Working Diagnosis:
Paroxysmal Atrial Tachycardia, Non-Sustained Ventricular Tachycardia, Exertional Hypertension, Athlete's Heart Syndrome

Treatment:
Detraining was initiated, which involved keeping heart rate indefinitely below her anaerobic threshold. An angiotensin II receptor blocker, Losartan, was started for blood pressure control. A loop recorder was implanted for long-term monitoring of episodes of ventricular tachycardia and atrial fibrillation or tachycardia.

Outcome:
Detraining improved the frequency and duration of arrhythmias. In addition, on a repeat stress test, maximal blood pressure improved to 205/90. She decided to retire from competition and had no recurrence of arrhythmias on the loop recorder.

Author's Comments:
Research indicates that 30% of myocardial fibrosis seen in endurance athletes is secondary to exertional hypertension. This volume and pressure overload causes a repetitive cycle of wall strain, inflammation, and ultimately permanent fibrosis, particularly in the thinner-walled atria. The right side of the heart seems to be more susceptible in these athletes. Paradoxically, right-sided pathology in athletes has been far less studied. Acquired cardiomyopathies and arrhythmias likely result from long-term insult, as suggested by the increased incidence of atrial fibrillation with age in endurance athletes.

Editor's Comments:
While the benefits of exercise on cardiac health are well known, the negative impacts are less understood. Cardiac remodeling is a known sequela of endurance sports and allows for larger cardiac output during exercise. Adaptive cardiac remodeling with endurance sports includes such changes as eccentric left ventricular hypertrophy, biventricular dilation, and biatrial dilation. While adaptive for many, there appear to be potential adverse effects of remodeling, including cardiac fibrosis. Myocardial fibrosis is known to have several negative effects, including arrhythmia and sudden cardiac death. Myocardial fibrosis in athletes is heterogeneous, and it is not fully understood what predisposes certain athletes. Genetics, recurrent microtrauma, pressure overload, and silent myocarditis are all potential contributors. Additionally, both atrial fibrillation and atrial fibrosis are associated with high-intensity endurance training. It is proposed that fibrosis may contribute to the development of atrial fibrillation; however, this requires further study.

References:
Chandra N, Bastiaenen R, Papadakis M, Sharma S. Sudden cardiac death in young athletes: practical challenges and diagnostic dilemmas. J Am Coll Cardiol. 2013 Mar 12;61(10):1027-40.

Tahir E, Starekova J, Muellerleile K, von Stritzky A, Munch J, Avanesov M, Weinrich JM, Stehning C, Bohnen S, Radunski UK, Freiwald E, Blankenberg S, Adam G, Pressler A, Patten M, Lund GK. Myocardial Fibrosis in Competitive Triathletes Detected by Contrast-Enhanced CMR Correlates With Exercise-Induced Hypertension and Competition History. JACC Cardiovasc Imaging. 2018 Sep;11(9):1260-1270.

Gay-Jordi G, Guash E, Benito B, Brugada J, Nattel S, Mont L, Serrano-Mollar A. Losartan prevents heart fibrosis induced by long-term intensive exercise in an animal model. PLoS One. 2013;8(2):e55427.

Myrstad M, Lochen ML, Graff-Iversen S, Gulsvik AK, Thelle DS, Stigum H, Ranhoff AH. Increased risk of atrial fibrillation among elderly Norwegian men with a history of long-term endurance sport practice. Scand J Med Sci Sports. 2014 Aug;24(4):e238-44.

Elliott AD, La Gerche A. The right ventricle following prolonged endurance exercise: are we overlooking the more important side of the heart? A meta-analysis. Br J Sports Med. 2015 Jun;49(11):724-9.

van de Schoor FR, Aengevaeren VL, Hopman MT, Oxborough DL, George KP, Thompson PD, Eijsvogels TM. Myocardial Fibrosis in Athletes. Mayo Clin Proc. 2016 Nov;91(11):1617-1631.

Peritz DC, Catino AB, Csecs I, Kaur G, Kheirkhahan M, Loveless B, Wasmund S, Kholmovski E, Morris A, Marrouche NF. High-intensity endurance training is associated with left atrial fibrosis. Am Heart J. 2020 Aug;226:206-213.

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