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Circulation on the Run

Nov 4, 2019

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.

Dr Greg Hundley: And I'm Dr Greg Hundley, associate editor from the Poly Heart Center at VCU Health in Richmond, Virginia.

Dr Carolyn Lam: Greg, this issue is super exciting. It's the ESC simultaneous publication issue, isn't it? So the original papers were simultaneous publications at the European Society of Cardiology meeting this year.

Dr Greg Hundley: Oh, wow. Carolyn can't wait to get to these. So Carolyn, later we're going to listen to the authors of this feature discuss the association between ICD use and all-cause mortality in a contemporary heart failure reduced ejection fraction cohort and examine relevant subgroups. So Carolyn, I'm going to get started with my first paper and it's a randomized trial of one hour, one-hour deponent T protocol and suspected acute coronary syndromes and it's a rapid assessment in emergency rooms and it's from professor Derek Chew from Flinders Medical Center. High sensitivity troponin assays promise earlier discrimination of MI, yet the benefits and harms of this improved discriminatory performance when incorporated within rapid testing protocols with respect to subsequent testing and clinical events has not been evaluated in an in-practice, patient level, randomized study. So this multicenter study evaluated the non-inferiority of a zero to one hour, zero to one-hour, high sensitivity troponin T protocol compared with a more traditional zero to three-hour mask, high sensitivity troponin T protocol in those suspected with ACS.

Dr Carolyn Lam: Interesting. So what did the study show?

Dr Greg Hundley: So participants in the zero to one-hour arm were more likely to be discharged from the ED quicker and that would be expected. So 45% versus the standard arm, which was 32%. Also their median ED length of stay was shorter, and we would expect that. Four and a half versus five and a half hours. Those randomized to the zero to one-hour protocol were less likely to undergo functional cardiac testing. The zero to one-hour high sensitivity troponin T protocol was not inferior to standard of care and among patients discharged from the ED, the zero to one-hour protocol had a negative predictive value of 99.6% for 30-day death or MI. So Carolyn, how about your first study?

Dr Carolyn Lam: Well, from MI risk stratification to heart failure risk stratification. I'm going to tell you about a paper describing the TIMI Risk Score for heart failure in diabetes, which is a novel integer base clinical risk score for predicting hospitalization for heart failure in patients with type two diabetes. This is from Dr Mark Sabatine and the TIMI study group who developed a clinical risk score for heart failure hospitalization in more than 8,200 patients with type two diabetes in the placebo arm of saver TIMI 53, as well as externally validated this score in more than 8,500 patients with type two diabetes in the placebo arm of declare TIMI 58.

They found that five clinical variables were independent risk predictors of heart failure hospitalization. These were prior heart failure, history of atrial fibrillation, coronary artery disease, estimated GFR, and urine albumin-to- creatinine ratio, a simple integer base score from zero to seven points. Using these predictors identified a more than 20 full gradient of heart failure hospitalization risk in both the derivation and validation cohorts with high SES statistics. Although the relative risk reductions with dapagliflozin were similar for patients across the risk scores, the absolute risk reductions were greater in those with higher baseline risks.

Dr Greg Hundley: Wow, Carolyn. So tell us what are the clinical implications of this really thorough study?

Dr Carolyn Lam: In summary, the risk score had excellent discrimination in two large clinical trial cohorts. It was well calibrated, and it identified a strong gradient of increasing absolute reduction in risk of heart failure hospitalization with the SGLT two inhibitor dapagliflozin. So by using this TIMI Risk Score for heart failure in diabetes, which is a simple validated clinical risk score, clinicians could better educate patients about their risk for heart failure hospitalizations and could perhaps better identify those patients who have a greater absolute risk reduction in heart failure risk with SGLT two inhibitors.

