Cardiovascular Flashcards
Where can thrombosis occur?
Thrombosis can occur in:
Arterial circulation: high pressure - platelet rich
Venous circulation: low pressure - fibrin rich
What is the normal bleeding time?
2-7 minutes
List a symptom that could occur due to an arterial thrombosis in the coronary circulation?
- Angina
- Shoulder pain
- Sudden death
List a symptom that could occur due to an arterial thrombosis in the cerebral circulation?
- Headache
- Slurred speech
- Unilateral weakness
- CVA cerebral vascular accident
List a symptom that could occur due to an arterial thrombosis in the peripheral circulation?
- Pain in leg
- Stomach-ache
What is the underlying cause of arterial thrombosis in majority of cases?
When an artery is damaged by atherosclerosis
List some examples of Arterial thrombosis Aetiology
Atherosclerosis
Inflammatory
Infective
Trauma
Tumours
What is the treatment for coronary arterial thrombosis?
- Aspirin.
- LMWH or Fondaparinux or UFH
- Thrombolytic therapy
- Reperfusion
What is the treatment for cerebral arterial thrombosis?
- Aspirin, other anti-platelets
- Thrombolysis
- Catheter directed treatments
Reperfusion
Why is heparin not used in patients who have had a CVA (cerebral vascular accident)
Increased risk of bleeding complications
What is the treatment for arterial thrombosis in other sites?
- Antiplatelets, statins
- Role of anticoagulants evolving
- Endovascular vs Surgical
Why is Fondaparinux used instead of heparin?
Much higher risk of bleeding when using heparin.
Fondaparinux also has a longer half life.
Where does venous thrombosis occur?
*Peripheral - such as the ileofemoral, femoro-popliteal
- Other sites such as cerebral and visceral
What are the symptoms of DVT?
Usually non-specific symptoms, pain and swelling, groin strain. Calf pain, chest pain, and breathlessness is a common clinical scenario however.
Briefly describe the investigations might be done in order to diagnose a DVT.
- D-dimer; looks for fibrin breakdown products. If normal, you can exclude DVT. Abnormal does not confirm diagnosis however.
- Ultrasound compression scan; if you can’t squash the vein = clot.
What is the treatment for DVT?
- Heparin or LMWH.
- Oral warfarin or DOAC.
- Endo-vascular treatment
Give 5 risk factors for DVT.
- Surgery, immobility, leg fracture.
- OCP, HRT.
- Long haul flights.
- Genetic predisposition: Factor 5 Leiden
- Pregnancy.
Causes of thrombosis (Virchow’s triangle, typically 2 out of these 3)
- Hypercoagulability
- Venous stasis
- Endothelial damage
When would the treatment of DVT be more aggressive?
when the DVT are really long ie right to the IVC from the leg, and when patients are really symptomatic.
Prevention of DVT
- Mechanical or chemical thromboprophylaxis
- Compression socks
- Also early mobilisation and good hydration
What is heparin?
- Heparin is an anticoagulant
- It activates antithrombin which then inhibits thrombin and factor Xa.
- It has a short half-life
How is unfractionated heparin administered? (UFH)
Intravenously, continuous infusion
How is low molecular weight heparin administered? (LMWH). What is it used for?
Once daily, weight-adjusted dose given subcutaneously. Used for treatment and prophylaxsis
Is HIT (Heparin induced thrombocytopenia) more common after LMWH or UFH?
UFH
Why might you use UFH over LMWH?
UFH has a short half life and its effects are easier to reverse. UFH might also be more effective.
What is Warfarin?
Warfarin is an anticoagulant.
- It produces NON-functional clotting factors 2, 7, 9 and 10.
- Orally active
- Long half life (36 hours)
- Prolongs the prothrombin time
What is warfarin the antagonist of?
Vitamin K.
Why is warfarin difficult to use?
- Lots of interactions!
- Teratogenic.
- Needs almost constant monitoring.
What are DOAC/NOAC?
Direct oral anticoagulants/ new oral anticoagulants.
Directly acts on factor II or X
Eg: apixaban
No monitoring needed
Shorter half lives
Used for extended thromboprophylasis and treatment of AF and DVT/PE
Why are DOACs not used in pregnancy or in metal heart valves?
