Diagnosis of coronary artery disease by radionuclide myocardial perfusion imaging

Combined Supine-Prone Myocardial Perfusion Imaging: Enhancing Diagnostic Accuracy

The combined supine-prone imaging protocol for SPECT myocardial perfusion imaging offers significant advantages over supine imaging alone. By comparing supine and prone images, one can distinguish attenuation artifacts in the inferior and anterior walls from true perfusion defects, thus improving specificity and diagnostic accuracy. The recommended protocol is to perform prone imaging after supine stress imaging when perfusion defects are noted. The additional prone imaging time is 20%-40% less than the standard supine imaging time. Implementing prone imaging can optimize patient care and provide substantial benefits for nuclear cardiology labs, especially those without attenuation correction.

Effects of Ivabradine on Myocardial Perfusion in Chronic Angina: A Prospective, Preliminary, Open-Label, Single-Arm Study

INTRODUCTION

Ivabradine reduces heart rate (HR), episodes of angina, and nitrate consumption, and increases exercise capacity in patients with chronic angina (CA). In this exploratory study, myocardial perfusion scintigraphy (MPS) was used to evaluate changes in the percentage of myocardial ischemia after ivabradine therapy in patients with CA.

METHODS

This prospective, open-label, single-arm study included patients with CA receiving maximum tolerated doses of beta blockers, who had a resting HR ≥ 70 bpm and had experienced ischemia according to MPS during an exercise test at baseline. Participants received ivabradine 5 mg twice daily (titrated according to HR) concomitant with beta blockers. A second MPS was performed after 3 months, without interruption of treatment with beta blockers or ivabradine. The primary outcome was change in the percentage of myocardial ischemia from baseline to 3 months. Time to ischemia during the exercise test, the proportion of patients presenting angina during the exercise test, and health status, assessed using the seven-item Seattle Angina Questionnaire-7 (SAQ-7), were also evaluated.

RESULTS

Twenty patients (3 females) with a mean (± standard deviation [SD]) age of 62.2 ± 6.5 years were included in the study, of whom 55% had diabetes, 70% had previous myocardial revascularization, and 45% had previous myocardial infarction. The percentage of patients with myocardial ischemia significantly decreased from baseline to 3 months after initiation of treatment with ivabradine (- 2.9%; 95% confidence interval [CI] - 0.3 to - 5.5; p = 0.031). Mean time to appearance of ischemia increased from 403 ± 176 s at baseline to 466 ± 136 s at 3 months after initiation of ivabradine (Δ62 s; 95% CI 18-106 s; p = 0.008), and the proportion of patients experiencing angina during the exercise test decreased from 40% at baseline to 5% also at 3 months (p = 0.016). Mean resting HR decreased from 76 ± 7 bpm at baseline to 55 ± 8 bpm at 3 months (p < 0.001). The mean SAQ-7 summary score improved from 69 ± 21 at baseline to 83 ± 12 at 3 months (p = 0.001). No serious adverse effects were reported.

CONCLUSION

Ivabradine added to beta blockers was associated with a reduction in detectable myocardial ischemia by MPS in patients with CA. Infographic available for this article.

TRIAL REGISTRATION

The trial has been retrospectively registered with the Brazilian Registry of Clinical Trials (REBEC) under the following number RBR-5fysqrh (date of registration: 30 November 2023).

The Application of Conditional Probability to Harmonize Nuclear Cardiology Test Results

Both exercise single photon emission computed tomography (SPECT) imaging and myocardial perfusion imaging with positron emission tomography produce multiple outcome variables. These include the stress electrocardiogram (ECG), visual perfusion assessment and quantitative myocardial blood flow. Bayes' analysis using conditional probability allows the distillation of multiple test results into a single probability of disease for individual patients. This paper examines the application of conditional probability analysis to two noninvasive modalities that generate multiple outcome results: exercise ECG combined with SPECT imaging and vasodilator RB-82 positron emission tomography perfusion imaging combined with quantitative measure of absolute myocardial blood flow. In this manner, a single probability of disease incorporating all the available data is generated for an individual patient.

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.

Establishment and validation of an AI-aid method in the diagnosis of myocardial perfusion imaging

BACKGROUND

This study aimed to develop and validate an AI (artificial intelligence)-aid method in myocardial perfusion imaging (MPI) to differentiate ischemia in coronary artery disease.

METHODS

We retrospectively selected 599 patients who had received gated-MPI protocol. Images were acquired using hybrid SPECT-CT systems. A training set was used to train and develop the neural network and a validation set was used to test the predictive ability of the neural network. We used a learning technique named "YOLO" to carry out the training process. We compared the predictive accuracy of AI with that of physician interpreters (beginner, inexperienced, and experienced interpreters).

RESULTS

Training performance showed that the accuracy ranged from 66.20% to 94.64%, the recall rate ranged from 76.96% to 98.76%, and the average precision ranged from 80.17% to 98.15%. In the ROC analysis of the validation set, the sensitivity range was 88.9 ~ 93.8%, the specificity range was 93.0 ~ 97.6%, and the AUC range was 94.1 ~ 96.1%. In the comparison between AI and different interpreters, AI outperformed the other interpreters (most P-value < 0.05).

