within one year, interventricular wall thickness, relative wall thickness and left ventricular mass, indexed to body surface area and height, increased significantly. Training intensity and aerobic capacity contributed to cardiac adaptations in young competitive athletes, as represented by altered structural parameters but preserved cardiac function. Within a year, however, structural changes and a decline in diastolic performance were observed within the longitudinal sub-sample.

Conclusion

Our results confirm the hypothesis that cardiac adaptations to exercise occur at a young age. Cardiac adaptation in our cohort was influenced by exercise intensity and maximum aerobic capacity.

Cardiac Remodeling in Elite Aquatic Sport Athletes

OBJECTIVE

To characterize and compare the sport-specific cardiac structure of elite swimmers (SW), water polo players (WP), and artistic swimmers (AS).

DESIGN

A cross-sectional assessment of elite aquatic athletes' hearts.

SETTING

The athletes' village at the 2019 FINA World Championships.

PARTICIPANTS

Ninety athletes from swimming (SW) (20 M/17 F), water polo (WP) (21 M/9 F), and artistic swimming (AS) (23 F).

ASSESSMENT AND MAIN OUTCOME MEASURES

An echocardiographic assessment of cardiac structure was performed on noncompetition days.

RESULTS

Male SW displayed primarily eccentric volume-driven remodeling, whereas male WP had a greater incidence of pressure-driven concentric geometry (SW = 5%, WP = 25%) with elevated relative wall-thickness (RWT) (SW = 0.35 ± 0.04, WP = 0.44 ± 0.08, P < 0.001). Female SW and WP hearts were similar with primarily eccentric-remodeling, but SW and WP had greater concentricity index than artistic swimmers (SW = 6.74 ± 1.45 g/(mL)2/3, WP = 6.80 ± 1.24 g/(mL)2/3, AS = 5.52 ± 1.08 g/(mL)2/3, P = 0.007). AS had normal geometry, but with increased posterior-wall specific RWT (SW = 0.32 ± 0.05, AS = 0.42 ± 0.11, P = 0.004) and greater left atrial area than SW (SW = 9.7 ± 0.9 cm2/m2, AS = 11.0 ± 1.1 cm2/m2, P = 0.003). All females had greater incidence of left ventricular (LV) posterior/septal wall-thickness ≥11 mm than typically reported (SW = 24%, WP = 11%, AS = 17%).

CONCLUSIONS

Male athletes presented classic sport-specific differentiation, with SW demonstrating primarily volume-driven eccentric remodelling, and WP with greater concentric geometry indicative of pressure-driven remodeling. Female SW and WP did not display this divergence, likely because of sex-differences in adaptation. AS had unique LV-specific adaptations suggesting elevated pressure under low-volume conditions. The overall incidence of elevated wall-thickness in female athletes may point to an aquatic specific pressure-stress.

Physiological Effects of Training in Elite German Winter Sport Athletes: Sport Specific Remodeling Determined Using Echocardiographic Data and CPET Performance Parameters

Nine ski mountaineering (Ski-Mo), ten Nordic-cross country (NCC), and twelve world elite biathlon (Bia) athletes were evaluated for cardiopulmonary exercise test (CPET) performance and pronounced echocardiographic physiological cardiac remodeling as a primary aim of our descriptive preliminary report. In this context, a multicenter retrospective analysis of two-dimensional echocardiographic data including speckle tracking of the left ventricle (LV-GLS) and CPET performance analysis was performed in 31 elite world winter sports athletes, which were obtained during the annual sports medicine examination between 2020 and 2021. The matched data of the elite winter sports athletes (14 women, 17 male athletes, age: 18–32 years) were compared for different CPET and echocardiographic parameters, anthropometric data, and sport-specific training schedules. Significant differences could be revealed for left atrial (LA) remodeling by LA volume index (LAVI, p = 0.0052), LV-GLS (p = 0.0003), and LV mass index (LV Mass index, p = 0.0078) between the participating disciplines. All participating athletes showed excellent performance data in the CPET analyses, whereby significant differences were revealed for highest maximum respiratory minute volume (VE _maximum) and the maximum oxygen pulse level across the participating athletes. This study on sport specific physiological demands in elite winter sport athletes provides new evidence that significant differences in CPET and cardiac remodeling of the left heart can be identified based on the individual athlete’s training schedule, frequency, and physique.

The Role of Interventional Irisin on Heart Molecular Physiology

Irisin, encoded by the FNDC5 (fibronectin type III domain containing 5) gene, is a novel myokine that has been implicated as an essential mediator of exercise benefits. Effects of irisin on heart physiology is still ambiguous. This study aimed to evaluate the impact of exogenous administration of irisin on heart physiology and the pharmacokinetic profile of pump-administered irisin. To do so, Sprague Dawley rats were implanted with an irisin-loaded osmotic pump (5 μg/kg/day) for 42 days, and other animals were administered with single bolus subcutaneous injections of irisin (5 µg/kg). Body weights and blood samples were collected weekly for 42 days for serum irisin quantification and histopathology. Clinical biochemistry analyses were performed. Heart mRNA expression was assessed in 26 selected genes. Chronic interventional exogenous irisin significantly reduced body weight without affecting the heart myocyte size and significantly reduced creatine kinase enzyme level. Blood CBC, serum biochemistry, and heart morphology were normal. Gene expression of FNCD5, Raf1, CPT1, IGF-1, and CALCIN, encoding for heart physiology, increased while PGC1, Nox4, and Mfn1 significantly decreased. Nevertheless, irisin increased the expression of cardioprotective genes and inhibited some genes that harm heart physiology. Administration of irisin promotes myocardial functions and could be translated into clinical settings after preclinical profiling.

Left ventricular function and mechanics in backs and forwards elite rugby union players

PURPOSE

The aim of the present study was to assess left ventricular (LV) morphological and regional functional adaptations in backs and forwards elite rugby union (RU) players.

METHODS

Thirty-nine elite male RU players and twenty sedentary controls have been examined using resting echocardiography. RU players were divided into two groups, forwards (n = 22) and backs (n = 17). Evaluations included tissue Doppler and 2D speckle tracking analysis to assess LV strains and twisting mechanics.

RESULTS

The elite RU players exhibited a LV remodeling characterized by an increase in LV mass indexed to body surface area (82.2 ± 13.2 vs. 99.9 ± 16.1 and 119.7 ± 13.4 g.m^-2, in controls, backs and forwards; P < 0.001). Compared to backs, forwards exhibited lower global longitudinal strain (19.9 ± 2.5 vs. 18.0 ± 1.6%; P < 0.05), lower early diastolic velocity (16.5 ± 1.8 vs. 15.0 ± 2.3 cm.s^-1; P < 0.05) and lower diastolic longitudinal strain rate (1.80 ± 0.34 vs. 1.54 ± 0.26 s^-1; P < 0.01), especially at the apex. LV twist and untwisting velocities were similar in RU players compared to controls, but with lower apical (-46.2 ± 22.1 vs. -28.2 ± 21.7 deg.s^-1; P < 0.01) and higher basal rotational velocities (33.9 ± 20.9 vs. 48.4 ± 20.7 deg.s^-1; P < 0.05).