Dr Greg Hundley: Very good, Carolyn. Well, I'm going to go back to the world of troponins and talk about a paper from Nicholas Mills from University of Edinburgh. And in this study, they evaluated the safety and effectiveness of risk stratification thresholds of high sensitivity troponin in patients with suspected acute coronary syndrome. 48,282 consecutive patients with suspected ACS were enrolled in a multicenter trial from 10 hospitals within Scotland and they're pre-specified secondary and observational analyses. They compared the performance of the limit of a detection of less than two nanograms per liter versus the optimized stratification threshold of less than five nanograms per liter using the Abbott high sensitivity troponin I assay. Patients with myocardial injury at presentation with less than two hours of symptoms or with ST segment elevation myocardial infarction were excluded and the negative predictive value was determined in all patients in subgroups for a primary outcome of MI or cardiac death within 30 days. And they had a secondary outcome that was MI or cardiac death at 12 months.

Dr Carolyn Lam: Nice. So Greg, which threshold of troponin was the optimal one?

Dr Greg Hundley: So the negative predictive value for the primary outcome was 99.8% and 99.9% in those with cardiac troponin I concentrations of less than five or less than two nanograms per leader respectively. At both thresholds, the negative predictive value was consistent in men and women across all age groups. Although the proportion of patients identified at low risk fell with increasing age. Compared to patients with cardiac troponin I concentrations of greater than five nanograms per liter but less than the 99th percentile, the risk of MI or cardiac death at 12 months was 77% lower in those with less than five nanograms per liter and 80% lower in those with less than two nanograms per liter. So in conclusion, use of risk stratification thresholds for high sensitivity cardiac troponin I identified patients with suspected acute coronary syndrome in at least two hours of symptoms at low risk presentation irrespective of both age and sex.

Dr Carolyn Lam: Very nice. Well, more risk stratification in this next paper, which really evaluated the application of the 2018 ACC AHA Cholesterol Management Guideline recommendations for additional lipid lowering therapies in patients with established atherosclerotic cardiovascular disease and residual dyslipidemia despite maximum tolerated Statin who were enrolled in the ODYSSEY OUTCOMES trial. Now, just as a reminder, the 2018 US Cholesterol Management Guidelines recommend additional lipid lowering therapies for secondary prevention in patients with LDL above 70 or non-HDL above a hundred despite maximum tolerated Statin therapy.

Such patients are considered at very high risk based on a history of more than one major atherosclerotic cardiovascular disease event or a single event and multiple high-risk conditions. So in this paper from Dr Matt Roe from Duke Clinical Research Institute and colleagues, they found that in the ODYSSEY OUTCOMES trial, patients classified as very high risk by these 2018 ACC AHA guidelines and either because of a history of multiple atherosclerotic cardiovascular events or a single event, which is a trial qualifying acute coronary syndrome and multiple high risk conditions, these very high risk patients had more than double the risk of recurrent cardiovascular events as compared to patients classified as not very high risk.

 They further looked at the association of Alirocumab with outcomes and found that Alirocumab was associated with a consistent relative risk reduction in both risk categories. But the absolute risk reduction for major adverse cardiovascular events was numerically greater, although not statistically different, in the very high-risk group versus those not at very high risk and among patients at very high risks with multiple prior events versus a single prior event.

Dr Greg Hundley: Wow, Carolyn. Can you put all this together? This is a lot of information in this study.

Dr Carolyn Lam: Yes, so it would appear that the application of the new ACC AHA 2018 guideline recommendations for risk stratification and the use of additional lipid lowering therapies in patients with established cardiovascular disease clearly identifies patients at very high risk of recurrent cardiovascular events after an acute coronary syndrome and these patients may derive substantial benefit from additional lipid lowering therapy, for example, with a PCSK nine inhibitor.

