By William W Russell, MD; Joseph Rossano, MD; Stephen Paridon, MD; Paul Stephens, MD; Julie A. Brothers, MD; Chandra Srinivasan, MD; and Jonathan Edelson, MD 

Abstract 

Background: Pediatric athletes with tachycardia and ventricular dysfunction are often assumed to have dilated cardiomyopathy or myocarditis, but a broad differential should be maintained.

Case summary: An 18-year-old competitive athlete presents to the emergency room with tachycardia and chest pain. ECG was thought to show high right atrial tachycardia consistent with sinus tachycardia, and echocardiogram demonstrated diminished left ventricular systolic function without dilation. Viral myocarditis and cardiomyopathy genetic testing were negative. Further observation and workup demonstrated ectopic atrial tachycardia, which was treated and the patient returned to sports. 

Discussion: Tachycardia-induced cardiomyopathy (TIC) is a rare, but reversible, cause of tachycardia and ventricular dysfunction. Exercise stress test can be useful in risk stratification. If returning to sport activity, an emergency action plan must be discussed with the patient and athletic training staff.

Take-home messages: TIC can be a subtle diagnosis but should not be missed, as this disease can be reversible with appropriate treatment.

History of presentation

The patient is a previously healthy 18-year-old competitive athlete with no past medical history who presented to the emergency room for tachycardia and chest pain with associated nausea and lightheadedness. Prior to his presentation to the emergency room, he was noted to have heart rates ranging from 120 to 200 bpm in a non-exertional setting. The heart rate in the emergency room was 120 bpm, and 12-lead electrocardiogram (ECG, Fig 1A) was of high right atrial origin, likely sinus tachycardia, thought to be secondary to hypovolemia. However, this tachycardia did not respond to fluid resuscitation, so cardiology was consulted and a transthoracic echocardiogram was obtained, demonstrating moderately diminished left ventricular (LV) systolic function. There were no wall motion abnormalities, troponin was normal and the LV size was within normal range (LVIDd 5.3cm, Z-Score -0.5). The patient was subsequently transferred to the Cardiology Center for additional evaluation.

Differential diagnosis

Initial differential diagnosis for this young athlete with LV systolic dysfunction and tachycardia included myocarditis, genetic dilated cardiomyopathy, coronary artery anomaly, hypertension-associated cardiomyopathy, tachycardia-induced cardiomyopathy, and hyperthyroidism.

Investigations

An infectious myocarditis workup, including adenovirus, cytomegalovirus, parvovirus and enterovirus, was negative. Troponin remained normal, as did labs measuring end organ function and brain naturietic peptide (BNP). Expedited exome sequencing was sent and found to be negative multiple weeks later. 

Management

The inappropriate nature of the patient’s tachycardia became apparent during the admission. The degree of tachycardia was out of proportion to his level of ventricular dysfunction and inconsistent with his compensated state. This raised the possibility of the high right atrial tachycardia (AT) to be ectopic AT from abnormal automaticity. Ivabradine and sacubitril/valsartan (Entresto) 24-26mg were started during the hospitalization. The patient began to show brief breaks from atrial tachycardia on ivabradine, with underlying sinus rhythm rates averaging 50-60 bpm.

Cardiac magnetic resonance imaging (CMR) was performed after starting on ivabradine and did not demonstrate edema or scarring, with an estimated left ventricular ejection fraction of 52% during sinus beats. The patient remained in the Cardiac Center for 6 days with intermittent runs of atrial tachycardia but was discharged with normal function in sinus rhythm.

Outcome and follow-up

Entresto was increased to 49-51mg BID at the patient’s first outpatient Sports Cardiology Clinic appointment. He continued to have recurrent breakthrough episodes of atrial tachycardia on a maximal dose of ivabradine. This led to intracardiac electrophysiology testing and mapping, which identified focal AT from the anterolateral aspect of the body of the right atrial appendage. Irrigated radiofrequency catheter ablation (CA) performed during this time achieved modification and attenuation of the arrhythmia substrate. He was started on nadolol and flecainide for interim control. Formal cardiopulmonary exercise testing was performed, following his first CA and found resting AT, which converted to sinus rhythm during exercise, thought to be a result of the modified arrhythmia substrate (Fig. 1B). Stress echocardiography did not demonstrate any wall motion abnormalities. 

