1. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
The Elusive Role of Myocardial Perfusion Imaging in Stable Ischemic Heart Disease: Is ISCHEMIA the Answer?
Joe X. Xie, MDa; David E. Winchester, MDb; Lawrence M. Phillips, MDc; Rory Hachamovitch, MDd; Daniel S. Berman, MDe; Ron Blankstein, MDf; Marcelo F. Di Carli, MDf; Todd D. Miller, MDg; Mouaz H. Al-Mallah, MDh; Leslee J. Shaw, PhDa
aDepartment of Cardiology, Emory University School of Medicine; bDepartment of Cardiology, University of Florida College of Medicine; cLeon H. Charney Division of Cardiology, New York University School of Medicine; dDepartment of Cardiology, Cleveland Clinic; eDepartment of Cardiology, Cedars-Sinai Medical Center; fCardiovascular Imaging Program, Departments of Medicine and Radiology, Brigham and Women’s Hospital; gDepartment of Cardiology, Mayo Clinic; hKing Saud bin Abdulaziz University for Health Sciences, King Abdullah International Medical Research Center;
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2. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
BACKGROUND
1- Ischemia has played a central role within guideline-supported diagnostic and therapeutic pathways of care for patients with stable ischemic heart disease.
2- However, randomized trials have consistently failed to show significant benefits in hard outcomes when using ischemic burden as a target to guide coronary revascularization.
3- Inherent limitations in prior investigations have created the impetus for reassessing current ischemia-driven management strategies.
4- In this review, we highlight existing evidence on the prognostic value of ischemia, limitations of previous trials and gaps in knowledge that have led to the ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches) trial, and its implications for the field of nuclear cardiology.
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3. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
METHODS
Study type: Review of pertinent observational and randomized control trials on myocardial ischemia
Study subjects: Patients with myocardial ischemia from aforementioned studies
Study endpoints: Variable, but typically death and/or myocardial infarction
Study variables: Variable
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4. RESULTS ? Figure 1. Current Ischemia-Directed Pathways of SIHD Care
Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
RESULTS
Suspected SIHD
Functional Testing1
Ischemic Burden
Optimal Medical Therapy
Invasive Coronary Angiography
High Risk Anatomy2
Figure 1. Current Ischemia-Directed Pathways of SIHD Care ?
Coronary Revascularization
Refractory Symptoms
Improve Survival
Patients with suspected SIHD are recommended to undergo additional diagnostic testing with either noninvasive modalities (if low-intermediate pretest probability) or directly to invasive coronary angiography (if high pretest probability); catheterization would also be supported for patients with concerning stress test findings. Following the results of noninvasive and invasive testing, coronary revascularization is reserved for patients with high risk coronary anatomy to improve survival or for those with angina refractory to maximal medical therapy. However, it remains unclear whether ischemic burden should also be used to guide revascularization decisions.
1Noninvasive anatomic testing would also be a guideline-supported alternative to functional testing in appropriate candidates; 2High risk anatomy includes obstructive left main disease or multivessel epicardial disease with involvement of the proximal left anterior descending artery; SIHD: stable ischemic heart disease
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5. Figure 2. ISCHEMIA Study Flow Diagram
Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
Figure 2. ISCHEMIA Study Flow Diagram
Stable Ischemic Heart Disease
with Moderate-Severe Ischemia
Blinded CCTA
(Rule Out Obstructive Left Main or No Obstructive Disease)
Patient
Late Screen Failure
Ineligible
Patient
Eligible
Randomize
Invasive Arm:
Catheterization + Revascularization + OMT
Conservative Arm:
OMT only; Catheterization reserved for OMT failure
Primary Endpoint: Composite of Cardiovascular Death or Nonfatal MI
Extrapolated from ISCHEMIA trial design ( Stable patients with documented moderate-severe ischemia will undergo blinded CCTA (estimated glomerular filtration ≥60 mL/min/1.73m2) to rule out obstructive left main or no obstructive coronary artery disease. Eligible patients will then be randomized to either an invasive strategy with cardiac catheterization, revascularization, and OMT or a conservative strategy of OMT alone with catheterization reserved for OMT failure. Patients will be followed for a primary endpoint of cardiovascular death or MI.
CCTA: coronary computed tomography angiography; ISCHEMIA: International Study of Comparative Health Effectiveness with Medical and Invasive Approaches; MI: myocardial infarction; OMT: optimal medical therapy
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6. Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology
CONCLUSIONS
1- A disconnect exists between observed reductions in ischemic burden and expected reductions in adverse events.
2- However, prior study populations were at low cardiovascular risk as many patients had only minimal ischemia on functional testing at baseline.
3- There still remains uncertainty regarding the best treatment strategy for patients with moderate to high risk ischemia for which the current ISCHEMIA trial will hopefully provide clarity.
4- The results from ISCHEMIA may not only reshape current SIHD guidelines, but more broadly, define the role of MPI and functional testing in the management of SIHD.
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