CONCLUSION

The AI system of our study showed excellent predictive accuracy in the diagnosis of MPI protocols, and therefore might be potentially helpful to aid radiologists in clinical practice and develop more sophisticated models.

Patient Selection and Clinical Indication for Chronic Total Occlusion Revascularization-A Workflow Focusing on Non-Invasive Cardiac Imaging

Percutaneous coronary intervention of chronic total occlusion (CTO PCI) is a challenging procedure with high complication rates and, as not yet fully understood long-term clinical benefits. Ischemic symptom relief in patients with high ischemic burden is to date the only established clinical indication to undergo CTO PCI, supported by randomized controlled trials. In this context, current guidelines suggest attempting CTO PCI only in non-invasively assessed viable CTO correspondent myocardial territories, with large ischemic areas. Hence, besides a comprehensive coronary angiography lesion evaluation, the information derived from non-invasive cardiac imaging techniques is crucial to selecting candidates who may benefit from the revascularization of the occluded vessel. Currently, there are no clear recommendations for a non-invasive myocardial evaluation or choice of imaging modality pre-CTO PCI. Therefore, selecting among available options is left to the physician's discretion. As CTO PCI is strongly recommended to be carried out explicitly in experienced centers, full access to non-invasive imaging for risk-benefit assessment as well as a systematic institutional evaluation process has to be encouraged. In this framework, we opted to review the current myocardial imaging tools and their use for indicating a CTO PCI. Furthermore, based on our experience, we propose a cost-effective systematic approach for myocardial assessment to help guide clinical decision-making for patients presenting with chronic total occlusions.

Predictive value of incidental right ventricular abnormalities identified on SPECT for mortality and pulmonary hypertension

BACKGROUND

The clinical significance of incidentally found RV abnormalities on low-risk SPECT studies is not well-defined. The objective of this study was to determine the predictive value of incidental right ventricular (RV) abnormalities identified on single photon emission computed tomography (SPECT) scans for mortality and pulmonary hypertension (PH).

METHODS

We retrospectively analyzed all low-risk SPECT studies in patients without known coronary artery or pulmonary vascular disease, performed at our institution, from 2007-2020. Adjusted Cox proportional hazards models were used to evaluate the association between incidental RV abnormalities on low-risk SPECT studies and outcomes.

RESULTS

Of the 4761 patients included in the analysis, mortality events were present in 494, and echocardiographic PH was present in 619. Incidental RV abnormalities on low-risk SPECT studies were significantly and independently associated with all-cause mortality (HR = 1.41, CI [1.07-1.86], P = 0.0152) and echocardiographic PH (HR = 2.06, CI [1.64-2.60], P < 0.0001).

CONCLUSIONS

These data suggest incidental RV abnormalities found on low-risk SPECT imaging studies are significantly and independently associated with increased mortality and risk of developing echocardiographic PH, and could identify high-risk patients for closer monitoring and additional diagnostic testing.

Diagnostic Accuracy of Coronary Computed Tomography Before Aortic Valve Replacement: Systematic Review and Meta-Analysis

PURPOSE

In aortic stenosis patients referred for surgical and transcatheter aortic valve replacement (AVR), the evidence of diagnostic accuracy of coronary computed tomography angiography (CCTA) has been limited. The objective of this study was to investigate the diagnostic accuracy of CCTA for significant coronary artery disease (CAD) in patients referred for AVR using invasive coronary angiography (ICA) as the gold standard.

MATERIALS AND METHODS

We searched databases for all diagnostic studies of CCTA in patients referred for AVR, which reported diagnostic testing characteristics on patient-based analysis required to pool summary sensitivity, specificity, positive-likelihood ratio, and negative-likelihood ratio. Significant CAD in both CCTA and ICA was defined by >50% stenosis in any coronary artery, coronary stent, or bypass graft.

RESULTS

Thirteen studies evaluated 1498 patients (mean age, 74 y; 47% men; 76% transcatheter AVR). The pooled prevalence of significant stenosis determined by ICA was 43%. Hierarchical summary receiver-operating characteristic analysis demonstrated a summary area under curve of 0.96. The pooled sensitivity, specificity, and positive-likelihood and negative-likelihood ratios of CCTA in identifying significant stenosis determined by ICA were 95%, 79%, 4.48, and 0.06, respectively. In subgroup analysis, the diagnostic profiles of CCTA were comparable between surgical and transcatheter AVR.

CONCLUSIONS

Despite the higher prevalence of significant CAD in patients with aortic stenosis than with other valvular heart diseases, our meta-analysis has shown that CCTA has a suitable diagnostic accuracy profile as a gatekeeper test for ICA. Our study illustrates a need for further study of the potential role of CCTA in preoperative planning for AVR.

