Circulation May 21, 2019 Issue

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 Greg Hundley, Associate Editor of Circulation and
Director of the Pauley Heart Center at VCU Health in Richmond,
Virginia. Well, Carolyn, our feature article is going to focus on
trastuzumab-induced cardiac dysfunction in breast cancer
patients. We will discuss with Stanford investigators their use
of pluripotent stem cells that are differentiated to
cardiomyocytes and subsequently exposed to toxins to determine an
individual's susceptibility to cardio-toxicity from cancer
treatment. But before we get to that, Carolyn, do you have a
paper that you'd like to discuss?


Dr Carolyn
Lam:               
Well, the first paper deals with cardiac biomarkers and asks the
questions, can these biomarkers be useful for the diagnosis and
risk stratification of syncope?" Now, this paper is from Dr
Mueller and colleagues from University of Hospital Basel in
Switzerland. They evaluated the diagnostic and prognostic
accuracy of BNP, NT-proBNP, high-sensitivity cardiac troponin T,
and high-sensitivity cardiac troponin I concentrations, alone and
against the ones of clinical assessments in more than 1,500
patients presented with syncope to the emergency department in a
prospective, diagnostic multi-center study. Now, cardiac syncope
was adjudicated in 234 or 15% of patients. What they found was
that the diagnostic accuracy from cardiac syncope, as quantified
by the area under curve, was 0.77 to 0.78 for all four
biomarkers. That was superior to that of the syncope-specific
diagnostic score, EGSYS.


                                               
Now, combining the four biomarkers further improved diagnostic
accuracy to an area under curve of 0.81. Furthermore, using the
four biomarkers at cutoffs achieved predefined thresholds for
sensitivity and specificity and allowed rule-in or rule-out of
30% of all patients. Finally, the biomarkers predicted adverse
cardiac outcomes with moderate to good prognostic accuracy and
better than some of the existing syncope risk-prediction scores.


Dr Greg
Hundley:            
Very interesting, Carolyn. Do you think we can now use this
clinically? Should we be drawing these biomarkers on patients
with syncope?


Dr Carolyn
Lam:               
These results really do imply that these biomarkers look like
useful tools for the early rule-out and/or rule-in of cardiac
syncope in the emergency department. After all, these biomarkers
are readily available, inexpensive, and results of this study
suggest that they have potential to simplify diagnosis and to
risk stratify in challenging presentations. However, before
embracing the concept of ordering cardiac biomarkers routinely
for syncope presentation, we really need to read the editorial by
Dr Sandhu and Sheldon, in which important perspectives are
presented, such as considerations of the certainty of the
diagnosis of syncope, the usefulness of the comparative scores,
the timing of testing, the potential unintended adverse
consequences of testing. These editorialists concluded that,
although promising, further work is needed to determine how the
use of cardiac biomarkers should be incorporated into a
risk-stratification algorithm.


Dr Greg
Hundley:            
Wow, Carolyn. It sounds like we'd get a lot out of that
particular editorial. I'm going to switch over and talk about
NT-proBNP in patients with pulmonary hypertension. This is a
paper from Dr Kelly Chin from UT Southwestern, and the study
evaluated the utility of end terminal pro BNP level thresholds
and assessing prognosis in pulmonary hypotension using the
GRIPHON study. So GRIPHON is a global double blind, randomized
placebo control event driven phase 3 study which assesses the
safety and efficacy or a Prostacyclin agonist that promotes
pulmonary arterial vasodilation.


                                               
They performed the study in patients that were 18 to 75 years old
with a diagnosis of idiopathic pulmonary hypertension, heritable
hypertension or pulmonary hypertension associated with connective
tissue disease, repaired congenital systemic pulmonary shunts,
HIV infection, drug use or toxin exposure; and the diagnosis of
pulmonary hypertension was confirmed by right heart
catheterization and by a reduced 6-minute walk distance of 50 to
450 meters.


