Post MI Complications

Rapid Review·Cardiovascular

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Coronary Artery Disease

T1Must know

Focus on

Timing plus one new finding names the complication: collapse in the first day is ventricular fibrillation; a new murmur at day 3 to 7 is a papillary muscle or septal rupture; sudden pulseless electrical activity at day 5 to 14 is free-wall rupture; persistent ST elevation weeks later is an aneurysm; pleuritic pain weeks later is Dressler syndrome.

Key takeaways

The clock of complications

Three families

complications of myocardial infarction (MI) follow a timeline.

Electrical: first 24 to 48 hours.
Mechanical: ruptures at 2 to 14 days, when the necrotic wall is softest; aneurysm later.
Inflammatory or embolic: pericarditis early, Dressler late, mural thrombus.

Early reperfusion is the single best prevention for all of them

late revascularization raises the risk of peri-infarction pericarditis too.

What this shows

Complications of MI on a timeline. 0 to 24 hours: ventricular arrhythmia and sudden death, bradyarrhythmia and AV block, acute heart failure, cardiogenic shock. 1 to 3 days: early infarct-associated pericarditis. 3 to 14 days: papillary muscle rupture with acute mitral regurgitation, ventricular septal rupture with a left-to-right shunt, free wall rupture with tamponade, pseudoaneurysm with mural thrombus. 2 weeks to months: true left ventricular aneurysm with mural thrombus, and Dressler syndrome. Arrhythmias, heart failure and reinfarction can occur at any time.

Arrhythmias (mostly under 48 hours)

What this shows

Tracings along the post-MI clock. First 24 hours: ventricular tachycardia, ventricular fibrillation and AV block (third-degree block shown). From the third day: pericardial effusion or tamponade (low voltage) and, later, the persistent ST elevation of a ventricular aneurysm.

Ventricular fibrillation (VF)

the most common cause of death in the first 24 hours (re-entry in ischemic tissue).

VF is the most common fatal rhythm, ahead of ventricular tachycardia.
Defibrillate VF or pulseless ventricular tachycardia (VT); amiodarone or lidocaine for recurrent VT; correct potassium and magnesium.
Early VF does not by itself mandate an implantable cardioverter-defibrillator (ICD); VT or VF beyond 48 hours does.

Bradycardia and atrioventricular (AV) block after inferior MI

the right coronary artery feeds the nodes.

Atropine, then temporary pacing if unstable; usually transient.

Mobitz II or complete block after anterior MI

means septal necrosis.

Pacing, and a worse prognosis.

Mechanical complications

Risk factors

first MI, transmural infarct, late or no reperfusion, older women, hypertension, non-steroidal anti-inflammatory drug (NSAID) or steroid use.

All three ruptures present with abrupt deterioration

echocardiography is the diagnostic test.

Surgery is the treatment, with an intra-aortic balloon pump or vasodilators as a bridge.

Mechanical complications by timing
Timing	Complication	Clue	Diagnosis and management
2 to 7 days	Papillary muscle rupture (posteromedial; inferior MI)	Acute pulmonary edema, hypotension, soft apical holosystolic murmur without a thrill; may be nearly silent	Echo shows a flail leaflet and severe mitral regurgitation; afterload reduction, balloon pump, emergency surgery
3 to 5 days	Ventricular septal rupture (apical with anterior MI, basal with inferior MI)	New harsh holosystolic murmur at the left sternal border with a thrill, biventricular failure, oxygen step-up from right atrium to right ventricle	Echo with color Doppler; surgery
5 to 14 days	Free-wall rupture	Sudden hypotension, tamponade, pulseless electrical activity (PEA) arrest	Echo (hemopericardium); pericardiocentesis as a bridge, emergency surgery
3 to 14 days	Pseudoaneurysm	Rupture contained by pericardium; often silent, or murmur, heart failure, syncope	Echo or angiography; urgent surgery (high rupture risk)
Weeks to months	True left ventricular aneurysm	Persistent ST elevation, deep Q waves, heart failure, VT, mural thrombus and embolism	Echo (thin dyskinetic wall); ACE inhibitor, anticoagulate if thrombus; surgery rarely

Pseudoaneurysm vs true aneurysm

a pseudoaneurysm is a free-wall rupture contained by scar and pericardium.

Its risk of rupture into tamponade is higher than a true aneurysm's, which is why it goes to urgent surgery.

Telling the two post-MI murmurs apart

failure pattern and thrill.

Papillary muscle rupture: left-sided failure only (flash pulmonary edema); the murmur is soft or absent because left atrial and ventricular pressures equalize quickly.
Septal rupture: biventricular failure (pulmonary edema plus a raised jugular venous pressure); the murmur is loud and harsh with a palpable thrill.

Pericarditis (early and late)

Peri-infarction pericarditis (1 to 3 days)

pleuritic positional pain, a rub, diffuse ST elevation over the infarct.

It is an extension of myocardial inflammation, usually localized and self-limiting.
Treat with high-dose aspirin (for example 975 mg three times a day), with or without acetaminophen.

