Cardiovascular Principles Flashcards
How do we treat a cardiac tamponade?
Pericardiocentesis
Pericardial cavity fills with blood?
Haemopericardium/Cardiac tamponade
What are the branches of the arch of aorta (from right to left)?
Brachiocephalic trunk
Left common carotid
Left subclavian a.
From right to left, what order do the great vessels appear when look at the anterior surface of the heart?
SVC
Aorta
Pulmonary trunk
What is the coronary sinus?
Venous conduit
Drains cardiac veins to RA
Do the coronary arteries arrive just above or just below the aortic valve?
Just above
Which artery supplies the RV?
Right marginal artery
Which artery supplies the posterior interventricular septum?
Posterior descending artery (r. coronary artery branch)
What artery supplies the posterolateral LV?
Circumflex artery (l. coronary branch)
What does the left anterior descending artery supply?
Anterolateral myocardium
Apex
Interventricular septum
What causes the first heart sound?
Tricuspid and mitral valve shutting
What causes the second heart sound?
Aortic and pulmonary valves shutting
When sympathetic nerves leave the spinal cord, what can they do?
Go into ganglion at that level
Travel in sympathetic chain
Pass through without synapsing then synapse at prevertebral ganglia
Pass to adrenal medulla
What does autonomic innervation of the heart do?
Increase heart rate
Increase contractility
What does parasympathetic innervation of the heart do?
Decrease heart rate
What afferent nerves are present in the arch of aorta?
Baroreceptor reflex afferents in vagus nerve
Where are visceral afferent nerves located in the heart?
Inner aortic arch PT Around SA node Outflow tracts of RV and LV Papillary muscles SVC and IVC
Where do somatic sensory action potentials travel to?
Postcentral gurus
Of the parietal lobe
In the cerebral cortex
Where are somatic motor sensations relayed back from?
Precentral gurus
Of the frontal lobe
What is phase 4/Funny current of the pacemaker potential?
Slow sodium ion influx
Decreased potassium ion efflux
What occurs in rapid depolarisation and what phase is this in the pacemaker AP?
Rapid calcium ion influx
Phase 0
What happens during repolarisation and what phase is this?
Increased potassium ion efflux
Phase 3
Describe the spread of excitation in the heart
From SA node to AV node
From SA node through both atria
From AV node through bundle of His
From bundle of His through Purkinje fibres
What type of cell junctions allow easy conduction in the heart?
Gap junctions
What three junctions form an intercalated disc as seen in heart muscle?
Gap junctions
Desmosomes
Fascia adherens
Where is the SA node located?
Near entrance of SVC into RA
Where is the AV node located?
At base of RA near junction to RV
What are each of the phases in the ventricular muscle action potential?
Phase 0 - Rapid Na influx Phase 1 - Slow potassium efflux Phase 2 - Plateau due to Calcium influx Phase 3 - Rapid potassium efflux Phase 4 - Resting membrane potential (-90mV)
Why is the intrinsic heart rate slowed from ~100bpm to ~70bpm?
Continuous vagal tone influences SA node at rest
What is defined as sinus bradycardia?
<60bpm
What is defined as sinus tachycardia?
> 100bpm
What effects does the vagus nerve have on the heart?
Decreased SA node firing
Increased AV nodal delay
How does atropine work?
Inhibits ACh to increase HR
What effect does the vagal tone have on the pacemaker potential slope?
It is decreased
So it takes longer to reach threshold - Negative chronotropic can effect
What noradrenergic receptors play the biggest role in the heart?
Beta1
What effect does NA have on the heart pacemaker potential?
Increases slope
What is the role of desmosomes?
Provide mechanical adhesions
Ensure tension is transmitted cell to cell
What two filaments are Myofibrils made from?
Myosin (thick and dark)
Actin (thin and lighter)
How are the filaments in myofibrils arranged?
Into sarcoma reds
What is the A band?
Length of myosin
What is the I band?
Section containing only actin
What is the H zone?
