Week 1 Flashcards
Define syncope
Total loss of consciousness due to cerebral hypoperfusion characterised by rapid onset short duration and spontaneous complete recovery
What are the 4 types of shock?
Hypovolaemic
Cardiogenic
Obstructive
Distributive
What are the types of hypovolaemic shock?
Haemorrhagic
Non-haemorrhagic
Up to what % of blood volume loss can the body compensate for?
> 30%
When the CO is decreased what response will be elicited by the baroceptor reflex?
Increase in HR
What volume of pulse is seen in hypovolaemic shock?
Low
What impact will the baroceptor response have on SVR in hypovolaemic shock?
Increased SVR (Cool peripheries)
What hormonal responses may be seen in hypovolaemic shock?
Increased vasopressin
Increased renin-angiotensin-aldosterone system action
What occurs in cardiogenic shock?
Sudden severe impairment of cardiac function leading to sustained hypotension
What occurs in obstructive shock?
Physical obstruction to circulation either into or out of the heart
What can cause obstructive shock?
Cardiac tamponade
Tension pneumothorax
PE
Severe aortic stenosis
How can a tension pneumothorax lead to shock?
Increased intrathoracic pressure, decreasing venous return.
What causes distributive shock?
Excessive vasodilation and abnormal distribution of blood flow
What are the 2 types of distributive shock?
Neurogenic
Vasoactive e.g. septic, anaphylactic
How could a SCI lead to shock?
Loss of sympathetic tone to vessels and heart, causes massive venous and arterial vasodilation.
What type of shock leads to bradycardia?
Neurogenic
Describe vasoactive shock.
Release of vasoactive mediators, leading to massive venous and arterial vasodilation and increased capillary permeability.
What type of shock doesn’t indicate volume replacement?
Cardiogenic
What is the tunica intima composed of?
Endothelial cells (simple squamous) supported by a basal lamina and thin layer of connective tissue
What is the tunica media made up of?
Mostly smooth muscle
What is the tunica adventitia made up of?
Supporting connective tissue
What separate the tunica layers?
Internal and external elastic membrane
What can help differentiate elastic arteries?
Many sheets of elastic fibre in the tunica media
Describe the histology of arterioles.
Only 1 or 2 layers of smooth muscle in the tunica media and almost no adventitia
Narrower lumen than arteries
What replaces smooth muscle in meta arterioles?
Pericytes
Where are capillaries absent?
Epithelial cells
Epidermis of skin, hair and nails
Cornea
Hyaline cartilage
Where are continuous capillaries found?
Muscle, connective tissue, lung, skin and nerves
Where are fenestrated capillaries found?
Mucosa of the gut
Endocrine glands
Glomeruli of the kidney
Where are discontinuous capillaries found?
Liver
Spleen
Bone marrow
What are precapillary sphincters?
Smooth muscle at the beginning of the capillary to help control flow by constricting the lumen
What differentiates postcapillary venules and venules?
Intermittent smooth muscle
Describe the histology of veins.
Relatively thin but continuous tunica media typically with a few layers of smooth muscle. Large veins have a thick adventitia which incorporates bundles of longitudinally orientated smooth muscle
Order these from innermost to outermost:
Myocardium
Endocardium
Epicardium
Endocardium
Myocardium
Epicardium
What is endocardium composed of?
Endothelium
Basal lamina
Thin layer of collagen fibres
Layer of denser connective tissue
What is the subendocardium?
Found in some areas
Loose connective tissue containing small blood vessels and nerves and Purkinje fibres
Describe the myocardium.
Bundles and layers of contractile cardiac muscle
Individual muscle fibres are surrounded by delicate collagenous connective tissue with a rich network of capillaries
What is the function of intercalated discs?
Pass across fibres at irregular intervals to assist in action potential conduction
Describe the epicardium.
Single layer of flattened epithelium called mesothelium
Basal lamina
Fibroelastic connective tissue
Some places adipose tissue
What are the two divisions of the pericardium?
Fibrous
Serous
What is fibrous pericardium?
Sac of tough fibrocollagenous connective tissue
What are the 2 divisions of the serous pericardium and where is each found?
Parietal - Lines the inner surface of the fibrous pericardium
Visceral - Covers the surface of the heart
Describe the fibrous skeleton of the heart
Thick band of connective tissue
Around the valves , between the atria and between the ventricles
Supports the valves and provides attachment for the cardiac muscle fibres
What are the 3 types of cardiac muscle cell?
