Clinical Context
In 2010, high blood pressure was the leading risk factor for the overall
burden of disease worldwide. High-income countries have recently experienced
reduced cardiovascular mortality, despite increased prevalence of patients
living with cardiovascular disease, thanks to the more widespread use of
preventive drugs.
Previous studies have not examined the associations of blood pressure with
various types of incident cardiovascular disease in a contemporary population.
The goal of this study was to determine whether blood pressure was associated
with 12 different manifestations of cardiovascular disease and whether
associations varied by age and by systolic vs diastolic elevations.
Study Synopsis and Perspective
New data from a UK study including 1.25 million patients in a primary care
setting has drummed home the substantial burden of hypertension and identified
some new observations on how blood pressure affects 12 different manifestations
of cardiovascular disease, including various forms of stroke.
It finds that a 30-year-old patient with hypertension has a large increase in
lifetime risk for a cardiovascular event compared with a normotensive individual
(63% compared with 46%) and will develop cardiovascular disease an average of 5
years earlier.
The researchers, led by Eleni Rapsomaniki, PhD, from the Farr Institute for
Health Informatics Research, London, United Kingdom, reported associations of
blood pressure with a substantially wider range of incident cardiovascular
diseases than seen before, across a broader age range (including people younger
than 40 years) and a wider range of blood pressure values (including less than
115/75 mm Hg).
For nearly all cardiovascular diseases, there was a linear relation between
systolic or diastolic blood pressure with outcomes at all ages, further
supporting the absence of a J-shape curve, even in the elderly.
Senior author Harry Hemingway, MD, also from the Farr Institute for Health
Informatics Research, commented to
Medscape Medical News: "We have
produced a treasure trove of data. This is the largest database ever produced on
how blood pressure is related to cardiovascular disease. Because we had data on
so many patients we could separate out many different clinical pathologies and
see how systolic and diastolic blood pressure was related to them. We were also
able to look across a wider range of blood pressures than has been done before.
This is like improving the magnification in the lens of a microscope to
establish greater detail."
He added: "This is contemporary data (up to 2010) from clinicians recording
information on real everyday patients in clinical practice. It faithfully
replicates what we already know, which proves validation, and it also identifies
new associations not examined before."
The study
appears in the May 31 issue of
The Lancet.
In an
accompanying comment, Professor Thomas Kahan, MD, from the
Karolinska Institute, Stockholm, Sweden, says the study provides important new
information to improve risk assessment, patient counseling, and decision making
for patients with hypertension, and he concludes that, "The clinical benefit of
improved risk assessment and appropriate treatment might be substantial."
For the study, researchers analyzed data on blood pressure from electronic
medical records and linked those results to other databases on hospital
admissions and deaths resulting from 12 different presentations of
cardiovascular disease.
Noting that substantial debate has surrounded the benefits of treating mild
hypertension in young people, the researchers state, "In the absence of
long-term randomized trials, our estimates of lifetime risk and cardiovascular
disease-free years of life lost provide epidemiological evidence of substantial
morbidity associated with raised blood pressure, irrespective of the starting
baseline risk."
They point out that their data on how blood pressure relates to the 12
cardiovascular conditions at various ages can be used to extend the existing
counseling of patients and decision making, which is currently based on heart
attack and stroke risks alone. They say this "will help to focus guidelines and
clinicians to the disease areas in which screening and treatments are more
likely to have an effect."
For example, they point out that of the 5 years of cardiovascular
disease–free life lost associated with hypertension, nearly half were
attributable to stable and unstable angina, whereas in patients aged 80 years
and older, heart failure accounted for nearly a fifth of the years of life
lost.
Although most of the 12 cardiovascular outcomes investigated correlated
better with systolic pressure (with the strongest associations being seen for
stable angina and intracerebral and subarachnoidal hemorrhage), abdominal aortic
aneurysm (AAA) was weakly associated with systolic pressure and much more
strongly associated with diastolic pressure. Professor Hemingway suggested that
this observation may improve the selection process for AAA screening.
The authors also found that the age-specific relevance of blood pressure
depends on which disease outcome is studied. For example, in patients older than
80 years, stroke, myocardial infarction (MI), and peripheral arterial disease
(PAD) were strongly associated with raised blood pressure, whereas unheralded
coronary death was not.
"Our data shows that PAD is a common initial presentation of cardiovascular
disease in the elderly," Professor Hemingway commented. "This condition has not
been well represented in clinical trials in recent years, but our data suggests
it should be."
Risk More Important Than Numbers
Another paper in the same issue reports that treatment rates
for hypertension have almost doubled and control rates have tripled in England
between 1994 and 2011, resulting in the saving of tens of thousands of lives
each year.
Although the investigators, led by
Emanuela Falaschetti, MSc, from Imperial College London in the United Kingdom,
and the authors of the accompanying comment suggest this is a cause for
optimism, a
Lancet editorial points out that control was achieved
in only 37% of patients in 2011 and concludes that, "Clearly, a more concerted
effort and different approaches are needed urgently."
