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SNMMI Press Releases

August 1, 2012

Difficult to Diagnose Cases of Infectious Endocarditis Solved with SPECT/CT Imaging Agent

Reston, Va. – When combined with standard diagnostic tests, functional imaging procedures have been shown to reduce the rate of misdiagnosed cases of infectious endocarditis. According to new research published in the August issue of The Journal of Nuclear Medicine, single photon emission computed tomography (SPECT)/computed tomography (CT) with 99mTc-hexamethylpropleneamine oxime-labeled white blood cells (99mTc-HMPAO-WBC) can improve the diagnosis of infectious endocarditis in hard-to-diagnose cases.

Infectious endocarditis is an infection of the lining of the heart chambers and heart valves that is caused by bacteria, fungi or other infectious substances. It affects 2-4 people per 100,000 each year, with 25-50 percent of the cases occurring in patients older than 60 years. Mortality from infectious endocarditis remains high when this condition is undiagnosed and, therefore, not adequately treated.

The diagnosis of infectious endocarditis is becoming progressively more challenging in the past years because of a variety of factors: the indiscriminate use of antimicrobial agents in some clinical settings, the increased number of individuals with predisposing or underlying conditions (i.e., frail and elderly, immune-suppressed persons), and the increasing number of interventional cardiovascular procedures and placement of valve prostheses, intravascular devices and cardiac devices.

“SPECT/CT with 99mT-HMPAO-WBC is a nuclear medicine technique currently used for the management of patients with infection; its application in infectious endocarditis has been restricted to few reports,” said Paola A. Erba, MD, lead author of the study. “With this work we aimed to open new perspective for the application of this technique.”

Researchers conducted 99mTc-HMPAO-WBC SPECT/CT scans on 131 consecutive patients with suspected infectious endocarditis. Patients with permanent cardiac devices were excluded from the research as the devices might have introduced the infection. Results from the scans were compared to diagnostic tests for standard infectious endocarditis—transthoracic or transesophageal echocardiography, blood cultures and the modified Duke Endocarditis Service criteria, which are recommended for classification.

Of the 131 patients, 97 were found to have uptake indicating infection.The 99mTc-HMPAO-WBC SPECT/CT scan was true-positive in 46 of 51 patients and false negative in 5 of 51 cases (90 percent sensitivity, 94 percent negative predictive value and 100 percent specificity and positive predictor value). In addition, septic embolism was detected in 41 percent of the patients.

“When the results of the 99mTc-HMPAO-WBC SPECT/CT scan were associated with either positive echocardiography or a positive blood culture, no cases of infectious endocarditis went undiagnosed,” noted Erba. “This demonstrates the added value that 99mTc-HMPAO-WBC SPECT/CT scans can provide to assist physicians in their diagnosis and treatment decisions. Cardiologists and infectivologists dealing with infectious endocarditis should consider using 99mT-HMPAO-WBC when they are facing difficult situation.”

Authors of the article “Added Value of 99mTc-HMPAO-Labeled Leukocyte SPECT/CT in Characterization and Management of Patients with Infectious Endocarditis”include Paola A. Erba, Elena Lazzeri, Martina Sollini and Giuliano Mariani, Regional Center of Nuclear Medicine, University of Pisa Medical School, Pisa, Italy; Umberto Conti, Laboratory of Echocardiography, Cardiology Unit, Azienda Ospaedaliero-Universitaria Pisana, Pisa, Italy;  Roberta Doria, Carlo Tascini and Francesco Menichetti, Infectious Disease Department, Azienda Ospaedaliero-Universitaria Pisana, Pisa, Italy; Salvatore M. De Tommasi, Cardiology Department, Azienda Ospaedaliero-Universitaria Pisana, Pisa, Italy; Francesco Bandera, Cardiovascular Department “E Malan,” IRCCS Policlinico San Donato Milanese, Milan, Italy; A.J.O. Dierckx, Nuclear Medicine and Molecular Imaging Department, University Medical Center Groningen, The Netherlands; and Alberto Signore, Nuclear Medicine and Molecular Imaging Department, University Medical Center Groningen, The Netherlands and Nuclear Medicine Unit, S. Andrea Hospital, University of Rome, Rome, Italy.

Please visit the SNMMI Newsroom to view the PDF of the study, including images, and further reading about molecular imaging and personalized medicine. To schedule an interview with the researchers, please contact Susan Martonik at (703) 652-6773 or smartonik@snmmi.org.Current and past issues of The Journal of Nuclear Medicinecan be found online at http://jnm.snmjournals.org.

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The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and medical organization dedicated to raising public awareness about nuclear medicine and molecular imaging, a vital element of today’s medical practice that adds an additional dimension to diagnosis, changing the way common and devastating diseases are understood and treated and helping provide patients with the best health care possible.

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