Discussion
SV heart defect is a rare congenital cyanotic heart disease often associated with PS, TGA, atrial septal defect, and other malformations. Echocardiography is the first choice for the diagnosis and evaluation of SV. Echocardiography can also be used to diagnose cardiac malformations in the early and second trimester of pregnancy, to make accurate judgments regarding the classification of SV, its associated malformations, and atrioventricular valve openings and reflux, as well as to evaluate ventricular function.4 SV heart defects can be divided into four types according to the morphological structure: Type A, the left ventricular main chamber is dominant; Type B, the right ventricular main chamber is dominant; Type C, the ventricular septum is absent, and the left and right ventricular structures constitute the ventricular cavity; and Type D, indeterminate.5 Unlike echocardiography, three-dimensional ultrasound can visually display the internal structure of the heart, thus improving the accuracy of preoperative diagnosis, and is of great significance in the selection of surgical methods and the assessment of prognosis.6
We reviewed literature reports of SV heart defect cases involving patients over 13 years of age without surgical intervention and summarized the common characteristics that were correlated to the long-term survival of the patients (Table 1). The aforementioned four patients in this study were diagnosed with SV heart defects during childhood, but received no surgical intervention. All four patients had appreciable outcomes. Table 1 shows that the clinical manifestations and long-term prognosis of patients with SV heart defects primarily depend on the presence or absence of pulmonary blood flow obstruction, pulmonary vascular resistance, and ventricular shape and function. Whether the aortic blood flow is blocked and whether the shape and function of atrioventricular valve still function play an important role in patient prognosis. Moderate PS is critical for hemodynamic balance in SV patients; first, it restricts pulmonary blood flow and prevents pulmonary arteriole disease; second, it restricts the left-to-right shunt, prevents pulmonary blood flow increase and ventricular overload, and maintains sufficient pulmonary blood flow to supply oxygen. In addition, SV patients with adequate oxygenation and balanced ventricular load may have a chance for long-term survival. The morphology and function of the ventricles is another important factor. There are, in fact, no reports of long-term survival for patients with right morphology or an indeterminate-type SV. This is probably due to the intrinsic capacity of the left ventricle to deal with systemic resistance. When all other conditions are equal, patients with a single left ventricle heart defect have better prognosis than those with a single right ventricle heart defect. When aortic blood flow resistance increases, the ventricular afterload also increases, leading to a low cardiac output, which is not conducive to survival. In addition, effective and detached atrioventricular valves have a positive effect on survival. Atrioventricular valve dysfunction leads to ventricular volume overload. The optimal anatomical structure for SV patients is a normal morphology for the left ventricle, great artery displacement, no systematic obstruction of outflow tract, full atrioventricular valve function, and moderate PS. These anatomical features enable patients to survive mild to moderate symptoms and enjoy a good quality of life. It should also be noted that arrhythmias are the most common complications in older SV patients.7With the improvement of surgical techniques and postoperative care, more SV patients have been able to survive for a longer period of time. The main treatment methods for SV patients are radical surgery, palliative surgery, and heart transplantation (Figure 5). The palliative surgery mainly includes modified Blalock-Taussig (B-T) shunt operation, PA banding, Norwood operation, Glenn operation, and Fontan operation.8