1. Cardiac Perfusion Imaging…continued

2. PURPOSE
To evaluate regional myocardial perfusion during resting and under stress
To identify and localize areas of reversible ischemia or previous infarction in patients with chest pain, suspected of having coronary artery disease, previous coronary intervention, or previous abnormal ECG examination.

4. Example of an Infarct = fixed defect – apparent on Stress and Rest

6. Protocols Technetium agents 2-day stress-rest 1-day rest-stress

7. Protocols Thallium-201 Dual isotope Stress and delay
Thallium rest and Technetium stress performed on the same day

8. Mechanism of cellular labeling
Sestamibi and Myoview transport involves passive diffusion across the plasma and mitochondrial membranes
Thallium 201 behaves physiologically as a potassium analog. Uptake reflects perfusion and sodium-potassium pump activity.(Na-K pump)

9. Stressing Physical Pharmacologic Treadmill or Bicycle
Adenosine – vasodilator
Dipyridamole (persantine) – vasodilator
Dobutamine – inotropic agent

10. Treadmill or Bicycle
Physical

11. Exercise stress Absolute contraindications
High risk unstable angina.
Inadequately controlled congestive heart failure.
Uncontrolled hypertension (blood pressure >200/110 mm of Hg).
Uncontrolled cardiac arrhythmias
Severe symptomatic aortic stenosis

12. Exercise stress Absolute contraindications
Acute pulmonary embolism
Acute myocarditis or pericarditis
Acute aortic dissection
Severe pulmonary hypertension
Acute myocardial infarction (<4 days)

13. Indications for Early Termination of Exercise
Chest pain
Breathing difficulty
Fatigue.
Dizziness
Signs of poor perfusion (cyanosis and pallor).
Patient’s request to terminate the test.

14. Exercise stress
patients who cannot exercise adequately should undergo pharmacologic stress testing

15. Adenosine Dipyridamole (persantine) Dobutamine
Pharmacologic – cardiology presence
Adenosine Dipyridamole (persantine) Dobutamine

16. STRESS PROCEDURE Pharmacologic stress Procedure
Cardiology Fellows and ARNP are responsible for administration of pharmacologic agents.

17. Dipyridamole (Persantine) or adenosine stress testing Absolute contraindications
Asthmatic patients with ongoing wheezing
Severe COPD
Severe A-V block
Use of dipyridamole-containing medications
Caffeine within the last 12 hours
Low blood pressure
Unstable acute myocardial infarction

18. Indications for Early termination of Dipyridamole (Persantine) or adenosine infusion
Severe hypotension (systolic blood pressure _80 mm Hg).
Development of symptomatic, persistent second degree or complete heart block.
Wheezing.
Severe chest pain associated with ST depression of 2 mm or greater.
Signs of poor perfusion (pallor, cyanosis, cold skin).
Technical problems with the monitoring equipment.
Patient’s request to stop.

19. Dobutamine should not be used under the following circumstances
Recent (<1 week) myocardial infarction.
Unstable angina.
Significant left ventricular (LV) outflow tract obstruction.
Severe aortic stenosis.
Atrial tachyarrhythmias
History of ventricular tachycardia.
Uncontrolled hypertension
Aortic dissection or large aortic aneurysm

20. The indications for early termination of dobutamine are similar to those for exercise stress.
Termination for ventricular tachycardia or ST-segment depression is more likely with dobutamine than with other stressors.

