Nov 22, 2021
Please join first author Yuan Lu and Guest Editor Jan Staessen as they discuss the article "National Trends and Disparities in Hospitalization for Acute Hypertension Among Medicare Beneficiaries (1999-2019)."
Dr. Carolyn Lam:
Welcome to Circulation on the Run: your weekly podcast, summary and backstage pass to the journal and it's editors. We're your co-hosts. I'm Dr. Carolyn Lam, associate editor from the National Heart Center and Duke National University of Singapore.
Dr. Greg Hundley:
And I'm Dr. Greg Hundley, associate editor, and director of Pauley Heart Center at VCU health in Richmond, Virginia.
Dr. Carolyn Lam:
Greg, today's feature discussion is about the national trends and disparities and hospitalizations for hypertensive emergencies among Medicare beneficiaries. Isn't that interesting? We're going to just dig deep into this issue, but not before we discuss the other papers in today's issue. I'm going to let you go first today while I get a coffee and listen.
Dr. Greg Hundley:
Oh, thanks so much, Carolyn. My first paper comes to us from the world of preclinical science and it's from professor Christoff Maack from University Clinic Wursburg. Carolyn, I don't have a quiz for you, so I'm going to give a little break this week, but this particular paper is about Barth syndrome. Barth syndrome is caused by mutations of the gene encoding taffazin, which catalyzes maturation of mitochondrial cardiolipin and often manifests with systolic dysfunction during early infancy. Now beyond the first months of life, Barth syndrome cardiomyopathy typically transitions to a phenotype of diastolic dysfunction with preserved ejection fraction, one of your favorites, blunted contractile reserve during exercise and arrhythmic vulnerability. Previous studies traced Barth syndrome cardiomyopathy to mitochondrial formation of reactive oxygen species. Since mitochondrial function and reactive oxygen species formation are regulated by excitation contraction coupling, these authors wanted to use integrated analysis of mechano-energetic coupling to delineate the pathomechanisms of Barth syndrome cardiomyopathy.
Dr. Carolyn Lam:
Oh, I love the way you explained that so clearly, Greg. Thanks. So what did they find?
Dr. Greg Hundley:
Right, Carolyn. Well, first defective mitochondrial calcium uptake prevented Krebs cycle activation during beta adrenergic stimulation, abolishing NADH regeneration for ATP production and lowering antioxidative NADPH. Second, Carolyn, mitochondrial calcium deficiency provided the substrate for ventricular arrhythmias and contributed to blunted inotropic reserve during beta adrenergic stimulation. And finally, these changes occurred without any increase of reactive oxygen species formation in or omission from mitochondria. So Carolyn what's the take home here? Well, first beyond the first months of life, when systolic dysfunction dominates, Barth syndrome cardiomyopathy is reminiscent of heart failure with preserved rather than reduced ejection fraction presenting with progressive diastolic and moderate systolic dysfunction without relevant left ventricular dilation. Next, defective mitochondrial calcium uptake contributes to inability of Barth syndrome patients to increase stroke volume during exertion and their vulnerability to ventricular arrhythmias. Lastly, treatment with cardiac glycosides, which could favor mechano-energetic uncoupling should be discouraged in patients with Barth syndrome and left ventricular ejection fractions greater than 40%.
Dr. Carolyn Lam:
Oh, how interesting. I need to chew over that one a bit more. Wow, thanks. But you know, I've got a paper too. It's also talking about energetic basis in the presence of heart failure with preserved ejection fraction, but this time looking at transient pulmonary congestion during exercise, which is recognized as an emerging and important determinant of reduced exercise capacity in HFpEF. These authors, led by Dr. Lewis from University of Oxford center for clinical magnetic resonance research sought to determine if an abnormal cardiac energetic state underpins this process of transient problem congestion in HFpEF.
Dr. Carolyn Lam:
To investigate this, they designed and conducted a basket trial covering the physiological spectrum of HFpEF severity. They non-invasively assess cardiac energetics in this cohort using phosphorous magnetic resonance spectroscopy and combined real time free breathing volumetric assessment of whole heart mechanics, as well as a novel pulmonary proton density, magnetic resonance imaging sequence to detect lung congestion, both at rest and during submaximal exercise. Now, Greg, I know you had a look at this paper and magnetic resonance imaging, and spectroscopy is your expertise. So no quiz here, but could you maybe just share a little bit about how novel this approach is that they took?
