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Circulation on the Run

Oct 30, 2017

Dr. Carolyn Lam:               Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. I'm Dr. Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore.

                                                This week's journal is really special. It is the 2017 cardiovascular surgery-themed issue of "Circulation." To summarize this issue, I am so privileged to have the editors, Dr. Marc Ruel from University of Ottawa Heart Institute, as well as Dr. Timothy Gardner from Christiana Care Health System. Welcome gentleman.

Dr. Timothy Gardner:     Hello.

Dr. Marc Ruel:                   Hi, Carolyn. Glad to be here.

Dr. Carolyn Lam:               Thank you for another beautiful themed issue, Marc. I see that there are four general themes within this theme, if I may. The first of which are a collection of papers on coronary disease and coronary surgery. Could you maybe start by giving us an overview of that?

Dr. Marc Ruel:                   One of the main topics that have been looked at in the surgical-themed issue this year is coronary surgery. We all know well that 2016, 2017, the academic year was quite fertile in providing new information around coronary surgery, especially with the release of the ART trial had actually scientific sessions of the American Heart Association the last November with simultaneous publication.

                                                Interestingly, the cardiovascular surgical-themed issue has several coronary papers and one that deals with essentially with graft failure, if you will. There's an in-depth review written by Mario Gaudino, who is well known and does fantastic work at Cornell, who essentially put a team together looking at several aspects of coronary graft failure. I guess we can say that these are looked in quite great depth, and they deal with several aspects of what would lead to a coronary bypass graft to fail.

                                                First and foremost, Mario and the team look at the blood components. Then the artery and the native bed itself. Then they focus a lot on the conduit, not only the nature of the conduit being a venous versus arterial conduit, but also the way of storing the conduit prior to performing the bypass. Also, the technique that's used around the use of that conduit.

                                                Finally, I'd say that the review culminates with the patient bioreactor, for lack of a better term, aspect. Endothelial dysfunction in the patient with diabetes, age, gender, hypertension, dyslipidemia, etc., all these things that do act as a significant substrate for the fate of the conduit vessel.

                                                A very unique, I think, first-time, in-depth review that, certainly, the "Circulation" editorial team and reviewers were very excited about. I think this will be quite impactful and provide very, very detailed information for future research and future improvement and fate of the coronary graft conduits.

Dr. Carolyn Lam:               And, Dude, I agree. It's the new look at perhaps a classic, old, central surgery, the cardiovascular surgery. Very nice, indeed.

Dr. Marc Ruel:                   Precisely, thank you. We also have a couple of important, seminal original papers within the realm of coronary surgery. In fact, these also deal, to some extent, with the fate of conduits and certainly how they work in the patient population in long ago bypass surgery.

                                                One is a randomized control trial, a single center randomized control trial that was performed in South Manchester. It's called the VICO trial, a study comparing vein integrity and clinical outcomes. Essentially, the study looked at open vein harvesting versus two types of endoscopic vein harvesting for coronary artery bypass grafting.

                                                The study was performed at a single center in England with three sound methods, having three groups of 100 patients who were compared with regards to the vein harvest technique. The primary outcome was with regards to actual vein integrity, looking at muscular damage and endothelial function and integrity on microscopy.

                                                Surprisingly and actually quite reassuredly that there were very few differences between endoscopic vein harvest and open vein harvest. Certainly the investigators also looked, as one of their secondary outcomes, at quality of life. It was quality of life that was gained in patients who had endoscopic vein harvest versus those who had open vein harvest.

                                                Overall, there was no difference in major adverse cardiac events. Therefore, showing at least in an internally valid fashion that these investigators at their center could do endoscopic vein harvesting as well as open vein harvesting.

Dr. Carolyn Lam:               I know that there are other original research papers, perhaps. Would you like to highlight any of them?

Dr. Marc Ruel:                   Yes, for sure. Carolyn, there's also one more coronary surgery paper, which I wanted to highlight and that is the paper entitled, "Does Use of Bilateral Internal Mammary Artery Grafting Reduce Long-Term Risk of Repeat Coronary Revascularization?"

                                                This is a multi-center analysis with first author is Iribarne from Northern New England. Essentially, seven medical centers got together and took about 20 years of consecutive CABGs with a total number of 50,000 operations, or just shy of 50,000 operations.

                                                The median duration of follow-up was 13 years, and these patients were well matched together using a propensity matching scheme. I think this paper and this research is unique and of high impact. Even though it does have shortcomings of not being a randomized control trial, it is very welcome information, especially in light of the recent ART trial, which, as you know, did not show any difference at five years analysis between single and bilateral internal thoracic artery use.

                                                The particularity of the Iribarne paper is that it is a very large data set up with close to 50,000 patients. It is multi-centered, therefore, it is real life. It is a consecutive series. The patients are extremely well matched, and it is remarkable to hear that the patients, in fact, had no difference in mortality until about five years after the operation.

