What is an atrial septal defect?
An atrial septal defect or ASD is an opening between the upper two chambers of the heart, known as the right atrium and the left atrium. A congenital heart defect, an ASD permits mixing of deoxygenated blood returning to the heart from the body (right atrium) and freshly oxygenated blood coming from the lungs (left atrium). The degree of mixing is largely related to the size of the defect and the relative pressures in each atrium. Early in life, blood from the left atrium preferentially moves into the right atrium, causing excessive blood to flow through the lungs. If this flow, otherwise known as “shunting” is significant enough, resistance to flow develops in the lung resulting in a gradual reversal of shunting of deoxygenated blood from the right atrium into the left atrium and subsequently through the body. This latter condition can lead to a condition called “cyanosis” whereby inadequately oxygenated blood is delivered to the body causing early fatigue and congestive heart failure.
How is an atrial septal defect treated?
Small atrial septal defects can often be followed conservatively without surgery, due to minimal shunting. Larger ASDs should be closed to prevent the late irreversible consequences of excessive left-to-right shunting. ASDs can be closed surgically by simply sewing them closed or, in the case of larger ASDs, placing a patch of the patient’s own tissue or synthetic material (e.g., Dacron) over it.
How is an atrial septal defect repaired?
ASD repairs require the use of cardiopulmonary bypass, otherwise known as “the heart-lung machine.” This permits the surgeon to safely open the right atrium and access the ASD in a relatively bloodless field. In some cases, the heart is also stopped for 1 to 2 hours to facilitate the repair. Repairs range from relatively simple operations to more complex procedures depending on the location, size, and characteristics of the ASD. The total duration of the operation ranges from 2 to 3 hours.
What are minimally invasive approaches to an atrial septal defect?
The most common surgical approach requires the surgeon to saw open the breastbone and spread the edges apart to gain direct access to the heart. Although this approach provides excellent access to the heart, the resulting wound requires several months to heal completely, an extended recovery period with substantial activity restrictions, and can be subject to serious complications including infection, breakdown, and even death.
Currently at The Johns Hopkins Hospital, the most commonly employed minimally invasive approach to ASDs is a “mini-thoracotomy” which consists of a 3 inch incision made through the right side of the chest between the ribs. Heart-lung bypass is instituted with small tubes placed in the main artery and vein of the right leg through a 1 to 2 inch incision placed in the right groin crease. The heart is then stopped and the right atrium is opened to expose the ASD. At this point, specialized hand-held “chopstick” like instruments are inserted through this small incision by the surgeon to repair the defect. After the defect is repaired, the heart is then closed and restarted. Finally, heart-lung bypass is discontinued and the incisions are closed.
Robotic ASD Repair
Another approach which is also sometimes used at our center utilizes a surgical robotic system instead of the hand-operated instruments to perform the repair. The surgical robot is designed to perform complex operations through incisions that are much smaller and less traumatic than those used with traditional surgical approaches.
The first robot-assisted cardiac operation at Johns Hopkins Hospital, performed in June 2003, consisted of successfully placing a biventricular pacemaker lead on a beating heart.
The surgical robotic system is comprised of four principal components: a surgeon console, a computerized control system, two instrument "arms," and a fiberoptic camera. The surgeon sits at the console and views the heart in three-dimensions through the fiberoptic stereoscopic camera system while manipulating the instinctive operating controls.The surgeon's hand motions are relayed to a computer processor, which digitizes and relays them to the fine instrument tips placed into the chest cavity through small 1 cm port incisions. This computerized robotic system enhances the surgeon's ability to perform minimally invasive cardiac surgery in several ways. First, the computer interface permits the accurate translation of the surgeon's hand motions to a dexterous endoscopic "wrist" placed within the chest cavity, conferring much higher degrees of freedom and precision than could be achieved with traditional hand-operated instruments. Second, the advanced two-camera stereoscopic optics provides unprecedented magnified, high-definition, full-color images of the heart and its structures in three-dimensions. This visualization provides much greater detail of the heart than is generally possible with the surgeon's eye.