Acute Coronary Syndromes Flashcards
What are the acute coronary syndromes?
- Unstable angina
- NSTEMI
- STEMI
- Sudden cardiac death
What is the unstable angina?
Defined by the absence of biochemical evidence of myocardial damage. It is characterised by specific clinical findings of:
- Prolonged (>20 minutes) angina at rest
- New onset of severe angina
- Angina that is increasing in frequency, longer in duration, or lower in threshold
- Angina that occurs after a recent episode of MI.
What is an NSTEMI?
Non-ST elevated myocardial infarction
MI, but without ST-segment elevation. May have other ECG changes, such as ST-segment depression or T-wave inversion. Will have elevated cardiac biomarkers.
This pathologyically results in a subendocardial infarct - partial thickness infarct
What is a STEMI?
ST elevation myocardial infarction
MI as defined as in acute myocardial infarction, with ST-segment elevation more than 0.1 mV in two or more contiguous leads, and elevated cardiac biomarkers.
Pathologically this is classed by a transmural infarct
What happens phsyiologically within a few minutes of infarction?
All these effects are reversible
Within seconds - Cell switches to anaerobic metabolism -> ATP depletion
<2 minutes - Myocardial contractility decreases -> Heart failure
Within 5 minutes - Myofibrillar relaxation, glycogen depletion, cell and mitochondrial swelling
What happens pathologically after about 20-40 minutes of infarction?
Effects of this stage are irreversible
Myocardial necrosis - Sarcolemmal integrity disrupted, leading to leakage of intacellular macromolecules
What happens phsyiologically 24-48 hours after an infarct has happened?
Macroscopically pale infarct appears
Acute inflammatory reaction begins at the edge of the infarct
After the first 20-40 minutes of infarction, what happens in the follwoing 24 hours from a pathological point of view?
- Early coagulation necrosis
- Oedema and haemorrhage
- Early neutrophil infiltration
What happens pathologically 3-7 days after an infarct?
- Disintegration of dead myofibres
- Dying neutrophils
- Early phagocytosis by infiltrating macrophages
What occurs pathologically after 7-10 days of infarction?
Granulation tissue begins to form at the margins of the infarct
What pathologically occurs 2-8 weeks after infarction?
Increased collagen deposition and decreased cellularity
What happens pathologically after 2 months post infarct?
Dense collagenous scar formation
What is coagulative necrosis?
Characterised by the formation of gelatinous substance in dead tissue in which the architecture of the tissue is still maintained. Coagulation occurs as a result of protein denaturation, causing albumin in proteins to form a firm and opaque state. .
How does infarction occur?
Coronary artery obstruction or rupture
What is the difference between an NSTEMI and Unstable angina?
NSTEMI there are biochemical signs of infarction (troponin rise), whereas in unstable angina there are not
What are modifiable risk factors for ACS?
- Smoking
- Alcohol intake
- Calorie intake
- Sedentary lifestyle
- Diabetes
- Obesity
- Hyperlipidaemia/Dyslipidaemia
What are non-modifiable risk factors for ACS?
- Increasing age
- Sex - male
- FH
- Ethnicity
What are symptoms of an acute coronary syndrome?
- Chest pain - crushing, radiates to jaw, neck and arm, not relieved by rest or GTN
- Dyspnoea
- Diaphoresis
- Nausea
- Palpitations
- Syncope
- Sense of impending doom
What signs may be seen in someone with an acute coronary syndrome?
- Brady/tachycardia
- Signs of HF - Increased JVP, basal creps, 3rd heart sound etc
- Pallor, sweatiness
- 4th heart sound
- Pansystolic murmur
- Late signs - Pericardial rub, Peripheral oedema
What causes a 3rd heart sound?
A dull, low-frequency extra heart sound heard in the rapid filling phase of early diastole. The cadence of the heart sounds in a patient with an S3 is said to be similar to the word ‘Ken-tuck-y’.
An abrupt limitation of left ventricular inflow during early diastole causes vibration of the entire heart and its blood contents, resulting in the S3. In heart failure with systolic dysfunction there is elevated atrial pressure. When the mitral valve opens there is rapid filling down the pressure gradient into the stiffened dysfunctional ventricle.
What causes a 4th heart sound?
An S4 is typically found in conditions that cause a decrease in compliance of the left ventricle or diastolic dysfunction. Any condition causing stiffening of the left ventricle may cause an S4.
Forceful contraction of the atrium pushes blood into a non-compliant left ventricle. The sudden deceleration of blood against the stiff ventricular wall produces a low-frequency vibration, recognised as the fourth heart sound.
Why might you get a pansystolic murmur in an MI?
Papillary muscle rupture or a VSD
What patient groups may present without chest pain but have a MI?
Reduced sensation in mediastinal area
- Elderly
- Diabetics
How might an elderly or diabetic patient present with an MI?
- Syncope
- Pulmonary oedema
- Epigastric pain and vomiting
- Acute confusional state
- Stroke
- Diabetic hyperglycaemia
If you suspected an ACS, what investigations would you do?
- 12 lead ECG, then continuous cardiac monitoring
- Bloods - FBC, U+E’s, LFTs, CRP, Glucose, Troponin, magnesium, phosphate, lipid profile, CK-MB, myoglobin
- CXR
What are the features of NSTEMI on an ECG?
Horizontal/downsloping ST depression >0.5 mm in > 2 leads
- ST depression ≥ 1 mm is more specific and conveys a worse prognosis.
- ST depression ≥ 2 mm in ≥ 3 leads associated with a high prob. of NSTEMI
T wave inversion/flattening at least 1mm deep in > 2 leads with dominant R-waves
What are the features of a STEMI on ECG?
- ST elevation in >/=2 adjacent chest leads of >/=0.2mV in leads V1, 2 or 3
- ST elevation in >/= 2 adjacent limb leads of >/=0.1 mV in other leads
- Pathological Q waves
- T-wave inversion
- New LBBB/RBBB
What would indicate a septal infarct?
Maximal ST elevation in V1-2
What would indicate an anterior infract on ECG?
Maximal ST elevation ST elevation in V2-V5
What would indicate an anterioseptal infarct on ECG?
Maximal ST elevation in leads V1-4
What would indicate an anterolateral infarct on ECG?
Maximal ST elevation in V3-6, 1 and aVL
Why when lookign at cardiac enzymes would you take an immediate level then take a level 12 hours later?
It can take 10–12 hours after a heart attack for troponin levels to rise, so 2 troponin tests are carried out (10–12 hours apart) to see if there is a change in troponin level
What would indicate purely lateral infarct on ECG?
Maximal ST elevation in I and aVL