Ani Anyanwu: In terms of nomenclature, the first thing, as Dr. Gilinov has said is, itís not very clear to define what is minimally invasive surgery. Is it avoiding a mid-line incision? Avoiding a full stenotomy? Using a small incision? A robot? I mean, what is minimally invasive surgery? And a lot of operations go under the name ďminimally invasiveĒ and because of that it is very difficult to know whatís really going on and analyze the effect of various operations because the invasiveness differs from one operation to another. So, some operations actually are no less invasive than a sternotomy and all minimally invasive operations are not the same.
This is a table from an excellent chapter written by Dr. Gilinov worth reading, which shows that looking at partial sternotomy, robotic, and mini thoracotomy approaches, they are very different operations. Some of them use central cannulation, the instrumentation is different, the bypass time is different, the learning curve is different. So these operations are different. And indeed, some minimally invasive operations are probably no less invasive than a sternotomy. Like in this patient you can see he had what was called a robotically assisted operation by the surgeon, but the scar is a big thoracotomy and is no different from the scar we used to re-repair his valve 3 months later because the valve repair failed.
So itís difficult to know what is minimally invasive surgery and all these operations make their way into the literature. So itís difficult to know the facts, but what Iím going to do is make some attempts to separate the myths from the facts and Iím going to attempt to answer 10 key questions about minimally invasive surgery. The same questions is: Is minimally invasive mitral surgery invasive? Iíll say the answer is yes. And that the invasion is probably not much different from the invasion of a sternotomy. I like showing this picture which is from Dr. Mohrís operating room, just to show that that there is a lot of invasion that goes on in a minimally invasive operation. There are lots of tubes, lots of clamps, lots of catheters; this is not minimally invasive. So we have to get rid of that name.
What minimally invasive surgery is, if it is done correctly, is a small scar, a very nice small scar, like this picture from Dr. Vernamanís operating room. But you can also get a small scar through a sternotomy if thatís what you are aiming for. So even the scar we have to be careful about and the principal difference might not be just the scar. We say we want to avoid a sternotomy, but if you look at the Cleveland experience, or the Brigham experience, where theyíve done half sternotomies, they have shown benefit over a full sternotomy. So splitting the sternum, or cracking the sternum, as cardiologists like to say, might not be as harmful as we think it is.
So the term ďminimally invasive surgeryĒ is really an oxymoron and ďless invasive surgeryĒ, the term ďless invasive surgeryĒ, might be more appropriate, but even then it probably applies to true endoscopic or robotic surgery. So the most invasive aspects of cardiac surgery, I would argue, donít relate to the incision. They relate to the other things that we do in surgery like cardiopulmonary bypass, anesthesia, and so on, and in some ways there is more invasiveness with minimally invasive surgery. As weíve heard, the bypass times are longer, you have new gadgets that you have to use, different perfusion. In some ways the invasion is less. For example, there is less tissue retraction and you donít have to do a wide pericardial opening, which might preserve biventricular function, so it can work both ways.
The second question is: Is minimally invasive surgery the same operation done through lesser access? No, itís not the same operation. It is a very different operation, and again, taken from Dr. Gilinovís chapter, you can see there are lots of differences between the various approaches. They are not the same. And if you are comparing a robotic and a sternotomy approach, for example, the perfusion is different Ė one is antegrade, one is retrograde. The clamping is different, the way the myocardium is cooled is different, our monitors, they are very different operations. Whether the difference matters is another question, but they are different.
So the reality is that we often shift our goalposts to fulfill less invasive cardiac surgery and there is invariable compromise, or change, in our principals and beliefs the smaller the incision gets. So there may also be benefits seen, such as better visualization, but all I say is that the two are not the same. So this, for example, is a paper from a group from I think, Tel Aviv, and they are showing for posterior leaflet pathology they are getting bypass times over 2 hours, but median sternotomy is just 80 minutes. So itís not the same operation being done, they are very different operations. And my concern is that these cut corners can result in failure of repair, although the data are not strong to show that, there are some indirect data that one can show to demonstrate that. So, thereís a tendency to make the pathology of the patient conform to the technique and make everyone have the same procedure despite their pathology.
