OFF PUMP CORONARY ARTERY BYPASS, OPCAB
What Is OPCAB? | Procedure | Off-Pump Techniques and Instrumentation
Comparisons | OPCAB vs. CABG | Heart-Lung Machine Complications
OPCAB vs. MIDCAB | Costs | Videos | OPCAB References
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The off-pump technique, also known as OPCAB, is very similar to the conventional Coronary Artery Bypass Grafting (CABG) procedure. OPCAB still utilizes a medial sternotomy, however the important difference is that the cardiopulmonary bypass pump is no longer employed. |
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Procedure:
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OPCAB was developed from the minimally invasive school of thought, so the basic premise is to reduce incision sizes. A surgeon will perform median sternotomy of varying sizes (depending on the physiology of the patient, the smallest incision will be made). Arteries or veins can be harvested from the patients chest wall, arm, and or leg. |
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To aid the surgeon in operating on the beating heart, drugs such as Adenosine and Esmolol are used to slow the heart rate. To allow for access to the entire heart, there must be a sufficient amount of cardiac displacement. This is accomplished by deep pericardial sutures and the use of specialized instruments to prop the heart in a position that will allow the surgeon to access occluded arteries. |
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Once within the pericardial sac, sponges are used to reduce free blood in the region being operated on. The sponges also serve as a way to displace the heart, allowing a clear view of the region for anastomosis. With the heart still beating, there is a greater difficulty in performing a bypass on the posterior and lateral walls of the heart. Surgeons have found many ways to stabilize the heart in order to bypass the necessary arteries. Along with sponges, some surgeons will use slings to prop the heart in the necessary positions and then utilize a stabilizer to focus on a particular occluded artery. Biotechnical firms have also developed products such as the Octopus® that help to stabilize pertinent regions of that heart during surgery. Some surgeons will prepare the patient for attachment to the cardiopulmonary bypass pump in case of an emergency or accident that might occur during the operation. This is precautionary and not all surgeons will choose to do so. |
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The length of the operation depends on a number of variables. Much like CABG, the number of occlusions can greatly effect the length of time on the operating table. The removal of the cardiopulmonary bypass pump does reduce time since it does not need to be attached and the heart does not need to be reanimated. However, the beating heart must be handled with a great amount of care. To reach an artery on the lateral wall of the heart, the heart must be propped and stabilized, all of which can add to the length of the operation.
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Techniques and Instrumentation used to Operate on a Beating Heart Minimally invasive procedures which are done on a beating heart and do not use cardiopulmonary bypass (the heart-lung machine), such as MIDCAB and OPCAB operations, are called off-pump procedures. These off-pump procedures require special techniques and instrumentation in order to perform efficient and reliable anastomosis on the beating heart. Click on the heading for a page describing these techniques and instrumentation. |
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Click on the heading for a page with a table comparing the basics between all minimally invasive surgeries, or continue for in-depth analysis of OPCAB vs. CABG and OPCAB vs. MIDCAB.
OPCAB vs. CABG
There are a number of studies being done on all types of minimally invasive surgeries. The studies in progress offer a short-term look at the reliability of minimally invasive procedures.
In a study performed by the Cardiac Surgical Associates, P.A. in Minneapolis, Minnesota, the comparison of OPCAB to CABG patients showed that (by percentage) OPCAB had similar or better results.
