Hyperkalaemia can mimic STEMI, but true coronary occlusion and hyperkalaemia may coexist. The challenge is to recognise the ECG abnormalities, confirm potassium rapidly, treat life-threatening hyperkalaemia and avoid delaying reperfusion.
The key principle is parallel management: investigate and treat hyperkalaemia while activating the primary PCI pathway when acute coronary occlusion remains a credible diagnosis.
1. Confirm potassium rapidly — do not delay PPCI
In a patient with suspected STEMI and hyperkalaemia:
- Repeat potassium immediately using i-STAT or a venous blood gas analyser. This provides rapid confirmation and reduces delays associated with laboratory processing.
- Review creatinine/eGFR, acid–base status, medications and any history of CKD or dialysis.
- Repeat the 12-lead ECG and maintain continuous cardiac monitoring.
A blood gas potassium result is useful for immediate decision-making but may not identify haemolysis. Send laboratory potassium and renal function in parallel.
Do not wait for laboratory confirmation or potassium normalisation before activating the PPCI pathway. If the initial ECG and clinical presentation strongly suggest coronary occlusion, discuss with the PPCI centre immediately.
2. ECG recognition — STEMI or hyperkalaemia?
Hyperkalaemia can cause striking ST-segment abnormalities, including patterns resembling anterior or inferior STEMI.
| Feature | Hyperkalaemia more likely | Coronary occlusion more likely |
|---|---|---|
| T waves | Diffuse, narrow-based, symmetrical, tented | Regional, broad-based hyperacute T waves |
| ST elevation | May be atypical or widespread | Often anatomically territorial |
| Reciprocal changes | Less typical, but possible | Supportive of STEMI |
| QRS | Widening with increasing severity | Often normal unless conduction disease |
| P waves | Flattened or absent | Usually preserved |
| Serial ECG | May improve rapidly following potassium correction | May persist or evolve with ischaemia |
No single ECG feature reliably distinguishes the two. Severe hyperkalaemia may produce convincing territorial ST elevation and reciprocal changes, while true STEMI may occur in patients with renal failure.
- Pseudo Inferior Myocardial Infarction Pattern Caused by Hyperkalemia – Revista Española de Cardiología (English Edition)
- Pseudoinfarction pattern in a patient with hyperkalemia, diabetic ketoacidosis and normal coronary vessels: a case report | Journal of Medical Case Reports | Springer Nature Link
- Diagnosis and treatment of hyperkalemia | Cleveland Clinic Journal of Medicine
Consider bedside echocardiography for regional wall-motion abnormalities if immediately available, but do not allow it to delay reperfusion. A normal or equivocal examination does not exclude acute coronary occlusion.
3. Treat hyperkalaemia while arranging reperfusion
Immediate potassium treatment
For severe hyperkalaemia or hyperkalaemia with ECG toxicity, follow the local hyperkalaemia protocol:
- IV calcium: 10 mL calcium chloride 10% over 5 minutes, or 30 mL calcium gluconate 10% over 10 minutes, according to access and local policy. Reassess the ECG and repeat calcium if necessary.
- Insulin–glucose: 10 units soluble insulin with 25 g glucose IV, with appropriate glucose monitoring and supplementary glucose when indicated.
- Nebulised salbutamol: 10–20 mg as an adjunct, not monotherapy.
- Potassium removal: Consider sodium zirconium cyclosilicate and urgent renal involvement for severe or refractory hyperkalaemia, particularly in oliguric AKI or dialysis patients.
- Don’t forget to look for and treat urinary retention
Treatment should not be delayed in life-threatening hyperkalaemia while waiting for a repeat laboratory result. Follow potassium and glucose monitoring recommendations after treatment.
Reperfusion timing
1. Aim for PPCI within 90 minutes where feasible. However, the 2023 ESC guidance uses 120 minutes from ECG-based STEMI diagnosis to PCI-mediated reperfusion as the threshold for choosing PPCI over fibrinolysis.
2. If PPCI cannot be achieved within 120 minutes, consider immediate fibrinolysis for eligible patients presenting within 12 hours of symptom onset, ideally within 10 minutes of diagnosis, followed by transfer to a PCI centre.
