Cardiogenic Shock

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Tissue hypoperfusion: depressed mental status, cool extremities, urine output < 30 mL/hour

• Hypotension: systolic blood pressure < 90 mm Hg

• Cardiac index < 2.2 L/min/m²

• Pulmonary artery wedge pressure > 15 mm Hg

GENERAL CONSIDERATIONS

• Causes and contributors: right or left ventricular failure, mechanical complications of acute myocardial infarction (MI) ventricular septal rupture, papillary muscle rupture or dysfunction, and free wall rupture; cardiomyopathies: valve disease; arrhythmias; toxic substances; posttraumatic and abnormalities of diastolic filling

• Shock resulting from an acute MI typically involves ≥ 40% of the left ventricular myocardium

• Most patients dying of cardiogenic shock have severe 3-vessel coronary artery disease

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• History of chest pain associated with MI within hours or up to a week

• Cardiac arrest associated with an acute MI

• Shortness of breath or acute respiratory distress

• Syncope

• Palpitations

• Nausea, vomiting

• Diaphoresis

• Obtundation and lethargy

PHYSICAL EXAM FINDINGS

• Systolic blood < 90 mm Hg

• Tachycardia

• Tachypnea

• Confusion, lethargy, or obtundation

• Pulmonary rales

• Jugular venous distention

• Displaced and diffuse apical impulse

• Muffled heart sounds in the presence of a pericardial effusion or cardiac tamponade

• S₃ and S₄

• Short, systolic murmur in patients with acute, severe mitral regurgitation

  • – Systolic murmur and associated parasternal thrill may indicate a ventricular septal rupture

• Hepatomegaly; pulsatile liver with severe tricuspid regurgitation

• Ascites in cases of longstanding right heart failure

• Peripheral edema

• Peripheral pulses are rapid and faint

• Mottled extremities

• Cool, ashen, or cyanotic skin

DIFFERENTIAL DIAGNOSIS

• Septic shock

• Hypovolemia

• Extracardiac obstructive: pulmonary embolism, pericardial tamponade

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Troponin

• Electrolytes, blood urea nitrogen, creatinine, and serum lactate

• CBC

• Bilirubin, alanine transaminase, aspartate transaminase, lactate dehydrogenase, partial thromboplastin time, prothrombin time

• Arterial blood gases

ELECTROCARDIOGRAPHY

• Sinus tachycardia or atrial tachyarrhythmias

• Q waves may indicate prior MI

• ST and T waves suggestive of an acute MI

IMAGING STUDIES

• Chest x-ray:

  • – Cardiomegaly and pulmonary vascular congestion or edema

  • – Heart size may be normal in patients with a first infarction

  • – Pulmonary congestion may be less prominent or absent in patients with predominant right ventricular failure or hypovolemia

• Echocardiography:

  • – Provides assessment of left and right ventricular size and function, global and segmental wall motion, valvular function (stenosis or regurgitation), right ventricular systolic pressures, and detection of ventricular septal shunts and pericardial fluid

DIAGNOSTIC PROCEDURES

• Right heart catheterization (generally useful to exclude other causes of shock); hemodynamic indicators of cardiogenic shock are pulmonary capillary wedge pressure > 15 mm Hg and a cardiac index < 2.2 ...