Uncontrolled risk factors and worsening perfusion pattern on SPECT myocardial perfusion imaging in medically treated patients with stable chronic ischaemic heart disease.

PURPOSE: Few data exist on the correlation between the effectiveness of risk factor control and the evolution of myocardial perfusion over time in patients with stable ischaemic heart disease. The aim of the study was to evaluate the changes in stress-rest myocardial perfusion in medically treated patients with stable chronic ischaemic heart disease and the relationship with risk factor control. METHODS: The study cohort included 174 consecutive patients (age 60 ± 9 years, 68 % men) undergoing stress-rest myocardial perfusion imaging (MPI) (study 1), who also underwent repeat evaluation (study 2) and who were clinically stable on medical therapy. Summed stress, rest and difference scores were calculated. According to the evolution of perfusion pattern from study 1 to study 2, patients were classified as improved, stable or worsened. RESULTS: Study 2 was performed on average 2.7 years after study 1. Of the 174 patients, 47 (26.9 %), 53 (30.8 %) and 74 (42.5 %) were classified as stable, improved and worsened, respectively. A significant trend was observed between the number of risk factors at the time of study 1 and worsening of myocardial perfusion (24 % of patients with zero or one risk factor showed worsening, 31 % with two, and 59 % with three or more; p = 0.03). Moreover, patients with worsened perfusion had a higher number of poorly controlled risk factors. CONCLUSION: Despite medical therapy and clinical stability, myocardial perfusion worsened in 42.5 % of patients. The risk profile was reclassified in half of the patients. Worsening occurred more frequently in patients with three or more risk factors at the time of study 1 and in those with poorly controlled risk factors at the time of study 2; in this subset of patients, even if clinically stable, reassessment after 2 years could be considered.

Wide beam reconstruction for half-dose or half-time cardiac gated SPECT acquisitions: optimization of resources and reduction in radiation exposure.

PURPOSE: A new iterative reconstruction algorithm (WBR™) has been recently proposed for cardiac single photon emission computed tomography (SPECT). The WBR™ technology is designed to reduce noise, improving lesion identification without affecting the image resolution, allowing SPECT studies with reduced count statistic. This allows for either half-time (HT) or half-dose (HD) cardiac SPECT, with image quality and quantitative data comparable to standard-time (ST) or standard-dose (SD) SPECT. Few data exist on the comparison between conventional filtered backprojection (FBP) and this new algorithm in a clinical setting. The aim of this study was to compare the performance of FBP and WBR™. METHODS: Phantoms studies were performed to compare spatial resolution and contrast recovery with FBP, ordered subset expectation maximization (OSEM) and WBR™. A group of 92 patients, with different cardiac pathology, scheduled for a stress-rest SPECT were studied: 52 patients (group A) were injected with a SD of tracer and underwent both ST and HT SPECT; 40 patients (group B) were injected with a half dose of tracer and underwent ST SPECT and immediately after an additional SPECT at double time/projection (DT), to compensate for the low count statistic. A 2-day (99m)Tc-sestamibi protocol was used in all patients. SD/ST and HD/DT SPECT were reconstructed with a conventional FBP; SD/HT and HD/ST SPECT were reconstructed with WBR™. The summed stress score (SSS) and summed rest score (SRS) were calculated; the left ventricular ejection fraction (LVEF) was automatically derived. RESULTS: In group A (SD), no significant differences were observed between ST FBP SPECT and HT WBR™ in SSS (11.1 and 11.7, respectively) and SRS (9.4 and 10.3, respectively, NS). LVEF on rest acquisitions was also comparable (50% on ST SPECT and 49% on HT SPECT, NS); LVEF on post-stress studies in HT SPECT (46%) was lower than ST SPECT (50%), although not statistically significant. In group B (HD), SSS (6.2 in ST and 5.3 in DT) and SRS (4.0 in ST and 3.3 in DT) were also comparable. No differences were documented between ST and DT in rest (47 and 48%, respectively) and stress (48 and 50%, respectively) LVEF. CONCLUSION: WBR™ performance and image quality were comparable to those of conventional FBP, allowing for either HT or HD studies. The former allows for an increased patient throughput and optimization of resources. The latter modalities would allow for a significant reduction in both patients' and operators' exposure. Further studies are needed to validate the clinical use of this method.