Pregnancy: Potential for reproductive toxicity
MHV:
It is associated with an increased risk of thromboembolic events and increase in clots and strokes
What is Fondaparinux?
It is an anticoagulant that indirectly inhibits factor Xa.
Preferred in patients more prone to HIT.
What is aspirin?
It is an antiplatelet that Inhibits cyclo-oxygenase irreversibly. Inhibits thromboxane formation and hence platelet aggregation
Act for lifetime of platelet, 7-10 days
Used in arterial thrombosis, 75-300 mg od
Drug for antiplatelet therapy in angina if aspirin intolerant?
Clopidogrel, prasugrel, ticagrelor
How does Clopidogrel work?
When platelets are activated they release dense granules which release ADP and can bind to P2Y12. P2Y12 can then amplify platelet activation. Clopidogrel inhibits P2Y12 receptor and reduces platelet activation
What is dual antiplatelet therapy?
Management of ACS using a combination of aspirin and a P2Y12 inhibitor
Clopidogrel vs prasugrel which is better?
Prasugrel is much more reliable and useful because it is a more efficient prodrug and has a direct liver breakdown pathway while clopidogrel effectiveness relies on genetics alongside other factors
Adverse effects of P2Y12 inhibitors
Common to all:
*Bleeding eg epistaxis, GI bleeds, haematuria
*Rash
*GI disturbance
Ticagrelor:
*Dyspnoea (shortness of breath)
*Ventricular pauses
Why are GPIIb//IIa antagonists used selectively? (antiplatelet drugs)
*Only IV drugs available
*Increase risk of major bleeding
*But still used in combination with aspirin and oral P2Y12 inhibitors in management of patients undergoing PCI for ACS
DVT signs
tenderness, swelling, warmth, discolouration
DVT complications
Phlegmasia Alba Dolens and Phlegmasia Cerulae Dolens, PE
How can DVT cause ischaemia?
An acute significant widespread venous embolism in a leg causes so much swelling that it blocks the blood flow through the leg. The leg becomes pale or blue and extremely painful. Gangrene (dead tissue) can develop if the blood flow is not restored.
In standard treatment of DVT, why is heparin used initially before switching to warfarin?
Heparin displays an anticoagulant effect within 1 day, while the anticoagulant effects of warfarin are not evident until the third day of therapy. If rapid anticoagulant effects are needed, heparin should be initiated first, and warfarin should be started later on.
Pulmonary Embolism symptoms
breathlessness, pleuritic chest pain, pain in leg
Pulmonary embolism signs
tachycardia, tachypnoea, pleural rub
Pulmonary Embolism Differential diagnosis
Musculoskeletal, Infection, Malignancy, Pneumothorax, Cardiac, GI causes
Pulmonary embolism initial investigations
CXR usually normal
ECG sinus tachy, (QI,SI,TIII)
Blood gases: type 1 resp failure, decreased O2 and CO2
Mainly done to exclude alternative causes
Pulmonary embolism: further investigations
Further investigations include D-dimer: normal excludes diagnosis
CTPA spiral CT with contrast, visualise major segmental thrombi
Ventilation/ Perfusion scan: mismatch defects
Pulmonary embolism treatment
Supportive treatment
LMW Heparin
Oral warfarin (INR 2-3)for 6 months
DOAC/NOAC
Treat underlying cause
Pulmonary embolism prevention
Anticoagulation
IVC filters - (can be used to catch clots)
How are massive pulmonary embolisms treated?
Thrombolytic therapy
Streptokinase and tPA
Complications of a massive pulmonary embolism
Haemodynamic instability
Hypotension, cyanosis, severe dyspnoea, right heart strain/ failure
What is peripheral vascular disease (or peripheral arterial disease)? PVD/PAD
Peripheral vascular disease is essentially reduced blood supply and ischaemia in the lower limbs due to atherosclerosis and thrombosis in the arteries
What is the most potent risk factor in PAD?
Using tobacco products
Risk factors for PAD. Modifiable and non-modifiable
Modifiable:
Smoking
Hypertension
Diabetes
Hypercholesterolaemia
Non-modifiable:
Sex
Age
Three main patterns of presentation of PVD?