CONCLUSION

RU players exhibited an increase in LV mass which was more pronounced in forwards. In forwards, LV global longitudinal strain was depressed, LV filling pressures were decreased and LV relaxation depressed at the apex.

Longitudinal Associations Between Cumulative Physical Activity and Change in Structure and Function of the Left Side of the Heart: The Tromsø Study 2007–2016

Background

Current knowledge about the relationship between physical activity (PA) and cardiac remodeling is mainly derived from cross-sectional studies of athletes, and there is a knowledge gap of this association in the general adult and elderly population. Therefore, we aimed to explore the longitudinal association between cumulative PA and change in cardiac structure and function in a general adult and elderly population.

Methods

This longitudinal study includes 594 participants from the sixth (Tromsø6, 2007–08) and seventh (Tromsø7, 2015–16) survey of the Tromsø Study. Cardiac structure and function were assessed by echocardiography at two time points, and PA was self-reported by questionnaire at both time points. PA volume was expressed as cumulative PA (Low, Moderate, and Hard) and the association with left atrial (LA) and left ventricular (LV) structure and function was assessed using ANCOVA.

Results

Overall, LA diameter index (LADi) increased significantly more in Hard compared to Moderate PA (+0.08 cm/m², 95% CI 0.01–0.15, p = 0.020) from Tromsø6 to Tromsø7. When stratified by sex or age, higher levels of cumulative PA were associated with increased LADi in males and in participants <65 years only. Indexed LV mass (LVMi) increased significantly more in Moderate than in Low PA (+3.9 g/m^2.7, 95% CI 0.23–7.57, p = 0.037). When stratified by sex or age, these changes in LVMi and indexed LV diameter (LVDi) were only significant in females. No significant associations were observed between cumulative PA and change in relative wall thickness, E/e' ratio, e' velocity, LV ejection fraction, and LADi/LVDi ratio.

Conclusion

Higher levels of cumulative PA were associated with increased LADi in males and participants <65 years, and with increased LVMi and LVDi in females. Despite cardiac chamber enlargement, the pump function of the heart did not change with higher levels of PA, and the atrioventricular ratio was unchanged. Our results indicate that cardiac chamber enlargement is a physiological response to PA.

Electrocardiographic characteristics of trained and untrained standardbred racehorses

Background

Long‐term exercise induces cardiac remodeling that potentially influences the electrical properties of the heart.

Hypothesis/objectives

We assessed whether training alters cardiac conduction in Standardbred racehorses.

Animals

Two hundred one trained and 52 untrained Standardbred horses.

Methods

Cross‐sectional study. Resting ECG recordings were analyzed to assess heart rate (HR) along with standard ECG parameters and for identification of atrial and ventricular arrhythmias. An electrophysiological study was performed in 13 horses assessing the effect of training on sinoatrial (SA) and atrioventricular (AV) nodal function by sinus node recovery time (SNRT) and His signal recordings. Age and sex adjustments were implemented in multiple and logistic regression models for comparison.

Results

Resting HR in beats per minute (bpm) was lower in trained vs untrained horses (mean, 30.8 ± 2.6 bpm vs 32.9 ± 4.2 bpm; P = .001). Trained horses more often displayed second‐degree atrioventricular block (2AVB; odds ratio, 2.59; P = .04). No difference in SNRT was found between groups (n = 13). Mean P‐A, A‐H, and H‐V intervals were 71 ± 20, 209 ± 41, and 134 ± 41 ms, respectively (n = 7). We did not detect a training effect on AV‐nodal conduction intervals. His signals were present in 1 horse during 2AVB with varying H‐V interval preceding a blocked beat.

Conclusions and Clinical Importance

We identified decreased HR and increased frequency of 2AVB in trained horses. In 5 of 7 horses, His signal recordings had variable H‐V intervals within each individual horse, providing novel insight into AV conduction in horses.

Contribution of Lean Mass Distribution on Aerobic Fitness and Performance in NCAA Division I Female Rowers

ABSTRACT

Haraldsdottir, K, Sanfilippo, J, Dawes, S, and Watson, A. Contribution of lean mass distribution on aerobic fitness and performance in NCAA division I female rowers. J Strength Cond Res XX(X): 000-000, 2022-The purpose of this study was to determine the relative influence of total lean body mass (LBM), body fat percentage (BF%), upper extremity lean mass (ULM), lower extremity lean mass (LLM), and trunk lean mass (TLM) on maximal aerobic capacity (V̇o2max) and time to exhaustion (Tmax) in female collegiate rowers. One hundred seven female collegiate rowers (aged 18-22 years) performed maximal progressive rowing ergometer testing to determine V̇o2max and Tmax. Body mass, LBM, BF%, ULM, LLM, and TLM were determined by using dual-energy x-ray absorptiometry. Separate multivariable linear regression models were performed to predict V̇o2max and Tmax by using LBM and BF% as predictors. In addition, separate linear regression models were used to predict V̇o2max and Tmax with ULM, LLM, and TLM as covariates. Subjects were aged 20 ± 3 years. V̇o2max was significantly predicted by LBM (r2 = 0.29, p < 0.001), but not BF% (r2 = 0.002, p = 0.79). Similarly, Tmax was significantly predicted by LBM (r2 = 0.25, p < 0.001), but not BF% (r2 = 0.003, p = 0.19). V̇o2max was significantly predicted by LLM (r2 = 0.12, p < 0.01), but not ULM (r2 = 0.08, p = 0.68) or TLM (r2 = 0.09, p = 0.17), and Tmax was significantly predicted by TLM (r2 = 0.09, p = 0.02), but not ULM (r2 = 0.07, p = 0.89) or LLM (r2 = 0.08, p = 32). Among female collegiate rowers, whole body LBM is a significant predictor of both V̇o2max and Tmax. However, LLM is a stronger predictor of V̇o2max while TLM is a stronger predictor Tmax, although each of these relationships has a low coefficient of determination. These findings suggest that aerobic fitness and performance may be influenced by regions of lean mass differently.

When one says yes and the other says no; does calcineurin participate in physiologic cardiac hypertrophy?

Developing engaging activities that build skills for understanding and appreciating research is important for undergraduate and postgraduate science students. Comparing and contrasting opposing research studies does this, and more: it also appropriately for these cohorts challenges higher level cognitive processing. Here, we present and discuss one such scenario, that of calcineurin in the heart and its response to exercise training. This scenario is further accentuated by the existence of only two studies. The background is that regular aerobic endurance exercise training stimulates the heart to physiologically adapt to chronically increase its ability to produce a greater cardiac output to meet the increased demand for oxygenated blood in working muscles, and this happens by two main mechanisms: 1) increased cardiac contractile function and 2) physiologic hypertrophy. The major underlying mechanisms have been delineated over the last decades, but one aspect has not been resolved: the potential role of calcineurin in modulating physiologic hypertrophy. This is partly because the existing research has provided opposing and contrasting findings, one line showing that exercise training does activate cardiac calcineurin in conjunction with myocardial hypertrophy, but another line showing that exercise training does not activate cardiac calcineurin even if myocardial hypertrophy is blatantly occurring. Here, we review and present the current evidence in the field and discuss reasons for this controversy. We present real-life examples from physiology research and discuss how this may enhance student engagement and participation, widen the scope of learning, and thereby also further facilitate higher level cognitive processing.

