CT angiography for safe discharge of patients with possible acute coronary syndromes

CCTA in patients with positive troponin and low clinical suspicion for ACS: a useful diagnostic option to exclude obstructive CAD

PURPOSE

It is uncertain whether patients with elevated troponin and non-classical presentation of acute coronary syndrome (ACS) should receive coronary CT angiography (CCTA). A proportion of these patients will have no coronary artery disease (CAD) and would benefit from non-invasive investigations and expedited discharge. Objectives were to determine most common diagnoses and rate of ACS among patients with positive troponin and low clinical suspicion of ACS who received CCTA.

METHODS

IRB approved retrospective analysis of 491 consecutive patients in a level I trauma center ED referred for CCTA between April 4, 2015 to April 2, 2017. Patients were included if there was an elevated troponin (TnI > 0.045 μg/L) and atypical chest pain within 24 h prior to imaging. One hundred one patients met inclusion criteria; 17 excluded due to technical factors or history. Scans performed on dual-source CT.

RESULTS

Eighty-four patients (47 men, 37 women) with median TnI of 0.11 ± 0.21 μg/L underwent CCTA 8.20 ± 6.41 h after first elevated Tn. Mean age was 53.2 ± 14.6 years. CCTA demonstrated absence of CAD in 39 patients (46.4%; 20 M, 19 F). CAD < 25% stenosis was observed in 24 (28.6%; 9 M, 15 F). CAD with 25-50% stenosis was observed in seven (8.3%; six M, one F). CAD > 50% stenosis was observed in 11 (13.1%; 9 M, 2 F), and non-diagnostic in three (3.6%, 3 M, 0 F). Forty-six (56.8%) were discharged directly from ED with median stay 15.82 ± 6.41 h.

CONCLUSIONS

Use of CCTA in ED patients with elevated troponin and low clinical suspicion for ACS allowed obstructive CAD to be excluded in 83%.

Chest pain CT in the emergency department: Watch out for the myocardium

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Hypodense myocardium (HM) can be observed often in chest pain CT examinations of patients presenting to the emergency department with chest pain.

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There is benefit when the myocardium is also analyzed for the presence of HM, even when the heart and coronary arteries were not specifically asked-for.

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Sensitivity, specificity, PPV and NPV for the detection of acute myocardial infarction by assessing HM was 52%, 100%, 100% and 95% respectively.

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Assessment of hypodense myocardium may increase the diagnostic confidence in ambiguous coronary findings in chest pain CT.

Rationale and Objectives

To evaluate the frequency and relevance of hypodense myocardium (HM) encountered in patients undergoing chest-pain CT in the emergency department (ED).

Material and Methods

In this IRB-approved retrospective study, ECG-gated chest-pain CT examinations of 300 consecutive patients (mean age 60 ± 17 years) presenting with acute chest-pain to our ED were evaluated. Once ST-segment elevation infarction was excluded, chest-pain CT including the coronary arteries (rule-out acute coronary syndrome (ACS), pulmonary embolism (PE) and acute aortic syndrome (AAS): chest-pain CT_coronary, n = 121) or not including the coronary arteries was performed (rule-out PE and AAS: chest-pain CT_{w/o coronary}, n = 179). Each myocardial segment was assessed for the presence of HM; attenuation was measured and compared to normal myocardium.

Results

HM was identified in 27/300 patients (9%): 12/179 in chest-pain CT_{w/o coronary} (7%) and 15/121 in chest-pain CT_coronary (12%). Mean attenuation of HM (40 ± 17 HU) was significantly lower than that of healthy myocardium (103 ± 18 HU, p < 0.001), with a mean difference of 61 ± 19 HU. In 15/27 patients (55.6%) with HM, the final diagnosis was acute MI, and in the remaining 12/27 patients (44.4%) previous MI was found in the patients’ history. Chest-pain CT_{w/o coronary} identified HM in 10/15 patients (66.6%) with a final diagnosis of acute MI.

Conclusion

HM indicating acute MI are often encountered in chest pain CT in the ED, also in chest-pain CT_{w/o coronary} when MI is not suspected. This indicates that the myocardium should always be analyzed for hypodense regions even when MI not suspected.

Acute Coronary and Acute Aortic Syndromes

Multidetector-row computed tomography (MDCT) can provide crucial information and rapid triage of emergency department patients with suspected acute coronary syndrome (ACS) or acute aortic syndrome (AAS). Coronary computed tomography angiography has high negative predictive value to rule out ACS, and MDCT is diagnostic for AAS and its variants. Optimization of acquisition technique and up-to-date knowledge of the pathophysiology of these conditions can improve study and interpretation quality for diagnosis of ACS or AAS.

