Dec 4, 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 features important information, that will aide identification of children with latent rheumatic heart disease, who are at highest risk of unfavorable outcomes. This important discussion is coming right up after these summaries.
The first original paper this week describes the largest study to date to examine payer approvals and rejections of PCSK9 inhibitor therapy, and describe the patient characteristics associated with successful prescribing. First author, Dr. Hess, corresponding author Dr. Yeh and colleagues from Beth Israel Deaconess Medical Center in Boston, Massachusetts, performed a retrospective descriptive cohort study utilizing nationwide pharmacy claims linked to electronic medical records from a nationwide data warehouse. The data set included over 220 million patients from all 50 states, and all pair types with more than 5,000 distinct health plans. PCSK9 inhibitor prescriptions were submitted for 51,422 patients in the pharmacy data set.
The authors found that among patients who were prescribed a PCSK9 inhibitor, 47% were approved for coverage by the payer. Variables that were associated with approval included age above 65 years, history of atherosclerotic cardiovascular disease, prescription by a cardiologist or a non-primary care provider, statin intolerance, longer statin duration, and non-commercial payers. Interestingly, higher LDL cholesterol levels were not associated with higher approval rates. Commercial third-party payers had the lowest approval rates of 24 from 4% and Medicare had the highest at 60.9%. Thus, rates of approval for PCSK9 inhibitor therapy are low, even for patients who appear to meet labeled indications. While a combination of clinical characteristics increase the likelihood of approval, payer type is the most significant factor.
The next study identifies a novel mitochondrial localized protein that plays a role in cardiac dysfunction, remodeling, and heart failure. This protein is FUN14 domain-containing 1, or FUNDC1, a highly conserved outer mitochondrial membrane protein. In today's study, first author, Dr. Wu, co-corresponding authors, Dr. Xie and Zou from Georgia State University, and their colleagues, showed that in cardio myocytes, FUNDC1 bound to inositol 1, 4, 5-triphosphate type 2 receptor, to form mitochondria-associated endoplastic reticular membranes.
These, in turn, modulate a calcium release from endoplasmic reticulum into mitochondria and the cytosol. FUNDC1 deletion lowered the levels of calcium in both mitochondria and the cytosol. A reduction at intracellular calcium resulted in mitochondrial fusion, mitochondrial dysfunction, cardiac dysfunction, and heart failure. In summary, this study identifies FUNDC1 as a novel mitochondrial localized protein that plays a role in maintaining mitochondrial dynamics, and cardiac function, and may therefore be a therapeutic target in heart failure.
The next study takes a deep dive into the J-Curve phenomenon of systolic blood pressure by providing an experimental approach to an observational paradigm. First and corresponding author, Dr. Kalkman, from University of Amsterdam and colleagues assess the association between on-treatment systolic blood pressure levels, cardiovascular events, and all cause mortality in patients randomized to different systolic blood pressure targets in the pool database of the SPRINT-6 and ACCORD trials. For both the intensive blood pressure target of less than 120 millimeters mercury, and the conventional target of less than 140 millimeters of mercury, the authors found an identical shape of the J-curve was present with a [inaudible 00:04:44] for cardiovascular events and all cause mortality just below the systolic blood pressure target.
The advantage of the intensive treatment group persisted at any level of the difference between the intended target and the achieved blood pressure targets. As discussed in an accompanying editorial by Dr. Verdecchia from Hospital of Assisi in Italy, these data suggest that if two patients achieve identical low values of blood pressure during treatment, prognosis is expected to be better in the patient actually targeted to achieve low values. Conversely, the outcome might be worse in the patient randomized to a higher blood pressure target, because low values in this case possibly reflect masked or unmasked confounders linked to a poorer outcome.
Thus, physicians should not be reluctant in lowering blood pressure in their patients because of an expected detrimental effect of BP reduction on death or major cardiovascular events. Rather, they should carefully monitor the possible occurrence of other adverse effects linked to blood pressure lowering, such as syncope, renal impairment, or electrolyte disturbances. This study further suggests that the benefit or risk associated with intensive blood pressure lowering treatment can only be established via randomized clinical trials and should not be extrapolated from observational data.
