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Nuclear cardiology methods in routine clinical practice

Nuclear cardiology methods in routine clinical practice. Materials for medical students. Lang O., Kamínek M. Dept Nucl Med, School of Medicine, Praha, Olomouc. Nuclear cardiology. Set of non-invasive mostly imaging diagnostic methods of the cardiovascular system

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Nuclear cardiology methods in routine clinical practice

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  1. Nuclear cardiology methods in routine clinical practice Materials for medical students Lang O., Kamínek M. Dept Nucl Med, School of Medicine, Praha, Olomouc

  2. Nuclear cardiology • Set of non-invasive mostly imaging diagnostic methods of the cardiovascular system • Huge expansion during last 30 years, in Czech rep. during last 10 years • Examination of venous system of lower extremities and lung perfusion are included

  3. Seminar includes • Imaging in nuclear cardiology (NC) • NC methods • Myocardial perfusion • Myocardial viability • Heart function • Examination of pulmonary embolism • New trends

  4. Ways of imaging in NC • Detectors of ionizing radiation – gamma cameras • Source of radiation inside the patient body - radiopharmaceutical, tracer • Ways of distribution - perfusion, metabolic process, receptors, etc. • Source of information - ionizing photon (gamma) • Digital images - processing, archiving, transfer • planar, tomographic • SPECT (transversal), PET (coincidence)

  5. Data collection by gamma cameras

  6. PET camera

  7. Way of tomography - SA slices

  8. Other tomographic slices

  9. Parts of left ventricle myocardium Legenda: 1 - apex 2 - anterior wall 3 - lateral wall 4 - inferior wall 5 – septum SA VLA HLA Pollar map

  10. Heart examination • Myocardium imaging • perfusion during stress and rest (80%) • viability • necrosis, innervation, ischemia • Mechanical function assessment • steady-state ventriculography (multigated - MUGA) • Angiocardiography (first-pass) • non-imaging systems

  11. Myocardial perfusionrate of NC examinations

  12. Why stress? Pathophysiology of CAD Hemodynamic effect of coronary stenoses Collaterals Ischemic cascade

  13. Rest myocardial perfusion in CAD • Physiological compensatory arteriolar dilatation in the region supplied by narrowed artery • Blood flow remains the same as in the region supplied by normal artery • Radiopharmaceutical distribution remains homogenous

  14. Stress myocardial perfusion in CAD • Arteriolar dilatation in the bed of normal artery for blood flow increase • Blood flow through the normal artery increases • Arteriolae in the bed of narrowed artery are already dilated - no further dilatation can occure, so blood flow remains as in the resting state • Non-homogenous perfusion (radiopharmaceutical distribution) as a result

  15. Ischemic cascade

  16. Type of stress • Mechanical dynamic stress • ergometer (bicycle), tread-mill • Pharmacological stress • vasodilators - adenosine, dipyridamole • positively inotropic drugs - dobutamine, arbutamine • atropine • Combined of all mentioned above

  17. Ergometer • Goal is to achieve at least 85% of maximal heart rate (220-age) or double-product more than 25000 • Increase by 50 (25) W after every 3 (2) minutes • Rate of pedalling 40 to 60 per minute • Radiopharmaceutical injection at peak stress • distribution proportional to blood flow at the time of injection • Maintain this stress for at least 1 to 2 minutes • Withdraw betablockers (BB), patient fasting

  18. Dipyridamole stress • Acts indirectly via the adenosin (block its removal) • Dilates coronary resistant arteries - it makes possible to assess coronary flow reserve • Maximal effect is achieved 3 to 4 minutes after stopping the 4 minutes infusion • Its effect can be stopped with theophyllines • withdraw them before the test • Usually used in patients using BB, unable to exercise, with LBBB

  19. Contraindications to perform dipyridamole stress • Patients with chronic obstructive pulmonary disease treated by theophyllines (dobutamine can be used) • Patients should avoid tee, cofee, cola before the test to prevent false negative results (insuficient or no vasodilation)

  20. Dipyridamole stress

  21. Side effects of dipyridamole • They occures in approximately 30% of patients • headache • neck tension • warm feeling • dizziness • nausea, hypotension • chest pain (very seldom)

  22. Performance of dipy stress • Dipyridamole applied by intravenous infusion • Usual dosage is 0.56 (0.75; 0.84) mg/kg • Dose is diluted with saline to 50 ml • to prevent local side effects (arm pain) • Duration of infusion is 4 minutes • If the patient is unable of any physical stress, tracer is injected 3-5 min. after stopping infusion

