3. DISCUSSION
Epicardial pacing has been a regular option for patients with complex congenital heart disease. Epicardial leads may be placed during cardiac surgery for underlying congenital heart disease with a plan to replace them in the future with transvenous leads.4Endocardial pacing of the ventricle for patients with Fontan circulation was impractical due to the lack of transvenous access to the ventricle. With the advances in pacing techniques, ventricular pacing in these patients is possible. Hsieh et al. reported permanent pacing of the left ventricle via coronary sinus in a patient with Fontan circulation and complete atrioventricular (AV) block.6 In another case report of a single ventricle patient using the endocardial method, DeWitt et al. described successfully placing a ventricular pacing lead through a trans-Fontan-baffle puncture.7 These techniques may be good alternatives to high-risk epicardial pacing methods in this group of patients.
Endocardial ventricular pacing is technically possible in patients with univentricular hearts who have not had previous reconstructive surgery, but the higher risk for thromboembolism limits this procedure.2 In a cohort study of 202 patients, transvenous pacemakers increased the risk of systemic thromboembolism in patients with intracardiac shunt by >2-fold, and anticoagulant therapy with warfarin or aspirin did not reduce the risk.3 However, when the risk of the surgery for epicardial lead placement is high transvenous route may be the better choice. This case was a candidate for a Fontan procedure with epicardial lead placement, but this was a high-risk procedure considering his chronic high pulmonary artery pressure. As a result, we deemed that transvenous lead placement with a tight anticoagulant regimen is the option with the lower risk. According to our research, this is the second report of left ventricular endocardial pacing via the interatrial septum in a single ventricle patient. In a similar study, Scott et al. reported a case of tricuspid atresia with intracardiac shunt and symptomatic chronotropic incompetence. They implanted an endocardial pacemaker in his left ventricle through the atrial septal defect to improve his condition. The patient had no thromboembolic events or complications related to the procedure at the one-year follow-up.8
There are few studies comparing the outcomes of dual-chamber pacing versus single-chamber ventricular pacing in patients with single ventricle physiology. Nevertheless, dual-chamber pacemakers are generally considered in these patients because of atrioventricular synchrony, which enhances cardiac output and the capacity to interfere if atrial arrhythmia or sick sinus syndrome occurs.9
The bilateral perirenal fluid accumulation was a rare finding in the present case. It has been reported in cases with intracardiac shunt and pulmonary hypertension.10,11 Pentimone et al. proposed that the underlying mechanism is that pulmonary hypertension increases local hydrostatic pressure in the perirenal veins, leading to fluid leakage to the renal subcapsular space. In their case repeated phlebotomies lowerd hematocrit and reduced perirenal fluid significantly.10
In conclusion, while endocardial pacing, in the presence of intracardiac shunts, has the risk of systemic thromboembolism, it may be the safer alternative for epicardial interventions in selected patients.