Cardiac imaging and diagnostic investigations
The exam tests whether you select the right test for the question and can extract the number that changes management.
ECG
- Rate 300 divided by large squares; assess axis, PR, QRS, QTc (Bazett), hypertrophy (Sokolow-Lyon, Cornell) and ischaemia.
- Always interpret with clinical context; serial ECGs beat a single tracing.
Echocardiography
- Simpson biplane ejection fraction; diastolic function from E/A, e' and E/e'; TAPSE for RV function; RVSP for pulmonary pressure.
- Global longitudinal strain detects early dysfunction, including cardiotoxicity and amyloidosis.
Stress and anatomical imaging
- Exercise ECG for interpretable tracings and ability to exercise; stress echo, SPECT/PET or stress CMR when the ECG is uninterpretable.
- Coronary CT angiography has a high negative predictive value in low-to-intermediate pretest probability; a calcium score of zero indicates very low risk. CT is also used for TAVR planning and pulmonary embolism.
- Cardiac MR characterises tissue: late gadolinium enhancement in infarction, myocarditis, sarcoid and amyloid; T1/T2 mapping for diffuse disease.
Catheterisation
- Fick and thermodilution cardiac output; shunt calculation from oxygen saturations; FFR/iFR for intermediate lesions; IVUS/OCT for stent planning.
Worked example
A 55-year-old with atypical chest pain and intermediate pretest probability has an Agatston calcium score of zero. The likelihood of obstructive disease is very low, so no further ischaemia testing is needed; manage risk factors instead.
Traps
- Quoting ejection fraction from a poor-quality study or during atrial fibrillation without averaging.
- Using CTCA as a screening test in high pretest probability.
- Reporting a test result without stating how it changes management.