May 1, 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 Doctor Carolyn Lam, associate editor for the National Heart Center and Duke National University of Singapore. Our feature paper today presents the first information on the impact of cardiovascular health in middle age and the burden of mobility in older age. This exciting data is from the Chicago Heart Association study. First, let me give you your summary of this week's journal.
The first study tells us that patients with long QT syndrome type II are at increased risk of hypoglycemia. First author, Doctor Hilton Cavallius, co-corresponding authors Doctor Tarakov and Hanson from University of Copenhagen, Denmark, noticed that loss of function mutations in HERG, which encodes the voltage gate at potassium channel 11.1, causes long QT syndrome II, but that the specific voltage gate at potassium channels are also present in pancreatic alpha and beta cells and intestinal L and K cells, which secrete glucagon, insulin, and the incretins, glucagon-like peptide one or GLP1, and glucose-dependent insulinotropic polypeptide, or GIP.
All these hormones are crucial for glucose regulation. The authors therefore hypothesize that patients with long QT syndrome II may have increased incretin and beta cell, but decreased alpha cell function and thus, lower glucose levels. To test this hypothesis, they measured secretion of these hormones and cardiac repolarization in response to a six-hour, 75 gram oral glucose tolerance test in 11 patients with long QT syndrome II with functional mutations in HERG with 22 matched healthy participants.
They found that following glucose ingestion, patients with long QT syndrome II displayed exaggerated incretin and endocrine pancreatic function with more than 50% increased levelsq of circulating insulin, GLP1 , and GIP and defective glucagon secretion, causing low plasma glucose levels and thus, increased risk of symptomatic reactive hypoglycemia following the glucose load.
Furthermore, in rats, pharmacological blockade of these voltage gate at potassium channel 11.1 with [inaudible 00:02:43] had similar effects and inhibition of HERG in beta and L cells increased insulin and GLP1 secretion up to 50%. Finally, glucose ingestion aggravated cardiac repolarization disturbances in patients with long QT syndrome II with a 122% greater increase in QT interval in these patients compared to controls. The take home message is that clinicians should be more aware of the risk of hypoglycemia with glucose ingestion in patients with long QT II syndrome and also recognize that this reactive hypoglycemia can further increase the risk of malignant arrhythmia in these patients.
The next paper is the first study to describe the risk of myocardial infarction after discontinuation of thienopyridine therapy in the DAPT study, or dual antiplatelet therapy study. As a reminder, in this trial, after PCI and 12 months of clopidogrel or prasugrel plus aspirin, eligible patients remained on aspirin and were randomized to continue thienopyridine versus placebo for 18 months. At 30 months, patients stopped the study drug and were observed for three months. In the current study by first author Doctor Schmidt, corresponding author Doctor Mauri, and colleagues from Brigham and Women's Hospital in Boston, Massachusetts. The authors looked at cumulative incidents of myocardial infarction assessed over three months after randomization and three months after study drug discontinuation. They found that discontinuing thienopyridine after either 12 or 30 months was associated with an early increase in myocardial infarction risk, mainly unrelated though to stent thrombosis. The magnitude of risk was highest in the early time frame and lower in patients not treated with the [inaudible 00:04:47] eluting stents.
The authors further compared pateints with DAPT scores above or below 2, and showed that both groups had lower rates of myocardial infarction with continued thienopyridine . Thus, while higher DAPT scores identify patients with a greater absolute ischemic benefit relative to bleeding with continued thienopyridine therapy, discontinuation at 12 months increases the myocardial infarction hazard regardless of DAPT score group.
The next paper describes the impact of depression treatment on one year mortality following acute myocardial infarction. Doctor [inaudible 00:05:28] and colleagues from the University of Missouri School of Medicine in Kansas City looked at the TRIUMPH study, which is an observational multicenter cohort study that enrolled more than 4000 patients with acute myocardial infarction between 2005 and 2008 from 24 US hospitals.
