SPECT identifies 'silent' cardiovascular risk in diabetic patients

June 17, 2002

Los Angeles, California...Diabetic patients who show no symptoms may still be at risk for cardiovascular disease, according to information reported at the Society of Nuclear Medicine's (SNM) 49th Annual Meeting in Los Angeles.

SPECT myocardial perfusion imaging (MPI) studies were performed on 189 diabetic patients. Although ECG changes were observed in only 14% of the patients in the study, SPECT revealed stress-induced ischemic defects in more than 56% of the participants. Moreover, these defects were more prevalent in patients in the asymptomatic group than in those with a history of chest pain, regardless of the age or sex of the participant.

John O. Prior, MD, PhD, and colleagues from the Centre Hospitalier Universitaire Vaudois in Lausanne, Switzerland, presented the results of a study on the use of single-photon emission computed tomography (SPECT) MPI to evaluate the presence of "silent" myocardial ischemia in diabetic patients undergoing cardiac assessment. Myocardial ischemia, a deficiency of blood supply to the heart muscle as a result of obstruction or constriction of the coronary arteries, is a leading cause of death among individuals with diabetes and often progresses without overt warning to a point at which cardiac damage is irreversible.

According to the American Diabetes Association, heart disease is a factor in 75% of diabetes-related deaths and results in more than 77,000 deaths in diabetics annually in the United States.

For the study, patients were analyzed for stress-induced ischemia. Patients were divided into two groups, those who had previously experienced chest pain and those who had not. Stress was induced either on a bicycle ergometer or, in those patients unable to exercise, by perfusion of dipyridamole. The defects were also more prevalent in those unable to exercise and in those who had presented ECG abnormalities on earlier tests. Stress-induced ischemic defects have been shown to accurately predict the possibility of future cardiac events.

"Our results indicate that diabetic patients should be aware that although they might not experience chest pain during stress-test exercising, they are actually at increased risk for cardiac events, and SPECT can provide important information about that risk," said Dr. Prior. "This is also true for patients who are physically unable to perform a bicycle or treadmill test or who presented with ECG abnormalities on an earlier stress test."

The authors concluded that SPECT examination should not be deferred in an admission or emergency cardiac assessment simply because the diabetic patient is asymptomatic or unable to exercise. "Myocardial perfusion SPECT should be performed as part of the work-up of diabetic patients," said Dr. Prior. "Our results indicate that this is especially important in those cases in which ECG abnormalities are present and/or in cases of elevated blood levels of cardiac enzymes (troponin)." Prior and his colleagues also recommended that nuclear medicine physicians work more closely with ER staff to facilitate the availability of SPECT MPI for the evaluation of diabetic patients.
The Society of Nuclear Medicine Annual Meeting is being held June 15-19 at the Los Angeles Convention Center, Los Angeles, CA. In addition to educational sessions, the meeting will focus on leading medical developments in the field of nuclear medicine, including radioimmunotherapy with a new class of drugs that target cancer, diagnostic breakthroughs with positron emission tomography (PET), and other topics. More than 5,000 specialists in the field of nuclear medicine, including scientists, technologists, researchers, and representatives from the medical industry, are expected to attend. The Society of Nuclear Medicine is an international scientific and professional organization with more than 13,000 members dedicated to promoting the science, technology, and practical applications of nuclear medicine. The SNM is based in Reston, VA.

For late-breaking news about the world of nuclear medicine and events at the 49th Annual Society of Nuclear Medicine meeting, visit www.snm.org

Abstract 505. Wednesday, June 19, 8:00-8:15 a.m. Room 410
Prevalence of Stress-Induced Myocardial Ischemia in Diabetic Patients--Relation to Angina, Capacity to Exercise and Abnormal Stress-ECG
J.O. Prior, D. Monbaron, J. Ruiz, A. Bischof Delaloye
Centre Hospitalier Universitaire Vaudois
Lausanne, Switzerland

PREVALENCE OF STRESS-INDUCED MYOCARDIAL ISCHEMIA IN DIABETIC PATIENTS -- RELATION TO ANGINA, CAPACITY TO EXERCISE AND ABNORMAL STRESS-ECG J. O. Prior*, D. Monbaron, J. Ruiz, A. Bischof Delaloye, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland. (200642) Objective: To analyze the prevalence of stress-induced myocardial ischemia in diabetic patients referred for myocardial scintigraphy, in relation to prior angina, capacity to exercise and stress-induced ECG changes. Methods: Gated-SPECT myocardial perfusion studies of 189 diabetic patients (aged 62.0 ± 9.5 y SD, 43% women) were analyzed for stress-induced ischemia (reversible perfusion defects). Subjects were divided in two groups: patients with prior angina (37%) and without. We used a 2-head gamma camera (E.cam, Siemens) and conventional 1-day protocol (dual-isotope 201Tl/99mTc-MIBI or single-isotope 201Tl or 99mTc-MIBI). Stress was performed on a bicycle-ergometer (41%) or with dipyridamole in subjects unable to exercise. Results: Stress-induced ischemia existed in 105 (56%) patients, without sex difference (c2 test, P = 0.29). Twenty-five (13%) patients presented chest pain during scintigraphic stress study. Stress-induced ECG changes were observed in 27 (14%) patients. However, ECG could not be assessed in 37 (20%) patients (pre-existing ST changes or conduction abnormalities). The prevalence of stress-induced ischemia in asymptomatic patients (63%) was greater than in symptomatic patients (43%; c2 test, P = 0.007). Stepwise logistic regression analysis of stress-induced ischemia showed an odds ratio of 3.7 (95% CI = 2.1-6.3) for stress-induced ECG changes, 2.6 (1.3-5.2) for exercise incapacity, and 0.42 (0.22-0.82) for angina, independently of age or sex. Conclusions: Stress-induced ischemia is more prevalent in diabetic patients who are asymptomatic (silent ischemia), unable to exercise, or with abnormal stress-ECG. The presence of stress-induced ischemia leads to an increased cardiovascular event rate that should be investigated by coronary angiography. Consequently, scintigraphic examination of diabetic patients should not be delayed because they are angina-free, unable to exercise or present with abnormal stress-ECG.

Society of Nuclear Medicine

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