Abstract 324: Outcomes of Patients With Normal Rubidium-82 Positron Emission Tomography Stress Perfusion Studies and Dipyridamole-Induced ECG ST-Segment Depression
Background: Ischemic ECG changes during otherwise normal adenosine SPECT studies are rare but associated with higher event rates. A single publication reported no adverse implication when ischemic ECG changes occurred in the setting of a normal Rb-82 PET study. In order to further understand the clinical significance of this discordant finding, we compared outcomes of a large population of patients with normal Rb-82 PET scans grouped according to ischemic or non-ischemic ST depression in response to dipyridamole (Dipy) pharmacologic stress.
Methods: All patients (pts) between Jun 2002 and Nov 2007 with normal Dipy Rb-82 PET scans by both perfusion and function analysis, normal baseline ECGs, and not on medications associated with heart-rate modulated ST depression were enrolled. We collected and analyzed pts demographic and clinical data as well as ECG changes in response to Dipy stress. Characteristics of pts who had ischemic ST depression (+ECG) (> 1.0 mm from baseline) were compared with those who did not (−ECG) for rates of all cause mortality, referral for coronary angiography and coronary revascularization. All pts were followed-up for at least 1 year. Categorical variables were analyzed with χ2 and continuous variables with the Student’s t-test. One-year mortality was estimated by the Kaplan-Meier method.
Results: 2004 pts had a normal Rb-82 PET scan. Of these, 123 pts (6%) had a +ECG response. There were no significant differences in age, BMI, history of coronary artery disease, HTN, dyslipidemia, smoking, and diabetes between the +ECG and −ECG groups. However, women were markedly over-represented in the +ECG group (84.6% vs 61.1%; p<0.001) Mean follow up time was 2.8±1.5 years and mean age was 65.9±12.3. There was no significant difference in all-cause mortality between the +ECG and the −ECG groups (1.6% vs. 2.1%, p = 0.70). There were also no differences in referrals for cath or PCI in either group (p=0.082). This relationship persisted after adjustment for baseline differences.
Conclusion: In pts with normal myocardial perfusion by PET MPI, Dipy-induced ST-segment depression is an uncommon but not rare finding that is closely associated with female gender, and does not impact the very low mortality associated with a normal Rb-82 PET scan.