Transposition With Atrial Switch and Risk of Sudden Death: Submitted by Marc G. Cribbs, MD, FACC

Case Synopsis

LB is a 26-year-old male with a history of dextro-transposition of the great arteries (DTGA) and intact ventricular septum. Desaturation and restriction of atrial level flow was almost immediately apparent and balloon atrial septostomy was performed just hours after he was born. At 3 months of age, he underwent a Senning-type atrial switch operation.

One month after surgery, he was admitted with an atrial tachycardia for which he was started on propranolol. The arrhythmia improved and regular follow-up demonstrated normal sinus rhythm with no evidence of pathologic tachycardia. LB maintained close congenital cardiology follow-up until he was 15 years of age and was then lost to follow-up.

At age 26 years, he presented with the New York Heart Association (NYHA) class IV heart failure. He was admitted to the CCU and the adult congenital heart disease (ACHD) team was consulted. He described a 6-month history of progressive shortness of breath, fatigue, three- to four-pillow orthopnea, and paroxysmal nocturnal dyspnoea. He also complained of a 10- to 15-pound weight loss over the previous 3 months because of nausea and early satiety. Most notable was a history of palpitations that had preceded all these symptoms. The palpitations were initially noted as infrequent episodes of “rapid heart rate” that, over time, became more and more frequent. There was no history of syncope. There was also no history of drug, tobacco, or alcohol use.

A transthoracic echocardiogram suggested severe biventricular dysfunction and moderate tricuspid insufficiency; however, the images were of poor quality. A cardiac MRI later confirmed severe systemic right ventricular (RV) dysfunction (right ventricular ejection fraction [RVEF], 20%), severe pulmonic left ventricular dysfunction (left ventricular ejection fraction, 22%), moderate systemic tricuspid insufficiency, and no evidence of systemic or pulmonary venous baffle dysfunction. With this and the palpitation history in mind, LB was taken to the electrophysiology (EP) laboratory where an atrioventricular nodal reentry tachycardia (AVNRT) was mapped and successfully ablated. Hemodynamic assessment at the time of EP study revealed a cardiac index of 2.1 L/min/m ² . He was initiated on intravenous milrinone, gradually transitioned to conventional oral medications, and discharged home 3 weeks later with NHYA class II–III symptoms.

For the next 2 months, the patient maintained close ACHD follow-up and adherence to all medications. Follow-up rhythm monitoring (Holter as well as a 30-day event monitor) demonstrated no evidence of arrhythmia, rare premature atrial contractions, and a single 8-beat run of nonsustained ventricular tachycardia (VT). Again there was no syncope. Subsequent imaging with transthoracic echocardiography, however, demonstrated no improvement in cardiac function and his exertional shortness of breath and fatigue returned. He was readmitted, this time to the Heart Failure and Transplant Service. A right heart catheterization subsequently demonstrated a cardiac index of 1.5 L/min/m ² , modestly elevated filling pressures (wedge pressure, 15–19 mmHg), and no evidence of baffle dysfunction. Given this, heart transplant evaluation was started. The ACHD team was also consulted regarding prophylactic implantable cardioverter defibrillator (ICD) placement in this patient with severe biventricular dysfunction.