Dr. Greg Hundley:
You bet. Carolyn, thanks so much for the intro on that and so beautifully described. What's novel here is they were able to combine imaging in real time, so the heart contracting and relaxing, and then simultaneously obtain the metabolic information by bringing in the spectroscopy component. So really just splashing, as they might say in Oxford, just wonderful presentation, and I cannot wait to hear what they found.
Dr. Carolyn Lam:
Well, they recruited patients across the spectrum of diastolic dysfunction and HFpEF, meaning they had controls. They had nine patients with type two diabetes, 14 patients with HFpEF and nine patients with severe diastolic dysfunction due to cardiac amyloidosis. What they found was that a gradient of myocardial energetic deficit existed across the spectrum of HFpEF. Even at low workload, the energetic deficit was related to a markedly abnormal exercise response in all four cardiac chambers, which was associated with detectable pulmonary congestion. The findings really support an energetic basis for transient pulmonary congestion in HFpEF with the implication that manipulating myocardial energy metabolism may be a promising strategy to improve cardiac function and reduce pulmonary congestion in HFpEF. This is discussed in a beautiful editorial by Drs. Jennifer Hole, Christopher Nguyen and Greg Lewis.
Dr. Greg Hundley:
Great presentation, Carolyn, and obviously love that MRI/MRS combo. Carolyn, these investigators in this next paper led by Dr. Sara Ranjbarvaziri from Stanford University School of Medicine performed a comprehensive multi-omics profile of the molecular. So transcripts metabolites, complex lipids and ultra structural and functional components of hypertrophic cardiomyopathy energetics using myocardial samples from 27 hypertrophic cardiomyopathy patients and 13 controls really is the donor heart.
Dr. Carolyn Lam:
Wow, it's really all about energetics today, isn't it? So what did they see, Greg?
Dr. Greg Hundley:
Right, Carolyn. So hypertrophic cardiomyopathy hearts showed evidence of global energetic decompensation manifested by a decrease in high energy phosphate metabolites (ATP, ADP, phosphocreatine) and a reduction in mitochondrial genes involved in the creatine kinase and ATP synthesis. Accompanying these metabolic arrangements, quantitative electron microscopy showed an increased fraction of severely damaged mitochondria with reduced crystal density coinciding with reduced citrate synthase activity and mitochondrial oxidative respiration. These mitochondrial abnormalities were associated with elevated reactive oxygen species and reduced antioxidant defenses. However, despite significant mitochondrial injury, the hypertrophic cardiomyopathy hearts failed to up-regulate mitophagic clearance.
Dr. Greg Hundley:
So Carolyn, in summary, the findings of this study suggest that perturbed metabolic signaling and mitochondrial dysfunction are common pathogenic mechanisms in patients with hypertrophic cardiomyopathy, and these results highlight potential new drug targets for attenuation of the clinical disease through improving metabolic function and reducing myocardial injury.
Dr. Carolyn Lam:
Wow, what an interesting issue of our journal. There's even more. There's an exchange of letters between Drs. Naeije and Claessen about determinants of exercise capacity in chronic thromboembolic pulmonary hypertension. There's a "Pathways to Discovery" paper: a beautiful interview with Dr. Heinrich Taegtmeyer entitled,"A foot soldier in cardiac metabolism."
Dr. Greg Hundley:
Right, Carolyn, and I've got a research letter from Professor Marston entitled "The cardiovascular benefit of lowering LDL cholesterol to below 40 milligrams per deciliter." Well, what a great issue, very metabolic, and how about we get onto that feature discussion?
Dr. Carolyn Lam:
Let's go, Greg.
Dr. Greg Hundley:
Welcome listeners to our feature discussion today. We have a paper that is going to address some issues pertaining to high blood pressure, or hypertension. With us, we have Dr. Yuan Lu from Yale University in New Haven, Connecticut. We also have a guest editor to help us review this paper, Dr. Jan Staessen from University Louvain in Belgium. Welcome to you both and Yuan, will start with you. Could you describe for us some of the background that went into formulating your hypothesis and then state for us the hypothesis that you wanted to address with this research?
