CVS Flow/Pressure Flashcards
Which side has the brachiocephalic trunk that splits into the common carotid and subclavian arteries, and which has the common carotid and subclavian straight off aorta?
L side has brachiocephalic trunk
What is pericardicentesis?
Aspiration of pericardial fluid e.g. blood or infective exudate that has caused a pericardial effusion
What can CO rise to in exercise?
25L/min
What is cardiac tamponade?
Fluid in the pericardial sac builds up and leads to compression of the heart - can lead to rocking rather than contraction and lead to cariogenic shock and death.
How much of blood is RBC and how much plasma?
2L RBC
3L plasma
5L altogether
Where does most of the blood lie in the cardiovascular system?
In the venous system
What are the three layers of artery and vein walls?
Tunica intima
Tunica media
Tunica adventitia
What does the tunica media of the aorta contain a lot of?
Elastin
Also 40 layers of SMCs
Why are AAAs most likely suprarenal?
Less elastin there
What is a capacitance vessel?
A vein - stretch passively and accommodate for increased blood (Store) and don’t recoil
Why do we need a CVS?
To get O2 nutrients and take waste from cells because diffusion isn’t possible over such large distances - transport system required
What two factors affect diffusion (gas exchange)
Area available for diffusion
Conc grad
What is rate of blood flow AKA? and how does this affect diffusion?
Perfusion rate
Higher perfusion rate more diffusion
What is the pericardial sac made of? What is the inner layer split into?
Outer fibrous layer
Inner serous layer - inner serous layer is made up of visceral layer and parietal (outer) layer with serous pericardial fluid in between
What are the roles of the fibrous layer vs serous layer of pericardial sac?
Fibrous layer anchors heart to mediastinum and is continuous with great vessels adventitia layer, prevents overfilling and protects heart against infection
Serous - lubrication to prevent friction during heart contractions
Why are coronary arteries prone to atherosclerosis?
Small vessels
Turbulent flow at junctions
Where is the phrenic nerve in relation to the pericardium?
Passes down between the lungs and the heart to meet the diaphragm. L phrenic nerve passes over pericardium of LV and pierces diaphragm. R phrenic nerve passes over RA
What is polycythaemia?
Rare condition normally defect in JAK2 gene that causes over production of RBCs (polycythaemia vera)
What is serum vs plasma?
Serum is plasma minus clotting factors so appears clear
Where are WBCs and platelets contained in a blood sample vial?
Buffy coat
What is peripheral resistance?
Resistance of the arteries to blood flow
Does a rise or fall in peripheral resistance lead to increased stroke volume?
Fall in TPR leads to increased SV
Which 3 characteristics of an artery/blood affect peripheral resistance?
- Change in length
- Change in diameter
- Change in blood viscosity
What is CRP? When is it used clinically?
It is an acute phase protein released in inflammation so used to measure inflammation
Acute phase proteins increase in concentration in the plasma during inflammation
Give a minor and major cause of increased blood viscosity
Minor - increase in acute phase proteins in inflammation
Major - Thrombocythaemia, Polycythaemia, multiple myeloma (plasma cell cancer)
What are metarterioles and what do they contain to help their function?
Arterioles that lead to a capillary bed - have SMC at the entrance to capillaries that act as pre capillary sphincters regulating blood flow through the capillary bed
Which blood disorder can cause dry gangrene and why?
Multiple myeloma due to increased protein Immunoglobulin that causes dry gangrene
Define viscosity
Intrinsic feature of a fluid relating to internal friction of adjacent fluid layers sliding past one another
What is the difference between velocity and flow?
Velocity is the distance of blood moved in time
Flow is the volume of blood moved in time
How would you work out flow from velocity and area of vessel?
flow = velocity x cross-sectional area of vessel
What is laminar flow? What is a flow characteristic of laminar flow?
Velocity of fluid is constant at any given point in the fluid
Flows in streamlines so layers of blood remain the same distance from the wall at any given time.
Parabolic flow is a characteristic of laminar flow where the fluid in the centra travels faster than that on the edges
What is turbulent flow?
Irregular flow in all directions in the vessel - blood continually mixing and changing direction
When can turbulent flow occur (5)?
- When blood flow becomes too great
- An obstruction
- A rough surface
- A corner
- Increased resistance to flow
By definition when does systole end?
