Hypertension
or High Blood Pressure
Hypertension
is a "Silent Killer." This
is not a misnomer and it is not surprising that this disease is called as such. It is a medical condition known to mankind for ages, and it
has been studied extensively by epidemiologists and clinicians in recent years.
It can kill if not treated.
The
recommended care of patients with
Hypertension is based upon the findings from these studies.
Management of Hypertension requires skills from the health practitioner
in enlisting the patient's cooperation and in selecting and monitoring and
adjusting treatment.
The
arterial blood pressure is regulated by a variety of inter-dependent mechanisms.
Inadequately compensated alterations in any of these mechanisms can lead
to abnormal elevation of blood pressure. An
elevated arterial blood pressure is one of the most important public health
problems in developed countries. It
is common, a symptomatic and that is the reason why it kills.
Although it is readily detectable, easily treatable, it often leads to
lethal complications if left untreated.
The
prevalence of Hypertension depends on both racial composition of the population
and the criteria used to define the condition.
Hypertension occurs in more than 60 million Americans.
The prevalence in Caucasians is approximately 15 percent, but it is over
25 percent in the black population. This
marked racial difference in the rates of Hypertension remains somewhat
unexplained. The prevalence of
Hypertension also increases with advancing age.
Hypertension is more common in men than in women up to approximately age
50. the rate thereafter is higher
in women.
Genetic
factors have long been assumed to be important in the genesis of Hypertension.
Most studies done so far support the concept that inheritance is
multifactorial in that a number of different genetic defects each have an
elevated blood pressure as one of their phenotypic expressions.
Both monogenic defects and susceptibility genes have now been reported
which have as one of their consequences an increased arterial pressure.
Environmental
factors have also been implicated in the development of Hypertension, including
salt intake, obesity, occupation,
level of alcohol intake, family size and crowding.
The
measurable blood pressure of the general population demonstrates extreme
variance. There is a correlation
of mortality and morbidity with the level of systolic and diastolic blood
pressure. The correlation provides
the basis for the arbitrary definition of abnormal blood pressure.
A diagnosis of Hypertension is made in an adult over 28 years of age if
the average of two or more blood pressure measurements on at least two
subsequent visits is 90 mm hg or higher diastolic or 140 mm hg systolic.
The blood pressure in healthy children and pregnant women is typically
lower, so that readings in excess of 120/80 may be considered abnormal.
There is a condition called isolated systolic hypertension, which is
defined as a systolic blood pressure greater than 160 mm hg in association with
a diastolic blood pressure less than 85 mm hg.
It occurs more frequently in the elderly, beginning after the 5th
decade and increasing with age. It
is important to recognize that isolated systolic hypertension is associated with
increased incidence of cardiovascular and cerebrovascular complications and it
must be treated.
Classification of Blood Pressure for Adults Aged 18 Years And Older
Category Systolic Pressure (mm Hg) Diastolic Pressure (mm Hg)
Normal Less than 130 less than 85
High
Normal
130-139
85-89
Hypertension
Mild
140-159
90-99
Moderate
160-179
100-109
Severe
180-209
110-119
Very Severe Equal or greater than 210 Equal or greater than 120
Physiologic principles indicate that pressure is a direct function of flow and resistance. The blood pressure is related to the cardiac output and the peripheral vascular resistance. The cardiac output depends upon the contractibility of the myocardium, the heart rate and the intravascular blood volume. The regulation of normal blood pressure depends upon several interrelated factors that modulate the output and resistance. The autonomic nervous system is responsible for the regulation of abrupt hemodynamic alterations. Other humoral factors regulate the blood pressure and the most important being the renin-antiotensin-aldosterone system.
Despite the understanding of the mechanism regulating ambulatory blood
pressure, monitoring can be of value in the following circumstances:
Suspected "white coat" Hypertension in which the increased blood pressure is associated with the stress of physician office visits;
- high normal blood pressure 130-139 mm Hg systolic, 85-89 mm Hg diastolic, with target organ damage;
-
Evaluation of possible drug resistance during the course of treating;
-
Episodic Hypertension;
-
Hypotensive symptoms associated with medication or autonomic dysfunction.
What is target organ
damage?
Patients
with untreated or uncontrolled Hypertention develop target organ damage due to
longstanding effects of the increased blood pressure in the different organ of
the body, the cardiovascular system, with the heart as the main target, the
neurological system and the kidneys.
The most common cause of death is heart disease, stroke and renal
failure. Eye damage with
retinopathy is very common.
How to Take Blood Pressure Measurements.
