Abnormal formation of the common atrioventricular valve in place of the mitral and tricuspid valves occurs at a relatively rare heart malformation, an open atrioventricular canal (OAVC). Its incidence rate in the structure of all congenital heart defects does not exceed 3 to 5%. OAVC is developed in utero under the influence of chromosomal abnormalities, genetic predisposition, infections, toxins, or endocrine pathology.
A partial OAVC form, whereby the septum between the heart ventricles is preserved, does not normally require early surgical treatment. The optimal age for surgical correction in this case is 7 to 10 years old.
A complete OAVC form, with the presence of a hole in the interventricular septum, often leads to severe manifestations of hemodynamic instability threatening the child's life, so the patients often must be operated very early. In the course of preparation for surgical correction, the conservative therapy is prescribed:
- cardiac glycosides;
- ACE inhibitors.
The decision on the urgency of OAVC surgical correction is made by a physician based on the clinical picture and structural damage degree. The surgical treatment method is chosen individually.
- Closure of atrial septal defect is indicated for a partial form of OAVC. The surgery requires an open access using the hypothermia and cardiopulmonary bypass. For a small diameter of the hole, the defect is sutured; otherwise it is covered with a patch made of synthetic material.
- Mitral and tricuspid valve plastics is indicated for partial OAVC. Missing leaflets are made from synthetic materials, the stretched hole is contracted with sutures and reinforced with support rings.
- Septum and valve plastics is the only version for correction of a complete form of OAVC. The surgery implies correction of all anomalies of the heart structure. The missing septa are created from biological or synthetic materials, forming complete mitral and tricuspid valves.
- Palliative surgeries sometimes help postpone the time of full correction and improve the patient's condition. For a complete form of OAVC, the narrowing of the pulmonary artery trunk, which reduces the heart congestion, improves the patient’s condition and prevents the formation of irreversible changes in the myocardium and blood vessels.
Adequate medical therapy and timely surgical correction performed by an experienced cardiac surgeon in a specialized center, in most cases, allow hoping for a positive result.