Stress-only Tc-99m myocardial perfusion imaging in an emergency department chest pain unit.

BACKGROUND: Stress-only myocardial perfusion imaging (MPI) saves time by eliminating rest imaging, which is important for emergency department (ED) throughput but has not been studied in an ED population. STUDY OBJECTIVE: To determine the prognosis of a normal stress-only MPI study compared to a normal rest-stress MPI and establish its effectiveness in an ED setting. METHODS: All patients evaluated in the ED over 6.5 years who underwent a stress-only technetium-99m gated MPI were compared to those who had a rest-stress study. All-cause mortality was determined using the Social Security Death Index. Survival was analyzed in patients with normal and abnormal MPI results. RESULTS: A total of 4145 studies (2340 stress-only, 1805 rest-stress) were performed. Patients' average age was 57.9 years, 38.5% were male, and most had an intermediate or low pretest risk of coronary artery disease (87.7%). Average follow-up was 35.9 ± 20.9 months. In patients with normal perfusion, at 1 year of follow-up there were 11 deaths in the stress-only group (0.5% 1-year mortality), and 13 deaths in the rest-stress cohort (1.1% 1-year mortality). At the end of follow-up, the stress-only group had a lower all-cause mortality (p < 0.0001) and similar risk adjusted all-cause mortality (p = 0.10) than the rest-stress cohort. Patients with abnormal perfusion demonstrated the expected differential prognosis based on total perfusion deficits in both groups. CONCLUSIONS: A normal stress-only MPI study has a benign 1-year prognosis similar to a rest-stress study when performed in the ED. The ability to triage patients more rapidly and reduce radiation exposure represents an attractive alternative for low-risk patients.

The prognosis of a normal stress-only Tc-99m myocardial perfusion imaging study.

BACKGROUND: Stress-only imaging saves time and radiation exposure, but apprehension remains about the reliability, diagnostic, and prognostic accuracy of a normal stress-only study. The objective of this study was to determine the prognosis of stress-only SPECT MPI in routine clinical practice. METHODS: Patients at lower pre-test risk for CAD presenting for a Tc-99m SPECT MPI over a 2-year period underwent a stress-only protocol. If the stress images were normal (attenuation correction was routinely acquired on all patients), rest imaging was not done. Outcomes of the stress-only group were compared to a full rest-stress protocol cohort. Only patients with normal perfusion and left ventricular function, and no known CAD, were included. All-cause mortality was determined using the Social Security Death Index and specific causes of death were determined using the National Death Index. The difference in all-cause and cardiac mortality between groups in the presence of competing risks was assessed using log-normal survival models. RESULTS: Out of 10,609 patients studied during the time period, 1,673 had a normal stress-only study and 3,237 had a normal rest-stress study. At one year, there were 20 total and 3 cardiac deaths (1.2% and 0.2% mortality) in the stress-only group, and 40 total and 4 cardiac deaths (1.2% and 0.1% mortality) in the rest-stress cohort. At the end of follow-up (40 +/- 9 months), there were 46 total and 7 cardiac deaths (2.7% and 0.4% mortality) in the stress-only group, and 119 total and 17 cardiac deaths (3.7% and 0.5% mortality) in the rest-stress cohort. No significant difference between the stress-only and rest-stress cohorts was found after controlling for confounding variables for both all-cause mortality (p = .94) and cardiac mortality (p = .82). CONCLUSIONS: A normal stress-only MPI has an excellent short-term prognosis (both for all-cause and cardiac mortality) comparable to that of a normal rest-stress MPI study.

Advantage of optimizing V-V timing in cardiac resynchronization therapy devices.

BACKGROUND: There is little consensus as to the benefits of interventricular (V-V) timing optimization in cardiac resynchronization therapy (CRT). A variety of parameters are currently used to optimize device timing. This study was designed to investigate the potential advantage of using 3D ejection fraction (EF) and aortic velocity-time integral (VTI) as measures of global left ventricular (LV) function to optimize ventricular activation in CRT devices. METHODS: Seventy-four patients seen in the Optimization Clinic with adequate echocardiographic images were included. Three aortic VTI and two 3D EF values were recorded at five V-V settings and the average value used. Aortic VTI and 3D EF were classified as the best, worst, and simultaneous setting values. Data were analyzed using a two-tailed paired t-test. RESULTS: Comparing the best to worst V-V timing settings, VTI improved by 4.7 ± 7.5 cm (P < 0.0001) and 3D EF by 9.9%± 5.7% (P < 0.0001). Comparing the simultaneous setting to the best V-V timing setting, VTI improved by 2.4 ± 2.1 cm (P < 0.0001) and 3D EF by 3.8%± 4.9% (P < 0.0001). Aortic VTI improved in 85% of patients and 3D EF improved in 72%. However, only 26% of the patients had the same optimal setting using aortic VTI and 3D EF yielding an r(2) value of 0.003. CONCLUSIONS: Individualized echocardiographic V-V optimization of CRT devices improves global LV function as measured by aortic VTI and 3D EF. Substantial differences in function were seen over an 80-ms range of V-V timing and optimization resulted in improved LV function in the majority of patients.