Elevated
blood pressure is usually discovered in asymptomatic individuals during
screening - optimal detection and evaluation of hypertension requires accurate
non invasive blood pressure measurements which should be obtained in a seated
patient having the arm level with the heart.
A calibrated, appropriately fitting blood pressure cuff should be used
because falsely high reading can be obtained if the cuff is too small.
Two readings should be obtained separated by two minutes.
Systolic blood pressure should be noted with the appearance of korotkoff
sounds (phase I) and diastolic BP with the disappearance of sounds (phase V).
In certain patients, the korotkoff sounds do not disappear but will be
pressing to 0 mm Hg. In this case,
the initial muffling of korotkoff sounds (Phase IV), should be taken as the
diastolic blood pressure. Hypertension
should be confirmed in both arms and the higher reading should be used.
We
should also take into account the secondary causes of Hypertension, mostly the
presence of medication that may affect blood pressure:
decongestants, nonsteroidal anti-inflammatory agents, exogenous thyroid
hormones and recent high alcohol consumption.
The new electronically measured blood pressure monitoring are very
helpful and can be used by anyone.
Considerations for Therapy
Before
considering therapy, your health care practitioner will order laboratory
assessments, which will help him or her to identify possible target organ damage
and provide a baseline for assessing adverse effects of therapy.
Hyperlipidemia evaluation, evidence of diabetes, and assessment of
cardiac function are very important.
The
goal of treatment for Hypertension is to prevent long-term sequelae or target
organ damage. Virtually every
patient with a diastolic arterial pressure that persistently exceeds 90 mm Hg,
or a patient over 65 years of age with a systolic arterial pressure over 160 mm
hg is a candidate for diagnostic studies and for subsequent treatments.
The primary goal is to reduce blood pressure to less than 140/90 mm hg,
which concurrently controlling other modifiable cardiovascular risk factors.
Isolated systolic Hypertension is associated with increased
cerebrovascular and cardiac event. Therefore, the therapeutic goal in this subset of patients
should be to lower blood pressure to less than 140 mm Hg systolic.
General Measures
We
must depart from the principle that no hypertensive patients should be left
untreated except through his or her own volition.
Most
patients with Hypertension should be given the opportunity to achieve a
reduction in blood pressure over an interval of three to six months by applying
non-pharmacological modifications. The
general measures employed include:
1.
relief from stress;
2.
dietary management;
3.
regular aerobic exercises;
4.
weight reduction (if needed).
-
Relief from emotional and environmental stress is one of the reasons for
the improvement of Hypertension that occurs when a patient is hospitalized. It is impossible to extricate the hypertensive patient from
all internal and external stress. He
or she should be advised to avoid unnecessary tensions. In rare instances, it may be appropriate to recommend a
change of job or of lifestyle. It
has been suggested that relaxation techniques also may lower arterial pressure.
-
For dietary modifications, sodium restriction is an effective and safe
means of lowering blood pressure modestly in hypertensive patients.
Sodium restrictions also may decrease drug resistance and enhance
efficacy. Total sodium chloride
intake should be limited to 6 g. per day. The
use of potassium as a therapeutic agent is controversial, but may be of some
benefit. Normal serum potassium
levels should be maintained in patients with spontaneous or drug induced
hypokalemia. Dietary intake of
cholesterol and saturated fat should be reduced to lessen hyperlipidemia and to
facilitate weight loss.
-
Regular dynamic exercise is advised if the clinical status of the patient
permits. Repeated periods of
exercise result in a significant reduction of blood pressure independent of
weight loss or altered sodium excretion, decreasing all-cause risk and
cardiovascular morbidity and mortality. Exercise
should be performed at least 3 times per week for at least 30 minutes, achieving
65 to 70% of a patient's predicted maximum heart rate.
Patients with known or suspected coronary artery disease and those older
than 40 with multiple coronary risk factors should undergo exercise stress
testing before beginning an exercise program.
-
Weight reduction should be strongly encouraged in patients whose weight
exceeds 10% of their ideal body weight. Reduction
of body weight, especially male-pattern obesity involving the trunk and upper
body may obviate the need for drug therapy or decrease the amount of medication
required to control Hypertension. Weight
loss is no recommended for pregnant patients with Hypertension.
In summary, lifestyle modifications should be encouraged in all hypertensive
patients, regardless of whether they require medication.
These changes may have beneficial effects on other cardio-vascular risk
factors. Patients who smoke should
be advised to stop smoking because
cessation of smoking is an effective means of reducing cardio-vascular risk and
target organ damage. Alcohol
consumption should be decreased to 1 oz or less per day because, in large
amounts, ethanol has a direct vasopressor effect and can exacerbate
Hypertension.