Secondary cardiac risk stratifying tests after coronary computed tomography angiography in emergency department patients

BACKGROUND

Several large trials demonstrated that coronary computed tomography angiography (CTA) in a triage strategy could lead to increased secondary cardiac risk stratifying testing (SCRST). Whether this is true for routine clinical care remains unclear. We measured SCRSTs after coronary CTA was implemented in our emergency department (ED) practice by CTA result, and if locally existing management recommendations for a structured post CTA diagnostic strategy were followed.

METHODS

This single site retrospective cohort study included all our ED patients who received coronary CTA between October 1, 2012 and September 30, 2016. SCRST's included functional cardiac tests and invasive coronary angiography (ICA), performed during the ED coronary CTA visit or related admission.

RESULTS

A total of 1916 subjects were included with a mean age of 52.9 ± 10.8 years. Of their coronary CTAs, 179 were positive (severe stenosis, occlusion or ventricular wall motion abnormalities; 9.3%), 105 intermediate (moderate stenosis; 5.5%), 1611 negative (no to mild obstructive CAD; 84.1%) and 21 non-diagnostic (1.1%). SCRSTs were performed in 237 (overall 12.4%, noninvasive in 5.6%, ICA in 6.7%). After positive coronary CTA, 73.7% of subjects received SCRSTs. For intermediate, negative and non-diagnostic CTAs this was 72.4%, 1.1% and 47.6% respectively. Management conformed to local management recommendations in 96.2% of cases.

CONCLUSION

In spite of previous trials, rates of secondary cardiac risk stratifying tests after routine clinical ED coronary CTA are low, especially in patients with negative coronary CTA. Structured management guidelines for post coronary CTA, and adherence to these guidelines, appear essential.

Clinical Implications of Moderate Coronary Stenosis on Coronary Computed Tomography Angiography in Patients with Stable Angina

PURPOSE

The present study investigated the diagnostic accuracy and clinical implications of moderate stenosis (50-69%, Coronary Artery Disease Reporting and Data System, grade 3) on coronary computed tomography angiography (CCTA), compared with invasive coronary angiography (ICA).

MATERIALS AND METHODS

Two hundred and seventy-six patients who underwent ICA due to moderate stenosis alone on CCTA were selected from our prospective registry cohort.

RESULTS

Diagnostic concordance between CCTA and ICA was found in only 50 (18%) patients. Among the 396 vessels and 508 segments with moderate stenosis, diagnostic concordance was found in 132 vessels (33%) and 127 segments (25%). Segments with calcified plaque had lower diagnostic concordance than those with mixed or non-calcified plaque (22% vs. 28% vs. 27%, respectively, p=0.001). While calcified plaque burden did not have an influence on severe stenosis (≥70%) on ICA, higher burden of non-calcified plaque was correlated with a greater incidence of ICA-based severe stenosis, which was more frequent in patients with ≥3 segments of non-calcified plaque (75%) than those without non-calcified plaque (22%, p<0.001). Typical angina and mixed or non-calcified plaque were correlated with a higher incidence of under-diagnosis, while the use of next-generation computed tomography scanners reduced the incidence of under-diagnosis. Increased body weight, left circumflex artery involvement, and calcified plaque were independent factors that increased the risk of over-diagnosis of CCTA.

CONCLUSION

The diagnosis of moderate stenosis by CCTA may be limited in estimating the exact degree of ICA-based anatomical stenosis. Unlike calcific burden, non-calcific burden was positively correlated with the presence of severe stenosis on ICA.

Risk stratification and role for additional diagnostic testing in patients with acute chest pain and normal high-sensitivity cardiac troponin levels

Background

Normal high sensitivity cardiac troponin (hs-cTn) assays rule out acute myocardial infarction (AMI) with great accuracy, but additional non-invasive testing is frequently ordered. This observational study evaluates whether clinical characteristics can contribute to risk stratification and could guide referral for additional testing.

Methods

918 serial patients with acute chest pain and normal hs-cTnT levels were prospectively included. Major adverse cardiac events (MACE) and non-invasive test results were assessed during one-year follow-up. Patients were classified as low and high risk based on clinical characteristics.

