Angina and ACS Flashcards
What is the most common site of infarction
Proximal LAD
What is meant by coronary artery dominance?
The dominant coronary artery is that which gives rise to the posterior descending artery and thereby supplies the posterior septum
80% of people exhibit RCA dominance
20% exhibit circumflex dominance
What three conditions comprise acute coronary syndrome (ACS)
- STEMI
- NSTEMI
- Unstable angina
What are the characteristics of classical/exertional angina?
Constricting discomfort in the chest, arms, neck and jaw
Provoked by physical exertion, especially after meals and in cold windy weather, or by anger or excitement
Relieved (usually within minutes) with rest or GTN
What is meant by the term stable angina?
Angina is stable when it is not a new symptom and there is no change in the frequency or severity of the attacks
What is meant by the term unstable angina?
Angina of recent onset (<24 hr) or a deterioration in a previous stable angina with symptoms frequently occuring at rest (i.e. ACS)
What is variant (Prinzmental’s angina)?
Angina that occurs without provocation, usually at rest, as a result of coronary artery spasm. More common in women
Describe the physiological process of atheromatous formation
Damage to vessel wall is caused by mechanical stresses (e.g. from morbid hypertension), biochemical abnormalities (e.g. elevated LDL, diabetes mellitus), immunological factors (e.g. free radicals from smoking) or inflammation. This initial endothelial injury or dysfunction triggers the development of atherosclerosis. There is increased permeability to and accumulation of oxidized lipoproteins, which are taken up by macrophages at focal sites within the endothelium to produce lipid-laden foam cells. Macroscopically these lesions are seen as flat yellow lines on the endothelium called ‘fatty streaks’. Release of cytokines by the damaged endothelium promotes further platelet adhesion and accumulation of macrophages as well as smooth muscle proliferation. This leads to formation of an atheroma
How much of the artery is occluded in stable angina?
70%
How much of the artery is occluded in unstable angina?
90%
What is the most common cause of angina?
Myocardial ischaemia due to atheroma
What are the major causes of ischaemia?
Mechanical obstruction: Atheroma Thrombosis Spasm Embolus
Decrease in the flow of oxygenated blood to the mycoadrium due to anaemia
Increased demand for oxygen due to increase cardiac output e.g. hyperthyroid or myocardial hypertrophy (due to aortic stenosis or hypertension)
How are patients with stable angina managed? (N.B 5 drug types used)
- Modify risk factors: stop smoking, encourage exercise, encourage weight loss, control hypertension, control diabetes, give statins if cholesterol is raised
- Aspirin (75-150mg/24 hr)
- Beta blocker (e.g. atenolol 50-100mg/24 hours) unless contraindicated e.g. COPD, asthma
- Nitrates
For symptom relief GTN spray
For prophylaxis oral isosobide mononitrate (N.B. 8hr nitrate free period to prevent tolerance) - Calcium channel blocker (useful if beta-blockers are contraindicated)
- If still not controlled, try a potassium channel activator e.g. nicorandil
Blockage of which artery causes anterior MI? What leads are affected on the ECG?
LAD
ST elevation in V1-V4
Blockage of which artery causes lateral MI? What leads are effected on the ECG?
Circumflex
ST elevation in I, aVL, V5 and V6
Blockage of which artery causes posterior MI? Which leads are effected on the ECG?
RCA or circumflex
Reciprocal ST depression in V1-V3
(ST elevation in V7-V9)
Blockage of which coronary artery causes inferior MI? Which leads are effected on the ECG?
RCA or circumflex
ST elevation in II, III, aVF
What is the most common complication(s) of an anterior MI?
1, Cardiac tampenade
2. Mitral regurgitation
What is the most common complication(s) of a posterior MI?
Arrhythmia
What is Dresner’s syndrome?
Pericarditis following MI
What are the non-modifiable risk factors of ACS?
- Age
- Male gender
- Family history (MI in first degree relative)
- Ethnicity
What are the modifiable risk factors of ACS?
- smoking
- hypertension
- DM
- hyperlipidemia
- obesity
- sedentary lifestyle
- cocaine use