The third question: Does minimally invasive surgery compromise repair rates? Iíll say the answer is yes. Maybe not in the most experienced hands, maybe not in those who have overcome their learning curve, but otherwise thereís both direct and indirect evidence that minimally invasive surgery compromises repair rates. Because it has to, by definition. Because certain repair techniques are more suited to congenital instrumentation and some valves are more difficult to repair. For example, rheumatic valves, congenital valves, heavily calcified valves, so it has to compromise. And the question is, can we replicate difficult repairs with minimally invasive heart surgery? And going back to the literature, the group at Vanderbilt, are one of the groups that have pioneered doing minimally invasive mitral valve operations, and their most recent publication, published just a few months ago, showed that out of over 500 patients, the repair rate was 56%, and for myxomatous degenerative disease the repair rate was 70%. So the repair rate is compromised in these patients. And even if you go to the very experienced center, this is a Fred Mohr center in Leipzig, for anterior leaflet or bileaflet problems, the repair rate is 90% with minimally invasive repair. So that young cardiologist who we were talking of this morning, if he went into a minimally invasive room, there is a one in ten chance that this cardiologist without symptoms comes out with a valve replacement. So itís not insignificant.
If one were to look at the high volume centers like Dr. Chitwoodís group, you wouldnít see much difference in bypass times, but there is a considerable number of patients undergoing replacement. We donít know why, but other groups show the same thing. This is Dr. Vannermanís group, earlier in his series, and there is about a 17% replacement rate for degeneration degenerative disease. So itís not insignificant and repair rates, I suspect in these surgeonís hands, would have been almost 100% if they were operating true sternotomy. And when we expand it to the rest of us that are tagging along much later than the pioneers, you see the same trend in that you have lower repair rates.
The fourth question: Is it possible in all patients? Dr. Gillinov has answered that; the answer is no. And I think that we have to be cautious in looking at the literature because patient selection and referral bias gives us an impression that people can get 100% repair with less invasive techniques. Well, the reality is that even in reference centers the patients that get these minimally invasive repairs are by and large simple pathologies.
This is going back again to Vannermanís series and you can see that most of the patients have posterior leaflet prolapsed, and in 83%, the repair was either a posterior repair or an annuloplasty, they were not rheumatic repairs. This is the Clevelandís series, published a few months ago, excellent series of over 700 posterior leaflet repairs, but if you focus on the robotic group, you can see that is a very young group of patients, 50% asymptomatic. I donít think there is anyone in this audience thatís operated on 50% asymptomatic. So if you take these results and think you will replicate them in your practice, youíll be surprised, because this is a different kind of population, which not all cardiac surgeons will see.
Itís certainly not reproducible, and this is from Trentoís group, you can see the same thing that most of their valve repairs by a robot are simple P2 prolapse fibroelastic deficiency. So patient selection and referral bias gives a skewed impression that minimally invasive surgery can be applied consecutively to all commons. Thatís not the case even in reference centers and most valves are simple pathology. And I suspect that many complex valves donít make their way into the minimally invasive operating rooms. As Dr. Gilinov says, not all patients are suited to minimally invasive approaches. For example, people with calcified aortas, and annular calcification, and so on.
So the fifth question: Is it reproducible by all surgeons? I would say no. Because it is a more difficult procedure to do. You need to be very skillful to do it. Letís not kid ourselves. Surgeons who can do this operation through small holes are by and large very highly skilled surgeons. Certainly like Dr. Chitwood who can achieve these results with 97% free from even mild regurgitation after surgery. But if you look at Trentoís results, you can see 10% of patients left the hospital with moderate or severe regurgitation. So itís not easy to replicate these results and the learning curve is unpredictable, which is a problem, and the reality is it takes about 100 cases to become proficient with minimally invasive surgery. Of course, if you are at the Cleveland Clinic it will take you like a month to achieve that. I mean, they did like 700 cases over 3 years, which is an amazing series. But look at Gammieís data with what Dr. Boling showed today, the median amount of minimally invasive heart surgeries in the United States is 3, so all of us in the audience are doing an average of 3 a year so it will take us a lifetime to achieve, to overcome that learning curve, so weíll always be learning.
