ECG Interpretation in Ischemic Heart Disease

myocardial ischemia v. infarction

-ischemia: occurs when the oxygen supplied by the coronary arteries does not meet the metabolic demands of the heart muscle, most commonly caused by a blockage of a coronary artery caused by atherosclerotic plaque; can also occur when there is an oxygen supply-demand mismatch that is not caused by obstructive plaque

-infarction: cell necrosis that occurs from prolonged/severe ischemia; can be subendocardial (limited to the innermost layers of the myocardium) or transmural (the entire thickness of the myocardium)

ECG wave form

-ventricular repolarization is very sensitive to myocardial perfusion

-ischemia and infarction can be detected by ST-segment and T wave changes, or in the case of irreversible myocardial necrosis, pathologic Q waves

NSTEMI v STEMI

ST elevation, depression, and Q waves

-non-ST-segment elevation myocardial infarction (NSTEMI)

non-atherosclerotic causes of NSTEMI (type-2 NSTEMI)

-ischemia that is not related to an unstable coronary plaque

-arrhythmia/tachycardia

-hypoxia

-sepsis

-heart failure/cardiomyopathy

-pulmonary embolism

-post-operative

-anemia

-hypertension/hypotension

-severe aortic stenosis

-stroke/neurologic

-ST-segment elevation myocardial infarction (STEMI)

non-atherosclerotic causes of STEMI

-spontaneous coronary artery dissection (tear of the coronary artery)

-coronary vasospasm (sudden constriction of the artery)

-embolism to the coronary artery (blood clot ejected and lodges in coronary artery)

-takotsubo cardiomyopathy (stress cardiomyopathy- heart failure caused by sudden/extreme stress)

-vasculitis (takayasu arteritis or Kawasaki disease)

-old myocardial infarction with pathologic Q waves

evolution of STEMI

-hyperacute T waves

-evolving STEMI

coronary artery distribution

-right coronary artery: perfuses the inferior wall of the left ventricle

-left anterior descending artery: perfuses anterior wall of the left ventricle

-left circumflex artery: perfuses lateral wall of the left ventricle

localization of STEMI- leads, territory, artery

coronary blood supply of the cardiac conduction system

new LBBB + CP

-think STEMI equivalent