Myocardial Infarction Flashcards
Normal Q wave
amplitude is less than 25% of the amplitude of the R wave in that lead
Duration is less than 0.04 seconds
Normal ST Segment
flat line that follows the QRS complex
can be raised or depressed 1 mm normally
Normal T wave
oriented in the same direction as the preceding QRS complex
maximum of 5mm height in limb lead
maximum of 10mm in ant precordial lead
slightly asymmetrical
Myocardial Ischemia
interruption of coronary artery blood flow, often due to the gradual development of atherosclerosis
causes a gradual narrowing of the coronary artery
which type of cholesterol participates in plaque formation
LDL
which type of cholesterol participates in removal of plaque formations
HDL
what is an embolism
obstruction of an artery, typically by a clot of blood or an air bubble leads rapid occlusion
myocardial injury results
if ischemia progresses
myocardial infarction
death of myocardial cells
peaked T waves
may be seen in the early stages of acute myocardial infarction
T wave is more than 6 mm high in limb leads and 12 mm in precordial leads
T wave is more than 2/3 height of R wave
but within a short time frame about 2 hours T waves become inverted
t wave inversion
myocardial ischemia
t waves inversion because ischemic tissue does not repolarize normally
still symmetric
ST segment depression
myocardial ischemia
Areas of ischemia is more negative than the surrounding normal tissues
myocardial ischemia ECG
Peaked then inverted t waves and ST segment depression
ST segment elevation
myocardial injury
zone of injury does not repolarize completely so it remains more positive than surrounding tissue leading to a ST segment elevation
Pathologic Q waves
indicate the presence of irreversible myocardial damage or myocardial infarction
develop because the infarcted area becomes electrically silent (fails to depolarize) as they are functionally dead