So we shouldnít get run over the bandwagon or what happens is we end up harming patients, because the slower the learning curve is, the more harm that patients will succumb to. Is it the new standard? Iíll say, still not the new standard. Because the reality is thereís not much penetration of minimally invasive surgery and the growth is coming largely from established minimally invasive centers just like this series from New York University. You can see sternotomy stays constant and thereís a growth, usually from increased referrals, in the minimally invasive group. And certainly, in the United Sates as I have said, weíre doing an average of 3 per year so there is not really growth in the United States.
Does it have non-inferior outcomes? Iíll say no, it doesnít. And certainly, looking at the Cleveland series, it would suggest to you that there is not much difference in outcome between minimally invasive, but remember most of these patients, or a lot of them, had hemisternotomies. You canít extrapolate that to the right thoracotomy approach. So non-inferior results seen in selective reports though are not duplicated when we look at large data sets. For example, this paper presented by Dr. Gammie, which Dr. Gilinov has mentioned already, with about a double incidence of stroke and this was also shown from the New York State database a few years ago by Dr. Cheema, which showed also 2.4% double the risk of stroke with minimally invasive surgery. So itís real. And indeed, looking at this series from Grossi and colleagues at New York University, very interestingly, if they look at their series the real risk factor here is retrograde perfusion and not using an aortic cross clamp. If you donít clamp the aorta or perfuse retrogradely, at least in their series, there was a marked increase in risk of stroke after surgery.
And certainly, if you extrapolate that if you look at series where they routinely use retrograde perfusion without a clamp like the Vanderbilt series, you can see thy have a stroke rate of 3.6%, which is not, I mean itís not markedly high by any means, but whatís more worrying is that there were 4 fatal stokes. So they had 11 deaths in the series and 4 of them were due to stroke. So if they could get rid of the stoke, then the results would even be better.
There are other risks that come with minimally invasive surgery like phrenic nerve paralysis and post pericardial syndromes are more common. Also, bleeding for some reason, which is not clear, reoperations for bleeding seem to be more with minimally invasive surgery. It is not clear why that should be the case, but it seems to be the case even for minimally invasive aortic valve surgery. And there are also some complications that I introduced. For example, long herniations, which you donít see through a sternotomy. So this is a patient who had a long hernia and a hematoma from Fred Mohrís group. But what is striking to me is look at the size of this thoracotomy. The skin incision is tiny, but whatís underneath often is much bigger than the cosmetic white wash on top of it. So there are some patients too where sternotomy can be harmful, I must admit, and in these patients minimally invasive surgery might be beneficial, particularly for example the morbidly obese, and there are good data suggesting you get better outcomes in the morbidly obese with a minimally invasive approach.
Do patients recover quicker? Iíll say itís not proven. If you look at data this is data from the Mayo Clinic and Hargroveís group. You can see whichever hospital you went to you spent over 6 days in hospital. These are data from Japan, they were 9 days in hospital with minimally invasive approach. This is data from Chitwood, 6 days in hospital. So Iím not sure you spend shorter time in hospital and surely, there is not much evidence that pain is less, and I assure you that with a median sternum you can have patients back to full activity within a few weeks if you want to. And with modern methods of sternal closure like rigid fixation, patients can go back to full activity in 2 weeks if they want to.
Is the quality of repair similar? Iíll say itís not for most surgeons. Maybe so for high volume surgeons, maybe so for Dr. Chitwood as Iíve said, but it seems not to be the case for others. This is posterior leaflet repairs only and you can see 18% with moderate or severe regurgitation going home. Is it reproducible? Again, difficult to reproduce 10% of patients with moderate or severe regurgitation going home.
So is it better for the patient? I would say we donít know. I donít think it is. I think the only benefit is for cosmesis for the patient and the benefit is for marketing and growing our practices for ourselves because itís a good way to grow oneís practice, but I donít think it improves the chances for a good long or short term outcome and certainly thatís not shown in the literature. So what really is better for the patient is not a valve repair, it is a good valve repair and adherence to the universal principals which were taught to us by our pioneers, which is a good competent valve, a good surface of coaptation, and to preserve mobility and orifice of the valve.
How we get to the valve is of much less importance.
Thank you very much.