Jul 18, 2016
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. Joining me in just a moment are Dr. James Gammie and Dr. Timothy Gardner to discuss our feature paper this week describing the first-in-human clinical experience with a novel transapical beating heart mitral valve repair.
First, here are the highlights of this week's journal. The first paper is from co-primary authors doctors Yoon, [Tsue 00:00:49], and [Cha 00:00:50] as well as corresponding authors Dr. [Che 00:00:55] and Dr. Kim from the Seoul National University College of Medicine. These authors examine mechanisms underlying diabetes-induced microvasculopathy, testing the hypothesis that Notch signaling in endothelial cells may play an important role in this condition.
The authors tested this hypothesis by inducing diabetes in eight-week-old adult mice using intravenous streptozotocin. They then modulated endothelial Notch signaling using chemical inhibitors in both wild type and transgenic mice. Results showed that the Notch ligand called Jagged-1 was markedly increased in endothelial cells of diabetic mice. Using endothelial specific Jagged-1 knocked down mice, they found that blocking Jagged-1 prevented diabetic microvaculopathy. Furthermore, using the induceable endothelium-specific Jagged-1 knocked down mice, blocking Jagged-1 even at four weeks after the establishment of diabetic microvaculopathy could reverse the condition.
In summary, these findings show that diabetes induces Jagged-1 over expression and suppresses Notch signalling in endothelial cells leading to diabetic microvaculopathy in adult mice. The clinical implications are that dysregulated intercellular Notch signalling may therefore represent a novel molecular target in the treatment of diabetic retinopathy.
The next study by Dr. Smith and colleagues at the Leiden University Medical Center in the Netherlands evaluated the association between LDL cholesterol variability and four cognitive domains at 30 months in the 4428 participants of the prosper study.
Results showed that a higher LDL cholesterol variability was associated with lower cognitive test performance for intermediate and delayed memory-related tasks, selective attention, and processing speed. Higher LDL cholesterol variability was also associated with lower cerebral blood flow and greater white matter hyperintensity load in an MRI substudy of 535 patients.
In addition to being independent of the mean LDL cholesterol levels and of clinically overt cardiovascular diseases, these associations were present both in the placebo and pravastatin treatment [inaudible 00:03:43] of the prosper trial suggesting that the findings did not mearly reflect pleiotropic effects of statins or of nonadherence.
The study importantly provides the first observational evidence that lipid variability, not just absolute or mean values, but the variability, maybe of importance to neurocognitive function and thus contributes while understanding potential pathways of neurocogniticve decline.
The next study is by first author, Dr. [Huh 00:04:19], and corresponding author, Dr. Ralph, from the Menzies School of Health Research Charles Darwin University in Australia. These authors aimed to investigate the long term outcomes from acute rheumatic fever and rheumatic heart disease.
They achieved this aim by using linked data between the rheumatic heart disease register, hospital data, and death register for residents of the northern territory of Australia, and examined 1248 patients with rheumatic heart disease as well as 572 patients with acute rheumatic fever in the period 1997 to 2013.
The main findings were that in the first year after an acute rheumatic fever episode, the incidents of progression to rheumatic heart disease was 10 times higher than acute rheumatic fever recurrence; 10% of rheumatic heart disease patients had severe disease at diagnosis. The presence of comorbidities was associated with higher incidence of rheumatic heart disease complications and mortality. In particular, comorbid renal failure and hazardous alcohol use accounted for 28% of the access indigenous mortality.
These findings have global relevance for settings with high acute rheumatic fever, rheumatic heart disease rates and really emphasized the need for integrated chronic disease management strategies for these patients.
The final paper is by first author Dr Bettencourt, corresponding author Dr. Blankstein, and colleagues from Brigman and Women's Hospital in Boston, Massachusetts. These authors sought to answer the question what is the most appropriate score for evaluating the pretest probability of obstructive coronary artery disease?