Dressler syndrome (2 to 10 weeks)

autoimmune pericarditis with fever, malaise, pleuritic pain, a rub, effusion and a raised erythrocyte sedimentation rate (ESR).

Treat with high-dose aspirin (or an NSAID once the infarct has healed) plus colchicine; steroids for refractory cases (Post-Cardiac Injury Syndrome).

Pump failure, thrombus and recovery

Heart failure and cardiogenic shock

follow a large anterior MI (ejection fraction under 40 percent).

Urgent revascularization, inotropes and mechanical support (Cardiogenic Shock), then long-term guideline therapy (Heart Failure).

Left ventricular mural thrombus (anterior MI, aneurysm)

causes embolic stroke, a cold pulseless limb, or renal or mesenteric infarction.

Anticoagulate with warfarin for 3 to 6 months.

What this shows

Left ventricular aneurysm: deep Q waves with persistent ST elevation in the leads of the prior transmural (usually anterior, left anterior descending) infarct, from fibrous scarring of the wall.

The aneurysm electrocardiogram (ECG)

persistent ST elevation with deep Q waves in the infarct leads.

True aneurysms also cause angina, heart failure and ventricular arrhythmias.

What this shows

Post-MI ACE inhibition: angiotensin II drives remodeling over weeks to months, with infarct ballooning, left ventricular dilation and reduced function; an ACE inhibitor limits infarct expansion and preserves contractile function.

An angiotensin-converting enzyme (ACE) inhibitor follows every large infarct

it limits the remodeling that produces the aneurysm.

Recurrent ischemia

new ST elevation in the same territory after a stent is stent thrombosis (Acute Coronary Syndrome).

Livedo, blue toes and a rising creatinine after catheterization is atheroembolism (Cholesterol Embolism Syndrome).

Return to activity

cardiac rehabilitation for everyone.

Moderate exertion and sexual activity resume when the patient can climb two flights of stairs comfortably (typically 1 to 2 weeks after an uncomplicated MI, later after bypass surgery or complications).
Driving after about a week for an uncomplicated MI.
Never combine nitrates with phosphodiesterase-5 inhibitors.

Five days after an inferior MI a patient develops sudden pulmonary edema and hypotension with only a soft apical murmur and no thrill. Which complication is this, and how does it differ from a septal rupture?

Papillary muscle rupture (posteromedial, single supply from the posterior descending artery): left-sided failure only, and the murmur is soft because left atrial and ventricular pressures equalize. A septal rupture gives biventricular failure and a loud harsh murmur with a thrill. Both need echo and surgery.

How it's tested

Sudden collapse 6 hours after an ST-elevation myocardial infarction (STEMI); the monitor shows a chaotic rhythm: ventricular fibrillation; defibrillate; it does not by itself mean an ICD.

Day 4 after an inferior MI: sudden dyspnea, crackles, blood pressure 85/50, a soft apical systolic murmur: posteromedial papillary muscle rupture; emergency echo and surgery.

Day 4 after an anterior MI: harsh holosystolic murmur at the left sternal border with a thrill and raised neck veins: ventricular septal rupture.

Day 7: abrupt hypotension, distended neck veins, then PEA: free-wall rupture with tamponade; pericardiocentesis and surgery.

Six weeks after MI: fever, pleuritic chest pain, friction rub, raised ESR: Dressler syndrome; aspirin or NSAID plus colchicine.

Persistent ST elevation with deep Q waves months after an anterior MI, now with a stroke: left ventricular aneurysm with mural thrombus; anticoagulate.

Go deeper

Guidelines: 2025 ACC/AHA Acute Coronary Syndromes Guideline

Related Step 2 pages: Acute Coronary Syndrome, Cardiac Tamponade, Acute Pericarditis, Post-Cardiac Injury Syndrome, Ventricular Tachycardia, Mitral Regurgitation, Cardiac Anatomy

High-yield images4

Left ventricular aneurysm: deep Q waves with persistent ST elevation in the leads of the prior transmural (usually anterior, left anterior descending) infarct, from fibrous scarring of the wall.

Post-MI ACE inhibition: angiotensin II drives remodeling over weeks to months, with infarct ballooning, left ventricular dilation and reduced function; an ACE inhibitor limits infarct expansion and preserves contractile function.

Tracings along the post-MI clock. First 24 hours: ventricular tachycardia, ventricular fibrillation and AV block (third-degree block shown). From the third day: pericardial effusion or tamponade (low voltage) and, later, the persistent ST elevation of a ventricular aneurysm.

Complications of MI on a timeline. 0 to 24 hours: ventricular arrhythmia and sudden death, bradyarrhythmia and AV block, acute heart failure, cardiogenic shock. 1 to 3 days: early infarct-associated pericarditis. 3 to 14 days: papillary muscle rupture with acute mitral regurgitation, ventricular septal rupture with a left-to-right shunt, free wall rupture with tamponade, pseudoaneurysm with mural thrombus. 2 weeks to months: true left ventricular aneurysm with mural thrombus, and Dressler syndrome. Arrhythmias, heart failure and reinfarction can occur at any time.

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