                                               
Eligible patients were permitted to take their other therapies
including Endothelin receptor agonists and phosphodiesterase
type-5 inhibitors. The patients were categorized into low, medium
and high in terminal BNP level subgroups according to two
thresholds. First, by just the tertiles within the study overall
and the secondly by the ESC guideline cutoff ranges.


Dr Carolyn
Lam:               
Nice, so what did they find Greg?


Dr Greg
Hundley:            
Well first of all both thresholds either the tertile one of the
ESC in follow-up NT-proBNP categories were highly prognostic for
future morbidity and mortality. And their time dependent analysis
the risk of experience a morbidity or mortality even was 92% and
83% lower in the treated patients with a low and medium NT Pro
BNP level. And 90% and 56% lower in placebo treated patients with
low and medium NT-proBNP levels. So both, whether you're taking
that drug of not, the NT-proBNP levels were prognostically
valuable. More pronounced treatment benefit of selexipag was seen
in the medium and low proBNP groups. There was a positive value
for the interaction term.


Dr Carolyn
Lam:               
Wow, sounds like two really important findings.


Dr Greg
Hundley:            
Yes, exactly Carolyn. So first, NT-proBNP levels are highly
prognostic for pulmonary arterial hypertension progression. And
having NT-proBNP in the low range, by improving to or maintaining
low NT-proBNP levels is a clinically relevant treatment goal for
those with pulmonary artery hypertension. And of course as we
described this was a very diverse well represented group of many
different types of patients with pulmonary hypertension. Then
second, while selexipag the study drug was beneficial in all
NT-proBNP categories, the treatment effect was greater in those
with low and medium categories versus the very high. Suggesting
that earlier selexipag treatment may be of greater benefit. But
very interesting biomarker study that follows up on yours
Carolyn.


Dr Carolyn
Lam:               
Indeed!


Dr Greg
Hundley:            
Carolyn what about your next paper?


Dr Carolyn
Lam:               
Well I want to switch tracks now and talk about iron. And the
question is, how does intravenous iron repletion augment exercise
capacity in chronic heart failure? Even if hemoglobin doesn't
change. So, first some background right, now, besides hemoglobin
it's important to recognize that iron is an obligate component of
the mitochondrial enzymes that generate cellular energy in the
form of adenosine triphosphate and phosphocreatine. So dynamic
phosphorous magnetic resonance spectroscopy is a noninvasive tool
that can really quantify the in vivo muscle energetics by
measuring the kinetics of phosphocreatine recovery after
exertion. These authors use this technique, and these are Dr
Okonko from King's College, London British Heart Foundation
sender of excellence, school of cardiovascular medicine and
sciences. The James Black Center in London and colleagues. And
what they did was they tested the hypothesis that intravenous
iron repletion in chronic heart failure would enhance skeletal
muscle energetics as reflected by a shorter phosphocreatine
recovery halftime on phosphorous magnetic resonance spectroscopy
imagining of the skeletal muscles. And they looked at 40 patients
with chronic heart failure with reduced deduction and iron
deficiency in a randomized double blind placebo controlled ferric
iron and heart failure trial.


Dr Greg
Hundley:            
So, what did they find?


Dr Carolyn
Lam:               
They found that a single total dose infusion of intravenous iron
repleted iron stores and augmented skeletal muscle energetics at
2 weeks post infusion. Enhancements in the skeletal muscle
energetics which implied better mitochondrial function were
accompanies by improved symptoms despite no change in hemoglobin
at 2 weeks. So, this trial really provides mechanistic support
for iron repletion in patients with chronic heart failure and its
very importantly discussed in an editorial by Peter van der Meer,
Haye van der Wal, and Vojtech Melenovsky. And I really suggest
that everybody read that.


