7. Cardiac Physiology - Beth Phillips Flashcards
Right side of the heart
- What kind of blood comes in?
- Through what?
- What valve is between the atrium and ventricle?
- What vessel does the blood come out from? Through which valve?
- Deoxygenated blood
- Superior and inferior vena cava
- Tricuspid valve
- Through the pulmonary valve into the pulmonary artery
Left side of the heart
- What kind of blood comes in?
- What valve is between the atrium and ventricle?
- What vessel does the blood come out from? Through which valve?
- Oxygenated blood
- Mitral valve AKA bicuspid valve
- Aortic valve into aorta
Coronary circulation
- What does the coronary circulation supply?
- Explain the 2 things the right coronary artery branches into
- Explain the 2 things the left coronary artery branches into
- Heart
- Marginal branch and posterior inter-ventricular branch
- Circumflex branch and anterior inter-ventricular branch
Explain the 5 steps of heart muscle conduction
SA node AV node AV bundle (bundle of His) Right and left bundle branches Purkinje fibres
Cardiac muscle
- What type of muscle is it?
- What is contraction dependent on?
- What is a sarcomere?
- What is a myofibril?
- Explain a H zone, an I band and an A band
- What are thick filaments mainly made of? What are thin filaments mainly made of?
- Striated
- Calcium and ATP
- Smallest functional unit of any striated muscle
- Sarcomeres end to end
- H zone = part in middle (only thick band)
I band = thin filaments connecting on adjoins sarcomeres (no thick)
A band = whole thick and the thin that it overlaps with - Thick = myosin
Thin = actin
Cardiac myocytes
- Explain cardiac myocytes in 3 ways. Explain the syncytium aspect.
- Define intercalated discs
- Define gap junctions
- Define connexons
- Small cell, single nucleus, mitochondria take up 30-40% of cell
Work as functional syncytium but are not a structural syncytium - Electrical boundaries between cells with leaky gap junctions
- Electrical pores made of proteins
- Charged aqueous pores
Action potentials
- What is the rating membrane potential of all cells?
- Membrane permeability to which ions causes depolarisation?
- Membrane permeability to which ions causes repolarisation?
- What is the part of an action potential called where the line is going from polarised to reaching the threshold?
- Electronegative
- Sodium and calcium
- Potassium
- Pacemaker potential
Autonomic control
- Higher brain centres and sensory receptors send input to where?
- From there, the output to the heart goes via the SNS or the PNS. What does the SNS release and on which receptor? What does this lead to an increase in?
- What does the PNS release and on which receptor? What does this lead to a decrease in?
- Cardiovascular centre
- Nor-adrenaline on beta1-adrenoreceptors
Leading to an increase in HR, spontaneous depolarisation in SA and AV node, contractility and stroke volume - Acetylcholine on muscarinic receptors
Leading to a decrease in HR and spontaneous depolarisation in SA and AV node
What do the following do to the slope of the pacemaker potential:
- Sympathetic tone
- Parasympathetic tone
- Increases slope
2. Decreases slope
- Define ECG
- What kind of recordings are these?
- What is a galvanometer?
- What is a dipole?
- Recording of electrical activity of the heart which represents mechanical activity
- Extracellular recordings
- Detects, measures and determines direction of small electrical currents
- Difference in charge between one bit of the membrane and another
What kind of deflection would happen in the following cases?
- Depolarisation moving towards unipolar electrode (or towards + pole of bipolar lead)?
- Depolarisation moving away from unipolar electrode (or away from + pole of bipolar lead)?
- What is the case for repolarisation?
- Positive upward deflection
- Negative downward deflection
- Opposite for repolarisation
Explain the places where the 10 electrodes are placed, naming each electrode (point out which one is the neutral electrode)
R wrist / L wrist R ankle (neutral) / L ankle V1 = 4ICS R sternum V2 = 4ICS L sternum V3 = between V2 and V4 V4 = 5ICS L mid-clavicle V5 = 5ICS L axilla start V6 = 5ICS L mid-axilla
Which leads are bipolar? Which leads are unipolar?