- Intermittent claudication (least severe)
- Critical limb ischaemia
- Acute limb-threatening ischaemia (most severe)
Name the classification system for peripheral vascular disease (PVD).
Brief description.
Fontaine classification.
4 stages:
1. Asymptomatic
2. Intermittent claudication
>200m pain free walking
<200m pain free walking
3. Chronic limb ischaemia (pain at rest)
4. Ischaemic ulcers → gangrene
Features of of acute limb-threatening ischaemia
6Ps
* Pulselessness
* Pallor
* Pain
* Perishingly cold
* Paralysis
* Paresthesia
Acute-embolus (AF, MI)
Acute on chronic-thrombus
Features of chronic limb-threatening ischaemia
*IC (intermittent claudication)
*Rest pain
*Tissue loss
*Burger’s test
6Ps present in chronic limb ischemia too but more you have=more limb threatening
Management of peripheral vascular disease?
- Intermittent claudication
Manage risk factors… decrease BMI, cease smoking, control BP, statins and antiplatelets and T2DM control - Chronic limb ischaemia
Revascularisation surgery… PCI if small, bypass if larger
Amputation if severe - Acute limb threatening ischaemia
Surgical emergency → revascularisation within 4-6 hours… otherwise very high amputation risk
What is the name of the circle consisting the arterial supply to brain?
Circle of Willis
Are the majority of TIA/strokes ischaemic or haemorrhagic?
Ischaemic! 60%
In TIA/stroke is it embolization or thrombosis which is aetiologically important?
Thrombosis
What is an aneurysm?
Weakening of the arterial wall leading to dilatation and bulging of the wall
Most common location of an aneurysm?
Commonest location is the infra-renal aorta
What are false aneurysms/pseudo aneurysms caused by?
Damage to wall of artery (ie by cardiologists)
Usually doesn’t involve damage to all 3 walls.
What are mycotic aneurysms caused by?
Weaknesses in the wall related to infection.
Initial investigations for in PVD?
- Bloods – Lipids, Glucose, Renal function, Vasculitic screen, Clotting, FBC
- ABPI
- Duplex
- Cross sectional Imaging
What is the diagnosis of peripheral vascular disease?
*ABPI → comparing blood in post+ant tibial artery, to the brachial artery with a doppler ultrasound
0.9-1.3 is normal
0.5-0.9 = intermittent claudication
<0.5 = critical limb ischaemia
When ABPI is VERY low… there is a risk of acute life threatening ischaemia
*Colour duplex ultrasound → assess the degree of stenosis
*CT Angiography if surgery is considered
What information does duplex give you?
Gives information about the flow of blood ie whether there is backflow etc.
Assess location and severity of stenosis.
CTA vs MRA vs Catheter angiography
CTA and MRA are both non-invasive while a Catheter angiography requires insertion of a catheter into the area.
All CTAs require the use of an IV contrast agent, but not all MRAs do.
CTAs require just a few minutes to complete; MRAs may require 20-30 minutes.
What are the advantages of MRA over CTA?
CTAs involve exposure to radiation (see below), MRAs do not.
The contrast dyes in CTAs are also more toxic on the kidneys.
Give 4 treatments for peripheral vascular disease.
- Risk factor modification.
- Bypass surgery for critical leg ischaemia.
- Balloon angioplasty.
- Stenting of occlusion.
- Amuptation.
What are the advantages and disadvantages of bypass surgery for peripheral vascular disease?
Advantages:
Better patency and limb salvage rates
Disadvantages:
Higher morbidity and mortality
Should a patient with IC (intermittent claudication) have exercise or angioplasty or surgery?
Exercise! Graded exercise therapy is officially recommended.
Define abdominal aortic aneurysm? (AAA)
Permanent aortic dilation exceeding 50% where diameter >3cm
Typically infrarenal (below renal arteries), in elderly men
A negative risk factor for AAA?
Diabetes but unknown reason
Risk factors for AAAs?
