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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Complications after myocardial infarction

Cardiology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull
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Escalate

After MI, new shock, pulmonary oedema, recurrent chest pain, syncope, a new murmur or electrical instability requires immediate ABCDE assessment, senior cardiology/critical-care help and urgent echocardiography; activate resuscitation pathways if peri-arrest.

Synopsis

Recognise the time-critical electrical, pump and mechanical complications of myocardial infarction and choose the next diagnostic and escalation step.

  • Electrical complications are most prominent early: ventricular tachycardia/fibrillation, bradyarrhythmia and atrioventricular block can all cause sudden deterioration.
  • A new harsh pansystolic murmur with shock suggests ventricular septal rupture; an apical systolic murmur with flash pulmonary oedema suggests acute severe mitral regurgitation from papillary-muscle rupture.
  • Sudden hypotension, raised JVP and pulseless electrical activity may be free-wall rupture with tamponade; absence of a loud murmur does not exclude a mechanical defect.
  • Recurrent ischaemic pain or fresh ST change raises reinfarction, acute stent thrombosis or extension of infarction and demands an urgent ACS/reperfusion review.
  • Heart failure may reflect extensive LV injury, right-ventricular infarction, acute mitral regurgitation or a ventricular septal defect: identify the phenotype before giving fluid or vasodilator.
  • Early post-infarction pericarditis causes pleuritic positional pain; a later immune-mediated syndrome may include fever, pericardial or pleural pain and effusions.
  • LV aneurysm and akinetic segments predispose to heart failure, ventricular arrhythmia and mural thrombus; confirm thrombus with imaging before selecting anticoagulation.

Key red flags

Ventricular arrhythmia

Palpitations, syncope, broad-complex tachycardia, VF or cardiac arrest; correct ischaemia, hypoxia and electrolyte disturbance while following the RCUK peri-arrest or ALS algorithm.

Papillary-muscle rupture

Abrupt pulmonary oedema, hypotension and a new apical systolic murmur after MI; the murmur may be soft when cardiac output is very low.

Ventricular septal rupture

Acute heart failure or shock with a new harsh pansystolic murmur, often with a palpable thrill and biventricular failure.

Free-wall rupture and tamponade

Sudden collapse, hypotension, raised JVP, electromechanical dissociation or PEA; a contained rupture may present more subtly as a pseudoaneurysm.

Pump failure or cardiogenic shock

Cold peripheries, confusion, oliguria, narrow pulse pressure and pulmonary or systemic congestion; consider LV, RV and mechanical causes.

Investigation priorities

01
12-lead ECG plus continuous rhythm monitoringFirst step

Detect recurrent ischaemia, ventricular arrhythmia, bradycardia or AV block.

Management branches

First-lineAny sudden deterioration after MI

Shock, hypoxaemia, chest pain, arrhythmia, syncope or a new murmur

  1. Start ABCDE, attach defibrillator pads, obtain a 12-lead ECG, IV access, blood gas/lactate and targeted oxygen only for hypoxaemia.
  2. Call senior cardiology and critical care immediately; obtain bedside echocardiography without delaying resuscitation.
  3. Treat the dominant reversible cause: recurrent coronary occlusion, arrhythmia, hypovolaemia/bleeding, pump failure or mechanical rupture.
  4. Move early to the catheter laboratory, theatre or critical care according to the identified cause.
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE NG185: Acute coronary syndromesUK ACS, reperfusion, secondary prevention and rehabilitation route.
  • ESC 2023 Guidelines for acute coronary syndromesOfficial guidance on in-hospital and mechanical complications.
  • Resuscitation Council UK 2025 Adult advanced life supportCurrent UK cardiac-arrest and peri-arrest arrhythmia route.
  • NICE CG187: Acute heart failureAcute pump failure and shock pathway.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom