Cardiogenic shock is characterized by a decreased pumping ability of the heart that causes a shocklike state (ie, global hypoperfusion). It most commonly occurs in association with, and as a direct result of, acute myocardial infarction (AMI). The most common cause of cardiogenic shock is extensive acute myocardial infarction, although a smaller infarction in a patient with previously compromised left ventricular function may also precipitate shock. Cardiogenic shock is defined by sustained hypotension with tissue hypoperfusion despite adequate left ventricular filling pressure. Signs of tissue hypoperfusion include oliguria. Cardiogenic shock is characterized by both systolic and diastolic dysfunction. Patients who develop cardiogenic shock from acute MI consistently have evidence of progressive myocardial necrosis with infarct extension. Decreased coronary perfusion pressure and increased myocardial oxygen demand play a role in the vicious cycle that leads to cardiogenic shock.
Cardiogenic shock occurs in 8.6% of patients with ST-segment elevation MI with 29% of those presenting to the hospital already in shock. It occurs only in 2% of non–ST-segment elevation MI. Outcomes significantly improve only when rapid revascularization can be achieved. The recent SHOCK trial demonstrated that overall mortality when revascularization occurs is 38%. When rapid revascularization is not attempted, mortality rates approach 70%. Cardiogenic shock can also be caused by mechanical complications—such as acute mitral regurgitation, rupture of the interventricular septum, or rupture of the free wall—or by large right ventricular infarctions. Myocardial ischemia causes a decrease in contractile function, which leads to left ventricular dysfunction and decreased arterial pressure; these, in turn, exacerbate the myocardial ischemia. The overall incidence of cardiogenic shock is higher in men compared to women because of the increased prevalence of coronary artery disease in males.
Cardiogenic shock can be caused by disorders of the heart muscle, the valves, or the heart’s electrical conduction system. Cardiogenic shock is life threatening and requires emergency medical treatment. Dopamine, dobutamine, epinephrine, norepinephrine, amrinone, or other medications may be required to increase blood pressure and heart functioning. Echocardiography may show arrhythmia, signs of PED, ventricular septal rupture (VSR), an obstructed outflow tract or cardiomyopathy. Pain medicine may be given if necessary. Bed rest is recommended to reduce demands on the heart. Coronary artery bypass grafting. In this surgery, arteries or veins from other parts of the body are used to bypass (that is, go around) narrowed coronary arteries. The use of the IABP reduces systolic left ventricular afterload and augments diastolic coronary perfusion pressure, thereby increasing cardiac output and improving coronary artery blood flow. Heart monitoring, including hemodynamic monitoring, to guide treatment.
Treatment for Cardiogenic Shock Tips:
1. Inotropic medications should be considered in systems with appropriately trained paramedical personnel.
2. In case of cardiac arrhythmia several anti-arrhythmic agents may be administered, i.e. adenosine, verapamil, amiodarone, ß-blocker.
3. Balloon angioplasty (PTCA) may be an alternative to surgery in some cases.
4. Oxygen reduces the workload of the heart by reducing tissue demands for blood flow.
5. Heart monitoring, including hemodynamic monitoring, to guide treatment
6. Coronary artery bypass grafting. In this surgery, arteries or veins from other parts of the body are used to bypass (that is, go around) narrowed coronary arteries.
