P12- Hypertension, thrombosis, embolism , Infarction Flashcards
what is systole?
left ventricular contraction
what is diastole?
left ventricular relaxation
what is blood pressure?
cardiac output x peripheral resistance
what contributes to cardiac output?
- heart rate
- contractility
- blood volume
Name peripheral resistance constrictors.
Angiotensin II , Catecholamines
Name peripheral resistance dilators.
Nitric oxide,
Prostaglandins
what is hypertension?
‘a disorder in which the level of sustained arterial pressure is higher than expected for the age, sex, and race of the individual’
what is hypertension synonymous with?
systemic arterial hypertension
what is high blood pressure ?
blood pressure of >140/90 mmHg consistently
Does hypertension affect ages specifically?
- NB age
- Children, adolescent, adult, 3rd decade
what is normal variation of hypertension?
Normal variation in individuals at different times of day- lowest levels during sleep
when does BP increase?
BP increases on standing up, on exercise and on exposure to cold and emotion
who is at risk of permanent hypertension -labile hypertension?
Individuals with a larger than normal pressure rise in response to these stimuli
How is hypertension monitored?
24 hr
what are the 2 types of classifications of hypertension?
- according to cause (Aetiological)
- according to consequences (Clinicopathological)
what are the 2 types of “according to cause” hypertension?
- primary
- secondary
what are the 2 types of “according to consequences” hypertension?
- benign
- malignant
what are 95% of cases?
no detectable cause- “primary” or “essential” hypertension
Give some causes of primary hypertension?
- Interplay of genetic and environmental factors
* Race, Stress, diet (salt, animal fats), alocohol intake, intrauterine life, exercise
what is secondary hypertension?
renal disease, endocrine disorders, aortic disease (Coarcta(on of the aorta ‐ congenital narrowing of segments of the aorta)
what are endocrine causes of hypertension?
- Adrenal gland hyperfunction / tumours
- Conn’s syndrome - excess Aldosterone
- Cushing’s syndrome - excess corticosteroid
- Phaeochromocytoma - excess noradrenaline
what is prognosis of patients with hypertension is related to?
height and rate of pressure rise
what is benign hypertension?
prognosis is measured in decades
what is malignant hypertension?
accelerated form fatal within 2 yrs if untreated
what can benign hypertension cause?
- Iscahemic Heart disease
- Heart Failure
- Stroke
- Acceleration of Renal Disease
- Malignant Hypertension
what are the symptoms of hypertension?
usually asymptomatic
How is bonging hypertension often detected ?
- Often detected in middle age during routine checkup
* BP rises slowly over many years
what does benign hypertension affect?
- Affects heart and arteries of all sizes
* Main target organs are heart, brain and kidneys
what is the most common complication of benign hypertension?
Ischaemic heart disease is most common complication (insufficient blood supply to the myocardium to meet functional demand)
what effect does benign hypertension have on the cardiovascular system?
- Increased pressure causes hypertrophy of the arteries and heart
- Resistance arteries have thicker walls and more narrow lumina
- Longstanding hypertension aggravates atherosclerosis and contributes to development and rupture of aneurysms and dissections
what effect does benign hypertension have on the heart?
- Left ventricular hypertrophy impairs diastolic function
- Increased muscle mass and interstitial fibrosis
- Poorer coronary artery perfusion
- If coronary atherosclerosis, increased oxygen demand of hypertrophied ventricle contributes to ischaemia, even at rest
- Leads to cardiac arrhythmias and myocardial infarct
what effect does benign hypertension have on the brain?
- Hypertension cause microaneurysms in arteries supplying basal ganglia, pons, cerebellum
- Rupture leads to hypertensive cerebral haemorrhages
- Also predisposes to cerebral infarction
what can occur in a subarachnoid haemorrhage?
rupture of berry aneurysm
what effect does benign hypertension have on the kidney?
Hypertension aggravates many renal diseases but only in severe cases does it cause renal failure
what are the values for benign hypertension?
- Every 10mmHg of diastolic pressure above 85 doubles risk of MI
- Every 8mmHg of diastolic pressure above 85 doubles risk of stroke
what is malignant hypertension?
