CCT (ASQ) common mistakes
CCT · Understand the traps and how to avoid them.
Confusing the roles of the right and left coronary arteries when tracing which vessels supply the SA node, AV node, and lateral wall of the left ventricle, and answering from a vague memory of 'the left side supplies the left side'.
Candidates memorise vessel names as a list without attaching each to a territory, so under time pressure the territories blur and dominance questions defeat them.
What to do instead
Build a territory table you can reproduce from blank paper: RCA (SA node in ~60% of people, AV node in ~90%, inferior wall), LAD (anterior wall, anterior two-thirds of septum, apex), circumflex (lateral wall, SA node in ~40%). Redraw it daily until the percentages and territories are automatic.
Describing the cardiac cycle in the wrong sequence, for example placing ventricular repolarisation before atrial systole or treating 'diastole' as a single undivided phase.
Textbook diagrams are read passively rather than rehearsed, so the mechanical events are recognised when seen but cannot be generated from memory.
What to do instead
Practise narrating the cycle aloud in strict order with pressure and valve states attached to each step (isovolumetric contraction, rapid ejection, reduced ejection, isovolumetric relaxation, rapid filling, diastasis, atrial systole), then self-test by writing it with the labels hidden.
Calculating heart rate from an ECG strip using the wrong method for the rhythm present, e.g. applying the 300/large-box rule to an irregular rhythm or counting small boxes incorrectly.
Candidates learn one formula and apply it universally; the 300 rule is quick and satisfying, so it becomes the default even when the rhythm is irregular.
What to do instead
Before calculating, classify the rhythm as regular or irregular. For regular rhythms use 300 divided by large boxes or 1500 divided by small boxes; for irregular rhythms count QRS complexes in a 6-second strip and multiply by 10, and state the method in your working.
Misidentifying the origin of a wide-complex tachycardia, labelling every broad-complex rhythm as ventricular tachycardia without checking for capture beats, fusion beats, or a preceding P wave relationship.
Pattern-recognition shortcuts replace systematic analysis, and candidates fear missing a dangerous rhythm so they over-call VT.
What to do instead
Use a fixed checklist for every wide-complex rhythm: rate, regularity, QRS width, AV dissociation, capture and fusion beats, concordance, and axis. Record each criterion before committing to an interpretation.
Measuring the QT interval from the wrong onset or including the U wave, and failing to correct for rate when the question asks for QTc.
The T-wave end is genuinely ambiguous on many traces, and candidates measure to the most visually obvious point rather than applying a consistent rule.
What to do instead
Measure from the earliest QRS onset to where the T wave returns to baseline, excluding any separate U wave. Always report both QT and QTc, and use the correction formula the question specifies rather than substituting your preferred one.
Confusing the indications and contraindications of exercise stress testing versus pharmacological stress imaging, and selecting the wrong modality for a patient who cannot exercise.
Candidates learn each test in isolation and never build a decision rule linking patient characteristics to test choice.
What to do instead
Create a two-column comparison for each test covering what it measures, sensitivity and specificity, absolute contraindications, and inability-to-exercise scenarios. Rehearse the rule: if the patient cannot achieve adequate workload, choose pharmacological stress with imaging.
Misreading a cardiac output or shunt calculation by mixing units, e.g. using oxygen content in mL/L where mL/dL is required, or omitting the Fick principle constants.
Haemodynamic calculations are practised rarely and the unit conversions are assumed rather than written down.
What to do instead
Write every calculation as a labelled equation with units attached to each term before substituting numbers, and carry the units through to the answer. Practise one full Fick calculation and one shunt calculation from scratch each study session.
Placing ECG limb electrodes on the wrong limbs or in the wrong anatomical position, producing a technically abnormal tracing that the candidate then interprets as pathology.
Electrode placement is treated as a trivial task learned once, and candidates do not recognise the characteristic patterns that misplacement produces.
What to do instead
Learn the signature of each misplacement (e.g. reversed arm leads producing inverted P and a negative aVR) and check for them before interpreting. Verbally confirm electrode sites on the patient before recording, and treat any unexpected axis or negative aVR as a placement problem until proven otherwise.
Ignoring artefact and baseline wander, or failing to check calibration and paper speed before interpreting a tracing.
Candidates focus on the rhythm and skip the quality-control steps, so they interpret a 10 mm/mV versus 5 mm/mV difference as a voltage abnormality.
What to do instead
Adopt a mandatory pre-interpretation check: confirm 25 mm/s and 10 mm/mV calibration marks, note baseline wander and muscle artefact, and repeat the recording after correcting the cause before drawing any conclusion.
Failing to apply patient safety checks before or during a cardiac diagnostic procedure, such as not confirming consent, allergy status, or the presence of a pacemaker or ICD before a test.
Candidates treat safety questions as common sense and answer from general instinct rather than the specific procedural checklist the exam expects.
What to do instead
Memorise a pre-procedure checklist for each test (identity and consent, allergies, implanted devices and their MRI compatibility, anticoagulation status, resuscitation equipment availability) and answer safety questions by naming the specific check rather than a general statement about being careful.