Aug 8, 2016
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.