hypertension - definitions, etiology and mechanisms
TRANSCRIPT
Hypertension –Definitions and Mechanisms
Dr. Md.Toufiqur Rahman MBBS, FCPS, MD, FACC, FESC, FRCPE, FSCAI,
FAPSC, FAPSIC, FAHA, FCCP, FRCPG
Associate Professor of CardiologyNational Institute of Cardiovascular Diseases,
Sher-e-Bangla Nagar, Dhaka-1207
Consultant, Medinova, Malibagh branchHonorary Consultant, Apollo Hospitals, Dhaka and
STS Life Care Centre, Dhanmondi [email protected]
Definition
Blood pressure (BP) in human populations has a normal distribution.
Accordingly,the definitions of "normal" BP and of various forms of hypertension are arbitrary, but
are needed for practical reasons in the assessment and treatment of patients.
Hypertension is defined as a systolic blood pressure (SBP) of 140 mm Hg or greater and/or a diastolic blood pressure (DBP) of 90 mm Hg or greater in persons not taking antihypertensive medication
Pre Hypertension
Those with a BP of 120 139 mm Hg systolic and/or 80 89 mm Hg diastolic areclassified as "prehypertensive," now known to increase the risk of any CV event bytwo to fourfold compared with a normal BP (<120/80 mm Hg).
Isolated systolic hypertension
Ageing is associated with a progressive increase in systolic BP, a reduction indiastolic BP, and widening of the pulse pressure. This is a reflection of a
progressive reduction in the compliance, or stiffening, of large conduit arteries.
"Isolated systolic hypertension" (ISH), the predominant form of hypertension in theelderly, is defined as a SBP of 140 mm Hg or greater in the presence of a DBP of 90mm Hg or lower.
Essential, primary, or idiopathic hypertension
"Essential, primary, or idiopathic hypertension," defined as high BP due neither tosecondary causes nor to a Mendelian (monogenetic) disorder, accounts for 90% of all cases.
The term "primary hypertension" is preferred, since “ essentialhypertension" represents an archaic misunderstanding of pathophysiology, namely
that hypertension is "essential" to maintain blood flow through severely narrowed resistance vessels.
Secondary hypertension
"Secondary hypertension" is high BP caused by an identifiable and potentiallycurable disorder.
"Refractory or resistant hypertension" is defined as a BP of≥140/90 mm Hg despite three drugs of different classes at maximum approved doses, given for at least 1 month.
"Spurious hypertension (pseudohypertension)" isartefactually elevated BP obtained by indirect cuff
measurement over a rigid, oftencalcified, brachial artery.
White coat hypertension
"White coat hypertension" describes patients whose BP is high (>140/90 mm Hg) in a n office or clinic setting, with a normal daytime ambulatory pressure (<135/85 mmHg).
This is a relatively benign condition with low risk of morbid events; however, the risk may increase with long term follow up (6 years or more).
Antihypertensivemedication in white coat hypertension patients may decrease clinic BP, but produces little or no change in ambulatory BP; thus, drug treatment may not confer substantial benefit.
Masked hypertension
"Masked hypertension" is the mirror image of white coat hypertension.
Here, theclinic BP is normal, but ambulatory or home measurements are high, andassociated with high risk. Although the prevalence of masked hypertension is low,
perhaps only 6% of the normotensive population, the absolute number in the United
States may approach 15 18 million.
Hypertensive crisis
"hypertensive crisis" encompasses both hypertensive urgency andhypertensive emergency.
"Hypertensive urgency" is defined as DBP >120 mm Hg inthe absence of acute or rapidly worsening target organ damage.
Hypertensive emergency
"Hypertensive emergency" is defined as acute or rapidly worsening target organdamage occurring in a hypertensive patient in association with elevated BP, but i rrespective of the specific BP level attained.
"Malignant hypertension" is ahypertensive emergency associated with papilledema, whereas "acceleratedhypertension" is a hypertensive emergency associated with retinal hemorrhages and exudates.
Summary
Hypertension is very common in nearly all populations, and is a major independent risk factor for CVD.
There is a graded relationship between BP and CV risk, with no apparent lower limit.
BP targets are <130/80 mm Hg for those with diabetes, kidney disease, and coronary artery disease.
The etiology of hypertension is multifactorial; monogenetic forms are rare.
SummaryKey elements in the etiology are activation of neurohormonal syste
ms (sympathetic nervous system, RAAS, ET); increased oxidative stress; altered
cellular ion transport of sodium, potassium, and calcium; and abnormalities of endothelial function and vascular
reactivity, large artery compliance, and small artery/ arteriolar resistance.
The main target organ effects and resultant CVD events are atherosclerotic vascular disease; MI, LV hypertrophy,
atrial fibrillation, heart failure; stroke, encephalopathy, dementia, and renal failure.
