The “defect” of an atrial septal defect (ASD) refers to an abnormal communication or “hole” in the upper chambers of the heart (the atria). The hole forms within the heart tissue separating the two upper chambers during heart development. This hole can be small or large and may go undetected for years. In addition there can be a number of small holes that create several communications between the two upper chambers of the heart. Blood flows in the wrong direction across the defect (left to right) creating significant mixing of oxygenated and nonoxygenated blood which may cause shortness of breath and fatigue with time. Most importantly, this abnormal flow of blood increases the amount of blood presented to the right side of the heart and causes increased loading of the right heart and an increase in the lung pressures (pulmonary hypertension).

If left unchecked, this will ultimately result in right heart failure and pulmonary hypertension that may be irreversible. Finally, this defect can create a passage for clots from the right side of the heart (usually filtered by the lung) into the left heart and then to the brain resulting in a stroke.

Two current treatments exist for closing these defects, surgical (open-chest/heart) and catheter-based (nonsurgical). Both are safe and effective ways of managing ASDs and both prevent the adverse effects described above.