Angina Flashcards
What is Angina?
Acute/chronic ischaemic heart disease characterised by transient chest pain due to decreased blood flow to the heart as a result of an imbalance of myocardial supply and demand
What is the underlying pathology of SCAD?
Reversible mismatch between myocardial supply and demand leading to reduced blood flow to the heart.
What are the two clinical subtypes?
- Angina with obstructive CAD
- Angina without obstructive CAD
Describe Angina with obstructive CAD.
- Partial obstruction of coronary artery by atherosclerotic plaque
- Chest pain on exertion
- ST-segment depression
E.g. Classic/Stable Angina
Describe Angina without obstructive CAD.
- At rest/at night and during exercise
- Focal or diffuse spontaneous coronary artery spasm.
- ST-segment elevation
E.g. Variant/ microvascular
Describe the CCS classification of Angina.
Class I - doesn’t cause angina
Class II - slight limitation
Class III - marked limitation
Class IV - unable to carry out physical activities and angina present at rest
Describe subendocardial ischemia.
- Only penetrates through 1st layer to the heart muscle
- Causes ST segment depression.
- The natural flow of current is to flow towards the septum, in this case the current is going opposite direction - causing an ST segment depression.
Describe Transmural ischemia.
- Penetrates completely through the heart muscle
- Causes ST segment elevation due to the fact that the current is moving towards the septum.
- The normal flow of the current is to flow towards the septum, in transmural ischemia this current is added on.
What are the symptoms of Angina?
Breathlessness, dizziness, chest pain that eases at rest, clammy/cold, nausea/vomiting, radiation to neck ,upper arms/ lower jaw
List and describe the pathology of the clinical features on SCAD.
Breathlessness and dizziness due to ischaemia induced LV dysfunction
Metabolic lactate production due to anaerobic metabolism
ECG - ST-segment depression or elevation
What is Classic angina?
- Partial obstruction of coronary artery by atherosclerotic plaque
- Increase myocardial demand
- Cheat pain on execration
- segment depression
What is Variant angina?
- Spontaneous, transient coronary artery spasm due to increase vasoconstriction
- Decreased myocardial supply
- Chest pain during sleep and rest
- ST-segment elevation
What is microvascular angina (unstable)?
- Primary structural/functional dysfunction to small coronary blood vessels.
- Decreased myocardial supply
- Chest pain at at rest and during exercise
- ST-segment depression
What are the triggers of angina?
- exercise/stress
- heavy meals
- exposure to cold
If a patient has angina what are some lifestyle changes would you recommend?
- Increase physical activity min 30mins a day
- Lose weight if needed
- Smoking cessation
- Alcohol moderation
- Healthy diet - low salts and fats
The revascularisation to restore blood flow in the coronary artery by increasing myocardial supply can be achieved by..
- Percutaneous coronary intervention (PCI) - balloon angioplasty, coronary stenting
- Coronary artery bypass grafting (CABG)
Describe the NICE pathway of treating angina.
- Treat acute episodes with GTN spray
- 1st line - BB or CCB e.g. atenolol or Verapamil
- Add dihydropyridine CCB e.g. amlodipine
- Switch to long acting nitrate e.g. ISDN OR miscellaneous agent such ivabradine, ranolazine, nicorandil
Describe the mechanism of action of 1st line treatment of angina
BBs
- Atenolol antagonises the effects of adrenaline and noradrenaline at B-adrenoceptors
- Decreasing HF, BP and contractility which decreases myocardial demand
- Increased diastolic filling time increases myocardial perfusion
- Anti-arrhythmic activity increases electrical stability
What are the side effects of BBs?
Fatigue
Headaches
sleep disturbnaces
cold hands and feet
bronchoconstriction
sexual dysfunction in males
Describe the mechanism of action of anti anginal drug Dihydropyridine CCBs
- Inhibit Ca+ influx into voltage gated channels into arterioles which leads to arteriole dilation and vasodilation decreasing SVR
- Coronary dilation increases blood flow to heart preventing/reversing spasm and decrease HR, BP and contractility which decrease myocardial demand
What are the side effects of dihydropyridine CCBs?
- swollen ankles
- flushing
- headaches
- dizziness
Describe the vascular effects of CCBs
Block of Ca influx into arterioles leading to arteriolar dilation
- Peripheral vasodilation resulting in decreased SVR leading to decreased arterial BP.
- Coronary dilation which leads to increased coronary blood flow reversal/prevention of spasm
Describe the Cardiac effects of the CCBs phenylalkyamines (verapamil) and Benzothiazepines (diltaizem)
- Block of Ca influx into cardiac muscle cells leading to decreases cardiac contractility.
- Block of Ca influx into nodal and conducting cells leading to decreased HR.
Describe the mechanism of action of anti anginal drug - Long acting nitrate
- ISDN/ISMN directly acts on blood vessels causing vasorelaxation and vasodilation to decrease SVR and increase blood flow
- venodilation decreases preload and myocardial demand
- arterial dilation decrease preload and myocardial oxygen demand
- coronary vasodilation increases blood flow and prevents/reverse spasm
What are the side effects of long acting nitrate?
flushing
throbbing headaches
postural hypotension
reflex tachycardia
Describe the mechanism of action of anti anginal drug - miscellaneous
Nicorandil - venodilation and arterial dilation decreases preload and after load which decreases myocardial demand
Ivabradine - inhibits If which decreases HR and myocardial demand
Ranolazine - inhibits INa having anti-ischaemic effects
Define modified release drug therapy.
delivery of drug to a target with delayed effect after administration
Why should we avoid MR formulations in nitrate therapy? Describe how tolerance can be overcome.
Avoid SR formulations as it exposes the body to nitrates for longer, speeding up depletion of thiol (-SH) groups. This leads to nitrate tolerance.
How would you counsel a patient taking nitrates?
begin with small dose then establish dose threshold. Have nitrate free interval by splitting dose e.g. 8am and 2pm