Results

MACE occurred in 6.1% of patients and mainly comprised revascularizations (86%). A recent abnormal stress test, suspicious history, a positive family history and higher baseline hs-cTnT levels were independent predictors of MACE with odds ratios of 16.00 (95%CI:6.25–40.96), 16.43 (6.36–42.45), 2.33 (1.22–4.42) and 1.10 (1.01–1.21), respectively. Absence of both recent abnormal stress test and suspicious history identified 86% of patients. These patients were at very low risk for MACE (0.4% in 30-days and 2.3% in one-year). Despite this, the majority (287/345 = 83%) of additional tests were performed in low risk patients, with <10% abnormal test findings. The diagnostic yield was significantly higher in the remaining higher risk patients, 40% abnormal test findings and a positive predictive value of 70% for MACE. Similar results were observed in patients without known coronary artery disease.

Conclusions

Clinical characteristics can be used to identify low risk patients with acute chest pain and normal hs-cTnT levels. Current strategies in the emergency department result in numerous additional tests, which are mostly ordered in patients at very low risk and have a low diagnostic yield.

Received care compared to ADP-guided care of patients admitted to hospital with chest pain of possible cardiac origin

Purpose

To assess the extent to which accelerated diagnostic protocols (ADPs), compared to traditional care, identify patients presenting to emergency departments (EDs) with chest pain who are at low cardiac risk and eligible for early ED discharge.

Patients and methods

Retrospective study of 290 patients admitted to hospital for further evaluation of chest pain following negative ED workup (no acute ischemic electrocardiogram [ECG] changes or elevation of initial serum troponin assay). Demographic data, serial ECG and troponin results, Thrombolysis in Myocardial Infarction (TIMI) score, cardiac investigations, and outcomes (confirmed acute coronary syndrome [ACS] at discharge and major adverse cardiac events [MACEs]) over 6 months of follow-up were analyzed. A validated ADP (ADAPT-ADP) was retrospectively applied to the cohort, and processes and outcomes of ADP-guided care were compared with those of care actually received.

Results

Patients had mean (±SD) TIMI score of 1.8 (±1.7); six (2.0%) patients were diagnosed with ACS at discharge. At 6 months, one patient (0.3%) re-presented with ACS and two (0.6%) died of non-coronary causes. The ADAPT-ADP defined 97 (33.4%) patients as being at low risk and eligible for early ED discharge, but who instead incurred mean hospital stay of 1.5 days, with 40.2% in telemetry beds, and 21.6% subject to non-invasive testing with only one positive result for coronary artery disease. None had a discharge diagnosis of ACS or developed MACE at 6 months.

Conclusion

Compared to traditional care, application of the ADAPT-ADP would have allowed one-third of chest pain patients with initially negative investigations in ED to have been safely discharged from ED.

Calcification of the heart: mechanisms and therapeutic avenues

INTRODUCTION

Coronary artery calcification (CAC) is reflective of atherosclerotic disease and incrementally predictive of future cardiovascular events (CVE), independent of traditional risk factors. Extra coronary calcium such as aortic valve calcification, which can be identified and quantified by computed tomography (CT) imaging, has shown to predict future CVE in both asymptomatic and symptomatic (i.e. stable angina and acute coronary syndrome [ACS]) settings. It has hence been a vital tool in studies involving new therapies for cardiovascular disease. Areas covered: In this review, promising therapies on the horizon are reviewed, along with the role of cardiac CT and coronary calcification in these studies. A Medline search for peer-reviewed publications using keywords related to coronary calcium score, aortic valve calcium, and therapies targeting the same was carried out. Expert commentary: CT scanning provides a distinct means of detecting and quantifying coronary plaque as well as valvular calcification with excellent reproducibility. Based on voluminous data available, the absence of coronary calcium serves as a factor to de-risk patients for cardiovascular risk stratification and management algorithms. Newer therapies have shown to lower progression of coronary calcification, thus being beneficial in slowing progression of atherosclerotic disease. As British Epidemiologist Geoffrey Rose states, the best predictor of a life-threatening disease is the early manifestation of that disease. As CAC represents the early manifestation of atherosclerosis, it is the best-known stratifier of risk today, and its clinical use will continue to rise.