When the aortic valve shuts
What is the dichrotic notch
Slight back flow in the aorta following aortic valve closure
When does blood enter the coronaries - systole or diastole
Diastole
How do you find the pulse pressure (equation)
Systolic - diastolic pressure
How do you find the MABP?
1/3 pulse pressure + diastolic pressure
Below which MABP is organ perfusion impaired?
70mmHg
Define the pulse?
Rhythmic shock wave of heart beat arriving slightly before the blood itself
What does the strength of the pulse depend on (2)
Force of LV contraction
Pulse pressure
What happens to the pulse pressure with a bounding pulse?
It widens
Does bradycardia widen or narrow the pulse pressure?
Widens - bounding
Does aortic insufficiency (regurgitation) lead to widened or narrowed pulse pressure?
Widened - as increased back flow during diastole reduced diastolic blood pressure so pulse pressure difference is more
Does pregnancy, hot baths exercise (low peripheral resistance) widen or narrow pulse pressure?
Widen
When taking blood pressure how must the cuff fit? Why?
Must go round at least 80% of arm
Too big - underestimates
Too small - overestimates
Where is blood pressure most accurate and why?
Nearest the heart so left arm as gravity has an effect on BP
Why does the heart need resistance and capacitance vessels?
Resistance - restricts blood flow to redirect to harder to perfuse areas of body
Capacitance - storage vessels e.g. to engorge and vary amount of blood pumped round body
Should L and R heart output over time be equal?
Yes has to be equal
Define systole diastole
Systole - contraction and ejection of blood
Diastole - relaxation and filling of blood
What is the pressure in the RA, RV, PA, LA, LV, Ao?
RA - 0-4 RV 25/4 PA 25/10 LA 8-10 LV 120/10 Ao 120/80
How long is a cardiac action potential?
200-400ms normally 280ms
How do APs travel from cell to cell in the heart?
Gap junctions
What determines whether a valve is open or closed?
Pressure
What are the roles of the papillary muscles/cordae tendinae?
Papillary muscles - contract on ventricular systole to prevent inversion (prolapse) of mitral and tricuspid valves
Chordae tendonae are tendon like structures that anchor the papillary muscles to the valves
Does the cardiac AP originate from the cardiac muscle or nerves?
AP for hear originates in the SAN not from nerves like skeletal muscle
Through the myocardial muscle does the AP travel endo-epicardium or epi-endocardium?
Endo - epicardium
From the wiggers diagram what is the A, C waves and X descent?
A wave - atrial systole
C wave - isovolumetric ventricular contraction increases the pressure in atrium - as mitral valves close
X descent - atrial pressure reduces as ventricles contract due to the atrial base being pulled downwards
What are the 7 stages of the wiggers diagram? Which are the stages where the heart sounds are heard?
1) Atrial contraction
2) Isovolumetric contraction - S1
3) Rapid ejection
4) Slowed ejection
5) Isovolumetric relaxation - S3
6) Rapid Filling
7) Slowed filling
What is the typical EDV (ml)?
120ml
How much ventricular filling is from atrial contraction?
10%
Which valves are open in stage 1 (atrial contraction)?
Mitral and tricuspid open, pulm and Ao closed
During which phase is the QRS complex?
2) Isovolumetric contraction
During which phase is the T wave?
Slowed ejection
What causes the A wave in the atrial pressure trace?
Atrial systole increases atrial pressure
Why does ventricular ejection rate slow (phase 4)?
Due to repolarisation of the ventricle leading to a decline in tension so the rate of ejection begins to fall
What is the difference between stenosis/regurg?
Stenosis - valves closed when should be open e.g. calcified
Regurg - valves closed when they should be open e.g. cusps not meeting in LV dilation
What is a cause of aortic valve stenosis?
1) Calcific - degenerative
2) Bicuspid aortic valve
3) Chronic rheumatic valve - commissural fusion
What kind of anaemia can occur from heart valve stenosis and why? What would it look like on microscopy?
Microangiopathy haemolytic anaemia due to shear stress and breaking of RBC when going through the valve
Would see schistocytes on histology
What is a cause of Ao valve regurgitation?
1) Rheumatic valve
2) Endocarditis
3) LV dilation - stretch - cusps don’t meet
What is Quinkes sign and head bobbing due to?
