A prospective evaluation of the repeatability of left ventricular ejection fraction measurement by gated SPECT.

BACKGROUND: Gated single-photon emission computed tomography (SPECT) is widely used for myocardial perfusion imaging and provides an automated assessment of left ventricular ejection fraction (LVEF). We prospectively tested the repeatability of serial SPECT-derived LVEF. This information is essential in order to inform the interpretation of a change in LV function on serial testing. METHODS: Consenting patients (n = 50) from among those referred for clinically indicated gated myocardial perfusion SPECT (MPs) were recruited. Following the clinical rest-stress study, patients were repositioned on the camera table for a second acquisition using identical parameters. Patient positioning, image acquisition and processing for the second scan were independently performed by a technologist blinded to the clinical scan. Quantitative LVEF was generated by Quantitative Gated SPECT and recorded as EF1 and EF2, respectively. Repeatability of serial results was assessed using the Bland-Altman method. The limits of repeatability and repeatability coefficients were generated to determine the maximum variation in LVEF that can be expected to result from test variability. Repeatability was tested across a broad range of LV systolic function and myocardial perfusion. RESULTS: The mean difference between EF1 and EF2 was 1.6% (EF units), with 95% limits of repeatability of +9.1% to -6.0% (repeatability coefficient 7.5%). Correlation between serial EF measurements was excellent (r = 0.9809). Similar results were obtained in subgroups based on normal or abnormal EF and myocardial perfusion. The largest repeatability coefficient of 8.1% was seen in patients with abnormal LV systolic function. CONCLUSION: When test protocol and acquisition parameters are kept constant, a difference of >8% EF units on serial MPs is indicative of a true change 95% of the time.

Relationship between silent myocardial ischemia and coronary artery disease risk factors.

BACKGROUND: The association between silent myocardial ischemia (SMI) and coronary artery disease (CAD) risk factors in asymptomatic patients with no prior history of CAD referred for stress myocardial perfusion imaging (MPI) is unknown. METHODS: We retrospectively evaluated patients who underwent MPI over a 3.4-year period to identify those who did not have chest pain, dyspnea, or known CAD. The presence of risk factors was categorized as none, 1-2, 3-4, and ≥5. MPI was performed using a rest thallium-201/stress Tc-99m sestamibi protocol, and read using a standard five-point perfusion score (0 = normal to 4 = absent) and a 17-segment left ventricular model. Summed stress score and summed rest score were derived as the sum of individual segmental scores at stress and rest, respectively. SMI was diagnosed if the summed differences score (SDS) was ≥2. Prognostically significant ischemia was defined by a SDS ≥ 8. RESULTS: Among 1,354 asymptomatic patients, SMI was present in 97 (7.2%) and prognostically significant in 60 (4.4%). The prevalence, but not severity, of SMI increased with increasing CAD risk factors--0 for none, 4.1% for 1-2, 8.8% for 3-4, and 12% for those with ≥5 CAD risk factors (P value for trend = .001), in patients <74 years of age. Of the 59 (4.4%) patients who underwent coronary angiography, only 31 (2%) had significant anatomical CAD. CONCLUSIONS: The prevalence of SMI and prognostically significant ischemia is low in asymptomatic patients without known CAD, and is related to the number of CAD risk factors in patients younger than 74 years of age.

Predictors of an ischemic electrocardiographic response in patients with exercise-induced myocardial ischemia.

BACKGROUND: The determinants of an ischemic electrocardiographic (ECG) response in patients with exercise-induced ischemia on single-photon emission computed tomography (SPECT) remain poorly defined. Specifically, it is unknown whether the occurrence of an ischemic ECG response is related to the extent and/or severity of SPECT ischemia. METHODS AND RESULTS: Among 3,294 patients who underwent exercise SPECT using a rest thallium-201/exercise Tc-99m sestamibi protocol, 699 (21%) patients had myocardial ischemia defined as summed difference score (SDS) ≥2. The extent of SPECT ischemia was further defined as the total number of segments with difference score ≥1, and severity of ischemia as the largest difference score among all segments. Patients with ischemic ECG changes (n = 315) were significantly older and had a significantly greater prevalence of hyperlipidemia. SDS (7.4 ± 2.2 vs 4.7 ± 1.9, P < .0001), extent (4.2 ± 2.6 vs 2.9 ± 1.7, P < .0001), and severity (2.8 ± 0.9 vs 2.3 ± 0.8, P < .0001) of SPECT ischemia were greater among patients with ischemic ECG changes. In multivariate analysis, age and SDS (which is a composite of the extent and severity of ischemia) were associated with ischemic ECG. When analyzed in a separate model which did not include SDS, both severity of SPECT ischemia (OR 1.42, CI 1.13-1.79) and extent of SPECT ischemia (OR 1.21, CI 1.10-1.33) were independently associated with ischemic ECG. CONCLUSIONS: Among patients with exercise-induced myocardial ischemia by SPECT, age and SDS were associated with ischemic ECG changes. When analyzed separately, the severity and extent of SPECT ischemia were both independent predictors of ischemic ECG changes.

Implementation of a clinical reasoning curriculum for clerkship-level medical students: a pseudo-randomized and controlled study.

