What are snapshots? In what ways are they limited?
- Instantaneous images
- No info about physiologic impact of what's seen
- No info about changes through time (movement of fluid, HR, BP)
What must be present in order to evaluate a heart condition for physiological cause?
Symptoms (ischemia, pale, weak, dizzy)
What is a lesion? Significance?
- Choke point where everything downstream of it will have trouble getting nutritive flow
- Can lead to myocardial tissue death (infarction)
What is coronary atherosclerosis?
Plaque buildup in the arteries resulting in blockage of flow
What do atherosclerotic lesions look like in an angiogram/arteriogram?
What is an angiogram?
An anatomic exam that visualizes the coronary lumen
What is an exercise stress test?
Physiologic exams wherein the O2 demand of the heart is driven up to see if myocardial blood supply can keep up (look for ischemia)
What can be concluded if the myocardial blood supply cannot keep up with the O2 demand during a stress test?
Myocardial ischemia will result
How can the O2 demand of the heart be predicted?
RPP = HR x SBP
What should precisely follow increases in RPP?
Myocardial O2 uptake (mVO2)
What is O2 delivery to the heart solely based on? Why?
- Enhanced blood flow
- B/c the heart is maximally extractive of O2 at rest
When does myocardial ischemia occur?
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
What is the dobutamine stress test?
Pharmacologic stress test during which the subject is injected w/ an epinephrine equivalent gradually instead of exercising
What is an exercise tallium scan?
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)