Bipolar leads = leads 1, 2 and 3
Unipolar leads = leads aVR, aVL, aVF
Einthoven’s triangle - limb electrodes
- What is each corner?
- What is lead 1? What is lead 2? What is lead 3?
- What are the labels inside the triangle? How do they work?
- Where are the other 6 leads from? What are they called?
- Right arm / left arm / left leg
- Lead 1 = LA to RA
Lead 2= LL to RA
Lead 3 = LL to LA - aVR (right arm) / aVL (left arm) / aVF (left foot)
They compare their own spot with the average of the other 2
Eg. aVF compares LL to average of LA and RA - 6 chest leads (V1-V6)
ECG and heart regions Describe what part of the heart each of these sections represents: V5, V6 aVL 1 aVF 2 3 V2, V3, V4 V1
V5, V6 = left side of the heart - lateral leads aVL = upper left side of heart 1 = second high lateral lead aVF = inferior wall of heart 2 = second inferior lead 3 = third inferior lead V2, V3, V4 = anterior face of heart V1 = septal leads (with V2)
ECG recording
- What 2 things do you need to be careful of when placing electrodes?
- What 3 things should the patient be doing?
- What else do you need to keep in mind when using an ECG machine?
- Accurate placing (no crossed cables)
Contact with skin (may require shaving) - Patient relaxed (pain free), not moving and not talking
- Electrical interference
P wave
- What does it show?
- Which atrial activation starts first?
- Size of muscle? Amplitude?
- Atrial depolarisation
- Right
- Small hence small
PR interval
- What does it show?
- It is measured from the start of the P wave up until when?
- Normal duration?
- Conduction through AV node, Bundle of His and Purkinje fibres
- First deflection of QRS complex
- 0.12-0.20 secs
QRS complex
- What does it show?
- Large muscle mass of what? Results in what?
- Normal duration?
- Ventricular depolarisation
- Left ventricle
QRS predominantly representing LV - Less than 120 ms
Q wave
- What is it?
- Normal depth? Normal duration?
- Any initial negative deflection
- Less than 2mm
Less than 40 ms
ST segment
- What does it show?
- What is the muscles status at this point?
- Usual depth?
- End of ventricular depolarisation to beginning of repolarisation
- Muscle is depolarised and contracting
- Level or +- 1mm from baseline
QT interval
1. What does this show?
- Total time for depolarisation and repolarisation of the ventricles
T and U wave
- What does the T wave show?
- Rarely exceeds what depth?
- What is the U wave? Do many ECGs have a discernible U wave?
- Ventricular repolarisation
- 10mm
- Small deflection after T wave
No
What 2 types of cells does the heart contain and which one is 99% of them? What does each one do?
Contractile cells (99%) Mechanical work
Autorhythmic cells
Initiate and conduct action potentials for contractile cells
- Where is the SA node?
- Where is the AV node?
- Explain the travel of the Bundle of His (AV bundle)
- Where are the Purkinje fibres?
- Which valves are open during ventricular diastole?
- Which valves are open during ventricular systole?
- Right atrial wall near opening of superior vena cava
- Base of right atrium, near septum
- AV node to IV septum-divides into right and left bundle branches- curve around ventricle walls back towards atria
- Bundle of His and spread throughout ventricular myocardium
- Bicuspid and tricuspid
- Pulmonary and aortic
Wall of ventricle
- What are the 2 sections either side of the mid-wall called? Which direction do the fibres run in and towards what?
- Which cells are activated slightly quicker?
- Subendocardial section
Fibres run away from mid-wall towards subendocardial surface
Subepicardial section
Fibres run away from mid-wall towards epicardium surface
- Endo cells
3 distinct layers of heart: epicardium, myocardium and endocardium
- Describe the epicardium
- What is the myocardium composed of?
- Describe the endocardium. What type of tissue is it made of?
- Thin external membrane that covers the heart
- Cardiac muscle
- Thin inner layer made of endothelium
Phases of the cardiac cycle
- Because there are 2 sides of the heart, what does that make the cardiac cycle?
