What is the initial approach to managing dysrhythmia (abnormal heart rhythm) in patients post-Fontan procedure?

Management of Dysrhythmias in Post-Fontan Patients

The initial approach to managing dysrhythmias in post-Fontan patients requires immediate consultation with an electrophysiologist with expertise in congenital heart disease, as these arrhythmias can cause serious hemodynamic compromise and contribute to atrial thrombus formation. 1

Initial Assessment and Stabilization

1. Prompt recognition and evaluation:

   • Recognize that atrial tachyarrhythmias occur in up to 60% of adults with Fontan palliation and are associated with substantial morbidity and mortality 1
   • Be aware that intra-atrial reentrant tachycardia (IART) may present with modest tachycardia rates (often <150 bpm) with 2:1 block, making it easily missed 1

2. Immediate diagnostic workup:

   • Comprehensive noninvasive imaging evaluation to identify:
     • Atrial/baffle thrombus
     • Anatomic abnormalities of the Fontan pathway
     • Ventricular dysfunction 1
   • Consider the arrhythmia as a potential manifestation of hemodynamic problems in the Fontan circulation 1

3. Anticoagulation:

   • Initiate anticoagulation therapy (warfarin) for all patients with atrial arrhythmias, even if atrial thrombus has not been documented 1
   • Standard decision-making strategies about rhythm versus rate control or thromboembolic prophylaxis used for acquired heart disease do not apply to Fontan patients 1

Pharmacological Management

1. Antiarrhythmic medications:

   • Use with caution due to:
     • Common sinus node dysfunction in these patients
     • Limited venous access for pacing if AV block develops
     • Potential negative inotropic effects in patients with single ventricle dysfunction 1

2. Specific considerations:

   • Avoid negative inotropic drugs in patients with single ventricle dysfunction 1
   • Consider ACE inhibitors and diuretics for management of single ventricle dysfunction 1

Advanced Management Options

1. Electrophysiological studies:

   • Should be performed only at centers with expertise in managing patients with Fontan physiology 1
   • Consider catheter ablation for atrial tachycardias 1

2. Surgical interventions:

   • Consider Fontan conversion (revision of atriopulmonary connection to an intracardiac lateral tunnel, intra-atrial conduit, or extracardiac conduit) with concomitant Maze procedure for recurrent atrial fibrillation or flutter without hemodynamically significant anatomic abnormalities 1

3. Pacemaker therapy:

   • Consider for symptomatic bradycardia due to sinus node dysfunction, which occurs in up to 45% of adults during long-term follow-up after Fontan surgery 1
   • Epicardial approach is often required as venous access may be limited by Fontan anatomy 1

Long-term Management and Monitoring

1. Regular follow-up:

   • At least yearly follow-up at a center with expertise in adult congenital heart disease 1
   • Serial imaging to assess for thrombosis, shunts, obstructive lesions, valve dysfunction, and ventricular function 1

2. Indicators for advanced heart failure consultation:

   • Recurrent arrhythmias despite therapy
   • Need for pacemaker implantation
   • Aborted sudden cardiac death events 1

Common Pitfalls and Caveats

1. Misdiagnosis:

   • IART may present with modest tachycardia rates (<150 bpm) and can be mistaken for sinus tachycardia 1
   • The onset of atrial arrhythmias should prompt a search for Fontan obstruction 1

2. Treatment risks:

   • Antiarrhythmic drugs may worsen sinus node dysfunction or cause AV block 1
   • Venous access for pacing may not be possible depending on Fontan anatomy 1

3. Long-term complications:

   • High recurrence rates of arrhythmias (approximately 50% within 10 years) despite treatment 1
   • Arrhythmias may be the first manifestation of right atrial obstruction or thrombus formation 2

By following this structured approach with early involvement of specialists in congenital heart disease, the management of dysrhythmias in post-Fontan patients can be optimized to reduce morbidity and mortality in this complex patient population.