Coronary artery disease detection - limitations of stress testing in left ventricular dysfunction

Incidental diagnosis of left ventricular systolic dysfunction (LVD) is common in clinical practice. The prevalence of asymptomatic LVD (Ejection Fraction, EF < 50%) is 6.0% in men and 0.8% in women and is twice as common as symptomatic LVD. The timely and definitive exclusion of an ischemic etiology is central to optimizing care and reducing mortality in LVD. Advances in cardiovascular imaging provide many options for imaging of patients with left ventricular dysfunction. Clinician experience, patient endurance, imaging modality characteristics, cost and safety determine the choice of testing. In this review, we have compared the diagnostic utility of established tests - nuclear and echocardiographic stress testing with newer techniques like coronary computerized tomography and cardiac magnetic resonance imaging and highlight their inherent limitations in patients with underlying left ventricular dysfunction.

Comparative Study between Perfusion Changes and Positive Findings on Coronary Flow Reserve

BACKGROUND

Functional assessment of coronary artery obstruction is used in cardiology practice to correlate anatomic obstructions with flow decrease. Among such assessments, the study of the coronary fractional flow reserve (FFR) has become the most widely used.

OBJECTIVE

To evaluate the correlation between FFR and findings of ischemia obtained by noninvasive methods including stress echocardiography and nuclear medicine and the presence of critical coronary artery obstruction.

METHODS

Retrospective study of cases treated with systematized and standardized procedures for coronary disease between March 2011 and August 2014. We included 96 patients with 107 critical coronary obstructions (> 50% in the coronary trunk and/or ≥ 70% in other segments) estimated by quantitative coronary angiography (QCA) and intracoronary ultrasound (ICUS). All cases presented ischemia in one of the noninvasive studies.

RESULTS

All 96 patients presented ischemia (100%) in one of the functional tests. On FFR study with adenosine 140 g/kg/min, 52% of the cases had values ≤ 0.80. On correlation analysis for FFR ≤ 0.80, the evaluation of sensitivity, specificity, positive and negative predictive values, accuracy, and ROC curve in relation to the stenosis degree and length, and presence of ischemia, no significant values or strong correlation were observed.

CONCLUSION

Coronary FFR using a cut-off value of 0.80 showed no correlation with noninvasive ischemia tests in patients with severe coronary artery obstructions on QCA and ICUS.

Outcomes after inappropriate nuclear myocardial perfusion imaging: A meta-analysis

BACKGROUND

The relationship between inappropriate MPI and cardiovascular outcomes is poorly understood. We sought to systematically review the literature on appropriate use criteria (AUC) for MPI, including temporal trend of inappropriate testing and resulting cardiovascular outcomes.

METHODS

We searched the MEDLINE database for studies related to AUC and MPI. The co-primary outcomes were abnormal test results and the presence of cardiac ischemia. Random effects odds ratios (OR) were constructed using DerSimonian-Laird method.

RESULTS

A total of 22 studies with 23,443 patients were included. The prevalence of inappropriate testing was 14.8% [95% confidence interval (CI) 11.6%-18.7%]. Inappropriate MPI studies were less likely to be abnormal (OR 0.41 95% CI 0.35-0.49, P < .0001) and to demonstrate ischemia (OR 0.40, 95% CI 0.24-0.67, P < .0001) compared to appropriate testing. No difference in the rate of inappropriate tests was detected based on the midpoint of the enrollment year (P = .54). The pattern of ordering inappropriate studies was not different between cardiology and non-cardiology providers (OR 0.74, 95% CI 0.51-1.06, P = .10).

CONCLUSION

Inappropriate MPI studies are less likely to yield abnormal results or demonstrate myocardial ischemia. The rate of inappropriate MPI has not decreased over time.

The Prevalence of Clinically Significant Ischemia in Patients Undergoing Percutaneous Coronary Intervention: A Report from the Multicenter Registry

Background

Myocardial perfusion scintigraphy (MPS) plays an important role in the evaluation and quantification of myocardial ischemia, and those with significant ischemia (SI) benefit most from revascularization procedures. This study aimed to identify the clinical factors and anatomical features associated with SI in patients with stable ischemic heart disease (SIHD).

Methods and Results

Data were analyzed from 4197 SIHD patients undergoing percutaneous coronary intervention (PCI). Ischemia was based on MPS findings prior to PCI, with SI defined as an ischemic region of more than 10% of the total left ventricular area. Logistic regression analysis was performed to identify any clinical factors associated with SI. MPS was used to evaluate 1070 (25.5%) patients pre-procedurally. Patients with a history of heart failure, stroke, or anginal symptoms with Canadian Cardiovascular Society class 2 or more were more likely to have SI (odds ratio [OR] 1.63, p = 0.025, OR: 1.85, p = 0.009, and OR: 1.49, p = 0.003, respectively). When angiographic variables were considered, a proximal left anterior descending artery (pLAD) lesion was the sole factor associated with SI (OR: 1.45, p = 0.012). Importantly, those with SI had more in-hospital complications (p = 0.006), most notably post-PCI infarcts (p = 0.008).

Conclusions

Patients’ background data, such as stronger anginal symptoms or a pLAD lesion, were associated with SI. Patients with SI must be treated with PCI to improve their long-term prognosis; however, procedure-related complications happen more frequently in SI patients than in non-SI patients. Physicians must give their full attention when performing the PCI procedure in SI patients to minimize their complication rate.

