Canadian and American researchers observed a "significant reduction" in cardiac events when using FDG-PET rather than standard methods of care to determine which patients receive revascularization therapy, according to research published in the April issue of the Journal of Nuclear Medicine.
Researchers from the National Cardiac PET Centre in Ottawa, Ontario, and the University of Washington in Seattle say their results suggest that outcomes may improve for heart failure patients in healthcare facilities with ready access to FDG. The lead author of the study is Dr. Robert Beanlands, chief of cardiac imaging at the University of Ottawa Heart Institute (JNM, April 2010, Vol. 51:4, pp. 567-574).
Previous research has shown FDG-PET to be the most sensitive noninvasive way to predict left ventricular functional recovery after coronary revascularization and that it can help identify patients at high risk for cardiac events.
The PET and Recovery Following Revascularization (PARR 2) trial also showed fewer cardiac events with information collected through FDG-PET, when compared to standard care. However, the authors noted, the PARR 2 trial was "inconclusive regarding primary outcomes."
Ottawa-FIVE
The researchers took a subgroup of PARR 2 and referred to it as the Ottawa-FIVE (FDG-PET Imaging of Myocardial Viability in an Experienced Center with Access to FDG and Integration With Clinical Management Teams).
Patients in the Ottawa-FIVE subgroup had met PARR 2 enrollment criteria by being considered for revascularization or revascularization workup, transplantation workup, or heart failure workup. They also were patients under consideration for FDG-PET viability imaging.
Patients also were included in Ottawa-FIVE if they were older than 18 years of age, and had an ejection fraction of 35% as documented by radionuclide angiography, left ventricular angiography, or echocardiography. They also had known or highly suspected coronary artery disease based on a coronary angiogram, previous revascularization, or previous myocardial infarction, or they had stress perfusion imaging which confirmed scarring with or without ischemia.
From the patient sample, the researchers randomly enrolled 56 patients into a PET group and 55 patients into a standard-care group. Two patients later dropped out of the PET group, leaving 54 patients with follow-up results.
Myocardium viability
Patients received radionuclide angiography at baseline, while FDG-PET was performed after an oral glucose load for nondiabetic patients and with an insulin-euglycemic clamp for diabetic patients. Image analysis software was used to evaluate FDG-PET perfusion images and produce quantified measures of the extent and severity of scarring and mismatch of heart tissue. Images were reviewed by physicians experienced in reading PET data, and then the physician or surgeon decided whether to proceed with revascularization based on the images.
In the PET group, a total of 55 patients received FDG-PET scans, which discovered varying degrees of myocardium viability. As a result, 25 (45%) of the 56 subjects received revascularization, which included 22 coronary artery bypass grafts and three percutaneous coronary interventions.
In the standard-care group, 24 (44%) of 55 patients underwent revascularization, which included 17 coronary artery bypass grafts and seven percutaneous coronary interventions. In addition, three patients underwent late revascularization.
Among the 82 patients with recent angiography procedures, 75 (91%) had two-vessel, three-vessel, or left main disease with 50% stenosis -- 39 (91%) of 43 patients in the PET group and 36 (92%) of 39 patients in the standard-care group. Distal stenosis of 50% in at least two distal segments was reported in 12 PET group patients (28%) and in 11 standard-care group patients (28%).
Cardiac events
The researchers also confirmed 32 cardiac events among the Ottawa-FIVE patients, including six cardiac deaths, four myocardial infarctions, and 22 cardiac hospitalizations. Ten patients in the PET group and 22 patients in the standard-care group experienced a cardiac event.
Based on the results, the researchers noted that a "significant reduction in cardiac events was observed in patients with FDG-PET-assisted management, compared with patients who received standard care. The results suggest that outcome may be benefited using FDG-PET in an experienced center with ready access to FDG and integration with imaging, heart failure, and revascularization teams."
The authors cited several limitations to the study, noting "inherent limitations of post hoc and subgroup analyses" and that conclusions "should be confirmed in a larger prospective study."
However, they added that the sample size was "sufficient to identify the significant interaction between FDG-PET-guided therapy and the Ottawa-FIVE subgroup in the primary outcome-adjusted model and the associated statistically significant hazard ratios."
By Wayne Forrest
AuntMinnie.com staff writer
April 2, 2010
Related Reading
Cedars-Sinai explores PET's future in nuclear cardiology, April 11, 2008
PET shows superiority in detecting coronary artery disease, March 28, 2008
PET identifies inflammation severity in carotid plaques, November 21, 2006
PET perfusion can predict cardiac events, March 15, 2006
PET, SPECT measures of LVEF have superior predictive value, March 13, 2006
Copyright © 2010 AuntMinnie.com
