Hypertension

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Hypertension, or high blood pressure, is a condition where the pressure of the blood in the arteries is elevated. It is one of the most common medical conditions and a major risk factor for heart disease and stroke.

The main types of hypertension are:

• Primary (essential) hypertension: Accounts for 95% of cases. The underlying cause is unknown but genetics, diet, obesity, lack of exercise, and stress play a role.
• Secondary hypertension: Due to an underlying condition such as kidney disease, adrenal gland dysfunction, thyroid issues, sleep apnea, etc. Treating the underlying cause may help lower blood pressure.

Blood pressure is measured as two numbers:

• Systolic pressure: The top number measures the pressure in arteries during a heartbeat. A normal systolic pressure is less than 120 millimeters of mercury (mm Hg).
• Diastolic pressure: The bottom number measures the pressure in arteries between heartbeats. A normal diastolic pressure is less than 80 mm Hg.

The stages of high blood pressure are:

• Elevated: Systolic between 120-129 or diastolic less than 80 mm Hg.
• Stage 1 hypertension: Systolic between 130-139 or diastolic between 80-89 mm Hg.
• Stage 2 hypertension: Systolic 140 mm Hg or higher or diastolic 90 mm Hg or higher.
• Hypertensive crisis: Systolic over 180 or diastolic over 120 with organ damage. Requires immediate treatment.

Most people with hypertension experience no symptoms, so regular blood pressure screening is important. Uncontrolled high blood pressure can lead to health issues like:

• Heart attack or stroke: Hypertension damages arteries and accelerates atherosclerosis.
• Heart failure: The heart has to work harder to pump blood through the body, leading to heart muscle thickening and eventual failure.
• Kidney disease: High blood pressure damages the small blood vessels in the kidneys, impairing their ability to filter waste. This can lead to kidney failure.
• Eye problems: Hypertension can damage blood vessels in the eyes, causing vision loss or even blindness.
• Dementia: Midlife high blood pressure may increase the risk of cognitive decline and dementia in older age.

Treatment for hypertension includes:

• Lifestyle changes: Losing excess weight, diet low in salt and fat, eating more potassium and calcium, reducing alcohol, quitting smoking, and exercise. These can help lower blood pressure.
• Medications: Such as diuretics, ACE inhibitors, angiotensin receptor blockers, beta blockers, calcium channel blockers, etc. Often multiple drugs are needed to control blood pressure.
• Treatment goals: A blood pressure less than 130/80 in most adults. Lower targets are needed for diabetics or kidney disease. Treatment aims to prevent complications and minimize side effects.
• Regular monitoring: Frequent blood pressure checks, as well as blood tests and screening for organ damage, are required to monitor hypertension treatment. Lifestyle and medication changes will be needed to keep blood pressure in the target range.

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Topic Highlights:-

• Hypertension or high blood pressure is a heterogeneous disorder.
• It is a leading risk factor for cardiovascular complications, stroke, and kidney failure.
• This visual presentation on hypertension focuses on its definition, measurement of blood pressure, pathophysiology, risk factors, complications, and treatment.
• The presentation also explains how hypertension can be controlled through lifestyle changes and medication.

Transcript:-
Hypertension is the medical term for high blood pressure. It is very common, occurring in about one in every four people. Hypertension has no symptoms. However, it can lead to organ damage and death if not treated.

The heart pumps blood full of dissolved oxygen to the body through the arteries. Arteries are not simply tubes, but have elastic walls made of a special type of muscle. The muscle can constrict or dilate, making the arteries narrower or wider. Damage to the inner wall of the artery causes fatty substances in the bloodstream to stick to it, forming plaques that make it stiffer and narrower in a process called atherosclerosis. The kidneys play a part in controlling blood pressure. They control the body’s total volume of blood and thus blood pressure by removing water from the bloodstream and excreting it in urine.

Renin-Angiotensin-Aldosterone System or RAAS plays an important role in maintaining normal blood pressure. It controls the blood volume and the blood pressure within the blood vessels and the heart functions. Renin is an enzyme primarily released by the juxtaglomerular cells of the kidneys, and also found in other tissues of the body. These enzymes are activated by the prostaglandins released by macula densa, which are closely packed kidney cells. Macula densa are sensitive to changes in sodium chloride (NaCl) levels in the fluid that pass through them. Renin is released in response to sympathetic stimulation, when a decrease in blood pressure within the renal arteries results in depletion of sodium levels in the distal tubules.

The released renin acts on angiotensinogen, a glycoprotein synthesized by the liver. Renin cleaves the angiotensinogen to form Angiotensin I. Angiotensin I is converted to Angiotensin II by angiotensin converting enzyme or ACE, found in the capillaries of the lungs. ACE also inactivates bradykinin and other vasoactive peptides. Other than ACE, enzymes like cathepsin G, elastase, tissue plasminogen activator, chymostatin-sensitive AT-II-generating enzyme, and chymase can also convert Angiotensin I to Angiotensin II.

Angiotensin II acts on the vascular smooth muscles, kidneys, adrenal cortex, and brain. It binds to its receptors and increases systemic vascular resistance and arterial pressure. Angiotensin II stimulates the release of aldosterone from adrenal cortex along with antidiuretic hormone and vasopressin from the posterior pituitary gland. Aldosterone causes re-absorption of water and sodium from the distal tubules, while vasopressin only acts in water retention. An over-active RAAS cascade leads to an increased retention of water and sodium, leading to hypertension.

Blood pressure is the pressure of the blood on the arteries’ inner walls. It is expressed as two numbers, for example ‘120 over 80 millimeters of mercury’, or ‘mmHg’. The first number is the systolic pressure, when the heart is squeezing blood out. The second number is the diastolic pressure, when the heart is resting between beats. Hypertension is defined as a pressure of 140 over 90 or higher. Because blood pressure varies during the day, a doctor will take at least three separate readings before diagnosing hypertension.

