Circulation September 18, 2018 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. This week's journal features
two papers that deal with genetic testing in young athletes and
for sudden arrhythmic death, and with findings that may surprise
you. They really show the complexities of this era of genetic
testing and cardiovascular medicine, and in fact are discussed as
growing pains in cardiovascular genetics. You must listen to our
feature discussion, which is coming right up after these
summaries.


                                               
The first original paper this week suggests that targeting
fibronectin polymerization may be a new therapeutic strategy for
treating cardiac fibrosis. Fibronectin polymerization is
necessary for collagen matrix deposition and is a key contributor
to increased abundance of cardiac myofibroblast following cardiac
injury. In today's paper, first author Dr Valiente-Alandi,
corresponding author Dr Blaxall from University of Cincinnati
College of Medicine and Heart Institute, and their colleagues
hypothesized that interfering with fibronectin polymerization, or
its genetic ablation and fibroblasts, would attenuate myocardial
fibrosis and improve cardiac function following ischemia
reperfusion injury. Using mouse and human cardiac myofibroblasts,
authors found that the fibronectin polymerization inhibitor pUR4
attenuated the pathological phenotype exhibited by mouse and
human myofibroblasts by decreasing fibronectin polymerization and
collagen deposition into the extracellular matrix as well as by
myofibroblast proliferation and migration.


                                               
Inhibiting fibronectin matrix deposition by pUR4 treatment or by
deleting fibronectin gene expression in cardiac fibroblasts
confirmed cardioprotection against ischemia reperfusion-induced
injury by attenuating at first left ventricular remodeling and
cardiac fibrosis, thus preserving cardiac function. In summary,
interfering with fibronectin polymerization may be a new
therapeutic strategy for treating cardiac fibrosis and heart
failure.


                                               
The Insulin Resistance Intervention after Stroke, or IRIS trial,
demonstrated that pioglitazone reduced the risk of both
cardiovascular events and diabetes in insulin-resistant patients.
However, concern remains that pioglitazone may increase the risk
of heart failure in susceptible individuals. To address this, Dr
Young from Yale Cardiovascular Research Center and the IRIS
investigators performed a secondary analysis of the IRIS trial.
They found that older age, atrial fibrillation, hypertension,
obesity, edema, high CRP, and smoking were risk factors for heart
failure.


                                               
Pioglitazone did not increase the risk of incident heart failure,
and the effect of pioglitazone did not differ across levels of
baseline risk. It should however be noted that in the IRIS trial,
the study drug dose could be reduced for symptoms of edema or
excessive weight gain, which occurred more often in the
pioglitazone arm. Overall, pioglitazone reduced the composite
outcome of stroke, MI, or hospitalized heart failure in the IRIS
trial.


                                               
The next study highlights the importance of genetic variation in
cardiac fibrosis and suggests that while fibroblast activation is
a response that parallels the extent of scar formation,
proliferation may not necessarily correlate with levels of
fibrosis. In this paper from co-first authors Dr Park and
Ranjbarvaziri, corresponding author Dr Ardehali, from David
Geffen School of Medicine, University of California, Los Angeles,
the authors utilized a novel multiple-strain approach known as
the Hybrid Mouse Diversity Panel to characterize the
contributions of cardiac fibroblasts to the formation of
isoproterenol-induced cardiac fibrosis in three strains of mice.


                                               
They found that isolated cardiac fibroblasts treated with
isoproterenol exhibited strain-specific increases in the levels
of activation, but showed comparable levels of proliferation.
Similar results were found in vivo with fibroblast activation but
not proliferation correlating with the differential levels of
cardiac fibrosis after isoproterenol treatment. RNA sequencing
revealed that cardiac fibroblasts from each strain exhibited
unique gene expression changes in response to isoproterenol.


                                               
The authors further identified LTBP2 as a commonly upregulated
gene after isoproterenol treatment. Expression of LTBP2 was
elevated and specifically localized in the fibrotic regions of
the myocardium after injury in mice and in human heart failure,
suggesting that it may be a potential therapeutic target. That
brings us to the end of our summaries. Now for our feature
discussion.


                                               
We all know that t-wave inversion is common in patients with
cardiomyopathy, however up to a quarter of athletes of African
descent, and five percent of white athletes also have t-wave
inversion on ECG, but with unclear clinical significance despite
comprehensive clinical evaluation. Now, what is the role in
diagnostic use of genetic testing beyond clinical evaluation when
we investigate these athletes with t-wave inversion? Well we're
about to get some answers in today's feature paper, and I'm so
pleased to have the corresponding author of the paper, Dr Sanjay
Sharma from St. George's University of London, as well as our
associate editor Dr Mark Link from UT Southwestern.


                                               
Sanjay, please let us know what you did and what you found.