Non-invasive nuclear myocardial perfusion imaging improves the diagnostic yield of invasive coronary angiography

AIMS

Several studies reported on the moderate diagnostic yield of elective invasive coronary angiography (ICA) regarding the presence of coronary artery disease (CAD), but limited data are available on how prior testing for ischaemia may contribute to improve the diagnostic yield in an every-day clinical setting. This study aimed to assess the value and use of cardiac myocardial perfusion single photon emission computed tomography (MPS) in patient selection prior to elective ICA.

METHODS AND RESULTS

The rate of MPS within 90 days prior to elective ICA was assessed and the non-invasive test results were correlated with the presence of obstructive CAD on ICA (defined as stenosis of ≥50% of a major epicardial coronary vessel). Multivariate logistic regression analysis was performed to identify predictors of obstructive CAD. A total of 7530 consecutive patients were included. At catheterization, 3819 (50.7%) were diagnosed as having obstructive CAD. Patients with a positive result on MPS (performed in 23.5% of patients) were significantly more likely to have obstructive CAD as assessed by ICA than those who did not undergo non-invasive testing (74.4 vs. 45.6%, P < 0.001). Furthermore, a pathological MPS result was a strong, independent predictor for CAD findings among traditional risk factors and symptoms.

CONCLUSION

In an every-day clinical setting, the use of MPS substantially increases the diagnostic yield of elective ICA and provides incremental value over clinical risk factors and symptoms in predicting obstructive CAD, thus emphasizing its importance in the decision-making process leading to the use of diagnostic catheterization.

Detection and severity classification of extracardiac interference in ⁸²Rb PET myocardial perfusion imaging

PURPOSE

Myocardial perfusion imaging (MPI) is used for diagnosis and prognosis of coronary artery disease. When MPI studies are performed with positron emission tomography (PET) and the radioactive tracer rubidium-82 chloride ((82)Rb), a small but non-negligible fraction of studies (∼10%) suffer from extracardiac interference: high levels of tracer uptake in structures adjacent to the heart which mask the true cardiac tracer uptake. At present, there are no clinically available options for automated detection or correction of this problem. This work presents an algorithm that detects and classifies the severity of extracardiac interference in (82)Rb PET MPI images and reports the accuracy and failure rate of the method.

METHODS

A set of 200 (82)Rb PET MPI images were reviewed by a trained nuclear cardiologist and interference severity reported on a four-class scale, from absent to severe. An automated algorithm was developed that compares uptake at the external border of the myocardium to three thresholds, separating the four interference severity classes. A minimum area of interference was required, and the search region was limited to that facing the stomach wall and spleen. Maximizing concordance (Cohen's Kappa) and minimizing failure rate for the set of 200 clinician-read images were used to find the optimal population-based constants defining search limit and minimum area parameters and the thresholds for the algorithm. Tenfold stratified cross-validation was used to find optimal thresholds and report accuracy measures (sensitivity, specificity, and Kappa).

RESULTS

The algorithm was capable of detecting interference with a mean [95% confidence interval] sensitivity/specificity/Kappa of 0.97 [0.94, 1.00]/0.82 [0.66, 0.98]/0.79 [0.65, 0.92], and a failure rate of 1.0% ± 0.2%. The four-class overall Kappa was 0.72 [0.64, 0.81]. Separation of mild versus moderate-or-greater interference was performed with good accuracy (sensitivity/specificity/Kappa = 0.92 [0.86, 0.99]/0.86 [0.71, 1.00]/0.78 [0.64, 0.92]), while separation of moderate versus severe interference severity classes showed reduced sensitivity/Kappa but little change in specificity (sensitivity/specificity/Kappa = 0.83 [0.77, 0.88]/0.82 [0.77, 0.88]/0.65 [0.60, 0.70]). Specificity was greater than sensitivity for all interference classes. Algorithm execution time was <1 min.

CONCLUSIONS

The algorithm produced here has a low failure rate and high accuracy for detection of extracardiac interference in (82)Rb PET MPI scans. It provides a fast, reliable, automated method for assessing severity of extracardiac interference.

Low hip bone mineral density predicts mortality in maintenance hemodialysis patients: a five-year follow-up study

BACKGROUND

Bone loss is common among hemodialysis patients and contributes to mortality. The association between bone loss and vascular calcification may explain the increased mortality risk. Studies on the association between decreased bone mass and mortality in maintenance hemodialysis patients are limited.

METHODS

Eighty-three hemodialysis patients underwent bone mineral density (BMD) and coronary artery calcification (CAC) measurements. The relationship between BMD and mortality was analyzed after a 5-year follow-up period.

RESULTS

Eighty percent of the patients had reduced hip BMD. In univariate Cox regression analyses, age, cardiovascular disease, dyslipidemia, increased CAC score, increased comorbidity score and decreased hip BMD were associated with mortality. Low hip BMD remained independently associated with mortality after adjustments for cardiovascular risk factors, comorbidity score and CAC score. Patients with BMD in the lowest tertile had the worst survival.

