Complications of Myocardial Infarction
On this page
Direct answer
Complications of myocardial infarction are arrhythmias, mechanical defects and inflammatory sequelae, each with a characteristic time of onset. Ventricular fibrillation dominates the first hours, free wall and septal rupture typically occur within the first week, papillary muscle rupture causes acute mitral regurgitation, and Dressler syndrome is a late autoimmune pericarditis appearing weeks after the event.
What you must remember
- Early arrhythmias: ventricular fibrillation and sustained ventricular tachycardia cluster in the first 24 to 48 hours; accelerated idioventricular rhythm is usually benign and signals reperfusion.
- Bradyarrhythmias: inferior infarcts often cause transient AV block through the AV nodal branch of the RCA; new bifascicular or complete block in an anterior infarct signals extensive LAD disease and needs pacing.
- Free wall rupture: usually between days one and seven, commonest in elderly women with a first anterior infarct and hypertension; it presents as tamponade with electromechanical dissociation, and surgery is definitive.
- Ventricular septal rupture: a new harsh pansystolic murmur at the lower left sternal border with a thrill, shock and biventricular failure; intra-aortic balloon counterpulsation reduces the shunt before surgical repair.
- Papillary muscle rupture: the posteromedial muscle, which has a single blood supply, ruptures more often; acute severe mitral regurgitation with pulmonary oedema and a soft murmur needs urgent valve replacement.
- Dressler syndrome: autoimmune post-infarction pericarditis appearing two to ten weeks after the event, with fever, pleuritic pain and a friction rub; aspirin, cautiously NSAIDs, and colchicine for resistant cases.
- Late sequelae: persistent ST elevation with a paradoxical bulge signals left ventricular aneurysm, and mural thrombus needs anticoagulation.
A worked scenario on day three
A 68-year-old woman three days after an anterior STEMI becomes hypotensive, breathless and grey, with a new harsh pansystolic murmur at the lower left sternal edge and a palpable thrill. The differential is ventricular septal rupture or papillary muscle rupture, both presenting with acute failure.
The murmur separates them only partly: septal rupture gives a loud harsh murmur with thrill, while papillary muscle rupture gives a softer murmur, often with pulmonary oedema out of proportion to it. Bedside echocardiography resolves the question, showing a left-to-right shunt across the septum or a flail leaflet with severe regurgitation. Management then follows the lesion.
- Septal rupture: Give inotropic support and afterload reduction, with an intra-aortic balloon pump limiting the shunt while the patient is prepared for surgical repair, which should be done early.
- Papillary muscle rupture: Surgery is needed, usually mitral valve replacement, with vasodilators and inotropes supporting output in the interim.
- Effusion check: The same echo checks for a pericardial effusion, because a new effusion raises the spectre of free wall rupture.
- Tamponade: Pericardiocentesis is a temporising step before surgery.
- Late presentation: Fever and pleuritic pain at three weeks would instead suggest Dressler syndrome, with a different timeline and treatment.
Timing, murmur character and echo findings together separate these lesions, which is the skill examiners test.
Where the exam tries to catch you
Timing, murmur and mechanism are the three things examiners test.
- Trap: attributing a late friction rub to rupture. Correct: free wall, septal and papillary muscle rupture cluster in the first week, while Dressler syndrome appears weeks later.
- Trap: judging papillary muscle rupture by a harsh murmur. Correct: that rupture gives a soft murmur, unlike the harsh septal murmur, so careful auscultation is needed.
- Trap: calling early pericarditis Dressler syndrome. Correct: early pericarditis occurs in the first days with diffuse ST elevation, though both produce a pericardial rub.
- Trap: assuming septal rupture follows only anterior infarction. Correct: it follows anterior infarcts (apical septum) and inferior infarcts (basal posterior septum), and the inferior type usually has the worse prognosis.
In a viva, the safe closing line is that any new murmur or sudden hypotension after infarction needs an echocardiogram and surgical referral until proven otherwise.
Frequently asked questions
Which complication presents with a new harsh murmur and shock in the first week?
Ventricular septal rupture presents with a new harsh pansystolic murmur at the lower left sternal border, a thrill, shock and biventricular failure. Echocardiography confirms the left-to-right shunt and is needed before surgery.
Why does posteromedial papillary muscle rupture occur more often than anterolateral rupture?
The posteromedial papillary muscle receives blood from a single artery, usually the posterior descending branch of the RCA, whereas the anterolateral muscle has a dual supply from the LAD and the circumflex. A single blood supply makes the posteromedial muscle more vulnerable to infarction.
How does Dressler syndrome differ from early post-infarction pericarditis?
Early pericarditis occurs within the first days of infarction and shows diffuse ST elevation with a pericardial friction rub. Dressler syndrome appears weeks later, typically two to ten weeks after the event, and is autoimmune in origin.
What is the first step in managing free wall rupture with tamponade?
Pericardiocentesis relieves tamponade and buys time. Surgical repair remains the only definitive treatment, and survival depends on getting the patient to theatre quickly after decompression.