Electrocardiogram (ECG)

Key uses

•    Arrhythmias

•    Ischaemia and infarction

•    Electrolyte disorders

•    Conduction abnormalities

Ischaemia and infarction

•    ST elevation → transmural infarction (STEMI)

•    ST depression and/or T wave inversion → subendocardial ischaemia, NSTEMI, unstable angina

•    New LBBB + chest pain → treat as STEMI equivalent

QT interval

•    Prolonged QTc (>450 ms in men, >470 ms in women) → risk of torsades de pointes

•    Causes: hypocalcaemia, hypokalaemia, hypomagnesaemia, drugs (antiarrhythmics, antipsychotics)

Ambulatory ECG (Holter monitoring)

•    Continuous 24–72 h monitoring

•    Indications:

o    Paroxysmal arrhythmias (e.g., AF, SVT, bradycardia)

o    Correlation with palpitations or syncope

Echocardiography

Transthoracic echo (TTE)

•    First-line for most cardiac structural assessments

•    Assess:

o    Valve disease (stenosis/regurgitation)

o    LV function (EF)

o    Regional wall motion abnormalities (ischaemia)

o    Pericardial effusion and tamponade

Transoesophageal echo (TOE)

•    Better resolution of posterior structures

•    Indications:

o    Infective endocarditis (especially prosthetic valves)

o    Left atrial thrombus (pre-cardioversion)

o    Aortic dissection assessment (ascending aorta)

Stress testing

Exercise ECG

•    Detects inducible ischaemia in stable angina

•    Positive: typical chest pain + ST depression ≥1 mm

Pharmacological stress

•    Agents: dobutamine (increases contractility), adenosine (vasodilation)

•    Indicated in patients unable to exercise

Cardiac catheterisation

Coronary angiography

•    Gold standard for coronary artery disease (CAD) assessment

•    Indications:

o    ACS

o    High-risk angina

o    Positive non-invasive stress test

Complications

•    Vascular access bleeding/haematoma

•    MI, arrhythmias

•    Stroke

•    Contrast-induced nephropathy (more common with CKD)

CT coronary angiography

•    Non-invasive anatomical assessment

•    Indicated in low-intermediate risk stable chest pain

Cardiac MRI

•    Soft tissue detail

•    Indications:

o    Cardiomyopathy (e.g., hypertrophic, dilated, infiltrative)

o    Myocarditis (late gadolinium enhancement)

o    Cardiac masses

NT-proBNP

•    Marker of ventricular wall stress

•    Raised in heart failure

•    Can be elevated in:

o    Ageing

o    Renal failure

o    AF

•    Low levels (<125 pg/mL in non-acute, <300 pg/mL in acute) → HF unlikely

Cardiac biomarkers

Troponin I/T

•    High sensitivity; rise within 3–12 h; peak ~24 h

•    Causes of elevation:

o    MI (type 1 = atherothrombotic; type 2 = supply-demand imbalance)

o    Myocarditis

o    PE (RV strain)

o    Severe sepsis

o    CKD (chronic mild elevation)

Extra Revision Pearls

•    Persistent ST elevation weeks after MI → ventricular aneurysm (not re-infarction)

•    New T wave inversion post-MI → reperfusion marker

•    QT prolongation clue → low Mg²⁺, K⁺, Ca²⁺ or drugs

•    BNP/NT-proBNP not reliable if on ARNI (e.g., sacubitril) — prefer NT-proBNP

•    Cardiac MRI is gold standard for myocarditis diagnosis

•    TOE preferred for left atrial thrombus before DC cardioversion