Dr Greg
Hundley:            
Well, I'm going to talk a little bit about dietary omega-6 fatty
acids and the incidence of cardiovascular disease and mortality.
And this paper is from Matti Marklund from the Georgia Institute
for Global Health and the University of New South Wales in
Sydney, Australia. The study focuses on linoleic acid which is an
omega-6 polyunsaturated fatty acid that we get from pumpkin
seeds, flax seeds, walnuts, soybean oil, canola oil and
grapeseed. It's been associated with a decrease in cardiovascular
risk, but others have worried about an effect of consumption
mainly the downstream production of arachidonic acid which can
give rise to eicosanoids that are both pro inflammatory and pro
thrombotic.


                                               
And it's interesting Carolyn, several organizations suggest
replacing saturated fat and carbohydrates with linoleic acid. So
this study was really performed to address whether consumption of
linoleic acid is associated with future cardiovascular events. In
the study, investigators measured linoleic acid as well as
arachidonic acid levels and from a global consortium across 30
perspective observational studies from 13 countries they
performed multi variable adjusted associations of circulating an
adipose tissue linoleic and arachidonic acid biomarkers with
incident total cardiovascular disease and subtypes of
cardiovascular disease including, coronary heart disease,
ischemic stroke and cardiovascular mortality and this was all
done as pre-specified analytic plan.


Dr Carolyn
Lam:               
Wow, so what did they find?


Dr Greg
Hundley:            
Well did I put you to sleep discussing all of that?


Dr Carolyn
Lam:               
No! You have to tell me what they found. I'm seriously so
interested in this topic because being vegetarian I actually get
my source of omega fatty acids exactly from these sources.


Dr Greg
Hundley:            
Okay, so Carolyn, higher levels of linoleic acid were associated
with lower risk of total cardiovascular disease, ischemic stroke,
cardiovascular mortality. While arachidonic acid was not
associated with cardiovascular risks. And so, the clinical
implications of the results support the potential benefits of
main dietary omega- 6 fatty acid. That is linoleic acid for
cardiovascular disease prevention. Now, while the trial is not
randomized so we don't have definitive answers, the results do
not support any theorized cardiovascular harms of consuming
omega-6 fatty acids. And there is an excellent review on
polyunsaturated versus saturated fat intake by Thomas Sanders
from King's College, London as an editorial to this piece. So
Carolyn I think we're safe right now in consuming linoleic acid.
So how about a transition to our featured article and learn a
little bit more about trastuzumab-induced cardiac dysfunction.


Dr Carolyn
Lam:               
Absolutely!


Dr Greg
Hundley:            
Great.


                                               
Welcome everybody, we have a fantastic paper to discuss. We're
going to review human induced pluripotent stem cell derived
cardiomyocytes and how they can be used to identify individuals
at risk of trastuzumab-induced cardiac dysfunction after
treatment for breast cancer. We have today Nazish Sayed and also
Dr Joseph Wu, both from Stanford University in California.


                                               
Welcome gentlemen.


Dr Joseph
Wu:                  
Thank you for inviting us.


Dr Nazish
Sayed:             
Thank you.


Dr Greg
Hundley:            
Nazish tell us a little bit about what are these human induced
pluripotent stem cells and then also describe your experiment and
what were your results?


Dr Nazish
Sayed:             
So, induced pluripotent stem cells is about 10 years ago I knew
technology where you can actually turn back the clock by you
taking human fiber blast or blood cells and then you can test
full reprogramming factors and turn back differentiated cells to
pluripotent stem cells will mimic like catalytic stem cells. The
catalytics include self-renewal, pluripotency and the most
important that they can be differentiated to any cell type in the
body. For example, cardiomyocytes or endothelial cells the neuron
and kind of mimic these differentiated cells from the same
individual from where the IPSCs were derived from.


                                               
So, what we did in our study is we used this platform to derive
these pluripotent stem cells from patients and then
differentiated them into a cardiomyocyte to understand what would
these human cardiomyocytes behave in a dish when treated with a
Herceptin or trastuzumab and then kind of determine the
underlying mechanism for this cardiac dysfunction. It seemed
really difficult to model trastuzumab and use cardiac dysfunction
as a heart which is the receptor for the trastuzumab is expressed
only in humans.