Patients were administered the patient health questionnaire 9 during the index myocardial infarction admission and depression was defined by a score of 10 or above. This was categorized as treated if there was a documentation of a discharged diagnosis, medication prescribed for depression, or referral for counseling, and is untreated if none of these three criteria were documented. Overall, 18.7% of patients met criteria for depression and 30.4% were treated. Compared without depression, patients with treated depression had one year mortality rates that were not different. However, patients with untreated depression had a higher one year mortality when compared to patients without depression. In summary, this study really shows that the association between depression following myocardial infarction and increased mortality differs by depression treatment status at the time of the index myocardial infarction. Patients with untreated depression have a 70 to 90% higher risk of dying at one year after the myocardial infarction than patients without depression or patients with treated depression. These findings should therefore encourage further research to examine the impact of depression recognition and treatment at the time of an acute myocardial infarction.
The final study provides insight into the paradox that folate deficiency is an independent risk factor for congenital heart disease, yet the maternal plasma folate level is paradoxically not a good diagnostic marker of this risk. In the current study by first author Doctor Wang, co corresponding authors Doctors Chow and Wang, from Fudan University, Shanghai, China. The authors examined six folate related polymorphisms in three independent case control groups comprising 1489 patients with congenital heart disease and 1745 healthy individuals from the Han Chinese population. They found that a specific fidgetin intronic 4 variant was associated with decreased circulating folate levels and increased protection against congenital heart disease. They further showed that increased fidgetin expression inhibited proteasomal degradation of reduced folate carrier 1 and dihydrofolate reductase, thus facilitating [inaudible 00:08:29] uptake and metabolism of folate. Their results therefore demonstrated that folate utilization, rather than the circulating folate levels, determined the preventive effects of folate against congenital heart disease. These findings provide new insights into the relationship of circulating folate levels with congenital heart disease and potentially other folate associated diseases.
Well, that wraps it up for your summaries. Now, for our feature discussion.
Today's feature paper really represents the first data we have that tells us what our cardiovascular health in middle age is doing to us in older age, in terms of both morbidity and longevity. To discuss this paper today, I'm so happy to have the first and corresponding author, Doctor Norrina Allen from Northwestern University in Chicago and Doctor Jarett Berry, associate editor from UT Southwestern. Welcome, both.
Dr Norrina Allen: Thank you very much.
Dr Jarett Berry: Thanks, Carolyn.
Dr Carolyn Lam: Norrina, could I start with you? This represents the 40 year follow up of the Chicago Heart Association detection project and industry. Could you maybe start by telling us a little bit about the Chicago Heart Association study?
Dr Norrina Allen: The Chicago Heart Association study was a large study that recruited almost 40,000 individuals who were employed in Chicago. They did a baseline exam between 1967 and 1973. After that baseline exam, we followed those individuals for over 40 years using their Medicare records, so we've been able to monitor their healthcare utilization and the incidence of disease across their lifetime up through 2010.
Dr Carolyn Lam: Then you measured their cardiovascular health by specific measurements, right? Could you tell us how that was defined and then also how was morbidity burden defined?
Dr Norrina Allen: Of course. We really think the overall burden of cardiovascular health tells us something more than looking at individual risk factors, so we classified each of the CHA participants into one of four groups, and each of those groups was defined by the level of main cardiovascular risk factors, including blood pressure, BMI, diabetes, smoking, and cholesterol level. We identified people who had favorable levels of all of those risk factors, individuals who had one elevated but not clinically of those high risk factors, individuals who had one high level, or individuals who had two or more high levels. That was based on their baseline exam. Overall we found that about 6% of the CHA participants had favorable levels of all of the risk factors at baseline, 19% had one or more that was elevated, 40% had one high, and 35% had two or more high risk factors, and again this was at the baseline exam when they were young to middle aged.
We then followed them, as I mentioned, using Medicare data and we identified the burden of whole morbidity based on the ICD9 codes in their Medicare record, and we identified the level of morbidity for each year of age, from entry into Medicare, [inaudible 00:11:54] all the way to their death.
Dr Carolyn Lam: And now, drum roll, your findings, they were pretty stunning.