Professor Hemingway agrees with the
Lancet editorial, pointing out
that control of blood pressure is not synonymous with normalization of risk. "If
we are doing well with hypertension management, then the risk of cardiovascular
disease would be the same whether the patient had a history of hypertension or
not. But this is definitely not the case," he told
Medscape Medical
News.
He added: "Clinicians talk about blood pressure control, meaning that the
numbers have been brought back into a certain range. But patients don't care
what their numbers are. They care about their risk of MI, stroke, PAD, etc. In
our study, we show that among people with hypertension — some controlled, some
not controlled — there is a strong association with lifetime risks of many
different cardiovascular conditions.
"It is not just about the blood pressure numbers. They must be interpreted
within the wider context of overall cardiovascular risk. It is clear that more
needs to be done. We need better strategies to lower blood pressure and
cardiovascular risk and more support to clinicians to help them implement these
strategies."
Professor Hemingway believes the electronic health record is a good place to
focus these strategies and support.
"We could build in tools in the records to prompt clinicians to ask certain
questions and consider overall cardiovascular risk when assessing blood
pressure," he noted. "We could also display the risks to the patient and show
how the risks are reduced with various interventions. There is an awful lot more
we can do with electronic health records."
The study by Rapsomaniki et al was funded by the Medical Research
Council, National Institute for Health Research, and Wellcome Trust. The authors
have disclosed no relevant financial relationships. The study by Falaschetti et
al received no funding. Falaschetti has disclosed no relevant financial
relationships; disclosures for the coauthors appear in the article
.
Professor Kahan reports he has received research grants from Celladon,
Medtronic, Pfizer, and Servier.
Study Highlights
- The cohort for this study consisted of 1.25 million patients who were at
least 30 years old and who had no cardiovascular disease at enrollment.
- The investigators identified this cohort using linked electronic health
records from 1997 to 2010 in the CALIBER (Cardiovascular Research Using Linked
Bespoke Studies and Electronic Health Records) program.
- Of patients in the cohort, 20% were treated with blood pressure–lowering
medications.
- The investigators examined the heterogeneity in the age-specific
associations of clinically measured blood pressure with 12 acute and chronic
cardiovascular diseases.
- They also estimated the lifetime risks (up to age 95 years) and
cardiovascular disease–free life-years lost, after adjustment for other risk
factors at index ages 30, 60, and 80 years.
- There were 83,098 initial cardiovascular disease presentations during
follow-up (median duration, 5.2 years).
- People with systolic blood pressure of 90 to 114 mm Hg and diastolic blood
pressure of 60 to 74 mm Hg had the lowest risk for cardiovascular disease in
each age group.
- There was no evidence of a J-shaped increased risk for cardiovascular
disease at lower blood pressures.
- For various cardiovascular disease endpoints, the effect of high blood
pressure varied from strongly positive to no effect.
- The strongest associations with high systolic blood pressure were for
intracerebral hemorrhage (hazard ratio [HR], 1.44; 95% confidence interval [CI],
1.32 - 1.58), subarachnoid hemorrhage (HR, 1.43; 95% CI, 1.25 - 1.63), and
stable angina (HR, 1.41; 95% CI, 1.36 - 1.46).
- The weakest association with high systolic blood pressure was for AAA (HR,
1.08; 95% CI, 1.00 - 1.17).
- Elevated systolic blood pressure had a greater effect on angina, MI, and PAD
than did diastolic blood pressure.
- However, elevated diastolic blood pressure had a greater effect on AAA than
did elevated systolic pressure.
- Pulse pressure was inversely associated with AAA (HR per 10 mm Hg, 0.91; 95%
CI, 0.86 - 0.98).
- Pulse pressure was directly and most strongly associated with PAD (HR, 1.23;
95% CI, 1.20 - 1.27).
- Lifetime risk of overall cardiovascular disease at age 30 years was 63.3%
(95% CI, 62.9% - 63.8%) in people with hypertension (blood pressure ≥140/90 mm
Hg or treatment with blood pressure–lowering drugs) compared with 46.1% (95% CI,
45.5% - 46.8%) for those with normal blood pressure.
- People with hypertension developed cardiovascular disease 5.0 years earlier
(95% CI, 4.8 - 5.2 years) than those with normal blood pressure.
- For persons having hypertension from index age 30 years, stable and unstable
angina accounted for 43% of the cardiovascular disease–free years of life
lost.
- For persons having hypertension from index age 80 years, heart failure and
stable angina each accounted for 19% of years of life lost.
- The investigators concluded that their findings do not support conventional
wisdom that blood pressure has strong associations with all cardiovascular
diseases across a wide age range, and that diastolic and systolic associations
are concordant.
- They also note the substantial lifetime burden of hypertension despite
modern treatments, as well as the need for new blood pressure–lowering
strategies.
Clinical Implications
- Findings of a large cohort study do not support conventional wisdom that
diastolic and systolic associations with cardiovascular diseases are
concordant.
- These findings also support varying associations of blood pressure with
different cardiovascular diseases at different index ages for hypertension.
Despite modern treatments, hypertension carries a substantial lifetime burden,
highlighting the need for new blood pressure–lowering strategies.
Fuente: http://www.medscape.org/viewarticle/827735?nlid=62704_2802&src=cmemp
