What is blood pressure?

When blood flows through the arteries, it creates pressure on the artery walls. This is called blood pressure. This pressure can be changed based on your activity throughout the day.

What is normal blood pressure? 

When a patient's blood pressure is measured, there will be two numbers.
The first number is called "systolic blood pressure". Which is the pressure on the artery wall when the heart pumps blood through arteries (when heartbeats).
The second number is called "Diastolic blood pressure". Which is the pressure on the artery wall when the heart rests between beats (when the heart fills with blood).
An average person's normal systolic blood pressure (up) and diastolic blood pressure (down) should be less than 120/80 mmHg. 

What is hypertension? (High blood pressure)



An increase in blood pressure is called hypertension. Hypertension can involve either pulmonary circulation or systemic circulation, either one can develop high blood pressure. Usually, when a patient has hypertension, both systolic and diastolic pressures are increased but if a patient has isolated systolic or diastolic pressure increase that would also be called hypertension.

Cardiovascular diseases account for about one-half of all mortality in industrialized countries. The most common diseases among these are atherosclerosis and hypertension. 


Symptoms of hypertension

Typically, hypertension may not have symptoms or warning signs, because of this most people are unaware of hypertension. As a result of this, regular blood pressure measurement is necessary.
Some symptoms can be related to hypertension.
  • Morning headaches
  • Bleeding through nose
  • Abnormality in vision
  • Abnormality in heart rhythms
Chest pain, vomiting, fatigue, and anxiety can be the symptoms of severe hypertension.

Complications of hypertension

High blood pressure puts more strain not only on blood vessels but also on vital organs such as the heart, brain, kidney, and eyes.
Continues high blood pressure can increase the risk of following life-threatening conditions
  • Hypertensive heart disease (increased pressure load leads to left ventricular hypertrophy, grossly increased thickness of left ventricular and weight exceeds 500g)
  • Strokes
  • Hypertensive cerebral disease (intracerebral hemorrhage, is caused by the sudden rupture of damaged brain arteries within the cerebral hemisphere. Favorite sites are the basal ganglia, internal capsule, and cerebral cortex. Grossly a collection of blood with irregular margins. It can affect large portions of the brain, bleeding location and size will determine the clinical manifestation)
  • Aortic aneurysm
  • Hypertensive kidney disease (symmetrically atrophied bilateral kidneys. The surfaces present a diffusely, finely granular appearance. Histologically, Hyaline degeneration of afferent arterioles; the glomeruli show varying degrees of fibrosis, and hyalinization, with atrophy of the corresponding tubules, and in the interstitium, connective tissue proliferates and lymphocytes infiltrate)
  • Hypertensive retinal disease

Types of hypertension

Systemic hypertension is divided into two subtypes based on etiology
  • Primary (essential or idiopathic) 
  • Secondary (symptomatic) types 
Systemic hypertension is defined as more than 140/90 mmHg.

Primary hypertension (essential or idiopathic)

Most of the hypertension cases represent Primary Hypertension (90-95% cases). But the causes are still unknown. Even though the causes are unknown, there are some risk factors related to primary hypertension.

Risk factors of primary hypertension

Modifiable risk factors

  • Age (when a patient gets older, hypertension becomes more prevalent) 
  • Race (much higher risk in African-Americans and relatively lower risk in Asians)
  • Obesity
  • Stress
  • Physical inactivity
  • High salt intake (systemic blood pressure is a function of stroke volume and diastolic blood pressure is a function of total peripheral resistance). Sodium increases both blood volume and total peripheral resistance, so sodium affects systolic and diastolic blood pressure)
  • Heavy consumption of saturated fat and trans fat
  • Low consumption of fruits and vegetables (fiber) 
  • High intake of alcohol or coffee (caffeine-based drinks) 
  • Smoking

Nonmodifiable risk factors

A family history of hypertension is considered a non-modifiable factor of primary hypertension.

Secondary hypertension (symptomatic)

It only makes up about 5-10% of cases of High blood pressure. One classic cause among many is renal artery stenosis.


If a person has stenosis of the renal artery, there will be less blood flow to the glomerulus of the kidney. Then there will be the release of renin by the response of the juxtaglomerular apparatus(JGA). Due to the release of renin, angiotensinogen will be converted to angiotensin I. eventually angiotensin-converting enzyme (ACE) will convert the angiotensin I to angiotensin II. This angiotensin II will be responsible for High blood pressure.

Stenosis in renal artery
|
decrease blood flow to the glomerulus
|
Juxtaglomerular apparatus secretes renin
|
Angiotensinogen
|
Angiotensin I
|
Angiotensin II
|
Increase blood pressure

There are two pathways where angiotensin II increases blood pressure
  1. increase the release of aldosterone by the adrenal (aldosterone promotes distal convoluted tubule's reabsorption of sodium)
  2. contraction of arteriolar smooth muscle
Angiotensin II will be responsible for increasing blood pressure by increasing the release of aldosterone from the adrenal. Which will then grab more sodium from the distal convoluted tubule and eventually expand plasma volume. This is a very important physiologic relationship to be aware of.
If a patient got renal artery stenosis because of activating of Juxtaglomerular, there would be an increased level of renin. Hence, increased plasma renin can often be seen in secondary high blood pressure patients.
Atherosclerosis is the main reason for stenosis in elderly males. In young females, fibromuscular dysplasia is the major reason for stenosis.
Usually, stenosis occurs in one kidney, because of a decrease in blood flow the kidney becomes smaller (atrophy).

According to the pathological change, Hypertension can be divided into benign or malignant.

Benign hypertension

Benign hypertension is a mild increase in blood pressure. Sustained systolic blood pressure greater than 140 mmHg, or sustained diastolic blood pressure over 90 mmHg. Most hypertension cases are benign (95%). Mostly asymptomatic, vessels and organs are damaged slowly.

Malignant hypertension

Malignant hypertension is a severe increase in blood pressure. Systolic pressures over 200 mm Hg or diastolic pressures over 120 mm Hg. Associated with renal failure and retinal hemorrhages. Very rare cases represent malignant hypertension (less than 5%). 
Most cases occur in patients with previous benign hypertension, which may occur in previously fit individuals (de novo). Patients with malignant hypertension often can be seen with acute end-organ damage. Classically Acute renal failure, headache, and papilledema. Fibrinoid necrosis of the blood vessel wall can be developed in a patient who has malignant hypertension.

Features of benign and malignant hypertension


Medicines for hypertension

If you are diagnosed with hypertension, you may be told to take one or two of the following medicines by your doctor to control high blood pressure.
  • Angiotensin-2 receptor blockers
  • ACE inhibitors
  • Calcium channel blockers
  • Beta-blockers
  • Alpha-blockers
  • Diuretics