- Which side has more pressure?
- Define stroke volume
- Define ejection fraction
- A tandem
- Left side
- Stroke volume = amount of blood ejected by the left ventricle in 1 contraction
- Ejection fraction = fraction of outbound blood pumped from the heart with each heartbeat
Phases of the cardiac cycle
1. Name the 3 phases in order
Name the 7 sub phases within it
1. Diastole Atrial systole 2. Systole Isovolumetric contraction Rapid ejection Reduced ejection 3. Diastole Isovolumetric relaxation Rapid ventricular filling Reduced ventricular filling
Phases of the cardiac cycle
- Which stage is the first heart sound heard? Which valves are closing? This also causes what?
- Which stage is the second heart sound heard? Which valves are closing
1. Stage 2 = isovolumetric contraction AV valves Associated blood turbulence 2. Stage 5 = isovolumetric relaxation Semi lunar valves
Common valvular problems
- What is mitral stenosis? This leads to a back up of blood where? What else does this mean?
- What is aortic stenosis? What does this lead to?
- What 2 things can cause mitral regurgitation?
- Incomplete opening of mitral valve = back up of blood in left atrium and inadequate ventricle filling
- Incomplete opening of aortic valve = inadequate ventricle emptying
- Mitral valve closes but can’t fully prevent back flow of blood during contraction
Or
Mitral valve doesn’t close properly
- Define arterial BP
- What are the 2 reasons for having this pressurised system?
- Aortic pressure rises to a peak pressure of what during LV contraction?
- Aortic pressure falls to a minimum pressure of what during LV relaxation?
- What is the small blip in the pressure profile called when the aortic valve closes?
- Hydrostatic pressure generated on arterial wall by hearts pumping action
- Blood can flow around body and also blood can flow against gravity
- 120 mmHg
- 80 mmHg
- Dichroic notch
Mean arterial BP
- What is the equation for pulse pressure?
- What is the equation for mean arterial blood pressure?
- Define MABP
- PP = systolic BP - diastolic BP
- MABP = diastolic BP + 1/3 pulse pressure
- Average pressure exerted by the blood on the walls of the major arteries
Efferent blood vessels
- Describe the wall of the artery
- Describe the wall of the arteriole
- Describe the wall of the capillary
- Muscular and elastic
- Muscular
- Thin walled
- Define cardiac output
- What does TPR stand for?
- What is the equation for CO?
- How can you work out MABP using Ohm’s law?
- Volume of blood ejected from the heart per minute
- Total peripheral resistance
- CO= HR x SV
- MABP = TPR x (HR x SV)
- What 4 things affect arterial BP?
- What 3 things increase MABP?
- What 3 things decrease MABP?
- In what 2 ways does the body maintain the correct BP, and what is their time?
- Circulatory volume/ force of ventricular contraction/ elasticity of arteries/ peripheral resistance
- increased HR/ increased fluid retention by kidneys/ polycythaemia
- Dilation of blood vessels/ reduced force of ventricular contraction/ dehydration
- Baroreceptor reflex (immediate)
Endocrine system (over days/weeks)
Baroreceptors
- What kind of receptors are they?
- Which 2 places are they found?
- Where do they send the information to?
- They increase MABP by increasing what 2 things?
- How do they increase TPR?
- Pressure receptors
- Wall of arch of aorta / carotid sinus
- Central nervous system
- HR and SV
- Constrict blood vessels
What 3 things does angiotensin 2 do to increaseTPR, MABP, CO and circulating blood volume?
- Constricts blood vessels
- Stimulates and promotes ADH release
- Stimulates aldosterone release
What is the 8 step systematic method of reading an ECG?
- Any electrical activity?
- What is the HR?
- QRS rhythm: regular/irregular?
- QRS duration: normal/prolonged?
- Atrial activity present?
- How is atrial activity related to ventricular activity?
- ST segment: raised/ depressed
- Any Q waves?
What are 6 common symptoms associated with arrhythmia presentation?
