4. Diagnosis Of Myocardial Ischemia

Question 0

Systolic Wall Thickening

Answer 0

• Normally increase 50% of end diastole value
• Loss of thickening is most sensitive change associated with ischemia
• May progress to wall thinning and dyskinesis
• Hemodynamics are preserved with compensatory hyperkinesis of unaffected regions

Question 1

Order of sensitivity in diagnosing reduced myocardial blood flow

Answer 1

1. TEE detects regional wall motion abnormalities
2. EKG changes (also has lower specificity due to many other physiologic reasons for having EKG changes)
3. Elevation of filling pressures noted by PAC

Question 2

Scoring wall motion abnormalities

Answer 2

Normal: 30-50% wall thickening
Mild HK: 30-50
Severe HK: <10
Dyskinesis: absent or systolic thinning

Question 3

Endocardium excursion vs wall thickening

Answer 3

• Endocaridal excursion tends to overestimate the area of hypoperfused myocardium, whereas wall thickening closely approximates it
• Endocaridal excursion is easily measured around entire surface of ventricle since endocardium is well defined, whereas wall thickening is more difficult with poorly defined epicardium
• Endocaridal excursion affected by rotation and movement of LV whereas wall thickening is not

Question 4

Dobutamine Stress Test

Answer 4

• Normally with low levels of dobutamine the heart becomes hyperkinetic with increased coronary blood flow
• Myocardial ischemia = previously normal segment developing HK or AK following dobutamine
• Chronic infarct = no increase in wall thickening in response to low or high levels of dobutamine
• Viable myocardium with contractile reserve (stunned myocardium) = shows improvement in function with low dose dobutamine
• Hibernating myocardium = has a biphasic response with improvement at low doses of dobutamine but deterioration at higher doses

Question 5

What is the only TEE view in which a portion of the territories of all three main coronary vessels is visible?

Answer 5

Transgastric short axis

Question 6

Wall motion score index

Answer 6

• Each segment is given a number based on wall motion, with increasing numbers representing worse function

Score index = sum of all segment/# segments assessed

Question 7

Ischemic Mitral Regurgitation

Answer 7

• Central in origin with marked increase in PA pressures
• Etiology unclear:
  
  • acute ventricle dilation causing incomplete coaptation
  • ischemic dysfunction of papillary muscles
  • hyperkinesis of ventricle wall underlying normal papillary muscle

Question 8

Causes of MR associated with myocardial infarction

Answer 8

• LV cavity and annulus dilation
• Aneurismal or pseudoaneurismal changes
• Papillary muscle rupture
  
  • most severe and life threatening
  • frequently posteromedial (perfused only by RCA vs anterolateral perfused by circumflex and LAD)

Question 9

Right Ventricle Ischemia

Answer 9

• RV is more susceptible than LV to incomplete preservation on CPB
• Signs of RV failure
  
  • elevation of CVP without increased PA pressures
  • RV dilation without increased PA pressures
  • severe tricuspid regurgitation

Question 10

What coronary artery is at highest risk for air emboli?

Answer 10

RCA because it exits the aorta anteriorly at a 90 degree angle

Question 11

Causes of ischemia during CABG

Answer 11

Pre-CPB

• hemodynamics (hypotension, tachycardia)
• ischemia during cannulation (hypotension)
• plaque dislodgment from prior graft
• v-fib

Post-CPB

• low cardiac output state
• graft problems
• air emboli
• v-fib