Cardiovascular · Year 1 · from Cardiovascular

Case 1: Cardiogenic Shock Post-MI

Patient Presentation

Demographics: 68-year-old male

Chief Complaint: Severe chest pain with progressive weakness

History of Present Illness: A 68-year-old male with history of diabetes and hypertension presents with severe crushing chest pain for 3 hours. Despite aspirin at home, his pain persists. Over the past hour, he has become increasingly weak, confused, and short of breath. He reports feeling "cold and clammy."

Physical Examination:

  • Vital Signs: BP 78/52 mmHg, HR 115 bpm, RR 28/min, SpO2 88% on room air, Temp 36.0°C
  • General: Diaphoretic, pale, obtunded, severe distress
  • Cardiovascular: Tachycardic, distant heart sounds, S3 gallop, JVP markedly elevated
  • Lungs: Diffuse bilateral crackles extending to upper lung fields
  • Extremities: Cold, mottled, prolonged capillary refill (5 seconds)
  • Urine output: Minimal (Foley draining 10 mL over past hour)

Workup

  • ECG: ST elevation in V1-V6, I, aVL (extensive anterior STEMI)
  • Labs:
  • Troponin I: 45 ng/mL
  • Lactate: 6.8 mmol/L (elevated, indicating tissue hypoperfusion)
  • Creatinine: 2.1 mg/dL (baseline 1.0)
  • BNP: 2500 pg/mL
  • Echocardiogram:
  • LVEF: 20% (severely reduced)
  • Extensive anterior, septal, and apical akinesis
  • No mechanical complications (VSD, free wall rupture)
  • Pulmonary artery catheter (Swan-Ganz):
  • Cardiac index: 1.6 L/min/m² (severely reduced, normal >2.2)
  • PCWP: 28 mmHg (elevated, normal <18)
  • SVR: 2400 dynes·s/cm⁵ (elevated due to compensatory vasoconstriction)

Diagnosis

Cardiogenic shock secondary to extensive anterior STEMI

Cardiac Output Correlation: Cardiac Output = Heart Rate × Stroke Volume

In cardiogenic shock:

  • Stroke volume: Severely reduced due to massive myocardial damage (↓ contractility)
  • Preload: Elevated (PCWP 28 mmHg) but not translating to improved output (failing on Frank-Starling curve)
  • Afterload: Elevated SVR worsens cardiac output (increased impedance to ejection)
  • Contractility: Severely impaired (EF 20%)
  • Compensatory tachycardia: Heart rate increases to maintain CO, but insufficient

Cardiac index formula: CI = CO / BSA (normal 2.5-4.0 L/min/m²) This patient's CI of 1.6 L/min/m² indicates severe pump failure.

Frank-Starling curve: The damaged heart operates on a flat or descending limb—increased preload no longer improves output.

Treatment

  1. Emergent PCI to restore coronary flow (primary intervention)
  2. Inotropic support:
  • Dobutamine (β1 agonist): Increases contractility and HR
  • Or milrinone (PDE inhibitor): Increases contractility and reduces afterload
  1. Vasopressor support:
  • Norepinephrine if MAP critically low (maintains coronary perfusion)
  1. Mechanical circulatory support:
  • Intra-aortic balloon pump (IABP): Augments diastolic pressure, reduces afterload
  • Consider Impella or ECMO if refractory
  1. Intubation for respiratory failure
  2. Continuous hemodynamic monitoring

Clinical Image

Image Description: Pulmonary artery catheter pressure tracing showing elevated pulmonary capillary wedge pressure (PCWP) indicative of left-sided heart failure and elevated filling pressures characteristic of cardiogenic shock.

Source: Wikimedia Commons - Swan-Ganz catheter License: CC BY-SA 3.0 URL: https://commons.wikimedia.org/wiki/File:Pulmonary_artery_catheter.png

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