8. Picturing the Heart

Question 1

What are snapshots? In what ways are they limited?

Answer 1

• Instantaneous images
• No info about physiologic impact of what’s seen
• No info about changes through time (movement of fluid, HR, BP)

Question 2

What must be present in order to evaluate a heart condition for physiological cause?

Answer 2

Symptoms (ischemia, pale, weak, dizzy)

Question 3

What is a lesion? Significance?

Answer 3

• Choke point where everything downstream of it will have trouble getting nutritive flow
• Can lead to myocardial tissue death (infarction)

Question 4

What is coronary atherosclerosis?

Answer 4

Plaque buildup in the arteries resulting in blockage of flow

Question 5

What do atherosclerotic lesions look like in an angiogram/arteriogram?

Answer 5

“Sausage-link” quality

Question 6

What is an angiogram?

Answer 6

An anatomic exam that visualizes the coronary lumen

Question 7

What is an exercise stress test?

Answer 7

Physiologic exams wherein the O₂ demand of the heart is driven up to see if myocardial blood supply can keep up (look for ischemia)

Question 8

What can be concluded if the myocardial blood supply cannot keep up with the O₂ demand during a stress test?

Answer 8

Myocardial ischemia will result

Question 9

How can the O₂ demand of the heart be predicted?

Answer 9

RPP = HR x SBP

Question 10

What should precisely follow increases in RPP?

Answer 10

Myocardial O₂ uptake (mVO₂)

Question 11

What is O₂ delivery to the heart solely based on? Why?

Answer 11

• Enhanced blood flow
• B/c the heart is maximally extractive of O₂ at rest

Question 12

When does myocardial ischemia occur?

Answer 12

When supply of O₂ > demand of O₂ due to a hemodynamically significant blockage (atherosclerosis)

• Exercise –> increased mVO₂ demand
• Decreased coronary blood flow –> decreased mVO₂ supply

Question 13

What is the dobutamine stress test?

Answer 13

Pharmacologic stress test during which the subject is injected w/ an epinephrine equivalent gradually instead of exercising

Question 14

What is an exercise tallium scan?

Answer 14

Patient has thallium injected into heart, then exercises. Doctor uses scanner to see thallium myocardial perfusion.

• Normal: even coronary perfusion –> even distribution of thallium signal
• Abnormal: area w/ blockage –> not filling w/ thallium as quickly as other parts (ischemic symptom)