The clinical syndrome of shock has great potential for significant morbidity and mortality and is one of the most challenging conditions to treat. In accordance with Barcroft’s original construct for conceptualizing shock that was published nearly 100 years ago, shock results from 1 or more of the following mechanisms: impaired oxygenation or hypoxic hypoxia, reduced oxygen carrying capacity or anemic hypoxia, limited cardiac output or stagnant hypoxia, or impaired oxygen utilization or histotoxic hypoxia (eg, cyanide toxicity). Shock results from inadequate oxygen delivery relative to oxygen demand, and if the body’s intrinsic compensatory mechanisms of increased cardiac output and oxygen extraction are insufficient, or left inadequately treated, this can rapidly result in organ dysfunction or failure. The etiologies of shock are broad, as are its manifestations, and in this review we will discuss the pathophysiology, assessment, and treatment of cardiogenic shock.
Shock results from inadequate oxygen delivery relative to oxygen demand. Shock is not necessarily a problem of blood volume, cardiac output, or blood pressure, but it is always a problem of inadequate tissue oxygen delivery:
where DO2 is oxygen delivery, CaO2 is arterial oxygen content, and CO is cardiac output.
Cardiogenic shock is due to low cardiac output, the causes of which can be classified according to the determinants of cardiac output: inadequate preload, excessive afterload, intrinsic muscle failure, or dysrhythmia.
Cardiogenic shock can result from a number of etiologies. Although not an exhaustive list, the most common categories and causes are listed below.
Undiagnosed (or untreated) critical congenital heart disease: left heart obstructive lesions (critical coarctation, hypoplastic left heart syndrome, aortic stenosis); right heart obstructive lesions (critical pulmonary stenosis or pulmonary atresia); transposition of the great arteries
Postoperative congenital heart disease: early low output syndrome; residual cardiac defects; late postoperative decompensation due to right, left, or bi-ventricular systolic or diastolic dysfunction; or pulmonary hypertension
Primary myocardial disease: dilated, restrictive, hypertrophic cardiomyopathies
Pericardial disease: acute tamponade or chronic pericardial constriction
Arrhythmias: chronic untreated or undertreated arrhythmia resulting in cardiomyopathy, also pacemaker-induced cardiomyopathy can result from long term cardiac pacing
Acute coronary syndromes
Other etiologies of shock can manifest as cardiogenic shock
The timely recognition of cardiogenic shock requires a high index of suspicion, an appreciation for high-risk groups (eg, patients with known underlying cardiac disease) and a comprehensive consideration of all available information, including the medical history, physical examination, laboratory tests, and hemodynamic parameters.
HISTORY AND PHYSICAL EXAMINATION
Early markers of cardiogenic shock, from both the history and examination, may be subtle and easily missed or confused with other noncardiac causes of acute illness or shock leading to inappropriate interventions that may ...