cardiovascular pathology Flashcards
hypertension: explain the epidemiology, aetiology, pathology, pathophysiology, and treatment of hypertension
define hypertension
level of blood pressure above which investigation and treatment do more good than harm
epidemiology of hypertension
leading global cause of death affecting approx. 1 billion people; distribution is unimodal and any distincion between normal and abnormal is arbitrary
ambulatory blood pressure
threshold 5-10mmHg lower than “office” blood pressure; recorded automatically at regular intervals over 24hrs
effect of age on mean blood pressure and pulse pressure
rises with age; diastolic doesn’t so greater gap (pulse); majority of >60 expected to be hypertensive, almost everyone by >80
aetiology of primary hypertension: genetics
monogenic (rare - almost all affect renal Na+ excretion e.g. Liddle’s syndrome), complex polygenic (common)
aetiology of primary hypertension: environment
dietary salt (Na+), obesity, lack of exercise, alcohol, birthweight, pregnancy
primary hypertension % cases
idiopathic; 85-95% cases
causes of primary hypertension
kidneys (e.g. affect Na+ excretion), endocrine, high sympathetic nervous system activity
secondary hypertension % cases
known cause; 5-15% cases
causes of secondary hypertension
renal disease, Conn’s syndrome (secrete aldosterone), tumours secreting catecholamines, oral contraceptive pill, pregnancy-associated hypertension, rare genetic causes
calculate mean arterial pressure
cardiac output x total peripheral resistance
what is established hypertension associated with
increased TPR, decreased arterial compliance, normal cardiac output, normal blood volume, central shift volume
name 3 causes of elevated total peripheral resistance
active narrowing of arteries, structural narrowing of arteries, capillary loss
what happens in isolated systolic hypertension
larger arteries become stiff for idiopathic reasons, not increasing TPR; leads to SBP > 140, DBP <90; incidence increases with age
7 consequences of hypertension
congestive heart failure, stroke, heart failure, aneurysms, dementia, retinopathy, vascular disease, renal dysfunction
how does hypertension affect the heart
left ventricular hypertrophy, leading to cardiomegaly; leads to heart failure
how does hypertension affect large arteries
wall thickness increases to withstand increased wall stress
how does hypertension cause aneurysms
dilations of medium-large arteries leading to thrombosis and/or haemorrhage upon rupture
how does hypertension cause strokes
due to clotting and thrombosis, not rupture
how does hypertension affect eyes
damaged retinal capillaries (retinopathy) and reduced blood flow as narrowed arteries; increased leakage into surrounding tissue
how does hypertension affect microcirculation
reduces capillary density and elevates capillary pressure, causing damage and leaking
how does hypertension cause microalbuminuria
increases albumin loss in urine, due to reduced glomerular filtration rate
lifestyle treatment for hypertension
weight loss, exercise, healthy eating, less alcohol
drugs used to treat hypertension
ACE inhibitors, angiotensin receptor blockers, diuretics, B-blockers, Ca2+ channel blockers
aims of hypertension drug treatments
stop arteriolar vasoconstriction, ADH and aldosterone secretion, and tubular Na+ reabsorption; decrease total peripheral resistance and water retention
when are loop diuretics used
crisis to block water reabsorption
thiazide diuretic features
don’t work through diuresis, but slowly reduce total peripheral resistance
how do B-blockers work
beta 1 receptors in heart blocked so reduction in rate and force of contraction, reducing cardiac output; in kidneys stop renin secretion
how do Ca2+ channel inhibitors work
major effect in vascular smooth muscle to reduce Ca2+ influx, reducing cross bridge cycling; minor effect in reducing contractility and rate of conduction in heart