Contractive
Pacemaker
Conducting
What are the 3 categories of syncope?
Reflex syncope
Orthostatic hypotension
Cardiac syncope
What are the 3 types of reflex syncope?
Vasovagal reflex syncope
Situational reflex syncope
Carotid sinus reflex syncope
What is reflex syncope?
All types where neural reflexes modify HR and/or vascular tone hence predisposing to a fall in MAP sufficient enough to affect cerebral perfusion
What can trigger vasovagal reflex syncope?
Emotional distress
Orthostatic stress
What occurs in situational reflex syncope?
Faint during or immediately after a specific trigger e.g. cough, swallowing etc
In what types of reflex syncope may cardiac permanent pacing be indicated?
May be in situation reflex syncope
Likely in carotid sinus reflex syncope
What can trigger carotid sinus reflex syncope?
Mechanical manipulation of the neck, shaving, tight collar etc
What indicates postural hypotension?
Drop within 3 minutes of standing from lying in systolic BP of at least 20 diastolic (with or without symptoms) or at least diastolic (with symptoms)
What may cause cardiac syncope?
Arrythmias
Acute MI
Structural cardiac disease
Other e.g. PE, aortic dissection
What may be suggestive of cardiac syncope?
Syncope during excretion or when supine
Presence of structural cardiac abnormality or coronary heart disease
Family hx of sudden death at a young age
Sudden onset palpitations immediately followed by syncope
ECG findings
Name a vitamin supplement recommended for all adults
Vitamin D
What vitamin deficiency are vegans at high risk of?
B12
What impact can plant sterols and stanols have?
Reduction in cholesterol
Where is the heart found?
Middle mediastinum
Where do the phrenic nerves run?
Anterior to the root of the lung
What is cardiac tamponade?
Pericardial cavity fills with blood placing pressure on the heart
What is the most external layer of the pericardium?
Fibrous pericardium
What is the transverse pericardial sinus?
Space within the pericardial cavity posterosuperiorly
Lies posterior to the ascending aorta and pulmonary trunk
What are the borders of the heart?
Right and left lateral
Inferior
Superior
Where is the apex beat best heard
5th intercostal space in the mid clavicular line
What may happen to the apex beat in cardiac enlargement?
Can shift towards the left
What are the auricles of the heart?
Extensions of the atria that optimise filling and increase capacity
What groove is found between the right and left ventricles?
Anterior intraventricular groove
What is the coronary sinus?
Short venous channel which all cardiac veins drain to
What groove is found posteriorly between the left and right atria?
Interatrial groove
What groove is found posteriorly between the right and left ventricles?
Posterior interventricular groove
What are the first branches of the aorta?
Right and left coronary arteries
What are the branches of the right coronary artery?
Right marginal artery
Posterior interventricular artery
What are the branches of the left coronary artery?
Left anterior descending artery
Left marginal artery
Lateral branch
Circumflex artery
What are the 2 parts of the heart’s septum?
Interatrial
Interventricular
What 3 openings are found in the right atria?
Superior vena cava
Inferior vena cava
Coronary sinus
What is the oval fossa?
Thumbprint type depression associated with the interarterial septum
What is the crista terminalis?
Division between the smooth area of the right atria and the tribecular carna
What are the cusps of the tricuspid valve?
Anterior
Posterior
Septal
What are the 2 semilunar valves?
Pulmonary
Aortic
What arises from the sinuses of the aortic valve?
Coronary arteries
Where are papillary muscles found?
Cardiac wall attaching to tendinous cords extending from the leaflets
Where is the area of auscultation for the mitral valve?
5th left intercostal space midclavicular line
Where is the area of auscultation for the tricuspid valve?
4th left intercostal space, sternal edge
Where is the area of auscultation for the pulmonary valve?
2nd left intercostal space sternal edge
Where is the area of auscultation for the aortic valve?
2nd right intercostal space sternal edge
What is an ECG lead?
The imaginary line the between 2 or more electrode
What happens on an ECG when depolarisation moves toward the recording electrode?
Upward deflection
What causes a downward deflection on an ECG?
Depolarisation moves away from recording electrode
What are the chest leads on an ECG?
V1 to V6
What are the 6 limb leads on an ECG?
I, II, III, aVR, aVL, aVF
Where are the limb electrodes placed?
Left LL
L UL
R UL
R LL (earthed)
What does the P wave represent?
Atrial depolarisation
What does the QRS complex represent?
Ventricular depolarisation
What does the T wave represent?