Area of myosin only (ie no actin overlap)
How is a single sarcomere defined?
Segment between two Z lines
Briefly describe the process of a power stroke
In the presence of calcium ions, myosin cross bridge binds to actin
ATP on myosin is hydrolysed, bending the cross bridge
Actin pulled along
In presence of ATP, it binds to myosin
Myosin detaches and realigns
What occurs in the absence of further ATP during the power stroke?
Rigor mortis
Why are calcium ions required for initiation of the power stroke?
Pulls away the troponin-tropomyosin complex to allow myosin-actin binding
During systole, where do the calcium ions come from?
Calcium ions influx into cell
Calcium induced calcium release (CICR) from sarcoplasmic reticulum
(Contraction)
What happens to the calcium ions in the cell during diastole?
Calcium influx ceases
Calcium ions re-sequestered into SR by Calcium-ATPase
(Relaxation)
What is the refractory period?
Period of time after an AP when another cannot be generated
What is the equation for the stroke volume?
SV = EDV - ESV
What intrinsic factors determine the end diastolic volume and hence stroke volume?
Venous return
Preload
What is the preload of the heart?
The end diastolic pressure that stretches the ventricles ie the greatest length of the sarcomeres
What is the afterload of the heart?
The resistance into which it pumps
How does sympathetic stimulation increase the force of contraction?
Activated calcium channels
Greater calcium influx
How does sympathetic stimulation increase the HR?
Increased peak ventricular pressure - increased rate of change - decreased duration of systole
Increased rate of ventricular relaxation due to increased calcium efflux - decreased duration of diastole
At 75bpm, what is the approximate length of
- Diastole
- Systole
- 0.5s
2. 0.3s
What are the five events in the cardiac cycle?
- Passive filling
- Atrial contraction
- Isovolumetric ventricular contraction
- Ventricular ejection
- Isovolumetric ventricular relaxation
How full do the ventricles become during passive filling (%)?
80%
What is the approximate EDV?
130ml
What is the approximate ESV?
65ml
Why does arterial pressure not fall to zero during diastole?
Aortic walls recoil
Maintains pressure
Forces blood forward
When is blood flow audible?
When diastolic BP < external pressure < systolic BP
What Korotkoff sounds do we use for BP measurements?
1st sound - systolic 5th sound (silence) - diastolic
What is the equation for mean arterial pressure (using DBP and SBP)?
MAP = ([Diastolic BP x 2] + Systolic BP)/3
What MAP is needed to perfume the major organs?
60mmHg
When BP falls, do cardiac sympathetic efferents or cardiac vagal efferents Fire more?
Sympathetic
Where are baroreceptors located in the heart?
Aortic arch (via CN x) Carotid sinus (via CN ix)
What events occur in postural hypotension?
Decreased venous return Transient decrease in MAP Decreased baroreceptor firing Decreased vagal tone/increased SNS tone Increased HR and SV and TPR (vasoconstriction) Increased venous return
What happens to the baroreceptor response in sustained hypertension?
Firing decreases
They ‘reset’
Only fire of BP rises even hire
Control of MAP now relies solely on blood volume control
What does renin do, when is it released, and where from?
Stimulates angiotensin i formation from liver angiotensinogen
Hypovolaemia/Hypotension
Kidney (juxtaglomerular apparatus)
What does angiotensin ii do?
Stimulates aldosterone release
Vasoconstriction
Increases thirst
Increases ADH release
What does aldosterone do?
Causes vasoconstriction
ADH release
Increased sodium and water retention
Increased BP
How is RAAS regulated?
Renal artery hypotension
SNS stimulation
Decreased [Na+] in renal tubular fluid
When is atrial natriuretic peptide released and what does it do?
In hypervolaemic states due to atrial stretching
Causes excretion of sodium ions and water
Decreases BP
Vasodilator
Decreases renin release
Where is the majority of the body’s blood at any given time?
In veins
What receptors does NA act on in vascular smooth muscle?
