P327 Concordance between regadenoson stress echocardiography and spect-MIBI (99mTc) in patients with suspected myocardial ischemia

Abstract

Abstract Background Regadenoson is a selective A2A adenosine receptor agonist approved for the detection of myocardial with SPECT-MIBI. To date, few studies have appraised the utility of this drug using transthoracic echocardiography with the same purpose. We designed this prospective study to evaluate the diagnostic agreement between these two techniques used simultaneously to detect myocardial ischemia. We report our first results evaluating the concordance between both techniques. Methods Patients enrolled were referred to our clinic for the evaluation of chest pain. Myocardial perfusion imaging was performed with regadenoson (400 µg ) which was injected before 99mTc-MIBI. Stress and rest sets of images were evaluated for relative uptake of the radiotracer in order to detect and characterize perfusion defects. The echocardiogram was acquired 60-90 seconds after the administration of the drug using a standardized technique. Two independent observers (one cardiologist and one specialist in nuclear medicine) interpreted the images, both unaware of the result of the complementary technique. Results One hundred twenty five patients were included, 69 (55%) of them males. Median age was 73 years (IQR 65-79). One hundred seventeen patients had both studies interpretable. Thirty-nine (32.5%) patients had had a diagnosis of ischemic heart disease before the study (either a myocardial infarction or a coronary revascularization). The median pre-test probability of coronary artery disease in those without a true previous diagnosis was 30.5% (16.0-50.8), being 50% in the intermediate risk (15-85%) and 49% in the low risk stratum (less than 15%). Significant reductions is systolic and diastolic blood pressure were detected with regadenoson [systolic 134 (21) mmHg Vs 131 (23) mmHg, p < 0.001; diastolic: 78 (12) mmHg Vs 73 (13) mmHg, p < 0.001], with a striking increase in heart rate: 67 (13) bpm Vs 91 (17) bpm, p < 0.001. More patients had a SPECT test showing myocardial ischemia (28% Vs 16%; p < 0.001). Agreement between both tests were 84%. The kappa index obtained from this sample was 0.34 (CI95% 0.15-0.53). Segregating those patients without a history of coronary artery disease (n = 81), the positive test rate were 14% for echo and 20% for SPECT-MIBI (p = 0.019). Kappa index was even lower: 0.29 (CI95% 0.02-0.56). Conclusions. SPECT-MIBI provides more positive tests than stress echocardiography when regadenoson is used as the stressor agent. The concordance between tests is low.