Stress-rest Single-photon Emission Computed Tomography Research Articles

Association between hypercholesterolemia and mortality risk among patients referred for cardiac imaging test: Evidence of a “cholesterol paradox?”

AimSome observational studies have observed a lower, rather than higher, mortality rate in association with hypercholesterolemia during follow-up of patients after cardiac stress testing. We aim to assess the relationship of hypercholesterolemia and other CAD risk factors to mortality across a wide spectrum of patients referred for various cardiac tests. Methods and resultsWe identified four cardiac cohorts: 64,357 patients undergoing coronary artery calcium (CAC) scanning, 10,814 patients undergoing coronary CT angiography (CCTA), 31,411 patients without known CAD undergoing stress/rest single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI), and 5051 patients with known CAD undergoing stress/rest SPECT-MPI. Each cohort was followed for all-cause mortality using risk-adjusted Cox models. We pooled the hazard ratios between cohorts with a random effects model. Baseline risk varied markedly among cohorts, from an annualized mortality rate of 0.31%/year in CAC patients to 3.63%/year among SPECT-MPI patients with known CAD. Hypertension, diabetes, and smoking were each associated with increased mortality in each patient cohort (pooled hazard ratio[95% CI]: 1.38[1.33–1.44], 1.88[1.76–2.00], and 1.67[1.48–1.86], respectively). By contrast, hypercholesterolemia was associated with decreased rather than increased mortality (pooled hazard ratio[95% CI]: 0.71[0.58–0.84]). Analysis of serum lipids among 7744 patients undergoing CAC or CCTA scanning revealed an inverse relationship between LDL cholesterol and mortality. ConclusionsAmong a broad spectrum of patients referred for a variety of cardiac tests and ranging from low to high clinical risk, hypercholesterolemia was not associated with increased mortality risk. Our findings suggest that hypercholesterolemia may be sensitive to confounding by other clinical factors and post-test treatment changes in patient populations.

Fixed myocardial perfusion defects on SPECT are not associated with focal myocardial fibrosis on CMR in adult patients with systemic right ventricle

Abstract Funding Acknowledgements Type of funding sources: None. Background Myocardial fibrosis is a known prognostic factor in patients with systemic right ventricle (SRV). In these patients fixed myocardial perfusion defects are a common finding and are thought to represent areas of myocardial infarction and fibrosis. However, no study has yet correlated myocardial perfusion imaging findings with cardiac magnetic resonance (CMR) imaging, which is the imaging gold standard for detecting myocardial fibrosis. Purpose Our aim was to evaluate whether fixed myocardial perfusion defects in adult patients with SRV represent myocardial fibrosis. Methods Patients with SRV followed at our outpatient clinic for congenital heart disease were prospectively included. Myocardial perfusion was evaluated with a two-day stress/rest single-photon emission computed tomography (SPECT) protocol, focal myocardial fibrosis with late gadolinium enhancement (LGE) and diffuse myocardial fibrosis with T1 mapping by CMR. The 12-segment model of the right ventricle was used to report segments with myocardial perfusion defects and fibrosis (Figure 1). Results Fifteen patients with SRV (12 patients with transposition of the great arteries following atrial switch procedure and 3 patients with congenitally corrected transposition of the great arteries; 4 (26.7%) females; mean age 34.6 ± 10.0 years) were included. Myocardial perfusion defects were present in 14 patients (93%), with predominate fixed perfusion defects (73%) and less common reversible perfusion defects (27%). Fixed myocardial perfusion defects were most frequent in anterior RV segments (figure 1), with multiple segments affected in 11 patients (median number of affected segments – 2 segments). CMR was possible in 11 (73%) patients, others had a permanent pacemaker. LGE indicating focal myocardial fibrosis was detected in only 1 (9%) patient, while increased T1 values indicating diffuse myocardial fibrosis were present in 7 (64%) patients. There was no matching between areas of fixed myocardial perfusion defects and focal myocardial fibrosis in individual patients. Conclusions In our study, fixed myocardial perfusion defects detected on SPECT in patients with SRV did not represent areas of focal myocardial fibrosis on CMR. Other causes than scar may explain the frequently reported fixed perfusion defects, such as SRV anatomy with anterior position of the outflow tract and aorta, SRV morphology with variable degree of wall thickness and hypertrophy that influences tracer accumulation and image quality, or difficulties due to complex image acquisition and interpretation. To improve the diagnostic accuracy, the use of fused imaging modalities (SPECT-CT or PET-CT) is recommended in patients with SRV. Figure 1. Bull`s eye 12-segment plots of the right ventricle (RV) representing the number of segments with fixed myocardial perfusion defects detected by SPECT (1A) and LGE by CMR (1B) in patients with SRV. ANT – anterior, FW – free wall, INF – inferior, SEP – septal wall of RV. Abstract Figure.