Given his negative stress test and recovered ventricular systolic function on echocardiography, the patient was cleared to return to competitive athletics. He was brought in for a second attempt at CA, and mapping identified a focal AT from the medial aspect of the body of right atrial appendage. The arrhythmia focus was successfully eliminated using cryocatheter ablation. The most recent imaging studies demonstrate normal LV systolic function. The patient has remained asymptomatic while participating in high-intensity summer workouts with his team. 

Discussion

This case demonstrates the differential diagnosis of ventricular dysfunction and tachycardia and highlights the subtlety of tachycardia-induced cardiomyopathy (TIC). TIC is a chronic condition where persistent rapid heart rates can lead to ventricular dysfunction. TIC can easily be misdiagnosed as a primary dilated cardiomyopathy with resultant secondary arrhythmias or sinus tachycardia as a compensation for marginal cardiac output. TIC is rare but, as demonstrated in this case, reversible and therefore should always remain in the differential. Right atrial appendage tachycardia is more prevalent in young male patients and is commonly associated with TIC (1,2). This form of high right atrial tachycardia is known to masquerade as “sinus tachycardia” on a 12 lead ECG, and therefore a high index of suspicion is required. It is important to recognize the “inappropriate” nature of this tachycardia so that effective therapeutic decisions can be made. They can be resistant to catheter ablation attempts, requiring repeat attempts and use of alternative energy sources (3,4).

Formal exercise stress testing can be helpful for helpful for risk stratification after the diagnosis of TIC has been made. An arrhythmia that suppresses at higher heart rates can suggest a lower risk. This overdrive suppression of the arrhythmia is due to sympathetic stimulation and sinus node activation, which overtakes the slower ectopic atrial focus (5). 

As part of the shared decision-making (SDM) process, the Sports Cardiology team worked jointly with the patient’s athletic training staff and physicians. Discussions included the availability of an AED during all exercises, practices and games, as well as having a teammate, staff member or work-out partner assist in the event of an event.

Conclusions

This case study emphasizes the importance of having a broad differential diagnosis when evaluating a patient with tachycardia and ventricular dysfunction. While dilated cardiomyopathy with compensatory sinus tachycardia or myocarditis is more common, tachycardia-induced cardiomyopathy should remain on the differential. TIC can be reversible if diagnosed early. The patient with TIC can typically return to sports with SDM, especially if the patient has a lower risk arrhythmia that resolves with exercise. 

Take-home messages

• The differential for tachycardia and ventricular dysfunction should include tachycardia-induced cardiomyopathy.
• Tachycardia-induced cardiomyopathy is reversible if diagnosed and treated early.
• An exercise stress test can assess arrhythmia at rest and with exertion, which can help inform decisions on safe competitive sports participation.

References

1. Freixa X, Berruezo A, Mont L, et al. Characterization of focal right atrial appendage tachycardia. Europace. 2008;10(1):105-109. doi:10.1093/europace/eum264
2. Raja DC, Saravanan S, Sathishkumar AG, Pandurangi UM. Right atrial appendage tachycardia: A rare cause of tachycardia induced cardiomyopathy in a 4-year-old child. Indian Pacing Electrophysiol J. 2018;18(5):176-179. doi:10.1016/j.ipej.2018.07.001
3. Roshan J, Gizurarson S, Das M, Chauhan VS. Successful cryoablation of an incessant atrial tachycardia arising from the right atrial appendage. Indian Pacing Electrophysiol J. 2015;15(3):168-171. Published 2015 Sep 18. doi:10.1016/j.ipej.2015.09.005
4. Hai-Yang X, Zi-Cong F, Xiao-Gang G, Qi S, Jian-Du Y, Jian M. Treatment Strategy in Atrial Tachycardia Originating From the Atrial Appendage. Front Physiol. 2022;13:902513. Published 2022 Jun 24. doi:10.3389/fphys.2022.902513
5. Fletcher GF, Ades PA, Kligfield P, Arena R, Balady GJ, Bittner VA, Coke LA, Fleg JL, Forman DE, Gerber TC, Gulati M, Madan K, Rhodes J, Thompson PD, Williams MA; American Heart Association Exercise, Cardiac Rehabilitation, and Prevention Committee of the Council on Clinical Cardiology, Council on Nutrition, Physical Activity and Metabolism, Council on Cardiovascular and Stroke Nursing, and Council on Epidemiology and Prevention. Exercise standards for testing and training: a scientific statement from the American Heart Association. Circulation. 2013 Aug 20;128(8):873-934. doi: 10.1161/CIR.0b013e31829b5b44. Epub 2013 Jul 22. PMID: 23877260.