CONCLUSION

Low hip BMD predicted mortality in maintenance hemodialysis patients independent of CAC.

Discrepancy between stress electrocardiographic changes and nuclear myocardial perfusion defects in the prognostic assessment of patients with chest pain

OBJECTIVES

The aim of the present study was to determine the long-term prognostic value provided by the exercise electrocardiographic (ECG) response to nuclear myocardial perfusion imaging (MPI) in the evaluation of patients with chest pain, focusing on patients with a discrepancy between the two tests.

METHODS

A total of 1460 consecutive patients (777 female; 62.6 ± 11.4 years) undergoing exercise myocardial single-photon emission computed tomography (SPECT) were included. The endpoint was the occurrence of acute coronary syndrome, heart failure or cardiac death during follow-up.

RESULTS

Ischemic ECG changes were observed during stress testing in 271 patients (18.5%) and 362 patients (24.7%) had positive (abnormal) exercise MPI results. There was a discrepancy between ECG and SPECT findings in 471 patients (32.2%). During the follow-up period (14.0-39.6 months), 224 patients (15.3%) presented cardiac events. The hazard ratios (HR) of ECG and MPI results to predict events were 1.506 (95% CI: 1.113-2.039) and 10.481 (95% CI: 7.799-14.080), respectively. In patients with negative MPI, the ECG response did not predict events (HR 1.214 [95% CI: 0.646-2.282]), the same as in patients with positive MPI (HR 1.203 [95% CI: 0.848-1.705]). Only in hypertensive patients with positive SPECT did the ECG show significant prognostic value (HR 1.937 [95% CI: 1.030-3.642]). In multivariate analysis, positive MPI proved an independent long-term prognostic factor (HR 10.536 [95% CI: 7.759-14.308]), but not ECG (HR 1.356 [95% CI: 0.994-1.850]).

CONCLUSION

MPI results (normal vs. abnormal) had strong predictive value and discrepant ECG results had no significant additive prognostic value.

Prevalence, extent, and independent predictors of silent myocardial infarction

BACKGROUND

The phenomenon of silent myocardial infarction is poorly understood.

METHODS

We aimed to evaluate the prevalence, extent, and independent predictors of silent myocardial infarction in 2 large independent cohorts of consecutive patients without a history of myocardial infarction referred for rest/stress myocardial perfusion single photon emission computed tomography. There were 1621 patients enrolled in the derivation cohort and 338 patients in the validation cohort. Silent myocardial infarction was diagnosed in patients with a myocardial scar ≥5% of the left ventricle.

RESULTS

In the derivation cohort, the prevalence of silent myocardial infarction was 23.3% (n = 377). The median infarct size was 10% (interquartile range [IQR] 5%-15%) of the left ventricle. The prevalence of silent myocardial infarction was 28.5% in diabetics and 21.5% in nondiabetics (P = .004). Diabetes mellitus was an independent predictor for the presence of silent myocardial infarction (odds ratio 1.5; 95% confidence interval, 1.1-1.9; P = .004). These findings were confirmed in the independent validation cohort. In the validation cohort, the prevalence of silent myocardial infarction was 26.3% (n = 89), while the prevalence was higher in diabetics (35.8%) than in nondiabetics (24%; P = .049). The median infarct size was 11.8% (IQR 5.9%-17.6%) of the left ventricle. Again, in logistic regression analysis, diabetes mellitus was a significant predictor of the presence of silent myocardial infarction.

CONCLUSION

Silent myocardial infarctions are more common than previously thought. One of 4 patients with suspected coronary artery disease had experienced a silent myocardial infarction; the extent in average is 10% of the left ventricle, and it is more common in diabetics.

Initial multicentre experience of high-speed myocardial perfusion imaging: comparison between high-speed and conventional single-photon emission computed tomography with angiographic validation

PURPOSE

High-speed (HS) single-photon emission computed tomography (SPECT) with a recently developed solid-state camera shows comparable myocardial perfusion abnormalities to those seen in conventional SPECT. We aimed to compare HS and conventional SPECT images from multiple centres with coronary angiographic findings.

METHODS

The study included 50 patients who had sequential conventional SPECT and HS SPECT myocardial perfusion studies and coronary angiography within 3 months. Stress and rest perfusion images were visually analysed and scored semiquantitatively using a 17-segment model by two experienced blinded readers. Global and coronary territorial summed stress scores (SSS) and summed rest scores (SRS) were calculated. Global SSS ≥3 or coronary territorial SSS ≥2 was considered abnormal. In addition the total perfusion deficit (TPD) was automatically derived. TPD >5% and coronary territorial TPD ≥3% were defined as abnormal. Coronary angiograms were analysed for site and severity of coronary stenosis; ≥50% was considered significant.