Head bobbing - bounding pulse due to aortic regurg - due to increased pulse pressure
Quinkes sign - blanching and flushing of the capillary nail bed due to ao regurg
What is myxomatous degeneration? What does this lead to in the heart?
It is pathological weakening of connective tissue that leads to mitral valve prolapse - mitral regurg
Name some causes of mitral regurg
1) Myxomatous degeneration
2) Damage to papillary muscle post MI
3) LHF - LV dilatation - cusps dont meet
4) Rheumatic fever
What is the main cause of mitral stenosis?
99% rheumatic fever
What does mitral stenosis lead to?
Dilated LA - AF and thrombus
Back pressure in pull veins - pulm hypertension
Exercise intolerance due to reduced CO and Pulm congestion
LVH
LHF
What can happen with the oesophagus with mitral stenosis and why?
Compression of the left recurrent laryngeal nerve and compression of the oesophagus can lead to dysphagia and hoarse voice
Why is the IJV pressure used to measure RA pressure not EJV?
- It is closer anatomically
- It doesn’t have valves like the EJV that prevent transmission of pressure
- It has a direct course to the RA whereas the EJV doesnt
What forms the Left, inferior and right borders of the heart?
L - RV mostly
R- RA
I - LV
How much should the heart occupy of the width of thorax in a chest x ray?
No more than 50%
What is the major symptom of an MI? (must describe type of symptom)
Central crushing chest pain
Why is an RCA occlusion most likely to cause rhythm disturbances?
RCA supplies SAN in most people
RCA supplies AVN in most people
What kind of murmur would a mitral valve regurg cause?
Pansystolic
What kind of murmur would a mitral valve stenosis cause?
Mid-diastolic low rumble
What kind of flow would occur through a stenotic mitral valve?
Turbulent
What would happen to the LA with a chronically stenosed mitral valve?
It would dilate because of the increased volume and pressure as it is harder for blood to flow through a stenosed valve
What is the effect of cardiac tamponade?
Compression of heart structures leading to reduced arterial blood pressure (haemodynamic compromise) - reduced cardiac output
In cardiac tamponade - why would cardiac output fall?
Because the fibrous layer of the pericardial sac cannot expand, so pressure on heart prevents it filling properly in diastole
What effect would a large VSD have on pulmonary circulation if left untreated?
Would cause vascular remodelling (increased SMCs) in pulm circulation leading to increased pulmonary vascular resistance —- in time would lead to reversal of flow in the VSD (Eisenmenger Syndrome)
What is preload?
Amount ventricles are stretched and filled
What is after load?
The load that the ventricles have to work against to eject blood - roughly equivalent to aortic pressure
What is TPR?
Resistance to blood flow offered by all systemic vasculature
What vessels in the body offer the greatest resistance?
Arterioles
What is Frank Starlings law? Why?
Increase in SV occurs with increased venous return
As increased stretch will cause increased contraction up to a point - until sarcomeres stretched too much to increase force of contraction - then contraction will reduce
What effect does dilation at the pre-capillary sphincters have on frank starlings law and on the autonomic NS?
- Would increase venous return so increase SV
- Would activated sympathetic NS so increase HR and contractility in response to increased venous return
Why when muscle fibres are stretched you get an increased force of contraction (2) ?
Increased length increases tension - increase force of contraction
Fibres are more Ca-sensitive when stretched - larger contraction
What effect will increased arterial pressure and increased TPR have on the heart workload and filling? What pathology can this lead to?
Increased work (increased afterload) and decreased filling due to increased TPR - leads to Hypertension
What is aortic impedance?
Basically afterload
What does ventricular emptying depend on (3)?
Pre load
After load
Force of contraction - sympathetic drive/circulating adrenaline
How does the arterial pressure, venous pressure, TPR change in increased metabolism and why?
Arterial pressure decreases
TPR decreases
Venous pressure increases
To increase blood flow to metabolising tissues
If both arterial and venous pressure decrease at the same time (e.g. on standing up) can you use intrinsic (frank starling) mechanisms? What can you use?
No -
Need both baroreceptor reflex and increased sympathetic drive to increase HR and increase TPR at the same time.
Why do you get postural hypotension?
If the baroreceptor reflex and sympathetic drive to increase TPR fail when you stand up