Utility of Physician Selection of Cardiac Tests in a Chest Pain Unit to Exclude Acute Coronary Syndrome Among Patients Without a History of Coronary Artery Disease

There are few data on the utility of physician selection of cardiac tests, including no-test, in a chest pain unit (CPU) to rule out acute coronary syndrome in low-risk patients without a history of coronary artery disease. We analyzed consecutive low-risk patients admitted to our CPU between 2012 and 2014 and determined the proportion of patients selected for testing, the type of initial cardiac test selected, and the incidence of major adverse cardiac events (MACEs) at 30 days and 6 months. The study group comprised 619 patients: mean age 57 years (27 to 92), 332 women (54%), and 360 (58%) with multiple cardiac risk factors. Cardiac testing included 283 no-test (46%); 179 exercise treadmill (29%); 113 myocardial perfusion stress scintigraphy (18%); <10% each for exercise stress echocardiography and coronary angiography. Testing was negative in 296 (88%), nondiagnostic in 30 (9%), and positive in 10 patients (3%). There were no MACEs at 30 days in any patients, and at 6 months, MACEs were 5 (1.1%). Length of stay was less in no-test than in tested patients (5.4 hours vs 9.8 hours, p <0.0001), and there was no difference in incidence of MACE at 6 months in no-test vs tested patients (2 MACEs vs 3 MACEs). Physician selection of cardiac tests, including no-test, promptly identified patients at low risk of acute coronary syndrome who could be safely and rapidly discharged from the CPU. Exclusion of cardiac testing shortened length of stay and was not associated with increase in MACE at 6 months.

Thyrotropin and free thyroxine levels and coronary artery disease: cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Data on the association between subclinical thyroid dysfunction and coronary artery disease (CAD) is scarce. We aimed to analyze the association between thyroid function and CAD using baseline data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). We included subjects with normal thyroid function (0.4-4.0 mIU/L, and normal free thyroxine, FT4, or 0.8 to 1.9 ng/dL), subclinical hypothyroidism (SCHypo; TSH>4.0 mIU/L and normal FT4), and subclinical hyperthyroidism (SCHyper; TSH<0.4 mIU/L and normal FT4) evaluated by coronary computed tomography angiography. We excluded individuals using medications that interfere in thyroid function or with past medical history of cardiovascular disease. Logistic regression models evaluated the presence of CAD, segment involvement score (SIS) >4, and segment severity score (SSS) >4 of coronary arteries as the dependent variables, and quintiles of TSH and FT4 as the independent variables, adjusted for demographical data and cardiovascular risk factors. We included 767 subjects, median age 58 years (IQR=55-63), 378 (49.3%) women, 697 euthyroid (90.9%), 57 (7.4%) with SCHypo, and 13 (1.7%) with SCHyper. No association between TSH and FT4 quintiles and CAD prevalence was noted. Similarly, no association between TSH levels and the extent or severity of CAD, represented by SIS>4 and SSS>4 were seen. Restricting analysis to euthyroid subjects did not alter the results. TSH levels were not significantly associated with the presence, extent, or severity of CAD in a middle-aged healthy population.

Cardiac CT in the Emergency Department: Contrasting Evidence from Registries and Randomized Controlled Trials

PURPOSE OF REVIEW

To compare outcomes between registries and randomized controlled trials of coronary computed tomographic angiography (CCTA)-based versus standard of care approaches to the initial evaluation of patients with acute chest pain.

RECENT FINDINGS

Randomized trials have demonstrated CCTA to be a safe and efficient tool for triage of low- to intermediate-risk patients presenting to the emergency department with chest pain. Recent studies demonstrate heterogeneous result using different standard of care approaches for evaluation of hard endpoints in comparison with standard evaluation. Also, there has been continued concern for increase in subsequent testing after coronary CTA. Although CCTA improves detection of coronary artery disease, it is uncertain if it will bring improvement of long-term health outcomes at this point of time. Careful analysis of the previous results and further investigation will be required to validate evaluation of hard endpoints.

Outcomes of non-invasive diagnostic modalities for the detection of coronary artery disease: network meta-analysis of diagnostic randomised controlled trials

OBJECTIVE

To evaluate differences in downstream testing, coronary revascularisation, and clinical outcomes following non-invasive diagnostic modalities used to detect coronary artery disease.

DESIGN

Systematic review and network meta-analysis.

DATA SOURCES

Medline, Medline in process, Embase, Cochrane Library for clinical trials, PubMed, Web of Science, SCOPUS, WHO International Clinical Trials Registry Platform, and Clinicaltrials.gov.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Diagnostic randomised controlled trials comparing non-invasive diagnostic modalities in patients presenting with symptoms suggestive of low risk acute coronary syndrome or stable coronary artery disease.

DATA SYNTHESIS

A random effects network meta-analysis synthesised available evidence from trials evaluating the effect of non-invasive diagnostic modalities on downstream testing and patient oriented outcomes in patients with suspected coronary artery disease. Modalities included exercise electrocardiograms, stress echocardiography, single photon emission computed tomography-myocardial perfusion imaging, real time myocardial contrast echocardiography, coronary computed tomographic angiography, and cardiovascular magnetic resonance. Unpublished outcome data were obtained from 11 trials.

