Stress-rest Protocol Research Articles

Duration of adenosine-induced myocardial hyperaemia: insights from quantitative 13N-ammonia positron emission tomography myocardial perfusion imaging.

This study aimed to assess the impact of adenosine on quantitative myocardial blood flow (MBF) in a rapid stress-rest protocol compared with a rest-stress protocol using 13N-ammonia positron emission tomography (PET) myocardial perfusion imaging (MPI) and to gain insights into the time dependency of such effects. Quantitative MBF at rest (rMBF) and during adenosine-induced stress (sMBF) and myocardial flow reserve (MFR) were obtained from 331 retrospectively identified patients who underwent 13N-ammonia PET MPI for suspected chronic coronary syndrome and who all exhibited no perfusion defects. Of these, 146 (44.1%) underwent a rapid stress-rest protocol with a time interval (Δtstress-rest) of 20 ± 4 min between adenosine infusion offset and rest imaging, as per clinical routine. The remaining 185 (55.9%) patients underwent a rest-stress protocol and served as the reference. Groups did not differ regarding demographics, risk factors, medication, left ventricular function, and calcium scores. rMBF was significantly higher in the stress-rest vs. the rest-stress group [0.80 (interquartile range 0.66-1.00) vs. 0.70 (0.58-0.83) mL·min-1·g-1, P < 0.001], and, as sMBF was identical between groups [2.52 (2.20-2.96) vs. 2.50 (1.96-3.11), P = 0.347], MFR was significantly lower in the stress-rest group [3.07 (2.43-3.88) vs. 3.50 (2.63-4.10), P = 0.007]. There was a weak correlation between Δtstress-rest and rMBF (r = -0.259, P = 0.002) and between Δtstress-rest and MFR (r = 0.163, P = 0.049), and the proportion of patients with abnormally high rMBF was significantly decreasing with increasing Δtstress-rest. Intravenously applied adenosine induces a long-lasting hyperaemic effect on the myocardium. Consequently, rapid stress-rest protocols could lead to an overestimation of rMBF and an underestimation of MFR.

Machine learning-based diagnosis and risk classification of coronary artery disease using myocardial perfusion imaging SPECT: A radiomics study

This study aimed to investigate the diagnostic performance of machine learning-based radiomics analysis to diagnose coronary artery disease status and risk from rest/stress Myocardial Perfusion Imaging (MPI) single-photon emission computed tomography (SPECT). A total of 395 patients suspicious of coronary artery disease who underwent 2-day stress-rest protocol MPI SPECT were enrolled in this study. The left ventricle myocardium, excluding the cardiac cavity, was manually delineated on rest and stress images to define a volume of interest. Added to clinical features (age, sex, family history, diabetes status, smoking, and ejection fraction), a total of 118 radiomics features, were extracted from rest and stress MPI SPECT images to establish different feature sets, including Rest-, Stress-, Delta-, and Combined-radiomics (all together) feature sets. The data were randomly divided into 80% and 20% subsets for training and testing, respectively. The performance of classifiers built from combinations of three feature selections, and nine machine learning algorithms was evaluated for two different diagnostic tasks, including 1) normal/abnormal (no CAD vs. CAD) classification, and 2) low-risk/high-risk CAD classification. Different metrics, including the area under the ROC curve (AUC), accuracy (ACC), sensitivity (SEN), and specificity (SPE), were reported for models’ evaluation. Overall, models built on the Stress feature set (compared to other feature sets), and models to diagnose the second task (compared to task 1 models) revealed better performance. The Stress-mRMR-KNN (feature set-feature selection-classifier) reached the highest performance for task 1 with AUC, ACC, SEN, and SPE equal to 0.61, 0.63, 0.64, and 0.6, respectively. The Stress-Boruta-GB model achieved the highest performance for task 2 with AUC, ACC, SEN, and SPE of 0.79, 0.76, 0.75, and 0.76, respectively. Diabetes status from the clinical feature family, and dependence count non-uniformity normalized, from the NGLDM family, which is representative of non-uniformity in the region of interest were the most frequently selected features from stress feature set for CAD risk classification. This study revealed promising results for CAD risk classification using machine learning models built on MPI SPECT radiomics. The proposed models are helpful to alleviate the labor-intensive MPI SPECT interpretation process regarding CAD status and can potentially expedite the diagnostic process.

Non-Invasive Assessment of Myocardial Perfusion Abnormality in Type 2 Diabetic Patients Without Symptoms of Coronary Artery Disease by SPECT-MPI

