Hypertension

When the blood pressure increases above normal range, then it is known as hypertension. Normal blood pressure is 120/80mmHg. Hypertension is a major risk factor for other cardiovascular diseases. The risk of hypertension is highest in those people who have a history of cardiovascular diseases such as myocardial infarction, transient ischemic attack or stroke.  Men are at higher risk for developing hypertension. Patients with diabetes or renal failure are also more susceptible to hypertension. It is a serious medical condition that increases the risk of damaging the other organs such as the brain, kidney etc.  There is no underlying medical condition in 90-95% of patients with hypertension.

Types

There are two main types of high blood pressure,

1. Primary hypertension

2. Secondary hypertension 

Primary hypertension

This type is also known as essential hypertension. There is no identifiable cause of primary hypertension. Primary hypertension accounts for about 90-95% of total hypertension cases. The Patho-genetic mechanisms of primary hypertension are multifactorial and poorly understood.

Secondary hypertension

The onset of secondary hypertension is abrupt. It causes higher blood pressure than primary hypertension. The causative agent of secondary hypertension is recognizable. It accounts for about 5-10% of total hypertension cases.

Risk factors

There are certain risk factors that increases the risk of development of hypertension,

• Ethnic-genetic risk (black people)
• Age
• Gender
• Hyperlipidemia (Cholesterol, TGs)
• Smoking
• Diabetes
• Overweight
• Inactivity (physical)
• Stress
• Insulin resistance
• Salt and alcohol intake
• Diet rich in saturated and trans fats
• Over consumption of tobacco
• Low fruits and vegetables intake

Symptoms

Most people with hypertension do not develop any sign and symptoms. Few people with hypertension or high blood pressure have symptoms of,

• Headache
• Visual disturbances
• Shortness of breath
• Nosebleeds
• Target organ damage

Causes

The blood pressure is the product of cardiac output and total peripheral resistance. In most patients with hypertension, cardiac output is not increased. But blood pressure increases due to total peripheral resistance. There are special pressure sensing receptors called baroreceptors that monitor minute to minutes variations in blood pressure. Renin–angiotensin–aldosterone system is important for long term control of blood pressure. This system increases preload as a result of increased water and sodium retention and stimulation of aldosterone secretion. This system can also increase afterload by causing constriction of vascular smooth muscles. The exact cause of essential or primary hypertension is still unknown. People with hypertensive parents are more susceptible to the development of high blood pressure. Genetic factors are responsible for about one-third of the blood pressure variation. Although there is no single gene responsible for high blood pressure, except in rare conditions such as polycystic kidney disease.

The causative agents responsible for the development of secondary hypertension are,

• Renal diseases
• Renal artery stenosis
• Fibro muscular hyperplasia
• Renal artery atheroma
• Coarctation of the aorta
• Hyperaldosteronism
• Conn's syndrome
• Hyperglucocorticoidism
• Cushing's syndrome
• Growth hormone excess
• Catecholamine excess (pheochromocytoma)
• Eclampsia
• Drugs such as sympathomimetic amines, oestrogens, contraceptive pills, ciclosporin,  erythropoietin, NSAIDs and steroids

Treatment

There is a stepwise approach to treat hypertension. In step 1, lifestyle modifications such as diet and exercise, limit alcohol and tobacco use and reduce stress factors are introduced to control blood pressure. In step 2, if lifestyle changes are not enough, then the drug therapy will be introduced to control the blood pressure. In step 3, if the previous steps don’t work, then dose or type of drug will be changed or another drug is added. In step 4, different medications are added until blood pressure is controlled.

The standard treatment plan of hypertension includes,

Diuretics

They are cheap and effective for the management of high blood pressure. They are more effective in older patients and resistant hypertension. There are two main types of diuretics, loop and thiazide. Drugs included are bendroflumethiazide, spironolactone and furosemide. 

Calcium channels blockers

They are well tolerated especially by elderly patients and those with ischemic heart disease or diabetes. They protect the heart tissue by inhibiting the entry of calcium into cardiac and smooth muscles. All calcium channels blockers are arteriolar vasodilators. They cause a decrease in smooth muscle tone and peripheral vascular resistance. There are two main types of calcium channel blockers, dihydropyridines and non dihydropyridines. Dihydropyridines include amlodipine, felodipine and nifedipine. Non dihydropyridine calcium channel blockers include diltiazem and verapamil.

Beta blockers

They decrease the myocardium oxygen demand by blocking β1receptors. As a result, a decrease occurs in heart rate, contractility, cardiac output and blood pressure. They can also reduce oxygen demand even during rest or exertion. Drugs included are atenolol, bisoprolol, metoprolol, pindolol and propranolol.

Angiotensin-converting enzyme (ACE) inhibitors

They are more effective in younger patients and those with diabetes or heart failure. Drugs include captopril, fosinopril, perindopril, lisinopril and ramipril.

Angiotensin II receptor blockers

They antagonize the effects of angiotensin II directly at the AT1 receptor. They are effective and recommended for use in patients who cannot tolerate ACE inhibitors due to severe cough. Losartan, valsartan, candesartan and irbesartan are angiotensin II receptor blockers.

Αlpha Blockers

They are used as second line agents for the treatment of hypertension. They are more expensive and less effective than other drugs. Drugs included are terazosin, prazosin and doxazosin.

Vasodilators

They are third line agents for the management of blood pressure. They are poorly tolerated and are used in severe hypertension and gestational hypertension. There are two main types of vasodilators, centrally and direct acting. Direct acting vasodilators are diazoxide, minoxidil and nitroprusside. Centrally acting vasodilators are methyldopa and moxonidine.

Complications

There are certain complications that can occur as a result of high blood pressure such as,

• Aneurysm
• Heart failure
• Heart attack
• stroke
• Metabolic syndrome
• Dementia
• Kidney diseases