RESULTS

18 trials of patients with low risk acute coronary syndrome (n=11 329) and 12 trials of those with suspected stable coronary artery disease (n=22 062) were included. Among patients with low risk acute coronary syndrome, stress echocardiography, cardiovascular magnetic resonance, and exercise electrocardiograms resulted in fewer invasive referrals for coronary angiography than coronary computed tomographic angiography (odds ratio 0.28 (95% confidence interval 0.14 to 0.57), 0.32 (0.15 to 0.71), and 0.53 (0.28 to 1.00), respectively). There was no effect on the subsequent risk of myocardial infarction, but estimates were imprecise. Heterogeneity and inconsistency were low. In patients with suspected stable coronary artery disease, an initial diagnostic strategy of stress echocardiography or single photon emission computed tomography-myocardial perfusion imaging resulted in fewer downstream tests than coronary computed tomographic angiography (0.24 (0.08 to 0.74) and 0.57 (0.37 to 0.87), respectively). However, exercise electrocardiograms yielded the highest downstream testing rate. Estimates for death and myocardial infarction were imprecise without clear discrimination between strategies.

CONCLUSIONS

For patients with low risk acute coronary syndrome, an initial diagnostic strategy of stress echocardiography or cardiovascular magnetic resonance is associated with fewer referrals for invasive coronary angiography and revascularisation procedures than non-invasive anatomical testing, without apparent impact on the future risk of myocardial infarction. For suspected stable coronary artery disease, there was no clear discrimination between diagnostic strategies regarding the subsequent need for invasive coronary angiography, and differences in the risk of myocardial infarction cannot be ruled out.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registry no CRD42016049442.

Utility of multiple rule out CT screening of high-risk atraumatic patients in an emergency department-a feasibility study

BACKGROUND

Several large trials have evaluated the effect of CT screening based on specific symptoms, with varying outcomes. Screening of patients with CT based on their prognosis alone has not been examined before. For moderate-to-high risk patients presenting in the emergency department (ED), the potential gain from a CT scan might outweigh the risk of radiation exposure. We hypothesized that an accelerated "multiple rule out" CT screening of moderate-to-high risk patients will detect many clinically unrecognized diagnoses that affect change in treatment.

METHOD

Patients ≥ 40 years, triaged as high-risk or moderate-to-high risk according to vital signs, were eligible for inclusion. Patients were scanned with a combined ECG-gated and dual energy CT scan of cerebrum, thorax, and abdomen. The impact of the CT scan on patient diagnosis and treatment was examined prospectively by an expert panel.

RESULTS

A total of 100 patients were included in the study, (53% female, mean age 73 years [age range, 43-93]). The scan lead to change in treatment or additional examinations in 37 (37%) patients, of which 24 (24%) were diagnostically significant, change in acute treatment in 11 (11%) cases and previously unrecognized malignant tumors in 10 (10%) cases. The mean size specific radiation dose was 15.9 mSv (± 3.1 mSv).

CONCLUSION

Screening with a multi-rule out CT scan of high-risk patients in an ED is feasible and result in discovery of clinically unrecognized diagnoses and malignant tumors, but at the cost of radiation exposure and downstream examinations. The clinical impact of these findings should be evaluated in a larger randomized cohort.

Coronary CT Angiography: Use in Patients With Chest Pain Presenting to Emergency Departments

OBJECTIVE

Previously published reports have shown that coronary CT angiography (CCTA) is a more efficient method of diagnosis than myocardial perfusion imaging (MPI) and stress echocardiography for patients presenting to emergency departments (EDs) with acute chest pain. In light of this evidence, the objective of this study was to examine recent trends in the use of these techniques in EDs.

MATERIALS AND METHODS

The nationwide Medicare Part B databases for 2006-2015 were the data source. The Current Procedural Terminology, version 4, codes for CCTA, MPI, and stress echocardiography were selected. Medicare place-of-service codes were used to determine procedure volumes in EDs. Medicare specialty codes were used to ascertain how many of these examinations were interpreted by radiologists, cardiologists, and other physicians as a group.

RESULTS

From 2006 to 2015, there was essentially no change in the number of MPI examinations performed in EDs for patients using Medicare (22,342 in 2006, 22,338 in 2015) or in the number of stress echocardiograms (3544 in 2006, 3520 in 2015). By contrast, the number of CCTA examinations increased rapidly, from 126 in 2006 to 1919 in 2015 (compound annual growth rate, 35%). Despite this rapid growth, patients in EDs underwent 11.6 times as many MPI as CCTA examinations in 2015. In that last year of the study, radiologists interpreted 78% of ED MPI and 83% of ED CCTA examinations.