Adenosine single-photon emission computed tomography-derived transient ischemic dilatation and ejection fraction reserve fail to predict multivessel coronary artery disease.

Next to myocardial perfusion, single-photon emission computed tomography (SPECT) also allows for the assessment of nonperfusion parameters such as transient ischemic dilatation (TID) and a reduction of ejection fraction (EF) with stress imaging. This study aimed to evaluate the diagnostic value of TID and EF reserve for the detection of significant multivessel coronary artery disease (CAD). A total of 206 patients with suspected stable CAD prospectively underwent gated stress-rest Tc-tetrofosmin SPECT and invasive coronary angiography with routine fractional flow reserve (FFR) measurements, irrespective of imaging results. Left ventricular volumes, TID, and EF reserve were assessed and compared with FFR-defined severity of CAD. According to FFR, 92 (45%) patients had significant CAD, whereas 25 (12%) showed 2-vessel disease (VD) and 22 (11%) showed 3-VD. With an increasing extent of CAD, TID values and EF reserve did not change significantly (P=0.07 and 0.42 for trend, respectively). Conversely, absolute left ventricular volumes and EF differed significantly among groups of CAD severity (P<0.01 for all trends). SPECT-derived TID and EF reserve did not differ between patients with high-risk CAD (3-VD) and low risk or no significant CAD. Therefore, the present results advocate exerting caution when using these ancillary findings in clinical practice.

Validation of automated quantification of myocardial perfusion single-photon emission computed tomography using Heart Score View in patients with known or suspected coronary artery disease.

Heart Score View (HSV) is a free software package for automated quantification of myocardial single photon emission computed tomography (SPECT) imaging using a standard Windows computer. We compared scoring results of myocardial perfusion among visual analysis, Quantitative Perfusion SPECT (QPS), and HSV in patients with known or suspected coronary artery disease.This study included 75 consecutive patients with known or suspected coronary artery disease who underwent adenosive stress-rest Tl-201 SPECT. Analysis of myocardial perfusion SPECT was performed on a standard 17-segment model visually and using QPS and HSV.There were 54 male and 21 female patients with a mean age of 70.5 ± 10.7 years. Thirteen patients (17%) had prior myocardial infarction. Summed stress score (SSS) and summed rest score (SRS) in the mid and basal areas were significantly higher on HSV than visual analysis or QPS. There was no significant difference in SDS in the whole area among the 3 methods. Similar results were found even in patients without prior myocardial infarction. Manual setting of the left ventricular cavity improved the correlations of SSS, SRS and SDS between HSV and the other methods.Our data suggested that HSV was comparable with visual analysis or QPS in scoring myocardial perfusion when manual setting of the left ventricular cavity is applied.

