Cardiogenic Shock

Basics

Description

  • End-organ hypoperfusion due to severely impaired cardiac function resulting in diminished cardiac output, often in the setting of persistent hypotension
  • Myocardial infarction (MI) is the most common cause of cardiogenic shock cases (∼70%)
  • Most common cause of death in hospitalized patients with acute MI (AMI)
  • Underlying mechanisms in AMI:
    • Pump failure:
      • >40% infarction of left ventricle (LV) myocardium
      • Infarct with pre-existing LV dysfunction
      • Reinfarction
    • Mechanical complications:
      • Acute mitral regurgitation
      • Ventricular septal defect
      • LV free wall rupture
      • Papillary muscle rupture
      • Pericardial tamponade
    • Right ventricular (RV) infarction
  • 5–10% of patients with STEMI develop cardiogenic shock
  • 6–12 mo mortality in cardiogenic shock ≈ 50%

Etiology

  • AMI
  • Sepsis
  • Myocarditis
  • Myocardial contusion
  • Valvular disease
  • Cardiomyopathy
  • Left atrial myxoma
  • Arrhythmia
  • Heart block
  • Thyroid disorder
  • Drug toxicity:
    • β-Blocker
    • Calcium channel blocker
    • Adriamycin

Diagnosis

Signs And Symptoms

  • ABCs and vital signs:
    • Patent airway (early)
    • Labored breathing, tachypnea, and orthopnea (early); respiratory failure (late)
    • Diffuse crackles or wheezing
    • Hypoxia
    • Hypotension:
      • Systolic BP <90 mm Hg for at least 30 min, or requiring inotropes/vasopressors to maintain systolic BP >90 mm Hg
    • Tachycardia
    • Weak pulses
  • General:
    • Fatigue
    • Cyanosis
    • Pallor
    • Diaphoresis
    • Altered mental status
    • Cool extremities
    • Lower extremity edema
    • Delayed capillary refill
    • Decrease in body temperature
    • Urine output of <0 mL/hr
  • Neck:
    • Jugular venous distention
  • Cardiac:
    • Ischemic chest pain
    • Systolic apical blowing murmur
    • Gallop rhythm:
      • S3 reflects severe myocardial dysfunction
      • S4 is present in 80% patients in sinus rhythm with AMI
    • Systolic click:
      • Suggests rupture of the chordae tendineae
  • Abdominal:
    • Epigastric pain
    • Nausea and vomiting
    • Hepatojugular reflux
  • Neurologic:
    • Obtundation

History

  • Obtain history from patient, family, or EMS for clues to possible etiology – may have history of prior MI or heart failure
  • Medication history

Physical Exam

  • Perform rapid survey and stabilize ABCs
  • Distended neck veins and cool extremities distinguish cardiogenic shock from distributive and hypovolemic shock
  • Careful heart and lung exam
  • “Cold and wet” (cool extremities and signs of pulmonary congestion and/or lower extremity edema) is most common presentation of cardiogenic shock

Essential Workup

Ancillary studies further define the type and degree of shock and evaluate for cardiac injury to determine indications for emergent catheterization or surgical intervention

Diagnostic Tests And Interpretation

Ecg:

  • Normal ECG does not rule out AMI
  • Classically, findings of AMI (ST elevations in 2 or more contiguous leads)
  • Can also occur in non–ST-elevation acute coronary syndrome
  • Arrhythmias (ventricular tachycardia, ventricular fibrillation, atrial fibrillation)
  • New bundle branch block
  • Worsening of a symptomatic high-degree atrioventricular block
  • LV hypertrophy

Labs

  • N-terminal prohormone of brain natriuretic peptide (NT-proBNP):
    • Elevated NT-proBNP associated with increased mortality
  • Troponin, creatine kinase (CK), CK-MB:
    • CK-MB is helpful when troponin is indeterminate, ie, with renal insufficiency or unknown onset of ACS/AMI
  • Electrolytes and renal function:
    • Acute renal failure is strongly associated with increased mortality
  • Hepatic panel:
    • Elevated aminotransferase levels associated with increased mortality
  • Complete blood count (CBC):
    • Evaluate for anemia
    • Identify anemia or elevated WBC
  • Lactate:
    • >2.0 mmol/L suggests end-organ hypoperfusion associated with increased mortality
  • Blood gas (venous or arterial)
  • Decreased PO2, elevated PCO2, metabolic acidosis
  • Drug levels (eg, digoxin)

Imaging

  • CXR:
    • Pulmonary edema
    • Pleural effusion
    • Cardiomegaly
    • Pneumonia
    • Pericardial effusion
  • Emergent echocardiography:
    • Transthoracic echocardiography (TTE) with color

Doppler

    • LV contractility looking for hypokinesis, akinesis, or dyskinesis
    • LV dilation
    • Acute mitral regurgitation or septal defects
    • RV dilation, tricuspid insufficiency, high pulmonary artery, and RV pressures suggest pulmonary embolism
    • RV hypokinesis or akinesis, RV dilation, normal pulmonary pressures suggest RV infarction
    • Pericardial effusion, right atrium, or RV diastolic collapse suggest cardiac tamponade
    • Point-of-care ultrasound (thoracic and IVC)
    • Evaluation for pulmonary edema (>3 B lines in bilateral lungs)
    • IVC >2 cm suggesting fluid overload

Differential Diagnosis

  • Obstructive shock:
    • Tension pneumothorax
    • Cardiac tamponade
    • Pulmonary embolism
    • Spontaneous esophageal rupture
    • Air embolus
  • Distributive shock:
    • Sepsis
    • Anaphylaxis
    • Addisonian crisis
    • Neurogenic shock
  • Hypovolemic shock:
    • Hemorrhage
    • GI losses
    • Dehydration
    • Burns

