CARDIOVASCULAR 2 Flashcards
what is the function of the capillaries?
vessels where exchange between blood & tissue occurs- most numerous vessels in body- oxygen leaves the blood & carbon dioxide enters in capillaries
how do capillaries allow gas exchange?
very thinned walls, very low blood pressure, slow blood flow
what is the function of venules & veins?
return blood to heart- blood bressure in vessels is low, so they have thin walls
how do veins appears in radiographs?
during respiration, pressure in thorax changes- changes in pressure are transmitted to veins, their appearance on plain radiographs will be affected by stage of respiratory cycle
how do veins maintain blood flow?
blood pressure is insufficient to maintain blood flow- pressure changes in chest & compression of veins by contracting muscles help maintain flow
what is blood flow determined by?
by amount of blood in the vessels (cardiac output & blood volume), diameter of vessels, downstream resistance to blood flow
what is blood pressure?
amount of pressure required to keep blood flowing is determined by the resistance to blood flow in the vessels- how crowded blood is in artery
what is cardiac output & downstream resistance under control of?
of sympathetic nervous system
what happens when someone stands upright from a lying position?
gravity pulls blood towards the feet- less blood in vessels going to head as blood pressure falls + sympathetic activity increases causing cardiac output & vasoconstriction (restoring blood pressure)
what is long term blood pressure controlled by?
changing blood volume by changing amount of water in our body & therefore amount of blood in vessels
what happens when the body is dehydrated?
decreased renal perfusion causing renin release, which causes angiotensin release causing vasoconsctriction & no retention in kidney causing increased blood volume
what occurs following advanced hypertension?
heart failure
what is shock due to?
low blood pressure caused by hypocolaemia (haemorrhage), distributing (anaphylaxis, sepsis, spinal injury), cardiogenic (obstructive, tamponade, tension pneumothorax, pulmonary embolism)
what is activated to elevate BP?
Increased heart rate & peripheral vasoconstriction in arteries & veins (causing cold & pale skin)
what is the role of lymphatic system?
drains excessive interstitial fluid & protein from tissue
how does lymphatic drainage begin?
series of tiny capillaries, which form a mesh-like network throughout the tissue- fluid is lymph- pressure in lymphatic vessels is low & flow can be easily stopped
what is the role of lymph nodes?
nodes located throughout body, receiving lymph from particular regions- nodes are where metastases are removed from lymph
what is lymph flow under & affected by?
under low pressure- affected by muscle & respirtatory pumps, tone in ducts, pressure of interstitial fluid
what does increase of interstitial fluid cause?
swelling known as oedema
what are risk factors of atherosclerosis?
age, smoking, diabetes mellitus, hyperlipdaemia, hypertension
what are the pathogeneis of atherosclerosis?
fatty streaks appear in subendothelial space, formation of plaque, calcification of plaque (fibroatheomas) is common- lesions will cause clot or thrombosis
why do fatty streaks appear in subendothelial space?
LDLs penetrate endothelium, inflammation occurs, fats are oxidised & ingested by macrophages causing fatty streaks
what is myocardial infarcation?
death of myocardial cells due to blockage of artery
what is ischaemia?
restriction in blood supply to tissues, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive)- heart will switch to anaerobic energy production leading to pain (angia) with 75% occlusion
what is atherosclerosis?
buildup of cholesterole & fat creating plaque causing narrowing of blood vessels- if plaques are disrupted, clotting will occur, which will block the vessel- can cause ectopic pacemakers (cause premature heart beat)- anaerobic metabolism producing lactic acid which causes pain- causes strokes
what is a stroke?
buildup of plaque in the brain arteries- clot will develop, preventing blood flow= ISCHAEMIC STROKE- when blood
what is the diagnosis of myocardial infarction (heart attack)?
symptoms of ischaemia, ECG anormalities, loss of viable mycardium or regional wall abnormality
how can we investigate ischaemic disease?
via stress scintigraphy, stress enchocardiography, coronary arteriography, stress testing
what is stress scintigraphy?
radioactive isotopes are taken up by active heart muscle. Areas with less blood flow take up less isotope.
what is stress enchocardiography?
gives images of abnormal wall motion
what is coronary arteriography?
contrast media are injected to allow direct visualisation of the coronary arteries
what is stress testing?
pharmacological agents induce stress (adenosine & dobutamine), used with radionuclide imaging & echocardiography to show myocardial blood flow- mimics exercise
what is the role of adenosine?
dilates coronary vessels and increases flow rate in normal vessels & less of a response in stenotic vessels
what is the role of dobutamine?
a synthetic catecholaime which increases heart rate, blood pressure & myocardial contractility- acts like adrenaline
what does adrenaline do the body?
heart rate increases, stimulates sympathetic nervous system-
what is an aneurysm of blood vessels?
localised area of widening of vessel wall- due to atherosclerosis which destroys elastic tissue- aorta commonly affected- haemorhagic stoke
what is aneurysm associated with?