Smoking = biggest risk factor
Increasing age
Hypertension
Connective tissue disorders - Ehlers Danos and Marfan syndrome (changes in balance of collagen and elastic fibres)
Family history
AAA Treatment
Elective surgery
Either:
1) EVAR (Endovascular aortic repair) - stent inserted through femoral/iliac artery
-Less invasive but more post op complications
2) open surgery
-more invasive but fewer complications
What is the current NICE recommendation for AAA repair open surgery or EVAR?
Open surgery is preferred by current NICE guidelines.
EVAR can be considered under medical or anaesthetic risks.
Carotid artery disease treatment
- Carotid Endarterectomy (standard treatment)
* opens the artery and removes the plaque. - Endovascular stenting
* fine catheter tube is passed through the skin and into the narrowed blood vessel. A metal tube (stent) is placed inside the vessel to prevent it narrowing again.
How would you treat incompetent deep veins that don’t return blood back to the heart?
Compression
What is the current NICE recommendation for treatment of varicose veins?
Surgical stripping - Endovenous laser varicose vein surgery
What prevents blood flowing distally?
Venous valves
Where is the saphenofemoral junction located?
4 fingers breadths lateral and inferior to the pubic tubercle on that common side
What does acute coronary syndromes cover?
Term covers a spectrum of acute cardiac conditions including unstable angina, NSTEMI and STEMI
How to define different acute coronary syndromes?
Unstable angina- severe ischaemia (no ECG changes)
NSTEMI- partial infarction + non-Q wave infarction
STEMI- transmural infarct and ST elevation in local ECG leads + Q wave infarction
Give 3 signs of unstable angina.
- Cardiac chest pain at rest.
- Cardiac chest pain with crescendo patterns; pain becomes more frequent and easier provoked.
- No significant rise in troponin.
Making a diagnosis of ACS? (Step by step) (primary investigations)
1) when patient presents with symptoms (eg chest pain) perform ECG
2) ST elevation or new left bundle branch block = STEMI
3) no ST elevation—-> troponin blood tests:
- increased troponin + changes (ST depression, t wave inversion or path Q waves) = NSTEMI
-normal troponin + no ECG changes then unstable angina or another cause (musculoskeletal chest pain)
What’s the difference between a stable and unstable angina?
Unstable angina:
* chest pain that occurs at rest
* not relieved by GTN
* occurs more frequently and lasts for longer.
Stable angina:
* Can be relieved by GTN
* Pain relieved at rest
What is Prinzmetal’s angina? ECG too…
Angina caused by coronary vasospasm (not due to cv vessel atherogenesis)
Seen increasingly in cocaine users
ECG shows ST elevation
Causes of ACS
Majority of cases: Rupture of an atherosclerotic plaque and subsequent arterial thrombosis.
Myocardial infarction due to atherothrombosis is known as type 1 myocardial infarction
Other causes of myocardial infarction usually fall under the umbrella of type 2 myocardial infarction:
- Drug abuse
- Oxygen demand/supply mismatch caused by sepsis, anaemia, haemorrhage etc
- coronary vasospasm without plaque rupture
What is Tako-Tsubo cardiomyopathy?
- Stress induced cardiomyopathy, may masquerade as myocardial infarction
- Often precipitated by acute stress such as extreme emotional distress in susceptible individuals
- Causes transient left ventricular systolic dysfunction, typically ballooning of the left ventricular apex during systole that recovers over days or a few weeks with limited or no permanent damage.
What does an ECG after MI look like?
- pathologically deep q waves
- ST segment elevation
Symptoms of myocardial infarction?
*Cardiac chest pain
- unremitting
- usually severe but may be mild or absent
- occurs at rest
- associated with sweating, breathlessness, nausea and/or vomiting
- 1/3 occur in bed at night
Aftermath of a myocardial infarction?
Usually causes permanent heart muscle damage although this may not be detectable in small MIs.
Management of a myocardial infarction?
*Initial management
- get in hospital quickly
- paramedics - if ST elevation, contact primary PCI centre for transfer for emergency coronary angiography
- Take aspirin 300 mg immediately
- Pain relief
*Hospital management
- make diagnosis
- oxygen therapy only if hypoxic
- pain relief - opiates/nitrates
- aspirin +/- platelet P2Y12 inhibitor
- consider beta-blockers
- consider other antianginal therapy
- consider urgent coronary angiography eg if troponin elevated or unstable angina refractory to medical therapy
MONAC!!