  23. Combined stress • Dipyridamole is infused according to previous rules to sitting or lying patient • 3 to 6 min. bicycle stress follows • better image quality • lower frequency of side effects • can be performed even in patients with hypotension • 1 to 2 min. before stopping bicycle stress radiopharmaceutical is injected

  24. Test arrangement • Right arm - tourniquet of tonometer • Left arm - infusion through the cannula • Saline is connected after stopping dipyridamole for venous link for the case of any complication • Patient is sitting on the ergometer, ECG electrodes according to Mason and Likar

  25. Dobutamine stress • If dipyridamole is contraindicated • Dobutamine intravenously in the dose of 5 to 10 g/kg/min., increase every 3 min. up to dose of 40 g/kg/min. • Monitore ECG, HR and BP, if 85% of maximal HR is not achieved, add Atropine • Radiopharmaceutical is injected 1 to 2 min. before stopping stress • Contraindications: ventricular tachycardia, severe hypertension, hypertrophic cardiomyopathy

  26. Myocardial perfusion protocols • One-day (Tl, Tc, FDG) - two-days (Tc, FDG, Tl) • Stress - rest or rest - stress (Tc, Tl-Tc) • Stress - (redistribution) - reinjection (Tl) • Stress - metabolism (Tc - FDG) • Stress - rest - metabolism (Tc, FDG) • Rest - redistribution - (late redistribution) (Tl) • Rest - metabolism (Tc - FDG)

  27. Radiopharmaceuticals for perfusion Tl-201 chlorid or Tc-99m MIBI for SPECT, N-13H3 or H2O-15 for PET Distribution in the myocardium rely on cells perfusion Tl-201 has redistribution Tc-99m MIBI does not have redistribution

  28. Data processing • Quantitative analysis of myocadial perfusion distribution • CEqual™ - uses pollar maps for standardization and comparison with „normals“ • Gated (synchronized) tomography (QGSPECT) • divides cardiac cycle into 8 periods • makes possible to evaluate mechanical function of the heart (ejection fraction - EF)

  29. Quantification of perfusion

  30. QGSPECT

  31. Basic patterns of myocardial perfusion imaging (MPI) • Normal finding • homogenous perfusion during stress as well as rest • Sign of ischemia • perfusion defect during stress which disappears on rest (reversible defect) • Sign of scar • perfusion defect on stress and rest (fixed defect) • Sign of ischemia and scar • combination of both mentioned above

  32. Main clinical indication of MPI • Detection of ischemic heart disease • Hemodynamic effect of coronary stenoses • Prognosis of patients with konwn CAD • Evaluation of revascularization effect and detection of restenosis • Risk stratification of patients after MI • Myocardial viability • Acute coronary syndromes • Cardiac risk in non-cardiac surgery

  33. Detection of CAD

  34. 66y old pt, atypical chest pain, ECHO difuse wall motion abnormality, Ao+mi reg, sci isch. of inferior wall, EF 40%

  35. Detection of CAD basic parameters • Planar Tl-201 scintigraphy - qualitative evaluatioin • Group of 4.678 pts - sens. 82%, spec. 88% • pts without MI - sens. 85% • pts after MI - sens. 99% • one-vessel disease - sens. 79% • two-vessel disease - sens. 88% • three vessel disease - sens. 92%

  36. Detection of CADbasic parameters • Referral bias • only patients with positive scintigraphy are referred to coronarography • patients with normal scintigraphy are not catheterized • higher sensitivity but decline of specificity • Normalcy rate (used instead of specificity) • negative scintigraphy in patients with very low pretest probabilty of CAD based on history, symptoms, stress ECG

  37. Detection of CAD basic parameters • SPECT Tl-201 scintigraphy • Group of 1.527 pts - sens. 90%, spec. 70% (more false positives due to artefacts), normalcy rate 89% • pts without MI - sens. 85% • pts after MI - sens. 99% • one-vessel disease - sens. 83% • two-vessel disease - sens. 93% • three-vessel disease - sens. 95%

  38. Detection of CAD basic parameters • SPECT Tl-201 scintigraphy • Group of 704 pts • stenosis of 50 to 70% - sens. 63% • stenosis of 75 to 100% - sens. 88% • Dipyridamole stress (1.272 pts) • sens. 87% • spec. 81%

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