Single ventricle: amphibians and human beings

Survival to adult life in patients born with “functionally” single ventricle, without any surgical treatment, as natural history, is extremely rarely reported [1–7]. In general, these group of patients with “functionally” single ventricle are symptomatic from the frst weeks of life, and require two to three staged operations to obtain that the single ventricle pumps the oxygenated blood to the systemic circulation, while the less oxygenated blood is deviated by gravity from the superior and inferior vena cava directly to the lungs [1, 8, 9]. The result of this artifcial “Fontan circulation” is high systemic venous pressure, and the chronic elevation of the systemic venous pressure may results in liver failure, renal failure, protein-losing enteropathy, and plastic bronchitis [10–17]. As a consequence, the long-term surgical outcomes of these patients are complicated by the combination of heart failure and cyanosis, substantially reducing their life expectancy and severely compromising their quality of life [10–19]. Mathematical and computational fuid dynamic models were used to study the blood fow distribution in single ventricle [20, 21], and a better design of circulation, altering the traditional surgical options [22]. Research could greatly beneft from studies performed on animals born with single ventricle, even if the only animal models available in nature are amphibians, like axolotl salamander (Ambystoma mexicanum) [7] and frogs (Xenopus laevis) [23, 24], and reptiles. These experimental studies on amphibians, performed with echocardiography and cardiac magnetic resonance imaging, revealed that salamanders and frogs have two elements in common in their double inlet form of single ventricle: intact interatrial septum and excessively trabeculated ventricular chamber.