Effect of regular endurance exercises on management of cardiovascular health in middle-aged men

This study was conducted to investigate the effect of regular endurance exercises on the management of cardiovascular health in middle-aged men. The following conclusions were drawn as the result of comparatively analyzing middle-aged men who regularly performed triathlon and cycling exercises for more than 5 years. The effect of regular endurance exercises on cardiovascular health management in middle-aged men was found to be relatively positive. However, prolonged endurance exercises can cause cardiovascular disease which can adversely affect the cardiac function, and to date, no defining limit is known about the amount of exercise that improves the cardiovascular function while reducing the cardiovascular events. Therefore, aiming for exercises at moderate intensity that befit the individual’s fitness level as well as conducting regular examinations to predict and manage the risk of sudden cardiac death from exercising were considered as the more effective method of cardiovascular health management.

Athlete’s Heart in Elite Biathlon, Nordic Cross—Country and Ski-Mountaineering Athletes: Cardiac Adaptions Determined Using Echocardiographic Data

Twelve world elite Biathlon (Bia), ten Nordic Cross Country (NCC) and ten ski-mountaineering (Ski-Mo) athletes were evaluated for pronounced echocardiographic physiological cardiac remodeling as a primary aim of our descriptive preliminary report. In this context, sports-related cardiac remodeling was analyzed by performing two-dimensional echocardiography including speckle tracking analysis as left ventricular global longitudinal strain (LV-GLS). A multicenter retrospective analysis of echocardiographic data was performed in 32 elite world winter sports athletes, which were obtained between 2020 and 2021 during the annual medical examination. The matched data of the elite world winter sports athletes (14 women, 18 male athletes, age: 18–35 years) were compared for different echocardiographic parameters. Significant differences could be revealed for left ventricular systolic function (LV-EF, p = 0.0001), left ventricular mass index (LV Mass index, p = 0.0078), left atrial remodeling by left atrial volume index (LAVI, p = 0.0052), and LV-GLS (p = 0.0003) between the three professional winter sports disciplines. This report provides new evidence that resting measures of cardiac structure and function in elite winter sport professionals can identify sport specific remodeling of the left heart, against the background of training schedule and training frequency.

The influence of maturation on exercise-induced cardiac remodelling and haematological adaptation

KEY POINTS

It has long been hypothesised that cardiovascular adaptation to endurance training is augmented following puberty. We investigated whether differences in cardiac and haematological variables exist, and to what extent, between endurance-trained vs. untrained, pre- and post-peak height velocity (PHV) children, and how these central factors relate to maximal oxygen consumption. Using echocardiography to quantify left ventricular (LV) morphology and carbon monoxide rebreathing to determine blood volume and haemoglobin mass, we identified that training-related differences in LV morphology are evident in pre-PHV children, with haematological differences also observed between pre-PHV girls. However, the breadth and magnitude of cardiovascular remodelling was more pronounced post-PHV. Cardiac and haematological measures provide significant predictive models for maximal oxygen consumption in children that are much stronger post-PHV, suggesting that other important determinants within the oxygen transport chain could account for the majority of variance in before puberty.

ABSTRACT

Cardiovascular and haematological adaptations to endurance training facilitate greater maximal oxygen consumption, and such adaptations maybe augmented following puberty. Therefore, we compared left ventricular (LV) morphology (echocardiography), blood volume, haemoglobin (Hb) mass (CO-rebreathe) and in endurance-trained and untrained boys (n = 42, age = 9.0-17.1 years, = 61.6±7.2 mL∙kg∙min, and n = 31, age = 8.0-17.7 years, O_2max = 46.5±6.1 mL∙kg∙min, respectively) and girls (n = 45, age = 8.2-17.0 years, O_2max = 51.4±5.7 mL∙kg∙min and n = 36, age = 8.0-17.6 years, O_2max = 39.8±5.7 mL∙kg∙min, respectively). Pubertal stage was estimated via maturity offset, with participants classified as pre- or post-peak height velocity (PHV). Pre-PHV, only a larger LV end-diastolic volume/lean body mass (EDV/LBM) for trained boys (+0.28 mL∙kg^LBM , P = 0.007) and a higher Hb mass/LBM for trained girls (+1.65 g∙kg^LBM , P = 0.007) were evident compared to untrained controls. Post-PHV, LV mass/LBM (boys:+0.50 g∙kg^LBM , P = 0.0003; girls:+0.35 g∙kg^LBM , P = 0.003), EDV/LBM (boys:+0.35 mL∙kg^LBM , P<0.0001; girls:+0.31 mL∙kgLBM, P = 0.0004), blood volume/LBM (boys:+12.47 mL∙kg^LBM , P = 0.004; girls:+13.48 mL∙kg^LBM , P = 0.0002.) and Hb mass/LBM (boys:+1.29 g∙kg^LBM , P = 0.015; girls:+1.47 g∙kg^LBM , P = 0.002) were all greater in trained vs. untrained groups. Pre-PHV, EDV (R² _adj = 0.224, P = 0.001) in boys, and Hb mass and interventricular septal thickness (R² _adj = 0.317, P = 0.002) in girls partially accounted for the variance in O_2max . Post-PHV, stronger predictive models were evident via the inclusion of LV wall thickness and EDV in boys (R² _adj = 0.608, P<0.0001), and posterior wall thickness and Hb mass in girls (R² _adj = 0.490, P<0.0001). In conclusion, cardiovascular adaptation to exercise training is more pronounced post-PHV, with evidence for a greater role of central components for oxygen delivery. Abstract figure legend: Schematic diagram depicting cardiac structural and haematological differences between trained and untrained boys and girls, pre-peak height velocity (PHV) and post-PHV alongside cardiac and haematological variables contributions to the variance in O_2max . Cardiac and haematological variables are greater in trained vs. untrained pre-pubertal children, and a greater number and magnitude of differences are observed at post-PHV. These variables provide significant predictive models for maximal oxygen consumption in children and are much stronger post-PHV, suggesting that other important determinants within the oxygen transport chain could account for the majority of variance in O_2max before puberty. This article is protected by copyright. All rights reserved.