Dr Sanjay
Sharma:           
Well as you rightly say, that up to 25% of black athletes have
t-wave inversion, as do three to five percent of white athletes.
And these t-wave inversions often overlap with the sort of
patterns that you see in patients with hypertrophic
cardiomyopathy and arrhythmogenic cardiomyopathy. For example,
80% of people with hypertrophic cardiomyopathy have t-wave
inversion as do 60% of patients with ARVC. Now we know that some
ECG patterns, t-wave inversions in V1 to V4 are benign in black
patients, but the significance of other ECG patterns is unknown.
Cascade screening in family members with cardiomyopathy have
shown that t-wave inversion may be the only manifestation of gene
inheritance, and there are reports to suggest that some athletes
with t-wave inversion do go on to develop overt cardiomyopathy.
Now when we investigate the vast majority of our patients with
t-wave inversion, these are our athlete patients, we don't
actually find anything. But over the past decade, also, these has
been major advance in next generation sequencing that allows us
to perform genetic testing in a large number of genes that can
cause diseases, capable of causing sudden death.


                                               
And so, we thought we'd investigate the role of this gene testing
in athletes with t-wave inversion. We looked at a hundred, 50
black athletes and 50 white athletes who had t-wave inversion,
and we investigated them comprehensively with clinical tests. But
we also added in a gene panel looking at 311 genes implicated in
six cardiac diseases, notably hypertrophic cardiac myopathy,
arrhythmogenic cardiomyopathy, dilated cardiomyopathy, left
ventricular non-compaction, long QT syndrome, and the brugada
syndrome. We found that 21% of our athletes were then diagnosed
with a cardiac disorder capable of causing sudden death, and the
vast majority of these people had hypertrophic cardiomyopathy.
And this diagnosis was based on clinical evaluation. When we
looked at gene testing, we found that gene testing only picked up
a problem in 10%. So, the diagnostic yield of gene testing was
half that of comprehensive clinical investigation.


                                               
When we actually looked at athletes who had nothing wrong with
them in clinical investigation, and actually had a gene mutation,
we found that only 2.5% of athletes who had t-wave inversion but
clinically normal tests, actually had something wrong with them.
And our conclusions were that gene testing picks up only half the
athletes that clinical testing does, and gene testing is only
responsible for identifying 2.5% of athletes with t-wave
inversion, where clinical tests are negative. That was the
summary of our study in short. We did find that black athletes
were less likely to have a positive diagnosis of cardiac myopathy
than white athletes, and black athletes are also less likely to
have a genetic mutation capable of causing a cardiomyopathy than
white athletes.


Dr Carolyn
Lam:               
First and foremost, congratulations on such a beautiful paper,
and so wonderfully summarized as well. It really seems to fly in
the face, doesn't it? Of the way we've been discussing
personalized medicine and saying that we're going to start whole
genome sequencing everyone and that's going to provide all the
answers for future disease risks. I mean, if I'm not wrong, what
your paper is trying to tell us is that at this moment we don't
have good examples where genetic testing may trump clinical
diagnoses, and in fact we should be still focusing on a
comprehensive clinical evaluation of patients and in the absence
of a genotype we should learn to question what we're doing in
genetic testing. Do you agree with that?


Dr Sanjay
Sharma:           
You couldn't have said that more precisely. As I've said, the
diagnostic yield of clinical testing was 21% versus only 10% with
genetic testing. The diagnostic yield of pure genetic testing in
people with otherwise completely normal findings clinically was
only 2.5%. And the other thing that I forgot to tell you was that
genetic testing, if we included genetic testing in addition to
comprehensive assessment, cost us three times as much as clinical
investigation on its own, and had we relied solely on genetics,
and nothing else, it would have cost us ten times more than
clinical testing. So our cost per making a diagnosis using
genetics only would have amounted to $30,000 per condition.


Dr Carolyn
Lam:               
Wow, what a great wake up call. Mark, you've thought a lot about
this and in fact there was another paper in this week’s journal
that has very complimentary messages. In fact you invited an
editorial by Dan Roden, and I really loved his title of it,
"Growing Pains in Cardiovascular Genetics." Would you maybe add
your thoughts in relation to the other paper, as well as overall?


Dr Mark
Link:                    
Sure. Circulation was very interested in these papers. These are
really  ... Now, as Dan Roden says, "Growing pains." Twenty
years ago when genetics came out it was looked upon as it was
going to completely change our clinical medicine and precision
medicine is really relying a lot on genetics. And while
ultimately that may be the case, we are in a stage now where the
honeymoon is over. And the other paper that was in this same
issue was a paper by Hosseini  and colleagues, and it was
the Clin Gen paper looking at the Brugada Syndrome abnormalities.
Now the Clin Gen is an NIH sponsored group that takes individuals
from a number of different institutions and actually gene
testing, and tries to provide an independent assessment of the
abnormality of genes. Previously is was companies that did this.
A company would gene test ... They would look for gene
abnormalities, try to link it with clinical disease, and they
could basically then do just on their patients. But Clin Gen now
is trying to tie all those companies together to get a broad
consortion and to look at genetic abnormalities and whether
they're truly pathologic, where there's areas of unknown
significance, or whether they're truly not pathologic.