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Stroke N (%) |
New Renal Failure N (%) |
New Atrial Fib N (%) |
Mortality N (%) |
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Low Risk |
On Pump N=2360 |
30 (1.3) |
99 (4.2) |
500 (21.2) |
27 (1.1) |
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0-2.59 |
Off Pump N=216 |
2 (0.9) |
7 (3.2) |
26 (12.0) |
3 (1.4) |
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N=2576 |
P -value |
1.0 |
0.499 |
0.001 |
0.736 |
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Medium Risk |
On Pump N=688 |
29 (4.2) |
71 (10.3) |
187 (27.2) |
45 (6.5) |
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2.6-9.9 |
Off Pump N=95 |
3 (3.2) |
9 (9.5) |
17 (17.9) |
6 (6.3) |
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N=783 |
P -value |
0.787 |
0.799 |
0.053 |
0.934 |
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High Risk |
On Pump N=123 |
6 (4.9) |
26 (21.1) |
34 (27.6) |
35 (28.5) |
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> 10 |
Off Pump N=39 |
0 (0) |
1 (2.6) |
7 (17.9) |
3 (7.7) |
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N=162 |
P -value |
0.337 |
0.006 |
0.225 |
0.008 |
In another study that was presented at an Annual Meeting of the Society of Thoracic Surgeons, the following information was found:
The hypothesis for the study was that off-pump surgery would reduce some of the side effects of conventional cardiopulmonary bypass surgery that stops the heart and restarts it after surgery. There were no hospital deaths in the off-pump group compared to nine deaths in the CABG group. Off-pump surgery also reduced the average postoperative hospital stay from 5.5 days to 3.3 days. Perhaps the most significant statistic was the reduction in the need for transfusion after the operation. Less than a third of the off-pump patients (29.6 percent) needed transfusions compared to more than half (56.5 percent) of the CABG group.
The problem is that there is, and will not be for a number of years, any data assessing the outcome of an off pump coronary artery bypass. The clear problem with the lack of data backing up the OPCAB procedure is why stray from conventional CABG that has a 99% success rate, as well as success over time.
OPCAB, it is believed, could be performed in 30-40% of coronary artery bypass situations (60-70% of the time, the physiology of the patient does not allow for an off-pump procedure). Many problems with the procedure have been dealt with over the past few years of development. For example, there were reports of a decrease in cardiac output by 33%. This was remedied by volume loading of the right ventricle. Surgeons have also become more familiar with the procedure and learned that during OPCAB, the systolic pressure should not be allowed to fall below 100 mmHg.
However, there are some questions about the safety of the procedure. Critics of OPCAB have presented several issues that may make this new procedure a poor alternative to CABG. The underlying problem is the lack of data supporting the patients status five to ten years down the road following bypass surgery using OPCAB. Another point being made is the sutures may not hold given that they were made on a beating heart. This point can not be contested since there is no long-term postoperative data that can show that the sutures held allowing for successful anastomosis. The major risk in OPCAB is that surgeons may not have a great deal of experience with the procedure. This could lead to poor or even fatal outcomes.
Why Avoid The Heart-Lung Machine?
Since the invention of a crude version of the heart-lung machine in 1955, it has aided surgeons in performing open-heart and bypass surgeries. Over time, the machine was refined to its current form, allowing surgeons to carry out open-heart procedures with a success rate of nearly 99%. Though the heart-lung machine has proven to be a major reason for the success of CABG procedures, there is some pathology associated with its use [17].
All of these factors leads to what some doctors call a "whole body inflammation". Doctors believe complications will increase with the amount of time a person is left on the cardiopulmonary pump. Complications inculde:
OPCAB vs. MIDCAB
The main reason why a patient may receive OPCAB as opposed to
MIDCAB is the number of vessels that need to be replaced. In the earlier days of OPCAB, surgeons were only able to reach blocked arteries on the front wall of the heart. As this surgical method has evolved over the past few years, new devices have been developed to allow the heart to be displaced from the protective pericardium. Once exposed, the heart is stabilized through various methods in various positions. This gives surgeons the ability to access arteries on anterior and lateral walls of the heart. Given this advantage, patients that suffer from multiple occlusions may receive OPCAB.The safety of these two procedures is still in question. OPCAB and MIDCAB have not been around for more than a few years, and the long term results are not known. The short-term studies done on the two procedures have given similar results, both showing promise of a safe alternative to conventional CABG. However, the physical condition as well as the number of occlusions to be removed will be a determinant in choosing OPCAB over MIDCAB (an over weight patient or a patient with multiple occlusions would not be eligible for MIDCAB).
Cost:
OPCAB will be a cheaper operation relative to conventional CABG in several ways. Cost reduction occurs due to:
On average, OPCAB is around 25% cheaper than CABG. At the University of Maryland Medical Center, conventional CABG costs around $20,000 whereas OPCAB is around $12,000.
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