The interaction of exercise ability and body mass index upon long-term outcomes among patients undergoing stress-rest perfusion single-photon emission computed tomography imaging

The obesity paradox has been reported in several populations of patients with cardiovascular disease. Recent data have shown that physical fitness may attenuate the obesity paradox. Patients who undergo pharmacologic stress testing are known to have a higher risk of mortality than those who can exercise. The purpose of this study is to determine the interaction of obesity and exercise ability on survival among patients with a normal stress-rest single-photon emission computed tomography (SPECT). A total of 5,203 (60 ± 13 years, male 37%) patients without a history of heart disease and a normal stress-rest SPECT between the years 1995 and 2010 were included in this analysis. Body mass index categories were defined according to the World Health Organization classification: normal weight, 18.5 to 24.9 kg/m(2); overweight, 25 to 29.9 kg/m(2); and obese, ≥30 kg/m(2). Patients were divided into 3 groups based on their ability to exercise: those who reached ≥6 METs on exercise, those who attained a level of <6 METs, and those who required pharmacologic stress. Patients in each of these fitness groups were further divided into 3 subgroups based on their body mass index. There were 939 (18%) deaths during a mean follow-up of 8.1 ± 4.1 years, for an overall event rate of 2.3%/y. Both exercise to ≥6 METs and being obese were associated with lower mortality. Adjusted multivariate analysis using the obese high-fit patients as the reference showed a wide heterogeneity in annualized mortality rates according to exercise and weight status, with annualized event rates which varied from 0.6%/y in the obese subjects who were physically fit to 5.3%/y among healthy subjects who underwent pharmacologic stress testing (P < .001). Stress mode and body weight impacted long-term survival in patients with a normal stress SPECT. The benefit of being physically fit was evident in all weight groups, as was the adverse effect of being unable to exercise. However, with regard to body weight, there was a paradoxical survival advantage for those patients who were overweight and obese, regardless of their exercise ability.

Temporal Trends in the Frequency of Inducible Myocardial Ischemia During Cardiac Stress Testing

This study sought to assess whether the frequency of inducible myocardial ischemia during stress-rest single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has changed over time. The prevalence of cardiac death and other clinical cardiac events have declined in recent decades, but heretofore no study has examined if there has been a temporal change in the frequency of inducible myocardial ischemia during cardiac stress testing. We assessed 39,515 diagnostic patients undergoing stress-rest MPI between 1991 and 2009. Patients were assessed for change in demographics, clinical symptoms, risk factors, and frequency of abnormal and ischemic SPECT-MPI. There was a marked progressive decline in the prevalence of abnormal SPECT studies, from 40.9% in 1991 to 8.7% in 2009 (p < 0.001). Similarly, the prevalence of ischemic SPECT-MPI declined, from 29.6% to 5.0% (p < 0.001), as did the prevalence of severe ischemia. The decline of SPECT-MPI abnormality occurred among all age and symptom subgroups, falling to only 2.9% among recent exercising patients without typical angina. We also noted a progressive trend toward performing more pharmacological rather than exercise stress in all age and weight groups, and pharmacological stress was more likely than exercise to be associated with SPECT-MPI abnormality (odds ratio: 1.43, 95% confidence interval: 1.3 to 1.5; p < 0.001). Over the past 2 decades, the frequency and severity of abnormal stress SPECT-MPI studies has progressively decreased. Notably, the frequency of abnormal SPECT-MPI is now very low among exercising patients without typical angina. These findings suggest the need for developing more cost-effective strategies for the initial work-up of patients who are presently at low risk for manifesting inducible myocardial ischemia during cardiac imaging procedures.

Stress variables add differential diagnostic information between ischemic and nonischemic cardiomyopathy over myocardial perfusion SPECT imaging

Noninvasive differentiation between ischemic cardiomyopathy (ICM) and nonischemic (NICM) cardiomyopathy is frequently difficult. The aim of this study was to analyze the value of stress test and stress-rest gated single-photon emission computed tomography (SPECT) criteria to differentiate between ICM and NICM. Data pertaining to 145 consecutive patients (mean age: 63±11 years, 24 women) assessed by means of stress-rest gated SPECT with Tc-tetrofosmin, with left ventricular ejection fraction less than or equal to 40% (107 patients with ICM and 38 with NICM according to coronary angiography) and known coronary anatomy, were analyzed. Multivariate analyses of gated SPECT variables identified a summed stress score greater than 21 [odds ratio (OR) 7.67, 95% confidence interval (CI): 2.85-20.58)] and divergent pattern (OR 6.84, 95% CI: 1.83-25.5) as predictors of ICM, and analysis of exercise test variables disclosed metabolic equivalents less than or equal to 7.3 (OR 10.75, 95% CI: 3.64-31.81) and ST depression of at least 1 mm (OR 6.97, 95% CI: 1.42-34.3) as independent predictors of ICM. The exercise test variables had a significant additional predictive value of ICM over gated SPECT variables (P<0.001). Estimated functional capacity and ST depression improve the diagnostic value of stress-rest SPECT to differentiate between ICM and NICM.