RESULTS

Of the 50 patients, 13 (26%) had no stenosis, 22 (44%) had single-vessel disease, 6 (12%) had double-vessel disease and 9 (18%) had triple-vessel disease. There was a good linear correlation between the visual global SSS and SRS (Spearman's ρ 0.897 and 0.866, respectively; p < 0.001). In relation to coronary angiography, the sensitivities, specificities and accuracies of HS SPECT and conventional SPECT by visual assessment were 92% (35/38), 83% (10/12) and 90% (45/50) vs. 84% (32/38), 50% (6/12) and 76% (38/50), respectively (p < 0.001). The sensitivities, specificities and accuracies of HS SPECT and conventional SPECT in relation to automated TPD assessment were 89% (31/35), 57% (8/14) and 80% (39/49) vs. 86% (31/36), 77% (10/13) and 84% (41/49), respectively.

CONCLUSION

HS SPECT allows fast acquisition of myocardial perfusion images that correlate well with angiographic findings with overall accuracy by visual assessment better than conventional SPECT. Further assessment in a larger patient population may be needed to confirm this observation.

Assessment of myocardial perfusion and viability by positron emission tomography

An important evolution has taken place recently in the field of cardiovascular Positron Emission Tomography (PET) imaging. Being originally a highly versatile research tool that has contributed significantly to advance our understanding of cardiovascular physiology and pathophysiology, PET has gradually been incorporated into the clinical cardiac imaging portfolio contributing to diagnosis and management of patients investigated for coronary artery disease (CAD). PET myocardial perfusion imaging (MPI) has an average sensitivity and specificity around 90% for the detection of angiographically significant CAD and it is also a very accurate technique for prognostication of patients with suspected or known CAD. In clinical practice, Rubidium-82 ((82)Rb) is the most widely used radiopharmaceutical for MPI that affords also accurate and reproducible quantification in absolute terms (ml/min/g) comparable to that obtained by cyclotron produced tracers such as Nitrogen-13 ammonia ((13)N-ammonia) and Oxygen-15 labeled water ((15)O-water). Quantification increases sensitivity for detection of multivessel CAD and it may also be helpful for detection of early stages of atherosclerosis or microvascular dysfunction. PET imaging combining perfusion with myocardial metabolism using (18)F-Fluorodeoxyglucose ((18)F FDG), a glucose analog, is an accurate standard for assessment of myocardial hibernation and risk stratification of patients with left ventricular dysfunction of ischemic etiology. It is helpful for guiding management decisions regarding revascularization or medical treatment and predicting improvement of symptoms, exercise capacity and quality of life post-revascularization. The strengths of PET can be increased further with the introduction of hybrid scanners, which combine PET with computed tomography (PET/CT) or with magnetic resonance imaging (PET/MRI) offering integrated morphological, biological and physiological information and hence, comprehensive evaluation of the consequences of atherosclerosis in the coronary arteries and the myocardium.

Effect of body mass index on the efficacy, side effect profile, and plasma concentration of fixed-dose regadenoson for myocardial perfusion imaging

BACKGROUND

There are limited data on the effect of body mass index (BMI) on the actions of fixed-dose regadenoson. The purpose of this study was to determine the effect of BMI on the efficacy, side effects, and plasma concentration of regadenoson for Myocardial Perfusion Imaging (MPI).

METHODS AND RESULTS

The study included 2,015 subjects from the ADVANCE MPI trials. Initial adenosine MPI was followed by randomization to regadenoson (400-μg bolus injection) or adenosine (6-minute infusion) MPI. Subjects were classified according to BMI into six categories from underweight (<20 kg/m(2)) to extremely obese (≥40 kg/m(2)). PK modeling was used to predict the effect of BMI on plasma regadenoson concentration (PRC). Adenosine-regadenoson agreement rates for the presence and extent of reversibility were similar across BMI categories (P > .05). The incidence of side effects was also similar across BMIs (P ≥ .06). Subjects were less likely to feel very or extremely uncomfortable after regadenoson vs adenosine in all groups with BMI ≥ 25 kg/m(2), but this trend was not statistically significant in subjects with BMI 20-24 kg/m(2) (P > .05). PRC was inversely related to BMI with 19% higher PRC in the underweight and 36% lower PRC in the extremely obese compared with a normal weight subject.

CONCLUSIONS

BMI does not alter the efficacy of regadenoson MPI despite lower PRC in high BMI subjects, or its side effect profile despite higher PRC in low BMI subjects. Regadenoson is better tolerated than adenosine but this benefit seems to lose statistical significance in subjects with BMI < 25 kg/m(2).

Prevalence of myocardial perfusion abnormalities in end-stage liver disease

BACKGROUND

The prevalence of coronary artery disease (CAD) in end-stage liver disease (ESLD) being evaluated for orthotopic liver transplantation (OLT) is unclear based on variable definition used for CAD.

OBJECTIVE

The aim of this study to investigate the prevalence of abnormal stress myocardial perfusion single-photon emission computed tomography (MPS) imaging, as a marker for CAD, among patients with ESLD who were referred for stress MPS imaging as a routine work up before OLT.

MATERIALS AND METHODS

This was a single-center, retrospective study. We reviewed data on 167 patients who were referred for MPS as a routine work up before OLT over the last 2 years. All patients underwent evaluation for CAD risk factors [age, hypercholesterolemia, diabetes mellitus (DM), hypertension (HTN), and smoking], and stress MPS as per standard protocol.

