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CLINICAL RESEARCH: CARDIAC IMAGING

Long-Term Prognostic Value of ¹³N-Ammonia Myocardial Perfusion Positron Emission Tomography

Added Value of Coronary Flow Reserve

Bernhard A. Herzog, MD^_*, Lars Husmann, MD^_*, Ines Valenta, MD^_*, Oliver Gaemperli, MD^_*, Patrick T. Siegrist, MD^_*, Fabian M. Tay, MD^_*, Nina Burkhard, MD^_*, Christophe A. Wyss, MD^_* and Philipp A. Kaufmann, MD^_*,,_*

^_* Cardiac Imaging Section, University Hospital Zurich, Zurich, Switzerland
Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland

Manuscript received October 7, 2008; revised manuscript received January 30, 2009, accepted February 17, 2009.

^_* Reprint requests and correspondence: Dr. Philipp A. Kaufmann, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, CH-8091 Zurich, Switzerland (Email: pak{at}usz.ch).

Objectives: The goal of this study was to assess the predictive value of myocardial perfusion imaging with ¹³N-ammonia positron emission tomography (PET) and coronary flow reserve (CFR) on long-term prognosis in patients with suspected myocardial ischemia.

Background: No prognostic data exist on the predictive value of CFR and ¹³N-ammonia PET.

Methods: Perfusion and CFR were assessed in 256 patients using ¹³N-ammonia PET, and follow-up was obtained in 245 (96%) patients. Sixteen early revascularized patients were excluded and 229 were assigned to normal versus abnormal perfusion or normal versus abnormal CFR (<2.0). Major adverse cardiac events (MACE) (cardiac death, nonfatal myocardial infarction, late revascularization, or hospitalization for cardiac reasons) were assessed using the Kaplan-Meier method. Cox proportional hazard regression was used to identify independent predictors for cardiac events.

Results: During follow-up (5.4 ± 2.2 years), 78 patients had at least 1 cardiac event, including 29 cardiac deaths. Abnormal perfusion (n = 126) was associated with a higher incidence of MACE (p < 0.001) and cardiac death (p < 0.05). In patients with normal perfusion, abnormal CFR was independently associated with a higher annual event rate over 3 years compared with normal CFR for MACE (1.4% vs. 6.3%; p < 0.05) and cardiac death (0.5% vs. 3.1%; p < 0.05). In abnormal perfusion, CFR remained predictive throughout the 10-year follow-up (p < 0.001).

Conclusions: Perfusion findings in ¹³N-ammonia PET and CFR are strong outcome predictors. CFR allows further risk stratification, suggesting a "warranty" period of 3 years if normal CFR is associated with normal perfusion. Conversely, in patients with abnormal perfusion, an impaired CFR has added value for predicting adverse outcomes.

Key Words: coronary flow reserve • positron emission tomography • ¹³N-ammonia • myocardial perfusion imaging • outcome

Abbreviations and Acronyms   CABG = coronary artery bypass grafting   CAD = coronary artery disease   CFR = coronary flow reserve   MACE = major adverse cardiac advents   MBF = myocardial blood flow   MPI = myocardial perfusion imaging   PCI = percutaneous coronary intervention   PET = perfusion emission tomography   SPECT = single-photon emission computerized tomography   SSS = summed stress score

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