4. If thrombolysis is required — which agent?
Hyperkalaemia itself is not a standard contraindication to fibrinolysis. However, renal impairment is common in patients with hyperkalaemia and may increase bleeding risk.
Tenecteplase or alteplase would generally be preferable to streptokinase. Fibrin-specific agents are recommended by ESC guidance. OUP Academic
| Agent | Renal considerations | Recommendation |
|---|---|---|
| Tenecteplase (Metalyse) | Predominantly hepatic elimination; no established dose adjustment for severe renal impairment | Preferred where available |
| Alteplase (Actilyse) | Renal impairment warrants bleeding-risk assessment; no routine renal-specific dose adjustment | Preferred alternative during shortages |
| Reteplase (Rapilysin) | Check product-specific contraindications, particularly in severe renal dysfunction | Specialist-approved alternative |
| Streptokinase | Severe renal disease and associated bleeding risks require particular caution; check the specific SmPC | Reserve option only |
Tenecteplase
- Single weight-based IV bolus, using the STEMI-specific preparation and dosing schedule.
- Consider the recommended half-dose strategy in patients aged 75 years or older, in accordance with the local STEMI protocol.
- No established renal dose adjustment; severe renal impairment remains an area of limited pharmacokinetic evidence.
Alteplase
- Established fibrin-specific alternative.
- Requires a STEMI-specific accelerated infusion regimen rather than the stroke thrombolysis regimen.
- Confirm the correct formulation, weight-based dosing, contraindications and adjunctive anticoagulation.
Streptokinase
Streptokinase is less fibrin-specific, more immunogenic and associated with hypotension and allergic reactions. Previous exposure is particularly important.
In the GUSTO trial, 30-day mortality was 6.3% with accelerated alteplase versus 7.3% with streptokinase-based treatment, although the accompanying anticoagulation strategies also differed.
Additional considerations before fibrinolysis
- Diagnostic certainty: Do not thrombolyse an ECG pattern likely to be explained solely by hyperkalaemia.
- Bleeding risk: Check for intracranial haemorrhage history, recent stroke, active bleeding, major trauma, recent surgery, uncontrolled hypertension and suspected aortic dissection.
- Renal impairment: Review creatinine clearance, platelet count, haemoglobin and anticoagulant exposure.
- Anticoagulation: Enoxaparin requires adjustment in severe renal impairment; UFH may be more suitable in severe AKI or uncertain renal function.
- Age: Older patients have higher intracranial bleeding risk and may require an altered fibrinolytic and antithrombotic regimen.
For enoxaparin, use creatinine clearance rather than relying on eGFR alone when making prescribing decisions.
5. After thrombolysis
Thrombolysis is not the end of the reperfusion pathway.
- Transfer immediately to a PCI-capable centre.
- Assess symptoms, haemodynamics and ST-segment resolution at 60–90 minutes.
- If ST elevation has resolved by less than 50%, or there is ongoing ischaemia or instability, arrange immediate rescue PCI.
- If thrombolysis appears successful, arrange routine coronary angiography within 2–24 hours.
- Continue potassium, glucose and renal function monitoring, including surveillance for recurrent hyperkalaemia. OUP Academic
Key messages
1. Check K⁺ rapidly using i-STAT/VBG — do not delay PPCI activation.
2. Recognise pseudo-STEMI, but remember hyperkalaemia and true STEMI can coexist.
3. Treat dangerous hyperkalaemia and arrange reperfusion simultaneously.
4. Aim for PPCI within 90 minutes; use the guideline 120-minute threshold when deciding between PPCI and fibrinolysis.
5. If fibrinolysis is required, favour a fibrin-specific agent and account for renal impairment, age and bleeding risk.
References
- ESC Guidelines for the Management of Acute Coronary Syndromes (2023) — reperfusion strategy, timing, fibrinolysis and pharmaco-invasive care.
- UK Kidney Association — Treatment of Acute Hyperkalaemia in Adults — updated July 2026.
- Resuscitation Council UK 2025 — Special Circumstances — emergency treatment of hyperkalaemia.
- Metalyse SmPC — tenecteplase dosing and renal impairment.
- Actilyse SmPC — alteplase STEMI regimen and precautions.