Introduction: Coronary artery disease (CAD) is the most common chronic macrovascular complication of diabetes mellitus. Diabetic patients have a high incidence of silent ischemia and MI due to autonomic neuropathy. SPECT imaging is a well-established, non-invasive procedure that offers perfusion and functional information for diagnosis and risk stratification, facilitating the early detection of CAD. Objective: To detect myocardial perfusion abnormality by SPECT-MPI in type 2 diabetic patients without symptoms of CAD. Methods: A total of eighteen diabetic patients with no history of typical CAD, with or without risk factors, underwent gated SPECT-MPI using 99mTc-sestaMIBI. A single-day stress–rest protocol with adenosine was done in each patient. Result: Six out of eighteen patients (33.3%) showed abnormal scans suggestive of myocardial ischemia or infarction. Four of these patients had reversible perfusion defects, one had a fixed perfusion defect, and one had a mixed defect. Among these patients, single vessel territory was involved in three patients, and three patients had involvement in double vessel territories. Regarding the summed stress score (SSS) value, most of the patients (four) had mild risk, whereas moderate and severe risk of a future cardiac event were observed in one patient each. In addition, two patients had left ventricular dysfunction (EF&lt; 45%). Five patients with normal MPI and two patients with abnormal myocardial perfusion scans had high transient ischemic dilatation (TID). Risk factors such as male sex, hypertension, hyperlipidemia, obesity, and family history of CAD were not significantly correlated with abnormal scans. But abnormal scans were significantly related to a longer duration of diabetes (P = 0.038). Conclusion: This study showed that despite being asymptomatic, a considerable portion of diabetic patients had perfusion abnormalities, not just ischemia but also infarctions. Moreover, some of these patients are at high risk for future cardiac events as assessed by SSS, TID, and LVEF. Bangladesh J. Nuclear Med. 25(2): 110-116, 2022

Diagnosis, performance and added value of assessing ventricular dyssynchrony by phase analysis in patients with three-vessel disease: A single-center cross-sectional study in Mexico

BackgroundThree-vessel disease (3VD) is a cardiovascular disorder that affects the three main coronary arteries. Gated myocardial perfusion SPECT (GMPS) evaluates ventricular function, synchrony, and myocardial perfusion. However, the diagnostic performance of GMPS parameters to assess 3VD has not been fully explored. AimsTo assess the univariate performance capacity of GMPS parameters, and to evaluate whether phase parameters could provide additional predictive value for the detection of patients with 3VD compared to control subjects. MethodsWe designed paired retrospective samples of GMPS images of patients with 3VD (stenosis > 70% of left anterior descending, right coronary, and circumflex coronary arteries) and without 3VD. A GMPS in rest-stress protocol was performed using 99mTc-Sestamibi and thallium and analyzed with the 3D method. Area under the receiver-operating characteristic curves (AUROC), decision curve analyses and diagnostic test performance were obtained for univariable analyses and stepwise binomial logistic regression for multivariable performance. Results474 Patients were included: 237 with 3VD (84% males, mean age 61.7 ± 9.9 years) and 237 with normal GMPS (51% women, mean age 63.8 ± 10.6 years). The highest AUROC for perfusion parameters were recorded for SSS, SRS and TID. For dyssynchrony parameters, both entropy and bandwidth in rest and stress phases displayed the highest AUROC and diagnostic capacity to detect 3VD. A multivariate model with SRS ≥ 4, SDS ≥ 2, TID > 1.19 and sBW ≥ 48° displayed the highest diagnostic capacity (0.923 [95% CI 0.897-0.923]) to detect 3VD. ConclusionPerfusion and dyssynchrony were the parameters which were most able to discriminate patients with 3VD from those who did not have CAD.

Association of Calcium Index and Myocardial Blood Flow in Non-Obstructive Atherosclerotic Lesion of the Coronary Arteries

Background. Over the past few years, scientific data have demonstrated that patients with non-obstructive coronary artery disease can have high risk for adverse cardiovascular events (ACE) despite the absence of severe coronary obstruction. From this point of view, some patients require special monitoring and treatment; we have to find new methods for stratification of the risk of ACE. Aims to study the association of coronary artery calcification (CCA) with indicators of myocardial blood flow (MBF) and myocardial flow reserve (MFR) in patients with non-obstructive coronary artery disease (CAD). Methods. The study included patients (n = 52) with non-obstructive CAD ( 50%), identified by CCTA. All patients received dynamic myocardial SPECT according to the two-day rest-stress protocol with the radiopharmaceutical agent 99mTc-methoxy-isobutyl-isotnitrile and the pharmacological stress-test (adenosine triphosphate 160 mcg/kg/min) to determine quantitative indicators of MBF and MFR. Depending on the calcium index (CI), three groups of patients were formed: 1 without CCA (CI = 0 Agatston units), 19 patients; 2 Mild CCA (CI = 1100 Agatston units), 21 patients; 3 Moderate CCA (CI = 101400 Agatston units), 12 patients. Results. The study included 52 patients (age 55.0 9.8 years, 36 men). The groups differed statistically significantly (p 0.05) in terms of quantitative scintigraphic parameters: stress-MBF, MFR and MBF. When analyzing the groups in pairs, it was found that stress-MBF and MBF were significantly lower in the group with moderate CCA compared to the group without CCA, and MFR was lower in the group with moderate CCA compared to the groups without CCA and with mild CCA. Correlation analysis revealed significant relationships between CI and scintigraphic parameters: stress-MBF ( = 0.46; p = 0.003), MFR ( = 0.48; p = 0.001), MBF ( = 0.48; p = 0.0008), SSS ( = 0.34; p = 0.02) and SDS ( = 0.28; p = 0.046). Conclusions. Even with non-obstructive CAD, identified by CCTA, there is a decrease in MBF and MFR inversely proportional to the level of CI, which can be considered as an early marker of impaired vasodilation reserve of the vascular wall, which develops in atherosclerosis of the coronary artery.

