Myocardial Ischemia v.1

Myocardial Ischemia

Prevention and treatment of perioperative myocardial ischemia is a primary consideration.  Two consistent factors associated with the pathogenesis of myocardial ischemia are inadequate oxygen supply to the myocardium due to localized coronary lesions, and excessive oxygen demand due to increased hemodynamic workload associated with increased heart rate, blood pressure, or adrenergic stimulation of myocardial contractility.  Myocardial ischemia can be detected by observing changes in the ECG, identifying wall motion abnormalities using TEE, or manifested as increased pulmonary artery wedge pressures.

Ischemic changes in leads II, III, and aVF may reflect involvement of the right atrium, right ventricle, sinoatrial node, and atrioventricular node due to decreased perfusion from right coronary artery.  Leads V3-V5 target the anterolateral aspect of the left ventricle and reflect hypoperfusion through the left anterior descending artery.  Leads I and aVL identify ischemia to the lateral wall of the left ventricle supplied by the circumflex artery.

Treatment for ischemia may include several therapeutic steps such reducing wall tension with nitroglycerin, controlling heart rate with ß-adrenergic blocking agents, reducing contractility by controlling myocardial depression with increased anesthetic levels, and maintaining coronary perfusion pressure using a non-chronotropic agent such as phenylephrine.

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