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Gregg Furie, HMS IV Gillian Lieberman, MD The Role of SPECT MPI in the Evaluation of Coronary Artery Disease Gregg Furie, HMS IV Gillian Lieberman, MD Gregg Furie, HMS IV Gillian Lieberman, MD SPECT MPI SPECT • single-photon emission computed tomography MPI • myocardial perfusion imaging 2 Gregg Furie, HMS IV Gillian Lieberman, MD Goals • Basic principles of SPECT MPI • Interpretation of SPECT MPI • Correlate with anatomy and pathophysiology • Clinical utility of SPECT MPI in patients with or without known CAD 3 Gregg Furie, HMS IV Gillian Lieberman, MD Patient PB • History • 75 yo woman with hypertension and hyperlipidemia presents with chest pain and dyspnea on exertion • Strong family history of CAD • No history of obesity, smoking, diabetes • Goals for workup of CAD • Diagnosis • Risk stratification • Management 4 Gregg Furie, HMS IV Gillian Lieberman, MD What studies are available to evaluate PB, a patient with an intermediate to high pre-test probability of CAD? Gregg Furie, HMS IV Gillian Lieberman, MD Modalities for Evaluation of CAD Functional Studies Anatomical Studies • Non-invasive • Invasive • • • • • Exercise tolerance testing Stress echocardiography Stress SPECT MPI Stress PET MRI • Coronary angiography • IVUS • Non-invasive • EBCT • MSCT • MRA 6 Gregg Furie, HMS IV Gillian Lieberman, MD SPECT MPI was chosen as the initial study in PB’s workup for CAD. Why? 7 Gregg Furie, HMS IV Gillian Lieberman, MD Functional Studies • Assessment of hemodynamic consequences of CAD • Perfusion defects • Left ventricular dysfunction • Non-invasive • Well validated • ETT • Stress echocardiography • SPECT MPI • Widely available • Useful for diagnosis, risk stratification, and guiding management 8 Gregg Furie, HMS IV Gillian Lieberman, MD Anatomical Studies • Visualization of coronary vasculature and stenoses • Inform decisions regarding method of intervention • Only well validated and widely available modality (coronary angiography) is invasive • Associated morbidity and mortality • Gold-standard for diagnosis of CAD • Coronary angiography 9 Gregg Furie, HMS IV Gillian Lieberman, MD SPECT MPI versus other Functional Studies • Good test characteristics in diagnosis of CAD • Better than ETT • Roughly equivalent to stress echocardiography • • • • • • Can be used in patients with baseline ECG abnormalities Not operator dependent Validated role in risk stratification for patients with CAD Cost-effective Widely available Detection of early events in ischemic cascade 10 Gregg Furie, HMS IV Gillian Lieberman, MD The Ischemic Cascade ETT Echocardiography SPECT MPI modified from Heart. 2005; 91: 1110-1117 11 Gregg Furie, HMS IV Gillian Lieberman, MD How does SPECT MPI detect ischemia due to CAD? Gregg Furie, HMS IV Gillian Lieberman, MD SPECT: Basic Principles • Nuclear imaging study • Gamma particles detected by a rotating camera • Radionuclides • Thallium201 • Long half life (73 hours) → low doses • Low energy emitter → increased attenuation • Low doses and high attenuation → low resolution • Technetium99m • Short half life (6 hours) → high doses • High energy emitter → decreased attenuation • High doses and low attenuation → high resolution www.gehealthcare.com 13 Gregg Furie, HMS IV Gillian Lieberman, MD MPI: Basic Principles • Radionuclides taken up by perfused myocytes • Tl201: active transport across membrane by Na+/K+ ATPase • Tc99m sestamibi and Tc99m tetrofosmin: passive diffusion across cell and mitochondrial membranes • Identify areas of infarction or inducible ischemia by comparing perfusion in rest and stress states • Exercise or pharmacologically induced coronary artery vasodilation → proportionately less perfusion distal to stenoses → relatively low radionuclide uptake in myocardium distal to stenoses → relatively low signal from areas of low perfusion 14 Gregg Furie, HMS IV Gillian Lieberman, MD Impaired Coronary Flow Reserve Causes Decreased Perfusion Distal to Stenoses http://merck.micromedex.com/index 15 Gregg Furie, HMS IV Gillian