Unrepaired Primum Atrial Septal Defect With Atrial Fibrillation and Broad Complex Tachycardia: Submitted by J.P. Bokma, MD, PhD

Case Synopsis

A 67-year-old man was referred to our hospital because of recurrent episodes of palpitations for the previous 3 years, which he described as irregular and fast. These episodes occurred several times per year. The palpitations usually started when he was at rest after a longer period of work or with stress. The diagnosis of atrial fibrillation was established and electric cardioversion was performed. A primum atrial septal defect (ASD) was diagnosed using transthoracic echocardiography. Considering the limited shunting and atrioventricular (AV) valve regurgitation, no intervention was performed.

The patient was then treated for several years with sotalol to prevent atrial fibrillation. A daily dosage of 240 mg was not tolerated because of increasing complaints of fatigue and exercise intolerance. A daily dosage of 120 mg was not sufficient to prevent recurrences. Within these recurrent episodes, the patient sometimes noticed a brief change in the palpitations. Suddenly the heart rhythm became fast and regular, during which the patient felt light-headed and needed to sit down. These episodes lasted no longer than approximately 20 s and he never lost consciousness.

He was admitted for atrial fibrillation to a community hospital. However, in preparing for cardioversion, the rhythm changed on the monitor, and patient described the known symptoms of light-headedness combined with fast regular palpitations. The monitor recording of that episode is shown in Fig. 4.1 . During the symptoms, he appeared to have recurrent and rapid (220/min) nonsustained monomorphic broad complex tachycardia (maximum 16 beats) , which terminated without intervention. During this broad complex tachycardia, there was a rightward shift of the QRS axis. Upon termination, he was again noted to be in atrial fibrillation.

After cardioversion during atrial fibrillation, sinus rhythm was restored. As the first diagnostic step, the congenital heart defect was reviewed in our hospital by transesophageal echocardiography to determine whether any intervention was needed for the underlying hemodynamic defect. During investigation, a primum ASD was observed with a left–right shunt limited to the atrial level ( Fig. 4.2 ). The magnitude of the shunt was small and the left-sided AV valve regurgitation was considered mild to moderate. The ventricular septum was intact. Right ventricular function was mildly impaired.

As the next step, a cardiovascular magnetic resonance imaging (MRI) scan was performed. The right ventricular ejection fraction was 44% and left ventricular function was normal. There was no clear difference in stroke volumes. There were no signs of ischemia and the myocardium showed no late enhancement, suggesting no large ventricular scars that could act as substrates for ventricular tachycardia (VT). Overall, an ischemic origin of the VTs was felt to be unlikely, although the VT episodes occurred mainly during fast atrial fibrillation.

At exercise testing, nonsustained VT (maximum 22 beats, 220/min) and polymorphic premature ventricular complexes (PVCs) were observed. The nonsustained VT during exercise had a morphology similar to that of the nonsustained VTs previously observed during atrial fibrillation ( Fig. 4.1 ). Owing to the persistent VT episodes with hemodynamic compromise, which were inadequately controlled with medication, an electrophysiologic study (EPS) was performed. During the EPS, PVCs were detected with a morphology similar to the clinical nonsustained VT, and ablation of a left-sided septal substrate just below the AV valve was successfully performed. However, PVCs with a different left bundle branch block (LBBB)-like configuration continued after ablation. An implantable cardioverter defibrillator (ICD) was implanted successfully afterward to prevent sudden cardiac death (SCD). There were no ventricular arrhythmias during the exercise testing performed after VT ablation, and our patient remained in sinus rhythm.