Palpitations Dizziness Chest pain Dispnea Syncope Sudden cardiac events
What are the 3 principle methods for arrhythmia formation?
- Disordered impulse formation
- Disordered impulse conduction
- Combined disorder
Sinus bradycardia
- Describe it
- Rate?
- Patient?
- Name 2 causes
(RR intervals constant and regular/ all wave forms present/ one P wave to each QRS complex)
- Normal sinus rhythm and conduction, but slowed down
- Less than 60bpm (not less than 40bpm)
- Asymptomatic
- Beta blockers or calcium channel blockers
Sinus tachycardia
- Describe it
- Rate?
- Patient?
- Name 3 causes
(RR intervals constant and regular/ all wave forms present/ one P wave to each QRS complex)
- Normal sinus rhythm and conduction, faster
- More than 100bpm (not more than 130)
- Asymptomatic
- Stress/ exercise/ hypovolaemia
Sinus arrythmia
- What kind of sinus rhythm?
- How much does the PP interval vary by?
- 2 causes?
- If respiratory: what will happen to the PP interval with inspiration?
- Regularly irregular
- More than 10%
- Naturally occurring/heart damage
- Shortens
Atrial fibrillation
- What kind of rhythm?
- Absence of what 2 things?
- AV conduction?
- 2 causes?
- Often associated with which 3 symptoms?
- Irregularly irregular
- No P waves or isolectric baseline
- Variable AV conduction
- COPD/CHF
- Palpitations/ fainting/ chest pain
1st degree heart block
- What is wrong in this case?
- Patient?
- What should you do if metabolic disturbance is suspected?
- Increases risk of what 3 things?
- PR interval longer than 0.20 seconds
- Usually asymptomatic
- Check U&Es
- AF/ pacemaker use and all-cause mortality
Second degree heart block
- Mobitz type 1: what is wrong here? What happens next? Where does it occur?
- Mobitz type 2: what is wrong here? PR interval? Where does it occur? What can it lead to? What is common treatment?
- PR interval progressively longer until 1 P wave is blocked
Cycle begins again after blocked P wave
Occurs in AV node
2. Some P waves not conducted to the ventricles PR interval constant Occurs below Bundle of His Leads to 3rd degree heart block Common treatment = external pacing
Third degree heart block
- What is wrong here?
- HR?
- PR interval?
- P waves and QRS complex?
- What does it require?
- Common treatment?
- All impulses from atria are blocked by the AV node
- Slow HR
- PR interval = random
- No relationship between P wave and QRS complex
- Requires subsidiary pacemakers in ventricles to act
- Common treatment = external pacing
Ectopics
- What are they?
- What are 2 main types and what do they mean?
- Premature impulses in cardiac cycle
- Atrial ectopics (premature atrial contractions)
Ventricular ectopics (premature ventricular contractions)
Starlings forces
- What are they also known as?
- What do they determine?
- Passive forces
2. How much fluid leaves plasma and enters interstitial fluid (and vice versa)
Diffusion
- Definition?
- Happens through what 3 things?
- Describe oxygen and nutrient movement through diffusion
- Describe carbon dioxide movement through diffusion
- Movement of ions/molecules/particles down a concentration gradient
- Intracellular clefts/ fenestrations/ endothelial cells
- From blood to interstitial fluid to body cells
- From body cells to interstitial fluid to blood
Transcytosis
- Definition
- What 2 ways are used to enter and leave the endothelial cells?
- What kind of molecules is transcytosis important for?
- Transport of large, insoluble molecules by pinocytotic vesicles
- Endocytosis and exocytosis
- Large lipid-insoluble molecules
Define bulk flow
Passive movement of a large number of ions, molecules or particles in a fluid moving in the same direction down a pressure gradient
Normal Starlings forces
- What 2 acronyms are inside the vessel?
- What 2 acronyms are outside the vessel?
- How often is lymph formed? Where does the lymphatic system drain back into?
- Which 2 forces promote fluid filtration?
- Which 2 forces promote fluid reabsorption?