Abstract 15033: Chronic Thromboembolic Pulmonary Hypertension Patients Have Reduced Bi-Ventricular Myocardial Perfusion Reserve, Which Improves Following Pulmonary Thromboendarterectomy

Introduction: This study seeks to determine whether bi-ventricular myocardial perfusion reserve (MPR) is reduced in patients with chronic thromboembolic pulmonary hypertension (CTEPH) compared to a control group using quantitative myocardial perfusion MRI. Methods: We prospectively enrolled 4 CTEPH patients (55±14 years, 4 males) and performed stress-rest (10 min apart) protocol using our 5-fold accelerated radial perfusion sequence. In one patient, we repeated stress-rest perfusion acquisition following pulmonary thromboendarterectomy (PTE). As a control group, we retrospectively identified 8 subjects (49±12 years, 5 males) with no evidence of vascular late gadolinium enhancement or perfusion defects who underwent a similar stress-rest protocol. The pixel-wise stress-rest myocardial blood flow (MBF) maps and MPR were quantified for both the left ventricular (LV) and right ventricular (RV) free walls. Two sample t-test was used to compare between the CTEPH and control groups. Results: Figure 1a shows representative stress and rest MBF maps and the corresponding MPR values comparing a CTEPH patient and a control subject. Summarizing the results of all patients (Figure 1b), compared to the control group, the CTEPH group had significantly (p &lt; 0.05) lower stress LV MBF (1.56 ± 0.34 vs. 2.66 ± 0.50 ml/g/min), RV MBF (1.48 ± 0.19 vs. 2.56 ± 0.53 ml/g/min), LV MPR (1.65 ± 0.43 vs. 2.32 ± 0.50), and RV MPR (1.59±0.46 vs. 2.50 ± 0.53), but non-significant difference (p &gt; 0.05) in resting LV MBF (0.96 ± 0.12 vs. 1.21 ± 0.43 ml/g/min) and RV MBF (0.96 ± 0.14 vs. 1.07 ± 0.36 ml/g/min). In one patient, PTE improved RV MPR from 1.43 to 2.49 as well as LV MPR from 1.24 to 2.36. Conclusions: This study suggests that both RV and LV MPR are reduced in CTEPH patients compared with controls and that PTE may improve RV as well as LV MPR in CTEPH patients. Future studies include additional enrollment of CTEPH patients, determining the diagnostic and prognostic role of RV and LV MPR in the context of PTE.

TECHNETIUM-99M MIBI GATED MYOCARDIAL PERFUSION SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY IMAGING – VALIDATION OF STRESS ONLY PROTOCOL

Objective: To validate ‘stress only’ protocol against ‘rest stress protocol in normal and essentially normal cases undergoing Tc99m MIBI gated myocardial perfusion Single Photon Emission Computed Tomography imaging.&#x0D; Study Design: A retrospective observational study.&#x0D; Place and Duration of Study: Department of Nuclear Cardiology, Armed Forces Institute of Cardiology/National Institute of Heart Disease, Rawalpindi, Pakistan, from Jul to Sep 2019.&#x0D; Methodology: 136 cases were included. Patients underwent Tc-99m gated Single Photon Emission Computed Tomography MPI using a single day, rest/stress protocol. The rest study was performed first with 8-10 mCi Tc-99m MIBI followed by stress study, 3 hours later with 3 times the rest dose. The most common stress technique was pharmacological stress and bicycle ergometer exercise with 0.14 mg/kg/min adenosine infusion. Few patients underwent physical stress using Bruce protocol, achieving a minimum of 85% of the target heart rate. Mages–stress followed by rest–were evaluated by two experienced nuclear cardiologists (blinded to the MPI reports) and interpreted as ‘normal’ or ‘essentially normal’.&#x0D; Results: Evaluation of stress-only and rest-stress Single Photon Emission Computed Tomography myocardial images yielded a concordance rate of 84.56% with Cohen’s kappa coefficient of 0.69.&#x0D; Conclusion: Substantial agreement and good concordance were found in normal and essentially normal ‘stress only’ and ‘rest stress protocols.

The presentation of clinical results of radiolabelling of 99mTc-MIBI complex using ultrasound technique for myocardial perfusion SPECT scanning

