New Ischemic Syndromes

In the past, it was generally believed that extended periods of myocardial ischemia led to irreversible damage of the myocardial or infarcted (necrotic) tissue. However, more recently, between the clinical conditions of transient ischemia (angina pectoris) and myocardial infarction, five additional ischemic syndromes have been described (Figs. 2 and 3) (2,3). The stunned myocardium is characterized by postischemic impairment of myocardial function, but it is considered acute and completely reversible.

The hibernating myocardium is also characterized by depressed myocardial function of variable duration, primarily caused by impaired oxygen delivery through an occluded vessel, and recovery of function occurs on reflow to the ischemic region. The hibernating myocardium is similar to the stunned myocardium, with the main difference that reperfusion is not the cause of myocardial hibernation, as is the case with myocardial stunning. However, hibernation can be considered a state of chronic stunning; yet, the exact mechanism of hibernation remains largely unknown (4).

The maimed myocardium is considered the most severe syndrome. It is characterized by irreversible myocardial damage that follows ischemia and reperfusion, and there is a delayed recovery to only partial preischemic function.

In ischemic preconditioning, multiple brief (<5 min) ischemic episodes followed by reperfusion subsequently enhance the myocardial tolerance to a longer (<45 min) ischemic event

Transient Coronary Occlusion incompiete Coronary Occlusion

Sustained Coronary Occlusion i

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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