Aortic Root Dimensions and Pulse Wave Velocity in Young Competitive Athletes

The assessment of aortic root dimensions is a cornerstone in cardiac pre-participation screening as dilation can result in severe cardiac events. Moreover, it can be a hint for an underlying connective tissue disease, which needs individualized sports counseling. This study examines the prevalence of aortic root dilatation in a cohort and its relationship to arterial stiffness as an early marker of cardiovascular risk due to vascular aging. From May 2012 to March 2018, we examined 281 young male athletes (14.7 ± 2.1 years) for their aortic root dimension. Moreover, we noninvasively assessed arterial stiffness parameter during pre-participation screening. Mean aortic diameter was 25.9 ± 3.1 mm and 18 of the 281 (6.4%) athletes had aortic root dilation without other clinical evidence of connective tissue disease. After adjusting for BSA, there was no association of aortic root diameter to pulse wave velocity (p = −0.054 r = 0.368) nor to central blood pressure (p = −0.029 r = 0.634). Thus, although a significant proportion of young athletes had aortic root dilatation, which certainly needs regular follow up, no correlation with arterial stiffness was found. It could be suggested that a dilated aortic root in young athletes does not alter pulse waveform and pulse reflection, and thus there is no increased cardiovascular risk in those subjects.

Circulating microRNAs fluctuations in exercise-induced cardiac remodeling: A systematic review

MicroRNAs (miRNAs) are small non-coding RNAs that participate in gene expression regulation. It has been observed that circulating levels of miRNAs may fluctuate during exercise, showing numerous cardiac biological and physiological effects such as structural and functional adaptations. We aimed to provide an overview of the currently available information concerning the role of circulating miRNAs in cardiovascular adaptations in response to acute and/or chronic exercise training. Relevant studies published were searched in three databases: PubMed, Web of Science and Scopus. A combination of the following keywords was used: ("microRNA" OR "miRNA" OR "miR" AND "exercise" OR "training" OR "physical activity") AND "(heart hypertrophy" OR "cardiac remodeling" OR "cardiac muscle mass" OR "cardiac hypertrophy"). Only experimental studies, written in English and conducted in healthy individuals were included. Five articles met the inclusion criteria and were finally included in this systematic review after reviewing both title, abstract and full-text. A total of thirty-six circulating cardiac-related miRNAs were analyzed, but only five of them (miR-1, miR-133a, miR-146a, miR-206 and miR-221) were directly associated with cardiac adaptations parameters, while two of them (miR-1 and miR-133a) were related to cardiac hypertrophy. Most of them were upregulated immediately after a marathon and returned to basal levels at longer times. Therefore, we conclude that, although evidence is still limited, and long-term studies are needed to obtain more robust evidence, exercise is more likely to affect circulating cardiac-related miRNAs levels.

Aerobic Exercise Attenuates Pressure Overload-Induced Cardiac Dysfunction through Promoting Skeletal Muscle Microcirculation and Increasing Muscle Mass

Background

Aerobic exercise has been proven to have a positive effect on cardiac function after hypertension; however, the mechanism is not entirely clarified. Skeletal muscle mass and microcirculation are closely associated with blood pressure and cardiac function.

Objective

This study was designed to investigate the effects of aerobic exercise on the skeletal muscle capillary and muscle mass, to explore the possible mechanisms involved in exercise-induced mitigation of cardiac dysfunction in pressure overload mice.

Methods

In this study, 60 BALB/C mice aged 8 weeks were randomly divided into 3 groups: control (CON), TAC, and TAC plus exercise (TAE) group and utilized transverse aortic constriction (TAC) to establish hypertensive model; meanwhile, treadmill training is used for aerobic exercise. After 5 days of recovery, mice in the TAE group were subjected to 10-week aerobic exercise. Carotid pressure and cardiac function were examined before mice were executed by Millar catheter and ultrasound, respectively. Muscle mass of gastrocnemius was weighed; cross-sectional area and the number of capillaries of gastrocnemius were detected by HE and immunohistochemistry, respectively. The mRNA and protein levels of VEGF in skeletal muscle were determined by RT-PCR and western blot, respectively.

Results

We found that ① 10-week aerobic exercise counteracted hypertension and attenuated cardiac dysfunction in TAC-induced hypertensive mice; ② TAC decreased muscle mass of gastrocnemius and resulted in muscle atrophy, while 10-week aerobic exercise could reserve transverse aortic constriction-induced the decline of muscle mass and muscle atrophy; and ③ TAC reduced the number of capillaries and the protein level of VEGF in gastrocnemius, whereas 10-week aerobic exercise augmented the number of capillaries, the mRNA and protein levels of VEGF in mice were subjected to TAC surgery.

Conclusions

This study indicates that 10-week aerobic exercise might fulfill its blood pressure-lowering effect via improving skeletal muscle microcirculation and increasing muscle mass.

mTOR signaling-related microRNAs as cardiac hypertrophy modulators in high-volume endurance training

Aerobic exercise training (ET) promotes cardiovascular adaptations, including physiological left ventricular hypertrophy (LVH). However, the molecular mechanisms that underlying these changes are unclear. The study aimed to elucidate specific miRNAs and target genes involved with the Akt/mTOR signaling in high-volume ET-induced LVH. Eight-week-old female Wistar rats were assigned to three groups: sedentary control (SC), trained protocol 1 (P1), and trained protocol 2 (P2). P1 consisted of 60 minutes/day of swimming, 5x/week, for 10 weeks. P2 consisted of the same protocol as P1 until the 8^th week; in the 9^th week, rats trained 2x/day, and in the 10^th week, trained 3x/day. Subsequently, structure and molecular parameters were evaluated in the heart. Trained groups demonstrate higher values to VO₂ peak, exercise tolerance, and LVH in a volume-dependent manner. The miRNA-26a-5p levels were higher in P1 and P2 compared to SC group (150±15%, d=1.8; 148±16%, d=1.7; and 100±7%, respectively, P < 0.05). In contrast, miRNA-16-5p levels were lower in P1 and P2 compared to SC group (69±5%, d=2.3, P < 0.01; 37±4%, d=5.6, P < 0.001 and 100±6%, respectively). Additionally, miRNA-16-5p knockdown and miRNA-26a-5p overexpression significantly promoted cardiomyocyte hypertrophy in neonatal rat cardiomyocytes. Both miRNAs were selected, using Diana Tolls bioinformatics website, for acting in the mTOR signaling pathway. The protein expression of Akt, mTOR, p70^S6k, and 4E-BP1 were greater in P1 and even more pronounced in P2. Nonetheless, GSK3β protein expression was lower in trained groups. Together, these molecular changes may contribute to a pronounced physiological LVH observed in high-volume aerobic training.

Differences in Left Ventricular Function at Rest and during Isometric Handgrip Exercise in Elite Aquatic Sport Athletes

PURPOSE

Elite swimmers (Sw) have lower diastolic function compared to elite runners, possibly as an adaptation to the aquatic training environment. Water polo players (WP) and artistic swimmers (AS) are exposed to the same hydrostatic pressures as Sw, but are subject to different training intensities, postures, and hemodynamic stressors. Our purpose was to compare resting and exercising cardiac function in elite Sw, WP, and AS, to characterize the influence of training for aquatic-sport on left ventricular (LV) adaptation.

METHODS

Ninety athletes (Sw:20 M/17F; WP:21 M/9F; AS:23F) at the 2019 FINA World Championships volunteered for resting and stress (3 min 30% maximal isometric handgrip) echocardiographic assessment of LV global function and mechanics.