CONCLUSION

Use of CCTA in EDs has increased rapidly, but far more MPI examinations are still being performed. This finding suggests that recently acquired evidence is not yet being fully acted upon.

SEALONE (Safety and Efficacy of Coronary Computed Tomography Angiography with Low Dose in Patients Visiting Emergency Room) trial: study protocol for a randomized controlled trial

Objective

Chest pain is one of the most common complaints in the emergency department (ED). Cardiac computed tomography angiography (CCTA) is a frequently used tool for the early triage of patients with low- to intermediate-risk acute chest pain. We present a study protocol for a multicenter prospective randomized controlled clinical trial testing the hypothesis that a low-dose CCTA protocol using prospective electrocardiogram (ECG)-triggering and limited-scan range can provide sufficient diagnostic safety for early triage of patients with acute chest pain.

Methods

The trial will include 681 younger adult (aged 20 to 55) patients visiting EDs of three academic hospitals for acute chest pain or equivalent symptoms who require further evaluation to rule out acute coronary syndrome. Participants will be randomly allocated to either low-dose or conventional CCTA protocol at a 2:1 ratio. The low-dose group will undergo CCTA with prospective ECG-triggering and restricted scan range from sub-carina to heart base. The conventional protocol group will undergo CCTA with retrospective ECG-gating covering the entire chest. Patient disposition is determined based on computed tomography findings and clinical progression and all patients are followed for a month. The primary objective is to prove that the chance of experiencing any hard event within 30 days after a negative low-dose CCTA is less than 1%. The secondary objectives are comparisons of the amount of radiation exposure, ED length of stay and overall cost.

Results and Conclusion

Our low-dose protocol is readily applicable to current multi-detector computed tomography devices. If this study proves its safety and efficacy, dose-reduction without purchasing of expensive newer devices would be possible.

Round-the-clock performance of coronary CT angiography for suspected acute coronary syndrome: Results from the BEACON trial

Objective

To assess the image quality of coronary CT angiography (CCTA) for suspected acute coronary syndrome (ACS) outside office hours.

Methods

Patients with symptoms suggestive of an ACS underwent CCTA at the emergency department 24 hours, 7 days a week. A total of 118 patients, of whom 89 (75 %) presented during office hours (weekdays between 07:00 and 17:00) and 29 (25 %) outside office hours (weekdays between 17:00 and 07:00, weekends and holidays) underwent CCTA. Image quality was evaluated per coronary segment by two experienced readers and graded on an ordinal scale ranging from 1 to 3.

Results

There were no significant differences in acquisition parameters, beta-blocker administration or heart rate between patients presenting during office hours and outside office hours. The median quality score per patient was 30.5 [interquartile range 26.0–33.5] for patients presenting during office hours in comparison to 27.5 [19.75–32.0] for patients presenting outside office hours (p=0.043). The number of non-evaluable segments was lower for patients presenting during office hours (0 [0–1.0] vs. 1.0 [0–4.0], p=0.009).

Conclusion

Image quality of CCTA outside office hours in the diagnosis of suspected ACS is diminished.

Key Points

• Quality scores were higher for coronary-CTA during office hours.

• There were no differences in acquisition parameters.

• There was a non-significant trend towards higher heart rates outside office hours.

• Coronary-CTA on the ED requires state-of-the-art scanner technology and sufficiently trained staff.

• Coronary-CTA on the ED needs preparation time and optimisation of the procedure.

Defining Quality in Cardiovascular Imaging: A Scientific Statement From the American Heart Association

The aims of the current statement are to refine the definition of quality in cardiovascular imaging and to propose novel methodological approaches to inform the demonstration of quality in imaging in future clinical trials and registries. We propose defining quality in cardiovascular imaging using an analytical framework put forth by the Institute of Medicine whereby quality was defined as testing being safe, effective, patient-centered, timely, equitable, and efficient. The implications of each of these components of quality health care are as essential for cardiovascular imaging as they are for other areas within health care. Our proposed statement may serve as the foundation for integrating these quality indicators into establishing designations of quality laboratory practices and developing standards for value-based payment reform for imaging services. We also include recommendations for future clinical research to fulfill quality aims within cardiovascular imaging, including clinical hypotheses of improving patient outcomes, the importance of health status as an end point, and deferred testing options. Future research should evolve to define novel methods optimized for the role of cardiovascular imaging for detecting disease and guiding treatment and to demonstrate the role of cardiovascular imaging in facilitating healthcare quality.