- BCOP + CHP
- ICOP + IHP
- Lymph formed daily
Drains back into blood - CHP + ICOP
- BCOP + IHP
Starlings forces
- What does BCOP stand for?
- What does CHP stand for?
- What does ICOP stand for?
- What does IHP stand for?
- Which 2 forces promote fluid filtration?
- Which 2 forces promote reabsorption?
- Blood colloidal osmotic pressure
- Capillary hydrostatic pressure
- Interstitial colloidal osmotic pressure
- Interstitial hydrostatic pressure
- CHP + ICOP
- BCOP + IHP
Net filtration pressure
- Definition
- Equation?
- What 2 places do you calculate it at?
- Balance of starlings forces
- NFP= fluid filtration - reabsorption
- Arterial end and venous end
- What also effects NFP?
- What is it numerically?
- How do we add it to the NFP equation?
- What does this give us?
- Changes in capillary permeability
- K(small)f = capillary filtration coefficient
- NFP = (filtration - reabsorption) X Kf
- True net filtration pressure
What are the 3 types of capillaries? Describe them briefly
- Continuous: endothelial cell membranes formed from a continuous tube
- Fenestrated: with fenestrations/pores
- Sinusoids: wider and more winding, usually with larger fenestrations
Oedema
- Define oedema
- Which 3 places is it most commonly seen?
- What is it called in the pleural cavity?
- What is it called in the peritoneal cavity?
- Give 2 characteristics of localised oedema
- Give 2 characteristics of diffuse oedema
- When net fluid movement exceeds lymphatic drainage
- Subcutaneous tissue, lungs and brain
- Hydrothorax
- Ascites
- Influenced by gravity/ dependent
- Severe/ non-dependent
Etiology of extracellular oedema
Name the 2 possible reasons for extracellular oedema and give 2 causes for each
- Lymphatic failure
Obstruction by cancer / surgery - Abnormal fluid leakage across capillary wall
Infection / tissue injury
Etiology of Intracellular oedema
- What is the cause? What does this lead to?
- What will this then stimulate?
- Name 4 consequences as a result of this
- Cellular pathological consequence
Leads to cellular damage - Stimulates the inflammatory response
- Impaired function of plasma membrane ATP dependent sodium pump
Increased sodium and calcium influx and increased potassium efflux
Increased water influx
Cellular swelling and membrane blebs
What 2 things can prevent oedema formation?
- Pressure changes in the interstitial fluid
2. Reactive lymph flow
Promoting oedema formation in ECF
- Increase in which 3 things of starlings forces?
- decrease in which 3 things of starlings forces?
- Kf / CHP / ICOP (the filtration aspect)
2. Lymphatic drainage / BCOP / IHP (the reabsorption aspect)
Causes of oedema - increased hydrostatic pressure
Give 3 methods and 1 cause for each one
- Excessive renal retention of salt and water
(Excessive salt intake) - Impaired venous return
(Venous obstruction) - Arteriolar dilation
(Heat)
Causes of oedema - decreased plasma proteins
Give 3 methods of this and give a cause for each one
- Loss of proteins in the urine
(Nephrotic syndrome) - Loss of protein from denuded skin
(Burns) - Failure to produce proteins
(Liver disease)
Causes of oedema - lymphatic blockage
Give 3 ways this can happen
- Inflammatory infections
- Neoplastic masses
- Treatments
Causes of oedema - increased capillary permeability
Name 3 ways in which this can happen
Immune reactions
Toxins
Bacterial infections
Left hand side heart failure
- If the LHS is weakened, it is difficult to pump blood to which circulation?
- There is back up behind which part of the heart?
- Where does fluid accumulate because of this?
- Which pressure rises?
- What does this cause?
- Systemic circulation
- Left ventricle
- Lungs
- Pulmonary vascular pressure
- Pulmonary oedema
Right hand side heart failure
- If the RHS is weakened, pumping of blood to what is weakened?
- What kind of congestion does this cause?
- What does this result in? What is this also known as?
- To the lungs
- Venous congestion
- Peripheral oedema AKA pitting oedema