Black stools for three days, now breathless

The case

76-year-old man. Black stools for three days, now breathless

Patient is on aspirin and rivaroxaban. He is grey and clammy with a heavy sensation across his chest when he walks to the toilet.

On arrival

Heart rate: 118
Blood pressure: 92/58 mmHg

Stage 1 of 3

His ECG is recorded in the resuscitation bay.

Tracing 1 of 2 for the quiz “Black stools for three days, now breathless”. — 12-lead, 25 mm/s Open this tracing in the studio

Bloods

Haemoglobin: 58 g/L

What is the most significant finding on this ECG?

AWidespread ST depression with aVR elevation Correct answer Your answer
BAcute ST elevation myocardial infarction Your answer
CSinus tachycardia with no ischaemic changes Your answer
DAcute pericarditis Your answer

The tracing shows sinus tachycardia at 118 per minute with a narrow QRS. There is ST depression of up to approximately 2.5 mm in leads I, II, aVL, aVF and V3 to V6, with ST elevation of about 2.5 mm in aVR. This pattern of diffuse ST depression with reciprocal aVR elevation reflects global subendocardial ischaemia, not a territorial STEMI, which would show ST elevation in a coronary distribution with reciprocal depression rather than depression everywhere.

What is the most likely cause of these ECG changes?

ASupply-demand mismatch from severe anaemia Correct answer Your answer
BAcute left main coronary occlusion Your answer
CRate-related ST changes only Your answer
DDigoxin effect Your answer

Widespread ST depression with aVR elevation is seen in both left main or severe three-vessel coronary disease and in global supply-demand mismatch. In a patient with a haemoglobin of 58 g/L, the cause is overwhelmingly likely to be the anaemia rather than an acute coronary occlusion. Tachycardia alone can produce mild ST depression, but the degree here, up to 2.5 mm, is far greater than rate-related changes account for.

Stage 2 of 3

The initial high-sensitivity troponin returns elevated. A colleague asks whether this patient needs the catheterisation laboratory.

Bloods

High-sensitivity troponin: 186 ng/L (normal <26)

What is the most appropriate initial management?

ATransfuse and arrange urgent endoscopy Correct answer Your answer
BDual antiplatelet loading and primary PCI Your answer
CTherapeutic anticoagulation for ACS Your answer
DIntravenous glyceryl trinitrate infusion Your answer

The ECG changes and troponin rise reflect demand ischaemia from profound anaemia, not an acute coronary occlusion requiring the catheterisation laboratory. Loading antiplatelets or starting anticoagulation in a patient who is actively bleeding from the gastrointestinal tract would be directly harmful. The priority is restoring oxygen delivery with packed red cells and identifying the bleeding source. Glyceryl trinitrate would only lower an already marginal blood pressure in a patient who is bleeding.

Stage 3 of 3

After transfusion of four units of packed red cells his chest heaviness resolves and his colour improves. A repeat ECG is recorded.

Tracing 2 of 2 for the quiz “Black stools for three days, now breathless”. — 12-lead, 25 mm/s Open this tracing in the studio

Observations

Heart rate: 88

Given the resolved ECG changes and the raised troponin, what is the most accurate diagnosis?

AType 2 myocardial infarction Correct answer Your answer
BType 1 myocardial infarction Your answer
CUnstable angina Your answer
DNon-cardiac troponin elevation Your answer

The repeat ECG shows resolution of the ST depression and the aVR elevation, confirming that the initial changes were driven by oxygen supply-demand mismatch rather than a fixed coronary occlusion. The Fourth Universal Definition of Myocardial Infarction (2018) defines type 2 myocardial infarction as myocardial injury with necrosis where a condition other than acute coronary atherothrombosis causes the supply-demand imbalance.

Diagnosis

Type 2 myocardial infarction from severe anaemia

This tracing shows diffuse subendocardial ischaemia: widespread ST depression in leads I, II, aVL, aVF and V3 to V6, with ST elevation of about 2.5 mm in aVR. The pattern reflects global myocardial oxygen supply-demand mismatch, here driven by profound anaemia from a gastrointestinal bleed.

Although the same pattern can signal left main or three-vessel coronary disease, the priority in a patient with a haemoglobin of 58 g/L and active melaena is restoring oxygen delivery, not loading antiplatelets or anticoagulating.

After stabilisation and treatment of the GI bleed, the patient could be clinically evaluated, optimally in an outpatient setting to determine the likelihood of underlying significant coronary heart disease. Further investigations might be indicated.

The troponin rise with ischaemic changes that resolve on correcting the anaemia is a type 2 myocardial infarction under the Fourth Universal Definition (2018).

References

Thygesen K, Alpert JS, Jaffe AS, et al. Fourth Universal Definition of Myocardial Infarction (2018). Circulation. 2018;138(20):e618-e651.
Collet JP, Thiele H, Barbato E, et al. 2020 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J. 2021;42(14):1289-1367.

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