RESULTS

Male Sw displayed greater resting systolic and diastolic function compared to WP; however, both groups maintained stroke volume under high-pressure handgrip stress (Sw:[INCREMENT]-4 ± 12%; WP:[INCREMENT]-1 ± 13%, P = 0.11). There were no differences between female Sw and WP resting LV function, but Sw demonstrated greater function over AS. During isometric handgrip, all female sport athletes maintained stroke volume (Sw:[INCREMENT]3 ± 16%; WP:[INCREMENT]-10 ± 11%; AS:[INCREMENT]-2 ± 14%, P = 0.46), but WP had improved apical rotation ([INCREMENT]1.7 ± 4.5°), which was reduced in AS ([INCREMENT]-3.1 ± 4.5°) and maintained in Sw ([INCREMENT]-0.5 ± 3.8°, P = 0.04). Unlike Sw and WP, AS displayed a unique maintenance of early filling velocity during handgrip exercise (Sw:[INCREMENT]-3.5 ± 14.7 cm/s; WP:[INCREMENT]-15.1 ± 10.8 cm/s; AS:[INCREMENT]1.5 ± 15.3 cm/s, P = 0.02).

CONCLUSION

Among male athletes, Sw display primarily volume-based functional adaptations distinct from the mixed volume-pressure adaptations of WP; however, both groups can maintain stroke volume with increased afterload. Female Sw and WP do not demonstrate sport-specific differences like males, perhaps owing to sex-differences in adaptation, but have greater volume-based adaptations than AS. Lastly, AS display unique functional adaptations, that may be driven by elevated pressures under low-volume conditions.

Left ventricular remodeling in rugby is a physiological adaptation to exercise: a pilot study conducted with high-level athletes

Purpose

Literature examining left ventricular (LV) structural adaptations to combined strength and endurance training is inconsistent. Rugby is a sport that combines these two exercise modalities, both during training and match play. This study aimed to explore differences in LV structure between high-level rugby players and untrained controls. Body composition analysis was performed to determine the most appropriate indexing variable for LV mass (LVM) and understand if increases in LV represent either a training-related physiological adaptation or reflect the groups’ anthropometric differences.

Methods

A cross-sectional design compared 10 rugby players and 10 untrained age-matched, male controls. Body composition was obtained by bioelectrical impedance. M-mode echocardiographic imaging was performed on the LV from the parasternal long axis view.

Results

Significantly greater end-diastolic interventricular septum, LV internal diameter, posterior wall thickness, LVM and LVM/fat-free mass (FFM) (p < 0.05) were found in rugby players compared to age-matched controls. Moreover, Pearson’s correlation tests revealed FFM to be the body composition variable with the strongest correlation to LVM (r = 0.775, p < 0.001).

Conclusion

The differences in LV structure between groups suggest that the combined endurance and strength training that rugby athletes are subjected to, induce a process of concentric and eccentric enlargement of the LV structure. Furthermore, the association found with FFM, suggests it to be the most appropriate body scaling variable to index to LVM and, thus, should be considered when describing increases in LVM. The present research suggests that increased LVM in the athletes group represents true physiological adaptations to training.

Absence of cardiac damage induced by long-term intensive endurance exercise training: A cardiac magnetic resonance and exercise echocardiography analysis in masters athletes

•

Endurance long-term high level of training induces significant cardiac remodelling involving all cardiac chambers, also known as ‘athletes-heart”.

•

Both left and right ventricular longitudinal strain increases significantly at exercise.

•

Cardiac extracellular volume is normal in master athletes and there is no evidence of cardiac fibrosis induced by long term endurance training in master athletes.

•

There is no evidence of cardiac damage induced by intensive endurance training in healthy asymptomatic master athletes.

Objectives

It is under debate whether the long-term practice of intensive endurance exercise induces chronic cardiac damage such as myocardial fibrosis and ventricle contractile dysfunction. Multimodality analysis was performed to evaluate myocardial damage induced by long term intensive endurance training in master athletes.

Methods

Thirty-three asymptomatic endurance master athletes (47 ± 6 year-old, 9,6 ± 1,7 h training/week for 26 ± 6 years), were compared to 18 sedentary controls (49 ± 7 year-old). They underwent a CMR protocol including 4 chambers morphological and late gadolinium-enhancement (LGE) analysis, left (LV) and right ventricular (RV) T1 mapping and calculation of cardiac extracellular volume (ECV). A maximal exercise echocardiography with left and right ventricular longitudinal global strain (LGS) analysis was performed. Cardiac biomarkers of fibrosis (high sensitive cardiac Troponin T, N-Terminal pro brain natriuretic peptide, N-terminal propeptide of procollagen type I and N-terminal propeptide of procollagen type III) were analysed.

Results

Athletes had larger left and right atrial volume, LV and RV end diastolic volume and increased LV and RV mass compared to controls. LGE was not found in athletes. Native T1 values of LV and RV were not significantly different in athletes compared with controls. ECV was normal in both groups (21,5%± 1,6% [18.3 – 23%] in athletes, 22%± 2,2% [18.5 – 27%] in controls). LV and RV peak exercise LGS values were higher in athletes. Cardiac biomarkers levels were normal.

Conclusion

Despite significant physiological cardiac remodelling, consistent with previous descriptions of athlete's heart, there was no evidence of myocardial fibrosis or exercise left or right ventricular dysfunction or cardiac fibrosis in endurance athletes. Our results are not supporting the hypothesis of deleterious cardiac effects induced by long term and intensive endurance exercise training.

Multiscale simulations of left ventricular growth and remodeling

Cardiomyocytes can adapt their size, shape, and orientation in response to altered biomechanical or biochemical stimuli. The process by which the heart undergoes structural changes-affecting both geometry and material properties-in response to altered ventricular loading, altered hormonal levels, or mutant sarcomeric proteins is broadly known as cardiac growth and remodeling (G&R). Although it is likely that cardiac G&R initially occurs as an adaptive response of the heart to the underlying stimuli, prolonged pathological changes can lead to increased risk of atrial fibrillation, heart failure, and sudden death. During the past few decades, computational models have been extensively used to investigate the mechanisms of cardiac G&R, as a complement to experimental measurements. These models have provided an opportunity to quantitatively study the relationships between the underlying stimuli (primarily mechanical) and the adverse outcomes of cardiac G&R, i.e., alterations in ventricular size and function. State-of-the-art computational models have shown promise in predicting the progression of cardiac G&R. However, there are still limitations that need to be addressed in future works to advance the field. In this review, we first outline the current state of computational models of cardiac growth and myofiber remodeling. Then, we discuss the potential limitations of current models of cardiac G&R that need to be addressed before they can be utilized in clinical care. Finally, we briefly discuss the next feasible steps and future directions that could advance the field of cardiac G&R.

The effects of activity, body weight, sex and age on echocardiographic values in English setter dogs

BACKGROUND

Breed-specific reference intervals improve echocardiographic interpretation and thereby reduce misdiagnoses, especially in athletic breeds.

