STEPTRACKERCARDIOVASCULAR | PATHOLOGY | HIGH-YIELD REVIEW

MI Complications

Electrical, pump, mechanical and inflammatory complications — each has a typical day and a typical infarct location.

FOCUS ON
Tie each complication to its time and its artery. Inferior MI (RCA) → bradycardia/AV block, RV infarct, posteromedial papillary rupture. Anterior MI (LAD) → apical thrombus, aneurysm, septal rupture. Mechanical ruptures cluster in days 3–7 while macrophages soften the wall.
COMPLICATION
TIMING
MECHANISM
CLUE · TREATMENT
Arrhythmias
First 24 h (highest risk)
Ischemic, irritable myocardium; conduction tissue infarcted
VF = top cause of pre-hospital death · inferior MI → AV nodal block, bradycardia
Cardiogenic shock / acute HF
Hours–days
Loss of ≥ 40% of LV muscle
Hypotension, pulmonary edema · revascularize, inotropes, mechanical support
RV infarction
Early, with inferior MI
RCA occlusion proximal to RV branches
Hypotension + JVD + clear lungs; ST elevation in V4R · IV fluids, avoid nitrates
Fibrinous pericarditis
1–3 days
Inflammation over a transmural infarct
Pleuritic pain, friction rub
Papillary muscle rupture
2–7 days
Posteromedial muscle has a single supply (PDA, usually RCA)
Sudden pulmonary edema + new apical holosystolic murmur (acute MR) after inferior MI
Septal rupture
3–5 days
Necrotic septum tears → left-to-right shunt
New harsh holosystolic murmur at left sternal border; O₂ step-up from RA to RV
Free-wall rupture
5–14 days
Softened free wall gives way into pericardium
Sudden tamponade → PEA arrest; elderly women, first MI, hypertension
Pseudoaneurysm
~1–2 weeks
Free-wall rupture contained by pericardium or scar; narrow neck
High rupture risk → urgent surgery
True ventricular aneurysm
2 weeks–months
Thin full-thickness scar bulges outward (dyskinesis); broad neck
HF, arrhythmia, mural thrombus; persistent ST elevation
Mural thrombus
Days–weeks
Akinetic apex (large anterior MI) → stasis
Embolic stroke, limb ischemia · anticoagulate
Dressler syndrome
Weeks–months
Autoimmune reaction to exposed cardiac antigens
Fever, pericarditis, pleuritis, ↑ ESR · NSAIDs, colchicine

Mechanism — why ruptures cluster in week one

NecrosisDays 0–2
→
Macrophages digestDays 3–7
→
No collagen yetWall weakest
→
RupturePapillary, septum, free wall
→
Scar formsRupture risk falls; aneurysm risk rises

Ruptures and aneurysms compared

LESION
PRESENTATION
TYPICAL MI
Papillary muscle rupture
Acute MR, flash pulmonary edema
Inferior (RCA)
Septal rupture
VSD murmur, O₂ step-up
Anterior or inferior
Free-wall rupture
Tamponade, sudden death
Anterior or lateral
Pseudoaneurysm
Contained rupture, narrow neck
Inferolateral often
True aneurysm
Dyskinetic bulge, thrombus
Large anterior (LAD)

How it's tested

COMMON CONFUSIONA new holosystolic murmur after MI is either papillary rupture (apex, mitral regurgitation, pulmonary edema) or septal rupture (left sternal border, O₂ step-up).
THE TRAPInferior MI with hypotension and clear lungs is RV infarction. Nitroglycerin can crash the BP by removing preload; fluids are the treatment.
YOUR APPROACHDays since the MI + infarct location + exam (murmur, JVD, lungs, rub) → name the complication.

If you see… think…

Inferior MI + hypotension + JVD + clear lungs → RV infarct — fluids, no nitrates
Inferior MI with complete heart block → RCA supply to AV node
Large anterior MI, then embolic stroke → LV mural thrombus
Day 4: flash pulmonary edema + apical holosystolic murmur → papillary muscle rupture
Day 4: new murmur + O₂ step-up in RV → septal rupture
Day 6: sudden PEA arrest in an elderly woman → free-wall rupture with tamponade
Narrow-neck sac held by pericardium → pseudoaneurysm — surgery
Persistent ST elevation weeks later, dyskinetic wall → true ventricular aneurysm
Fever and pleuropericarditis 5 weeks after MI → Dressler syndrome