Potential Associated Cardiovascular Controversies in Master Endurance Athletes

The cohort of master athletes (MA), defined people older than 35 years taking part in competitive sport events, is a rapidly growing population. This athlete cohort acquires adequate and sport-specific medical care. 
Although physical exercise has many positive effects on the cardiovascular system, high levels of endurance exercise are associated with numerous cardiovascular controversies. 
In this context, our case report would like to present an example of a MA with exercise-induced cardiac remodeling (EICR), who – at the initial diagnosis of paroxysmal supraventricular tachycardia – was extremely sensitive to bouts of atrial tachycardia (AT) and reported irregular palpitations during exercise and in the recovery period.

Key Words: Cardiac Remodeling, Athletes, Supraventricular Tachycardia, PAFIYAMA Syndrome, Arrhythmogenesis

We present the case of a forty-two old male endurance athlete who started to prepare for a half marathon with regular running training in the pre-season. He was six feet tall, 78 kg of weight (BMI 23,5 kg/m2) and his average level of training hours was 10 per week (including running and strength and stability training). He was performing an intermediate level half-marathon training in the last 10 years with long runs up to 21 km and an average weekly mileage of 25 to 40 km. The athlete´s individual V˙O2 maximum value estimation based on the Heart rate ratio method, described by Uth et al. in 2005, resulted in 51 ml/min/kg (13). The forty-two-year-old endurance athlete presented in our emergency department with newly occurring, previously unknown, cardiopulmonary symptoms during exercise and in the recovery phase, including intermittent shortness of breath and heart palpitations during running sessions and in the recovery period. His medical and family history did not reveal any cardiovascular events, and he did not take regularly medications. He did not report any history of cardiac complaints, particularly no episodes of chest pain or exercise-associated syncope. Written informed consent was obtained from the patient for publication of this case report and any accompanying images.

The initial electrocardiogram (ECG, figure 1) assessed in the emergency room showed a stable sinus rhythm with few supraventricular extrasystoles, but without any significant abnormalities according to the Seattle criteria nor any evidence of acute coronary syndrome (ACS). The laboratory parameters determined showed no relevant inflammatory constellation and no significant increase in the specific cardiac biomarkers, i.e. N-terminal pro b-type natriuretic peptide (NT-pro BNP) and especially the high-sensitivity troponin (hs TnT).
 The transthoracic echocardiographic data showed a mild enlargement of both atria (LA 22 cm2, left atrial; and RA 24 cm2, right atrial), a mild enlargement of the right ventricle (RV) with an enddiastolic diameter of 35 mm (RVedd) and preserved systolic function of the RV – TAPSE 27mm (Tricuspid annular plane systolic excursion) in the apical four chamber view. The calculated LA volume Index (LAVI) showed with 36 mL/m2 a mildly abnormal finding. We detected no relevant hypertrophia of the left ventricular walls (IVSd 11 mm, interventricular septum thickness at end-diastole; LVPWd 10 mm, left ventricular posterior wall end diastole; RWT 0.38, relative wall thickness) and the athlete displayed a preserved systolic ejection fraction (60%) of the left ventricle (LV) as well as normal diastolic function with E/E´ratio 6.7 accompanied by normal LV end-diastolic diameter (LVedd 52mm). No clinical relevant left and right heart valve regurgitations could be revealed, whereby the Tricuspide valve showed a mild regurgitation and an estimated right ventricular systolic pressure (RVSP) of 19 mmHg (figure 2).
In order to examine the patient more extensively, we decided to perform a stress ECG on a bicycle ergometer. During the test, the patient developed an episode of paroxysmal supraventricular tachycardia (SVT, maximum effort 250 watts) and we were able to record the exercise-related SVT episodes (figure 3). After finishing the ergometer stress testing, the patient recovered very fast and his heart rhythm returned to a stable sinus rhythm, similar to the pre-testing conditions without any SVT episodes.
Further cardiological diagnostics using cardio MRI showed no criteria for relevant stress ischemia in the stress test with regadenoson and no evidence of active or previous myocarditis or pericarditis. However, cardiac imaging showed evidence of sport-specific remodeling through mild biatrial dilation (RA 25 cm2, LA 26 cm2), and adaptation of the right ventricle to regular vigorous endurance training. Therefore, the RV parameters showed sport-specific remodeling with an indexed RV enddiastolic volume (RVEDV 100 ml/m2) and an indexed RV endsystolic volume (RVESV 50 ml/m2) accompanied by TAPSE 32mm. Additionally, the LV parameters displayed a normal indexed LV enddiastolic volume (LVEDV 95 ml/m2) and normal indexed LV endsystolic volume (LVESV 39 ml/m2) resulting in a LV stroke volume of 56ml/m2 and a cardiac index (CI) of 4.2 l/min/m2 (figure 4).

Paroxysmal supraventricular tachycardia in endurance athletes.
 

