IHD Symposium -Stable IHD Flashcards
What are the epicardial coronary vessels
Left and right coronary blood vessels because they sit on the heart surface
What symptom is caused by restricted coronary blood flow
Angina - almost always an effect of atherosclerosis
What is ischaemia
Mismatch between oxygen demand and oxygen supply
How does O2 supply demand mismatch occur in ischaemia
- Proximal arterial stenosis impairs blood flow
- Impairs distal resistance
- Reduced oxygen-carrying capacity of blood
By how much does the diameter have to decrease before symptoms of angina and ischaemia arise
Below 75% its original size
What determines the resistance of the epicardial arteries
The resistance of the microvascular vessels
If there is a LOW pressure in epicardial and HIGH in microvascular - low flow (3 ml/s - normal flow rate)
If there is a LOW pressure in epicardial and LOW in microvascular - high flow
When does resistance in microvascular vessels decrease and why is this necessary
During excersise
To supply the heart with more oxygen
How does epicardial disease effect the coronary arteries and how does it effect flow
Increases resistance in the epicardial vessels
Flow remained at 3 ml/s as microvascular resistance reduces (homeostasis)
Under what conditions can compensation of pressure no longer keep flow rate at 3 ml/s
During stenosis of epicardial arteries
Microvascular resistance can be lowered anymore
How does stenosis effect the heart
Myocardium becomes ischaemic and pain is experienced
How is IHD stopped after excersise
Rest
What is Prinzmetal’s angina
Coronary spasms
What is microvascular angina (syndrome X)
Microvascular vessels narrow which leads to hypoxia
What is Crescendo angina
Unstable angina - it changes or worsens after a period of time and/or occurs at rest
What would patients present with if they had angina
- Heavy, central, tight radiation to arms, jaw and neck
- Made worst by exertion
- Relieved by Rest or GTN
3/3 = typical agina 2/3 = atypical pain 1/3 = non-anginas pain
What can angina be mistaken for
Pericarditis/ Myocarditis Pulmonary embolism Chest infection Dissection of aorta Gastro-oesophageal reflux
What signs should we be looking for when diagnosing a patient for angina
- Hypercholesterolaemia
- Smoking
- Diabetes
- High BP
Scares from surgery (e.g. pacemakers)
How does an ECG help diagnosis of angina
12 Lead ECG - should be normal but could give us clues of IHD (T-wave inversions)
How does an Echocardiogram help diagnose for angina
Normal
Allows us to check LV function and see signs of previous infarcts (alternative diagnosis)
How do we initially manage patients with suspected SCAD (spontaneous Coronary Artery disease)
- Assess PTP (pre-test probability)
- Low PTP < 15%
- Intermediate (15-85%)
- High PTP (diagnosis of SCAD)
Two anatomical diagnostics for angina
CT angiography
Invasive Angiography
What does a CT angiography show us
Shows us all the vessels of the body (saggital cross-section) - narrowed vessels
What is the physiological diagnostic investigation for angina
- Exercise stress treadmill
- Stress echo
- Perfusion MRI
What is the treadmill test
Induce ischaemia while walking uphill incrementally fast
Look at ST segment - if depressed then that detects a late stage of ischaemia
Why is the treadmill test not suitable for everyone
- People can’t walk
- Unfit
- Young females
When is a CT angiogram suitable
Excluding CAD in younger individuals
When is a CT angiogram unsuitable
People with arrhythmias and calcified disease
what is an issue with CT angiograms
Low Positive Predictive Value
What can an invasive angiogram show us
Pressure gradient across the stenosis of the artery (going from 100 mmHg on one side of stenosis to 80 mmHg on the other side e.g.)
What is stress echo
Dynamic imagine with and without pharmacological stress
Look for regional wall motion abnormalities
What is a SPECT/ myoview
Radio-labelled tracer
Gives idea about degree of ischaemic MYOCARDIUM
How does SPECT work
Taken up by metabolising tissues
What does a 1st SPECT test show
Perfusion defects (looking at adenosine levels)
When would we bring a patient in for a second SPECT test
If there’s a perfusion defect
Fixed defect = scar
Reversible = isichaemia
What is primary prevention of CAD
Reducing risk of CAD and risk factors
We use SCORE tool which estimates 10 year risk of major CV even happening
What is secondary prevention of CAD
Risk factor modification
Prognostic therapy
Symptomatic therapy
Medications in primary prevention used to treat hypertension
Antihypertensives
Medications in primary prevention used to treat hypercholesterolaemia
Statins + Lipid modulating therapies
Medications in primary prevention used to treat T2DM
Diabetic therapy
Medications in primary prevention used to treat smoking
Cessation
Medications in primary prevention used to treat diet
General Advice
Medications in primary prevention used to treat excercise
Get Plenty
What are the three major arms of secondary prevention therapy
- Lifestyle changes
- Pharmacological
- Interventional
What are lifestyle changes in secondary prevention
- Risk factor and behaviour modification
What are pharmacological changes in secondary prevention
- Reduce CV events (aspirin, statin)
2. Reduce symptoms (nitrates)
What interventional changes in secondary prevention
- Reduce events
- Reduce symptoms
PCI
What drug is given to patients in secondary pharmacological prevention
Beta blockers - Bisoprolol and atenolol
How do bisoprolol and atenolol function
Beta 1 receptors
Reduce HR
Reduce contractility
(reduces O2 demand)
What are the side effect of beta-blockers like atenolol and bisoprolol
Tiredness, nightmares
Bradycardia
Erectile dysfunction
Cold hands and feet
What are the contraindications for beta blockers
- Asthma
- Prinzmetal’s angina
- Severe heart block
- Excess bradycardia
Why do we give patients nitrates
- Venodilators
- Reduces venous return + preload on the heart
- Reduce work done by the heart and O2 demand
Dilate coronary arteries and antagonise spasms
Why are calcium channel antagonists given
Primary arterodilatoes
Reduces BP in systemic arteries
Reduction of after load on heart
Less energy required to produce same CO
Reduced Work Done and O2 demands
Antagonise spasms of coronary arteries by dilating them
Name two second line abtianginal drugs
Nicorandil + Ivabridine
How does Nicorandil work
Veno and artero dilatory properties
How does Ivabridine work
Slows sinus rhythm
Why would anti platelets be given to a patient with angina
- Aspirin is a cycle-oxygenase inhibitor
- Decreased prostaglandin synthesis incl. thromboxane
- Decreased platelet aggregation
Side-effect of aspirin
Gastric ulceration
Alternatives to aspirin
P2Y12 inhibitors (Clopidrgrel, prasugrel, ticagrel)
Why are statins given to patients with angina
Reduce LDL cholesterol
Why would we carry out revascularisation
- Restore patent coronary arteries and increase flow
When would we carry out revascularisation
When medication fails or when high risk disease is identified
How would we carry out revascularisation
PCI (stenting) or Coronary artery bypass graft surgery
Pros of PCI vs CABG
- Less invasive
- Covenient
- Repeatable
- Acceptable
Cons of PCI vs CABG
- Risk stent thrombosis
- Risk restenosis
- Can’t deal with complex disease
- Dual anti platelet therapy
Pros of CABG vs PCI
- Prognosis
2. Deals with complex diseases
Cons of CABG vs PCI
- Invasive
- Risk of stroke
- Length of stay
- Time for recovery