21. Nuclear
protocol

22. Patient preparation for Stress Studies
Fast for 4 hours prior to the test
Avoid shunting of blood to the stomach
Precaution against vomiting during stress
If Pharmacologic stressing
No caffeine for 24 hours prior to the test

23. Day of test Identify the patient
Explain the procedure and possible side effects of the pharmacologic stress agent
Assess for pregnancy and breastfeeding
Obtain a signed consent form.
Start an I. V.
Administer the resting dose
Image according to protocol

24. Imaging Place patient supine on the imaging table
secure using the imaging pad straps
Make patient as comfortable as possible in order to minimize movement
Place patient’s arms overhead
use an arm support accessory if possible for support
Explain the need to breath normally, and the importance of not moving during the scan
Follow the acquisition protocol

25. DOSAGE
Technetium-99m Cardiolite® (Sestamibi) or Myoview™ (Tetrofosmin) Rest: 7-10 mCi Stress: mCi Thallium-201 Stress: 2 to 3 mCi

26. STRESS PROCEDURE Physical Exercise Procedure
The patient will be attached to a 12-lead ECG, and have an IV in place.
The patient will go through a series of graded levels of exercise lasting 3 minutes each (Bruce protocol, Modified Bruce protocol).
Record blood pressure, heart rate, and ECG every 1 minute.
The radiotracer should be injected at target heart rate and peak exercise 1 to 2 minutes prior to the conclusion of exercise.
Record radiotracer injection time.
The end point will be determined either by the patient’s inability to continue or at the direction of the attending cardiologist supervising the study.
Patients are assessed for stability before discharge

27. STRESS PROCEDURE Pharmacologic stress Procedure
Precautions/Restrictions: Cardiology Fellows and ARNP – are responsible for administration of pharmacologic agents.

28. PERSANTINE PROTOCOL
Dose of persantine is mg/kg/minute infused over 4 minutes.
Maximum dose is 60 mg
Patient should be told that mild chest discomfort, flushing, headache, nausea may be encountered.

29. PERSANTINE PROTOCOL Make sure IV aminophylline is available
Start a heparin lock or use existing one.
Draw the desired Persantine dose in a 30 cc Terumo syringe. Add Normal Saline to the same Terumo syringe to a total volume of 23 cc.
Insert the filled syringed into the Baxa Rapid Rate Infuser, attach the tip of the syringe to heparin lock. To start infusion, select Rate 1, slide the ON/OFF switch to ON.

30. PERSANTINE PROTOCOL
Monitor blood pressure, heart rate, and ECG every minute.
Inject nuclear agent three (3) minutes post persantine infusion.
If patient develops severe side-effects or severe chest pain, the effects of persantine can be reversed with IV aminophylline.
If possible, inject nuclear agent and wait 1 minute before reversing the adverse effects of persantine.
Dose of aminophylline is 125 to 250 mg IV injected at a rate of 50 mg per minute.

31. ADENOSCAN INFUSION PROTOCOL
In most cases, discontinuation of the adenosine infusion is followed by a prompt (< 1 minute) resolution or improvement of the adverse effect. In rare cases, aminophylline may be required, 50 to 125 mg IV .

32. DOBUTAMINE PROTOCOL Start IV line with angiocath gauge 22 or larger.
Mixed dobutamine 50 mg (4cc of Dobutamine 250mg/20 ml) in 96 cc of Normal Saline to make a total volume of 100 cc. prime the IV tubing and use an IVAC pump to regulate infusion based on the patients weight in kilogram (kg).
Make sure intravenous metoprolol is available.
Inform patient of possible side effects: chest discomfort/pain, palpitations, ect.

33. DOBUTAMINE PROTOCOL
Dobutamine is infused intravenously starting at 10 mcg/kg/min. and if tolerated, is increased every 3 minutes thereafter by 10 mcg/kg/min until a maximal dose of 40 mcg/kg/min. Target heart rate is 85% of the age-predicated maximal value.
Up to 1 mg of intravenous atropine may be given if an adequate heart rate is not achieved.
EKG, blood pressure, and heart are monitored during each stage.
The radioisotope is injected at peak dobutamine dose. Dobutamine infusion is continued for 1 minute after injection.
If the effects of dobutamine need immediate reversal (eg, symptomatic tachycardia), give metoprolol 5 mg IV, may repeat every 5 minutes three times (total of 15 mg)

34. Myocardial Viability
myocardial tissue that retains at least the minimal requirements for cell survival. 
cell membrane integrity
mitochondrial activity, and other metabolic functions. 

