ECG Quiz Answer: A Murmur in an Asymptomatic Athlete

Janus D. Butcher, MD

THE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 8 - AUGUST 97

Diagnosis

[FIGURE 2] The chest x-ray (figure 2) demonstrates moderate cardiomegaly with a cardiothoracic (CT) ratio of 0.59. ECG (figure 3) displays Q waves in leads V(1) through V(4), first degree heart block, and prominent P waves throughout, a pattern that is consistent with Ebstein's anomaly. A subsequent echocardiogram revealed a displaced tricuspid valve with a dilated right atrium and moderate tricuspid regurgitation. Twenty-four-hour Holter monitoring showed no aberrant rhythm. An exercise stress test was performed with the patient exercising 16 minutes on the Bruce protocol without evidence of arrhythmias, oxygen desaturation, ischemia, or symptoms suggesting cardiac decompensation.

Morphology and Natural History

Ebstein's anomaly is a congenital lesion of the tricuspid valve with relatively constant morphology (1). The septal and posterior leaflets are usually displaced distally, resulting in atrialization of the right ventricle. These leaflets are often dysplastic or adherent to the ventricle. The anterior leaflet is also dysfunctional and may be tethered to the ventricular wall, resulting in severe tricuspid regurgitation (2). Ebstein's anomaly has been associated quite frequently with corrected transpositions of the great vessels and rarely with tetralogy of Fallot and other valvular anomalies. Atrial septal defects are also common in patients with Ebstein's anomaly (1). Intrauterine exposure to lithium has been associated with the subsequent development of Ebstein's anomaly (1).

Ebstein's anomaly results in several rhythm disturbances, including atrial fibrillation, supraventricular tachycardia, ventricular tachycardia, and Wolff-Parkinson-White syndrome. Sudden death can occur in these patients and has been associated with exercise in relatively asymptomatic individuals (3).

[FIGURE 3] The natural history of Ebstein's anomaly varies depending on the severity of tricuspid dysfunction and associated atrial septal defects. Severe cases often result in intrauterine or neonatal death, while the mildest forms can remain asymptomatic through a normal life span (4).

Diagnosis is usually made in the neonatal period, although mild lesions may not be recognized until later in life (3). Patients with a mild case will often remain asymptomatic into middle adulthood, when gradual decompensation occurs with increasing dyspnea, fatigue, poor exercise tolerance, and in some cases syncope (2). A number of factors have been identified as predictors of death in these patients: male gender, breathlessness, a cardiothoracic ratio greater than 0.65, New York Heart Association functional class (NYHA-FC) III or IV, and atrial fibrillation (5).

Management

Patients with low-grade lesions (NYHA-FCI or II) are best managed medically with treatment of any associated arrhythmias. With clinical evidence of decompensation or with a CT ratio greater than 0.65 (even in the absence of symptoms), surgical therapy is usually indicated (6). Tricuspid annuloplasty is currently the procedure of choice when anatomically feasible. Prosthetic valve replacement remains another surgical option. Repair of concurrent atrial septal defects appears to be the most effective measure for improving exercise tolerance in patients with this lesion (6,7). New techniques of electrophysiologic mapping and accessory conduction pathway ablation may be useful in preventing fatal arrhythmias in these patients.

The approach to the athlete with Ebstein's anomaly involves careful evaluation of the structural defect and cardiac function. Echocardiography is the best imaging modality in Ebstein's anomaly. Graded exercise testing with continuous pulse oximetry is useful for evaluation of cardiac reserve. Careful evaluation of any arrhythmia with ECG and Holter monitoring is required. Therapy directed at preventing arrhythmias must be tailored to the individual athlete.

The 1994 Bethesda Conference guidelines for exercise in athletes with Ebstein's anomaly (8) recommend no restrictions for those with mild forms (near normal heart size, no cyanosis, and no arrhythmia). In more severe forms, or in individuals who have had surgical repair, noncompetitive low-intensity exercise (class IA, such as bowling, golf, billiards) is usually allowed.

The patient described here had an NYHA-FC I lesion and had maintained a remarkable exercise capacity with no objective evidence of cardiac decompensation. He had no history or current evidence of arrhythmias, so no medications were indicated at this time except antibiotics for endocarditis prophylaxis. He was advised to continue in his active occupation with no specific restrictions on his exercise. He was, however, denied clearance for the HALO training because of the potential for cardiovascular decompensation in a low-oxygen environment, which would result in an inability to perform HALO.

Future monitoring of this athlete will include annual ECG, chest x-ray, and physical exam. Annual echocardiography will also be done to monitor tricuspid valve function. If any historical evidence of cardiac decompensation develops, an exercise stress test with continuous pulse oximetry will be performed to evaluate cardiac reserve.

References

Anderson KR, Zuberbuhler JR, Anderson RH, et al: Morphologic spectrum of Ebstein's anomaly of the heart. Mayo Clin Proc 1979;54(3):174-180
Giuliani ER, Fuster V, Brandenburg RO, et al: Ebstein's anomaly: the clinical features and natural history of Ebstein's anomaly of the tricuspid valve. Mayo Clin Proc 1979;54(3):163-173
Tuzcu EM, Moodie DS, Ghazi F, et al: Ebstein's anomaly: natural and unnatural history. Clev Clin J Med 1989;56(6):614-618
Seward JB, Tajik AJ, Feist DJ, et al: Ebstein's anomaly in an 85-year-old man. Mayo Clin Proc 1979;54(3):193-196
Gentles TL, Calder AL, Clarkson PM, et al: Predictors of long-term survival with Ebstein's anomaly of the tricuspid valve. Am J Cardiol 1992;69(4):377-381
Mair DD: Management of Ebstein's anomaly. Clev Clin J Med 1989;56(6):626-627 [Published erratum appears in Clev Clin J Med 1989;56(8):848]
Driscoll DJ, Mottram CD, Danielson GK: Spectrum of exercise intolerance in 45 patients with Ebstein's anomaly and observations on exercise tolerance in 11 patients after surgical repair. J Am Coll Cardiol 1988;11(4):831-836
Graham TP Jr, Bricker JT, James FW, et al: Task Force 1: Congenital heart disease, in 26th Bethesda Conference: Recommendations for determining eligibility for competition in athletes with cardiovascular abnormalities. Med Sci Sports Exerc 1994;26(10 suppl):246-253

Dr Butcher is director of primary care sports medicine at Dwight D. Eisenhower Army Medical Center at Fort Gordon, Georgia, and a clinical assistant professor at Uniformed Services University of Health Sciences and the Medical College of Georgia in Augusta. Address correspondence to Janus D. Butcher, MD, Department of Family Practice, D.D. Eisenhower Army Medical Center, Ft Gordon, GA 30905.

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