- M - morphine + anti-emetic (metoclopramide)
- O - O2 (if stats <94% or 88-92% if COPD)
- N - nitrates (GTN spray)
- A - aspirin 300 mg
- C - Clopidogrel/Ticagrelor (75mg dual antiplatelet_ or prasugrel if undergoing PCI
- Anticoagulant: fondaparinux or heparin
*Note not all patients require oxygen
What is troponin?
A protein complex consisting of troponin C, troponin I, and troponin T that regulates actin:myosin contraction
Cardiac specific isoforms of troponin T and troponin I are highly sensitive markers for cardiac muscle injury
When is platelet adhesion and secretion bad?
When it’s reacting to an atherosclerotic plaque rupture. As it causes a thrombus to form inside the artery and potentially occlude it.
Which part of the heart does the P wave represent?
The atrium
Which part of the ECG represents the ventricle?
The QRS wave
What is a patent foramen ovale?
A hole between the left and right atria of the heart that fails to close naturally after birth.
What is a paradoxical embolism?
This is when the patent foramen ovale allows venous thrombi to cross into the arterial system causing an ischemic stroke
Which conditions/syndromes is coarctation of the aorta associated with?
Turner’s syndrome and Berry aneurysms of the brain
Cardiac output equation
Cardiac output = heart rate x stroke volume
Mean arterial blood pressure equation
Mean arterial blood pressure = cardiac output x systemic vascular resistance
Normal physiology of heart
Normally- increased preload= increased afterload= increased cardiac output (frank starling law)
Overall pathophysiology of a failing heart! (heart failure)
Normally… an increased preload = increased afterload = increased CO…
But in heart failure, the cardiac myocytes are messed → frank starling law ineffective → decreased cardiac output…
RAAS+SNS tries to compensate this temporarily, to get BP high. This is why aldosterone and ADH are high as are Adrenaline and Norad
However, the compensation fails and the heart undergoes cardiac remodelling → decreased CO
This normally happens in 1 side of the heart. If it happens in both, this is known as congestive heart failure.
What causes cardiac ischaemia?
- Vessel occlusion
- coronary artery disease
- thrombosis and thromboembolism
- Arterial spasm/compression
- drugs (eg cocaine)
- stress (takotsubo)
- anomalous arteries
- myocardial bridging
- Oxygen demand/supply mismatch
- anaemia
- CO
- bleeding
- decreased cardiac output/bradycardia
Give 5 potential complications of MI.
D - Death
A - Arrhythmia
R - Rupture
T - Tamponade
H - Heart failure
V - Valve disease
A - Aneurysm
D - Dressler’s syndrome
E - Embolism
R - Recurrent regurgitation
DARTHVADER
What is atrial fibrillation
- 300-600bpm
- Irregularly regular atrial firing rhythm → causes irregularly irregular ventricular contraction
What is the most common cardiac arrhythmia?
Atrial fibrillation
Which is the most common artery involved in a stroke?
The middle cerebral artery (MCA)
A 60 year old retired school teacher is an ex smoker who has shortness of breath and heart murmur - ejection systolic, heard over aortic area, pitting oedema ankles. What is the likely diagnosis?
Heart failure - aortic stenosis
What is heart failure
Complex clinical syndrome - heart’s inability to effectively fill and/or eject blood
How is heart failure ejection fraction classified?
Normal = 50–70%
> 50% = preserved
Diastolic failure (filling issues)
< 40% = reduced
Systolic failure (pump issues)
Describe the NYHA classification for heart failure.
- Class 1: heart disease is present but there is no limitation.
- Class 2: comfortable at rest but slight limitation on activity - mild HF.
- Class 3: marked limitation - moderate HF.
- Class 4: SOB at rest, all activity causes discomfort (severe HF).
What is arrhythmogenic cardiomyopathy?
It is associated with genetic mutations that leads to myocytes to die and be replaced with fat and scar tissues.
It leads to arrhythmia and can lead to sudden cardiac death in young adults
What is angina?
