Comparison of Positron Emission Tomography Measurement of Adenosine-Stimulated Absolute Myocardial Blood Flow Versus Relative Myocardial Tracer Content for Physiological Assessment of Coronary Artery Stenosis Severity and Location
Mohammad M. Hajjiri, MD*,
Marcia B. Leavitt, BA*,
Hui Zheng, PhD ,
Amy E. Spooner, MD*,
Alan J. Fischman, MD, PhD ,
Henry Gewirtz, MD*,*
* Cardiology Division, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
Biostatistics Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
Department of Nuclear Medicine, Shriner Burns Hospital, Boston, Massachusetts
* Reprint requests and correspondence: Dr. Henry Gewirtz, Cardiac Unit/Yawkey 5E, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 (Email: hgewirtz{at}partners.org).
Objectives: This study tests the hypothesis that absolute measurement of adenosine (Ado)-stimulated myocardial blood flow (MBFado) is superior to measurement of relative tracer uptake for identification of hemodynamically significant coronary artery disease (CAD).
Background: Positron emission tomography measurement of absolute myocardial blood flow (MBF) (13N-ammonia) with Ado has the capability to more accurately assess hemodynamic severity of CAD than measurement of relative tracer content (TC) (nCi/ml) during Ado, which by definition depends on at least 1 normal zone to which others are compared.
Methods: A total of 27 patients (20 male, 58 ± 11 years, mean ± SD) with known or suspected CAD and 21 normal subjects (13 male, 38 ± 10 years) were studied. Parametric (K1) MBF images and TC sum images were analyzed. A stenosis  70% defined significant CAD. The receiver-operator characteristic curve (ROC) analysis area under the curve (AUC) compared MBF and TC results. Cut-point analysis for sensitivity, specificity, and accuracy showed the best MBF criteria for CAD as MBFado <1.85 ml/min/g and the best TC as <70% maximum. The myocardial blood flow reserve ratio (MBFR) (optimal <2.0x) also was studied.
Results: The ROC analysis of PET parameters showed that MBFado was superior to <70% maximum uptake for CAD detection (n = 144 vessels; AUC 0.900 vs. 0.690, respectively, p < 0.0001) and was marginally greater than MBFR (0.856; p = 0.10). For CAD cut-point analysis, MBFado accuracy exceeded TC (0.84 vs. 0.72, respectively, p = 0.005), as did sensitivity (0.81 vs. 0.48, respectively; p = 0.001). Specificity of MBFado for CAD classification (0.85) was comparable to TC (0.82; p = NS). Sensitivity, specificity, and predictive accuracy for MBFR were 0.62, 0.85, and 0.79, respectively. The difference in specificity was not significant versus MBFado. However, MBFado was more sensitive than MBFR (p = 0.01). The difference in predictive accuracy was borderline (p = 0.06) in favor of MBFado.
Conclusions: Measurement of Ado-stimulated absolute MBF is superior to relative measurement of myocardial tracer retention for identification of CAD and can be accomplished with a single MBFado measurement.
Key Words: PET • myocardial blood flow • coronary artery disease
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Abbreviations and Acronyms
| | Ado = adenosine | | AUC = area under the curve | | CAD = coronary artery disease | | LAD = left anterior descending coronary artery | | LCX = left circumflex coronary artery | | MBF = myocardial blood flow | | MBFado = adenosine-stimulated myocardial blood flow | | MBFR = myocardial blood flow reserve ratio | | MPI = myocardial perfusion imaging | | PET = positron emission tomography | | RCA = right coronary artery | | ROC = receiver-operator characteristic curve | | TC = tracer content |
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