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Ann Thorac Surg 1998;66:55
© 1998 The Society of Thoracic Surgeons
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Discussion |
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 Top Discussion |
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The other question would be, from your experience, are there any patients who you would predict on the basis of their preoperative angiography you would not offer a MIDCABG to for technical reasons that you have learned from this procedure?
Is there any special equipment or setup that is required to do this over and above buying the catheters?
You answered what the worth of the doctor was, but it was kind of your gut feeling. Thanks for a very nice presentation.
DR ELBEERY: In terms of cost of the catheters, they are relatively inexpensive. They are available commercially now, and there is nothing that was designed special for this procedure. The whole system that we use is less than $100.
And as I said, we use a fluoroscopy unit that is standard in our operating room for use on peripheral arteriograms and cholangiography, and this appears to be adequate. There is a newer OEC unit that is basically a mobile cardiac catheterization laboratory that is becoming available now, which should give even better pictures, but I am not sure that it is necessary. Based on the relatively common findings of spasm and edema, we were just looking for a good flow versus no flow, essentially. A 30% stenosis was ignored.
In terms of patient selection for MIDCABG, our policy has been to offer the procedure to anyone in need of a single LAD graft. Although there are a fair number of patients with distal disease in the left anterior descending who are not good MIDCABG candidates, they often can be grafted via the minimally invasive approach. At the same time, I have found no increased morbidity if conversion to standard coronary artery bypass grafting is required. We have converted approximately 12 patients who now have a median sternotomy and small left anterior thoracotomy and they have all done fine. They all still received mammary artery bypass grafts. So I do not think I have done them a disservice.
DR TODD L. DEMMY (Columbia, MO): Have your findings in arteriography made you think about applying that to your patients with standard coronary bypass?
I use the duplex that shows increased diastolic flow. Do you think use of that plus your echocardiography in your assessment might have improved your sensitivity and specificity?
DR ELBEERY: We have not applied it to standard coronary artery bypass grafting, although I am presently working on a protocol to do that. I think it would be an interesting study to see whether patients done on cardiopulmonary bypass have the same spasm and changes in their grafts that we see in the off-pump cases.
There are other noninvasive systems, the transonic Doppler and duplex systems, and these probably would increase the sensitivity slightly, but I do not think they would give us the 100% reliability that we really want. It has been my experience that when these devices give a good signal that you are happy with them, but when you have a poor signal it is difficult to distinguish whether your signal is poor because there is not a good acoustic window or whether you actually have a graft problem.
DR DIMITRI NOVITZKY (Tampa, FL): I do not do MIDCABGs but I do total myocardial revascularization off cardiopulmonary bypass on a beating heart. I have performed this operation on 130 patients, and the mean number of grafts per patient is about 2.9. I absolutely agree on the need of having a noninvasive diagnostic method that will allow us to send the patient back to the intensive care unit with a patent graft. I have used Doppler echocardiography in the way that you have described, and in my experience, I have not found this to be a reliable method. Because of the graft elasticity, even in the presence of significant distal anastomotic stenosis, you can have Doppler signals from the graft. The proximal signals may show an equal systolic and a diastolic component. In the event Doppler echocardiography is used as a tool for coronary artery graft patency, the most important signal is the diastolic component. This must be loud and clear. In the correlation between the Doppler signal and the use of the flowmeter, the latter has to be the most reliable tool. Possibly the combination of both techniques is the ideal noninvasive method for arrest of the patency of coronary artery bypass graft. Whenever the flow in a vessel of 2.0 mm is not more than 20 mL/min, I think the anastomosis should be redone. Furthermore, to asses the blood flow, I inject the nitroglycerin directly into the graft and measure the flow through the graft again. Usually the blood flow increases over 50% to 100% of the previous flow. If this is not observed, something may be wrong technically with the distal anastomosis.
DR ELBEERY: I would agree with those comments. We do not inject nitroglycerin into the graft. And the transonic flow probe requires you to skeletonize a mammary artery, which I prefer not to do, unless I have to for some reason; that is the main reason we did not use that on all the cases. It also requires, again, a very good fit between the probe and the graft, and sometimes that is difficult to obtain.
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