Preliminary Data on the Prognostic Value of a New Protocol of Ultra-fast Myocardial Scintigraphy with Less Radiation in CZT Gamma Camera

Abstract

Background: Myocardial perfusion scintigraphy (MPS) is one of the most used imaging methods for the evaluation of patients for coronary artery disease (CAD) due to its diagnostic and prognostic value. Two of its main limitations are radiation use and scan duration. However, CZT cameras (CZT-C) have allowed tracer dose and scan time reductions. However, the prognostic value of these new protocols is not known. Objective: To determine the prognostic value of a new, ultrafast, low dose protocol in a CZT-C. Population: Patients with suspect CAD undergoing MPS from 11/2011 to 6/2012 were studied. Methods: They had a 1-day Tc-99m sestamibi protocol starting with rest study (5 mCi dose) followed by stress (15 mCi). Acquisition times were 6 and 3 minutes respectively. MPS studied were classified as normal or abnormal and perfusion scores (SSS, SRS and SDS) were calculated. Patients were accompanied by 6-month phone calls. Events were defined as death, nonfatal myocardial infarction and late revascularization (> 60 days after MPS) and analyzed with the Cox method. Results: 792 patients were followed for 21.3 ± 3.7 months. Age was 65.2 ± 12.7 years, 50.3% were male and body mass index was 26.9 ± 4.7. Hypertension was the most frequent risk factor (59.5%), followed by hypercholesterolemia (51.9%) and diabetes (23.3%). Exercise was used in 438 (55.3%); 618 (78%) MPS studies were normal. Mean dosimetry was 6 mSv and mean scan time, 48 ± 11 minutes. During follow-up, there were 12 deaths, 4 nonfatal infarctions, 42 angioplasties and 5 coronary artery bypass surgeries. Annual hard event rate was higher in patients with abnormal MPS (3.0% vs. 0.7%, p < 0.01), as well as the frequency of patients undergoing late revascularization (10.8% vs 1.9%, p < 0.001). SSS and SDS were higher in patients with hard events compared to those without events (7.8 ± 8.8 vs 2.9 ± 5.7; 3.3 ± 5.7 vs 0.7 ± 2.2, p < 0.01) and among revascularized patients compared to non-revascularized (7.1 ± 7.9 vs 2.7 ± 5.6; 3.1 ± 4.4 vs 0.6 ± 2.1, p <0.001). Conclusion: A new MPS protocol in a CZT-C allowed faster, lower radiation studies without compromising the prognostic ability of this imaging method. (Arq Bras Cardiol: Imagem cardiovasc. 2016;29(1):11-16)