increased risk of vessel rupture which causes usually fatal haemorrhage
how do we investigate aneurysms?
plain radiographs, ultrasound, CT
how do aneurysms show in plain radiographs?
may appear as large soft tissue mass with calcification
how do aneurysms show in ultrasound?
shows enlargement of vessel
how do aneurysms show in CT?
shows location & extend, and some evidence of rupture
what is claudication?
peripheral arterial disease causes severe muscle pain on exercise
how is claudication diagnosed?
nonimaging & doppler ultrasongraphy & angiography
what is heart failure?
inability of heart to pump enough blood to meet requirement of the tissues
what is heart failure due to?
systolic dysfunction (not pumping), diastolic dysfunction (unable to relax and fill)
what are the main imaging features of heart failure?
changes in stroke volume & ejection fraction + structural changes in chambers (wider than 50% of transverse width of thorax)
what is oedema in the heart?
failing heart does not empty effectively, harder to fill chamber with blood & venous pressure goes up - as more pressure develops in ventricles
what happens when venous pressure goes up?
causes back pressure throughout the vascular system- high pressure in capillaries forces out into the tissue
what happens to the lung during oedema?
veins supplying the left side of heart are draining he lungs- congestion will develop in lungs
what happens to extremities during oedema?
veins supplying the right side of heart are draining the extremities- congestion will develop in abdomen, ankles
how do plain radiographs show oedema?
show enlargemnt of chambers & congestion in chest
how do echocardiogram show oedema?
shows chamber enlargement, ventricular function & valve function- used to measure ejection fraction
how does doppler ultrasound show oedema?
shows direction & acceleration of blood flow through the chambers- used to assess valcular regurgitation & stenosis
how does radionucleotide ventriculography show oedmea?
shows right & left ventricular ejection fraction
what is cardiomyopathies?
as a group, these conditions cause heart failure- the inability of heart to performs its normal function- affects the myocardium (effects the size of heart)- dilates
why may the heart be enlarged?
because of dilation & hypertrophy
what is dilation of the heart?
stretching of heart due to weakened muscles & excessive blood in heart- easy to see on plain radiographs
what may dilation be due to?
idiopathic, coronary artery disease (muscle is weak), valcular or hypertensive disease (heart is overloaded), infections, endocrime diseases, haematological disease (sickle cell anaemia), alcholism- wall of ventricle is thin & will affect function of valves
what does dilation cause?
fall in stroke volume (ejection function) causing systolic failure- valves fail to form an effective seal
what is hypertrophy?
increase in size & number of muscle cells in heart- occurs due to heart trying to pump against increased resistance- hard to see on plain radiographs- increased ventricle wall thickness
what is hypertrophy due to?
hypertension, outflow obstruction, endocrine disease
what occurs in hypertrophy?
size of chambers of ventricle & amount of blood it can hold is decreased which causes diatolic failure & ventricle walls are thick
what does hypertrophy develop in to?
outflow obstruction, diastolic failure, myocardial ischaemia
what are 2 main types of problems with valvular heart disease?
narrowing (stenosis) + incompetence (regurgitation)
what is stenosis?
anatomical obstruction of valves- increased resistance to outflow of blood because outlet has been narrowed
what happens to the myocardium during stenosis?
hypertrophies in response to increased work it is required to do- systolic dysfunction develops because myocardium is unable to maintain the high work load required to maintain function
what is imcompetence (regurgitation)?
caused by disease to the valve or its supporting structures due to infection (valves wont be able to close in normal position)
what occurs during incompetence (regurgitation)?
causes a large increase in end diastolic volume as blood flows backwards through incompetent valve- blood sits in heart (overstretches)- heart murmur
how do plain radiographs show valvular abnormalities?
hypertrophy of chambers which occur in response to pressure overload
how do echocardiographs show vulvular abnormalities?
used to examine valve motion, and chamber enlargement which occurs with volume overload
how do doppler ultrasounds show vulvular abnormalities?
used to meaure the pressure gradient across valve
what is atrial septal defect?
hole in wall seperating the 2 atria- congenital
what occurs due to atrial septal defect?
because of pressure gradient, blood passes through hole in atrial wall from left side to right side- increases amount of blood being ooumped from right ventricle & may lead to damage in lungs
what is ventricular septal defect?
systolic pressure in left ventricle much higher than in the right- blood flows from left ventricle to right- increase in pulmonary blood flow
what is pericardial effusion?
abnormal accumulation of fluid in pericardial sac due to irritation or injury to pericardium- can cause tamponade- any extra fluid will compress and collape the chambers
what is pericardial effusion caused by?
tumours, renal disease, heart attack, iatrogenic, infection, radiation
when does tamponade occur?
when effusion compresses the chamber of heart- chambers collape during diastole increasing the systemic venous pressure
what happens as a result of decreased filling of ventricles in tamponade?
systemic arterial pressure is low
what is tamponade due to?
metastatic tumours
how does a pericardial effusion appear on radiograph?
looks like a ball- not regular heart shape
