STRESS TEST AND RNI

• Also known as


  Nuclear stress test
• Myocardial perfusion imaging


  • Visualize distribution of radiopharmaceuticals that extracted rapidly from coronary arterial blood into myocardium
  • The distribution is proportional only to myocardial perfusion and viable myocardial cells combined with exercise or pharmacological stress
• Myocardial perfusion scan


  • Provide excellent information regarding existing coronary artery disease and anticipated future events
• Indications for myocardial perfusion scan

  • Detection and evaluation of coronary artery disease with assessment of the extent the severity of myocardial ischemia or infarction
  • Assessment of myocardial viability
  • Evaluation of possible candidates for coronary bypass surgery or angioplasty
  • Evaluation of patients with clinical indications of myocardial infarction, chest pain, and SOB
  • Evaluation of patients showing abnormal biochemical findings like elevated creatinine phosphokinase (CPK), lactate dehydrogenase or positive cases for trophonin and myoglobin
  • Detection and evaluation of viable/hibernating myocardial tissue
  • Evaluation of effects of angioplasty and bypass surgery on myocardial perfusion with pre- and post intervention studies (blood flow)
  • Evaluation of prognosis
• Indications for myocardial perfusion scan

  • Patient experiencing chest pain
  • Frequent ventricular arrhythmias at rest
  • Patients with very high blood pressure
  • Patients allergic to drugs used for pharmacological stress
  • Third degree heart block
  • Severe valvular disease, specially aortic valve stenosis
• Equipments required for myocardial perfusion scan

  • SPECT- capable gamma camera, preferably dual-headed with LEHR, GP collimator
  • Treadmill or bicycle ergo meter, or
  • Pharmacological stressing agent (adenosine or dobutamine)
  • 3 or 12 ECG monitor
  • Resuscitation facilities inc. defibrillator
  • Readily availability of drugs (aminophylline and lignocaine)

  
• Radiopharmaceuticals used


  • Thallium (TI-201 thallus chloride)
  • Tc-99m MIBI
  • Tc-99m tetrofosmin
• Adult dose range


  • Tc-99m sestamibi or Tc-99m tetrofosmin → 20-30 mCi (740-1110 MBq)
  • TI-201: 2-4 mCi (74-148 Mbq)
• Patient preparation


  1. Light breakfast 4-6 hours prior to the test. Avoid caffeine in the last 24 hours. No cardiac medication on the day of the test if possible. Beta blockers maybe continued. Shave and wipe chest with alcohol. Prepare patients with a 10 or 12 lead ECG set up

  2. Start IV set up with patency ensured

  3. Obtain baseline BP and record/attach the patient to non-invasive blood pressure (NIBP) if possible
• Protocol using Tc-99m MIBI or Tc-99m-tetrofosmin


  1. Initiate pharmacological stress or exercise. At max. stress level, administer dose IV and continue stress protocol for 1 min, post ejection (to allow uptake in myocardium). After 10-30 min post injection, give milky drink (to promote biliary clearance)

  2. Position patient comfortably, if possible, arms above head. Set camera head 180 degrees orbit from RAO 45 to LPO 45. With dual-headed systems, this can be achieved with the heads at 90 degrees to each other to minimize the amount of camera rotation

  3. Adjust matrix size and zoom to give pixel size of 3-4 mm

  4. Acquire data in 30-40 projections (30 minutes) for single, 15 minutes for dual-headed systems

  5. View projections in cine before allow patient to leave the room (check for significant movement)

  6. Stress study normal → may not required for a rest study, otherwise patients need to return preferably 2-7 days after the stress study to repeat scan at rest
• Thallium stress/rest scintigraphy


  1. Initiate pharmacological stress or physical exercise. At max. stress level, administer 80 MBq Thallium dose IV. Continue stress protocol for 1 min, post ejection (to allow uptake in myocardium). Image after 5 minutes.

  2. Repeat image at rest, 3-4 hours after redistribution period. During this period, patient shouldn't allowed to eat
• Thallium stress/rest scintigraphy for myocardial viability


  1. If fixed defects are seen in exercise and rest images, and assessment of myocardial viability or hibernation is required, either:

  2. Administer a second smaller dose of 40 MBq TI-201 with nitroglycerine prior to the injection. Image 20-30 minutes later. If defect still persist, image again at 18-24 hours. 30% of fixed defects at 3-4 hours image, may show reversibility in 18-24 hours image

  3. Perform on a separate day, rest redistribution study with 80 MBq TI-201 and nitroglycerine. Image at 20-30 minutes and 3-4 hours.
• Stress protocols


  1. Physical exercise: Treadmill or bicycle. Place pt on the equipment with 10/12 lead ECG. Run baseline ECG. Start exercise. Monitor heart rate, BP, ECG changes untill target heart rate is achieved (>85% of 220- age of pt). Radiotracer is injected after target HR is achieved. Maintain exercise level for 60-90s after injection

  2. Pharmacological stress: Stress with dobutamine. Stress with dipyramidol: Apply dose slowly, using pump over 4 min, wait 3-4min more. Inject radiotracer.
• MUGA study (aka radionuclide ventriculography)


  Gamma camera images of labeled blood inside the chambers of the heart, gated to pt's ECG. Changes in counts, detected by the camera in cardiac chambers, represent chamber volume and enables quantification of EF. Images of chamber changes volume can be viewed as cine giving information about wall motion.
• Ejection fraction (EF)


  A measurement (in %) of how much blood the left ventricle pumps out with each contraction.
• Indications for MUGA scan

  • Calculation of L ventricular, sometimes R ventricular EFs
  • Evaluation of wall motion abnormality
  • Evaluation of functional status of heart prior to surgery, chemotherapy or RT
  • Evaluation cause of dyspnea (cardiac / pulmonary)
  • Diagnosis and prognostication of CAD
  • Detection and evaluation of vulvular dysfunction
  • Evaluation of cardiomyopathy
  • Evaluation of pre-cardiac and post-cardiac transplantation
• Contraindications for MUGA scan

  • Presence of acute chest pain
  • Patients with known severe arrhythmia
  • Patients allergic to pyrophosphates
• MUGA scan equipment


  • Gamma camera with LE, HR or LEAP collimator
  • 30 degrees slant hole collimators also preferred
  • Computer settings: 16 frames/sec, 20-50 ms/frame, matrix 64x64, 3M counts
• Radiopharmaceutical for MUGA


  Tagged RBC by pyrophosphate or stannous chloride in combination with Tc-99m pertechnatate. Dose: adult 20-30 mCi (740-1110 MBq)
• Patient preparation for MUGA

  Discontinue cardiac medications and caffeine at least 4 hours prior. Avoid oral food 2-8 hours prior.
• MUGA procedure - stress study

  Prepare pt at rest. Position pt in exercise device, connect ECG and position camera for test as per protocol. Ensure camera position to have a best septal separation. Start exercise with 25w or 50w, increase workload till adequate heart rate is reached. Start camera and start collect up to 3M counts. Obtain blood pressure and record ECG at each level of exercise.
• MUGA procedure - processing

  Draw ROI manually or automatically on computer. Calculate EF = (ED-ES)/ED x 100. Calculate SV (stroke volume) = ED (end diastolic)-ES(end systolic). Calculate CO (cardiac output) in ml = SV x HR (heart rate).