About this Research Topic
The majority of congenital heart defects can be repaired assuring an anatomical and physiologically normal cardiovascular circuit, which includes two separate, in series, systemic and pulmonary circulations, regulated by two functional pumping chambers (i.e. the left and right ventricles). One in 3000 babies are born with congenital heart defects characterized by the presence of only one functional ventricle that cannot be repaired by modelling a biventricular circulation. These patients have necessarily to undergo a palliative pathway that includes surgical adjustments of the pulmonary flow and ends with the single ventricle circulation also known as “Fontan Circulation”. In this circulatory model de-oxygenated blood passively flows into the pulmonary circulation due to a pressure gradient between systemic veins and common atrium, whereas the single ventricle delivers oxygenated blood to the systemic organs. Conditions to achieve a good Fontan circulation are 1) a preserved ventricular function, both systolic and diastolic, and 2) a regular development of pulmonary vascular architecture and physiology. Most commonly the Single Ventricle treatment pathway includes, according to the underlying anatomy, multiple surgical and interventional catheterization steps that as stated above are critical to create a good Fontan’s candidate. In theory, this is a relatively straightforward and remarkable treatment for what was not so long ago considered a non-treatable and incompatible with life pathology. Although, advancements in both medical and surgical interventions have led to improved early mortality and morbidity, the intermediate period (> 20 years) is wrought with complications and the prospect of long term survival (> 40 years) is grim. The complications of the single ventricle circulation include both cardiovascular and extra cardiac manifestations. Cardiovascular complications include systolic and diastolic dysfunction, reduced exercise tolerance, worsening of cyanosis, arrhythmias, pulmonary vascular disease, thrombosis and stroke; extra cardiac complications typically entangle liver and renal dysfunction, protein-losing enteropathy, and plastic bronchitis; collectively they are referred to as “the failing single ventricle”. The aim of this article collection is to get a clearer understanding of the complex aspects behind the failing single ventricle circulation and to describe the current diagnostic and therapeutic options available to these patients. More in details specific contributions to the topic will address:
• Surgical Strategies to improve the Fontan Circulation. This topic will discuss the key point to achieve the “better” Fontan circulation all along the surgical pathway.
• Numerical models and simulation to improve Fontan circulation, dedicated on research about efficiency of Fontan circulation under different anatomic conditions.
• Pathophysiology of failing Single Ventricle circulation, to address the cardiovascular mechanism that causes failure and describe the clinical consequences.
• Heart Transplantation for Single Ventricle, to address the key point of medical and surgical HTX.
• Two topics will address the problems of Mechanical Assist Devices in Single Ventricle circulation, analyzing the pathophysiology of mechanical support in Single Ventricle circulation and surgical techniques to establish mechanical support, including choice of device.
• Final topics will be dedicated to future development of cell therapy to improve Single Ventricle circulation.
Keywords: Single Ventricle, Fontan Circulation, Fontan Failure, Heart Transplant for CHD, Mechanical Assist Devices for CHD
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