Acute coronary syndromes Flashcards
What does term acute coronary syndromes mean?
This term covers a spectrum of acute cardiac conditions from unstable angina to varying degrees of evolving myocardial infarction (MI)
What does the spectrum range from (least to most damage to myocardium)
- Unstable angina (No ECG changes)
- Non- Q wave MI (Non-ST-elevation MI)
- Q wave MI (ST elevation MI)
What is the clinical classification of unstable angina?
- Cardiac chest pain at rest
- Cardiac chest pain with crescendo pattern
- New onset angina
How would you diagnose unstable angina?
- history
- ECG
- troponin (no significant rise in unstable angina)
How is ST-elevation MI diagnosed?
can usually be diagnosed on ECG at presentation
How is non-ST-elevation MI diagnosed?
a retrospective diagnosis made after troponin results and sometimes other investigation results are available
What is the J point on ECG?
J point is point of inflection
When is there is a pathological Q wave?
When there is no R wave
What can MI be defined as retrospectively?
non-Q wave or Q-wave MI on the basis of whether new pathological Q waves develop on the ECG as a result of it
What is ST elevation MI and MI associated with left bundle branch block (LBBB) associated with?
larger infarcts unless effectively treated (and therefore more likely to lead to pathological Q wave formation, heart failure or death)
Which type of MI is there a pathological Q wave in?
Q wave MI
- Loss of R wave
Describe features of cardiac chest pain in MI
- unremitting
- usually severe but may be mild or absent
- occurs at rest
- associated with sweating, breathlessness, nausea and/or vomiting
- one third occur in bed at night
What is the consequence of MIs?
Usually causes permanent heart muscle damage although this may not be detectable in small MIs
What are some risk factors of MI?
Higher risk associated with higher age, diabetes, renal failure, left ventricular systolic dysfunction etc
What is the initial management of MI?
- Get in to hospital quickly – 999 call
- Paramedics – if ST elevation, contact primary PCI centre for transfer for emergency coronary angiography
- Take aspirin 300mg immediately
- Pain relief
Describe the hospital management of MI
- Make diagnosis
- Oxygen therapy only if hypoxic
- Pain relief – opiates/ nitrates
- Aspirin +/- platelet P2Y12 inhibitor
- Consider beta-blocker
- Consider other antianginal therapy
- Consider urgent coronary angiography e.g. if troponin elevated or unstable angina refractory to medical therapy
What are causes of ACS?
- Rupture of an atherosclerotic plaque and consequent arterial thrombosis is the cause in the majority of cases
- Myocardial infarction due to atherothrombosis is known as ‘type 1’ myocardial infarction
- Most common
- Other causes of myocardial infarction usually fall under the umbrella of ‘type 2’ myocardial infarction
What are uncommon causes of ACS?
Uncommon causes include coronary vasospasm without plaque rupture, drug abuse,
dissection of the coronary artery, and thoracic aortic depression
- Type 2 MIs
What is troponin?
- A protein complex consisting of troponin C, troponin I and troponin T that regulates actin-myosin contraction
- Highly sensitive markers for cardiac muscle injury
- Not specific for acute coronary syndrome
- May not represent permanent muscle damage
Why is troponin not specific for acute coronary syndrome?
- Positive also in:
- Gram-negative sepsis
- pulmonary embolism
- myocarditis
- heart failure
- tachyarrhythmias
- cytotoxic drugs
- vigorous exercise
What is an agonist released to activate other platelets?
- ADP
- Target for anti platelet drugs
What is the mechanism of aspirin?
Aspirin irreversibly inactivates cyclo-oxygenase 1 so no thromboxane A2
Describe features of P2Y12 inhibitors
- Used in combination with aspirin in management of ACS
- Dual anti platelet therapy (DAPT)
- Increase risk of bleeding so need to exclude serious bleeding prior to administration
What are 3 oral P2Y12 inhibitors?
clopidogrel, prasugrel and ticagrelor