                                               
People have usually relied on animal model and for the first time
what we did is we used these ideas of cardiomyocytes to model
this dysfunction in a dish. Our results were pretty
straightforward. We found that the IPSCs cardiomyocytes when
treated with the chemotherapy agent showed cardiac dysfunction in
the case of decrease contractility. The contraction velocity of
these each individual cardiomyocytes is significantly reduced.
More with this was also confirmed by having impaired calcium
cycling which is very important for the contractility of these
cardiomyocytes.


                                               
But I think the most important thing which we determined from the
study is that individuals who are treated with trastuzumab have a
metabolic impairment in these cardiomyocytes which is convenient
but however have a severe impact on this contractility and
calcium handling in these cardiomyocytes. And that was one of the
gist of these papers to figure out the metabolic impairment could
be a target where we can improve this cardiac dysfunction in
these patients.


Dr Greg
Hundley:            
And so, after you discovered this, I noticed you also did some
work with AMPK activators and perhaps would reverse some of the
dysfunction. Could you describe a little bit what are AMPK
activators and then how did they reverse the dysfunction that you
observed?


Dr Nazish
Sayed:             
In our study we characterized these IPS cardiomyocytes from these
individuals and then we ran a whole sequencing of them after
treatment where trastuzumab to see which of the pathways which
could be down regulated or dysfunction when compared to the
control patients which are not treated with trastuzumab. And one
of the most significant pathways which we found was in PK
pathways which was down regulated in the trastuzumab treated IPSC
cardiomyocytes. So knowing that the AMPK activators are used for
metabolic diseases, for example being diabetes and metabolic
dysfunction, we thought that this same thing could be used in a
dish where we can take these AMPK activators and simultaneously
cotreat cardiomyocytes with Herceptin or trastuzumab to see if we
can rescue the phenotype and indeed you can see in our paper we
used 4 different AMPK activators with metformin which is a
commonly used diabetic drug. Showing the best rescue for that
trastuzumab induced cardiac dysfunction.


Dr Greg
Hundley:            
Very intriguing because it looks like you've been able to harvest
cells from individuals and then pre-treat them, understand the
mechanism of dysfunction, understand who's at risk of dysfunction
and then offer therapeutic interventions to perhaps prevent that
dysfunction in this patient population. Joe, turning to you now,
this is really revolutionary technology it seems to me. Can you
describe how long does this process take? Is this something that
we see might come into clinical medicine soon?


Dr Joseph
Wu:                  
We're really excited about this technology that Nazish has
described. I think as you know we've been working on this
platform for the past 10+ years. In terms of the timeline, right
now it takes us about a month to generate the induced pluripotent
stem cells. It takes us another month to expand, propagate the IP
itself. It takes us another month to generate the IPS
cardiomyocytes. And it will take us probably another month to do
all the phenotypic characterization in terms of using these IPS
cardiomyocytes to expose them to various chemotherapy drugs and
see how the chemotherapy drugs have an effect on these
cardiomyocytes.


                                               
So, I would say the total timeline is 12 months at this moment.
Is it possible that the timeline could be crunched, could be
shrunk over time? Yes that's possible, I think the technology is
improving month by month, week by week because there are many
different labs trying to work on this platform trying to improve
the whole process. But right now one of the limitations that as
you pointed out is this 4 month time period. And also the cost
that's associated with this. But we're hopeful that over time
that both the time, the costs can go down so that we can offer
this type of platform to help patients diagnosed with cancer,
find out what kind of chemotherapy is safe to use, what kind of
chemotherapy is not safe to use.


Dr Greg
Hundley:            
So, we're working towards clinical applications but at this point
in time it looks like a fantastic platform for understanding,
diagnoses and understanding pathways that for patients
particularly as they are treated for cancer will experience
cardiovascular dysfunction. So, switching a little bit and asking
a related question. Patients that receive trastuzumab often also
receive doxorubicin. Especially the breast cancer patients. If
you looked at this technology trying to understand, and certainly
those more at risk for trastuzumab associated left ventricular
dysfunction, are the patients that previously received
doxorubicin. Have you and your group looked at patients that have
also received doxorubicin and then went on to receive trastuzumab
relative to those that received trastuzumab alone?


