Single ventricle, many arrhythmias

As the wheels of progress churn forward in cardiovascular care and cardiac surgical technique, the survival rate for infants born with single ventricle physiology, once a universally fatal disease, has improved dramatically. The single ventricle reconstruction (SVR) trial recently reported an overall survival in these patients of 62% at 6 years of follow up (1,2). Fontan’s original operation featuring an atriopulmonary connection combined with an end-to-end SVC to PA connection for tricuspid atresia was a breakthrough and created normal or near normal systemic saturations in single ventricle patients. However, the abnormal physiology inherent to this circulation leads to progressive dilation of the systemic venous atrium and frequent arrhythmic complications. Modifications of the original Fontan operation were also instituted to not only address survival but also to improve morbidities that became apparent in the short, medium and long term follow up associated with the hemodynamic consequences of the original approach. The introduction of the lateral tunnel Fontan was designed to improve the energy loss of the venous system through the systemic and pulmonary circulations while also decreasing the burden of atrial arrhythmias. This technique was further refined to the extracardiac Fontan, though this strategy is frequently limited by the need to balance the size of the extracardiac conduit and the patient (3). Similarly, the surgical approach to the initial Stage I palliation has evolved over time. The initial (and still frequently used) palliation utilized a modified Blalock-Taussig shunt (MBTS) to provide a stable source of pulmonary blood in addition to the reconstruction of the aortic arch. Sano et al. revised this by incorporating a right ventricle to pulmonary artery shunt (RVPAS) and eliminating the MBTS. One of the motivations behind this development was to eliminate potential coronary steal which many thought played a role in a sizable percentage of interstage mortality. Many centers have adopted this technique and the SVR trial run by the Pediatric Heart Network was undertaken to examine the short and medium term outcomes after each type of shunt. This multicenter 6-year follow up study showed no statistically significant difference in transplant-free survival based on type of shunt at the Stage I procedure. With these improvements in survival and changes in surgical technique, providers are now able to address the significant morbidity of this vulnerable population. One major post-operative morbidity remains electrophysiologic abnormalities