Dr Norrina Allen: Yeah. As you mentioned when you introduced the study, this study is really the first to look at the whole of an individual's later life, meaning not just looking at the incidence of disease or longevity but taking those both into account. What we were particularly interested in was looking at the cumulative burden of morbidity in older age and the relative proportion of life that people live with cardiovascular or all cause morbidity. What we found was that individuals, who at baseline in young and middle age and favorable levels of all major cardiovascular risk factors, lived longer by almost four years but they also delayed the onset of all cause and cardiovascular morbidity by 4 and a half and almost 7 years respectively. What that means is that the proportion of their life that they live with morbidity was much shorter, they lived longer and healthier as compared to individuals who had one or two more high risk factors.
Dr Carolyn Lam: What an important public health message. Jarett, this concept of morbidity compression, tell us your thoughts.
Dr Jarett Berry: This is a really important paper. We've known for a long time, of course, that low risk individuals live longer, but the question of whether or not low risk individuals lived better throughout their life has been incompletely understood. The problem is that because low risk individuals live longer, the question that many have asked is that when we live longer is there a so-called expansion of misery, which some have talked about? That we live longer, but we have the same burden of disease or is that extended time horizon with the extended life span ... is the burden of morbidity compressed into a shorter period of time? In order to do that you need a couple things. You need a very large study that's followed for a very long time. Importantly, not just follow them for a long period of time, but follow enough individuals all the way until death so you know not just the first part of the story but we know the end of the story.
It really wasn't until [inaudible 00:15:18] paper, with not only the very large sample side but the very long term follow up until death, that we've been able to understand that actually low risk status in middle age does actually compress morbidity. This question of morbidity compression is not just an academic question but it actually has potential implications for cost savings and how we think about health care costs in our health care system. It'd be nice to hear [inaudible 00:15:18] thoughts about that as well, what else she found in regard to the Medicare costs.
Dr Norrina Allen: Right. As Jarett mentioned, not only from an individual perspective but at a societal level, what we're interested in is whether being in favorable cardiovascular health actually lowers healthcare costs at the same time as increasing an individual's health and longevity. What we found was that not only do the individuals in favorable health live longer and healthier, but they also have lower cumulative and annual healthcare costs, meaning that from a societal standpoint the compression of morbidity results in healthcare savings. We really think this is a strong method that provides support for earlier prevention efforts not only to improve an individual's quality of life but to reduce the healthcare costs associated with later life morbidity.
Dr Carolyn Lam: Indeed, what an important message to live longer and better and to save societal cost we need to get healthier cardiovascularly in middle age. Now, what really scares me though, is the statistic you told us a bit earlier. Only 6% of the individuals that you studied had a favorable level of all factors. What do you think this implies? What do you think needs to be done?
Dr Norrina Allen: Unfortunately, at this point, it's relatively rare in our population to reach middle age, 40 to 50 years of age, with favorable levels of all major cardiovascular risk factors. I think ... my research is really focused on trying to identify ways and times to intervene, to really help promote cardiovascular health early in life. I really think that we need to work hard to prevent the occurrence of these risk factors and the elevation of these risk factors much earlier in life. That means, even before the age of 40 and much earlier than that, we really need to be focusing on preserving cardiovascular health so that by the time individuals reach later life they can have a good quality of life and a longer, healthier life.
Dr Jarett Berry: I think the issue of the fact that low risk status is rare is that's a challenge that we continue to wrestle with as a society and as investagators interested in this are and how to improve that. When you look at your data, Norrina, I guess one silver lining here is we do see that ... when you look across the strata of risk groups ... it wasn't just the low risk individuals that seemed to benefit. It seemed that there was a little bit of a dose response. The goal obviously is to promote low risk status, but if we could limit the prevalence of those at the highest risk and shift them down a little bit, that could also have potential implications. I'd be interested to hear your thoughts about that.
Dr Norrina Allen: I think that's very accurate. There really is kind of a dose response level, so that every risk factor that's favorable adds a benefit and the more we can do to reduce the high risk factors over time, the better the long term outcomes are likely to be. I do really think prevention doesn't only have to exist before the development of the risk factors, but also there's a benefit to reducing risk factors that may have already developed or are elevated, and to try and reduce their level. I would say that I think that's an interesting next step that we really want to look at and try and think about how best to intervene even at middle age and help improve outcomes much later in life.
Dr Carolyn Lam: Thank you, listeners, for joining us today. I'm sure you agree, it's such an important message. Share it with your friends and tune in next week.