The final study establishes a causal link between dysregulated Tryptophan metabolism and abdominal aortic aneurysm. In a series of elegant mouse experiments from first author, Dr. Wang, two corresponding authors, Dr. Liu] and Ding from Georgia State University in Atlanta, Georgia, the authors establish that 3-Hydroxyanthranilic acid or 3-HAA, a key Tryptophan catabolite of the Angiotensin II induced abdominal aortic aneurysm in vascular smooth muscle cells was indeed responsible for Angiotensin II induced abdominal aortic aneurysm in Vivo. 3-HAA activated nuclear factor kappa-B transcription factor, promoted matrix metallopeptidase 2 expression in vascular smooth muscle cells. Human abdominal aortic aneurysm samples had stronger staining with the antibody against 3-HAA, than those in the adjacent non-aneurysmal aortic sections of these samples.
The identification of 3-HAA in Angiotensin II triggered abdominal aortic aneurysm and in human patients with abdominal aortic aneurysms, suggests that Tryptophan derived metabolites may be a biomarker for abdominal aortic aneurysm diagnosis. Furthermore, agents that alter Tryptophan metabolism may have a therapeutic potential in preventing or treating abdominal aortic aneurysms. Well on that intriguing note, we're at the end of this week's summaries. Now, for our featured discussion.
Today's feature paper really reminds us that rheumatic heart disease remains the most common cardiovascular disease among the world's youth. These days, echocardiographic screening provides a promising tool for early detection. However, the utility of this tool really depends on knowing the natural history of screen detected rheumatic heart disease, so-called latent rheumatic heart disease. Now, that has remained clear until today's paper. I'm so pleased to have with us the first and corresponding author, Dr. Andrea Beaton, from Children's National Medical Center in Washington D.C., as well as Dr. Bongani Mayosi, Associate Editor from University of Cape Town, South Africa. Andrea, could you start by letting us know about your study and what you found?
Dr. Andrea Beaton: As you mentioned, over the last decade or so it's become clear that in addition to the substantial burden of clinical rheumatic heart disease that we see around the world in low and middle income countries, there's also an even larger burden of latent rheumatic heart disease or early rheumatic heart disease that we can see on echo. This brings up the question if echo screening might represent a very powerful tool for rheumatic heart disease control, but we can't move forward with that discussion until we understand the rate of progression of children who are found to have echo detected rheumatic heart disease, and if we can do something to intervene to prevent progression in that population.
That something is likely penicillin, which is known to prevent progression in clinical rheumatic heart disease. To start to address that question, we followed a large cohort of children who had been diagnosed with echo detected rheumatic heart disease through school-based screening in different areas of Uganda and had collected about 227 cases of children with latent rheumatic heart disease who had been in clinical followup between two and a half and almost six years.
Dr. Carolyn Lam: Great. Could you tell us what you found about the progression and risk factors perhaps of progression, which I think are most significant?
Dr. Andrea Beaton: Right, so this is the largest natural history cohort of children with latent rheumatic heart disease to date and four major findings emerged from our study. The first is that we find a lot of echo detected rheumatic heart disease in low income settings that is more advanced. What we found is that children, even if this is their first time of diagnosis at echo screening, if they had moderate to severe rheumatic heart disease on screening, if they had poor outcomes even if over a very short time period. In our study, children with moderate to severe disease, only 10% of those children improved over the study period and 10% had died after only two to five years of followup.
We also saw that kids with mild, but definite rheumatic heart disease, which is more criteria for rheumatic heart disease than borderline, showed worse outcomes. Although, both children with mild definite and borderline disease had substantial risk of progression. 25% progressed in the mild definite group and 10% in the borderline rheumatic heart disease group. That tells us that even with very minor changes on echo screening, there is substantial risk of progression to more severe rheumatic heart disease, because we had a larger cohort using a multi-variant model.
We also found that there were features of rheumatic heart disease that put children at higher risk of progression. In our cohort, if children had aortic insufficiency at the time of screening, or some specific morphological changes, or changes in the mitral valve at time of screening, then they had higher risk of progression. While older age at time of screening showed a protective effect against progression.
Dr. Carolyn Lam: Wow. Andrea, congratulations on this remarkable study and you've highlighted so many important public health messages just in this one study. Bongani, what do you think was the most important or significant finding?
Dr. Bongani Mayosi: The most important finding is the reflection of the progression even in the mild and borderline cases. I think there has been an understanding that the definite cases do have a higher rate of progression and on top of that, I think showing the fact that there are some predictors that can be detected on echo is also very useful. Those with more advanced disease categories, those with younger age, as well as those with morphological valve abnormalities, I think those are very, very valuable points. Of course, the other point that is not all here is the fact that the majority of the initial progression appears to occur early and this is brought out in this study because of the serial echos that were done, which is again, another very valuable and a unique aspect of the study.
