06. Complications of Acute Myocardial Infarction

Introduction

  • Complications after ACS can be divided by timing into acute complications and subacute-chronic complications.
    • Though this delineation is generally true, these complications can occur earlier or later than expected.
  • Acute (on presentation to days) complications:
    • Cardiogenic shock from LV failure.
    • Arrhythmias.
    • Ischemic papillary muscle rupture.
    • Ventricular septal defect (VSD).
    • LV free wall rupture.
    • Early pericarditis.
  • Subacute-chronic (weeks or more) complications:
    • LV thrombus.
    • LV aneurysm.
    • Late pericarditis.

Cardiogenic Shock from LV Failure 

  • Epidemiology: 5-10% of patients with ACS. High mortality. Typically within 1 day after STEMI and within several days after NSTEMI.
  • Risk factors: anterior infarct, diabetes, older age, prior MI, multivessel disease, or left main disease.
  • Physical exam: signs of heart failure with sustained hypotension and volume overload.
  • Diagnosis: chest x-ray, echocardiography, right heart catheterization.
  • Treatment: early revascularization, inotropic/pressor support, ventilatory support, mechanical circulatory support (see section Cardiogenic Shock).

Arrhythmias 

  • Both tachyarrhythmias and bradyarrhythmias can occur, typically on presentation to days after ACS.
  • Tachyarrhythmias:
    • Supraventricular: atrial fibrillation is the most common. See Atrial Fibrillation section for management. Specifically, avoid class I antiarrhythmics.
    • Ventricular:
      • Accelerated idioventricular rhythm is a common reperfusion arrhythmia which does not require treatment unless patient is symptomatic or hemodynamically unstable.
      • Ventricular tachycardia:
        • Within the first 48 hours after infarct is more likely due to increased automaticity in the region of ischemia/infarction. Treat with correction of acid/base status and electrolyte abnormalities, medical and/or interventional treatment of ongoing ischemia, and GDMT for any co-occurring HF.
        • After the first 48 hours is more likely due to a reentrant circuit around scar. ICD placement is indicated before discharge (if VT episode not due to electrolyte or acid/base abnormalities, transient ischemia, or reinfarction).

Papillary Muscle Rupture 

  • Epidemiology: <1% of patients, typically within a week after ACS.
  • Risk factors: inferior MI (single blood supply to posteromedial papillary muscle), large infarct, poor collateral circulation, first infarct, diabetes, older women. Can result from a relatively small or clinically unapparent MI.
  • Physical exam: new systolic murmur (loudest at the apex, radiating to the axilla), intensity of the murmur does not correlate to severity of mitral regurgitation.
  • Diagnosis: echocardiogram.
  • Treatment: urgent surgery. Temporary stabilization with medical therapy may be needed, including afterload reduction with vasodilator or IABP.

Ventricular Septal Defect

  • Epidemiology: <1% of patients, typically within a week after ACS.
  • Risk factors: large infarct, single vessel disease, poor collateral circulation, first infarct, diabetes, older women.
  • Physical exam: holosystolic murmur loudest over LLSB as well as thrill.
  • Diagnosis: echocardiography, right heart cath.
  • Treatment: emergent surgical repair. Temporary stabilization with medical therapy may be needed, including afterload reduction with vasodilator, inotropes, mechanical circulatory support.

LV Free Wall Rupture 

  • Epidemiology: <1% of patients in the modern reperfusion era, typically within a week after ACS.
  • Risk factors: transmural MI, first MI, anterior infarct, lack of collaterals, no or delayed reperfusion, female gender, steroids, NSAIDs.
  • Physical exam: acute decompensation related to cardiac tamponade (hypotension, elevated JVP, diminished heart sounds, pulsus paradoxus). Acutely, a small effusion can cause severe tamponade. 
  • Diagnosis: echocardiography, right heart cath.
  • Treatment: emergent surgical repair.

Early Pericarditis

  • Epidemiology: 10% of patients with acute MI, typically within days after ACS.
  • Risk factors: transmural MI.
  • Symptoms: sharp, stabbing pain, worse while supine and with inspiration, radiating to trapezius.
  • Physical exam: pericardial friction rub in 85% of patients.
  • Diagnosis: EKG may show evidence of pericarditis, echo may reveal pericardial effusion.
  • Treatment: aspirin and consider colchicine. Avoid NSAIDs and corticosteroids (may interfere with healing of infarcted myocardium). Avoid heparin to reduce risk of hemorrhagic transformation of pericardial effusion.

LV Thrombus

  • Epidemiology: 5-10% of patients after PCI for ACS, typically occurs within two weeks after ACS.
  • Risk factors: anterior MI, large MI, LV aneurysm.
  • Complications: embolization risk.
  • Diagnosis: sensitivity for LV thrombus CMR > TEE > TTE. Echo contrast can improve diagnostic accuracy.
  • Treatment: anticoagulation with heparin bridge to warfarin, goal INR 2-3. Duration of anticoagulation varies, but patients will need serial imaging to assess for resolution of thrombus usually in 3 month intervals.

LV Aneurysm

  • Epidemiology: <5% of patients with STEMI (though 10-30% if no reperfusion), typically in the days to weeks after ACS.
  • Risk factors: anterior MI, steroids, NSAIDs.
  • Physical exam: diffuse, displaced point of maximal impulse (PMI), ± S3 and/or S4.
  • Diagnosis: EKG (Q waves in V1-3 with persistent ST elevation), echo, cardiac MRI. Make sure to distinguish it from a pseudoaneursym which has a higher risk for rupture and needs surgical attention.
  • Treatment: anticoagulation with heparin/warfarin if mural thrombus present.

Late Pericarditis (Dressler's Syndrome)

  • Epidemiology: 1-3% of patients with acute MI, typically within weeks-months after ACS.
  • Etiology: thought to be secondary to immune-mediated injury.
  • Physical exam: pericardial friction rub, fever.
  • Diagnosis: EKG may show evidence of pericarditis, echo may show pericardial effusion.
  • Treatment: aspirin and consider colchicine. If >4 weeks after MI, can use NSAIDs (ibuprofen preferred, indomethacin may diminish coronary blood flow); corticosteroids are second-line.

References

Hohnloser SH, Kuck KH, Roberts RS et al. Prophylactic Use of an Implantable Cardioverter–Defibrillator after Acute Myocardial Infarction. N Engl J Med 2004; 351:2481-2488.

Ibanez, Borja, et al. "2017 ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation: The Task Force for the management of acute myocardial infarction in patients presenting with ST-segment elevation of the European Society of Cardiology (ESC)." European heart journal 39.2 (2018): 119-177.

O’Gara PT, et al. 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction. J Am Coll Cardiol. 2013;61(4)e78-e140.