RESULTS

The total number of patients referred for stress MPS was 167. Seven patients (4% of total study population) were excluded from the study due to poor and/or nondiagnostic studies. 147 patients (92%) had normal, but only 13 patients (8%) had abnormal MPS scans. DM and male gender were the most independent risk factors for abnormal MPS with P value of 0.046, and 0.26, respectively. There was no significant association between the abnormal MPS result and HTN, hypercholesterolemia, smoking, age or etiology of the liver disease.

CONCLUSION

Based on our data, the prevalence of abnormal MPS and left ventricular ejection fraction in patients with ESLD was found to be 8%. DM and male gender were the most independent predictor factors for abnormal MPS. True prevalence of CAD and usefulness of MPS in patients with ESLD can only be studied using a very large and randomized prospective study.

Regadenoson for myocardial perfusion scintigraphy

IMPORTANCE OF THE FIELD

Stress myocardial perfusion scintigraphy (MPS) plays a major role in the detection of obstructive coronary artery disease and provides valuable diagnostic and prognostic information to guide clinical decision-making with regard to medical therapy and coronary revascularisation. Current stress techniques for MPS are effective but their use may be limited by reduced tolerability, contraindications and untoward side effects. The recently developed selective adenosine A2A receptor agonists have the potential for improving stress tolerability, hence expanding the indications for functional imaging in the assessment of coronary artery disease.

AREAS COVERED IN THIS REVIEW

This article reviews the basic principles underlying activation of coronary arteriolar adenosine A2A receptors. It describes the benefits and limitations of current vasodilator stress agents and highlights the effectiveness, side effect profile and tolerability of regadenoson, the only selective adenosine A2A receptor agonist available at present for clinical use.

WHAT THE READER WILL GAIN

The reader will gain an understanding of the pharmacokinetics and mechanism of action of regadenoson for the assessment of coronary artery disease when combined with myocardial perfusion imaging. The reader will also become aware of the available evidence on the clinical usefulness of regadenoson MPS and its future applications.

TAKE HOME MESSAGE

Selective activation of coronary arteriolar adenosine A2A receptors by regadenoson provides an effective modality of stress for the detection of inducible perfusion abnormality in patients with known or suspected coronary disease. The effectiveness of regadenoson is similar to that of adenosine, but test tolerability is improved with regadenoson. The use of this agent simplifies stress testing and has the potential for expanding the applications of functional imaging to patient populations unsuitable for conventional vasodilator stress with adenosine or dipyridamole.

Cardiac radionuclide imaging in stable coronary artery disease and acute coronary syndromes

INTRODUCTION

The increasing number of available cardiac imaging techniques has made the investigation of coronary artery disease (CAD) more complex. Appropriate patient referral depends on an understanding of the pre-test likelihood of CAD and the information provided by each test.

SOURCES OF DATA

This article describes myocardial perfusion scintigraphy (MPS) and summarizes evidence for its role in stable CAD and acute coronary syndromes with particular reference to current guidelines.

AREAS OF AGREEMENT

MPS has been extensively validated for the cost-effective diagnosis and prognosis of functionally significant CAD in both the acute and chronic settings. Its use is emphasized in the current NICE, national and international guidelines.

AREAS OF CONTROVERSY

Although normal MPS is associated with good outcomes, assessments of subclinical atherosclerosis such as coronary artery calcium scoring and computed tomography coronary angiography (CTA) demonstrate that non-flow-limiting CAD remains prognostically important.

GROWING POINTS

Technological developments, such as attenuation correction to improve diagnostic accuracy or analysis of left ventricular phase to detect dyssynchrony, carry the possibility of increasing the information that can be usefully gained from a single MPS study.

AREAS TIMELY FOR DEVELOPING RESEARCH

Of particular importance will be the role of MPS in an integrated imaging strategy that involves both anatomical and functional cardiac assessments. The use of hybrid technology that combines techniques such as MPS and CTA into a single imaging unit requires careful consideration with regard to diagnostic usefulness and cost-effectiveness.

Cardiac evaluation of liver transplant candidates

Physicians previously thought that heart disease was rare in patients with end stage liver disease. However, recent evidence shows that the prevalence of ischemic heart disease and cardiomyopathy is increased in transplant candidates compared to most other surgical candidates. Investigators estimate that up to 26% of all liver transplant candidates have at least one critical coronary artery stenosis and that at least half of these patients will die perioperatively of cardiac complications. Cardiomyopathy also occurs in greater frequency. While all patients with advanced cardiac disease have defects in cardiac performance, a larger than expected number of patients have classical findings of dilated, restrictive and hypertrophic cardiomyopathy. This may explain why up to 56% of patients suffer from hypoxemia due to pulmonary edema following transplant surgery. There is considerable controversy on how to screen transplant candidates for the presence of heart disease. Questions focus upon, which patients should be screened and what tests should be used. This review examines screening strategies for transplant candidates and details the prognostic value of common tests used to identify ischemic heart disease. We also review the physiological consequences of cardiomyopathy in transplant candidates and explore the specific syndrome of “cirrhotic cardiomyopathy”.