                                                As opposed to many previous series where single versus bilateral internal mammary grafting shows a mortality difference very early on, which always raises the suspicion of poor matching or confounding by indication, if you will, this paper did not have that.

                                                Finally, the follow-up was quite long and at about six years, there was really a mechanistic signal with regards to repeat revascularization events, which seemed to match the difference in late mortality. There was no difference in early and five-year mortality, but afterwards as repeat revascularization events started to occur more frequently in the single mammary group, this was matched by a difference in mortality, as well.

                                                I think a very useful, large, long follow-up mechanistically-based information that I think adds very significantly to the current information we have about bilateral versus single mammary use.

Dr. Carolyn Lam:               Thank you, Marc. Two original papers, highlighted, dealing with really very important modern controversies in this area. Open vein versus endoscopic vein harvesting, single versus bilateral mammary artery bypass. Excellent.

                                                Let's move on now to the next sub-theme, if you will. And that is the collection of papers on "Adult Congenital Heart Conditions," really, really an increasingly important and growing population that we're seeing. Tim, would you like to summarize maybe some of the highlights of the papers there?

Dr. Timothy Gardner:     The first paper, as you point out, is focused on adult patients with repaired tetralogy of Fallot. This series came from the UK and it examines the course of almost 60 patients, at a mean age of 35 years following a repair of tetralogy as infants or young children, developed right heart failure and required pulmonary valve replacement.

                                                This is a common scenario that we're seeing, successfully repaired children who appear to do well but as they get into their late 20s and 30s, their pulmonary valve function, which is often inadequate or not even present valve, require an intervention.

                                                The important learning here is that pulmonary valve replacement, either surgically or by catheter technique, was shown to be highly effective in salvaging right ventricular function. That is based on imaging studies as well as hemodynamic studies of right ventricular function. There was an almost, in this group of patients, almost an immediate reverse remodeling of the right ventricle after placement of the valve, that continued to improve over time.

                                                This was, I think, quite reassuring. There, historically, was a bit of a reluctance to operate on these patients as their right heart was failing, despite the fact that without some intervention to take the volume load off of the RV, the patients didn't do well. This is good news for an important group of patients who we are all seeing, who oftentimes present to the adult cardiologist because of this right ventricular failure problem. A nice, reassuring study.

                                                Actually, the other two congenital papers are, again, focused on the infant. They both deal with the infant with hypoplastic left heart syndrome or single ventricle pathology. The first paper seems sort of specialized in terms of its focus, "The Optimal Timing of Stage-2-Palliation for Hypoplastic Left Heart Syndrome." This was a report from the NIH Pediatric Heart Network. They had a single ventricle reconstruction trial.

                                                This network is comprised of about 10 North American centers, both in the U.S. and Canada and has provided excellent data about the management of pediatric heart disease but, in particular, the single ventricle trial has been excellent.

                                                In this particular paper, they look at the optimal timing for stage-2 repair. Just to remind ourselves, the first part of the three-stage treatment for hypoplastic left heart syndrome is the Norwood procedure, which has to be done shortly after birth, as the patent ductus arteriosus closes and converts, essentially, the single right ventricle into the systemic ventricle.

                                                The stage-2 comes along, usually done with a Glenn-type of shunt, increases pulmonary blood flow and stabilizes these infants until they can reach the age for, and the heart function for definitive repair. This has been a particularly difficult problem for the congenital heart surgeons. What is the optimal timing?

                                                This study, which involved over 400 patients, identified optimal timing for the second stage between three and six months after the Norwood. I think this was very reassuring, is reassuring or supportive for the congenital heart community in terms of both patients and also good evidence base that a delay of three to six months does, in fact, produce the best transplant-free survival.

                                                In fact, the other aspect of this observation was that infants who developed the need for another second stage operation sooner than that did not do well, and the reasons for the required earlier surgery could be failure of the initial operation or additional anatomic risk factors. But this, I think, was an important, large series, multi-center study that will prove to be very helpful in sorting out this complex timing of a three-stage repair.

                                                Just to comment, again, for readers who don't deal with infant congenital heart treatments very often, there's been a remarkable amount of success over the last two decades in salvaging and saving these very difficult infants with the hypoplastic left heart syndrome. In fact, an additional paper in this surgery-themed issue, comes from the UK and is, in fact, a report on the findings from the UK-wide audit of the treatment of infants with hypoplastic left heart syndrome.

                                                In fact, their findings, in this sort of real world, not in the Pediatric Heart Network trial group, is very similar. They found that infants who got to the second stage without additional refinement of the initial Norwood procedure and were able to be successfully treated with a Glenn shunt somewhere in the four-to-six-month age range, did well. They actually made the point that the anatomy was more of a determinant than anything else.