Anti-Hypertensive
Drugs
I must point out that an individualized approach to therapy is more
favorable than the traditional stepped-care therapy.
A patient may have associated or inter-current conditions that must be
taken into account. To make
rational use of anti-hypertensive drugs, the sites and mechanism of their
actions, as well as their side effects must be understood.
There are six classes of drugs and note that the most commonly prescribed
of these drugs will be enumerated in this short piece:
-
diuretics;
-
antiadrenergic agents;
-
vasodilators;
-
calcium entry blockers;
-
angiotension - converting enzyme (ACE) inhibitors; and
-
angiotensive receptor antagonists.
Diuretics
The
most commonly used diuretics are the thiazides prototypes.
They have formed the cornerstone of most therapeutic programs designed to
lower arterial pressure and they are usually effective within three to four
days. They have been shown to
reduce morbidity and mortality in long-term trials.
Their early effect in the reduction of blood pressure is related to
sodium diuresis and volume depletion by inhibition of tubular NACL absorption.
Reduction in peripheral vascular resistance has also been reported.
Despite their usefulness in the management of Hypertension, there has
been increasing resistance in recent years to their continued use, primarily
because of their adverse metabolic effects, which include: hypokalemia due to
renal potassium loss, hyperucemia due to uric acid retention, carbohydrate
intolerance given hyperglycemia and hyperlipidemia.
In lower doses, these side effects are very much less common.
Furosemide,
Bumetamide produce also sodium diuresis and volume depletion, but are not used
extensively for Hypertension because of their short duration of action.
Furosemide is more useful in chronic renal failure.
Spironolactone,
triamterene and amiloride are potassium sparing diuretics that can be given
along with thiazide diuretics to minimize renal potassium loss.
Most common side effects of these potassium sparing diuretics are
hyperkalemia. Patients with renal
insufficiency or renal failure should not take these medicines.
The Anti-Adrenergic Agents or Adrenergic Antagonists
This
group of agents comprises:
-
the alpha-adrenergic antagonists;
-
the Beta-adrenergic antagonists;
-
the agents with mixed properties both alpha and Beta; and
-
the centrally acting adrenergic agents.
A.
The Alpha-Adrenergic Antagonists
The
most commonly used agents of this group are:
Doxazosin, Prazosin, Terazosin. They
are called selective alpha adrenergic antagonists.
Their mechanism of action is to block the postsynaptic alpha-receptors
producing arteriolar and venous vasodilation.
Side effects include syncope, orthostatic hypotension, dizziness,
headache and drowsiness. In most cases, side effects are self-limited and do not occur
with continued therapy.
B.
The Beta-Adrenergic Antagonists
The
most commonly used agents of the group are:
Atenolol, Betaxolol, Bisoprolol, Metoprolol, Nadolol, Propanolol,
Timodol, Acebutolol.
The
mechanism of action of beta-adrenergic antagonists is competitive inhibition of
the effects of catecholamines at beta-adrenergic receptors which decrease heart
rate and myocardial contractility and cardiac output.
They are part of medical regimens proved to decrease the incidence of
stroke and myocardial infarction. They
cause release of vasodilating prostaglandin decrease plasma volume and also may
have a CNS-mediated antihypertenseive effect.
Although
beta blockers are tolerated by the majority of patients as first-line treatment
for uncomplicated hypertension, higher doses of beta blockers are associated
with fatigue, nightmares, depression, reduced exercise tolerance, erectile
dysfunction and sexual impotance , atrioventicular block and in some patients,
bronchospasm. They may adversely affect lipid profiles and increase insulin
resistance. They are recommended as
first-line therapy following myocardial infarction because these drugs
consistently have been shown to improve survival rates in patients after acute
myocardial infarction. They are of particular advantage in patients with angina
pectoris and either atrial fibrillation or tachydcardia. They are not recommended for patients with brochospatic
disease.
The
agents with mixed properties, such as Labetolol and Carvedilol, have both alpha
and beta-adrenergic antagonist actions. Side
effects of Labetolol include hepato-cellular damage, postural hypotention,
tremors, hypotension, reflex tachycardia. Carvedilol
appears to have a similar side effect profile to other beta-adrenergic
antagonists.