Lieberman, MD SPECT MPI Protocols • Exercise vs. pharmacological • Exercise: Bruce protocol • Patients who can achieve ≥85% of maximal predicted heart rate • Exercise preferable since exercise capacity, symptoms, and ST segment changes provide additional prognostic information • Pharmacological • Vasodilators: adenosine, dipyridamole • Iono-/chronotrope: dobutamine • ECG gated vs. nongated • Gated protocol allows determination of LV function • Single isotope vs. double isotope • Rest and stress portions performed back-to-back in double isotope • Visual, semi-quantitative, or quantitative interpretation 16 Gregg Furie, HMS IV Gillian Lieberman, MD Cardiac Anatomy in SPECT MPI http://info.med.yale.edu/intmed/cardio/imaging/techniques/spect_anatomy/index.html 17 Gregg Furie, HMS IV Gillian Lieberman, MD Coronary Artery Territories from Hurst’s The Heart http://brighamrad.harvard.edu/education/online/Cardiac/ 18 Gregg Furie, HMS IV Gillian Lieberman, MD Patterns of Ischemia in Various Coronary Artery Territories in SPECT MPI Single-vessel disease A S A L I Multi-vessel disease S L I SA SA VLA VLA HLA HLA from Hurst’s The Heart from Hurst’s The Heart A: anterior wall L: lateral wall I: inferior wall S: septum 19 Gregg Furie, HMS IV Gillian Lieberman, MD High Risk Features on SPECT MPI • • • • • • Perfusion defects in multiple vascular territories Extensive hypoperfusion in one vascular territory LVEF < 40% Increased end-systolic and end-diastolic volumes Transient LV cavity dilation during stress Increased Tl201 lung uptake cavitary dilation stress rest 20 image courtesy of Dr. Kevin Donohoe Gregg Furie, HMS IV Gillian Lieberman, MD How is SPECT MPI used clinically for evaluation of CAD? Gregg Furie, HMS IV Gillian Lieberman, MD SPECT MPI for Diagnosis of CAD • Patient selection • Patients with intermediate pre-test probability of CAD based on historical and clinical factors • Patients with intermediate to high likelihood of CAD based on ETT or indeterminate ETT • Patients with baseline ECG abnormalities 22 Gregg Furie, HMS IV Gillian Lieberman, MD SPECT MPI for Risk Stratification in CAD • Identify patients with >1% likelihood of cardiac events • Cardiac death • Nonfatal MI • Progression of CAD • Use risk stratification to guide management • Patient selection • Intermediate or high risk by Framingham/ATPIII score • Patients with known CAD from prior cath or SPECT MPI who have been asymptomatic for >2 years or are symptomatic • Patients with prior revascularization who have been asymptomatic for >5 years or are symptomatic 23 Gregg Furie, HMS IV Gillian Lieberman, MD PB’s SPECT MPI Study • Dual isotope exercise SPECT MPI study • Performance • Exercised 4 minutes • Achieved 87% of maximal predicted heart rate • Study stopped due to dyspnea • No ECG changes • Strongly positive study at low level of exercise • LVEF 50% 24 Gregg Furie, HMS IV Gillian Lieberman, MD PB’s Stress SPECT MPI Study: Apical Ischemia Consistent with LAD Stenosis stress spin to assess for artifact or attenuation rest short axis stress rest vertical long axis stress rest gated view of LV function horizontal long axis images courtesy of Dr. Donohoe 25 Gregg Furie, HMS IV Gillian Lieberman, MD What are the implications of PB’s SPECT MPI study? Gregg Furie, HMS IV Gillian Lieberman, MD Diagnostic Implications • Test characteristics as compared to angiography • Sensitivity • Exercise: 87% • Vasodilator: 89% • Specificity • Exercise: 73% • Vasodilator: 75% • Normalcy rate: 91% • Corrects for decreased specificity due to referral bias. • People with positive studies are referred for coronary angiography while people with negative studies generally are not, thus increasing the apparent proportion of false positive SPECT MPI studies. 