OBJECTIVES

The objectives of the study were to examine transthoracic echocardiographic values in healthy adult English setter dogs and determine the effects of activity, body weight, sex and age on these values.

ANIMALS, MATERIALS AND METHODS

One hundred and one adult English setter dogs, recruited from local veterinary clinics and from the Norwegian English setter club, underwent routine transthoracic echocardiography. The population was stratified into two groups based on the reported level of activity. The effects of activity level, body weight, sex and age on echocardiographic variables were examined. Results were compared with published data from other breeds and from a pre-existing species-wide allometric model.

RESULTS

Of the 100 dogs between 19 months and 10 years of age included in the study, 72 were reported as very active and 28 as less active. Echocardiographic intervals were calculated for body size-independent echocardiographic variables. The upper limits of the intervals for left-atrial-to-aortic ratios and normalised left ventricular volumes exceeded those of various, previously published studies of other breeds. Normalised left ventricular dimensions exceeded published allometric 95^th percentile upper reference values in 13% of dogs in diastole and 32% of dogs in systole. More active dogs had larger cardiac dimensions than less active dogs; however, the activity level did not predict echocardiographic variables when included in a multiple regression model.

CONCLUSIONS

The study provides breed specific transthoracic echocardiographic values for English setter dogs, thereby contributing to improve diagnostic assessment of cardiac health in this breed.

Potential role of an athlete-focused echocardiogram in sports eligibility

Sudden cardiac death (SCD) of an athlete is a rare but tragic event and sport activity might play a trigger role in athletes with underlying structural or electrical heart diseases. Preparticipation screenings (PPs) have been conceived for the potential to prevent SCD in young athletes by early identification of cardiac diseases. The European Society of Cardiology protocol for PPs includes history collection, physical examination and baseline electrocardiogram, while further examinations are reserved to individuals with abnormalities at first-line evaluation. Nevertheless, transthoracic echocardiography has been hypothesized to have a primary role in the PPs. This review aims to describe how to approach an athlete-focused echocardiogram, highlighting what is crucial to focus on for the different diseases (cardiomyopathies, valvulopathies, congenital heart disease, myocarditis and pericarditis) and when is needed to pay attention to overlap diagnostic zone ("grey zone") with the athlete's heart. Once properly tested, focused echocardiography by sports medicine physicians may become standard practice in larger screening practices, potentially available during first-line evaluation.

Endurance training-induced increase in muscle oxidative capacity without loss of muscle mass in younger and older resistance-trained men

While concurrent training is regularly used in older populations, the inverse relationship between fibre size and oxidative capacity suggests that endurance training in resistance-trained individuals may result in some loss of resistance training-induced gains in muscle mass, which may be more pronounced in older people. We investigated the impact of superimposed endurance training in younger (28.5 ± 4.8 years; n = 8) and older (67.5 ± 5.5 years; n = 7) highly resistance-trained men. Participants underwent a 10-week endurance cycling training programme consisting of five 6-min intervals at 75% max heart rate (HRmax) separated by 4-min intervals at 90% HRmax. The anatomical cross-sectional area (ACSA) of the thigh muscles, as determined with MRI, was 24% smaller in older compared to younger participants (p < 0.001). Although maximal oxygen consumption (VO₂max) was also lower in the older group (p < 0.001), VO₂max per kg body mass did not differ significantly between younger and older participants. Histological analyses of biopsies of the m. vastus lateralis showed that endurance training induced an increase in succinate dehydrogenase activity in both younger and older participants (p ≤ 0.043), and an increase in the number of capillaries around type I fibres (p = 0.017). The superimposed endurance training did not induce a significant decrease in thigh ACSA, fibre cross-sectional area, or knee extensor maximum voluntary isometric force. These observations indicate that adding endurance training to resistance training can lead to positive endurance-related adaptations without negative consequences for muscle size and strength in older and younger resistance-trained people.

A comprehensive electrocardiographic analysis for young athletes

ECG-based differences between athletes and sedentary adolescents are a frequently investigated subject in sports medicine. Especially, training-induced ECG variations are common in adult athletes and sustained training often leads to anatomical changes in the heart that can yield abnormalities in ECG. Therefore, ECG screening in athletes is important in diagnosis of cardiac problems of young athletes. The present work investigated the ECG characteristics of young athletes in terms of both gender and sedentary healthy young control group differences. Besides comparison between groups, analysis parameters were also investigated within the groups using correlation analysis. ECG characteristics were extracted using wavelet transform-based adaptive algorithms. Results showed that ECGs of athletes demonstrate differences related to gender and compared to young sedentary. Athletes had significantly lower heart rate; higher QTc, P, and T amplitudes; ST segment; and ST, QT, and RR intervals compared to control group (p < 0.05). Proposed new parameter, namely "scalogram" of each wave, was lower in male athletes compared to other groups (p < 0.05). Negative correlation between T wave amplitude and RR interval could be an indicator of long QT syndrome for male athletes. Furthermore, prolongation of QRS interval in athletes could be the underlying reason of changes in T wave amplitude. Findings of this study can propose indicators for understanding the possible diseases as well as help evaluate the sudden changes in athlete's heart.

Aging Athlete's Heart: An Echocardiographic Evaluation of Competitive Sprint- versus Endurance-Trained Master Athletes

BACKGROUND

Sports training triggers exercise-induced cardiac remodeling (EICR). Sprint- and endurance-trained master athletes are exposed to different hemodynamic stimuli accompanied by aging. The aim of this study was to compare EICR types in light of the Morganroth hypothesis, frequency of abnormalities, and relationships between cardiac traits and age.

METHODS

In this observational cross-sectional study, echocardiographic examinations were conducted in 143 sprint-trained (age range, 36-83 years) and 114 endurance-trained (age range, 38-85 years) competitive master athletes. Structural and functional characteristics were compared with population reference values, and EICR types were identified. Athletic groups were compared using t tests and χ² tests. Relationships with age were assessed using linear regression.

RESULTS

In the sprint group, 51.0% of athletes had normal cardiac geometry (nonhypertrophic heart), 4.2% had eccentric hypertrophy, 36.4% had concentric remodeling, and 8.4% had concentric hypertrophy. In their endurance-trained peers, these proportions were 22.8%, 16.7%, 36.8%, and 23.7%, respectively. Many athletes in both groups had structural abnormalities, as assessed using population norms (up to ~81% for septal thickness) but their resting cardiac function was normal. The relationships of structural and functional cardiac characteristics with age were mostly weak to moderate and did not differ between training modalities.

CONCLUSIONS

Even though many endurance- and sprint-oriented master athletes exceed population norms for cardiac structure, they do not go beyond the "gray zone" and preserve normal cardiac function. Therefore, physiologic adaptations, rather than pathologic abnormalities, are expected in aging but still active athletes. Inconsistent with the Morganroth hypothesis, EICR is shifted toward normal geometry in sprinters and toward concentric remodeling and hypertrophy in endurance runners. A better understanding of the mechanisms behind cardiac remodeling during aging is needed to adequately predict EICR types in master athletes.

