ECG Interpretation — Clinical Case

DCE Long Case

Patient brief (provided to trainee)

Patient: Mr David Chen, 70 years old, retired engineer. ^[1]

Presenting complaint: Two episodes of rest chest pain overnight, each lasting 20 minutes and settling with sublingual glyceryl trinitrate. Now pain-free on the ward. ^[1]

Past history:

• Anterior STEMI 6 years ago — DES to proximal LAD
• Ischaemic cardiomyopathy, last known LVEF 32%
• Hypertension, type 2 diabetes (HbA1c 62), stage 3 CKD (eGFR 44)
• Paroxysmal atrial fibrillation ^[1]

Current medications:

• Aspirin 100 mg, atorvastatin 80 mg, bisoprolol 5 mg, ramipril 5 mg, spironolactone 25 mg, dapagliflozin 10 mg, apixaban 5 mg BD ^[1]

Examination findings (trainee elicits):

• Comfortable at rest at 45 degrees, BP 148/86, SpO₂ 97% on air
• Pulse irregularly irregular at 78/min
• JVP elevated 3 cm; apex displaced to 6th ICS, anterior axillary line, diffuse
• Soft S3 at apex; bilateral basal crackles to mid-zones; trace ankle oedema ^[1]

Investigations:

• ECG (the focus of the case): atrial fibrillation, ventricular rate 78, left axis deviation, QRS 134 ms with LBBB morphology, QTc 440 ms, old Q waves V1–V3, Sokolow-Lyon voltage for LVH with lateral strain
• High-sensitivity troponin: mildly elevated (2.5× upper limit of normal), with a flat trend
• Renal function and electrolytes within his baseline ^[1]

Candidate's structured presentation (model)

Opening statement: ^[1]

"Mr Chen is a 70-year-old retired engineer who presents with two episodes of rest chest pain overnight, now settled. He has a background of ischaemic cardiomyopathy from an anterior STEMI six years ago, with a last-known ejection fraction of 32 per cent, hypertension, type 2 diabetes, stage 3 chronic kidney disease, and paroxysmal atrial fibrillation." ^[1]

"His main problems are:

1. Possible acute coronary syndrome on a background of established ischaemic heart disease — but the ECG is confounded by LBBB
2. Heart failure with reduced ejection fraction — he has signs of mild congestion and an S3
3. Atrial fibrillation, now apparently persistent
4. Chronic kidney disease and diabetes — cardiorenal and metabolic overlap
5. Multimorbidity and polypharmacy requiring careful reconciliation"* ^[1]

ECG interpretation: ^[1]

"His ECG shows atrial fibrillation at a controlled ventricular rate of 78. The axis is leftward, consistent with left anterior fascicular block. The QRS is broad at 134 milliseconds with a left bundle branch block morphology. The QTc is normal at 440 milliseconds. There are old Q waves in V1 to V3 from his prior anterior infarction, and voltage criteria for left ventricular hypertrophy with a lateral strain pattern." ^[1]

"Because he has LBBB, I cannot read ischaemia in the usual way. I apply the Sgarbossa criteria: there is no concordant ST elevation or concordant ST depression in V1 to V3, and no excessively discordant ST elevation, so the score is zero — the ECG does not demonstrate an acute occlusion. I would therefore interpret his presentation as a possible non-occlusion myocardial infarction and rely on the troponin trend, symptoms, and serial ECGs, with echocardiography to look for a new wall-motion abnormality." ^[1]

Management plan: ^[1]

1. Acute coronary syndrome: continue aspirin and apixaban with cardiology input (balance ischaemic and bleeding risk), add or continue a P2Y12 inhibitor, treat as NSTEMI pathway with inpatient angiography given the high-risk features (rest pain, diabetes, CKD, prior PCI). Do NOT stress test.
2. Heart failure: confirm he is on all four GDMT pillars (he is — ARNI would be preferred over ACEi if tolerated), address congestion with loop diuretic, reassess LVEF, assess for ICD/CRT (his QRS is 134 ms — if LBBB morphology, he may qualify for CRT).
3. Atrial fibrillation: rate control, confirm anticoagulation adequacy (apixaban 5 mg BD appropriate for his renal function), consider rhythm control if symptomatic.
4. Cardiorenal-metabolic: continue SGLT2 inhibitor, monitor renal function, diabetic optimisation.
5. Communication and follow-up: medication reconciliation, cardiac rehabilitation, advance care planning appropriate to his HF trajectory. ^[1]

Examiner discussion questions

Q: "How do you decide whether his chest pain is ischaemic given the LBBB?" ^[1]

"LBBB distorts repolarisation and obscures ST analysis, so I use the Sgarbossa criteria to look for an occlusion — concordant ST change or excessively discordant ST elevation. He meets none, so there is no occlusion ECG. I then assess the clinical probability of an ACS: he has rest pain, prior ischaemia, diabetes, CKD and prior PCI — all high-risk features. The mildly elevated troponin with a flat trend is consistent with chronic myocardial injury in heart failure rather than acute infarction, but a rising trend would change that. I would manage him as a possible NSTEMI with inpatient coronary angiography and echocardiography for a new wall-motion abnormality, and avoid functional stress testing." ^[1]

Q: "Would his QRS of 134 ms qualify him for cardiac resynchronisation therapy?" ^[1]

"Current guidelines consider CRT for patients with an LVEF of 35 per cent or less who are in sinus rhythm with a QRS of 130 milliseconds or more, particularly with LBBB morphology. He has the LVEF and the QRS duration, but he is now in atrial fibrillation — CRT benefit in AF is less well established and usually requires AV nodal ablation or strict rate control to ensure a high percentage of biventricular pacing. I would first address his rhythm: if he is to receive CRT, I would consider rhythm control or AV junction ablation to guarantee biventricular capture. I would discuss this with an electrophysiologist." ^[1]

Q: "He is on apixaban and aspirin. Should he continue both?" ^[1]

"After six years from his stent, his aspirin is for secondary prevention and his apixaban is for stroke prevention in AF. Continuing both long-term increases major bleeding without a clear ischaemic benefit in most patients. The standard approach after completing the dual-therapy window following PCI is to stop the aspirin and continue oral anticoagulation alone, unless there is a separate indication for aspirin such as recent stenting. Given his chronic kidney disease and age, I would favour stopping aspirin and continuing apixaban alone, after cardiology discussion." ^[1]