HYPERTENSION-Etiology, Complications, Pathophysiology, Clinical Presentation and Diagnosis

Edited by, SRIRAM

Hypertension can be defined as a condition in which the blood pressure is elevated to a level likely to lead to adverse consequences. The world Health Organization has identified hypertension as a leading risk factor for death worldwide. The systolic/diastolic blood pressure of 140/90 mmHg is considered as the upper limit of normal range.

COMPLICATIONS:

Hypertension is the major risk factor for future development of cardiovascular disease. The complication includes stroke, myocardial infarction, heart failure, renal failure and dissecting aortic aneurysm.

EPIDEMIOLOGY:

Hypertension is a very common condition. It is estimated that approximately 25% of the adult population has hypertension, rising to above 50% of people over the age of 60 years old, although much of this remains undiagnosed. Hypertension is more common in black people of African or Caribbean family origin, who are also at a particular risk of stroke and renal failure.

ETIOLOGY:

In 90-95% of cases, there is no underlying medical illness to cause high Blood pressure. This is termed as essential Hypertension. The precise etiology of essential Hypertension is currently Unknown.

Genetic factors clearly play a part because the condition clusters in families, with hypertension being twice as common in subjects who have a hypertensive parents. The causes of secondary hypertension (5-10%) are renal diseases, endocrine diseases, vascular causes, renal artery stenosis and uses of some drugs such as steroids, NSAIDS, Erythropoietin, ciclosporin.

PATHOPHYSIOLOGY:

The mean blood pressure is the product of cardiac output and total peripheral resistance. In most cases, cardiac output is not increased, and high BP is due to result of increased total peripheral resistance caused by constriction of small arterioles.

Control of BP and homeostatic reflexes have evolved to provide blood pressure homeostasis. The changes in blood pressure are regulated by the baroreceptor reflex, whereas the renin-angiotensin aldosterone system is important for longer term blood pressure control.

CLINICAL PRESENTATION:

Hypertension is asymptomatic in most cases and is often identified during presentation with unrelated conditions or cardiovascular risk assessment. Severe cases may present with head ache, visual disturbances, evidence of target organ damage including stroke, ischemic heart disease, renal failure and retinopathy. Malignant or accelerated hypertension is an uncommon condition which shows elevated BP of  >220/120 mmHg associated with clinical manifestations of ongoing small vessel damage, papilledema, hemorrhages, exudates and renal damage. This condition is associated with hypertensive encephalopathy with severe clinical features include cerebral edema, visual loss, seizures and coma.

DIAGNOSIS:

Blood pressure should be measured using a validated manual or automated sphygmomanometer, which should be well maintained and regularly calibrated. Blood pressure should be initially measured in both arms and if there is a difference of more than 20 mmHg sustained after repeat measurement, the arm with highest value should be used for subsequent monitoring readings. It is important to palpate the radial and brachial pulse before measuring blood pressure to identify if there is a pulse irregularity. The blood pressure value of above 140/90 mmHg is considered as a diagnosis of hypertension.

TREATMENT THRESHOLDS:

Patients with stage 1 hypertension with no additional risk factors should be treated with lifestyle advices and support. Patients with stage 1 hypertension with additional risk factors such as CVD, Diabetes, renal diseases etc. should be treated with certain drug treatment (One drug) with lifestyle advices and support. Patients with stage 2 hypertension should be treated with specific drug regimens (combination drugs) and follow some lifestyle modifications. 

Patients with severe hypertension should be referred to specialist care with drug approach and lifestyle support.