                                                I think that this particular review will reinforce what the congenital heart surgeons have learned about optimal timing for this three-stage treatment of what previously were unreconstructable children.

Dr. Carolyn Lam:               Thank you so much, Tim. Isn't it wonderful the way papers come in and they're actually complementary and consistent with one another. We're just so lucky to be publishing all of these great, high-quality, impactful papers in "Circulation."

                                                Moving on, the next paper actually reminds us why this is a cardiovascular surgery-themed issue and not just a cardiac surgery-themed issue. Didn't we just say that earlier, Marc? This one is on abdominal aortic aneurysm treatment. A population-based landscape of this. Could you tell us a little bit more about that one?

Dr. Marc Ruel:                   Absolutely. Carolyn, you're entirely right. We must remember that "Circulation" is also about peripheral vascular disease, saying this earlier, or cardiovascular surgery and anesthesia consult also when it encompasses vascular surgery. Precisely to that effect, one of the papers in our cardiovascular surgical-themed issue is a landscape population based analysis from Finland that looks at the incidence of abdominal aortic aneurysm between the years of 2000 and 2014.

                                                Finland has a population of about 5.5 million and remarkably has a very circumscribed healthcare system. They do not have an organized system of AAA care as some other countries have shown to have and potentially benefit from, but rather they have a treatment of this condition at several institutions, many of which may not be high volume.

                                                I think the paper is remarkable is that it is very well nested in terms of a population. It provides a comprehensive landscape of where this condition has evolved to over the last few years. Obviously, we see in the results from the authors that the mortality has decreased quite a bit, but also the incidence, probably as a result of better control of risk factors. And also the incidence of rupture outside the hospital.

                                                One thing that came out of this paper, as well, is a potential cohort of the benefits gained from developing an organized system of AAA care, from the reason that the mortality of AAA rupture in Finland was still quite high, despite this being a modern series. In fact, when you include ruptures, before arrival to hospital and at arrival to hospital, the overall mortality was almost 80% for ruptured AAA.

                                                Perhaps one message that comes out of this is that there may be a benefit in having specialized centers dealing with these conditions, especially as they are in the process of rupturing. One last observation was, obviously, the increasingly prevailing role of endoscopic vascular repair in the treatment of this condition, which, in fact, has now surpassed open repair as the dominant method of elective repair.

                                                I think, overall, a very comprehensive, well-nested, country-wide with good follow-up landscape of the AAA condition in a country that has essentially a similar socioeconomic status to much of the western world. Therefore, with external generalized ability to some extent.

Dr. Carolyn Lam:               Exactly, and contemporary data. I really enjoyed that you paired those with an excellent editorial, as well. Finally, before we wrap this up, I have to ask Tim to comment on this next paper, and it's on ventricular assist device malfunctions, I love the title, "It's More Than Just The Pump." Of course, as a heart failure physician, this one's very close to my heart. Forgive the pun. But, Tim, could you tell us about that?

Dr. Timothy Gardner:     This paper comes from the University of Pittsburgh and their artificial heart program. Robert Kormos is the first author and he's been one of the stalwart leaders in the use of LVADs and other pump devices. He reports on their experience with over 200 both HeartMate and HeartWare ventricular assist devices.

                                                It was interesting when we reviewed this paper by the editors, there was some thought that maybe this was a little too engineering focused and so on, but I think the point of the paper is that, as they say in the very first line in their report, reports of LVAD malfunction had focused on pump thrombosis.

                                                But they point out very appropriately that, in fact, controller failure, battery failure, cable failure and other causes of device failure, which can be critical and life threatening and so on, are engineering issues. It reminds us that when we're managing this difficult group of patients, and we're seeing many more patients today with getting LVADs than 10 or 20 years ago, we need to have the bioengineering abilities and resources available.

                                                Even the surgeon and the critical care physician who is dealing with these patients either has to acquire this kind of knowledge or capacity himself or herself, or needs to have a good bioengineer nearby.

                                                What's interesting, I think, that all of us define that these mechanical failures were more common in this pretty big experience than what we've more clinically worried about, which was thrombosis of the pump.

Dr. Carolyn Lam:               Exactly. That's so wonderful. And you know it just leads me to really thank you both, Marc and Tim, for this extraordinarily excellent selection of original research, state-of-the-art and perspective articles and editorials on congenital, coronary, vascular and heart failure surgery. This really appeals not just to the cardiovascular surgeons but really to the vast readership of "Circulation."

                                                Thank you for a wonderful themed issue and thank you for this great podcast.

Dr. Timothy Gardner:     Well, thank you.

Dr. Marc Ruel:                   Thank you very much, Carolyn.

Dr. Carolyn Lam:               Listeners, don't forget to tune in again next week.