Circulation August 9, 2016, Issue

 


Carolyn:
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 National Heart Center and Duke
National University in Singapore. Joining me today will be Dr.
Katherine Mills and Dr. Andrew Moran to discuss the very striking
findings of a new study on global disparities of hypertension
prevalence and control, but first, here's the summary of this
week's original papers.


 
 
In a study by first author, Dr. [Lu 00:00:42], corresponding
author, Dr. Denny, from the Harvard TH Chan School of Public
Health in Boston, Massachusetts and colleagues, authors aimed to
investigate how the risk of cardiovascular disease is distributed
among whites and blacks in the United States and how
interventions on cardiovascular risk factors would reduce these
racial disparities. To achieve these aims, the authors used a
nationally representative sample of more than 6,000 adults, age
50-69 years of age, in the United States and developed a risk
prediction model that was calibrated separately for blacks and
whites.


 
 
The main results were that were substantial disparities in the
risk of fatal cardiovascular disease; 25% of black men and 12% of
black women were at high risk of fatal cardiovascular disease
compared to only 10% of white men and 3% of white women,
respectively. A large proportion of these fatal cardiovascular
events among blacks were concentrated among this small proportion
of the population. Now, whereas, population wide and
interventions focused on single risk factors did not reduce
black/white disparities in fatal cardiovascular risk and
intervention that focused on high-risk individuals and reduced
multiple risk factors simultaneously could indeed reduce
black/white disparities in fatal cardiovascular disease by a
quarter in men and a third in women.


 
 
These results really emphasize that focusing preventative
interventions on the high-risk individuals has a large potential
to improve overall cardiovascular health and reduce racial
disparities in the United States.


 
 
The next paper is from first author, Dr. Lee, corresponding
author, Dr. Federer, from Ohio State University Wexner Medical
Center in Columbus Ohio and colleagues who looked at the issue of
adenosine-induced atrial fibrillation and aimed to elucidate the
molecular and functional mechanisms that may underlie this
problem. To achieve this aim they integrated panoramic optical
mapping and regional immunoblotting to allow them to resolve the
protein expression of the two main components of the adenosine
signaling pathway, mainly the A1R and GIRK4. They found that
these signaling pathways were 2-3 times higher in the human right
atrium compared to the left atrium leading to a greater right
atrial action potential duration shortening in response to
adenosine.


 
 
Furthermore, they showed that sustained adenosine-induced atrial
fibrillation is maintained by re-entrant drivers localized in the
lateral right atrial regions with the highest A1R and GIRK4
expression. Finally, the authors demonstrated that selective GIRK
channel blockade successfully terminated and prevented atrial
fibrillation. Thus, suggesting that the arrhythmogenic effect of
adenosine in human atria may be mediated by activating GIRK
channels. The take-home message, therefore, is that specific
blockade of the GIRK channels may offer a novel mechanism to
prevent adenosine mediated atrial fibrillation in patients.


 
 
The next study is from Dr. Nielsen and colleagues from the
Copenhagen University Hospital of Bispebjerg in Copenhagen,
Denmark, who aimed to assess the optimal blood pressure in
patients with asymptomatic aortic valve stenosis. To achieve this
aim, the authors used data from the simvastatin, ezetimibe in
aortic stenosis or SEAS trial of 1,767 patients with asymptomatic
aortic stenosis and no manifest atherosclerotic disease. Outcomes
that were studied included all-cause mortality, cardiovascular
death, heart failure, stroke, myocardial infarction, and aortic
valve replacement. The main findings were that an average
diastolic blood pressure above 90 and a systolic blood pressure
above 160 millimeters mercury were associated with a poor
outcome.


 
 
Furthermore, low systolic blood pressure was also related to
adverse outcomes while low average diastolic blood pressure was
harmful in moderate aortic stenosis. In summary, the optimal
blood pressure, which was associated with the lowest risk of
adverse outcomes, were the systolic blood pressure between 130
and 139 and a diastolic blood pressure between 70 and 90
millimeters mercury. The clinical take-home message is that in
the scarcity of randomized controlled evidence, these results may
assist clinicians in their decisions in blood pressure
measurements in patients with aortic stenosis, meaning that a
blood pressure above 149D may be treated while a blood pressure
lower than 120 systolic or 60 diastolic may be recognized as a
warning signal for poor outcomes.


 
 
That was the summary of this week's original papers. Now for a
discussion of our feature paper.


 
 
I am so excited to be joined by two guests today to discuss our
feature paper entitled Global Disparities of Hypertension
Prevalence and Control, a systematic analysis of population-based
studies from 90 countries. We are so pleased to have the first
author, Dr. Katherine Mills, from Tulane University School of
Public Health and Tropical Medicine in New Orleans. Welcome,
Katherine.


 
Katherine:
Thank you. Good morning.


 
Carolyn:
And a very special occasion indeed, we have an editorialist
joining us, as well, in none other than Dr. Andrew Moran from
Columbia University Medical Center in New York. Welcome, Andrew.


 
Andrew:
Good morning. Thank you, Carolyn.


