Myocardial Infarction

Question 1

Non-ST-elevation acute coronary syndrome (NSTEACS):

What are the two main ECG patterns?

Answer 1

ST segment depression
T wave flattening or inversion

(Ref:Lifeinthefastlane)

Question 2

What are the patterns of ST segment?

Answer 2

ST depression can be
1/ upslopinge
2/ downsloping
3/ horizontal

Horizontal or downsloping ST depression ≥ 0.5 mm at the J-point in ≥ 2 contiguous leads indicates myocardial ischaemia (according to the 2007 Task Force Criteria).

ST depression ≥ 1 mm is more specific and conveys a worse prognosis.

ST depression ≥ 2 mm in ≥ 3 leads is associated with a high probability of NSTEMI and predicts significant mortality (35% mortality at 30 days).

Upsloping ST depression is non-specific for myocardial ischaemia.

(Ref:Lifeinthefastlane)

Question 3

Which leads does subendocardial ischemia present as?

Answer 3

ST depression in leads I, II, V4-6& a variable number of additional leads.

Question 4

What does a pattern of widespread ST depression plus ST elevation in aVR > 1 mm is suggestive of?

Answer 4

Left main coronary artery occlusion

Ref:Lifeinthefastlane

Question 5

Differential dx of chest pain

Answer 5

> Ischaemic CVD causes 
ACS (e.g. acute myocardial infarction, unstable angina)
Stable angina
Severe aortic stenosis
Tachyarrhythmia (atrial or ventricular)

> Non-ischaemic cardiovascular causes of chest pain
Aortic dissection
aortic aneurysm
Pulmonary embolism
Pericarditis and myocarditis
Gastrointestinal causes (e.g. gastro-oesophageal reflux, oesophageal spasm, peptic ulcer,
pancreatitis, biliary disease)

> Non CVD causes
Musculoskeletal causes (e.g. costochondritis, cervical radiculopathy, fibrositis)
Pulmonary (e.g. pneumonia, pleuritis, pneumothorax)
Other aetiologies (e.g. sickle cell crisis, herpes zoster)

(Ref: Heart foundation, management of acute coronary syndromes 2016)

Question 6

Causes of Elevated Troponin

Ref: Heart foundation, management of acute coronary syndromes 2016

Answer 6

1) Cardiac:
Trauma: Cardiac contusion, surgery, ablation, pacing, frequent defibrillator shocks

Congestive heart failure — acute and chronic

Coronary vasculitis, e.g. SLE, Kawasaki syndrome

Aortic dissection

Aortic valve disease

Hypertrophic cardiomyopathy

Tachy- or bradyarrhythmias, or heart block

Stress cardiomyopathy (Takotsubo cardiomyopathy)

2) Pulmonary
Pulmonary embolism
severe pulmonary hypertension

3) Renal failure

4) Acute neurological disease
stroke or subarachnoid haemorrhage

5) Infiltrative diseases, e.g. amyloidosis, haemochromatosis, sarcoidosis, and scleroderma
Inflammatory diseases, e.g. myocarditis or myocardial extension of endo-/pericarditis

6) Drug toxicity or toxins e.g. anthracyclines, CO poisoning
7) Critically ill patients, especially with respiratory failure or sepsis
8) Hypoxia
9) Burns, especially if affecting > 30% of body surface area

Question 7

Complications of AMI

Answer 7

cardiogenic shock
Left ventricular Failure / Cardiac failure
Right Ventricular Infarct
Pericarditis
Arrhythmias (e.g. bradycardia with inferior AMI)
complications of therapy, e.g. haemorrhage, coronary artery dissection, stent thrombosis, surgical complication
acute mitral regurgitation
thromboembolism

(ref: lifeinthefastlane)

Question 8

Indications for reperfusion therapy in a STEMI

Answer 8

Chest pain or associated sx for >20mins
nil contraindictions for reperfusion therapy
ST elevation or new BBB
presents within 12 hrs of chest pain

(ref:ETG)

Question 9

Absolute Contraindications to reperfusion therapy

Ref ETG

Answer 9

1/ Risk of bleeding
Active bleeding or bleeding tendency
Head/facial trauma within 3/12 (sig)
Aortic dissection suspected

2/ Risk of intracranial haemorrhage
any prior intracranial haemorrhage
ischaemic stroke within 3 months
known structural cerebral vascular lesion (eg arteriovenous malformation)
known malignant intracranial neoplasm (primary or metastatic)