Ventricular repolarisation
Which segment on an ECG is isoelectric?
ST segment
Which lead is used for the rhythm strip?
Lead II
What is the standardised speed of ECG paper?
25mm/sec
One large square 0.2 secs
One small block 0.04 secs
What is the normal duration of the QRS complex?
0.1 secs or less
Where is the PR interval and what does is represent?
Start of P wave to start of QRS complex
Time for SA node impulse to reach the ventricles
What is the normal length of the PR interval?
0.12 - 0.2 secs
What does the QT interval represent?
Primarily time for ventricular depolarisation and repolarisation
What is a normal time for QT interval?
Needs to be corrected for HR
Normally 0.36 to 0.44 secs at rate of 60bpm
Where are lead I, II and III?
Lead I between R and L arm
Lead II between R arm and L leg
Lead III between L arm and L leg
What leads give a horizontal view of the heart?
V1 to V6
How does coronary venous blood drain?
Via the coronary sinus into the right atrium
Is the oxygen extraction higher or lower in the coronary circulation comparted to systemic?
Higher ~75% compared to ~25%
What is the nervous supply of coronary arterioles?
Sympathetic vasoconstrictor
What is functional sympatholysis?
Sympathetic stimulation of the heart results in coronary vasodilation despite vasoconstrictor affect
What receptors are abundant in the coronary arteries?
Beta 2
What can overcome sympathetic vasoconstrictor tone in skeletal muscle?
Metabolic hyperaemia
What circulation meets the metabolic needs of airways?
Systemic bronchial circulation
What is the typical pulmonary artery BP?
Systolic - 20 - 25
Diastolic - 6 - 12
Is pulmonary capillary pressure lower or higher than systemic?
Lower
What effect does hypoxia have on pulmonary arterioles?
Vasoconstriction, the opposite to that on systemic arterioles
What drives the heartbeat in sinus rhythm?
The SA node
What causes the pacemaker potential?
Funny current
What are HCN channels?
Hyperpolaristation-activated Cyclic Nucleotide gated channels
If HCN channels are blocked what would happen to the HR?
Slowed
What is the neurotransmitter of the sympathetic ANS?
Noradrenaline
What is the impact of the sympathetic nervous system on the pacemaker potential and AV nodal delay?
Increases the slope of pacemaker potential
Decreases AV nodal delay
What impact does the sympathetic ANS have on HR?
Increases HR
How does the sympathetic ANS impact the Frank-Starling curve?
Shifts to the left
What is the neurotransmitter of the parasympathetic ANS?
Acetylcholine
What is the impact of the parasympathetic nervous system on the pacemaker potential and AV nodal delay?
Decreases slope of pacemaker potential
Increases AV nodal delay
What nerve does the parasympathetic ANS act on the heart through?
Vagus
What impact does the parasympathetic system have on HR?
Decreases HR
What does atropine do at acetylcholine receptors?
Competitive inhibitor increasing HR
Give 2 examples of cardioselective beta blockers?
Atenolol
Bisoprolol
What effect do beta blockers have on cardiac action?
Block sympathetic action
Reduce force of contraction
Slow HR
Reduce myocardial oxygen consumption
What are the phases of the contractile myocyte action potential?
Phase 0: Fast Na influx
Phase 1: Closure of Na channels and transient K efflux
Phase 2: Mainly Ca influx (L-type Ca channels)
Phase 3: Closure of Ca channels and K efflux
Phase 4: Resting membrane potential
Why is calcium required for cross bridge formation in cardiac myocytes?
To expose the myosin binding site through confirmational change of the tropomyposin complex
What is stroke volume?
Volume of blood ejected by each ventricle per heart bead
End diastolic volume - End systolic volume
What is cardiac output?
Volume of blood pumped by each ventricle per minute
SV x HR
What is normal resting cardiac output?
~5 litres per minute
What extrinsic factors control vascular smooth muscle?
Nervous
Hormonal
What type of nerve fibres supply vascular smooth muscle?
Sympathetic
What receptors does noradrenaline work on in vascular smooth muscle?
Alpha
What impact does adrenaline have on beta 2 receptors and alpha receptors?
Beta 2 - Vasodilation
Alpha - Vasoconstriction
What intrinsic factors can cause relaxation of arteriolar smooth muscles?
Decreased local PO2
Increased local PCO2
Increased local H+
Increases extracellular K+
Adenosine release from ATP
What effect does nitric oxide have on blood vessels?
Vasodilator
Give 2 examples of nitrates?