Dr. Yuan Lu:
Sure. Thank you, Greg. We conducted this study because we see that recent data show hypertension control in the US population has not improved in the last decades, and there are widening disparities. Also last year, the surgeon general issued a call to action to make hypertension control a national priority. So, we wanted to better understand whether the country has made any progress in preventing hospitalization for acute hypertension. That is including hypertension emergency, hypertension urgency, and hypertension crisis, which also refers to acute blood pressure elevation that is often associated with target organ damage and requires urgent intervention. We have the data from the Center for Medicare/Medicaid, which allow us to look at the trends of hospitalization for acute hypertension over the last 20 years and we hypothesize we may also see some reverse progress in hospitalization rate for acute hypertension, and there may differences by population subgroups like age, sex, race, and dual eligible status.
Dr. Greg Hundley:
Very nice. So you've described for us a little bit about perhaps the study population, but maybe clarify a little further: What was the study population and then what was your study design?
Dr. Yuan Lu:
Yeah, sure. The study population includes all Medicare fee-for-service beneficiaries 65 years and older enrolled in the fee-for-service plan for at least one month from January 1999 to December 2019 using the Medicare denominator files. We also study population subgroups by age, sex, race and ethnicity and dual eligible status. Specifically the racial and ethnic subgroups include Asian, blacks, Hispanics, North American native, white, and others. Dual eligible refers to beneficiary eligible for both Medicare and Medicaid. This study design is a serial cross sectional analysis of these Medicare beneficiaries between 1999 and 2019 over the last 20 years.
Dr. Greg Hundley:
Excellent. Yuan, what did you find?
Dr. Yuan Lu:
We actually have three major findings. First, we found that in Medicare beneficiaries 65 years and older, hospitalization rate for acute hypertension increased more than double in the last 20 years. Second, we found that there are widening disparities. When we look at all the population subgroups, we found black adults having the highest hospitalization rate in 2019 across age, sex, race, and dual eligible subgroup. And finally, when we look at the outcome among people hospitalized, we found that during the same period, the rate of 30 day and 90 day mortality and readmission among hospitalized beneficiaries improved and decreased significantly. So this is the main findings, and we can also talk about implications of that later.
Dr. Greg Hundley:
Very nice. And did you find any differences between men and women?
Dr. Yuan Lu:
Yes. We also looked at the difference between men and women, and we found that actually the hospitalization rate is higher among females compared to men. So more hospitalizations for acute hypertension among women than men.
Dr. Greg Hundley:
Given this relatively large Medicare/Medicaid database and cross-sectional design, were you able to investigate any relationships between these hospitalizations and perhaps social determinants of health?
Dr. Yuan Lu:
For this one, we haven't looked into that detail. This is just showing the overall picture, like how the hospitalization rate changed over time in the overall population and by different population subgroups. What you mentioned is an important issue and should definitely be a future study to look at whether social determine have moderated the relationship between the hospitalization.
Speaker 3:
Excellent. Well, listeners, now we're going to turn to our guest editor and you'll hear us talk a little bit sometimes about associate editors. We have a team that will review many papers, but when we receive a paper that might contain an associate editor or an associate editors institution, we actually at Circulation turn to someone completely outside of the realm of the associate editors and the editor in chief. These are called guest editors. With us today, we have Dr. Jan Staessen from Belgium who served as the guest editor. He's been working in this task for several years. Jan, often you are referred papers from the American Heart Association. What attracted you to this particular paper and how do you put Yuan's results in the context with other studies that have focused on high blood pressure research?
Dr. Jan Staessen:
Well, I've almost 40 years of research in clinical medicine and in population science, and some of my work has been done in Sub-Saharan Africa. So when I read the summary of the paper, I was immediately struck by the bad results, so to speak, for black people. This triggered my attention and I really thought this message must be made public on a much larger scale because there is a lot of possibility for prevention. Hypertension is a chronic disease, and if you wait until you have an emergency or until you have target organ damage, you have gone in too late. So really this paper cries for better prevention in the US. And I was really also amazed when I compared this US data with what happens in our country. We don't see any, almost no hospitalizations for acute hypertension or for hypertensive emergencies. So there is quite a difference.
Dr. Jan Staessen:
Going further on that, I was wondering whether there should not be more research on access to primary care in the US because people go to the emergency room, but that's not a place where you treat or manage hypertension. It should be managed in primary care with making people aware of the problem. It's still the silent killer, the main cause of cardiovascular disease, 8 million deaths each year. So this really triggered my attention and I really wanted this paper to be published.
