What is blood pressure (BP) : it is the amount of pressure which the circulating blood exerts on the walls of the vessels while flowing through it.By blood pressure it always means arterial blood pressure unless indicated otherwise.Blood pressure is always measured in large arteries such as brachial artery in the arm (pressure in other vessels is always lower than brachial artery pressure).Blood pressure measurement provides two values (e.g.130/80 mm Hg),the first value (130) is called systolic blood pressure (when the heart contracts) and the latter value (80) is called diastolic blood pressure (when the heart relaxes).
Definition of Hypertension :
Hypertension is having blood pressure of more than 140 mm of Hg (systolic) and more than 90 mm Hg (diastolic).
ICD-9CM CODES :
401.1 Essential hypertension (HTN)
401.0-9 with 5th digit 1 Reno-vascular hypertension
405 Secondary hypertension
642 Hypertension complicating pregnancy
437.2 Hypertensive encephalopathy
There are about 1 billion individuals worldwide who would meet the criteria of hypertension.According to a study conducted by National Health and Nutrition Examination Survey (NHANES) from 2005-2008 about 68 million (31%) adult people in U.S. have hypertension out of which only only 46% have their hypertension under control.Peak incidence of hypertension are found in males and in elderly people (>65 years).Prevalence is higher among balks than whites.
The Joint National Committee on Prevention,Detection,Evaluation and Treatment of High Blood Pressure (JNC7) has classified hypertension into various categories :
- Normal blood pressure (adults) : <120 mm Hg systolic and <80 mm Hg diastolic.
- Pre-hypertension : systolic BP from 120 to 139 mm Hg and diastolic BP from 80 to 89 mm Hg.
- Stage 1 hypertension : systolic BP from 140 to 159 mm Hg and diastolic BP from 90 to 99 mm Hg.
- Stage 2 hypertension : systolic BP greater/equal to 160 mm Hg and diastolic BP greater/equal to 100 mm Hg.
Hypertension is either essential (idiopathic/primary) or secondary (following some disease in other body system/s).
Types of Hypertension : hypertension may present as one of the following
- Essential hypertension (85%) : is presence of sustained hypertension in the absence any correctable disease condition (renal,adrenal etc.).Previously it was known as benign hypertension (misnomer and outdated term).
- Isolated systolic hypertension : is presence of systolic blood pressure greater than/equal to 140 mm Hg and diastolic pressure less than 90 mm Hg,found in hyperthyroidism and conditions like leakage in a heart valve.
- Malignant hypertension (Hypertensive Emergency) : is presence of diastolic BP greater than 120 mm Hg along with exudative vasculopathy in the renal and retinal circulations.
- Refractory hypertension (Resistant hypertension) : is presence of BP greater than 140/90 mm Hg despite combined usage of two-three medicines (that includes a diuretic) for 3-4 months to the maximum dosage of the drugs.
- Pulmonary (arterial) hypertension : is increase in blood pressure
following some disease in lung vasculature (pulmonary artery,pulmonary
vein or pulmonary capillaries) leading to shortness of breath,dizziness
and syncope.When elevated blood pressure occurs exclusively due to lung
diseases,it is called primary pulmonary hypertension.The normal pulmonary artery pressure is about 14 mm Hg at rest,if it is greater than 25 mm Hg at rest or greater than 30 mm Hg on exertion then it is known as Pulmonary arterial hypertension. Recently the term idiopathic pulmonary hypertension
is being used when hypertension occurs due to increased pulmonary
artery pressure (Pulmonary arterial hypertension) without any apparent
- Morning hypertension : is a condition characterized by high blood pressure in the morning and controlled levels throughout the day. Heart attacks and stroke usually occur in the morning because of morning hypertension. Treatment for morning hypertension differs from treatments for other types of high blood pressure.The human body produces certain hormones in the early morning like cortisol,epinephrine,nor-epinephrine and growth hormone which cause elevation in blood pressure.Angiotensin Antagonist are useful in treatment.
- Idiopathic intracranial hypertension ( older names Benign intracranial hypertension (BIH) or Pseudotumour cerebri ) : is a neurological disorder that is characterized by increased intracranial pressure (pressure around the brain) in the absence of a tumour or other diseases. The main symptoms are headache, nausea, and vomiting, as well as pulsatile tinnitus (buzzing in the ears synchronous with the pulse), double vision and other visual symptoms.If untreated it may lead to swelling of the optic disc in the eye, which can progress to vision loss.The normal intracranial pressure is 7-15 mm Hg in an adult.Treatment depends upon the cause and usually treated with a diuretic.
- White coat hypertension : a group of patients present with high blood pressure readings on exposure to clinical settings but their blood pressure readings are otherwise normal.They are at low risk of developing cardiovascular diseases but may progress to develop sustained hypertension.Some believe seeing a picture of an iceberg before measuring blood pressure relieves these category of patients.
Causes of High blood pressure (secondary causes) :
- Kidney (5%) causes like glomerulonephritis,reflux nephropathy,diabetes,renal artery stenosis and other renal vascular pathology.
- Endocrine(<2%) causes like cushing's syndrome,primary aldosteronism (Conn's syndrome),phaeochromocytoma,congenital adrenal hyperplasia,use of oral contraceptive pills etc.
- Coarctation of Aorta (<0.2%).
- Immune disorders like polyarteritis nodosa.
- Drugs (5%) like steroids,amphetamines,NSAIDS,contraceptive pills.
- Neurogenic causes like increased intracranial pressure,acute spinal cord section.