35. Myocardial Viability
These requirements for cell survival do not necessarily imply that the tissue is fully functional however.
viable cardiac tissue may exhibit poor to no contractile capability.
If its impairment results from reduced blood flow, it has the potential for recovery and for improved function following revascularization.

36. Myocardial Viability “Stunned myocardium“ "Hibernating myocardium"
viable tissue that recovers function spontaneously following a temporary severe reduction in blood flow.
"Hibernating myocardium"
viable tissue in a region of chronic coronary artery disease, whose contractile function only improves following restoration of blood flow to the myocardium.
it is thought that hibernating myocardium is the result of chronic repetitive "stunning" 

37. Myocardial Viability
The standard protocol for demonstrating viability consists of a rest injection of Thallium-201 chloride, followed by 15 min, 4 hour, and 24 hour views. 
An alternative protocol employs an initial injection during stress (exercise or pharmacological), followed by imaging at 15 min, 4 hours, with re-injection and imaging at 20 min, and if needed, additional imaging up to 24 hours later.

38. Myocardial Viability test rationale
There is a steady exchange of Tl-201 between the myocardial cells and the blood. 
Within 15 minutes after injection redistribution begins. 
Tl-201 will washout more quickly from normal cells than from abnormal cells.  The overall effect will be a steady relative decrease in uptake in normal tissue and increase in uptake in abnormal tissue over several hours.

39. Myocardial Viability test rationale
Hibernating tissue is identified as tissue that demonstrates reduced uptake immediately following initial injection, when compared to normal myocardium, but which on delayed images demonstrates normalization or "filling in".   

40. Technique: Tl-201 for viability
Dose: 4.0mCi of 201Tl-chloride I.V.
Rest-redistribution Inject at rest and begin imaging as soon as possible, re-image at 4 and if necessary at 24 hours
Stress-rest-reinjection
Inject at peak exercise and continue exercising for at least one minute after injection
Begin imaging 15 minutes after injection
delayed images at 4 hours. 
Re-inject mCi and re-image at approximately 15 minutes after injection;
later delayed imaging is optional.

41. Imaging Acquisition parameters (one or two headed cameras):
acquire frames,
20-45 sec/frame over a 180o arc from 45o RAO to 45o LPO.
64x64 acquisition matrix
LEHR collimator
Processing:  varies by the camera manufacturer
Zoom as needed 

42. SPECT processing
View ‘rotogram’ for patient motion. Correct if necessary
Transaxial reconstruction
Reorientation of image axis
Oblique reconstruction – apply proper filtering
Final report presentation

51. Gated perfusion imaging

60. PET 18Fluorine-FDG (2-fluoro-2-deoxyglucose)
18F-FDG is transported across cell membranes where it is phosphorylated to 18F-FDG-6-phosphate, and is then trapped within the viable myocardial cells, accumulating slowly.
Viability Testing Rationale
The myocardium in a normally perfused state is largely dependent on fatty-acid metabolism.
Fatty acid metabolism in myocytes is very sensitive to reduced perfusion and hypoxia, however.
As a result, ischemic cells switch their metabolism from beta oxidation of fatty acids toward anaerobic glucose metabolism.
The energy generated from anaerobic glucose metabolism may not be sufficient to maintain contractile function, but still may suffice for the preservation of cell membrane integrity and gradients.
Hypoperfused but viable tissue is defined as normal or increased regional cardiac FDG uptake in a region of reduced uptake of a flow tracer (using 99mTc-sestamibi, 99mTc-tetrofosmin, Rb-82, or N-13 ammonia).
Infarcted tissue will demonstrate reduced uptake of both a flow tracer and FDG (i.e. a matched defect of perfusion and metabolism).