 
Carolyn:
It's wonderful to have you discuss this. This paper has so many
key findings that really struck me. If you don't mind, I am just
going to summarize some of these. For example, Katherine, you
reported globally more than 30% of the adult population,
amounting to almost 1.4 billion people have hypertension in 2010,
and the prevalence of hypertension was higher in low and middle
income countries than in the high income countries, making it,
therefore, that approximately 75% of people living with
hypertension live in the low and the middle income countries.
Yet, hypertension awareness, treatment, and control were much
lower in the low and middle income countries compared to the high
income countries. That is really striking. Katherine, I'd really
love for you to share with us what was the inspiration to look at
this and what do you think was the most striking finding?


 
Katherine:
We know that hypertension is a very important risk factor for
cardiovascular and kidney disease. It's the leading cause of
cardiovascular disease in the world and for premature death. A
previous study in our research group found that about 26% of the
world's adult population had hypertension in 2000, but since then
there really hasn't been any global estimate made. Basically,
since 2000, a lot of studies from individual countries and high
income countries have shown a leveling off or decrease of
hypertension prevalence, but studies from individual low and
middle income countries have actually shown an increase in
hypertension prevalence.


 
 
Given these trends in individual countries and the importance of
hypertension prevalence and treatment and control, to prevent
cardiovascular disease, we really wanted to look and see what the
disparities were in high income compared to low and middle income
countries. I think the most striking findings to me was that we
found that over 75% of adults with hypertension globally are in
low and middle income countries, and that's over a billion
people. We also found that only 7.7% of those people with
hypertension and low and middle income countries have controlled
hypertension. That represents a huge global public health problem
that could lead down the road to a large burden of cardiovascular
and kidney disease if it's not effectively addressed.


 
Carolyn:
Katherine, I could not agree with you more because it's actually
a living reality that I'm seeing where I come from in Asia. We
have just so much hypertension, and what struck me was that from
2000 to 2010, while the prevalence increased here, it decreased
in high income countries. Yet, this is where the greatest need is
and where the control is the lowest. That was striking. Can you
just articulate a bit further how your data now add to the
knowledge that was there before your paper?


 
Katherine:
Basically, this is the first paper to show that the prevalence of
hypertension is higher in low an middle income countries compared
to high income countries. It's the first paper since 2000 to
quantify the global burden of hypertension, and it's the first
paper to really compare rates of awareness, treatment, and
control comparing high income to low and middle income countries.


 
Carolyn:
That is fantastic and really striking. I think that's why the
Circulation Editorial Board to invite an editorial by Andrew to
discuss this. Andrew, your editorial was entitled Still on the
Road to Worldwide Hypertension Control, and even in the first
sentence of your editorial, you mention that hypertension is a
preventable risk factor, and that's why this is so important. I
really like that your first subheading has this big word, action.
Maybe you could tell us a bit more. What are the implications of
these findings for worldwide hypertension control and actions
that we can take?


 
Andrew:
There's a growing attention to noncommunicable diseases worldwide
as a lot of maternal and fetal deaths, those rates have improved
worldwide, and so really as the world population ages, problems
like hypertension and related noncommunicable diseases are
becoming a bigger and bigger health problem for people around the
world, not just in high income countries. As a matter of fact,
recently the World Health Organization set a 25 by 25 goal,
meaning to reduce deaths from noncommunicable diseases by 25% by
the year 2025. A big part of that effort is going to be an effort
to control hypertension. The World Heart Federation has set a
goal of improving hypertension control by 25% as part of that
overall effort.


 
Carolyn:
Yes. You mentioned that I think in the editorial, as well, but
are there some action steps that we could take globally as a
community?


 
Andrew:
Yes. It's striking to me as a practicing physician that something
so basic as measuring blood pressure and recommending treatment
for people with elevated blood pressure, which is so integral to
our daily practice in medicine, that we still have so far to go
in achieving control both in high income settings and low and
middle income country settings. One of the most basic
cornerstones of achieving control is proper measurement of blood
pressure. I think one of the goal efforts has to involve making
sure that primary care settings and even community centers have
available well-calibrated and validated blood pressure
measurement devices and that people know how to measure blood
pressure accurately.


 
 
The other problems that come up with controlling hypertension are
for people who have a diagnosis that is accurately made, are they
able to follow up with a primary care provider to monitor their
blood pressure, and do they have medications available to them
that are affordable? It's important to note that especially in
low and middle income countries, most people have to pay for
their medications out of their own pockets, so the affordability
and availability of medications is a really important part of
achieving our goals. I think it's important to see that low and
middle income countries, even though it can seem like a daunting
setting in which to implement improvements in the quality of
healthcare delivery, there also important places to experiment
with improving the quality of care delivery worldwide.


 
 
For example, the concept of having a community health worker make
home visits and reach out into the community was something that
was developed in low and middle income countries and now is
becoming a popular and effective method of delivering care in all
countries worldwide.


 
Katherine:
One thing I would add is that I think we really need
collaborations from the international level because so many of
these low and middle income countries have very limited
healthcare resources, and there still dealing with a lot of
infectious diseases, so I think it really is going to take an
international effort to address this problem in low and middle
income countries.


 
Carolyn:
Thank you so much for joining us for another episode of
Circulation on the Run. Tune in next week for more summaries and
highlights.