Association of physical activity with stroke among long-term colorectal cancer survivors

PURPOSE

Cancer survivors are currently considered high-risk populations for cardiovascular disease. However, no studies have directly evaluated risks and benefits of physical activity for stroke among long-term colorectal cancer survivors.

METHODS

This large-scale observational cohort study used data from the Korean National Health Insurance Service database. Newly diagnosed colorectal cancer patients diagnosed between 2006 and 2013 who survived at least 5 years were studied. The primary outcome was stroke, including ischemic stroke and hemorrhage stroke. All patients were followed up to the date of stroke, death, or December 2018, whichever occurred earliest.

RESULTS

Of 20,674 colorectal cancer survivors with a median age of 64 years, stroke occurred in 601 patients (2.9%). Moderate-to-vigorous physical activity lowered stroke risk in 5-9 time/week group (adjusted hazard ratio [aHR], 0.72; 95% confidence interval [CI], 0.57-0.93; P=0.010), but not in ≥10 time/week group (aHR, 0.85; 95% CI, 0.62-1.17; P=0.327). Walking also lowered stroke risk in 4-5 time/week group (aHR, 0.75; 95% CI, 0.58-0.97; P=0.028), but not in ≥6 time/week group (aHR, 0.96; 95% CI, 0.78-1.18; P=0.707). In addition, benefits of physical activity were maximized when carried out both moderate-to-vigorous physical activity and walking with moderate frequency (aHR, 0.77; 95% CI, 0.60-0.97; P=0.027).

CONCLUSIONS

Moderate frequency of moderate-to-vigorous physical activity (5-9 time/week) and walking (4-5 time/week) significantly lowers the risk of stroke, whereas high-frequency physical activity reduces the benefits of physical activity.

IMPLICATIONS FOR CANCER SURVIVORS

Physical activity with moderate frequency is important in the prevention of stroke for long-term colorectal cancer survivors.

Resting Heart Rate Measurement in Elite Athletes during COVID-19 Lockdown: The Impact of Decreased Physical Activity

The purpose was to observe the effects of a four-week lockdown on the resting heart rate (RHR) and well-being perception of elite swimmers. Twenty elite swimmers performed RHR measurements upon waking in supine and standing positions. Baseline values and those measured after four weeks of lockdown were compared. Swimmers completed a questionnaire on their training volume and state of well-being. During the lockdown, swimmers reported a weekly mean physical activity of 10.4 ± 3.6 h (an estimated reduction of 254% compared to their usual training volume). After four weeks of lockdown, RHR in the supine position increased by more than two beats per minute (58.8 ± 8.2 vs. 56.5 ± 7.4 bpm, p < 0.05). In the standing position, RHR increased by almost 15 beats per minute (103.3 ± 13.2 vs. 88.4 ± 9.4 bpm, p < 0.0001). Fifty percent of these athletes expressed a decrease in well-being. These results underline that the lockdown circumstances induced a large reduction in parasympathetic activity in elite athletes, which was associated with a decrease in training volume. This increase in RHR may reflect that a highatly strenuous environment and maintaining a high level of physical activity in this population could be favorable to preserve physical and psychological health.

Plasma lipocalin-2/NGAL is stable over 12 weeks and is not modulated by exercise or dieting

Amongst other immune cells, neutrophils play a key role in systemic inflammation leading to cardiovascular disease and can release inflammatory factors, including lipocalin-2 (LCN2). LCN2 drives cardiac hypertrophy and plays a role in maladaptive remodelling of the heart and has been associated with renal injury. While lifestyle factors such as diet and exercise are known to attenuate low-grade inflammation, their ability to modulate plasma LCN2 levels is unknown. Forty-eight endurance athletes and 52 controls (18–55 years) underwent measurement for various cardiovascular health indicators, along with plasma LCN2 concentration. No significant difference in LCN2 concentration was seen between the two groups. LCN2 was a very weak predictor or absent from models describing blood pressures or predicting athlete status. In another cohort, 57 non-diabetic overweight or obese men and post-menopausal women who fulfilled Adult Treatment Panel III metabolic syndrome criteria were randomly allocated into either a control, modified Dietary Approaches to Stop Hypertension (DASH) diet, or DASH and exercise group. Pre- and post-intervention demographic, cardiovascular health indicators, and plasma LCN2 expression were measured in each individual. While BMI fell in intervention groups, LCN2 levels remained unchanged within and between all groups, as illustrated by strong correlations between LCN2 concentrations pre- and 12 weeks post-intervention (r = 0.743, P < 0.0001). This suggests that circulating LCN2 expression are stable over a period of at least 12 weeks and is not modifiable by diet and exercise.

Age- and Sex-Differences in Cardiac Characteristics Determined by Echocardiography in Masters Athletes

Background

Cardiac function and morphology are known to differ between men and women. Sex differences seen with echocardiography have not been studied systematically in masters athletes.

Purpose

To evaluate sex differences in cardiac structure, function and left ventricular (LV) systolic global longitudinal strain among masters athletes.

Methods

This cross-sectional study comprises of 163 masters athletes (M = 109, 60 ± 12 years; F = 55, 57 ± 12 years, range 36–91 years) who participated at the 23rd World Masters Athletics Championship held in Málaga, Spain. All athletes underwent state-of-the-art echocardiography including cardiac function, morphology, strain and hemodynamic assessment.

Results

Left ventricular mass was higher in male than in female athletes (174 ± 44 vs. 141 ± 36 g, p < 0.01) due to greater end-diastolic intraventricular septal, LV posterior wall and LV basal diameter. However, LV mass index did not differ between the groups. End-diastolic LV volume and right ventricular area, both indexed to body-surface-area, were greater in men than in women (52.8 ± 11.0 vs. 46.1 ± 8.5 ml/m², p < 0.01, 9.5 ± 2.4 vs. 8.1 ± 1.7 cm²/m², p < 0.01). In contrast, women had higher LV systolic global longitudinal strain (-20.2 ± 2.6 vs. -18.8 ± 2.6%, p < 0.01) and LV outflow tract flow velocity (75.1 ± 11.1 vs. 71.2 ± 11.1 cm/s, p = 0.04). Systolic and diastolic blood pressure, LV ejection fraction, and stroke volume index were not different between sexes.

Conclusion

Cardiac sex differences are present even among masters athletes. Lifelong exercise training does not appear to exasperate morphological difference to a point of cardiac risk or dysfunction in both male and female athletes.

