Cardiogenic shock


Cardiogenic shock is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart. Signs of inadequate blood flow include low urine production, cool arms and legs, and altered level of consciousness. People may also have a severely low blood pressure and heart rate.
Causes of cardiogenic shock include cardiomyopathic, arrhythmic, and mechanical. CS is most commonly precipitated by acute myocardial infarction. Cardiogenic shock is a type of circulatory shock, in which there is insufficient blood flow and oxygen supply for biological tissues to meet the metabolic demands for oxygen and nutrients. Cardiogenic shock is defined by sustained low blood pressure with tissue hypoperfusion despite adequate left ventricular filling pressure. People can have combined types of shock. Shock by definition is inadequate blood circulation to the rest of the body, which causes organ damage. Organs do not have enough oxygen delivery, and cannot adequately maintain their cellular metabolism.
Treatment of cardiogenic shock depends on the cause with the initial goals to improve blood flow to the body. This can done in a number of ways—fluid resuscitation, blood transfusions, vasopressors, and ionotropes. If cardiogenic shock is due to a heart attack, attempts to open the heart's arteries may help. An intra-aortic balloon pump or left ventricular assist device may improve matters until this can be done. Medications that improve the heart's ability to contract may help; however, it is unclear which is best. Norepinephrine may be better if the blood pressure is very low whereas dopamine or dobutamine may be more useful if only slightly low. Cardiogenic shock is a condition that is difficult to fully reverse even with an early diagnosis. With that being said, early initiation of mechanical circulatory support, early percutaneous coronary intervention, inotropes, and heart transplantation may improve outcomes. Care is directed to the dysfunctional organs.
Mortality rates have been decreasing in the United States. This is likely due to the rapid identification and treatment of the CS. Some studies have suggested that this possibly related to the increased use of coronary reperfusion strategies, like heart stents. Nonetheless, the mortality rates remain high. Multi-organ failure is associated with higher rates of mortality.

Signs and symptoms

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 or myocardial contusion. Other causes include abnormal heart rhythms, cardiomyopathy, heart valve problems, ventricular outflow obstruction, or ventriculoseptal defects.
It can also be caused by a sudden decompressurization, where air bubbles are released into the bloodstream, causing heart failure.

Diagnosis

Electrocardiogram

An electrocardiogram helps to establish the exact diagnosis and guides treatment, it may reveal:
may show poor ventricular function, signs of PED, rupture of the interventricular septum, 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

When cardiomyopathy is suspected as the cause of cardiogenic shock, a biopsy of heart muscle may be needed to make a definite diagnosis.

Cardiac index

If the cardiac index falls acutely below 2.2 L/min/m2, the person may be in cardiogenic shock.

Treatment

Depending on the type of cardiogenic shock, treatment involves infusion of fluids, or in shock refractory to fluids, inotropic medications. In case of an abnormal heart rhythm immediate synchronized cardioversion or anti-arrhythmic agents may be administered, e.g. adenosine.
Positive inotropic agents, which enhance the heart's pumping capabilities, are used to improve the contractility and correct the low blood pressure. Should that not suffice an intra-aortic balloon pump or a left ventricular assist device can be considered. Mechanical ventilation or ECMO may be used to help stabilize people with severe or refractory cardiogenic shock until they can be given some type of definitive treatment, such as a ventricular assist device. Finally, as a last resort, if the person is stable enough and otherwise qualifies, heart transplantation, or if not eligible an artificial heart, can be placed. These invasive measures are important tools—more than 50% of patients who do not die immediately due to cardiac arrest from a lethal abnormal heart rhythm and live to reach the hospital, die within the first 24 hours. The mortality rate for those still living at time of admission who suffer complications from cardiogenic shock is even worse around 85%, especially without drastic measures such as ventricular assist devices or transplantation.
Cardiogenic shock may be treated with intravenous dobutamine, which acts on β1 receptors of the heart leading to increased contractility and heart rate.