Alpha
What effect does adrenaline have on vascular smooth muscle presenting the following receptors?
- Alpha
- Beta
- Vasoconstriction
2. Vasodilation
Where are alpha-receptors predominant?
Skin
Gut
Kidney arterioles
Where are beta receptors predominant?
Cardiac muscle
Skeletal muscle
What metabolic changes cause VSM relaxation?
Decreased local PaO2 Increased local PaCO2 Increased local pH Increased extracellular potassium Increased ECF osmolariry Adenosine release (ATP)
What other chemicals cause vasodilation?
Histamine
Prostaglandins
Bradykinin
Nitric oxide
What factors increase venous return?
Increased venomotor tone
Increased blood volume
Increased skeletal muscle pump
Increased respiratory pump
What is the respiratory pump?
During inspiration
- Intrathoracic pressure falls
- Intra-abdominal pressure rises
- Pressure difference between abdominal IVC and thoracic IVC pushes blood towards RA
What is venomotor tone controlled by?
SNS -> Stimulation -> Constriction
What is the skeletal muscle pump?
Large veins lie between muscles
Muscle contraction forces blood towards heart
What is cardiogenic shock?
Decreased contractility resulting in hypotension
How do we treat shock?
- ABCDE
- High flow oxygen
- Volume replacement (14G cannulae in each antecubital fossa - 500ml 0.9% NaCl quickly)
- Inotropes (Cardiogenic shock)
- Adrenaline (Anaphylactic shock)
- Vasopressors (Septic shock)
What is the P wave and how long should it last?
Atrial depolarisation
0.08-0.10s (2-2.5 small squares)
What is the QRS complex and how long should it last?
Ventricular depolarisation
What is the T wave?
Ventricular repolarisation
Why can we not see an atrial repolarisation wave?
It is masked by the QRS complex
What does the PR interval represent and how long should it last?
AV nodal delay (atrial systole)
0.12-0.20s (3-5 small squares)
What does the ST segment represent?
Ventricular systole
What does the TP interval represent?
Diastole
Which leads are the septal leads?
V1
V2
Which leads are the anterior leads?
V3 (Anteroseptal)
V4 (Anterolateral)
Which leads are the lateral leads?
V5
V6
I
aVL
Which leads are the inferior leads?
II
III
aVF
How can we calculate the HR from an ECG?
300/Number of large squares between each R-R Interval
How do we calculate the HR from an ECG in a person with an irregular heartbeat?
Count the number of peaks in 30 large squares (6 seconds) and multiply by ten
What do NA and adrenaline activate and couple with in the heart?
Beta1 adrenoceptors
Gs (activates adenylyl cyclase and cGMP production)
What does acetylcholine activate and couple with?
M2 muscarinic Gi coupling (inhibits adenylyl cyclase and cAMP production)
What is the name of the channels allowing the influx of sodium know as the funny current?
Hyperpolarisation-activated Cyclic Nucleotide gated channels (HCN)
What does Ivabradine do?
Blocks HCN Slows HR (in angina reduces Oxygen consumption)
What effect does the SNS have on the heart?
Increased contractility
Decreased AV nodal delay
Increased automacity
Where are the sites of Protein Kinase A action and the effects?
L-type Calcium channels - greater influx
Ryanadine receptors - greater CICR
SERCA 2a - phospholamban dissociates allowing quicker removal of calcium at end of HB
Troponin - decreased affinity for calcium therefore increasing relaxation
When are beta-blockers used?
Cardiac arrhythmias
Hypertension
Angina
CCF
What are the side effects of Beta-Blockers?
Bronchospasm Aggravation of CCF Bradycardia Hypocalcaemia Fatigue Cold extremities
What is an example of a non-selective muscarinic ACh antagonist?
Atropine
What drugs are used as anti-hypertensives?
Thiazides Calcium antagonists Alpha blockers ACe inhibitors ARBs
What drugs are used in angina?
