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Recent advances in medical
science make previous notions of hypertension
barely recognizable today. Although hypertension
is widely misunderstood, often ignored, and
generally under-treated, this incredibly
important facet of health and well-being can be
your passport to cardiovascular disease
prevention.
High blood pressure can be
imperceptible, insidious, and sometimes
inscrutable.
Too often, people deny that
they have high blood pressure. “I’m nervous,” or
“I fought traffic to get here,” or “Wait until I
relax a little while and it’ll come down,” are
common reactions of those advised that their
blood pressure is too high.
If you truly have high blood
pressure, you are not alone. Without
intervention, high blood pressure is likely to
affect most of us at some point in our lives.
With age and declining health, high blood
pressure can be as inevitable as death and
taxes. Even if you are non-hypertensive at the
age of 55, the Framingham Heart Study predicts a
90% likelihood that you’ll be hypertensive
within your lifetime.
Too often, discussion
about hypertension degenerates into a mandate
for prescription medication, once the obligatory
comments about eating a healthier diet, reducing
salt intake, and quitting smoking are out of the
way. It is no secret to the medical community
that conventional blood pressure treatment does
not fully eliminate the risk of suffering
cardiovascular events from hypertension.1
In other words, threats to health from high
blood pressure often remain uncorrected even
when blood pressure appears to be fully
controlled by medication.
From Bloodletting to
Metabolic Syndrome
In the late nineteenth
century, Dr. Carl Ludwig first devised a
technique for measuring blood pressure that
required the insertion of a tube into an artery,
allowing blood to flow into a manometer. Not
until the turn of the twentieth century did the
sphygmomanometer became available. This device
for measuring blood pressure did not require
puncturing a blood vessel and was therefore
useful for everyday purposes. In 1912, the
Massachusetts General Hospital in Boston began
mandatory blood pressure measurements for all
patients admitted to its wards.
Progress in treating high
blood pressure has lagged behind techniques for
measuring it. Even in Ludwig’s day, some
practitioners advocated bloodletting to allow
high pressure to dissipate. As recently as the
1960s and 1970s, hospital wards were filled with
patients suffering uncontrolled, perilous levels
of hypertension (“hypertensive crises”) due to
the broad failure of the medical community to
recognize and treat earlier phases of high blood
pressure. Treatment choices were likewise
limited and flawed.
Our understanding of blood
pressure has advanced considerably since these
early observations. Today, medicine has
improved, though it is certainly not foolproof.
Even better, breakthroughs in the science of
regulating blood pressure are revealing many
promising nutrition-based approaches for
preventing and controlling high blood pressure.
Some of the most exciting recent insights
revolve around the role of nitric oxide, a
master controller of blood pressure, and the
frightfully common cluster of health disorders
known as metabolic syndrome, an eminently
correctable factor in blood pressure control.
What Is Normal Blood
Pressure?
In the 1960s and 1970s, the
medical profession used arbitrary guidelines
that grossly underestimated the perils of
hypertension. For example, a rule practiced in
the 1970s held that an “allowable” blood
pressure value could be calculated by adding 100
to a person’s age. By this formula, a
60-year-old adult woman would be permitted a
systolic blood pressure of 160 mmHg before her
physician would become concerned. We all know
now that a blood pressure like this virtually
guarantees complications of high blood
pressure—such as stroke, dementia, and kidney
failure—within a few short years.
Why such confusion about
acceptable blood pressure levels? The dilemma
arises in part because blood pressure is
variable. In the morning, just before arising,
your systolic/diastolic blood pressure might be
104/78 mmHg. After eating breakfast and having
coffee, it could change to 128/74 mm Hg. While
sitting at your desk at work, having more
coffee, answering email, and making phone calls,
your level could rise to 149/79 mmHg. An
annoying comment from a customer could push your
blood pressure to 164/68 mmHg. After blowing off
steam with a friend, walking 200 feet to another
part of the building, looking at the picture of
your family on your desk, and reminding yourself
that there is more to life than work, your blood
pressure might then drop to 130/70 mmHg.
No one’s blood pressure stays
constant at the optimal level of 120/80 mmHg or
lower. Blood pressure fluctuates widely, even in
people with normal levels. People without high
blood pressure will fluctuate into clearly
abnormal ranges during periods of emotional
stress, overindulgence in unhealthy foods or
alcohol, and physically demanding activities.