Blood pressure may be measured with a sphygmomanometer (often called sphygmometer). This is an inflatable cuff connected to an air pump and a pressure gauge. The cuff is wrapped around the upper arm and inflated to cut off the circulation, then deflated while the doctor or nurse listens to the heartbeat through a stethoscope. The pattern of heartbeats indicates the blood pressure reading. Electronic devices are available which can take readings from the arm or wrist. A patient’s blood pressure may increase because he/she becomes anxious in a clinical setting. It’s possible to get a more accurate reading by using a device at home. Ambulatory monitoring means measuring the blood pressure for 24 hours during a person’s normal routine and when they are sleeping. A small machine is worn that takes readings at regular intervals and records them. This gives an accurate average value for blood pressure.

Blood pressure tends to increase with age. Men are more at risk of hypertension than women. People with a family history of hypertension are at a higher risk. So are people from an Afro-Caribbean or a South Asian background. Other risk factors include obesity, alcohol abuse, consuming a high sodium diet, and high stress levels. For about nine out of ten people with hypertension, there is no identifiable single cause. This is called primary hypertension. For one in ten people, their hypertension has a cause that can be identified and possibly treated, such as kidney disease. This is called secondary hypertension.

Although symptom-less in itself, hypertension should be treated because it can damage the body’s organs. The high pressure inside arteries stresses and damages their linings and encourages the build-up of plaque. The presence of plaque increases the chance of blood clots and blocked arteries. This can affect the brain, the heart, the peripheral arteries, the kidneys and the eyes.

People with hypertension are more likely to have a stroke. In ischemic stroke, a blood clot forms in an artery supplying the brain. Part of the brain is deprived of oxygen and dies. Another kind of stroke is hemorrhagic stroke. An artery in the brain develops a weak spot in its wall, and high blood pressure makes it bulge and burst. Both kinds of stroke can lead to permanent disability or death. A rare complication of severe hypertension is hypertensive encephalopathy, when fluid leaks from the bloodstream into the brain and causes swelling. This can lead to headaches, confusion and seizures.

Hypertension makes the heart work harder, and over time this makes it pump less effectively. This can cause heart failure, where the heart can’t pump as much blood as the body needs. Hypertension also increases a person’s risk of angina and heart attack. If an artery supplying the heart gets partly blocked, the heart muscle doesn’t get enough blood and can’t work properly. This is angina, often felt as chest pain. In a heart attack, the blood supply is completely cut off, and the heart stops working unless blood flow can be restored.

Hypertension promotes the build-up of plaque. This reduces blood flow in peripheral arteries, such as those in the arms and legs. People may experience this as cramps during exercise, especially in the calf muscle. If blood flow in the peripheral arteries is completely cut off, gangrene will result. Hypertension also increases the risk of aneurysm. This is a weak spot on the artery wall that bulges and can rupture.

Hypertension damages the filters in the kidneys that remove waste from the bloodstream. Often kidney disease has no symptoms at first, but a doctor can use urine and blood tests to diagnose it. If it goes untreated, dialysis or a kidney transplant may be needed. Kidney disease can be both a cause and a result of hypertension.

Hypertension damages tiny blood vessels in the retina, at the back of the eye. This can lead to blurred vision and eventually blindness. The retina is the only part of the body where the effects of hypertension on the arteries can be viewed directly. A doctor can see how serious a person’s hypertension is by looking at the retina with an ophthalmoscope.

A doctor will usually advise someone with hypertension to make changes to their diet and lifestyle as a first step to control their blood pressure. Those with hypertension should lose weight if overweight, and eat a diet with reduced salt and fat. They should do some moderate exercise every day and reduce their alcohol consumption. It is also important to stop smoking. If these changes are not effective, drugs to reduce blood pressure may be prescribed.

The first choice of drug is often a diuretic. Diuretics work by helping the kidneys eliminate salt and water, thus reducing the blood volume and pressure. They also help the arteries to dilate.

Beta-blockers work by slowing the heartbeat and reducing the volume of blood pumped out of the heart every second. Some also block the kidneys’ release of renin.

ACE inhibitors decrease the effect of angiotensin-converting enzyme. ACE converts the body chemical angiotensin I into a form called angiotensin II, which constricts the arteries. It is also involved in the inactivation of bradykinin, a potent vasodilator. Inhibiting ACE thus makes the arteries dilate and reduces blood pressure.

Another group of drugs are called calcium channel blockers. Calcium channels are structures in cell walls that let calcium ions inside the muscle cells line the arteries. When calcium enters the cells, the arteries constrict. Calcium channel blockers work by blocking these channels. This makes the arteries dilate and reduce the blood pressure.

Renin helps to control the body’s sodium-potassium balance, fluid volume and blood pressure. Renin inhibitors lower blood pressure by blocking the renin-angiotensin system. Aliskiren reduces plasma renin activity (PRA) and thus optimizes renin-angiotensin-aldosterone system suppression or RAAS suppression. It is the first non-peptide, highly specific, orally active renin inhibitor to be indicated for the treatment of hypertension.

Alpha-blockers work by blocking alpha-receptors on the muscle cells lining the arteries. When certain body chemicals activate these receptors, the arteries constrict. When these receptors are blocked these chemicals cannot be activated. The arteries dilate and the blood pressure falls.

Angiotensin receptor blockers block the action of angiotensin II on artery muscle cells and stop it from constricting the arteries. This makes the arteries dilate, reducing blood pressure. The different groups of drugs described here may be used in combination with each other to control hypertension.