CIRCULATORY SYSTEM DISORDERS
Any injury or disease that damages the heart, the blood or the blood vessels is considered as a disorder of the circulatory system. The most important circulatory diseases are hypertension and arteriosclerosis or atherosclerosis.

Hypertension is a medical condition in which the blood pressure is abnormally elevated. Hypertension, if persistent, leads to strokes, heart attacks, heart failure and arterial aneurysm. It also leads to chronic renal failure. The point at which blood pressure is considered as hypertension is somewhat arbitrary because blood pressure is a continuous distributed variable. Sustained blood pressure above 140 / 90 mm Hg is considered as hypertension. If the blood pressure is in between 120 / 80 mm Hg and 139 / 89 mm Hg, the condition is termed as prehypertension. Unlike hypertension, prehypertension is not a disease. Rather, it is a designation chosen to identify individuals who are a high risk of developing hypertension. In individuals with diabetes mellitus or renal diseases, blood pressure over 130 / 80 mm Hg is usually considered a risk factor.

Hypertension develops when the body's blood vessels narrow, causing the heart to pump harder than normal to push blood through the narrowed openings. If hypertension is not treated on time, it may often result in the enlargement of the heart and thickening of the heart muscle. Heart failure, brain stroke or renal impairment may result as eventually the heart needs more oxygen supply to function. Mild to moderate hypertension can be controlled by light exercise and weight loss. Light exercise is highly effective in reducing blood pressure. Even then most patients with moderate or severe hypertension end up requiring indefinite drug therapy to bring their blood pressure down to a harmless level. Stopping smoking does not reduce blood pressure but is useful in preventing other related diseases like stroke and heart attack, which are outcomes of hypertension. Mild hypertension is usually treated by diet, exercise and improved physical fitness. A diet rich in fruits and vegetables and fat-free dairy foods and low in fat and sodium lowers blood pressure in people with hypertension. Reducing salt intake decreases blood pressure in around one-third of the people. Regular mild exercise improves blood flow, and helps to lower blood pressure. Reduction of environmental stressors such as high sound levels can be an additional method of controlling hypertension.

There are many classes of medications for treating hypertension. Together, these are called antihypertensives. Reduction of the blood pressure by 5-6 mmHg can decrease the risk of stroke by 40%, of coronary heart disease by 15-20%, and reduces the likelihood of dementia, heart failure, and death from vascular disease.

Commonly used drugs include Beta blockers such as metoprolol (Lopressor®), atenolol, labetalol, carvedilol (Coreg®), ACE inhibitors such as lisinopril (Zestril®), quinapril, fosinopril (Monopril®), captopril, enalapril, ramipril (Altace®), Angiotensin receptor blockers (ARBs): eg, losartan (Cozaar®), valsartan (Diovan®), irbesartan (Avapro®), Calcium channel blockers such as amlodipine (Norvasc®), verapamil, Diuretics: eg, chlortalidone, hydrochlorothiazide (also called HCTZ), Combination products (which usually contain HCTZ and one other drug) and Alpha blockers such as terazosin, prazosin The aim of treatment should be blood pressure control (less than 140/90 mmHg for most patients, and lower in certain contexts such as diabetes or kidney disease). Each added drug may reduce the systolic blood pressure by 5-10 mmHg, so often multiple drugs are necessary to achieve blood pressure control.