The
centrally acting adrenergic agents, such as Clonidine, Methyldopa, Guanabenz,
Guanfacine, are potent antihypertensive agents. Their mechanism of action is to stimulate the presynaptic
alpha 2 adrenergic receptors in the CNS. This
stimulation leads to a decrease in peripheral sympathetic tone, which reduces
systemic vascular resistance. Also,
it causes a modest decrease in cardiac output and heart rate.
Renal blood flow is not compromised by centrally acting adrenergic
agents.
Side
effects of these centrally acting adrenergic agents include:
bradycardia, drowsiness, dry mouth, orthostatic hypotension, galatorrhea
and sexual dysfunction. It is not
recommended to stop these medicines abruptly because abrupt cessation may
precipitate an acute withdrawal syndrome of elevated blood pressure, tachycardia
and diaphoresis.
A.
The
Calcium Entry Blockers
The
calcium entry blockers are also called calcium channel antagonists.
They are effective agents in the treatment of Hypertension.
Calcium entry blockers lower blood pressure by reducing peripheral
vascular resistance. This is
accomplished by blocking the influx of calcium through voltage-sensitive calcium
channels located in smooth-mucle cell membranes.
Classes of calcium channel antagonists include:
a)
The diphenylalkylamines such as Verapramil and Benzothiazepines such as
Diltiazem, also called non dihydropyridines.
They have been shown to lower heart rate and decrease myocardial
contractibility and atrioventicular conduction.
These drugs have added benefits in patients with proteinuria due to
diabetic nephropathy and also can be used as an alternative for patients who are
unable to tolerate beta blockers after myocardial infarction.
The nondihydropiridines are associated with constipation and changes in
the cardiac conduction system or AV block in susceptible patients.
b)
The dihydropyridines such as Nifediprine, Amlodipine, Felodipine,
Nisoldipine, Isradipine, Nicardipine. These drugs function primarily as pure peripheral
vasodilators. The side effects
associated with the dihydropyridines include:
flushing, headache, dizziness, peripheral edema, which is not due to
sodium retention, but to unopposed arteriolar dilatation.
All calcium channel antagonists are
metabolized in the liver. Thus,
in
patients with cirrhosis, the dosing interval should be adjusted
accordingly
B.
The Angiotension - Converting Enzyme
(ACE) Inhibitors
The ACE inhibitors include: Benazepril,
Captopril, Enalapril, Fosinopril, Lisinopril, Moexipril, Quinapril, Ramipril,
Tandolapril. They are effective
antiphypertensive agents in a broad array of patients.
Their mechanism of action is to block the production of angiotension II,
a vasoconstrictor, by inhibiting ACE competitively, thereby leading to arterial
and venous vasodilatation and to natriuresis.
Ace inhibitors also increase level of vasodilatory bradykinins.
Some of these agents directly stimulate reduction of renal and
endothelial vasodilatory
Compared to other antihypertensive drugs, ace inhibitors have an
excellent side effect profile. They
may cause, however, a chronic, non-productive cough, angioedema and
hyperkalemia. Overall, these drugs
have demonstrated benefits among patients with hypertension who have had a
myocardial infarction, who have known cardiovascular disease or who have
diabetes. They are contraindicated
in patients with significant bilateral renal artery stenosis.
Angiotensine - Receptor Blockers (ARB)
They are fairly new antihyprtensive drugs
that are affective in diverse patient populations.
The five agents on the market in the United States are Losartan,
valsartan, Irbesartan, Candesartan and Eprosartan. The main mechanism of action of these drugs is to antagonize
the vasoconstrictive effects of angiotensin II at the AT1 receptor.
This action results in decreased peripheral vascular resistance.
In terms of their performance in lowering blood pressure, ARB's are
similar to ACE inhibitors and other classes of antihypertesnive drugs.
Some
side effects of these drugs occur rarely, but include angioedema, allergic
reaction, and rash. The cough seen with ACE inhibitors occurs much less
frequently with angiotensine - receptor blockers.
Renal hemodynamic alterations and hyperkalemia appear to be less than
that seen with ACE inhibitors.
Conclusion
Hypertension is a chronic disease that must be treated.
I urge anyone suffering from this condition not to be discouraged in
following their diet, performing regular exercises and taking medication under
their health care provider's guidance.
Joseph J. Nicolas, M.D.
104-105 Springfield Blvd.
Queens Village, NY 11429
Tel. (718) 776-6050
Fax (718) 776-6051
Sources:
Harrison Principles of Internal Medicine; The Washington Manual of
Medical Therapeutics; Journal of Clinical Hypertension; Archive of Internal
Medicine.
(The above is provided solely for informational purposes. It is in no way to be construed as a substitute for professional medical care.)