To answer the question, the authors compared the Diamond-Forrester score with the two CAD consortium scores recently recommended by the European Society of Cardiology, and they did this in 2274 consecutive patients without prior CAD referred for coronary CT angiography. CT angiography findings were used to determine the presence or absence of obstructive CAD defined as 50% or more stenosis.
Here's a refresher of the different probability scores. The Diamond-Forrester score is calculated based on chest pain type such as non-anginal, atypical or typical angina, gender, and age. The first CAD consortium model score called CAD consortium basic is also based on these factors, but was developed using more advanced statistical modeling strategies which were not available when the Diamond-Forrester model was derived. Additionally, the population had a lower prevalence of disease than the original Diamond-Forrester derivation cohort.
The second CAD consortium score called CAD consortium clinical included the same characteristics as CAD basic, but also included the following clinical risk factors; diabetes, smoking status, hypertension, and dyslipidemia. Moreover, the presence of typical chest pain was weighted less in diabetics compared to nondiabetics in the CAD clinical score. Results showed that among symptomatic individuals referred for coronary CT angiography, the CAD consortium clinical pretest probability score demonstrated improved calibration and discrimination for the prediction of obstructive CAD compared to the Diamond-Forrester classification.
Driving home the clinical implications of this, the authors applied these observed differences in pretest probability of obstructive CAD to guidelines-based patient management algorithms and projected that the use of the newest score could decrease the proportion of individuals in whom testing would be recommended and increase the yield of diagnosing obstructive CAD.
Those were the highlights of these weeks issue. Now, for our feature paper. Our feature paper today is about the first-in-human clinical experience with the transapical beating heart mitral valve repair using a expanded polytetrafluoroethylene chordal insertion device. We're really lucky today to have the first and corresponding author, Dr. James Gammie from the University of Maryland Medical Center as well as Dr. Timothy Gardner, associate editor from Christiana Care Health System to discuss this exciting paper. Welcome, both of you.
James, may I start with you? What an exciting title, a first-in-human experience, and this is really sounding very reminiscent of our experience with TAVR and aortic stenosis valves. Could I ask you, with so many exciting things, what is it about the results that excited you most?
This is an exciting project in that we believe it affords a new treatment option for patients with degenerative mitral regurgitation. We believe that this is a less invasive way of achieving surgical grade reduction of mitral regurgitation. This is a project which has involved a great number of people on our team both within the university and then within Harpoon Medical, as well as our colleagues in Europe to bring this device from an idea which was asked more than a decade ago into a clinical experience.
It really rose out of our recognition in particularly my own practice that virtually, every patient with degenerative mitral regurgitation could be fixed with ePTFE or Gore-Tex neo-chords, and the question became how can we place neo chords on a prolapsed mitral leaflets without doing open heart surgery?
We begin working on that in the laboratory a number of years ago and went through a variety of prototypes, and ultimately, came up with this idea where we could use a 3 millimeter shafted instrument with a specially designed wrap of Gore-Tex on a 21-gauge needle such that we could land on the underside of the mitral leaflet, deploy device, and create a specially designed knot on the atrial surface of the leaflet, and that would anchor the ePTFE on the leaflet. We could repeat that a few times transapically and then adjust the length of those chords in real time using transesophageal echo guidance.
We got this to work in the laboratory and we had hoped that we would have some modest success in humans, but we've been quite pleasantly surprised that it has just worked and we've outlines this initial clinical experience in the manuscript.
First of all, I'd just like to pick up on the point that this is degenerative mitral regurgitation, so this is limited to the primary mitral regurgitation, not secondary?
That's correct and we know that right now, at least in North America, that two-thirds of mitral valve operations are done for degenerative disease. That's correct.
I think a lot of the audience out there is going to be wondering how this new technique compares to the MitraClip. Could you tell us a little bit more about that?