                                               
So as an example, they took Brugada Syndrome, and they took the
different gene abnormalities that have been described from
basically different companies and different labs and different
institutions, and they looked at the evidence behind the fact
that they were truly pathologic, 'cause all 21 genes were defined
as pathologic. They found in their independent assessment that
only one ended up to be truly pathologic, and the others ones
were disputed. And sort of another wakeup call that just because
a single company calls a gene pathologic or Brugada Syndrome,
does not make it pathologic necessarily. So we all thought these
were two very important papers that looked at some of the
limitations of genetic testing. We asked Dan Roden, who is really
a very accomplished scholar in this field, to provide perspective
on this. And I agree, I loved his title, "Growing Pains in
Cardiovascular Genetics." And what he did is reviewed the history
of genetic testing, and he actually starts before genetic testing
and starts with Mendelian genetics, and [inaudible] genetics. And
then 23 years ago they started linking that Mendelian genetics to
gene abnormalities, especially in diseases such as long QT
syndrome and hypertrophic cardiomyopathy.


                                               
We've come a tremendous way in diagnosing gene abnormalities and
associating them with these underlying cardiac myopathies and
hind channel abnormalities. So no one doubts we've come a
tremendous way, but there's a long way to go in terms of getting
better diagnostic accuracy and really defining where these
genetic testing are ultimately going to play out in clinical
medicine. So everyone's excited about it, but I think these two
papers are two cautionary tales that we do have to remember that
genetic testing in 2018 is not the end all and be all.


Dr Carolyn
Lam:               
I love that, cautionary tales. So important. But where do we go
from here? What's the take home message for clinicians listening
to this today in 2018? I mean is it that perhaps when we do these
things we now need to include medical geneticists and genetic
counselors as vital partners as we look at this all? Perhaps we
need to not forget the primacy of clinical evaluation. What do
you think, Sanjay?


Dr Sanjay
Shar:                 
Well, there are guidelines from the American Medical Genetics
side as to what one defines as a disease-causing mutation. But I
agree that we need to be using certified laboratories that can
actually interpret the genetic mutations. For example, in our
study of athletes, 63% actually had variance of undetermined
significance. So they had spinning mistakes in their genes which
probably didn't account to anything at all, but had these
mutations, or these so called variance of undetermined mutations
been interpreted by someone who didn't really know much about
this, these could have resulted in false positive results which
could cause absolute chaos for an athletes career. So I do think
this type of testing has to be governed very, very carefully and
needs to be performed in very specialized and certified
laboratories.


Dr Carolyn
Lam:               
Indeed. Not just to the athlete, but to their families too, isn't
it? Mark, what do you think is the take home message [inaudible
00:16:18]?


Dr Mark
Link:                    
I think one of the big take home messages that I took away from
these papers is that clinical medicine is not dead. In fact,
clinical medicine in this day and age is still the prime way of
taking care of patients. Genetic testing is still in its infancy.
It doesn't help clinically in too many situations yet. It will in
the future. It helps in the diagnosis, it's not as useful in the
treatment. So we have a long ways to go with genetics. I like
your comment that going forward we're going to need more genetic
counselors to make sense of these results. Clinicians are going
to have a hard time making sense of these results. I do think
that there is plenty of role once a disease causing mutation has
been defined, and in that situation it's invaluable in cascade
screening in identifying other family members who may be
affected, but outside that I do believe and I agree completely
with both of you, that clinical medicine is not dead. And
clinical evaluation should be number one and should enjoy it's
prime time because that's where we still are at. And genetics is
still in its infancy and so is cardiology.


Dr Carolyn
Lam:               
Perhaps in selective settings ... We're not talking here about,
for example, hypercholesteremia variance, we're not talking about
cancer gene variance for which screening may be a little bit more
advanced, and we may understand the gene phenotype associations
that are perhaps-


Dr Mark
Link:                    
I think that understanding gene phenotype associations are going
to be critically important in the future. I think, as Sanjay
said, the real use of genetic screening now is cascade screening
for the family, and there it's invaluable. That you can tell if
you've got a co-band with the disease, and with a defined
pathological mutation. You can test siblings, sons and daughters,
parents to see if any of them have the gene. I think that's where
it should be used for sure in 2018.


Dr Carolyn
Lam:               
Thank you so much Mark and Sanjay. So some precautions, some
hope. Very, very balanced discussion. So much more we could
discuss, so I really want to highly encourage our audience. Pick
up this issue. You have to read these amazing papers and the
editorials.


Dr Carolyn
Lam:               
So, here's a podcast with all your colleagues, and don't forget
to tune in next week.