Background The National Academies of Sciences report Improving Diagnosis in Healthcare highlighted the need for better training in medical decision-making, but most medical schools lack formal education in clinical reasoning. Methods We conducted a pseudo-randomized and controlled study to evaluate the impact of a clinical reasoning curriculum in an internal medicine clerkship. Students in the intervention group completed six interactive online modules focused on reasoning concepts and a skills-based workshop. We assessed the impact of the curriculum on clinical reasoning knowledge and skills and perception of education by evaluating: (1) performance on a clinical reasoning concept quiz, (2) demonstration of reasoning in hospital admission notes, and (3) awareness of attending physician utilization of clinical reasoning concepts. Results Students in the intervention group demonstrated superior performance on the clinical reasoning knowledge quiz (67% vs. 54%, p < 0.001). Students in the intervention group demonstrated superior written reasoning skills in the data synthesis (2.3 vs. 2.0, p = 0.02) and diagnostic reasoning (2.2 vs. 1.9, p = 0.02) portions of their admission notes, and reported more discussion of clinical reasoning by their attending physicians. Conclusions Exposure to a clinical reasoning curriculum was associated with superior reasoning knowledge and superior written demonstration of clinical reasoning skills by third-year medical students on an internal medicine clerkship.

Left ventricular systolic dysfunction predicts long-term major microvascular complication outcomes in type 1 diabetes. The Pittsburgh Epidemiology of Diabetes Complications (EDC) study of childhood onset diabetes.

OBJECTIVES: We aimed to assess association between abnormal LVEF, in the absence of coronary artery disease (CAD), and 25-year incidence of major outcomes of diabetes (MOD) in a cardiology substudy of the Pittsburgh Epidemiology of Diabetes Complications cohort of childhood-onset type 1 diabetes. METHODS: 115 normotensive type 1 diabetes individuals without known CAD, underwent a baseline exercise radionuclide ventriculography. Abnormal LVEF was defined as a resting ejection fraction <50% or a failure to increase ejection fraction with exercise by >5% (men) or a fall in ejection fraction with exercise (women). Cox proportional hazards models were used to predict the composite endpoint of MOD (first instance of major CAD, stroke, end-stage renal disease, blindness, amputation or diabetes-related death). RESULTS: Mean baseline age was 28 and diabetes duration 19 years. In a mean follow-up of 19 years, 50 MOD events were identified. Allowing for established risk factors at baseline, abnormal LVEF (n = 22) independently predicted MOD incidence (HR = 2.12, 95% CI: 1.12-4.00, p = 0.022) but not major CAD (HR = 1.33, 95% CI: 0.53-3.33, p = 0.539). CONCLUSIONS: An abnormal LVEF may identify diabetic cardiomyopathy and predict long term risk of MOD (but not CAD alone) in type 1 diabetes individuals, consistent with it reflecting microvascular disease.

On the importance of image gating for the assay of left ventricular mechanical dyssynchrony using SPECT.

UNLABELLED: The potential of SPECT for quantifying left ventricular mechanical dyssynchrony is increasingly appreciated. We sought to examine the incidence and impact of image gating errors on this quantification and to test a possible solution for affected studies. METHODS: First, to establish whether and how gating error alone could affect the measurement of dyssynchrony, we performed a prospective study in which patients with pacemakers were studied twice: during normal rhythm without gating error and with gating error caused by pacemaker-induced dysrhythmia. Second, to understand the pattern and magnitude of gating error during our typical imaging practice, we retrospectively examined studies from a separate cohort of 64 patients who were referred for dyssynchrony evaluation. Third, to understand whether studies with gating error could be repaired for the purpose of quantifying dyssynchrony, we tested a correction algorithm on the pacemaker-induced dysrhythmia image set to see whether it repaired this set so as to approximate the patients' normal rhythm image data. We subsequently applied this algorithm to the 64-patient cohort. RESULTS: Pacemaker-induced gating error caused a spurious decrease in dyssynchrony magnitude. Among the 64-patient cohort, similar gating errors were common, and an inverse exponential relationship between gating-error magnitude and dyssynchrony magnitude was observed. The correction algorithm accurately repaired the pacemaker-induced dysrhythmia image set; when it was applied to the 64-patient cohort, the magnitude of the postcorrection increase in dyssynchrony magnitude was proportional to the magnitude of the gating error. CONCLUSION: Gating errors cause a spurious reduction in SPECT assay of dyssynchrony magnitude. In our standard imaging practice, gating errors were common. Post hoc correction appears to be feasible.

Clinical value of attenuation correction in stress-only Tc-99m sestamibi SPECT imaging.

BACKGROUND: Attenuation artifact remains a substantial limitation to confident interpretation of images and reduces laboratory efficiency by requiring comparison of stress and rest image sets. Attenuation-corrected stress-only imaging has the potential to ameliorate these limitations. METHODS AND RESULTS: Ten experienced nuclear cardiologists independently interpreted 90 stress-only electrocardiography (ECG)-gated technetium 99m sestamibi images in a sequential fashion: myocardial perfusion imaging (MPI) alone, MPI plus ECG-gated data, and attenuation-corrected MPI with ECG-gated data. Images were interpreted for diagnostic certainty (normal, probably normal, equivocal, probably abnormal, abnormal, and perceived need for rest imaging). With stress MPI data alone, only 37% of studies were interpreted as definitely normal or abnormal, with a very high perceived need for rest imaging (77%). The addition of gated data did not alter the interpretations. However, attenuation-corrected data significantly increased the number of studies characterized as definitely normal or abnormal (84%, P <.005) and significantly reduced the perceived need for rest imaging (43%, P <.005). These results were confirmed by use of a nonsequential consensus interpretation of three readers. CONCLUSION: Attenuation correction applied to studies with stress-only Tc-99m ECG-gated single photon emission computed tomography images significantly increases the ability to interpret studies as definitely normal or abnormal and reduces the need for rest imaging. These findings may improve laboratory efficiency and diagnostic accuracy.