Ischaemic heart disease Flashcards
Define what is meant by ischaemic heart disease
Known as coronary heart disease
Atherosclerosis within coronary artery which leads to impaired blood flow/thromboembolic occlusion
Coronary blood flow does not match demand leading to ischaemia (restriction of blood supply to tissues)
Describe the clinical features of stable and unstable angina
Stable: atherosclerotic disease, which limits the heart’s ability to respond to increased demand - symptoms on exertion but are relieved by rest.
Unstable: generally due to plaque rupture and the formation of a non-occlusive thromboembolism, or less commonly vasospasm (Prinzmetal angina) - symptoms at rest.
How to diagnose IHD
History
GTN
ECG - ST segment depression
In stable angina, pain is indujced by exercised (+ relieved by rest)
Angiography of coronary arteries
What are the lifestyle changes to manage IHD?
Smoking cessation
Exercise
Diet
Weight
- Coronary artery bypass grafting*
- Angiopasty + stenting*
Describe the mode of action of nitrates in IHD
Via release of NO
Venodilatation, leading to decrease in preload + a reduction in cardiac work
Coronary vasodilatation
Prolonged exposure can reduce effectiveness
- must have nitrate free period (2 doses rather than 3 per day)
- sustained release preparations: given once daily but do not give 24 hr coverage
- patches: leave off for hours
Describe the mode of action of beta-blockers in IHD
1st choice drugs for prevention
-ve inotropic + chronotropic
reduced cardiac work + prevent symptoms
coronary flow occurs during diastole; slowing heart increases diastolic period + increases time for blood flow
anti-arrhymthmic effects decrease MI risk
Describe the mode of action of calcium channel inhibitors in IHD
Rate-limiting: verapamil and diltiazem
DHPs: amlodipine, nifedipine
Vasodilatation and improve coronary blood flow, so preventing symptoms.
Verapamil (and to a lesser extent diltiazem) also have myocardial depressant and bradycardic actions, so reducing cardiac work.
Verapamil also exerts Class IV anti-arrhythmic activity.
Rate-limiting CCBs > DHPs - do not cause reflex tachycardia
What was the outcome of the HOPE trial?
Indicated that ramipril reduced mortality in patients with IHD
Name an example of a potassium channel activator
What is its mode of action?
Nicorandil
Combined NO donor and activator of ATP-sensitive K-channels.
The target is the ATP-sensitive K+-channel (KATP)
What is the mode of action of Ivabradine?
Inhibits If channels (pacemaker Na/K currents in the SAN)
Reduces heart rate
INITIATIVE trial indicated that it was equally effective as atenolol but without beta-blocker side effects
Describe the role of antiplatelet drugs and statins in IHD
Discuss aspirin resistance
Is there any side effects?
e.g. low dose aspirin and/or clopidogrel
Ibuprofen can oppose beneficial actions of aspirin
Clopidogrel = ADP receptor antagonist
- Equally effective
- Used in pts who can not receive aspirin
- can be used with aspirin
- Interacts w/ omeprazole
- Quarter of pts resistant to aspirin - not related to COX*
- At an increased risk of CVD*
- Other anti-platelets do not substitute for aspirin*
Hypercholesterolaemia is a side effect
For symptomatic relief/occasional treatment, a GTN spray/sublingual tablets would be appropriate
State how a patient with stable angina might be managed pharmacologically
Why in refractory disease verapamil cannot be taken with beta-blocker?
In refractory disease…
a beta-blocker plus DHP but NOT with verapamil.
Interaction between beta-blockers and verapamil (and to a less extent diltiazem) substantial risk of fatal aystole.
What should be used for unstable angina?
Low moleular weight heparin
