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