Previous studies have only done an echo at the time of diagnosis and perhaps an echo at the end of the followup period. I think that these features really make this study a valuable one. There is one question though that I wanted to put to Andrea, the issue of auscultation is one that we realized very early was not very useful for screening patients with latent rheumatic heart disease. We missed too many. I'd like to ask you now, once we've identified patients with latent disease, do you think auscultation of those patients could in fact identify the ones with clinical disease? Presumably, the more severe aortic regurgitation, mitral regurgitation, may be audible using a stethoscope? In other words, now shifting the role of the stethoscope not so much for diagnosis, but for risk stratification. I just want to know if you looked at this issue at all in this particular cohort?
Dr. Andrea Beaton: That's a really good question, Professor. We did not specifically look at the role of auscultation in this cohort. Although, it stands to reason that children with moderate to severe rheumatic heart disease, which by our definitions meant at least moderate to severe regurgitation at one of the valves, or presence of mitral stenosis would be audible. In that way, I think separating out children with moderate to severe disease, versus children with mild definite and borderline disease, would be quite possible and reasonable by auscultation.
My worry with the use of auscultation is I don't think it would separate out well children with mild definite disease, who by definition could have no more than mild regurgitation at any one valve, from children with borderline disease. Whether that distinction is important, I think still remains to be understood, but it would not be a very sensitive way to follow children until they had progressed to the point of having much more significant disease. I think echo still remains incredibly sensitive compared to auscultation for minor progressions, which to be clear, were included here as counting as progression of disease, even minor changes on echocardiographic evaluation.
Dr. Carolyn Lam: I have a question along the same lines Andrea, what kind of expertise was required for these echocardiographic screening procedures, both of the acquisition and then the interpretation? I do notice that you had a trained pediatric cardiologist with expertise in rheumatic heart disease who actually re-reported some of the echos. Do you think this is needed? What do you think about that?
Dr. Andrea Beaton: This is a complicated question, but a good one. A lot of the research that we've done outside of this paper has been looking at the ability to task shift echo screening, so to have non-physicians, not experts conducting echo screening. What we found across the board, as well as other groups around the world have found, is that you can train non-experts in a relatively short period of time to both screen and diagnose, at least on a screening basis, the presence of absence of rheumatic heart disease. For the purposes of this study, we're using very precise and very detailed diagnosis. According to the World Heart Federation criteria, which do really require experts to interpret.
Dr. Bongani Mayosi: The other issue, Andrea, which you highlight in the paper is the whole issue of the definition of progression, and regression, and the fact that there isn't consensus in the field about how we handle that, which results in papers not being comparable among each other. What do you suggest is the way of taking this forward so that we can build a consensus and a way of actually following up this patients that will be comparable between studies?
Dr. Andrea Beaton: That's a really important question and something we struggled with while we were writing this paper. You'll note in our paper that we reported it in two different ways because we couldn't come to a consensus and we thought both had some legitimate importance. Most of the papers in this field have reported the groups as progression and as stable lumped together, versus regression or improvement of disease. We felt the most important endpoint and something we had the numbers to power, was progression by itself. How many children were getting worse over the study period? In one sense, we powered it progression, versus stable plus regression, trying to dichotomize it still.
Then on the other hand, we thought that it was important if you had mild definite disease, even if you remained stable and mildly definite, and so we reported differently on the second outcomes based on if you had definite disease where we grouped progression and stable together, versus if you had borderline where we only counted true progression as a change for the worse. I don't have the perfect answer of how this should be reported. Although, I think the more granular we can be as we report these studies going forward, the more we can separate out the data that is reported to make it comparable. A lot of the previous papers, I think, lack the granularity needed to compare in different ways.
Dr. Carolyn Lam: We're coming to the end of our time, so may I just wrap up by asking Andrea, what do you think are the next steps?
Dr. Andrea Beaton: That's a good question and something I feel strongly about. Another part of our paper showed that the other incredibly important outstanding question is if we can find these kids, can we change what happens to them over time, and does penicillin do that? Even with our large cohort of patients, we couldn't determine the effect of penicillin on progression or trajectory of these children over this time period. It's something that now that we have large numbers of children and still can't come to a conclusive response, I think warrants a randomized control trial to look at the effect of penicillin on children with echo detected rheumatic heart disease, because that's really what's going to drive the policy on if echo screening makes sense as a public health policy to reduce the global rheumatic heart disease burden.
Dr. Carolyn Lam: I'm sure listeners out there, you've appreciated this as much as I have. Tune in again next week.