A young man with an unusual cause of palpitations

IS CARDIOVERSION NEEDED?

According to the American Heart Association guidelines for advanced cardiopulmonary life support, patients with tachyarrhythmias who are hemodynamically unstable should undergo cardioversion immediately.⁵

Our patient, who has a heart rate faster than 200 bpm and a systolic blood pressure of only 60 mm Hg, undergoes synchronized cardioversion in the emergency department. Immediately afterward, his ECG (Figure 4) demonstrates sinus rhythm with pre-excitation consistent with type B Wolff-Parkinson-White syndrome.

Once he is hemodynamically stable, a more thorough physical examination is performed. Examination of the head, ears, eyes, nose, and throat is unremarkable. He has no jugular venous distention or carotid bruits. His lungs are clear to auscultation bilaterally, without wheezes. His cardiac examination shows a regular rate and rhythm, normal first and second heart sounds, and no murmurs, rubs, or gallops.

WHICH DIAGNOSTIC STUDIES ARE NEEDED?

Laboratory tests

In an otherwise healthy young patient presenting with an arrhythmia, the initial laboratory workup should focus on a precipitating illness or a disease state that may incite an arrhythmia.

Our patient is evaluated for infection or septic shock (white blood cell count with differential), anemia (hemoglobin), thyrotoxicosis (thyroid-stimulating hormone and free thyroxine levels), drug abuse (urine toxicology screen), and cardiac syndromes including structural heart disease and myocardial injury (cardiac enzymes and B-type natriuretic peptide).⁶

His initial laboratory tests show normal electrolyte levels and renal function, leukocytosis with a white blood cell count of 15.6 × 10⁹/L (normal 4.0–10.0), mildly elevated thyroid-stimulating hormone, and a negative urine toxicology screen.

Transthoracic echocardiography

For a young patient presenting with pre-excitation on ECG and hemodynamic instability, transthoracic echocardiography to evaluate chamber size and look for structural abnormalities is a reasonable option.

Our patient undergoes transthoracic echocardiography, which demonstrates normal left ventricular size and function with a left ventricular ejection fraction of 69%, moderate right atrial enlargement, and mild right ventricular enlargement (Figure 5). The septal leaflet of the tricuspid valve is apically displaced, and there is mild regurgitation.

DIAGNOSIS: EBSTEIN ANOMALY

These findings are consistent with Ebstein anomaly. It can be recognized on transthoracic echocardiography as adherence of the septal and posterior tricuspid valve leaflets to the myocardium due to failure of the tissue to detach during embryogenesis, apical displacement of the annulus, right atrial enlargement, and right ventricular enlargement.^7–10 Apical displacement of the tricuspid valve is a hallmark finding and must be more than 20 mm or 8 mm/m² of body surface area to make the diagnosis.^11–13 ECG often demonstrates right atrial enlargement, first-degree atrial ventricular block, and right bundle branch block.

Ebstein anomaly is a rare embryonic developmental abnormality of the tricuspid valve. It occurs in 1 to 5 of 200,000 live births, accounting for approximately 0.5% of all congenital heart disease.^14,15 Most cases are sporadic and result from failure of the ventricle to delaminate during embryogenesis of the tricuspid valve, resulting in apical displacement of either the septal, posterior, or, very rarely, anterior leaflet of the tricuspid valve.^7,8 The prevalence is higher in infants whose mothers took lithium during early pregnancy.¹⁶

2. Which of the following is not a common finding associated with Ebstein anomaly?

• Apical displacement of the septal leaflet of the tricuspid valve
• Wolff-Parkinson-White syndrome
• Accessory bypass tract
• Tachyarrhythmias
• Increased risk of sudden death
• Left-sided heart failure

The answer is left-sided heart failure. Ebstein anomaly is associated with increased risk of tachyarrhythmias, right-sided heart failure, and sudden death.^7,8,17,18 In Ebstein anomaly, the tricuspid valve forms closer to the apex, so the part of the right ventricle that is superior to the displaced tricuspid valve functions as the right atrium, thus the term “atrialized” right ventricle. These abnormalities create an environment for accessory pathways, most commonly type B Wolff-Parkinson-White syndrome.¹⁹ Biventricular dysfunction can occur in rare severe cases.^7,8,18

Our patient is found to have an accessory tract-mediated antidromic atrioventricular reentrant tachycardia in the setting of Wolff-Parkinson-White syndrome and Ebstein anomaly. This is further confirmed with an electrophysiology study demonstrating a right posterior accessory pathway.

TREATMENT FOR EBSTEIN ANOMALY

3. Which treatment is advised for Ebstein anomaly?

• Observation alone
• Standard heart failure medications
• Radiofrequency catheter ablation
• Tricuspid valve repair or replacement
• Biventricular reconstruction
• Heart transplant

The answer is all of the above. Observation alone is advised for patients with mild symptoms, no evidence of right-to-left shunting, and only mild cardiomegaly. Medical management includes an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker, a beta-blocker, and diuretics. Radiofrequency catheter ablation is the first-line therapy for patients with symptomatic Wolff-Parkinson-White syndrome.²⁰ A patient who develops worsening right-sided heart failure, cyanosis, paradoxical emboli, or frequent tachyarrhythmias should be considered for corrective surgery, which may include tricuspid valve repair or replacement, or biventricular reconstruction.^7,8,21 Cardiac transplant is reserved for severe cases.⁸

On hospital day 4, our patient undergoes successful radiofrequency catheter ablation without complications. At follow-up 3 months later, he continues to do well, with resolution of his symptoms and no further evidence of pre-excitation. His postprocedure ECG no longer shows delta waves.

TAKE-HOME POINTS

• For a patient with regular wide complex tachycardia, the first step is to assess hemodynamic stability. If the patient is hemodynamically unstable, emergent cardioversion is indicated.
• The differential diagnosis for regular wide complex tachycardia includes supraventricular tachycardia with aberrancy (orthodromic atrioventricular reentrant tachycardia, antidromic atrioventricular reentrant tachycardia, atrial tachycardia), and ventricular tachycardia.
• When pre-excited atrial fibrillation is suspected, AV nodal blocking agents should be avoided, as they may worsen tachyarrhythmia. Sodium channel blockers such as procainamide can help slow down the conduction of the accessory pathway.
• Ebstein anomaly is diagnosed on transthoracic echocardiography as apical displacement of the tricuspid valve resulting in atrialization of the right ventricle.
• Patients with Ebstein anomaly have a higher risk of death from right-sided heart failure and tachyarrhythmias, most commonly type B Wolff-Parkinson-White syndrome.
• Ebstein anomaly is medically managed with standard heart failure medications, including neurohormonal blockade therapies.
• Patients with Ebstein anomaly and cyanosis require surgical intervention with either valve repair or replacement.
   

Acknowledgment: We thank Dr. William Collins for his contribution in reviewing the manuscript and his technical expertise in developing some of the figures.