BackgroundThe aim of this study was to introduce a new clinical procedure (ultrasound irradiation technique) as an alternative method for the preparation of sestamibi kits as opposed to the boiling water bath technique. The main proposal of this study was to evaluate the clinical application of ultrasound method, preparation of 99mTc-MIBI complex and biodistribution of the heart in comparison with 99mTc-MIBI complex, which was prepared using the boiling water technique. Materials and methodsForty MIBI kits were supplied for twenty patient volunteers. 740–3700MBq (20–100mCi) freshly eluted solution of Na+99mTcO4− was added to freeze-dry MIBI Kits (The first day up to 20 kits and the second day another 20 kits with the same amount was used). Moreover, twenty kits were labeled applying the ultrasound radiation method as an alternative approach (The vials were sonicated in thermo noted bath (Elma, P=50W, Germany) at 65±0.5̊C and for 60±1seconds), and another twenty kits were provided applying boiling water bath method as a standard approach. Twenty patient volunteers (8 men and 12 women; age range 30–72, median 52.45 years) took part in this research. These volunteers had originally been referred to the hospital for myocardial perfusion imaging. The twenty volunteer patients were divided into two groups (each group contained ten people): group A (consisted of 3 men and 7 women with an age range from 36 to 67 years and a mean age of 51.7 years), and group B (involving 5 men and 5 women with an age range from 30 to 72 years and an average age of 50.3 years). The 99mTc-MIBI complex samples provided by ultrasound method were injected into group A subjects intravenously and group B received 99mTc-MIBI vials provided by boiling water bath approach (intravenous injection). In this research, the myocardial perfusion-SPECT was performed applying a rest-stress protocol which is carried-out between two isolated days for all volunteer patients. ResultsThe results obtained in this research applying radio-HPLC and ITLC, suggest that radio-labeling of MIBI vial with 99mTc can be achieved with high efficacy and appropriate acceptance applying the ultrasound method as a novel approach. The imaging research applying SPECT indicated that the 99mTc-MIBI complex samples that were prepared applying an ultrasound irradiation approach indicate very similar biodistribution in the heart, thyroid, lung, liver, gallbladder, kidneys, stomach, GI and bladder of the volunteer patients. Non-habitual aggregation of 99mTc-MIBI samples were not observed in our approach. ConclusionsThe results of this research suggest that the sonication approach can be proposed for preparation of 99mTc-MIBI radio-complex samples. The reaction time to provide radio-complex can be considerably decreased compared to the boiling water bath approach. This main development could decrease the potential risk to the patient to inhibit any delay in emergency situations i.e. acute therapy, especially for myocardial infarction patients in clinical practice.

Changes in left ventricle myocardial volume during stress test using cadmium-zinc-telluride cardiac imaging: Implications in coronary artery disease

BackgroundCadmium-zinc-telluride (CZT) SPECT allows the estimation of left ventricle myocardial volume (LVMV). We tested the clinical relevance of rest-stress LVMV changes (Δ LVMV) in detecting coronary artery disease (CAD, coronary stenosis > 70%), using CZT-SPECT. MethodsWe prospectively enrolled 512 consecutive patients with known or suspected CAD (mean age: 70.3 ± 9.2 years, 72% male) for stress-rest myocardial perfusion imaging (MPI, single-day stress-rest protocol). We quantified summed stress scores (SSS), summed rest scores, and summed difference scores, together with LVMV and ejection fraction (EF) after stress and at rest. All patients underwent coronary angiography within 30 days. ResultsTwo hundred seventy-two patients had CAD at coronary angiography. ΔLVMV ≤ 5 mL, corresponding to 6% of change from rest LVMV, was the best predictor of CAD (AUC = 0.831, 79% sensitivity, 82% specificity), irrespective of the stress protocol (dipyridamole or exercise stress) and independently of MPI-SSS, LV EF, and clinical history (P = 0.004). Integrated discrimination improvement (IDI) and net reclassification improvement (NRI) were significant for the addition of ΔLVMV ≤ 5 mL (IDI = 6.1%, P < 0.0001; NRI = 29.7%, P = 0.02) to MPI-SSS, whereas the other parameters were not. ConclusionsThe evaluation of ΔLVMV using CZT-SPECT can improve the diagnostic accuracy in predicting the presence of CAD when added to conventional MPI.

The role of stress-induced dyssynchrony obtained from nuclear modalities in evaluation of high-risk patients after surgical treatment of ischemic cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: None. Background Mechanical dyssynchrony (MD) is a well-known parameter witch has prognostic value [1]. Stress tests can be used to unmask MD. However, stress-induced changes in left ventricle (LV) MD by data of nuclear imaging modalities are not well-understood, especially its predictive value [2]. Purpose. To assess the role of stress-induced changes of LV MD obtained by nuclear modalities in evaluating high-risk patients after surgical treatment of ischemic cardiomyopathy (ICM). Methods. Sixty-nine patients with ICM were enrolled. Before surgical treatment all patients underwent gated myocardial perfusion imaging (gMPI) (Tc99m-MIBI; 2 days stress-rest protocol, adenosine 140mkg/kg/min) and gated blood pool SPECT (gBPS) (rest – stress, dobutamine doses of 5/10/15 µg/kg/min). After surgical treatment patients were divided into 2 groups: with (n = 21) and without (n = 48) complicated course of early postoperative period (death, intra-aortic balloon pump, extra inotropic support). The following parameters were estimated: summed stress score (SSS), summed rest score (SRS), summed different score (SDS); phase mean, phase standard deviation (PSD) and histogram bandwidth (HBW) (% from cycle for MPI; degrees for gBPS); phase entropy (%, only by gBPS). Stress-induced changes (Δ) were calculated for MPI indices as [stress value-rest value], for gBPS indices as [value on each dobutamine dose-rest value]. For gBPS the maximum changes of MD were calculated as well. Results. Rest gBPS MD correlated with SRS better than rest gMPI (gMPI: PSD r = 0.31, p = 0.005; HBW r = 0.28, p = 0.008; gBPS: PSD r = 0.47, p &amp;lt; 0.001; HBW r = 0.36, p = 0.006; entropy r = 0.39, p = 0.003). Stress gBPS MD correlated better with post stress gMPI MD at the dobutamine dose of 5µg/kg/min. An following increase of the dobutamine dose led to a decrease in the r-value, but it remained significant for all indices (tab.1). Stress-induced MD changes didn’t correlate between gMPI and gBPS. Mann-Whitney test showed significant differences in SDS (p = 0.02) between the groups. Both methods didn’t show any differences at rest study. Stress-induced changes of MD showed differences between groups in only ΔEntropy rest-10µg/kg/min (p = 0.02) and maximum ΔEntropy (p = 0.01) by gBPS, as well as Δphase mean (p = 0.03) by gMPI. Logistic regression analysis showed that only maximum ΔEntropy has prognostic value in prediction of the course of early postoperative period (OR 1.2 95%CI 1.04; 1.37). ROC-analysis showed sensitivity of 80% and specificity of 55% with AUC of 0.7 for cut-off value &amp;gt;0. Conclusion. LVMD obtained from gBPS is associated with SRS better than those obtained from gMPI. Dyssynchrony indices obtained from gMPI with adenosine stress-test have a week to moderate correlation with those obtained from dobutamine gBPS, and correlation decrease with increasing of dobutamine dose. Only maximum ΔEntropy obtained from dobutamine gBPS is associated with the adverse course of early postoperative period in patients with ICM.

