Cardiogenic shock

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Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

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Overview

Cardiogenic shock is based upon an inadequate circulation of blood due to primary failure of the ventricles of the heart to function effectively.

Since this is a category of shock there is insufficient perfusion of tissue (i.e. the heart) to meet the required demand for oxygen and nutrients. This leads to cell death from oxygen starvation, hypoxia. Because of this it may lead to cardiac arrest (or circulatory arrest) which is an acute cessation of cardiac pump function.

Definition

Cardiogenic shock is defined by sustained hypotension with tissue hypoperfusion despite adequate left ventricular filling pressure. Signs of tissue hypoperfusion include oliguria (<30 mL/h), cool extremities, and altered mentation.

Etiology

Cardiogenic shock is caused by the failure of the heart to pump effectively. It can be due to damage to the heart muscle, most often from a large myocardial infarction. Other causes include arrhythmia, cardiomyopathy, cardiac valve problems, ventricular outflow obstruction (i.e. aortic valve stenosis, aortic dissection, systolic anterior motion (SAM) in hypertrophic cardiomyopathy), ventriculoseptal defects or medical error.

Signs and symptoms

• Anxiety, restlessness, altered mental state due to decreased cerebral perfusion and subsequent hypoxia.
• Hypotension due to decrease in cardiac output.
• A rapid, weak, thready pulse due to decreased circulation combined with tachycardia.
• Cool, clammy, and mottled skin (cutis marmorata), due to vasoconstriction and subsequent hypoperfusion of the skin.
• Distended jugular veins due to increased jugular venous pressure.
• Oliguria (low urine output) due insufficient renal perfusion if condition persists.
• Rapid and deep respirations (hyperventilation) due to sympathetic nervous system stimulation and acidosis.
• Fatigue due to hyperventilation and hypoxia.
• Absent pulse in tachyarrhythmia.
• Pulmonary Edema (fluid in the lungs) due to insufficient pumping of the heart, fluid backs up into the lungs.

Diagnosis

Electrocardiogram

An Electrocardiogram helps establishing the exact diagnosis and guides treatment, it may reveal:

• Cardiac arrhythmias
• Signs of cardiomyopathy

Radiology

Echocardiography may show arrhythmia, signs of PED, ventricular septal rupture (VSR), an obstructed outflow tract or cardiomyopathy.

Swan-ganz catheter

The Swan-ganz catheter or Pulmonary artery catheter may assist in the diagnosis by providing information on the hemodynamics.

Biopsy

In case of suspected cardiomyopathy a biopsy of heart muscle may be needed to make a definite diagnosis.

Diagnostic criteria of cardiogenic shock

A. Clinical criteria

1. Systolic blood pressure <90 mm Hg
2. Evidence of hypoperfusion
3. Cool, clammy periphery
4. Decreased urine output
5. Decreased level of consciousness

B. Hemodynamic criteria

1. Left ventricular end diastolic pressure or pulmonary capillary wedge pressure >15 mm Hg
2. Cardiac index <2.2 L/min/m2

Reference:

1. Data from Hochman JS, Sleeper LA, Webb JG, et al. Early revascularization in acute myocardial infarction complicated by cardiogenic shock. SHOCK Investigators. Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock. N Engl J Med 1999; 341 (9) : 625–34.

Treatment

In cardiogenic shock: depending on the type of myocardal infarction one can infuse fluids or in shock refractory to infusing fluids, inotropes should be administered. Positive inotropic agents, which enhance the heart's pumping capabilities, are used to improve the contractility and correct the hypotension. Should that not suffice an intra-aortic balloon pump (which reduces workload for the heart, and improves perfusion of the coronary arteries) can be considered or a left ventricular assist device (which augments the pump-function of the heart).

See also

• Intra-aortic balloon pump
• Ventricular assist device

References

• Irwin, R.S., Rippe, J.M., Curley, F.J., Heard, S.O. (1997) Procedures and Techniques in Intensive Care Medicine (3rd edition). Boston: Lippincott, Williams and Wilkins.
• Marino, P. (1997) The ICU Book. (2nd edition). Philadelphia: Lippincott, Williams and Wilkins.

External links

• Cardiogenic Shock by eMedicine