Side effect profile and tolerability of adenosine myocardial perfusion scintigraphy in patients with mild asthma or chronic obstructive pulmonary disease

BACKGROUND

Adenosine may cause bronchoconstriction in subjects with asthma or chronic obstructive pulmonary disease (COPD). Recent evidence suggests that this effect may be dependent on the severity of disease. This study investigates the tolerability of adenosine stress in patients with mild asthma or COPD undergoing myocardial perfusion scintigraphy.

METHODS AND RESULTS

In this case-control study patients with known or suspected mild asthma or COPD were pretreated with an inhaled beta(2)-adrenergic agonist and adenosine titrated up to the maximal dose of 140 microg x kg(-1) x min(-1) over a period of 6 minutes. The occurrence of side effects and test tolerability were compared between the airway disease group and 72 control subjects. Of 1261 patients, 124 had known or suspected airway disease; of these, 72 (58%) were suitable for adenosine stress. The proportion of tests completed as per protocol in the asthma/COPD group was similar to that of control subjects (93% vs 100%, P = .06). Dyspnea (n = 38 [53%] in asthma/COPD group vs n = 25 [35%] in control group, P = .03) and chest pain (n = 14 [19%] in asthma/COPD group vs n = 16 [22%] in control group, P = .7) were the most common side effects, and these were mostly mild and well tolerated. Bronchospasm occurred in 5 patients with asthma/COPD but reverted shortly after discontinuation of the adenosine infusion. Aminophylline was not required in any case.

CONCLUSIONS

A stepwise 6-minute adenosine infusion with prophylactic beta(2)-adrenergic agonist is safe and well tolerated in patients with mild asthma or COPD.

A comparison of Tl-201, Tc-99m sestamibi, and Tc-99m tetrofosmin myocardial perfusion scintigraphy in patients with mild to moderate coronary stenosis

BACKGROUND

Thallium 201, technetium 99m sestamibi (MIBI), and Tc-99m tetrofosmin differ in their myocardial uptake characteristics. This may make the technetium tracers less sensitive for detecting mild to moderate coronary stenosis.

METHODS AND RESULTS

We identified 163 patients with angiographic mild to moderate stenosis (50%-89%) and coexistent severe disease (88/163 patients) from a previous study of patients who received either thallium, MIBI, or tetrofosmin for myocardial perfusion scintigraphy. Summed segmental uptake scores were used to assess myocardial perfusion of territories supplied by the mildly to moderately stenotic vessels. Mean (+/- SD) summed stress uptake scores in the left anterior descending artery territory were 21.4 +/- 3.8, 21.6 +/- 4.2, and 22.1 +/- 2.3 for thallium, MIBI, and tetrofosmin, respectively (P = .7); mean summed difference uptake scores were 1.2 +/- 1.8, 1.1 +/- 1.9, and 1.0 +/- 1.1, respectively (P = .8). In the non-left anterior descending artery territory, mean summed stress uptake scores were 32.5 +/- 6.3, 34.0 +/- 6.3, and 34.5 +/- 4.7 for thallium, MIBI, and tetrofosmin, respectively (P = .4), whereas mean summed difference scores were 1.9 +/- 2.6, 1.7 +/- 2.2, and 1.7 +/- 2.3, respectively (P = .9).

CONCLUSION

There were no significant differences between the tracers for the summed uptake scores. This suggests that the 3 tracers are comparable in clinical practice for assessing the extent and severity of perfusion abnormalities arising from mild to moderate coronary artery stenosis, especially in the presence of coexistent severe disease.

Use of B-type natriuretic peptide in the detection of myocardial ischemia

BACKGROUND

Exercise electrocardiography (ECG) has high specificity but limited sensitivity for the detection of myocardial ischemia. The aim of this study was to determine whether measurement of B-type natriuretic peptide (BNP) can improve the diagnostic accuracy of exercise ECG.

METHODS

A total of 256 consecutive patients with suspected myocardial ischemia referred for rest/ergometry myocardial perfusion single-photon emission computed tomography were enrolled. Levels of BNP were determined before and 1 minute after maximal exercise.

RESULT

Inducible myocardial ischemia on perfusion images was detected in 127 patients (49.6%). Median BNP levels at rest and after peak exercise were higher in patients with than without inducible ischemia (71 pg/mL vs 38 pg/mL, P < .001; and 88 vs 52 pg/mL, P < .001, respectively). Compared with patients in the lowest peak exercise BNP quartile, those in the highest quartile of peak exercise BNP had more than 3 times the risk of inducible ischemia (adjusted relative risk 3.3, 95% CI 1.3-8.6, P = .015). Using 110 pg/mL as a cutoff, the combination of exercise ECG and peak exercise BNP level distinguished between ischemic and nonischemic patients more accurately than the exercise ECG alone (67% vs 60%, P = .024). Although the increase in accuracy was similar for the combination of exercise ECG with baseline BNP or DeltaBNP, overall, peak exercise BNP seemed to be the preferred measurement.

CONCLUSIONS

B-type natriuretic peptide levels are associated with inducible myocardial ischemia. The use of BNP levels improves the diagnostic accuracy of exercise ECG.