Ischemia/Infarction (Exam #2) Flashcards
What is the “path” of depolarization in heart tissue?
Endocardial → Epicardial (inner to outer)
What is the “path” of repolarization in heart tissue?
Epicardial → Endocardial (outer to inner)
Define Myocardial Ischemia. What general changes are seen (2)?
Ischemia = REVERSIBLE cell damage due to decreased O2
- ST segment changes
- T wave changes
What are the three criteria for Myocardial Ischemia (__ OR __ OR __)?
- ST segment depression OR - T wave inversion OR - Peaked/Symmetrical T waves
Define Myocardial Injury. What general changes are seen?
Injury = prolonged ischemia → further cell damage but NO cell death
- ST segment changes
What is the primary criteria for Myocardial Injury?
ST segment elevation
What other condition presents with T wave inversion, and how can you differentiate it from Transmural Ischemia?
Strain presents with T wave inversion but they are asymmetrical
- Transmural Ischemia = T wave inversion and SYMMETRICAL
What is seen with Subendocardial Ischemia?
Transient ST segment depression
What is seen with Transmural Ischemia?
Transient ST segment elevation
What causes the T wave inversion seen with Myocardial Ischemia?
Delayed repolarization
What causes the T wave changes seen when Subendocardial Ischemia progresses to Transmural Ischemia?
Reversal of repolarization causes T wave to invert and become symmetrical
What other condition presents with ST segment elevation, and how can you differentiate it from Myocardial Injury?
Pericarditis presents with DIFFUSE ST segment elevation
- Injury presents in respective leads (not diffuse)
Define Myocardial Infarction. What general changes are seen?
Infarction = cell death, enzymes released (T)
- Pathologic Q waves
What causes the development of pathologic Q waves?
Infarcted tissue is electrically silenced
What are the criteria for Q waves (__ AND __ AND __), and when do these present?
Myocardial Infarction - 0.04+ seconds in duration AND - At least 1/3 the height of R waves in same QRS complex AND - Present in 2+ contiguous leads
How can you differentiate Ischemia from Infarction (non-EKG)?
Elevated Troponin (T) with Myocardial Infarction
How can you differentiate an NSTEMI from a STEMI?
- NSTEMI = ST segment changes + T wave changes (NO Q waves)
- STEMI = ST segment changes + T wave changes + Q waves
In what three leads does an Anterior MI present?
V2, V3 and V4
- V1 NOT INVOLVED
What type of MI presents in V2, V3 and V4?
Anterior MI
In what two leads does a Septal MI present?
V1 and V2
What type of MI presents in V1 and V2?
Septal MI
In what three leads does an Anterolateral MI present?
V4, V5 and V6
What type of MI presents in V4, V5 and V6?
Anterolateral MI
In what four leads does a Lateral MI present?
I, aVL, V5 and V6
What type of MI presents in I, aVL, V5 and V6?
Lateral MI
In what three leads does an Inferior MI present?
II, III and aVF
What type of MI presents in II, III and aVF?
Inferior MI
What are the two criteria for a Posterior MI (hint: be specific with the R waves)?
Reciprocal changes in V1 and V2
- Abnormal R waves in V1 and V2 (0.04+ seconds in duration, R > S, patient is 30+ years old)
- ST segment depression
How can you differentiate a NEW MI from an OLD MI?
- New = ST segment changes + T wave changes + Q waves
- Old = Q waves only
What should you suspect if you see ST depression in V1, V2 and V3 with NO other ST elevation in other leads?
Posterior MI
What finding on EKG is suspicious for Posterior MI?
ST depression seen in V1, V2 and V3 with NO other ST elevation in other leads