Treatment

Prehospital

  • ABCs, IV access, O2, monitor
  • Consider fluid bolus (250–500 mL crystalloid) if no crackles on lung exam
  • Aspirin
  • Nitroglycerin or morphine sulfate for chest pain in absence of hypotension. Should be avoided if suspicion of RV infarction
  • Transport suspected AMI patients to facility with 24-hr cardiac revascularization capability

Initial Stabilization/Therapy

  • ABCs
  • 2 large-bore peripheral IV lines
  • Cardiac monitor
  • Goal oxygen saturation >90%
  • Consider noninvasive positive pressure ventilation (NIPPV) if tolerated
  • Endotracheal intubation and mechanical ventilation for respiratory failure:
    • Consider etomidate for induction (minimal effect on BP)
    • Low tidal volumes (5–7 mL/kg ideal body weight) are lung protective and optimize blood flow between pulmonary and parenchymal vasculature
  • Fluid challenge (250–500 mL crystalloid) if hypovolemic and in absence of pulmonary congestion
  • Foley catheter to monitor urine output

Ed Treatment/Procedures

  • AMI:
    • Cardiology consultation for emergent percutaneous coronary revascularization
    • Aspirin
    • Heparin or bivalirudin
    • Thrombolysis if percutaneous coronary intervention or bypass surgery not available
    • GP IIb/IIIa inhibitors prior to percutaneous coronary intervention
    • Clopidogrel or other platelet inhibitors often held until after revascularization attempt, may be contraindicated in patients requiring emergent bypass surgery
  • Hypotension:
    • May cautiously trial 250–500 mL crystalloid IV fluid bolus if hypovolemic and no signs of pulmonary edema or fluid overload
    • Norepinephrine (NE) is 1st-line vasopressor
    • Goal mean arterial pressure >65 mm Hg
  • Inotropy and adjunctive treatments:
    • Dobutamine is the preferred 1st-line inotrope and may be used with NE if patient is not persistently hypotensive
    • Milrinone may be considered in conjunction with dobutamine
    • Epinephrine can be considered in cases of bradycardia
  • Pulmonary edema:
    • Nitroglycerin drip or furosemide in the normotensive patient
  • Prompt cardiology consultation is crucial for the initiation of the following therapies:
    • Early revascularization as single most important life-saving measure
    • IABP independently improves survival in experienced centers
    • Evaluation for the role of VADs and ECMO in refractory cases of cardiogenic shock

Medication

  • Bivalirudin 0.75 mg/kg bolus then 1.75 mg/kg/hr IV
  • Clopidogrel 600 mg PO
  • Dobutamine: 2–10 mcg/kg/min, titrate to 20 mcg/kg/min as needed IV; max dose 20 mcg/kg/min
  • Furosemide: 40–80 mg initial dose, may repeat as needed (Pediatrics: 1 mg/kg IV or IM, not to exceed 6 mg/kg) IV or IM
  • Milrinone: 50 mcg/kg loading dose, 0.125–0.75 mcg/kg/min continuous infusion IV
  • Nitroglycerin: 5–20 mcg/min (peds: 0.1–1 mcg/kg/min) IV, USE NON-PVC tubing
  • Nitroprusside: 0.3 mcg/kg/min, titrate to maximum of 10 mcg/kg/min IV
  • NE: 0.05 mcg/kg/min IV, titrate up as needed to maximum of 3 mcg/kg/min

Follow-Up

Disposition

Admission Criteria

  • All patients in cardiogenic shock require admission to a critical care unit
  • Cardiology consultation necessary for consideration of emergent coronary angiography and reperfusion or advanced therapies

Pearls And Pitfalls

  • Cardiogenic shock is the leading cause of death in inpatient AMI
  • Early recognition of preshock states is essential
  • Early revascularization associated with improved outcomes

Additional Readings

  1. Daly M, Long B, Koyfman A, Lentz S. Identifying cardiogenic shock in the emergency department. Am J Emerg Med. 2020;38(11):2425–2433.  [PMID:33039227]
  2. Mebazaa A, Tolppanen H, Mueller C, et al. Acute heart failure and cardiogenic shock: A multidisclipinary practical guidance. Intensive Care Med. 2016;42:147–163.
  3. Reyentovich A, Barghash MH, Hochman JS. Management of refractory cardiogenic shock. Nat Rev Cardiol. 2016;13:481–492.  [PMID:27356877]
  4. Samsky MD, Morrow DA, Proudfoot AG, Hochman JS, Thiele H, Rao SV. Cardiogenic shock after acute myocardial infarction: A review. JAMA. 2021;326(18):1840–1850. Erratum in: JAMA. 2021;326(22):2333.  [PMID:34751704]
  5. Tehrani BN, Truesdell AG, Psotka MA, et al. A standardized and comprehensive approach to the management of cardiogenic shock. JACC Heart Fail. 2020;8(11):879–891.  [PMID:33121700]
  6. Vahdatpour C, Collins D, Goldberg S. Cardiogenic Shock. J Am Heart Assoc. 2019;8(8):e011991.  [PMID:30947630]
  7. van Diepen S, Katz JN, Albert NM, et al. Contemporary management of cardiogenic shock: A scientific statement from the American Heart Association. Circulation. 2017;136:e232–e268.  [PMID:28923988]
  8. Vincent JL, Quintairos E Silva A, Couto L Jr, Taccone FS. The value of blood lactate kinetics in critically ill patients: a systematic review. Crit Care. 2016;20:257–271.  [PMID:27520452]

See Also (Topic, Algorithm, Electronic Media Element)

Shock; MI

Authors

Gordon A. MacDougall

Shamai A. Grossman