Dr. Greg Hundley:
Very nice. Jan, I heard you mention the word awareness. How have you observed perhaps differences in healthcare delivery in Belgium that might heighten awareness? You mentioned primary care, but are there any other mechanisms in place that heighten awareness or the importance?
Dr. Jan Staessen:
I think people in Belgium, the general public, knows that hypertension is a dangerous condition. That it should be well treated. We have a very well built primary care network, so every person can go to a primary care physician. Part of the normal examination in the office of a primary care physician is a blood pressure measurement. That's almost routine in Belgium. And then of course not all patients are treated to go. Certainly keeping in mind the new US guidelines that aim for lower targets, now recently confirmed in the Chinese study, you have to sprint three cells. And then the recent Chinese study that have been published to the New England. So these are issues to be considered. I also have colleagues working in Texas close to the Mexican border at the university place there, and she's telling me how primary care is default in that area.
Dr. Jan Staessen:
I think this is perhaps part of the social divide in the US. This might have to be addressed. It's not only a problem in the US, it's also a problem in other countries. There is always a social divide and those who have less money, less income. These are the people who fell out in the beginning and then they don't see primary care physicians.
Dr. Jan Staessen:
Belgium, for instance, all medicines are almost free. Because hypertension is a chronic condition prevention should not only start at age 65. Hypertension prevention should really start at a young age, middle age, whenever this diagnosis of high blood pressure diagnosis is confirmed. Use blood pressure monitoring, which is not so popular in the US, but you can also use home blood pressure monitoring. Then you have to start first telling your patients how to improve their lifestyle. When that is not sufficient, you have to start anti hypertensive drug treatment. We have a wide array of anti hypertensive drugs that can be easily combined. If you find the right combination, then you go to combination tablets because fewer tablets means better patient adherence.
Dr. Greg Hundley:
Yuan we will turn back to you. In the last minutes here, could you describe some of your thoughts regarding what you think is the next research study that needs to be performed in this sphere of hypertension investigation?
Dr. Yuan Lu:
Sure. Greg, in order to answer your question, let me step back a little bit, just to talk about the implication of the main message from this paper, and then we can tie it to the next following study. We found that the marked increase in hospitalization rate for acute hypertension actually represented many more people suffering a potential catastrophic event that should be preventable. I truly agree with what Dr. Staessen said, hypertension should be mostly treated in outpatient setting rather than in the hospital. We also find the lack of progress in reducing racial disparity in hospitalization. These findings highlight needs for new approaches to address both the medical and non-medical factors, including the social determinants in health, system racism that can contribute to this disparity. When we look at the outcome, we found the outcome for mortality and remission improved over time.
Dr. Yuan Lu:
This means progress has been made in improving outcomes once people are hospitalized for an acute illness. The issue is more about prevention of hospitalization. Based on this implication, I think in a future study we need better evidence to understand how we can do a better job in the prevention of acute hypertension admissions. For example, we need the study to understand who is at risk for acute hypertensive admissions, and how can this event be preempted. If we could better understand who these people are, phenotype this patient better and predict their risk of hospitalization for acute hypertension, we may do a better job in preventing this event from happening.
Dr. Greg Hundley:
Very nice. And Jan, do you have anything to add?
Dr. Jan Staessen:
Yes. I think every effort should go to prevention in most countries. I looked at the statistics, and more than 90% of the healthcare budget is spent in treating established disease, often irreversible disease like MI or chronic kidney dysfunction. I think then you come in too late. So of the healthcare budget in my mind, much more should go to the preventive issues and probably rolling out an effective primary care because that's the place where hypertension has to be diagnosed and hypertension treatment has to be started.
Dr. Greg Hundley:
Excellent. Well, listeners, we've heard a wonderful discussion today regarding some of the issues pertaining to hypertension and abrupt admission to emergency rooms for conditions pertaining to hypertension, really getting almost out of control. We want to thank Dr. Yuan Lu from Yale New Haven and also our guest editor, Dr. Jan Staessen from Louvain in Belgium. On behalf of Carolyn and myself, we want to wish you a great week and we will catch you next week on the run. This program is copyright of the American Heart Association, 2021. The opinions express by speakers in this podcast are their own and not necessarily those of the editors or of the American Heart Association for more visit aha journals.org.