Intense Endurance Exercise: A Potential Risk Factor in the Development of Heart Disease

Exercise is known to improve cardiac health; however, the upper limit of exercise is not as clear. High-intensity endurance exercise and its association with cardiac dysfunction are becoming more important as more people in the USA participate in endurance activity. Intensive endurance exercise is associated with heart disease. Peer-reviewed primary literature related to endurance exercise, cardiac remodelling, myocardial fibrosis, and arrhythmia was searched and selected from the PubMed Database to be reviewed. Increased cardiac remodelling, myocardial fibrosis, and arrhythmias were associated with increased endurance exercise in most instances. Clinically significant dysfunction from endurance exercise-induced cardiac remodelling and myocardial fibrosis is not certain. However, increased incidence of sinus node disease (SND) and atrial flutter in endurance athletes, even after deconditioning, seems to be most associated with endurance exercise. Cardiac remodelling, fibrosis, and arrhythmia were associated with cardiac dysfunction. All review articles in this study were limited by a low sample size since it was difficult to obtain a full record of previous endurance activity. The reversibility of cardiac changes needs to be further investigated and can be applied in the differential diagnosis of other cardiomyopathies. The interaction between performance-enhancing drugs and endurance exercise needs to be further studied to determine its action on cardiac health. Findings from these studies could contribute to exercise recommendations.

Changes in Short-Term and Ultra-Short Term Heart Rate, Respiratory Rate, and Time-Domain Heart Rate Variability Parameters during Sympathetic Nervous System Activity Stimulation in Elite Modern Pentathlonists-A Pilot Study

Monitoring of markers reflecting cardiac autonomic activity before and during stressful situations may be useful for identifying the physiological state of an athlete and may have medical or performance implications. The study aimed to determine group and individual changes in short-term (5 min) and ultra-short-term (1 min) heart rate (HR), respiratory rate (RespRate), and time-domain heart rate variability (HRV) parameters during sympathetic nervous system activity (SNSa) stimulation among professional endurance athletes. Electrocardiographic recordings were performed in stable measurement conditions (Baseline) and during SNSa stimulation via isometric handgrip in 12 elite modern pentathlonists. Significant increases in short-term HR and decreases in time-domain HRV parameters with no changes in RespRate were observed during SNSa stimulation. Significant differences were observed between Baseline (all minutes) and the last (i.e., 5th) minute of SNSa stimulation for ultra-short-term parameters. Analysis of intra-individual changes revealed some heterogeneity in responses. The study provides baseline responses of HR, RespRate, and time-domain HRV parameters to SNSa stimulation among elite pentathlonists, which may be useful for identifying abnormal responses among fatigued or injured (e.g., concussed) athletes. More attention to individual analysis seems to be necessary when assessing physiological responses to sympathetic stimuli in professional endurance athletes.

Female Athlete's Heart: Sex Effects on Electrical and Structural Remodeling

BACKGROUND

Most of our knowledge on training-induced cardiac remodeling is derived from men, with the paucity of data from women representing an important gap in knowledge. The aim of the study was to define the electrocardiographic and morphological features of female athlete's heart, with special attention to differences related to sex and sport.

METHODS

Seven hundred twenty Olympic athletes (360 females and 360 age- and sport-matched males, mean age: 23±5 years) were evaluated by clinical, resting, and exercise electrocardiography and echocardiography.

RESULTS

Anterior T-wave inversion was more common in females than males (P<0.05). Left ventricular (LV) wall thickness and LV mass were greater in men (P<0.001). Females had smaller absolute but greater indexed LV and right ventricular (RV) dimensions as compared to males. Most women had normal LV geometry (80.8%). A progressive increase in LV/RV dimensions was observed in women from those engaged in skill, power, to mixed and endurance disciplines, with the endurance ones demonstrating the greatest degree of RV dilatation. Women had a peculiar biventricular adaptation, with higher LV/RV (1.41±0.16 versus 1.36±0.15, P<0.0001) and lower RV inflow/outflow ratio (P<0.001), as compared to men.

CONCLUSIONS

Sex significantly affects cardiac remodeling in athletes, with females presenting a different electrical and structural remodeling. Women maintain a normal LV geometry, with relative larger increase of cavity dimensions compared with men. Type of sport has a relevant impact, with endurance athletes exhibiting the greatest degree of RV and LV dimensional remodeling. The present study confirms the need for a sex-based approach for interpreting the complex features of athlete's heart in women.

Comparative study of cardiorespiratory adaptations in elite basketball players of different age groups

BACKGROUND

Systematic training of basketball causes morphological cardiac and cardiorespiratory adaptations. Previous studies have mainly focused either on only cardiac or respiratory changes. However, the extent of these cardiac adaptations and their relationship with aerobic capacity remain unclear in basketball athletes of different ages.

METHODS

Eighty male basketball players participated in the experimental group and 80 healthy and sedentary male individuals served as controls. All participants underwent to athletic history, anthropometric measurements, 12-lead resting electrocardiogram (ECG), echocardiography, resting spirometry and cardiopulmonary exercise stress test.

RESULTS

Left ventricular mass (LVM), left ventricular mass index (LVMI), left ventricular end-diastolic internal dimension (LVIDd), end-diastolic volume (EDV), stroke volume (SV) and interventricular septal thickness at diastole (IVSd) were significantly higher in all groups of athletes compared to controls (P<0.05). End-diastolic volume index (EDVI) was significantly higher only in adult players compared to controls (P<0.05). Posterior wall thickness at diastole (PWd) was significantly greater in groups of children and adult players compared to controls (P<0.05). Maximal oxygen uptake (V̇O<inf>2max</inf>) in relative values was higher in all groups of athletes compared to controls (P<0.05).

CONCLUSIONS

The increased LVM is attributed to concentric hypertrophy. This is further supported by the finding that there was no relationship between V̇O<inf>2max</inf> and echo parameters. The results of the present study indicate that the cardiorespiratory adaptations caused by basketball training are mainly formed at the early age stages without further increase throughout the years of action.

ECG Restitution Analysis and Machine Learning to Detect Paroxysmal Atrial Fibrillation: Insight from the Equine Athlete as a Model for Human Athletes

Atrial fibrillation is the most frequent arrhythmia in both equine and human athletes. Currently, this condition is diagnosed via electrocardiogram (ECG) monitoring which lacks sensitivity in about half of cases when it presents in paroxysmal form. We investigated whether the arrhythmogenic substrate present between the episodes of paroxysmal atrial fibrillation (PAF) can be detected using restitution analysis of normal sinus-rhythm ECGs. In this work, ECG recordings were obtained during routine clinical work from control and horses with PAF. The extracted QT, TQ, and RR intervals were used for ECG restitution analysis. The restitution data were trained and tested using k-nearest neighbor (k-NN) algorithm with various values of neighbors k to derive a discrimination tool. A combination of QT, RR, and TQ intervals was used to analyze the relationship between these intervals and their effects on PAF. A simple majority vote on individual record (one beat) classifications was used to determine the final classification. The k-NN classifiers using two-interval measures were able to predict the diagnosis of PAF with area under the receiving operating characteristic curve close to 0.8 (RR, TQ with k ≥ 9) and 0.9 (RR, QT with k ≥ 21 or TQ, QT with k ≥ 25). By simultaneously using all three intervals for each beat and a majority vote, mean area under the curves of 0.9 were obtained for all tested k-values (3-41). We concluded that 3D ECG restitution analysis can potentially be used as a metric of an automated method for screening of PAF.