This does not mean they have high blood
pressure.
Then how do we define high
blood pressure if even those with normal blood
pressure occasionally trespass into high levels?
High blood pressure does not
necessarily mean constantly and persistently
high. People with high blood pressure tend to
fluctuate more widely. Differences of 60-80 mmHg
within just a few minutes are common. The “give
me a few minutes to calm down” comment that
allows systolic blood pressure to drop from 180
to 120 mmHg simply reflects this phenomenon in a
hypertensive individual. High blood pressure
also stays higher longer and rises above normal
more frequently. In other words, for
hypertensive people, the peaks and valleys of
blood pressure are higher, broader, and more
numerous than for those with normal pressure.
The ideal way to measure blood pressure is to
have somebody follow you throughout the day and
measure your blood pressure under all sorts of
different circumstances. Unfortunately, this
approach is impractical.
One practical way to gauge
overall blood pressure behavior is to wear an
ambulatory blood pressure monitor. This device
is worn for 24 hours, and automatically measures
and records blood pressure every 15 minutes. Its
readings are then reviewed by a physician.
Another way is a stress test, since graded
exercise’s effects on blood pressure can be
observed while the patient walks on a treadmill.
Both tests show the extremes of blood pressure
fluctuations and offer a good idea of whether
you truly have high blood pressure when faced
with the stressors of everyday life.
The last option is to simply
measure your blood pressure the old-fashioned
way, while sitting in your doctor’s office. You
can improve on this by adding measures of your
own (with an automatic blood pressure cuff or
measured by a friend) at different times and
under varied circumstances, such as at home,
upon awakening, and following exercise. This
will gives you a reasonable idea of everyday
fluctuations in your blood pressure. However,
you should expect variations in pressure,
regardless of whether you have high blood
pressure.
Another reason for confusion
over elevated blood pressure arises from its
“silent” nature. Only occasionally does high
blood pressure cause symptoms like headache or
fatigue. The vast majority of those with lurking
hypertension feel just fine, with no symptoms at
all. Perhaps that is why we question, argue
with, and resist a diagnosis of high blood
pressure.
Blood Pressure’s Ebb and
Flow
What exactly is blood
pressure? Put simply, it is the force with which
blood is propelled through your arteries. Unlike
a river, which flows continuously downstream,
blood flow is pulsatile, with the ebb and flow
driven by the pumping heart muscle. The heart
muscle squeezes forcefully, propelling blood
forward. The heart then relaxes and blood flow
ebbs momentarily. This cycle repeats itself with
each heart-beat, 60 or so times each minute.
Blood pressure, therefore, is
the pressure contained within your arteries,
with a forward burst of flow from heart
contraction called systolic pressure, and the
receding flow of heart relaxation called
diastolic pressure. A blood pressure measurement
of 120/80 mmHg signifies a systolic value of 120
and a diastolic value of 80, measured in the
pressure units of milligrams of mercury.
You can deduce many of the
causes of high blood pressure just by
understanding this basic process. For instance,
pour a greater volume of fluid into the system,
and systolic pressure goes up because each
contraction of the heart delivers greater
volume, and the diastolic pressure goes up
because there is more volume to fill the
arteries and less room to dissipate pressure
during heart relaxation. Several disorders cause
fluid retention in your circulatory system and
thereby cause high blood pressure. These include
excessive salt intake, poor kidney function, and
high levels of certain hormones like renin,
angiotensin, and cortisol.
Another factor is arterial
flexibility or stiffness. Normally, arteries are
flexible and “give” with pulsatile blood flow.
However, when these vessels are stiff, they are
less able to expand with bursts of flow, and
pressure increases. This is common in arteries
lined with semi-rigid atherosclerotic plaque,
also known as “hardening” of the arteries.
Regardless of their cause,
all forms of blood pressure can eventually lead
to the same undesirable effects. High blood
pressure pounds your organs with each heartbeat,
hour after hour, day after day. Over the years,
the effects of this relentless trauma begin to
show. In the kidney, the ability to filter the
body’s waste products and separate excess fluid
from blood weakens. In the heart, coronary
arteries develop plaque that leads to heart
attack. Heart muscle becomes overly thick and
muscular, internal heart pressure increases, and
you become breathless and retain fluid, a
condition called diastolic dysfunction. The
arteries of the chest and abdomen, and
particularly the major artery of the body, the
aorta, also develop plaque. The aorta enlarges,
essentially “inflating” under the increased
internal pressure of hypertension, leading to
the formation of aneurysms. In the brain, the
relentless pounding of high blood pressure can
lead to deterioration of brain tissue,
eventually leading to a form of dementia called
multi-infarct dementia that arises from many
mini-strokes.