27 Gregg Furie, HMS IV Gillian Lieberman, MD Prognostic Implications • Excellent negative predictive value • 0.5% annual cardiac event rate in patients with normal studies • Specific patient populations have worse prognosis for same degree of perfusion defect • • • • Advanced age Known CAD Diabetics Pharmacological stress tests 28 Gregg Furie, HMS IV Gillian Lieberman, MD Severity of Perfusion Defect is Correlated with Likelihood of Future Cardiac Events from Fuster V et al. Hurst’s The Heart; Eleventh Edition. The McGraw-Hill Companies, Inc. 2004 29 Gregg Furie, HMS IV Gillian Lieberman, MD Poststress Ejection Fraction is Correlated with Survival Ejection fraction ≥45% Ejection fraction <45% from Fuster V et al. Hurst’s The Heart; Eleventh Edition. The McGraw-Hill Companies, Inc. 2004 30 Gregg Furie, HMS IV Gillian Lieberman, MD Implications for Management • Patients with no or mild ischemia benefit from medical management over revascularization • Patients with moderate to severe ischemia (>10% of myocardium) benefit from revascularization over medical management • Only patients with inducible ischemia benefit from revascularization • Selective referral of patients to catheterization is cost-effective 31 Gregg Furie, HMS IV Gillian Lieberman, MD Implications of PB’s SPECT MPI Study • Diagnosis • High post-test probability of CAD • Risk Stratification • >1% annual probability of a major cardiac event • Management • Likely to benefit from revascularization 32 Gregg Furie, HMS IV Gillian Lieberman, MD Companion Patient’s Coronary Angiogram Complete occlusion of proximal LAD Stented LAD Stent LAD LAD LCX LCX http://www.path.utah.edu/ http://www.path.utah.edu/ 33 Gregg Furie, HMS IV Gillian Lieberman, MD PB’s Post-Stent Stress SPECT MPI Study: Resolution of Inducible Apical Ischemia Before revascularization After revascularization stress rest short axis short axis stress vertical long axis rest vertical long axis stress horizontal long axis rest horizontal long axis images courtesy of Dr. Kevin Donohoe 34 Gregg Furie, HMS IV Gillian Lieberman, MD Conclusion • SPECT MPI identifies regions of myocardial ischemia with decreased perfusion and LV dysfunction • SPECT MPI has a well validated role in diagnosis and risk stratification in patients with CAD • Risk stratification with SPECT MPI can be used to costeffectively guide management of patients with CAD 35 Gregg Furie, HMS IV Gillian Lieberman, MD References • • • • • • • • • • • Brindis RG, Douglas PS, Hendel RC, Peterson ED, Wolk MJ, Allen JM, Patel MR, Raskin IE. ACCF/ASNC appropriateness criteria for single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI): a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group and the American Society of Nuclear Cardiology. J Am Coll Cardiol 2005;46:1587– 605. Clark AN and Beller GA. The present role of nuclear cardiology in clinical practice. Q J Nucl Med Mol Imaging. 2005; 49: 43-58 Fuster V et al. Hurst’s The Heart; Eleventh Edition. The McGraw-Hill Companies, Inc. 2004 Klocke FJ, Baird MG, Bateman TM, Berman DS, Carabello BA, Cerqueira MD, DeMaria AN, Kennedy JW, Lorell BH, Messer JV, O’Gara PT, Russell RO Jr, St. John Sutton MG, Udelson JE, Verani MS, Williams KA. ACC/AHA/ASNC guidelines for the clinical use of cardiac radionuclide imaging—executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASNC Committee to Revise the 1995 Guidelines for the Clinical Use of RadionuclideImaging). Circulation. 2003;108:1404 –1418. Loong CY and Anagnostopolous C. Diagnosis of coronary artery disease by radionuclide myocardial perfusion imaging. Heart. 2004; 90: 2-9 Mannting F et al. Atlas of Myocardial Perfusion SPECT. http://brighamrad.harvard.edu/education/online/Cardiac/ Micromedex. http://merck.micromedex.com/index Sabharwal NK and Lahiri A. Role of myocardial perfusion imaging for risk stratification in suspected or known coronary artery disease. Heart. 2003; 89:1291-1297 Schuijf JD et al. Cardiac imaging in coronary artery disease: differing modalities. Heart. 2005; 91: 1110-1117 University of Utah, Department of Pathology. http://www.path.utah.edu/ Yale University School of Medicine. http://info.med.yale.edu/intmed/cardio/imaging/techniques/spect_anatomy/index.html 36 Gregg Furie, HMS IV Gillian Lieberman, MD Acknowledgements Dr. Kevin Donohoe Dr. Gillian Lieberman Pamela Lepkowski Larry Barbaras 37