Dr Greg Hundley: Very nice, Carolyn. Well, let me just finish off with what other articles we have in this ESC featured issue of our journal. So Jonathan Stamler and John Lundberg in separate letters discuss findings related to whether hemoglobin beta 93 cystine is not required for export of nitric oxide bio activity from the red blood cell. And in additional separate letters, Doug Lewandowski and Heng-Chen Yao discuss preservation of ACL CoA and attenuation of pathological and metabolic cardiac remodeling through selective lipid trafficking. In a perspective piece, Blake Thomson from the University of Oxford discusses what Medicare for all in the United States can mean for US medical research and provides lessons from the United Kingdom. In a letter from the United States, Gregory Marcus from University of California San Francisco discusses incident atrial fibrillation among American Indians in California and then both Marco Bergonti from University of Milan and Derek Chew from University of Calgary present two separate cases in our ECG challenge feature. Well, Carolyn, what a great issue and how about we turn to our feature discussion?

Dr Carolyn Lam: Yes, let's go. Thanks, Greg.

Dr Greg Hundley: Welcome, everyone, to our feature discussion today we have Gianluigi Savarese from Karolinska Institute in Stockholm, Sweden and our own associate editor, Sana Al-Khatib from Duke University. We're going to be discussing implantable cardioverter defibrillators in their mortality and looking at a more recent take on this relative to some of the previous published studies. So Gianluigi, I'd like to start with you. Could you tell us a little bit about the hypothesis and why you wanted to perform your study?

Dr Gianluigi Savarese: Yes. Basically we design our study based on three main considerations. First one is recent studies show that the advance in heart-failure therapies have impact patients' risk profile leading to roughly 40% reduction risk of sudden cardiac death in HFrEF and RCTs on ICD use for primary prevention of sudden cardiac death and rural patients more than 20 years ago and thus, nowadays the beneficial prognostic effects of ICD may be different due to the improved risk profile in this population.

The second consideration was that efficacy of ICD patients with heart failure with non-ischemic cardiomyopathy patients receiving a contemporary heart failure therapy as being a question in Danish trial and the third consideration is that efficacy of ICD in elderly is still debated due to findings again from the Danish trial showing a significant reduction in all-cause death associated with ICD use in patients age younger versus older than 70 years old. Based on these considerations, we decided to assess the use of ICD for primary prevention propose in a contemporary and selected FRF population and to assess the association between ICD use and outcomes in such a population.

Dr Greg Hundley: So it sounds like we're doing an update on the utility of ICDs. Can you tell us a little more about your study population and your study design and then let's hear a little bit about your results.

Dr Gianluigi Savarese: Sure. First of all, I would like to first highlight of course the observational natural of this study. Our analysis is performed using data from the Swedish Heart Failure Registry, which is a large enough select court of heart failure patients, enrolling patients regardless of ejection fraction. So today we have roughly around 70,000 patients. And of course for the current analysis we select the patients with HFrEF. There were around 15,000 patients with the HFrEF who were eligible for ICD use for primary prevention according to the ESC guidelines. A study design, we used propensity score matching design in order to try to address the issue of potential compounders. Of course this is a very important point in observational studies. So basically, we amassed patients receiving the ICD versus those not receiving ICDs. And we assessed the association between ICD use and all-cause death and cardiovascular death and we accessed one year and five-year outcome.

Dr Greg Hundley: And so what were some of those results?

Dr Gianluigi Savarese: What we observed is that there was a statistically significant 25 relative risk reduction in all-cause mortality in ICD recipients versus those who didn't receive an ICD within one year and there was also a 12% reduction erased within five years. And we also serve a statistically significant 29% reduction in risk of cardiovascular mortality within one year. But we were not able to observe any association for cardiovascular mortality within five years. We thought it was particularly relevant to have subgroup analysis in our studies since there are so many questions regarding ICD use in specific subgroups, which are, for example, older versus younger patients, those with versus without ischemic heart disease, males versus the females and so on. So what we observed was that results in terms of all-cause mortality were consistent in all of the subgroups considered such as patients older versus younger than 70 years old, versus those without history of ischemic heart disease and those with versus without concurrent CRT use.