High residual platelet aggregation in patients with coronary artery disease: a new methodological approach to detection

Aim. To develop a new methodological approach to assessment of collagen-induced platelet aggregation in patients with coronary artery disease (CAD) and to determine the quality of various methods for detecting high residual platelet reactivity (HRPR) to predict the risk of myocardial perfusion disturbance. Materials and methods. 36 patients (10 men and 26 women) aged 41–83 years and having stable CAD were examined. All patients had been undergoing continuous antiaggregation therapy for 6 months. We evaluated platelet aggregation using a laser analyzer with collagen as an aggregation inducer by the standard method 1 and our own patented method 2. The degree of platelet aggregation (%) and the size of aggregates in relative units (r.u.) in platelet-rich plasma were estimated. Myocardial perfusion scintigraphy with 99mTc-methoxy-isobutylisonitrile was performed according to a two-day stress-rest protocol. The summed stress score (SSS) values were used for analysis. SSS &lt; 4 was regarded as normal myocardial perfusion. Results . The degree of platelet aggregation according to method 1 was 12 (5; 64)%, the aggregate size was 3 (2; 7) r.u. The degree of platelet aggregation according to method 2 was 44 (13; 78)%, and the aggregate size was 5 (4; 8) r.u. Method 2 allowed to diagnose the presence of myocardial ischemia with an aggregation degree ≥ 44.9% with sensitivity of 84% and specificity of 92% (area under the curve (AUC) = 0.89; p &lt; 0.0001; odds ratio (OR) 2.18; 95% confidence interval (CI) 0.57–0.98) and an increase in aggregate size ≥ 4.80 r.u. with sensitivity of 84% and specificity of 84% (AUC = 0.95; p &lt; 0.00001; OR 5.83; 95% CI 0.72–0.99). Conclusion. In patients with CAD, detection of high rates of collagen- induced platelet aggregation using the patented technique is associated with the risk of impaired myocardial perfusion. The developed new methodological approach to detection of HRPR allowed to determine high risk of atherothrombotic complications in additional 22% of the examined patients.

The prognostic significance of stress-only myocardial perfusion scan: A 5 year observational study.

Stress-only myocardial perfusion imaging protocol has a prognostic value similar to that of a stress-rest protocol. The aim of the study was to assess stress myocardial perfusion by gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (GSMPI) in patients who had a normal stress-only study 4.9 years (mean time) before and assess the possible influence of various factors on the results. Three hundred and forty patients who had a normal stress-only study in the past, were reexamined with GSMPI after a mean period of 4.9 years. Thirty out of 340 patients (8.8%) had an ischemic result on stress and were therefore submitted to a rest study. Differences between normal and pathological results across levels of potential prognostic factors (age, gender, diabetes mellitus, dyslipidemia, arterial hypertension, smoking and family history), symptoms,left ventricular ejection fraction (LVEF) on ultrasound (U/S), coronary angiography and pre-test probability did not prove statistically significant. On multivariable analysis patients with the combination of family history, diabetes mellitus and hypertension had a 10.7 times higher risk of a pathological scan than the patients without. The information delivered by stress-only GSMPI proved to be a prognostically reliable method for follow-up of low and intermediate pretest probability coronary artery disease (CAD) patients. The 91.2% of the patients with an initial normal stress-only GSMPI had a repeat normal stress-only GSMPI after a mean period of 4.9 years. The combination of family history, diabetes mellitus and hypertension increases the risk of a pathological scan significantly.

Myocardial perfusion imaging and appropriateness of the test for preoperative cardiac risk evaluation in an Iranian population: clinical role of Duke Activity Status Index.