While the interest and participation in general endurance training and recreational sports competitions have been growing continuously during the last decades, the number of master level endurance athletes has additionally increased (12). Therefore, men and women older than 35 years participating in competitive athletics are referred to the term master athletes (MA) and represent a steadily growing population to which broad cardiological attention should be devoted (14).
Previous research revealed positive effects of regular and moderate physical activity due to cardiovascular health, but however, recent scientific studies also showed some increase in long-term effects regarding adverse cardiovascular outcomes due to regular endurance sport activity (12). In this context, the negative consequences and controversies regarding negative anatomical and functional cardiac remodeling are discussed, but also the increased risk of arrhythmogenesis, such as paroxysmal SVT and atrial fibrillation (AF) in MA during lifetime, as well as accompanying accelerated coronary artery arteriosclerosis (12). This process, named exercise-induced cardiac remodeling (EICR), shows a broad interindividual variability based on gender, ethnicity, sporting discipline and duration of exercise exposure (4, 14). For this reason, the prevalence of atrial ectopy and paroxysmal SVT– in our athlete´s case paroxysmal episodes of AT, might be interpreted as a potential predictor for enhanced arrhythmogenesis in MA and an increased risk of AF appearance during athlete´s lifetime career might be assumed. The incidence of atrial AF, representing the most common clinically relevant arrhythmia in general population, is higher in MA than in the general population and in gender-matched normally active people (2, 4, 6, 11). The highest risk appears to be in male athletes who participate in ambitious endurance sports (4, 6, 11). In this context, Newman et al. revealed in a systematic review and meta-analysis that younger athletes (<55 years) were more likely to develop AF than older athletes (OR: 3.60), whereby endurance and mixed sport activities presenting the highest risk of developing AF (8). D´Ambrosio et al. reported in a cross-sectional analysis of observational studies in endurance MA, older than 40 years, a prevalence of 32% of AF (5, 7). Additionally, register data assessment of 52755 Vasaloppet participants – a 90 km cross skiing event in Sweden – revealed an arrhythmogenesis prevalence of 1.5-2,0% overall participants (3, 7). The pathogenesis of AF in MA seems to be multifactorial and complex, whereby several influencing factors have been reported before, i.e. atrial remodeling including LA dilatation and fibrosis, enhanced vagal nerve activity in endurance athletes, but even overwhelming sympathetic nervous system activity during ambitious exercise, combined with chronic periodic inflammation, alcohol consumption and psychosocial stress (4, 5, 15). Therefore, the new onset of AF, named PAFIYAMA – paroxysmal AF in young and middle-aged athletes – has to be classified individually based on the specific athlete´s background (16, 17). In this context, latest research could not reveal any significant correlation between anatomical and functional LA assessment with AF prevalence and training load or lifetime training parameters (1, 7). Some MA report a decrement of performance or exercise capacity, otherwise - as in our athlete - MA are extremely sensitive to bouts of AT or paroxysmal AF episodes and report irregular palpitations during exercise and in the recovery period (4). By identification and subsequent optimization of modifiable risk factors, such as training load, blood pressure control during rest or in response to maximal effort, supplement use and alcohol consumption, in several MA a significant reduction or elimination of recurrent AF episodes can be achieved, obviating the need of specific additional AF treatment (4). In our specific case, we proposed our MA to adapt individual training load and optimize the previously mentioned modifiable risk factors. In detail, we recommended our athlete to avoid high-intensity anaerobic interval training and intensive competition participation, focus on baseline running and stability training, and to reduce the cumulative weekly training load from 10 to 6-7 hours. We additionally recommended potassium and magnesium supplementation after exclusion of clinical relevant electrolyte disorders to stabilize his heart rhythm. Furthermore, we recommended our athlete to use his smartwatch during maintaining sports activity for arrhythmia detection. According to the current ESC Sports Cardiology Guidelines, our athlete was instructed to stop exercise in the event of palpitations to avoid (pre)syncope and was educated how to safely perform vagal manoeuvres, such as Valsalva manoeuvre or carotis sinus massage, as we revealed no pre-excitation (9). A cardiological revaluation was scheduled in 3 months, including CPET.
In conjunction with risk factor modification, an individual athlete-related medical care and follow-up is necessary in order to discuss individual topics with the MA in the sense of shared decision making. These considerations include the individual initiation of oral anticoagulation in lone AF or paroxysmal SVT episodes, specific antiarrhythmic medication, or the planning of an invasive strategy such as pulmonary vein isolation (4, 16, 17). Nevertheless, moderate regular physical activity is a cornerstone in the prevention of paroxysmal SVT or AF, as it modifies many of its predisposing factors and might contribute to life expectancy extension compared to sedentary individuals. Therefore, the term “exercise is medicine” retains its validity (9).

In conclusion, MA represent a broad and increasingly growing cohort encountered in clinical cardiovascular practice. Therefore, sports cardiology expertise is necessary to provide individualized cardiological care and follow-up for athletes. Comprehensive treatment of MA requires consideration of multiple aspects that contribute to the prevention and treatment of paroxysmal SVT or AF episodes and to maintaining athlete´s performance. Future scientific effort will be necessary to better understand the various influencing pathophysiological components and to optimize sport specific medical care for these MA.

Conflict of Interest
The authors have no conflict of interest.

While presenting young, healthy patients with palpitations and high levels of physical activity, always consider sport-specific cardiac remodeling.
Exclusion of predisposing factors such as electrolyte disorders, endocrine causes, evaluation of dietary supplements and alcohol consumption. Strive for ECG documentation of cardiac arrhythmia.
Individual shared decision strategy – consider individual initiation of oral anticoagulation in lone AF and SVT, specific antiarrhythmic medication, or planning of an invasive strategy such as pulmonary vein isolation. Consider the use of wearables during sports activity for arrhythmia detection.