Cardiac Investigations — Written Clinical Reasoning

SAQ 1 — Stable Chest Pain Investigation Pathway (20 marks, 30 minutes)

Prompt: Outline your integrated investigation and management plan for this patient, including the rationale for your choice of cardiac imaging or stress test, the information each test provides, and how the results would direct your management. Justify each decision with reference to evidence and guidelines. ^[1]

Model Answer

Problem list (3 marks): ^[1]

1. Stable chest pain with features suggestive of angina — exertional, central, relieved by rest, in a high-risk patient. The presentation meets the definition of typical angina (constricting discomfort in the chest, provoked by exertion, relieved by rest or glyceryl trinitrate within minutes).
2. High pre-test probability of coronary artery disease — estimated at over 50 percent based on the 2019 ESC CCS guidelines clinical likelihood model (PMID 31504425), factoring in age, sex, risk factors (diabetes, smoking, hypertension, dyslipidaemia, family history), and the typical nature of the symptoms.
3. ECG uninterpretable for exercise testing — the left ventricular hypertrophy with strain pattern (resting ST-T changes in the lateral leads) renders exercise ECG uninterpretable, as baseline ST changes preclude reliable detection of ischaemic change during exercise. ^[1]

Choice of investigation — the key decision (6 marks): ^[1]

The correct investigation is coronary CT angiography as the first-line test or, given the high pre-test probability, invasive coronary angiography with consideration of functional assessment (FFR). ^[1]

The detailed reasoning: ^[1]

• Why NOT exercise ECG: This patient has resting ST-T changes from LVH with strain pattern. Exercise ECG requires an interpretable resting ECG. The baseline ST changes confound ischaemic interpretation. Exercise ECG also has only approximately 70 percent diagnostic accuracy (sensitivity 68 percent, specificity 77 percent). It is a lower-tier test.
• Why CT coronary angiography is reasonable: The 2019 ESC CCS guidelines (PMID 31504425) recommend CTCA as the first-line anatomical test in patients with low-to-intermediate pre-test probability (approximately 15 to 50 percent). CTCA has a negative predictive value above 95 percent for obstructive CAD. The SCOT-HEART trial (PMID 30145934) demonstrated that CTCA improved diagnostic certainty, increased preventive therapy, and reduced fatal and non-fatal MI by 41 percent over 5 years.
• Why invasive coronary angiography may be preferred: This patient has a high pre-test probability (over 50 percent). In high-risk patients, the ESC guidelines favour either functional imaging or direct invasive angiography because the probability of finding obstructive disease is high and CTCA may be less efficient (a positive result still requires angiography for definitive treatment). Additionally, heavy calcification in a high-risk patient may degrade CTCA image quality.
• The integrated approach: CTCA to define anatomy is reasonable; if it shows obstructive disease, proceed to invasive angiography with FFR for physiological assessment before PCI. Alternatively, stress imaging (stress echo or myocardial perfusion imaging) to demonstrate ischaemia first, then invasive angiography if positive. ^[1]

Investigation plan (5 marks): ^[1]

Management based on results (4 marks): ^[1]

• If CTCA or angiography shows no obstructive CAD: Diagnose non-cardiac chest pain or microvascular angina; institute aggressive risk factor modification (statin to target LDL under 1.4 mmol/L, blood pressure control, diabetes management, smoking cessation). Consider microvascular angina (coronary flow reserve assessment) if symptoms persist.
• If obstructive CAD found (over 50 percent stenosis) with positive FFR (under 0.80): Optimal medical therapy as baseline for all patients (antiplatelet, statin, ACE inhibitor or ARB, beta-blocker if symptomatic, GTN). Revascularisation (PCI or CABG) for symptom relief and prognostic benefit in high-risk anatomy (left main, proximal LAD, multivessel disease with reduced LV function). The ISCHEMIA trial (PMID 32227755) supports an initial conservative strategy for many stable patients — invasive management does not reduce death or MI compared with optimal medical therapy, though it improves symptom control.
• Risk factor modification in all cases: Smoking cessation (single most important modifiable risk factor), statin therapy, blood pressure control, glycaemic optimisation, cardiac rehabilitation. ^[1]

Communication and follow-up (2 marks): ^[1]

• Explain the rationale for the chosen test and what the results mean in plain language.
• Arrange follow-up at 4 to 6 weeks to review results, adjust medical therapy, and reinforce lifestyle modification.
• Safety-netting: advise the patient to call an ambulance if chest pain occurs at rest, lasts more than 10 minutes, or is not relieved by GTN — these features suggest unstable angina or MI. ^[1]