Myocardial Ishcemia and Infarction Chapter 8: St Segment Elevation Ischemia and Q Wave Infarct Patterns

Terminology Ischemia Angina Pectoris Necrosis Myocardial Infarction Epicardium Subendocardium TransmuraL three major coronary arteries

Transmural Ischemia Acute Phase St segment elevation Sometimes tall T waves in certain leads Acute phase may last hours to days

Transmural Ischemia Evolving phase T wave inversion in the leads where the previously showed ST segment elevation

Transmural Ischemia Location Anterior Leads V1 - V6, I and aVl Inferior Leads II, III and aVf

Anterior MI

Inferior MI

Recipocity Compare the anterior leads (V1 - V6, I and aVl)to the inferior leads (II, III and aVf)

ST Depression in II, III and aVf St Depression in V1-V6, I and aVl Anterior MI Inferior MI Early Phase ST elevation Tall T waves V1-V6, I and aVl II, III and aVf ST Depression in II, III and aVf St Depression in V1-V6, I and aVl Evolving Phase Inverted T waves in V1-V6, I and aVl Inverted T waves in II, III and aVf

ST Elevation The ST elevation seen with acute MI is called a “Current of injury” ST segment elevations are the earliest ECG signs of acute MI

Q Waves Q waves are characteristic markers of infarction. (But not all transmural infarcts lead to Q waves.) New Q waves of an MI generally appear with the first day or two With an Anterior MI, these Q waves are seen in one of more of leads V1-V6, I and aVl With an Inferior MI, these Q waves are seen in one of more of leads II, III and aVf

Normal Q Waves large Q waves Small Q waves Horizontal Axis Vertical Axis Small Q waves Horizontal Axis Small Q waves Small Q waves Vertical Axis Small Q waves Vertical Axis Small Q waves

Abnormal Q waves in V1 and V2 Tall T waves in V2-V5 Abnormal Q waves in V1 and V2

Normal and Abnormal Q Waves Narrow (less than 0.04 sec), Low amplitude Abnormal if greater than 0.04 sec in leads I, II, III, aVf or leads V3 - V6. Wider Q waves in V1, V2, III, and aVf can be normal Not all Q waves are abnormal, Not all Q waves are the result of MI.

Anterior Infarctions FYI Anterior MI show loss of R wave progression in the chest leads Anterospetal Infarcts: Loss of R waves in V1 and V2 “Strictly” Anterior Infarcts: Loss of R waves in V3 and V4 Anterolateral or Anteroapical infarcts: abnormal Q waves in V5 and V6

Inferior Infarctions FYI Abnormal Q waves in leads II, III, and aVF

Other FYI Posterior Infarctions Right Ventricular Infarctions Ventricular Aneurysm Multiple Infarctions “Silent” MI MI with Bundle Branch Block

Myocardial Ischemia and Infarction Chapter 9: St Segment Depression Ischemia and non-Q Wave Infarct Patterns

Subendocardial Ischemia Inner layer St Segment depression Anterior leads (I, aVl and V1-V6) Inferior leads (II, III, and aVf) May see ST segment elevation in aVr

Subendocardial Ischemia

Subendocardial Ischemia Transient ST segment depression ST segment depression often occurs with angina, which generally returns to baseline when the angina subsides

Subendocardial Ischemia Exercise

Subendocardial Ischemia ST segment depression criteria 1 mm or more horizontal or downward lasts 0.08 seconds depression of only the J point with rapid upward sloping are considered normal.

Subendocardial Ischemia False-Positive ST depression without disease False-Negative Disease without ST depression Silent Myocardial ischemia

Subendocardial Infarction Persistent ST depression

Subendo-cardial Infarction T wave inversion

Non-Specific ST-T changes FYI Subtle changes slight flattening of T wave minimal T wave inversion

Prinzmetal’s Angina Transient ST segment elevation with angina No Q waves, no T wave inversion Angina may occur at rest or at night Coronary artery spasm