Lecture 24: Myocardial Infarction

Question 1

What is the range of normal axis?

Answer 1

0/-30 to +90

Question 2

What does a LAD tell you?

What does a RAD tell you?

Answer 2

• Cells on the right side of the heart are damaged, can’t depolarize and using the left side to conduct electricity
• same, but left side is damaged and cannot depolarize

Question 3

What does a narrow QRS complex mean?

What does a wide QRS complex mean?

Answer 3

Electrical impulse coming from above AV node

Electrical impulse coming from below the AV node (ventricle)

Question 4

What is the classic presentation of CAD?

Answer 4

Heavy chest pressure, radiation to neck, jaw, left arm, epigastrium or between shoulder blades. With associated dyspnea or diaphoresis

Question 5

In which populations are silent MI s frequent?

What are the atypical symptoms of MI and which populations are these common?

Answer 5

• elderly women, diabetics

- dyspepsia or something else that isn’t classic. Women and diabetics

Question 6

What is the cause of CAD?

Answer 6

Narrowing of coronary arteries due to blockage

Question 7

What is the difference between unstable angina/NSTEMI and STEMI

Answer 7

-Unstable angina and NSTEMI refers to partial occlusion, portion of the heart is dying, not the whole wall yet (subendocardial)
STEMI refers to coronary occlusion, myocardial death up to the epicardium (wall)
+cardiac enzymes in both NSTEMI and STEMI

Question 8

What does ischemia mean? What type of changes in the ECG indicate this?
What does injury mean? What type of changes in the ECG indicate this?
What does infarction mean? What type of changes in the ECG indicate this?

Answer 8

• deficient blood supply = impaired repolarization. T wave changes
• deficient blood supply = inability to fully polarize. ST segment shifts
• dead tissue = no depolarization. Q waves

Question 9

When concerned about MI or CAD, what should you evaluate on an ECG?

Answer 9

ST segment (J point) - normal, depressed or elevated? 
Q wave - prominent (> 2 boxes) - infarct, scarred myocardium, heart muscle takes longer to fully depolarize, usually patient has past hx of MI

Question 10

What are the cardiac biomarkers of necrosis?

What can cause a false positive cTnT?

Answer 10

Trop I and T (CTnI and CTnT), CK-MB

Renal failure

Question 11

How does NSTEMI present clinically?

Answer 11

+ cardiac enzymes but no ST elevation. Can have depressions or T wave inversions, particularly in chest leads (but this is not always indicative of NSTEMI)

Question 12

What characterizes a STEMI on an ECG?

Answer 12

> 2 mm ST elevation from base point in men
1.5 mm ST elevation from base point in women
-New LBBB

Question 13

What artery feeds the anterior wall?
What artery feeds the inferior wall?
What artery feeds the lateral wall?
What artery feeds the posterior wall?

Answer 13

LADA
RCA
Circumflex A.
PDA

Question 14

What leads measure anterior wall damage?
What leads measure inferior wall damage?
What leads measure lateral wall damage?
What leads measure posterior wall damage?

Answer 14

V1 - V4
2, 3, aVF
1, aVL, V5, v6
V1-v2

Question 15

What does reciprocal change mean in MI?

Answer 15

When there is STEMI in one group of leads, there is usually an ST depression at another group of leads