For preoperative radionuclide myocardial perfusion imaging, metabolic equivalent is one of the key factors to evaluate the appropriateness. Duke Activity Status Index is a practical method to calculate metabolic equivalents. We intended to validate Duke Activity Status Index in our population for the assessment of preoperative myocardial perfusion imaging appropriateness. A total of 542 patients referred for myocardial perfusion imaging were recruited. A questionary compiled from Duke Activity Status Index was filled out based on which metabolic equivalents were calculated. Demographic data and history of cardiac risk factors were also collected. Myocardial perfusion imaging was performed using a 2-day stress-rest protocol either by exercise tolerance test or by pharmacologic stress through injection of Tc-MIBI and imaging by a dual-head gamma camera. Out of 542 patients, 369 (68.1%) were evaluated for preoperative risk assessment. Metabolic equivalents (oxygen consumption/min/kg) were calculated at 9.3 ± 5.1, 10.8 ± 4.8, and 8.7 ± 5.1 in total, preoperative patients and patients evaluated for ischemia due to nonsurgical purposes, respectively (p = 0.001). The myocardial perfusion imaging was rarely appropriate in 291 (79.5%), maybe appropriate in 67 (18.3%), and appropriate in 8 (2.2%) patients. The prevalence of abnormal myocardial perfusion imaging was 22.5%, 28.4%, and 12.5% in "rarely appropriate," "maybe appropriate," and "appropriate" scenarios, respectively. Metabolic equivalents were similar between patients with normal and abnormal myocardial perfusion imaging (8.7 ± 5.0 vs. 8.5 ± 5.4). Either Duke Activity Status Index is not a proper tool for calculation of metabolic equivalents or the appropriate use criteria is not operational in the population of Iranian preoperative patients in which cultural factors may contribute.

Assessment of Semi-automated Computed Tomographic Measures of Segmental Perfusion Defects in a Swine Model (Sus scrofa) of Intermediate Coronary Lesions.

Computed tomographic myocardial perfusion (CTP) imaging is a tool that shows promise in emergent settings for defining the hemodynamic significance of coronary artery disease. In this study, we examined the accuracy with which the transmural perfusion ratio (TPR) derived through semiautomated CTP analysis reflected segmental perfusion defects associated with intermediate coronary artery lesions in swine. Lesions (diameter stenosis, 65% ± 11%) of the left anterior descending coronary artery (LAD) were created in 10 anesthetized female swine (weight, 47.5 ± 1.9 kg) by using a pneumatic occlusion device implanted on the LAD. Occluder inflation pressures were adjusted to maintain fractional flow reserve (FFR, 74.3 ± 1.7) during adenosine infusion (140ug/kg/min). Static CTP imaging using a stress-rest protocol and segmental TPR derived from semiautomated CT perfusion software was compared with microsphere-derived TPR (mTPR) by using a 16-segment model and polar mapping. Intermediate LAD stenosis was verified through multiplanar coronary CT angiography. Receiver operating characteristic analysis identified an optimal threshold for segmental perfusion defects for intermediate lesions (TPR threshold, ≤0.80); however, the area under the receiver operating characteristic curve was 0.58, and the overall accuracy was 63%. At this threshold, the sensitivity and specificity were 65% and 61%, and the positive and negative predictive values were 61% and 65%, respectively. Although CTP-TPR illustrated segmental perfusion defects with intermediate lesions, the disparity between CTP-TPR and mTPR measures of segmental perfusion suggests that further advances in analysis software may be necessary to improve the localization of segmental defects for intermediated lesions.

Lower limb perfusion scintigraphy with 99mTc-MIBI scintigraphy and determination of endothelin in diabetic and nondiabetic patients

Background/Aim. Peripheral artery disease (PAD) is a common macrovascular complication in patients with diabetes mellitus (DM) as a result of impairment of homeostatic mechanisms of the endothelium, thus initiating the process of atherosclerosis. The imbalance between endothelium- derived vasodilators and vasoconstrictors plays an important role in the pathogenesis of diabetic microangiopathy, as well as in other vascular complications in diabetes. Perfusion scintigraphy using technetium-99m-methoxyisobutyl isonitrile (99mTc-MIBI) can be very useful method for evaluation of the lower limbs muscle perfusion. The aim of this study was: to compare the results of dynamic and static studies of lower limbs tissue muscle perfusion scintigraphy with 99mTc-MIBI (one-day rest-stress protocol) in patients with and without DM and to determine the perfusion reserve for diagnostic evaluation of PAD in patients with DM type 2, as well as to assess the endothelin-1 (ET-1) levels as a vasoconstrictor agent in patients with and without diabetes. Methods. Prospective study was performed in 90 patients, divided into two groups according to the presence of DM ? patients with DM type 2 (DP), 60/90 (67%), and patients without DM (NDP), 30/90 (33%). Lower limbs tissue muscle perfusion scintigraphy was done with 99mTc-MIBI including two studies (?rest? and ?stress?). Results. In the DP group significantly lower pick of radioactivity was detected in comparison with the NDP group, in both phases (rest and stress), for both calves. Lower counts from the static phase were registered in the region of both calves. Lower inter-extremity indexes as well as perfusion reserve were found in the DP group. There was a significant difference in concentrations of ET-1 between groups (higher concentrations were found in tzhe DP group). Conclusion. This one-day protocol (rest-stress with 99mTc-MIBI) of perfusion scintigraphy of lower limbs is considered a useful procedure in PAD assessment in patients with DM type 2, especially the asymptomatic form.

