Unusual method of creation of a transcatheter fenestration in an extracardiac conduit Fontan circulation

Superior Cavopulmonary Connection: Its Physiology, Limitations, and Anesthetic Implications

The superior cavopulmonary connection (SCPC) or "bidirectional Glenn" is an integral, intermediate stage in palliation of single ventricle patients to the Fontan procedure. The procedure, normally performed at 3 to 6 months of life, increases effective pulmonary blood flow and reduces the ventricular volume load in patients with single ventricle (parallel circulation) physiology. While the SCPC, with or without additional sources of pulmonary blood flow, cannot be considered a long-term palliation strategy, there are a subset of patients who require SCPC palliation for a longer interval than the typical patient. In this article, we will review the physiology of SCPC, the consequences of prolonged SCPC palliation, and modes of failure. We will also discuss strategies to augment pulmonary blood flow in the presence of an SCPC. The anesthetic considerations in SCPC patients will also be discussed, as these patients may present for noncardiac surgery from infancy to adulthood.

Endocardial transvenous pacing in patients with surgically palliated univentricular hearts: A review on different techniques, problems and management

Fontan surgery and its modifications have improved survival in various forms of univentricular hearts. A regular atrial rhythm with atrioventricular synchrony is one of the most important prerequisite for the long-term effective functioning of this preload dependent circulation. A significant proportion of these survivors need various forms of pacing for bradyarrhythmias, often due to sinus nodal dysfunction and sometimes due to atrioventricular nodal block. The diversion of the venous flows away from the cardiac chambers following this surgery takes away the simpler endocardial pacing options through the superior vena cava. The added risks of thromboembolism associated with endocardial leads in systemic ventricles have made epicardial pacing as the procedure of choice. However challenges in epicardial pacing include surgical adhesions, increased pacing thresholds leading to early battery depletion and frequent lead fractures. When epicardial pacing fails, endocardial lead placement is equally challenging due to lack of access to the cardiac chambers in Fontan circulation. This review discusses the univentricular heart morphologies that may warrant pacing, issues about epicardial pacing, different techniques for endocardial pacing in patients with disconnected superior vena cava, pacing in different modifications of Fontan surgeries, issues of systemic thromboembolism with endocardial leads, atrioventricular valve regurgitation attributed to pacing leads and device infections. In a vast majority of patients following Glenn shunt and Senning surgery, an epicardial pacing and lead replacement is always feasible though technically very difficult. This article highlights the different options of transatrial and transventricular endocardial pacing.

•

Fontan surgery prolongs the mean survival of patients with univentricular hearts beyond 30 years.

•

9-20% of survivors need permanent pacing for bradyarrhythmias.

•

Epicardial pacing is preferred as the first choice for permanent pacemaker.

•

There is 20-40% failure of permanent pacing at 10 years due to high threshold, lead fractures.

•

Repeated epicardial pacing with surgical revisions are difficult.

•

Endocardial pacing involves special techniques.

•

Manoeuvring through fenestrations,venous collaterals, hepatic veins, pulmonary valve or hybrid peratrial routes is needed.

•

Systemic thromboembolism, endocarditis and systemic AV valve regurgitation should be prevented by meticulously measures.

A computational study of the Fontan circulation with fenestration or hepatic vein exclusion

Fontan patients may undergo additional surgical modifications to mitigate complications like protein-losing enteropathy, liver cirrhosis, and other issues in their splanchnic circulation. Recent case reports show promise for several types of modifications, but the subtle effects of these surgeries on the circulation are not well understood. In this paper, we employ mathematical modeling of blood flow to systematically quantify the impact of these surgical changes on extracardiac Fontan hemodynamics. We investigate two modifications: (1) the fenestrated Fontan and (2) the Fontan with hepatic vein exclusion. Closed-loop hemodynamic models are used, which consist of one-dimensional networks for the major vessels and zero-dimensional models for the heart and organ beds. Numerical results suggest the hepatic vein exclusion has the greatest overall impact on the hemodynamics, followed by the largest sized fenestration. In particular, the hepatic vein exclusion drastically lowers portal venous pressure while the fenestration decreases pulmonary artery pressure. Both modifications increase flow to the intestines, a finding consistent with their utility in clinical practice for combating complications in the splanchnic circulation.