The heart is divided into right and left sides by a septum, or wall, during embryonic development. Occasionally, holes or defects in this wall develop. If the hole occurs between the right and left upper heart chambers (atria), it is called an atrial septal defect; if it occurs between the lower chambers (ventricles), it is called a ventricular septal defect. The seriousness of the problem depends on the size of the opening or hole.
There are several possible outcomes of atrioventricular septal defects. With small defects, there may be little or no effect on heart function, and the pet may seem completely normal. In others, there may be partial or complete closure of the defect by a portion of the heart valve. Patients with larger defects may develop congestive heart failure or low oxygen levels in the blood and exhibit bluish-colored membranes (cyanosis).
Important Points in Treatment
1. Correction of septal defects requires open heart surgery using a cardiopulmonary bypass. These operations are rare and are usually performed at major veterinary referral centers.
2. Pets with congestive heart failure can sometimes be treated effectively for long periods.