Mismatch of oxygen demand and supply
What is the most common cause of angina?
Narrowing of the coronary arteries due to atherosclerosis.
Predisposing factors for ischaemic heart disease IHD (list 4)
- Age
- Cigarette smoking
- Family history
- Diabetes mellitus
- Hyperlipidemia
- Hypertension
- Kidney disease
- Obesity
- Physical inactivity
- Stress
Exacerbating factors for ischaemic heart disease IHD
Supply:
-Anemia
-hypoxemia
Demand:
-hypertension
-tachycardia
-valvular heart disease
Environmental factors for IHD
- cold weather
- heavy meals
- emotional stress
Briefly describe the pathophysiology of angina that results from atherosclerosis.
On exertion there is increased O2 demand. Coronary blood flow is obstructed by an atherosclerotic plaque -> myocardial ischaemia -> angina.
Briefly describe the pathophysiology of angina that results from anaemia.
On exertion there is increased O2 demand. In someone with anaemia there is reduced O2 transport -> myocardial ischaemia -> angina.
How do blood vessels try and compensate for increased myocardial demand during exercise.
When myocardial demand increases e.g. during exercise, microvascular resistance drops and flow increases!
Physiology of ischaemic heart disease
Myocardial ischemia occurs when there is an imbalance between heart’a oxygen demand and supply, usually from an increase in demand accompanied by limitation of supply:
1) impairment of blood flow by proximal arterial stenosis
2) increased distal resistance eg. Left ventricular hypertrophy
3) reduced oxygen-carrying capacity of blood eg. Anaemia
How to assess chest pain?
OPQRST
O - Onset
P - Position (site)
Q - Quality (nature/character)
R - Relationship (with exertion, posture, meals, breathing and with other symptoms)
R - Radiation
R - Relieving or aggravating factors
S - Severity
T- Timing
T - Treatment
At what point does the coronary flow fall off in stenosis and cause a rapid decline?
When the diameter stenosis reaches 70%
How can angina be reversed?
Resting - reducing myocardial demand.
How would you describe the chest pain in angina?
- Chest pain (tightness/ discomfort) ***
- Breathlessness **
- Fluid retention
- Palpitation
- Syncope or pre-syncope
Differential diagnosis for myocardial ischemia
- Pericarditis/myocarditis
- Pulmonary embolism/pleurisy
- Chest infection/ pleurisy
- Dissection of the aorta
- Gastro-oesophageal (reflux/spasm/ulceration)
- Musculoskeletal
- Psychological
Treatment for myocardial ischemia
- Reassure
- Lifestyle
- smoking
- Weight
- Exercise
- Diet
- Advice for emergency
- Medication
- Revascularisation
What tool can you use to determine the best investigations and treatment in someone you suspect to have angina?
Pre-test probability of CAD. It takes into account gender, age and typicality of pain.
What investigations might you do in someone you suspect to have angina?
- ECG - usually normal, there are no markers of angina.
- Echocardiography.
- CT angiography - has a high NPV and is good at excluding the disease.
- Exercise tolerance test - induces ischaemia.
- Invasive angiogram - tells you FFR (pressure gradient across stenosis).
A young, healthy, female patient presents to you with what appears to be the signs and symptoms of angina. Would it be good to do CT angiography on this patient?
Yes. CT angiography has a high NPV and so is ideal for excluding CAD in
younger, low risk individuals.
Treatment for angina
At the GP:
- Aspirin
- Nitrates - GTN - Ca++ CB
- β Blocker
- Statin
At hospital:
CTCA/functional test of ischaemia
- ACE inhibitor
- Long acting nitrate
If still no improvement:
- Revascularisation: PCI/CABG: MDT meeting
- Ca++ channel blocker
- Potassium channel opener
- Ivabradine
Effects of β blockers on the heart
Beta blockers are beta 1 specific. They antagonise sympathetic activation and so are negatively chronotropic and inotropic.
Myocardial work is reduced and so is myocardial demand = symptom relief.
Give 3 side effects of beta blockers.
- Bradycardia.
- Tiredness.
- Erectile dysfunction.
- Cold peripheries.
When might beta blockers be contraindicated?