Dr Joseph
Wu:                  
I think for these two populations for this particular study, we
tried to keep them clean. Meaning that we're looking mostly for
trastuzumab treated patients, otherwise it's hard for us to piece
out whether the toxicity was due to one medication or the other
medication. But what you are asking is very important because as
you pointed out many of these patients received both and I think
for future studies we should be able to model both medications,
meaning that take some IPS cardiomyocytes treated with
doxorubicin, treated with Herceptin by itself and treated with
both the medications.


                                               
In previous studies we have studied using IPS cardiomyocytes the
effects of doxorubicin induced cardiac toxicity. In just the
assessment, doxorubicin is a very common effective chemotherapy
for breast cancer medications and just like Herceptin, the
clinicians struggled with the issue, as we cannot predict which
patient will develop toxicity. And then granted the doxorubicin
induced toxicity has a slight different mechanism compared to
perception induced mild cardiac dysfunction that this Nazish had
mentioned about. But these are kind of the studies that we're
very excited because now for the first time we have a way to
model this. Otherwise they alternative would be not possible, for
example it would not be possible for us to biopsy breast cancer
patients woman's heart to study the cells.


                                               
Especially in the case of perception. The receptor that's being
studied is not present in animal model cells. For example not
present in mouse cardiomyocytes and therefore it would be very
difficult to understand the mechanism and this is the reason why
the patient specific and disease specific IPS cardiomyocytes
become so useful.


Dr Greg
Hundley:            
Do you find another emerging therapy in this entire realm is the
immunotherapies? Do you think this technology will be applied to
determine susceptibility to immune mediated toxicity?


Dr Joseph
Wu:                  
This is a very good question as well Greg. We've been thinking
about studying that and as you know, it's a more complicated
system because it involves patients’ immune response, the
myocardial, to inflammatory infiltrates that happens. So we have
a couple projects going on. One is to study direct effect of the
immunotherapy on the cardiomyocytes and then the second angle is
to take patients who are in full myocarditis and collect their
patients urine samples, blood samples and to see if we could
expose these IPS cardiomyocytes to the patients urine samples to
see what is the effect. For these IPS cardiomyocytes for future
studies we're also trying to make it more complicated by
generating not just the cardiomyocytes by itself, but generating
what we call engineered heart tissues. In which it's a chunk of
human heart muscles that would have the patients cardiomyocytes,
patients fibroblast, patients endothelial cells and expose them
to the patients serum.


                                               
But that kind of study would take much longer period of time
because the number of people who have these types of
immunotherapy induced myocarditis it's relatively low compared to
patients who have Herceptin or doxorubicin induced cardio
toxicity. This is also part of the reason why we're very much
interested in collaborating with big centers throughout the
country like York Center to see if we could understand this
process better as a team.


Dr Greg
Hundley:            
Excellent. I want to thank both of you for this really elegant
discussion and perfect work moving forward. In summary, you've
illustrated an ability to withdraw human pluripotent stem cells,
differentiate them to cardiomyocytes and then perform tests on
them to forecast susceptibility to various treatments used
commonly for women with breast cancer. And in this study
identifying mechanisms for trastuzumab toxicity. And then perhaps
therapeutic interventions using again human cells which has a
marked leap as you've identified over doing mouse studies,
particularly for studying trastuzumab when the receptors the HER2
receptors in mirroring models differ substantially to those in
human subjects.


Dr Joseph
Wu:                  
Thank you Greg. And we want to also express our thanks to our
collaborators, our colleagues who contributed to the study and
most importantly to the patients who helped us with these
studies.


Dr Greg
Hundley:            
I want to thank both Nazish and Dr Wu from Stanford and Carolyn
and I wish you the best for the coming week and we look forward
to speaking with you again next week.


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