Chest pain triage: Current trends in the emergency departments in the United States

Chest pain is one of the most common complaints in the emergency department (ED). Over the past decade, there has been a significant shift in the approach to patients with chest pain in the ED. With the development of improved cardiac biomarkers, the validation of clinical scoring systems, and an increasing emphasis on shared patient medical decision making, increasing numbers of patients in the ED are being evaluated without requiring admission to the hospital.

Incidental pulmonary nodules in emergent coronary CT angiography for suspected acute coronary syndrome: Impact of revised 2017 Fleischner Society Guidelines

BACKGROUND

Pulmonary nodules (PN) are frequently detected incidentally during coronary computed tomography angiography (CTA). We evaluated whether the 2017 Fleischner Society guidelines may result in a decrease of follow-up testing of incidental PN as compared to prior guidelines in patients undergoing coronary CTA.

METHODS

We conducted a retrospective study of a registry of emergency department patients who underwent coronary CTA for acute coronary syndrome assessment between 2012 and 2017. Based on guidelines, patients <35 years, history of cancer, or prior exams showing stability of PN were excluded. Patients >60 years, history of smoking, irregular/spiculated PN morphology, or PN size >20 mm were classified as high-risk for lung cancer. Radiological findings pertaining to PN were identified (PN size, morphology, quantity) through review of radiology reports. PN follow-up recommendations were established using 2017 Fleischner Society Guidelines and compared with prior guidelines for solid (2005) and subsolid (2013) PN. Data were analyzed with Student's t-test.

RESULTS

The registry included 2066 patients (female 45.1%, 52.9 ± 11.0 years), of which 578 (28.0%) reported PN. 438 of those (21.2%) were eligible for guideline-based follow-up evaluation. 205 (4 6.8%) were classified as high-risk for lung cancer. 2017 guidelines reduced the number of individuals requiring follow-up by 64.5%, from 264 (12.8%) to 94 patients (4.5%) when compared to prior guidelines (p < 0.001). The minimum number of follow-up chest CTs decreased by 55.8% from 430 to 190 (p < 0.001).

CONCLUSION

Application of the 2017 Fleischner Society Guidelines resulted in a significant decrease of follow-up testing for incidental PN in patients undergoing coronary CTA for suspected acute coronary syndrome.

Advanced Imaging Reduces Cost Compared to Standard of Care in Emergency Department of Triage of Acute Chest Pain

OBJECTIVE

To evaluate medical costs of novel therapies in complex medical settings using registry data.

DATA SOURCE/STUDY SETTING

Primary data, from 2008 to 2010. We used patient registry data to evaluate cost and quality performance of coronary computed tomography angiography (CCTA) in triaging chest pain patients in our tertiary care emergency department and to model financial performance under Medicare's two midnight rule.

STUDY DESIGN

Using generalized linear modeling, we retrospectively compared estimated expenditures for evaluation of low-to-intermediate-risk chest pain for demographic and medically risk matched samples of 894 patients each, triaged with CCTA or local standard of care (SOC) using Medicare reimbursement as a proxy.

DATA COLLECTION/EXTRACTION METHODS

Predefined data elements were downloaded from the hospital mainframe into the CCTA registry, where they were validated and maintained electronically.

PRINCIPLE FINDINGS

We found that predicted standard of care costs were 2.5 times higher on the initial visit and 1.98 times higher over 30 days (p < .001) than those using CCTA. Predicted cost was 1.6 times higher when we applied our two midnight rule model (p < .001).

CONCLUSION

Rapid assessment of treatment using registry data is a promising means of analyzing cost performance in complex health care environments.

Low Adverse Event Rates But High Emergency Department Utilization in Chest Pain Patients Treated in an Emergency Department Observation Unit

OBJECTIVES

Nearly 40% of all previously admitted chest pain patients re-present to the emergency department (ED) within 1 year regardless of stress testing, and nearly 5% of patients return with a major adverse cardiac event (MACE). The primary objective of this study was to determine the prevalence of return visits to the ED among patients previously admitted to an ED chest pain observation unit (CPU). We also identified the patient characteristics and health risk factors associated with these return ED visits.