Is “Normal” Blood Pressure
Too High?
“We have taken it as the
natural human condition that blood pressures are
as high as they are. We have arbitrarily defined
‘normal blood pressure.’ But that does not mean
that normal is optimal.”
—Dr. Henry R. Black,
Rush University Medical Center
At what point does
blood pressure begin to have demonstrable
effects on cardiovascular complications and
mortality itself? At a systolic pressure of 150
mmHg? How about at 140 mmHg? In fact, measurable
complications of blood pressure begin to appear
at just 115 mmHg! That is, systolic pressures
above 115 mmHg are sufficient to generate damage
to arteries and other organs, with measurable
impacts on morbidity and mortality over a period
of several years.2
Every additional
increment in blood pressure of 20/10 mmHg
doubles one’s risk of developing cardiovascular
disease. For this reason, the most recent
national guidelines for blood pressure issued by
the National Heart, Lung, and Blood Institute
recommend maintaining a systolic blood pressure
under 120 mmHg and a diastolic pressure below 80
mmHg. Values at or above 140/90 mmHg are
considered hypertensive, requiring medical
intervention. The new guidelines provide for a
category called “pre-hypertension”— defined as
systolic pressures of 120-139 mmHg and diastolic
pressures of 80-89 mmHg—that justifies lifestyle
modification for improvement.1
The recent release of the
Camelot Study conducted by Dr. Steven Nissen of
the Cleveland Clinic has fueled the argument
that lowering blood pressure even moderately
yields substantial health benefits. In this
study of nearly 2,000 participants with heart
disease, lowering blood pressures within the
borderline range from 129/78 to 124/76 mmHg led
to significant reductions in heart attack,
death, and hospitalization. This blood pressure
reduction also decreased arterial plaque growth,
as measured by intra-coronary ultrasound.3 It is
interesting to contemplate what the potential
effects of lowering blood pressures to 100 mmHg
would be, and perhaps future clinical trials
will answer this question for us.
Hypertension: A Twenty-First
Century Epidemic
Look down the aisles at
your neighborhood grocery store and you will see
why 47 million adults in the US, or about one of
every four, have the cluster of disorders dubbed
metabolic syndrome. Ninety percent of the
products on the supermarket shelves are highly
processed foods that are rich in unhealthy fats,
loaded with sugar, and depleted of fiber.
Combine these foods with lifestyles marked by
inactivity, sleep deprivation, and stress, and
you create a constellation of physiological
phenomena that includes abdominal obesity, low
levels of beneficial HDL (high-density
lipoprotein), high levels of harmful
triglycerides, elevated blood sugar, and high
blood pressure. So many adults in the US meet
the diagnostic criteria for metabolic syndrome
that the total number now afflicted nearly
equals the number of “baby boomers.”4
If you have
hypertension, there is a high likelihood that
you have at least some of the characteristics of
metabolic syndrome, particularly resistance to
insulin, a condition that precedes development
of full-blown diabetes. In fact, the association
is so strong that hypertension should be
regarded as a significant risk factor for future
diabetes, with a greatly increased risk of
diabetes in your future.5
Moreover, the estimate
of 47 million US adults with metabolic syndrome
is based on the rather lax definition of
hypertension as a blood pressure greater than
140/90 mmHg. Many truly hypertensive people will
be uncounted using this guideline. As noted
earlier, blood pressure is, by its nature,
labile and variable. It is also clear that blood
pressure begins to affect mortality rates at
levels above 115 mmHg. Most people are shocked
when they hear this, having been accustomed to
hypertension guidelines specifying levels of
150/90 mmHg and higher. To remind ourselves of
what optimal blood pressure should be, we need
only look at blood pressure levels in primitive
cultures that lack access to processed foods and
are engaged in physical activity much of the
day. People in these cultures, who rarely suffer
from cardiovascular disease, have blood
pressures of around 90/60 mm Hg.2
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