Cardiac MRI > Pathology > Coronary Artery Disease > Introduction

Introduction to Coronary Artery Disease

Ischemic heart disease is the most common cause of death in America. While Cardiac MRI is not the first modality routinely used in the evaluation of patients with ischemic heart disease, it does play a complementary role to other imaging modalities. Cardiac MRI can be used to evaluate global as well as regional cardiac function, detect acute and chronic infarcts as well as ischemia, distinguish hibernating and stunned myocardium from infarcted myocardium and determine myocardial viability.

Myocardial ischemia refers to insufficient delivery of oxygen to the myocardium, which can occur due to partial or total occlusion of a coronary artery. Ischemia leads to dysfunction of the myocardium and if it is severe and sustained will lead to infarction of the myocardium. Myocardial infarction usually results from rupture of an atherosclerotic plaque in a coronary artery leading to thrombus formation in that artery. The subendocardium is most vulnerable to ischemia and after total occlusion of coronary blood flow an infarct will expand from the subendocardium to the subepicardium, with the greatest damage to the subepicardium.

Patient experiencing ischemia may have symptoms of pressure, squeezing, or pain in the chest. This pain may radiate to the arms or the jaw. Pain that does not resolve is suggestive of infarction. Additional symptoms of ischemia/infarction include light-headedness, dyspnea, sweating, and nausea.

After an acute ischemic event, reperfusion may occur spontaneously or secondary to intervention. Following reperfusion, the myocardium responds depending on the type of injury in three typical zones: cells at the periphery can be protected from ischemia from opening of collateral vessels, deeper cells may have experienced ischemia but are improved by reperfusion, and a core of myocardium where ischemia has caused necrosis of blood vessels (microvascular obstruction) thus prohibiting salvage by reperfusion (aka the no-reflow territory).

This diagram depicts a short axis cross section of the left ventricle in a patient with an acute MI, with the bright red representing normal myocardium and the gray at the center of the figure being the blood pool. The three areas within the myocardium represent the no-reflow territory with microvascular obstruction (black), the area undergoing ischemia but that can be salvaged by reperfusion (maroon), and the area preserved from ischemia by opening of collaterals (brown).

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