Nuclear Cardiology

Question 1

role of left ventricular perfusion imaging

Answer 1

evaluate blood flow to myocardium

Question 2

Questions to ask yourself during perfusion study

Answer 2

1. is perfusion abnormality reversible during rest or fixed during stress/rest?
2. size of perfusion abnormality
3. severity: mild/subendocardial, moderate, or severe/transmural
4. which coronary artery territory?
5. associated abnormalities such as right ventricular uptake, ischemic dilation, wall motion abnormalities?

Question 3

types of stress in perfusion imaging

Answer 3

physical (treadmill)
pharmacologic/adrenergic (dobutamine)
pharmacologic/vasodilatory (dipyridamole/adenosine)

Question 4

indications for myocardial perfusion imaging

Answer 4

1. evaluation of acute chest pain (evaluate ambiguous cases; chest pain with negative EKG/troponins)
2. evaluation of hemodynamic significant coronary stenosis
3. risk stratification after MI
4. preoperative risk for noncardiac surgery
5. viability prior to revascularization therapy
6. evaluation of myocardial revascularization status pose CABG

Question 5

high risk patients after MI

Answer 5

• significant peri-infarct ischemia
• defect in different vascular territory (multivessel disease)
• significant lung uptake
• left ventricular aneurysm
• low ejection fraction < 40%

Question 6

hibernating myocardium

Answer 6

hypoperfused myocardium that is viable; meaning could be revascularizaed and isn’t scar tissue

Question 7

viability imaging

Answer 7

rest–redistribution thallium-201 perfusion imaging or F-18 FDG PET. F-18 FDG PET is the gold standard for evaluation of myocardial viability, although unlike thallium FDG-PET does not evaluate perfusion.

Question 8

static SPECT images from pure pefusion exams

Answer 8

Tc-99m sestamibi, rubidium-82 PET, or N-13 ammonia PET cannot distinguish between scar/hibernating scar tissue

Question 9

Thallium 201

Answer 9

cyclotron produced radionuclide with half life 73 hrs

decays by electron capture; emits characteristic xray 69-81 keV

Question 10

how does thallium work physiologically

Answer 10

acts like potassium analog and crosses into cells via ATP dependent Na K pump

Question 11

thallium in the heart

Answer 11

myocardial uptake directly proportional to myocardial perfusion

50% stenosis&raquo_space; perfusion defect with maximal exercise

undergoes redistribution with simultaneous cellular washout; ischemic myocardium washes out more slowly than normal myocardium

scar tissue will have persistent defect

Question 12

Technetium 99m sestamibi (Cardiolite); physiologic activity and redistribution?

Answer 12

enters myocardium via passive diffusion, binding to mitochondrial proteins ;

myocardial uptake proportional to perfusion

does not undergo redistribution; stays in the myocardium

Question 13

rubidium 82 is generated from? half life? physiology? type of stress test?

Answer 13

PET perfusion agent generated from strontium 82

half life 76 seconds so high doses can be administered; used as pharmacologic stress

acts as potassium analog, like thallium

Question 14

nitrogen 13 ammonia production? half life? physiology?type of stress test?

Answer 14

PET perfusion agent

cyclotron produced; must be produced on site due to short half-life

10 min half life

pharmacologic stress

Question 15

F18 FDG agent? viability?

Answer 15

positron emitting PET viability agent
half life 110 min; can’t be used for perfusion

can be used with sestabmibi perfusion study to evaluate viability; differentiate between hibernating myocardium

Question 16

basic components of cardiac perfusion study

Answer 16

stress (physical vs pharmacologic) and imaging

Question 17

cardiac exercise protocol

Answer 17

NPO for 6 hours to decrease splanchnic blood flow (liver/bowel uptake)
CCB and beta blockers held to allow target heart rate to be achieved
multistage treadmill (Bruce/modified Bruce protocol) and target heart rate is 85% of max heart rate (220bbp -age)

Question 18

pharmacologic vasodilators

Answer 18

dipyridamole stress, adenosine stress, regadenosonqq

Question 19

pharmacologic stress agent

Answer 19

dobutamine

Question 20

dipyridamole

Answer 20

adenosine deaminase inhibitor; allows adenosine to accumulate (potent vasodilator that can increase coronary blodo flow 3-5x)

critical coronary stenosis will not dilate in response to adenosine and will appear as perfusion defect; does not increase cardiac work or O2 demand

Question 21

dipyridamole antidote

Answer 21

aminophylline

Question 22

reversal agents for dipyridamole

Answer 22

caffeine and theophylline; should be held 24 hrs prior

Question 23

adenosine

Answer 23

identical physiologically t dipyridamole but rapidly effective

half life of 30 sec, no reversal agent

Question 24

regadenosine

Answer 24

adenosine receptor agonist; 2-3 min half life

easier to administer compared to adenosine due to universal dose IV injection

Question 25

dobutamine

Answer 25

beta 1 agonist that increase myocardial oxyen demand

used when adenosine contraindicated

Question 26

when is adenosine contraindicated

Answer 26

severe asthma, recent caffeine, COPD

Question 27

most common myocardial perfusion test

Answer 27

single day Tc99m sestamibi perfusion study

Question 28

protocol for Tc99m sestamibi perfusion study

Answer 28

rest images with 8-10 mCi Tc99m sestamibi

stress images after 20-30 mCi Tc99m sestamibi administered during peak exercise/pharmacologic stress

images performed 30 min after injection to allow liver activity to clear (no issues with redistribution, so imaging can be delayed)

Question 29

gated SPECT images vs perfusion images

Answer 29

gated SPECT shows wall motion at time of imaging

perfusion images show perfusion at time of injection

Question 30

PET perfusion vs SPECT

Answer 30

PET rest-stress myocardial perfusion has greast sensitivyt, specificity, accuracy

Question 31

best agent for quantifying myocardial blood flow

Answer 31

N13 ammonia preferred as rubidium has lower extraction fraction