GTN
Isosorbide mononitrate
What hormonal systems regulate extracellular fluid volume?
RAAS
Natriuretic Peptides
Antidiuretic Hormone
Where is aldosterone released from?
Adrenal cortex
What is the rate limiting step in the RAAS?
Renin release from the kidneys
What is the overall effect of the RAAS?
Increase in Na and water reabsorption in the kidneys
Increased plasma volume
How do natriuretic peptides decrease BP?
Cause excretion of salt and water in the kidneys reducing blood volume
Act as a vasodilator
What are the 2 main types of natriuretic peptides released by the heart?
Atrial
Brain-Type
What conversion do ACEi inhibit?
Angiotensin I to angiotensin II
What do ARBs block?
Action of angiotensin II at ATI receptors
What is the cardiac plexus?
Intertwining of different nerve types - Sympathetic fibres, parasympathetic fibres (vagus) and visceral afferent fibres
When might statins be prescribed?
Hypercholesterolemia
Diabetes
Angina/MI
CVA/TIA
High risk of MI and CVA
What are the possible side effects of statins?
Myalgia/ myopathy
Rhabdomyolysis, renal failure
Other than statins what medication groups can be prescribed for lowering cholesterol?
Fibrates
PCSK 9 inhibitors
Name 2 PCSK 9 inhibitors
Alirocumab
Evolocumab
How do PCSK9 inhibitors work?
Inhibit the binding of PCSK9 to LDL receptor increasing the number of LDL receptors available to clear LDL
What is inclisiran?
Gene silencing drug, silencing the PCSK9 gene
What do thiazide diuretics do?
Block Na reabsorption in the kidneys
Give an example of a thiazide diuretic and an example of a loop diuretic.
Thiazide - Bendrofluazide
Loop diuretic - Furosemide
Give some side effects of diuretics?
Hypokalemia - Fatigue and arrythmias
Hyperglycemia in diabetics
Increased uric acid - May lead to gout
Give some examples of cardioselective beta blockers.
Atenolol
Bisoprolol
Give some examples of non-selective beta blockers.
Propanolol
Carvedilol
What are the 2 types of calcium antagonist?
Dihydropyridines and rate limiting
Give an example of a dihyropyridine.
Amlodipine
What side effect can be caused by calcium channel blockers?
Oedema
Give 2 examples of rate limiting calcium antagonists.
Verapamil
Diltiazem
What other medication should be avoided with rate limiting calcium antagonists?
Beta blockers
What do ACEi block?
Angiotensin I being converted to angiotensin II
Give an example of an ACEi.
Lisinopril
Give some potential side effects of ACEi.
Cough
Renal dysfunction
Andioneurotic oedema
What should be prescribed for HTN in pregnant women?
Beta blockers
What do ARBs block?
Angiotensin II receptors
Give an example of an ARB
Losartan
Give an example of an alpha blocker
Doxazosin
What do mineralocorticoid antagonists block?
Aldosterone receptors
When might spironolactone be prescribed?
Resistant HTN
Name a mineralocorticoid antagonist.
Spironolactone
What drugs may be prescribed for vasodilation in angina?
Nitrates
Calcium antagonists
What drugs may be used to reduce HR in angina?
Beta blockers
Calcium antagonists
Ivabradine
What are some side effects of nitrates?
Headache
Hypotension
To avoid tolerance what should be advised when prescribing nitrates?
8 hours a day nitrate free
When can ivabradine act on HR?
Only in sinus rhythm
What are the categories of anti thrombotic drugs?
Antiplatelet
Anticoagulants
Fibrinolytics
Give some examples of antiplatelets.
Aspirin
Clopidogrel
Prasugrel
Ticagrelor
Give some examples of anticoagulants.
Heparin
Fonaparinux
Warfarin
Rivaroxaban
Dabigatran
Edoxaban
How is a warfarin overdose reversed?
Vitamin K
Give an example of a fibrinolytic.
Streptokinase
What can be used to chemically cardiovert in AF?
Amiodarone
Flecainide
What are the 4 pillars of HF therapy?
ARNI/ACEi
Beta blocker
MRA
SGKT2i
What effect do neprilysin inhibitors have?
ARB and prevent breakdown of naturitic peptides increasing vasodilatory naturitic peptides
What is nicorandil?
K ATP channel opener
What are some side effects of digoxin?
Nausea
Yellow vision
Bradycardia
Heart block Ventricular arrythmias
What effect does digoxin have?
Blocks AV conduction producing a degree of AV conduction delay
