Triatrial heart is a rare congenital cardiovascular malformation. Anatomically, the left atrium is divided into two parts by an anomalous fibromuscular septum or septum: the proximal side of the septum, the right posterior superior parasternal chamber or paracardial cavity or third chamber, which receives pulmonary venous blood flow, and the distal side of the septum, the left anterior inferior, which is the true left atrium that is intrinsic to the left auricle, mitral valve, and left ventricle and is connected by an orifice in the septum. This malformation may be present alone or in combination with other malformations, most commonly atrial septal defect or complete anomalous pulmonary venous reflux.
It is generally believed that the common venous trunk fails to fuse with the left atrium during embryogenesis, while the common pulmonary vein enlarges to form part of the left atrium and fails to fuse with the original left atrium to form a parasternal atrium. As well as abnormal development of the primary atrial septum, the abnormal septum within the left atrium separates the left atrium into the paratria and the true left atrium.
The hemodynamic changes depend on the size of the intra-atrial septal orifice and concurrent malformations. The hemodynamics of a solitary left-sided triatrial heart resemble mitral stenosis, and in cases where the left septal orifice is only a few millimeters in diameter, it may cause pulmonary venous reflux stasis, pulmonary depression, pulmonary edema, and pulmonary hypertension, complicated by partial abnormal pulmonary venous return or a left-to-right shunt if the septal defect is located between the right atrium and the parasternal atrium, or a right-to-left shunt if the septal defect is in close proximity to the intrinsic atrial cavity.
Clinical types.
1, Type I: No communication between the paratria and the true left atrium, with paratrial traffic through the foramen ovale or with complete abnormal pulmonary venous reflux.
2. Type II: One to several small channels between the paratria and the true left atrium, which are subdivided into two subtypes from a clinico-surgical perspective.
(1) Not communicating with the right atrium, with clinical manifestations similar to mitral stenosis symptoms.
(2) Connected to the right atrium, with clinical manifestations similar to those of atrial septal defect or complete abnormal pulmonary venous reflux.
3. Type III: Large communication exists between the parasternal atrium and the true left atrium.
Auxiliary examinations.
1.X-ray examination: mild to moderate enlargement of the heart, with right ventricular hypertrophy predominant, marked pulmonary circulatory hypertension but little or only mild enlargement of the left atrium as its characteristics, dilated superior vena cava, interstitial pulmonary edema, and prominent pulmonary artery segment showing signs of pulmonary arterial and venous hypertension.
2.Electrocardiogram: right-sided electrical axis, right ventricular hypertrophy, and increased P waves suggest right atrial hypertrophy.
3.Echocardiography: B-type echocardiography shows abnormal septal echogenicity in the left atrium and can be seen above the mitral valve. Pulsed Doppler ultrasonography can show the abnormal septum, and can see the blood flow through the orifice on the septum and the size of the atrial septal defect, which is very helpful for diagnosis.
4, cardiac catheterization and imaging: right heart catheterization such as measured pulmonary artery wedge pressure increased while the true left atrial pressure is low or normal for its characteristics. In about 1/3 cases, the catheter enters the right atrium and then enters the left atrium through the atrial septal defect or oval foramen. The imaging of the left atrium can show the presence of abnormal septum in the left atrium, and if it can show the parasternal atrium, it can be found that the contraction is not seen in the cardiac cycle and remains constant. Routine cardiac catheterization angiography is not usually required.
Treatment measures.
Once the diagnosis of triple atrial heart is established, surgical treatment is the only method. Adequate removal of the septum under extracorporeal circulation is required, along with repair of the atrial septal defect and correction of other combined intracardiac malformations. The following two surgical routes are often used.
1. left atrial incision through the atrial sulcus, for infants and children without atrial septal defects.
2. A right atrial incision through the atrial septum into the left atrium, for children with large atrial septal defects.
Prognosis of triple atrial heart.
The surgical result is good, and the pulmonary artery pressure may fall to normal after surgery. Mortality is high in infants and children with congestive heart failure.