I. Causes
II. Pathophysiology
III. Management
IV. Perspective and Research Implications
GLOSSARY
atheromatous same as atherosclerotic, a plaque that juts into the lumen and obstructs the flow of blood in arteries.
myocardial infarction death of an area of heart muscle due to blockage of a coronary artery by blood clot and atheroma; medical term for a heart attack of coronary thrombosis.
revascularization procedures that include coronary artery bypass surgery to bypass obstructive atheromatous plaques or percu¬taneous coronary intervention (PCI) using balloon angioplasty with or without stents.
tissues aggregation of similarly specialized cells which together perform certain special functions.
CARDIOGENIC SHOCK IS CAUSED BY A DECREASED pumping ability of the heart that results in a shock-like state with insufficient blood perfusion to organs and tissues. During cardiogenic shock, systolic blood pressure is less than 90 mmHg for greater than one hour and not responsive to IV fluids. The cardiac index is less than 2.2 L/minute/m2, and the pulmonary capillary wedge pres¬sure is greater than 18 mmHg. Patients usually have clouded consciousness and cold extremities.

• I. CAUSES
  Acute myocardial infarction is the most common cause of cardiogenic shock. Other causes of cardiogenic shock are given in Table 1. The complete occlusion of a coronary artery by a clot causes death of an area of heart muscle that is supplied by that blood vessel and its branches. If a very large area of heart muscle is involved, the general pumping capability of the heart is severely compromised. Because dead myocardium cannot contract, blood cannot be effectively ejected out of the left ventricle into the aorta [see Fig. 1 in the chapter Anatomy of the Heart and Circulation). Blood is held up in the lungs and fluid accumulates in air sacs causing pulmonary edema which results in severe shortness of breath. Because blood cannot be ejected from the heart, the blood pressure falls drastically. When more than 40% of the heart muscle is involved, cardiogenic shock often occurs.
• II. PATHOPHYSIOLOGY
  In general terms shock is a clinical state in which target organ–tissue perfusion is inadequate to supply vital sub¬strates and remove the metabolic waste. Inadequate cellular oxygenation leads to marked generalized impairment of cellular function and multiorgan failure.
• III. MANAGEMENT
  Most patients require an intra-aortic balloon pump and IV vasopressor drugs to support blood perfusion to organs and tissues. The opening of the obstructed artery using balloon angioplasty with the insertion of stents has improved survival. Because approximately 40% of cardio-genic shock patients have occlusions in three coronary arteries, emergency coronary artery bypass surgery is the only measure that has improved survival in this group. In the SHOCK trial, the overall 30-day mortality rate was 47% in patients undergoing emergency revascu-larization versus 56% in the medical stabilization group.
• IV. PERSPECTIVE AND RESEARCH IMPLICATIONS
  The incidence of cardiogenic shock will not decrease until the main cause, which is obstruction to coronary arteries by atheromatous plaque and thrombosis, is arrested. Thrombolytic therapy is of little value and revasculariza-tion with balloon angioplasty and coronary bypass surgery can only be undertaken in special centers. The SHOCK trial only studied 300 patients. More research is required to assess if we could develop cardioactive agents to protect the myocardium from necrosis during an occlusion of a coronary artery.
• BIBLIOGRAPHY
  Hasdal, D., Topol, E. J., Calif, R. M. et al. Cardiogenic shock