They might be contraindicated in someone with asthma or in someone who is bradycardic.
Describe the action of nitrates.
i.e GTN sprays
Nitrates e.g. GTN spray are arterial and venous dilators -> reduction of preload and afterload -> reduced myocardial work and myocardial demand -> lower BP
Describe the action of Ca2+ channel blockers.
Ca2+ blockers are arterodilators -> reduced BP -> reduced afterload -> reduced myocardial demand.
Name 2 drugs that might be used in someone with angina or in someone at risk of angina to improve prognosis.
- Aspirin.
- Statins.
How does aspirin work?
Aspirin irreversibly inhibits (cyclooxygenase 1) COX. You get reduced TXA2 synthesis and so platelet aggregation is reduced.
Caution: Gastric ulcers!
What are statins used for?
They reduce the amount of LDL in the blood.
What do ACE inhibitors do?
Reduces blood pressure.
Angiotensinogen is converted to angiotensin 1 via renin. Angiotensin 1 is then converted to angiotensin 2 via ACE. ACE inhibitors prevents angiotensin 1 binding and so you don’t get angiotensin 2 formation. (Angiotensin 2 is a vasoconstrictor and so ACE can be used in the treatment of hypertension).
What is revascularisation?
Revascularisation might be used in someone with angina. It restores the patent coronary artery and increases blood flow.
Name 2 types of revascularisation.
- PCI.
- CABG.
Give 2 advantages and 1 disadvantage of PCI.
- Less invasive.
- Convenient and acceptable.
- High risk of restenosis.
Give 1 advantage and 2 disadvantages of CABG.
- Good prognosis after surgery.
- Very invasive.
- Long recovery time
When is PCI and CABG preferred?
STEMI - PCI preferred
NSTEMI - PCI preferred, CABG may be used
Stable angina - both PCI and CABG used
Briefly describe the electrical conduction pathway in the heart.
- The SAN generates an electrical impulse.
- This generates a wave of contraction in the atria.
- Impulse reaches AVN.
- There is a brief delay to ensure the atria have fully emptied.
- The impulse then rapidly spreads down the Bundle of His and Purkinje fibres.
- The purkinje fibres then trigger coordinated ventricular contraction.
What is an ECG?
The electrocardiogram is a representation of the electrical events of the cardiac cycle
How does an ECG work?
Contraction of any muscle is associated with electrical charges called depolarisation. These changes can be detected by electrodes attached to the surface of the body
What are the three basic laws of electrocardiography?
Electrical activity towards a lead causes an upward deflection.
Electrical activity away from a lead causes a downward deflection.
If the lead is 90 degrees to the wave of depolarisation then you get a biphasic wave form.
ECG electrodes: what are bipolar and unipolar leads?
*Bipolar leads measure 2 different points on the body
*Unipolar leads measure 1 point on the body and a virtual reference point with zero electrical potential located in the centre of the heart
Standard ECG has 12 leads. What do these include?
- 3 bipolar limb leads, I II III
- 3 augmented unipolar limb leads - AVR, AVL, AVF
- 6 unipolar precordial leads
What is the direction of the bipolar limb leads?
Lead I
Right to left wrist
- on right wrist
+ on left wrist
Lead II
Right wrist to left leg
- on right wrist
+ on left leg
Lead III
Left wrist to left leg
- on left wrist
+ on left leg
What is the position of the unipolar augmented limb leads?
aVR - right shoulder
aVL - left shoulder
aVF - symphysis pubis
What are the pacemakers of the heart?
SA node - dominant pacemaker
60 - 100 beats/min
AV node - back-up pacemaker
45 - 50 beats/min
Bundle of His - back-up pacemaker
40 - 45 beats/min
ECG: what is the J point?
Where the QRS complex becomes the ST segment.
ECG: what is the normal axis of the QRS complex?
-30° -> +90°
ECG: what does the P wave represent?
Atrial depolarisation.
ECG: what does the PR interval represent?
AV node conduction delay
ECG: how long should the PR interval be?
120 - 200ms.
3 - 5 little squares
ECG: what might a long PR interval indicate?
Heart block.
ECG: how long should the QT interval be?
0.35 - 0.45s.