Beta-blockers
Calcium antagonists
Nitrates
Nicorandil
What three classes of anti-thrombotic drugs exist?
Antiplatelet
Anticoagulants
Fibrinolytics
What are the side effects of diuretics?
Hypokaelamia
Hyperglycaemia
Gout
Impotence
What are the two types of calcium channel antagonists and examples of each?
Rate limiting - Verapamil - Diltiazem Non-rate limiting - Amlodipine
When are alpha blockers used?
Hypertension
Prostatic hypertrophy
Eg is Doxazosin
What are some side effects of ACE inhibitors?
Cough Renal dysfunction Angioedema Hyperkalaemia Headache Hypotension
What are side effects of organic nitrates?
Morning headache
Hypotension
Tolerance
When are anticoagulant drugs used?
DVT
PE
NSTEMI
AF
What are some examples of fibrinolytic drugs?
Streptokinase
tPA
What are the side effects of digoxin?
Nausea Vomiting Yellow blurred vision Bradycardia Heart block Ventricular arrhythmias
What does Nicorandil do?
Opens ATP-mediated potassium channels in VSM
Which has a stronger diuretic effect, thiazides or loop diuretics?
Loop
What is an example of a potassium-sparing diuretic?
Triamterene
What are the four major lipoproteins?
HDL
LDL
VLDL
Chylomicrons
What apoproteins do the lipoproteins contain?
HDL - apoA1 and apoA2
LDL - apoB100
VLDL - apoB100
Chylomicrons - apoB48
What do apoB containing lipoproteins do?
Deliver triglycerides to
- Muscle (for ATP production)
- Adipocytes (for storage)
Where are chylomicrons formed and what is there function?
Intestine
Transport dietary fats
Where are VLDLs formed and what is their function?
Liver
Transport synthesised fats
What happens to chylomicrons and VLDLs after they have transported the fats?
Bind to lipoprotein lipase (LPL) via apoCII (from HDL)
Triglyceride core hydrolysed - they are now cholesterol rich
ApoCII exchanged for apoE - remnants
Metabolised by hepatic lipase
50% of apoB100 become LDLs
Why is LDL bad?
It is oxidised in artery intima
Attracts macrophages - take in OXLDL - foam cells - fatty streak
Inflammation - collagen deposition
Atheromatous plaque forms
Why is HDL good?
Brings cholesterol to the liver for elimination
How do statins work?
Inhibit HMG-CoA reductase
Prevents cholesterol formation
What are the side effects of statins?
Myositis
Rhabdomyolysis
What does ezetimibe do?
Inhibits NPC1L1 transport protein - decreased cholesterol absorption
What are the three layers of blood vessels (inner to outer)?
Tunica intima
Tunica media
Tunica adventitia
Where does the outer half of the walls of elastic aeries get nutrients from?
Vasa vasorum
What are the three types of capillary?
Continuous
Fenestrated
Sinusoidal/Discontinuous
How are heart valves anchored?
Via chordae tendinae to papillary muscles
Histologically, does the SA node appear darker or lighter than surrounding cells?
Lighter (less organelles present)
How does digoxin work?
Blocks Na/K ATPase (binds to alpha subunit)
This increases intracellular [Na]
This increases [Ca]i
Increased Ca storage in sarcoplasmic reticulum
Increased CICR therefore increased contractility
What is the levosimendan?
Makes TnC more sensitive to Ca
Used in acute decompensated heart failure
What does active Myosin Light Chain Kinase do?
It converts myosin LC to myosin LC P
This results in contraction
What is the role of active Myosin LC phosphatase?
Converts myosin LC P to myosin LC
This causes relaxation
What is required for the activation of MLCK?
Calcium ions
What is required for the activation of Myosin-LC Phosphatase?
cGMP
What does NO (and hence organic nitrates) do to VSM tone?
Activates guanylate cyclase
GTP -> cGMP
Activates protein kinase G
Relaxation
What is isosorbide mononitrate do?
It is a prophylactic organic nitrate (longer half life)