負荷&amp;ndash;安静心筋血流SPECTにおける一度のCT撮影による減弱補正法の検討

Attenuation correction (AC) of myocardial perfusion stress-rest single photon emission computed tomography (SPECT) with hybrid SPECT/computed tomography (CT) is effective. But because CT scan is done two times, the radiation exposure of patients increases. Therefore, we suggested a new method of AC that can correct attenuation of SPECT images acquired during a rest examination by using the CT scan during a stress examination. AC was done using one CT scan and we evaluated the clinical appropriateness of using this method. Matters of this study were (1) positional reproducibility of data analysis machine (Xeleris) (2) phantom study: accuracy of registration by manual and repetition reproducibility (3) clinical study using (99m)Tc-tetrofosmin. Comparison methods were analyzed by calculating the difference perfusion (Dp) with 17-segments model of American Heart Association and visual evaluation of three axis images in the myocardium. In the phantom study, because most of the score of 17-segments accord (Dp≤1), it was considered that the shift on SPECT/CT's bed was reproduced by the shift on Xeleris. And it is shown that AC with CT scan on deference point was accuracy. In the clinical study, there were a few differences in Dp (Dp≤4) and approximately equal evaluation on visual evaluation was provided, which compared with conventional methods. Because AC of myocardial perfusion stress-rest SPECT by one CT scan showed that it was approximately equal in evaluation compared with conventional methods, we expect to be able to use this method in clinical cases.

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

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™. 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. 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. 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.

Assessment of automated scintigram alignment in the stackgram domain for cardiac stress–rest SPECT studies

Single photon emission computed tomography (SPECT) provides a method to obtain three-dimensional images of blood perfusion. In cardiac stress–rest SPECT studies, coronary artery disease can be examined by comparing intensity differences of the acquired images of the heart at stress and rest. The stress–rest image pair needs to be aligned into the same spatial position and orientation in order to compare the images in an automated and reproducible manner. In this work, we study a novel stackgram-based alignment algorithm for cardiac stress–rest SPECT data. The stackgram approach allows the alignment of the acquired raw data prior to image reconstruction, unlike conventional alignment techniques.

Yield of Early Rest and Stress Myocardial Perfusion Single-Photon Emission Computed Tomography and Electrocardiographic Exercise Test in Patients With Atypical Chest Pain, Nondiagnostic Electrocardiogram, and Negative Biochemical Markers in the Emergency Department

There are no studies in which diagnostic yield of early rest myocardial perfusion gated single-photon emission computed tomography (SPECT), electrocardiographic exercise testing, and stress SPECT were compared in patients with atypical chest pain, nondiagnostic electrocardiograms (ECGs), and negative markers of myocardial damage in the emergency department. A prospective study of 96 patients who presented with atypical chest pain and nondiagnostic ECG, but without elevated markers of necrosis, was performed. All underwent rest gated SPECT using technetium-99m methoxyisobutyl isonitrile within 6 hours after pain subsided followed by an electrocardiographic exercise test to obtain stress-rest SPECT images. After 1 year, there were no deaths and coronary artery disease was confirmed in only 5 patients. Negative predictive values of the 3 techniques were high (99%, 96%, and 100%, respectively), but positive predictive values were low (27%, 22%, and 14%, respectively). Sensitivities of early SPECT (80%) and stress SPECT (100%) were higher than for the electrocardiographic exercise test (40%). In conclusion, in patients with atypical chest pain, nondiagnostic ECG, and negative biochemical markers, negative predictive values of the 3 tests analyzed are very high. The sensitivity of radionuclide tests is higher, but their widespread use does not appear warranted because their positive predictive value and incidence of complications is low.

