Cardiogenic shock

Cardiogenic shock is a medical emergency resulting from inadequate blood flow to the body's organs due to the dysfunction of the heart. Signs of inadequate blood flow include low urine production (<30 mL/hour), cool arms and legs, and decreased level of consciousness. People may also have a severely low blood pressure.

Causes of cardiogenic shock include cardiomyopathic, arrhythmic, and mechanical. Cardiogenic shock is most commonly precipitated by a heart attack. Cardiogenic shock is estimated to complicate 5-10% of all heart attacks.

Treatment of cardiogenic shock depends on the cause with the initial goals to improve blood flow to the body. If cardiogenic shock is due to a heart attack, attempts to open the heart's arteries may help. Certain medications, such as dobutamine and milrinone, improve the heart's ability to contract and can also be used. When these measures fail, more advanced options such as mechanical support devices (such as an intra-aortic balloon pump or left ventricular assist device).

Cardiogenic shock is a condition that is difficult to fully reverse even with an early diagnosis. However, early initiation of treatment may improve outcomes. Care should also be directed to any other organs that are affected by this lack of blood flow (e.g., dialysis for the kidneys, mechanical ventilation for lung dysfunction).

Mortality rates for cardiogenic shock are high but have been decreasing in the United States. This is likely due to its rapid identification and treatment in recent decades. Some studies have suggested that this is possibly related to new treatment advances. The 30-day mortality rate for cardiogenic shock after a heart attack is 40% with a 1-year mortality rate of 50%. Nonetheless, the mortality rates remain high and multi-organ failure in addition to cardiogenic shock is associated with higher rates of mortality.

Cardiogenic shock may present as shortness of breath (respiratory distress) due to fluid buildup in the lungs (pulmonary edema). Reduced perfusion to the brain can cause drowsiness, with anoxic brain injury causing coma and death. Low blood pressure due to decrease in cardiac output may cause circulatory shock with symptoms of a rapid, weak pulse due to decreased circulation, cool, clammy, and mottled skin (cutis marmorata) due to vasoconstriction and subsequent hypoperfusion of the skin, low urine output, confusion. Increased heart filling pressures can cause orthopnea and distended jugular veins due to increased jugular venous pressure.

Cardiogenic shock is caused by the failure of the heart to pump effectively. It is due to damage to the heart muscle, most often from a heart attack. Other causes include abnormal heart rhythms, cardiomyopathy, heart valve problems, ventricular outflow obstruction (i.e. systolic anterior motion in hypertrophic cardiomyopathy), myocardial contusion or ventriculoseptal defects. It can also be caused by a sudden depressurization (e.g. in an aircraft), where air bubbles are released into the bloodstream (Henry's law), causing heart failure.

In cardiogenic shock due to a heart attack, shock can develop at the time of the heart attack or after. The median time from heart attack to developing shock was about 5.5-6 hours. In a registry study, 74% of people developed shock within 24 hours of the heart attack, with 46.6% developing shock within 6 hours of the heart attack. The left anterior descending artery and the left main coronary artery are the two most commonly blocked arteries in heart attacks that lead to cardiogenic shock.