High blood pressure makes your heart work harder and, over time, can damage blood vessels throughout your body. If the blood vessels in your kidneys are damaged, they may stop removing wastes and extra fluid from your body. The extra fluid in your blood vessels may then raise blood pressure even more. It's a dangerous cycle.

Heart

The main effect of hypertension on the heart is the development of hypertrophy and increased stiffness of the left ventricle (LV). Associated development of accelerated coronary atherosclerosis occurs resulting in higher incidence of myocardial infarction, sudden death, arrhythmias and cardiac failure. The risk of coronary heart disease increases almost 2 fold for a person with a diastolic pressure >91 to one with 105 mmHg. Myocardial ischemia is a common accompaniment due coronary artery disease and the decreased coronary blood flow per unit found in myocardial hypertrophy. Increased afterload and LV hypertrophy eventually results in systolic and diastolic heart failure.

The heart  involvement can be assessed with:

1) ECG: Myocardial ischemia is indicated by T-wave inversions.   Left ventricular hypertrophy (LVH) criteria:
 R in aVL >13 mm
 R voltage in L1+ S III >25 mm
 S v1 + R v5 or v6 >35 mm

2) Echocardiography: LV hypertrophy can be identified using M-Mode and 2 D imaging. Indications of myocardial ischemic states and systolic functions can be assessed by studying regional wall abnormalities and contractility indices like ejection fraction. Transmitral Doppler and newer technologies like Tissue Velocity Imaging can be used to diagnose diastolic abnormalities.

b) Central Nervous System

Hypertension is one of the leading causes of cerebrovascular disease. It has been associated with accelerated age related cognitive decline. The most dreaded  complication  is the occurrence of  strokes. The risk of a stroke increases almost 4 fold in a person with a diastolic pressure of 91 to one with 105 mmHg. Transient ischemic attacks (TIA) do occur due to extracranial atherosclerosis.

c) Renal

Hypertension induces microalbuminuria in the early stages. Later on nephrosclerosis sets in leading to renal failure with rise in blood urea and creatinine.

d) Aorta

The commonest abnormality of the aorta, associated with hypertension is abdominal  aneurysms. This can eventually lead on to rupture with fatal results.

e) Eye

The changes in the eye can be identified and assessed by fundus examination. Keith Wagner classification is the usual method of grading.

Grade I: Narrowing of arteries giving rise to copper wire or silver wire appearance.

Grade II: In addition to copper wire appearance,  arterio-venous nipping where the arteries cross the veins.

Grade III : In addition to above, superficial flame shaped and deep dot like haemorrhages and cotton wool exudates.

Grade IV : In addition to all the above, papilloedema.