angina and mi Flashcards
what is chd
Coronary heart diseases (CHD
Atherosclerosis
deposition of fatty plaques in coronary arteries
Atheroma or plaques narrow coronary artery
Rupture can cause further narrowing or block (Thrombosis)
Spasm or constriction similar effect
Rare, may also be associated with atheroma
what is angina?
Angina is a symptom of CHD-
Insufficient oxygen supply to myocardium (ischaemia)
Pain characterised by pain in chest/arm/neck
Also pallor, sweating breathlessness
what are the different types of angina and what do they do?
Stable angina
Predictable pain normally on exertion
Almost always caused by atheroma (plaque)
Unstable angina – considered as acute coronary syndrome
Pain on less and less exertion or at rest
Normally caused by ruptured atheroma
Variant angina
Rare, often artery spasm, normally associated with atheroma
Microvascular angina
Not always due to atheroma, pain often more severe
may not respond to normal treatments for angina
what is MI
Most “Heart attacks” are MI also termed acute coronary syndrome
Caused by coronary artery block by rupture of atheroma and thrombus formation
loss of oxygen area of heart supplied by blocked coronary artery
Prolonged loss of oxygen, irreversible cell death (apoptosis or necrosis)
Various treatments utilised to restore blood supply, prevent re-occlusion and minimise cell death
Atheroma Thrombus embolism*
how can you diagnose MI
Symptoms similar to angina attack (pallor, pain, etc)
Traditionally diagnosis Relied on 3 factors (WHO, 1979)
Patient history of chest pain/angina/unstable angina
ECG changes (see arrhythmia lectures)
Cardiac biomarkers esp. troponin
How can MI be classified?
MI further classified based on the ECG* recording
if ST segment is elevated then termed STEMI
if ST segment normal then classed as NSTEMI
what are the drugs which are used in CHD/ ACS
Many agents are used in CHD
Complex- specific cases described later, local guidelines vary
Acute
Organic nitrates
Prophylactic Organic nitrates Beta blockers or Calcium antagonists Anti-thrombolytic and anti-platelet agents ACE inhibitors
Often surgical interventions are appropriate
E.g. in MI revascularisation (e.g. angioplasty)
what is the MOA of organic nitrates
example
- relieves angina
Cause relaxation of smooth muscle by liberation of nitric oxide (NO) and subsequent generation of cGMP (see hypertension lecture 1 + aorta practical)
Dilate coronary arteries, re-distribute blood to ischaemic region (see later)
Reduce cardiac oxygen consumption
Prevent/relieve coronary spasm
Glyceryl trinitrate (GTN) now commonly used and also longer acting agents such as isosorbide mononitrate
Indications: Angina (inc. unstable angina) Heart failure Extravasation Anal fissure
Mechanism of action:
Releases NO in the blood stream, produces cGMP in smooth muscle causing relaxation
of all blood vessels including collateral arteries
what are the cautions/ need to look out for in organic nitrates?
Prone to development of tolerance
Avoided by having nitrate free periods (normally overnight)
Action is short (as is shelf life)
GTN as spray or sublingual tablet, rapidly absorbed into blood stream – ineffective if swallowed (1st pass metabolism)
Isosorbide longer lasting as absorbed and metabolised more slowly
Side effects include flushing, headache, postural hypotension
what are the use of calcium channel blockers in heart conditions?
examples
side effects
Calcium channel blockers are vasodilators* also reduce heart rate and force of contraction†
Dilate collateral arteries
Reduce oxygen demand of heart, dilate coronary arteries
Diltiazem and Verapamil** commonly used
Dihydropyridines more commonly used in coronary vasospasm, nifedipine to be avoided in angina (reflex tachycardia)
Side effects*
Include postural hypotension (rare), flushing, constipation,
Nifedipine increases mortality following MI
what is the indication and MoA of diltiazem?
Indications:
Prophylaxis and treatment of angina
Hypertension
Mechanism of action:
Blocks L-Type voltage gated Calcium channels in heart (and blood vessels) reduces CO
(decreasen HR and force of contraction). Dilates blood vessels
what is the role of Beta-blockers (β1-adrenoceptor antagonists)
specifically developed for the treatment of angina pectoris
More selective β1 blockers atenolol and bisoprolol Cardioselecctive)
Carvedilol and bisoprolol are preferred only ones to be used in heart failure and post-MI
Reduce oxygen demand of the heart by inhibiting sympathetic drive to heart (β1 adrenoceptors)
Have little effect on resting HR, CO, or arterial pressure
In normal individuals little consequence
Reduce effect of exercise or excitement on the heart
lower sympathetic drive and effect
Thus lower oxygen demand of the heart
Also heart disease have anti- arrhythmic effect*
important following MI increased sympathetic nerve activity has pro-arrhythmic effect on the heart
what is Angioplasty: Percutaneous Coronary Intervention (PCI)
Catheter inserted in femoral or radial arteries
Stents placed in narrowed coronary artery
Stent is expanded increasing arterial diameter and blood flow
Drug eluting stents are preferred in the UK (NG185)
contain drugs that decrease proliferation and prevent restenosis
what is coronary bypass
redirects blood around a section of a blocked or partially blocked artery in your heart. The procedure involves taking a healthy blood vessel from your leg, arm or chest and connecting it below and above the blocked arteries in your heart.
First presentation of chest pain: determining if ACS (NICE CG95)
Check last episode of Chest pain- eliminate non-cardiac pain
Assess for ACS symptoms
Chest pain longer than 15min
Pain associated with nausea vomiting, sweating , breathlessness or haemodynamic instability
New onset or deterioration of stable angina, or reoccurring pain not on exertion longer than 15 min
Refer as an emergency :
ACS suspected
Currently have chest pain or 12 lead ECG abnormal/not available
Refer for same day assessment :
No reasons for emergency
Pain in last 12 hours but now pain free and normal ECG
Last pain episode was 12-72 hours ago