Silent Myocardial Ischemia in Patients With Symptomatic Intracranial Atherosclerosis

Optimization of coronary risk evaluation in stroke patients has been encouraged. The relationship between symptomatic intracranial atherosclerosis and occult coronary artery disease (CAD) has not been evaluated sufficiently. We aimed to investigate the prevalence of silent myocardial ischemia in patients with symptomatic intracranial atherosclerosis and to identify factors associated with its presence. From 186 first-ever transient ischemic attack or ischemic stroke patients with intracranial stenoses, 65 fulfilled selection criteria, including angiographic confirmation of a symptomatic atherosclerotic stenosis and absence of known CAD. All patients underwent a maximal-stress myocardial perfusion single-photon emission computed tomography (SPECT). Lipoprotein(a) [Lp(a)], C-reactive protein, and homocysteine (Hcy) levels were determined before SPECT. Stress-rest SPECT detected reversible myocardial perfusion defects in 34 (52%) patients. Vascular risk factors associated with a pathologic SPECT were hypercholesterolemia (P=0.045), presence of >2 risk factors (P=0.004) and high Lp(a) (P=0.023) and Hcy levels (P=0.018). Ninety percent of patients with high Lp(a) and Hcy levels had a positive SPECT. Existence of a stenosed intracranial internal carotid artery (ICA; odds ratio [OR], 7.22, 2.07 to 25.23; P=0.002) and location of the symptomatic stenosis in vertebrobasilar arteries (OR, 4.89, 1.19 to 20.12; P=0.027) were independently associated with silent myocardial ischemia after adjustment by age, sex, and risk factors. More than 50% of the patients with symptomatic intracranial atherosclerosis and not overt CAD show myocardial perfusion defects on stress-rest SPECT. Stenosed intracranial ICA, symptomatic vertebrobasilar stenosis and presence of high Lp(a) and Hcy levels may characterize the patients at a higher risk for occult CAD.

Clinical validation of technetium-99m MIBI-gated single-photon emission computed tomography (SPECT) for avoiding false positive results in patients with left bundle-branch block: comparison with stress-rest nongated SPECT.

Septal perfusion defects are common on myocardial perfusion single-photon emission computed tomography (SPECT) slices in patients with left bundle-branch block (LBBB) in the absence of coronary artery disease. The use of gated myocardial perfusion SPECT imaging in such patients should be clinically validated. The aims of this study were, therefore, to validate clinically the use of gated myocardial SPECT imaging to avoid false positive septal perfusion defects in patients with LBBB and to compare nongated and gated SPECT imaging techniques in the same patients in the same imaging session. We performed stress-rest myocardial perfusion SPECT and resting gated SPECT using Technetium-99m MIBI in 25 patients with LBBB and in 6 control subjects. Stress-rest SPECT images and end-diastolic and end-systolic gated SPECT slices were assessed visually and quantitatively (septum/lateral wall count ratio). Coronary angiography was performed in 15 patients with LBBB and in all 6 control subjects. Stress-rest (nongated) SPECT slices and end-diastolic and end-systolic gated SPECT images were normal in all control subjects. Stress-rest (nongated) SPECT imaging revealed septal perfusion defect in 20 (11 reversible, 9 irreversible) patients with LBBB, whereas the figures were 15 and 5 for end-systolic and end-diastolic gated SPECT images, respectively. Coronary angiography results were normal in all control subjects and in 15 patients with LBBB. Quantitative analysis of gated SPECT images revealed no statistically significant difference between patients with LBBB and control subjects in end-diastolic mean septum/lateral wall count values (0.86 +/- 0.19 in LBBB vs. 0.98 +/- 0.15 in normal subjects, p > 0.05), but the difference was statistically significant for end-systolic, stress, and rest values (p < 0.001 for all). Gated SPECT imaging, particularly end-diastolic images, revealed fewer false positive results and thus can be used to avoid false positive septal perfusion defects commonly seen in stress-rest (nongated) myocardial perfusion SPECT in patients with LBBB.