Dr Greg Hundley: What about the frequency of implanting ICDs? Was the frequency expected in your results?

Dr Gianluigi Savarese: We add that only 10% of our patients received an ICD at the baseline. This person's age is quite low in particular. If we compare these with other studies in US for example, or also in other European countries and basically, we can only speculate about the underuse of ICD in primary prevention propose. First of all, a certain proportion of ICD underuse may be explained by the fact that we could not assess whether life expectancy was longer than one year, and this is one of the eligibility criteria for ICD according to the guidelines.

Then another point is that in Sweden, the majority of heart failure patients are seen by primary care physician and general practitioners who may have less knowledge and acceptance of device therapy and then higher perception of contraindication. In our previous analysis, we showed that patients not seen by cardiologists have lower likelihood of receiving an ICD and use of devices is higher in centers who do implants, CRT, ICD. So this may be some of the explanation that I can anticipate that some more analysis will follow where we will try to assess the predictors for an under use of ICD for primary prevention.

Dr Greg Hundley: Well, thank you very much. Sana, now we're going to turn to you and help us put this study in perspective to what we have already found or observed in other prior studies related to implantation of cardio defibrillators.

Dr Sana Al-Khatib: As was mentioned earlier, I was the handling associate editor for this paper, so I really enjoyed the handling it and writing an editorial on it. The main points that I wanted to touch on are number one, the significantly low or reduced utilization rate of ICDs. So as was mentioned, the 10% of this patient population received a primary prevention ICDs. Even if you account for some of the new ones is that you can't estimate life expectancy. You can't capture granular clinical data on these patients. So of course some of the non-use of ICDs may have been appropriate. I think 10% by anyone's definition is still pretty low and I'm very encouraged to hear that there are plans to look at predictors of non-use, the characteristics of those patients and hopefully the office can build on their findings and try to implement some strategies to improve the utilization of this life saving therapy.

The other thing that I wanted to touch on is clearly the results are positive in favor of the implantable cardioverter defibrillator. Showing that it significantly reduces all-cause mortality within one year, within five years, certainly reduces cardiovascular mortality within one year. As was mentioned, the reduction in cardiovascular mortality within five years was not significant and to me that is probably mostly explained by competing causes of death in this patient population, but I also cannot rule out the possibility of some mis-classification of causes of death, which is not uncommon. I do want to commend the authors for the great and robust methods that they applied in their analysis. As was mentioned, this was a comparative effectiveness research using observational data. These kinds of analyses can be pretty challenging, but the authors defined their patient population very clearly. They used propensity score matching. In fact, they took it a step further by doing a negative control analysis, meaning looking at hospitalizations for renal failure, for pneumonia, respiratory infections, things like that that you don't expect to be affected by the ICD and they found no difference in that.

And that is amazing to kind of see this level of analysis that I believe really lends their results more credibility. It is important though to keep in mind that when you have 10% of patients getting an ICD, I suspect that this was a highly selected patient population and most likely people who were thought to benefit the most from ICDs were implanted with an ICD. And yet, as I said, that given the robustness of the methods that they use, I actually believe the results. I think the results are credible.

The one last point that I want to comment on is the subgroup analyses that were mentioned. Absolutely important subgroups to look at from a clinical perspective. But I point out the fact that when you start looking at subgroup analyses, and especially when you have a smaller sample sizes and lower event rates that it makes you start thinking about, "Well, are these results valid? Are they believable?" I mean, even honestly, in the setting of a randomized clinical trial, I look at subgroup analyses as hypothesis generating. So I liked that they included those just to kind of really emphasize the importance of looking at these subgroups. But I certainly would not put too much weight on the subgroup analysis results, but overall great results and congratulations to the authors.

Dr Greg Hundley: Fantastic overview, Sana and Gianluigi. So on behalf of Carolyn Lam and myself, we wish you a great week and we look forward to speaking with you next week.

Dr Carolyn Lam: This program is copyright American Heart Association 2019.