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]

SAQ 2 — Cardiac MRI Interpretation: Viability and Cardiomyopathy Phenotyping (15 marks, 20 minutes)

Prompt: A 60-year-old man presents with progressive exertional dyspnoea over 6 months. Echocardiography shows a dilated left ventricle with ejection fraction of 30 percent and global hypokinesia, with more severe akinesia in the anterior and apical segments. Coronary angiography shows a 90 percent stenosis in the proximal LAD and chronic total occlusion of the right coronary artery with collaterals. Cardiac MRI with late gadolinium enhancement shows transmural LGE (over 75 percent of wall thickness) in the LAD territory from base to apex, and subendocardial LGE (25 percent of wall thickness) in the inferior wall. T2-weighted imaging shows no oedema. Native T1 mapping is normal. [1]

Task: Interpret the MRI findings, assess myocardial viability in each territory, and outline how this guides the revascularisation strategy. [1]

Model Answer

Interpretation of the LGE pattern (4 marks): [1]

The LGE pattern is ischaemic — both areas of enhancement are subendocardial-based and conform to coronary territories. The anterior and apical transmural LGE conforms to the LAD territory, and the inferior subendocardial LGE conforms to the RCA territory. There is no midwall, epicardial, or diffuse pattern to suggest a non-ischaemic cardiomyopathy. The T2 imaging showing no oedema excludes superimposed acute myocarditis or acute infarction. The normal native T1 excludes diffuse infiltration (e.g., amyloidosis). This is chronic ischaemic cardiomyopathy with established infarction. [1]

Viability assessment (5 marks): [1]

The principle is that the transmural extent of LGE predicts recovery. Segments with less than 25 percent transmural LGE are viable and likely to recover after revascularisation. Segments with over 50 percent LGE (and especially over 75 percent) are predominantly scar and unlikely to recover function. [1]

Implication for revascularisation strategy (4 marks): [1]

The revascularisation strategy should be guided by viability: [1]

• LAD territory (proximal LAD 90 percent stenosis): The downstream myocardium (anterior wall and apex) is non-viable (transmural scar). Revascularising the LAD will NOT improve regional function because there is no living myocardium to recover. However, revascularising a subtotally occluded LAD may still be considered for prognostic benefit (reducing the risk of future complete occlusion and arrhythmia) and to prevent further remodelling, but the functional benefit is minimal.
• RCA territory (chronic total occlusion): The inferior wall is viable (25 percent subendocardial LGE). Revascularising the RCA (either PCI of the CTO or CABG) has a high probability of improving inferior wall function and contributing to overall LV recovery. This is the territory where revascularisation will make the most functional difference. [1]

The integrated strategy: pursue revascularisation of the RCA territory (CTO PCI or CABG bypass grafting) for viability-driven functional recovery. The LAD may be stented for prognostic reasons but is unlikely to yield functional improvement. If CABG is chosen, the surgeon would graft both vessels; if PCI, the CTO should be attempted if the likelihood of success is reasonable. [1]

Prognostic and adjunctive considerations (2 marks): [1]

• Initiate or optimise guideline-directed medical therapy for HFrEF: ARNI, beta-blocker, MRA, SGLT2 inhibitor (ESC HF 2021, PMID 33481140).
• Assess for ICD indication: LVEF under 35 percent at least 40 days post-MI and 3 months on optimal medical therapy meets primary prevention criteria.
• Cardiac rehabilitation, smoking cessation, and secondary prevention. [1]