P3355Stress-induced left ventricular dyssynchrony predicts future cardiac events in patients with known or suspected coronary artery disease

Abstract Background Prognostic value of stress induced left ventricular (LV) dyssynchrony has not been fully understood. The aim of this study was to evaluate the possible impact between cardiovascular events and stress induced worsening LV dyssynchrony. Methods and results One hundred and eighty consecutive subjects with known or suspected coronary artery disease (CAD) (142 men, mean age 68±12 years) underwent both gated myocardial single photon emission computed tomography (SPECT) with 99mTc-sestamibi or tetrofosmin according to a standard same day stress-rest protocol and coronary angiography or coronary computed tomography. The summed difference score (SDS) was calculated in every subjects. LV ejection fraction (EF) and phase Entropy at after stress and rest were determined by cardioREPO software. We determined %ΔEntropy = (stress Entropy - rest Entropy)/rest Entropy x100, as an indicator of stress-induced LV dyssynchrony. In the study population, the mean SDS was 2.7±3.9 and LVEF was 58±16%, stress and rest Entropy were 0.62±0.15 and 0.57±0.13, respectively. %ΔEntropy was higher in patients with CAD than in those without CAD (3.3±11.5 vs. 10.2±15.0, respectively). Moreover, there was a strict correlation between the presence of CAD and %ΔEntropy, indicator of stress induced LV dyssynchrony (non-CAD vs. CAD and/or 1 vessel disease vs. multivessel disease: 4.3±12.5 vs. 8.8±15.6 vs. 12.7±14.3, respectively. p&lt;0.05) We examined all study subjects and they were divided into 2 groups by cut off value of the %ΔEntropy constructed with receiver operating characteristic curve (=15.4). Kaplan-Meier analysis revealed that future cardiovascular event rate was significantly higher in %ΔEntropy &gt;15.4 group (20/57) than in %ΔEntropy &lt;15.4 group (24/123) (Log-rank p&lt;0.01). On the other hand, summed stress score and SDS were no significant differences between 2 groups. However, SDS was higher in patients with future cardiovascular event than in those without cardiovascular event (4.4±5.4 vs. 2.2±3.2, respectively. p=0.001). Conclusion In patients with known or suspected CAD, stress-induced worsening LV dyssynchrony may predict the presence of CAD and future cardiac events. Acknowledgement/Funding None

How variable are the volumetric measurements from gated perfusion SPECT when a one-day stress-rest protocol is used?

BackgroundUsing myocardial perfusion scintigraphy (MPS), an increase in left ventricular (LV) volumes or a decrease in ejection fraction (EF) from rest to stress may be clinically important. The variation in these measures between the low-dose stress acquisition and high-dose rest acquisition in a one-day stress-rest protocol has not been established. We assessed the reproducibility of gated volumetric indices between stress and rest and the normal variation in ungated TID ratio for a one-day stress-rest 99mTc-tetrofosmin protocol. MethodsTwo thousand and one hundred and fifty eight (2158) 99mTc-tetrofosmin MPS patient studies were analyzed retrospectively. Studies were excluded for incomplete data, significant technical difficulties, or (for gated analysis but not for analysis of TID ratio) if the LV EF was > 75%. An analysis of gated data was undertaken to establish the reproducibility of ventricular volumes and EF between stress and rest scans. Ungated volume data were analyzed to determine the confidence limits of TID ratio according to ventricular volume. ResultsGated data were analyzed for 621 patients without inducible hypoperfusion. Mean EF at rest was slightly higher than after stress (62.4% ± 10.3% vs 61.2% ± 10.4%, P < 0.001), and the standard deviation of the difference was 5.2% (95% CI 4.9% to 5.5%). Ungated volumes were available for 992 non-ischaemic patients. The upper 95% CI for TID ratio was 1.23. This increased from 1.20 to 1.37 between the highest and lowest deciles of rest ungated volume. ConclusionUsing a one-day stress-rest 99mTc-tetrofosmin protocol, a fall in LV EF between rest and stress of > 11.6% or a TID ratio of > 1.23 is likely to be clinically reliable. The upper limit of normal for TID ratio needs to be increased for patients with small LV chamber volumes.

Evaluation of Patients’ effective dose in nuclear medicine department of Isfahan in order to define a local reference level

