Let’s learn about hypertension.
Hypertension or high blood pressure, is a sustained arterial blood pressure higher than
normal.
Blood pressure is measured in millimeters of mercury (Hg) and consists of both systolic
and diastolic pressures.
The systolic pressure represents the pressure in the arterial system during contraction
of the heart’s ventricles which is called systole, while the diastolic pressure is the
pressure in the arteries during relaxation of the heart called diastole.
Blood pressure is represented by both numbers with the systolic number on top and the diastolic
number on the bottom.
Hypertension is characterized by an arterial pressure of 140 mm Hg or higher.
According to the American Heart Association: In adults, normal blood pressure is less than
120/80 Elevated blood pressure is a systolic pressure
of 120-129 and a diastolic pressure of less than 80.
Stage 1 hypertension is a systolic pressure of 130-139 or a diastolic pressure of 80-89.
Stage 2 hypertension is a systolic pressure of 140 or greater or a diastolic pressure
of 90 or higher.
A hypertensive crisis is a systolic pressure greater than 180 and/or a diastolic pressure
greater than 120.
Hypertension can be categorized as primary or secondary with the majority of hypertension
cases being primary.
There is no direct cause for primary hypertension but there are a series of lifestyle, genetic,
and environmental factors that contribute to it.
These include the sympathetic nervous system, hormones, inflammation, and changes to the
inner walls of arteries.
The sympathetic nervous system (SNS) is part of the autonomic nervous system and is commonly
known as the fight or flight system.
SNS activity causes an increase in heart rate and vasoconstriction, both of which increase
blood pressure.
Other effects of SNS activity include increased renin, renal sodium retention, and insulin
resistance.
The Renin-Angiotensin-Aldosterone System (RAAS) can also contribute to hypertension.
Renin is a hormone secreted by the kidney.
Activation of the RAAS results in the secretion of aldosterone from the adrenal gland which
promotes sodium retention, systemic vasoconstriction, and insulin resistance.
High sodium intake contributes to hypertension through fluid retention.
Increases in fluid volume promote an increase in blood volume and blood pressure.
Dysfunction of the natriuretic hormones which work to reduce sodium concentration can also
increase blood pressure through sodium retention.
Chronic inflammation can contribute to hypertension by way of damage to the inner lining of arteries
(endothelium).
Chronic inflammation can lead to a decrease in Inflammatory chemicals that promote vasodilation
which then facilitates vasoconstriction.
Obesity contributes to hypertension by increasing vascularity and peripheral resistance along
with insulin resistance and increased sympathetic nervous system activity.
Insulin resistance contributes to hypertension through decreased release of vasodilators
in arterial endothelium, sodium retention, and overactivity of the SNS and RAAS.
Here we see normal channels on the left responding to insulin to allow the transport of glucose
into the cell while the channels on the right are not responding to insulin.
Secondary hypertension results from an underlying disease process such as adrenal gland tumors
and renal diseases.
Medications such as antihistamines and corticosteroids can also increase blood pressure.
Malignant hypertension is characterized by a diastolic pressure greater than 140 mm Hg.
Causes include reactions to drugs (cocaine and amphetamines), adrenal tumors and medication
reactions.
Malignant hypertension causes movement of fluid out of capillaries into the interstitial
spaces and can cause cerebral edema and organ failure.
Treatments for hypertension include lifestyle modifications such as decreasing weight, stopping
smoking, and exercise.
Medications for hypertension include diuretics to reduce fluid volume, Angtiotensin Converting
Enzyme inhibitors (ACE inhibitors), Angiotensin II antagonists, Beta blockers which decrease
heart rate and vasoconstriction, and calcium channel blockers which help to decrease the
heart’s force of contraction and promote vasodilation of arteries.