OFF Pump Coronary Artery Bypass surgery is the most popular minimally invasive heart bypass operation today, one that is done on a beating heart. Conventionally, coronary bypass is done on an arrested heart (chemically-induced cardiac arrest to allow for a quiet field) with the patient connected to a heart-lung machine (pump) that temporarily takes over the oxygenation (lung function) and circulation (heart function) of the patient while the surgery is going on.
Is OPCAB better?
If at all possible, OPCAB, or beating heart surgery, is preferred. Doing the coronary bypass on a beating (non-arrested) heart precludes the use of the heart lung machine. This pump has the potential of destroying some blood cells, of wasting some essential clotting factors in the blood, and of forming blood clots or air bubbles that could cause stroke, albeit very rare. So, not using the heart-lung machine is a definite advantage, much less invasive and stressful for the patient. As a result, OPCAB patients recover a lot faster, go home much sooner, usually after 3-4 days after surgery. However, OPCAB is not for everyone.
How is the heart stilled?
With the patient connected to the pump, the heart is arrested by lowering the body temperature (thru blood cooling using a special cooler machine connected to the pump) down to about 28-30 degrees centigrade, and by giving the patient a high dose of potassium chloride which stops the heart beat in a relaxed (flabby) muscular state. This allows the cardiac surgeon to make tiny (2 mm-4 mm) anastomoses (suturing together two arteries or a vein and an artery of the heart, like sewing a sleeve to the shirt, an end-to-side or T-connection) using a magnifying surgical loop (special eyeglasses for an enlarged view), on a non-beating heart.
What are the sizes of the arteries?
The coronary arteries (which feed the muscles of the heart) and the internal mammary arteries (which are harvested as grafts from the undersurface of the breast bone, one from the left and one from the right side) are usually about 2 to 3 millimeters in diameter, about the size of a round toothpick or the lead in pencils. The vein grafts that are harvested from the leg are on the average about 4 to 5 mm in diameter.
To connect vessels this small, we arrest the heart and use a magnifying loop as mentioned above for precise suturing. This is a delicate and a most essential part of the bypass surgery, and requires extreme attention to details, in order for the “pipe connection” to allow maximum blood flow, with the least resistance or impedance. Any buckling, purse-stringing, or twisting of the anastomosis will cause blood clots in the area of the T-joint which eventually blocks off, leading to failure of the surgery. This could spell a disaster, a heart attack. This particular “plumbing job” must be “perfect.”
What suture materials are used?
The sutures we use for the anastomoses have a diameter smaller than human hair. They are technically known as 6-0, 7-0, or, 8-0, which is the smallest of the three. They are prophylene (plastic-like, but with greater tensile strength) sutures, commercially called Prolene, which are non-absorbable, unlike silk, which disintegrate with time. Prolene sutures stay intact forever.
How are blockages diagnosed?
The stenoses (narrowing) or occlusion (total blockage) of the coronary arteries are diagnosed with the aid of coronary angiogram (also referred to as cardiac catherterization), where a spaghetti-sized catheter is inserted into the femoral (groin) artery under local anesthesia and its tip directed to the opening of the left and right main coronary arteries. Dye is injected into the coronary arteries and the whole procedure is recorded in a video movie. This will show the dye in motion, the diameter and integrity of the lumen (inner channel) of the arteries and whether there are blockages or none.
Why not do this test on everyone?
While cardiac catheterization is a safe procedure done daily in various heart centers around the world, it has potential complications like transient irregular heart rhythm, blood clots, arterial leak, disruption in the wall of the artery, bleeding at the puncture site in the groin. While these are rare, there is a golden rule in medicine that says tests, in general, must only be done if there is an clinical indication (justification). If a person has no symptoms or strong family history of heart disease, cardiac catheterization is not recommended. Just about the only exceptions could be an employer required executive check-up, or airline mandated test for commercial pilots. Besides, this is an expensive procedure and insurance companies do not consider this to be a reimbursable prophylactic test.
How is OPCAB done?
With the patient under general anesthesia, the chest is split in the middle, from the base of the neck down to about the tail of the sternum (breastbone), same as in the conventional technique. With OPCAB, the patient is not connected to a heart lung machine. There is a special instrument (cardiac stabilizer) that minimizes the heart action in the area of the artery to be bypassed. The rest of the heart continues to beat. This stabilizer restricts the contraction of the heart in the target area, allowing the cardiac surgeon to do his suturing, aided by a surgical loop for magnified (3-4 times) view. With beating heart surgery, the patient does not feel so zapped, rundown and tired compared to the standard procedure where heart lung machine and cardiac arrest are used.
Does every heart surgeon do OPCAB?
No. Only those who had additional training on this particular technique perform beating heart surgery. It is a more tedious procedure and more difficult for the surgeon but much easier on the patient. Putting sutures on tiny arteries while the heart is beating is just like “shooting a tiny moving target.” A surgeon has to “retrain” his mind and hands, and gets used to this cutting edge-technology to be able to do OPCAB.
This writer had to undergo such hands-on OPCAB surgical training at the Boston University Hospital in Massachussetts, under Dr. R. Cohn, the inventor of the Genzyme Cardiac Stabilizer. My team and I did our first OPCAB on a 68-year-old American from California, a retiree in Cebu, on June 8, 1999, the first quadruple OPCAB bypass performed in the Philippines, at the Cebu Doctors University Hospital. Even in the United States, only a little more than 60% of the surgeons perform OPCAB procedures.
Is the conventional bypass obsolete?
Most definitely not. There are still a large number of patients who could be better served with the conventional on-pump heart bypass. As I stated earlier, OPCAB is not for everyone. But the trend shows more and more coronary bypass procedures are being done on beating hearts today. It stands to reason that OPCAB is here to stay.