Introduction: Nowadays, nuclear medicine (NM) imaging indications in medical practice is raising. A practical step to get closer to the optimization rule is collecting data about patients’ exposure and definition of guidance levels. The aim of this study was definition of local reference level in Isfahan city. Materials and Methods: Questionnaires were given to two NM departments of Isfahan Hospitals. The data of age, gender, weight, type and activity of used radiopharmaceutical were collected for protocols of Bone (TC-MDP), Kidney (TC-DMSA), Kidney (TC-DTPA), Kidney (TC-EC), Thyroid (TC- Pertechnetate), Lung (TC-MAA), Cardiac (TC-MIBI) for adults and Bone (TC-MDP), Kidney (TC-DMSA), Kidney (TC-EC), Kidney (TC-DTPA) for pediatrics. The cardiac scan is performed in two-day Stress-Rest protocol. Results: 1540 patients (243 pediatric and 1297 adults) were included. The average injected activities in pediatrics were 5, 3, 2 and 5 mili-curies for MDP, DMSA, EC and DTPA respectively. These injected activities impose doses of 1.82, 1.91, 1.68, 2.32 mili siverts for pediatric patients. For adult patients the average activities were 22.5, 6.5, 8, 4, 12, 4, 21.5 and 19.5 mili-curies for protocols of MDP, DMSA, EC, MAA, DTPA, Pertechnetate, MIBI-Stress and MIBI-Rest respectively. Which impose effective total body doses of 4.75, 2.12, 2.07, 1.62, 2.17, 1.92, 6.29 and 6.49 mili siverts to adult patients respectively. Conclusion: It is the first study done in all ages to evaluate patients’ dose in NM in Iran. In these departments injected activities were based on patient weight and protocols were adapted with dose charts exists for adult and pediatric patients; so variations in doses were minimum. These charts were offered to radiation workers based on acceptable image quality, SPECT system sensitivity and patient dose. In comparison with guidance levels of other countries, patients’ received dose during in these Isfahan N.M centers were comparable with international diagnostic reference levels reported by the European commission and mettle et al 2008 and study of Niksirat et al, 2014 in Mazandaran. Injected activities for cardiac imaging are higher (40%) from study of Salimi et al 2015 in Tehran. This variations through the administrated dose in country makes it more critical to plan a national survey in order to offer a guideline in this country.

Comparative Performances of Dipyridamole and Regadenoson to Detect Myocardial Ischemia using Cardiac Cadmium-Zinc-Telluride Single-Photon Emission Computerized Tomography.

Objective:We evaluated the relative performances of dipyridamole (Dip) and regadenoson (Reg) in a cohort of patients referred for coronary artery disease diagnosis or follow-up using myocardial perfusion imaging.Materials and Methods:We retrospectively included 515 consecutive patients referred for 99mTc-sestamibi myocardial perfusion single-photon emission computerized tomography (SPECT) on a cadmium-zinc-telluride (CZT) camera after pharmacologic stress. About three quarters (n = 391, 76%) received Dip. Reg was administrated to patients with chronical respiratory disease or with body mass index (BMI) over 38 kg/m2 (n = 124, 24%). Patients with an abnormal stress scan (92%) underwent a rest imaging on the same day. Qualitative interpretation of perfusion images was achieved using QPS software, and the ischemic area was assessed using the 17-segment model. In patients undergoing a stress-rest protocol, perfusion polar plots were postprocessed using automated in-house software to quantify the extension, intensity, and location of the reversible perfusion defect. Statistical comparison between groups was performed using univariate and multivariate analysis.Results:Qualitative analysis concluded to myocardial ischemia in 70% of the patients (69% in the Dip group, 76% in the Reg group, P = ns). In those patients, the number of involved segments (Dip 2.5 ± 1.6, Reg 2.7 ± 1.6, P = ns) and the proportion of patients with an ischemic area larger than two segments (Dip 30%, Reg 37%, P = ns) were comparable. Automated quantification of the reversible perfusion defect demonstrated similar defect extension, intensity, and severity in the two groups. Defect location was identical at the myocardial segment and vascular territory scales.Conclusions:Reg and Dip showed equal performances for ischemic burden characterization using myocardial CZT SPECT.

Accuracy of cadmium-zinc-telluride imaging in detecting single and multivessel coronary artery disease: Is there any gender difference?

PurposeTo evaluate gender-related differences in diagnostic accuracy of cadmium‑zinc-telluride (CZT) myocardial perfusion imaging in detecting single- and multi-vessel coronary artery disease (CAD). MethodsWe prospectively enrolled 1161 consecutive patients with known or suspected coronary artery disease (288, 25% women and 873, 75% men) who had been referred to our laboratory for stress–rest myocardial perfusion imaging (single-day stress–rest protocol, mean radiation dose: 4 mSv). All patients underwent coronary angiography within 30 days; significant CAD was defined in the presence of a coronary stenosis >70%. Summed stress scores (SSS), summed rest scores (SRS) and summed difference scores (SDS) were obtained. Image quality was graded “good” or better in >90% of patients. ResultsOn coronary angiography, left main trunk, left anterior descending artery, left circumflex artery and right coronary artery obstructive stenosis were seen in 13, 486, 393 and 499 patients, respectively. Global SSS was the best predictor of CAD in women (AUC = 0.866, 81% sensitivity and 79% specificity) and in men (AUC = 0.871, 76% sensitivity and 84% specificity). Interestingly, its accuracy was maintained also in patients with two-vessel (women: AUC = 0.842, p < 0.001; men: AUC 0.839, p < 0.001) or three-vessel disease (women: AUC = 0.800, p < 0.001; men: AUC 0.804, p < 0.001). There was no gender-related difference in terms of diagnostic accuracy. ConclusionsEvaluation of multivessel disease can be obtained by CZT camera in men as well as in women, with high accuracy at a lower radiation exposure.