I do MitraClip as well, so I think I'm well positioned to comment on the differences. The Harpoon device right now is still in operation. It does require a small one or two-inch incision. We anticipate it's going to be a thoracoscopic approach in the very near future and then, beyond that, we would hope to extend it to a transcatheter approach. That's one difference.
The MitraClip now is certainly across the world. It's used predominantly for functional mitral regurgitation. In our own experience, it seems to work best for functional mitral regurgitation and as you know, there are anatomic limitations for MitraClip in degenerative disease. The MiraClip replicates the LCRA surgical approach and I think what we've learned from all the less invasive approaches to treat mitral valve disease is that we have to respect what we've learned from our surgical experience, and we know that the LCRA approach works best when it's combined with an annuplasty ring, and certainly, the MitraClip, again, is mostly this perfunctional MR.
Another point I'd bring up is that the experience with MitraClip has been that when you place a MitraClip, you get a fairly strong fibrous reaction and in most of the series, it's not been possible to then go back and surgical repair the valve, but you have to do a replacement because you've compromised the leaflets. Our own approach were simply putting Gore-Tex sutures in the leaflets and we believe that one advantage is that we're not burning any bridges, and that you can go back and do an open repair of you had to.
In our experience, you asked about our results, we had great results in 10 out of 11 of our patients. One patient did require a reoperation. Actually, one of the chords had come untied on the surface in that patient. We were able to go ahead and do a repair and we saw as we had anticipated it based on our animal experience, there was not much compromised to the leaflets.
One of the advantages of our approach is that we can titrate the length to the Gore-Tex chords to optimize the amount of coaptation and maximize the quality of the repair, and that's something that we can't do an open cardiac surgery, and one of the challenges of mitral valve repair is that you have to figure out how long to make those chords while the heart is arrested and placid, and that's one of the challenges in why mitral valve repair is certainly some degree of an art to doing that.
What we've found is that the imager is incredibly important, and so we've teamed up with our echocardiography colleagues, and they really provide essential input into the procedure, and it's done not looking directly at the valve, but looking up at the screens. I think as surgeons, with this procedure, we're moving more into almost becoming interventionalists.
Thank you, James. That was so exciting. Tim, I have to bring you into this now. Now that James has said they're becoming like the interventionalist. Back to my original comment of TAVR and aortic stenosis, are we witnessing history in the making now? You invited an editorial by Dr. Michael Mack and his title was very provocative, Transcatheter Treatment of Mitral Valve Disease. Is it deja vu all over again? What are your thoughts?
I think this is an exciting report and I think that this is the wave of the future. I agree completely with Michael Mack that we are beginning to see interventions for mitral valve disease that are effective, less invasive, in some instances catheter based, but this is just the beginning. In fact, mitral valve disease is somewhat more complex even than aortic stenosis, but this type of experience and the ingenuity and the technical prowess, and the ability to do this minimally, invasively, and so on really portend a whole new era.
I agree with Jim. This is sort of the common ground between the interventional structural cardiologist and the surgeon, and we're becoming even more entwined, more collaborative, and more mutually supportive. We are in a new era and I think over those next decade or so, we're going to see this and similar, and even different procedures tried and proven to be useful for the variety of mitral valve disorders that we encounter. Perhaps the era of the full sternotomy for fairly straightforward, single, focused operations will become something of a thing of the past.
That's beautifully put. James, with that comment, what are the next steps?
As we said in the manuscript, this isn't barely experience and we're continuing to learn as we move [inaudible 00:17:07] to the clinical arena. We are currently in the midst of a CE Mark trial in Europe. We rolled it out to eight separate centers. As we approve clinical experience, we will learn more about precisely which patients work best with this approach and we will accrue longer term data. We now have a number of patient out to a year with stable results and so, as the numbers go up, we'll do that, and then we anticipate a randomized trial in the United States in the early to mid portion of 2017 where we'll compare this approach to conventional open cardiac surgery.
That's fantastic. Thank you so much to both of you, gentlemen, for joining me on our podcast today.
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