- Serious life-threatening condition
- Diastolic pressure >130 mmHg
- Retinal changes of bilateral flame-shaped haemorrhages and /or papilloedema (swelling of optic nerve)
- Can develop from either benign primary or secondary hypertension (most common), or arise de-novo
- Usually younger people with hypertension 30-40yrs
- Needs urgent treatment to prevent death
what can malignant hypertensions cause?
- Causes cerebral oedema - seen as papilloedema (swelling of optic disc)
- Acute heart failure
- Stroke
- Acute renal failure
- Blood vessels show fibrinoid necrosis and endarteritis proliferans of their walls
what are the conclusions of hypertension?
- Hypertension is very common
- It is usually asymptomatic
- It may be due to an underlying disease
- It requires treatment to prevent complications and death
- It affects the physiology of several organs
what is blood clotting?
Solid mass of blood constituents EXTERNAL to the blood vessel
what is blood clotting a defence mechanisms against?
haemorrhage
what is blood clotting important in?
trauma and surgery /anaesthetics
what is a thrombus?
Solid mass of blood constituents formed WITHIN the blood vessel
where does thrombus occur?
Thrombosis occurs most commonly in veins but can occur in arteries
what is the risk of thrombosis increased by?
‘Virchows triad”
what is the Virchows triad?
- Injury to the VESSEL WALL
- Alterations in BLOOD FLOW
- Alterations in blood constituents that increase coagulability
what effect does Virchows triad have on vessels?
- loss of endothelial surface
- inflammation
what effect does Virchows triad have on flow?
- stasis
- turbulence
what effect does Virchows triad have on constituents?
- platelets
- coagulation proteins
- viscosity
what is involved in thrombus formation?
- platelets
- coagulation cascade
- fibrinolytic cascade
Describe the formation of a platelet rich thrombus?
- In rapidly flowing blood, vascular injury results in formation of platelet-rich thrombus which grows by gradual build up of activated platelets and fibrin (white/pale thrombus)
- Platelets stick to endothelium and become activated
- Coagulation cascade generates fibrin strands
- Thrombus occludes the vessel, blood flow slows and red blood cells can adhere to the surface of the thrombus (red thrombus)
- Further thrombosis both sides of blockage due to altered flow -propagation
what is the fate of thrombus?
- Can be lysed by anticlotting factors
- Larger thrombi on vessel wall can reorganise- infiltartion of macrophages and endothelial cells, recanalise, restore blood flow
- Some may become detached from vessel wall and move in blood flow to impact downstream (embolism)
what is an embolus?
Abnormal material carried in the blood which may block downstream vessels, depending on the size and nature of the material
what do large emboli result in?
infarction of the tissue in which the material impacts, eg brain‐stroke
Name the major types of embolism.
- THROMBOEMBOLISM
- Arterial side , heart to brain and kidney
- Venous side, pulmonary circulation
- ATHEROEMBOLISM (cholesterol crystals)
- FAT EMBOLISM
- AIR EMBOLISM
- TUMOUR EMBOLISM
- SEPTIC EMBOLISM
- AMNIOTIC FLUID
what happens in deep vein thrombosis?
- post op
- bed bound
- travel
- unilateral leg swelling
- oedema
- pain
what happens in pulmonary thromboembolism?
- sudden onset
- potentially life threatening
- haemoptysis
- breathlessness
- cardiovascular collapse and shock
- cardiac arrest
what is infarction?
Zonal necrosis due to sudden occlusion of blood supply:
- anatomy of blood supply is important
- atheroma
- embolism
what is necrosis due to?
lack of oxygen and nutrient
How is susceptibility to necrosis varied?
different tissues have different susceptibility
what can an infarction be?
fatal
what is a myocardial infarct?
Death of myocardial tissue caused by ischaemia (reduction or cessation of blood flow), such that oxygen delivery is not adequate to meet metabolic demands of cells
Is ischaemia reversible?
initially reversible - stable angina
what does persistent ischaemia lead to?
structural changes then death of myocytes
what are most infarcts due to?
thrombosis over atherosclerotic plaque
what do complications of myocardial infarct include?
- Arrhythmias
- Cardiogenic Shock
- Cardiac rupture
- Ventricular septal defects
- Heart Failure
what can re-perfusion result in?
injury to cells not previously affected
What is re-perfusion injuring due to?
Due to toxic oxygen species that are over-produced on restoration of blood supply