METHODS

This was a prospective cohort study of patients admitted to a CPU in a large-volume academic urban ED who were subsequently followed over a period of 1 year. Inclusion criteria were age ≥18 years old, American Heart Association low-to-intermediate assessed risk, electrocardiogram nondiagnostic for acute coronary syndrome (ACS), and a negative initial troponin I. Excluded patients were those age >75 years with a history of coronary artery disease. Patients were followed throughout their observation unit stay and then subsequently for 1 year. On all repeat ED evaluations, standardized chart abstractions forms were used, charts were reviewed by 2 trained abstractors blinded to the study hypothesis, and a random sample of charts was examined for interrater reliability. Return visits were categorized as MACE, cardiac non-MACE, or noncardiac based on a priori criteria. Social security death index searches were performed on all patients. Univariate and multivariate ordinal logistic regressions were conducted to determine demographics, medical procedures, and comorbid conditions that predicted return visits to the ED.

RESULTS

A total of 2139 patients were enrolled over 17 months. The median age was 52 years, 55% were female. Forty-four patients (2.1%) had ACS on index visit. A total of 36.2% of CPU patients returned to the ED within 1 year vs. 5.4% of all ED patients (P < 0.01). However, the overall incidence of MACE at 1 year in all patients and in those without an index visit diagnosis of ACS was 0.5% (95% confidence interval [CI], 0.4%-06%) and 0.4% (95% CI, 0.2%-0.7%), respectively. Patients who received a stress test on index visit were less likely to return (adjusted odds ratio [AOR] = 0.64 [95% CI, 0.51-0.80]) but patients who smoked (AOR = 1.51 [95% CI, 1.16-1.96]) or had diabetes (AOR = 1.36 [95% CI, 1.07-1.87]) were more likely to return. Hispanic and African-American patients had increased odds of multiple return ED visits (AOR=1.23 [95% CI, 1.04-1.46] and AOR =1.74 [95% CI, 1.45-2.13], respectively).

CONCLUSION

Patients treated in an ED CPU have a very low rate of MACE at 1 year. However, these same patients have very high rates of subsequent ED utilization. The associations between certain comparative demographics and ED utilization suggest the need for further research to identify and address the needs of these patient populations that precipitate the higher than expected return rate.

High-Sensitivity Cardiac Troponin I as a Gatekeeper for Coronary Computed Tomography Angiography and Stress Testing in Patients with Acute Chest Pain

BACKGROUND

Most patients presenting to the emergency department (ED) with suspected acute coronary syndrome (ACS) undergo noninvasive cardiac testing with a low diagnostic yield. We determined whether a combination of high-sensitivity cardiac troponin I (hs-cTnI) and cardiovascular risk factors might improve selection of patients for cardiac testing.

METHODS

We included patients from the Rule Out Myocardial Infarction/Ischemia Using Computer Assisted Tomography (ROMICAT) I and II trials who presented to the ED with acute chest pain and were referred for cardiac testing. Based on serial hs-cTnI measurements and cardiovascular risk factors, we derived and validated the criterion for no need of cardiac testing. We predicted the effect of this criterion on the effectiveness of patient management.

RESULTS

A combination of baseline hs-cTnI (<4 ng/L) and cardiovascular risk factors (<2) ruled out ACS with a negative predictive value of 100% in ROMICAT I. We validated this criterion in ROMICAT II, identifying 29% patients as not needing cardiac testing. An additional 5% of patients were identified by adding no change or a decrease between baseline and 2 h hs-cTnI as a criterion. Assuming those patients would be discharged from the ED without cardiac testing, implementation of hs-cTnI would increase ED discharge rate (24.3% to 50.2%, P < 0.001) and decrease the length of hospital stay (21.4 to 8.2 h, P < 0.001), radiation dose (10.2 to 7.7 mSv, P < 0.001), and costs of care (4066 to 3342 US$, P < 0.001).

CONCLUSIONS

We derived and validated a criterion for combined hs-cTnI and cardiovascular risk factors that identified acute chest pain patients with no need for cardiac testing and could improve effectiveness of patient management. ClinicalTrials.gov Identifiers: NCT00990262 and NCT01084239.

Coronary Computed Tomography Angiography vs Functional Stress Testing for Patients With Suspected Coronary Artery Disease: A Systematic Review and Meta-analysis

Importance

Coronary computed tomography angiography (CCTA) is a new approach for the diagnosis of anatomical coronary artery disease (CAD), but it is unclear how CCTA performs compared with the standard approach of functional stress testing.

Objective

To compare the clinical effectiveness of CCTA with that of functional stress testing for patients with suspected CAD.

Data Sources

A systematic literature search was conducted in PubMed and MEDLINE for English-language randomized clinical trials of CCTA published from January 1, 2000, to July 10, 2016.

Study Selection

Researchers selected randomized clinical trials that compared a primary strategy of CCTA with that of functional stress testing for patients with suspected CAD and reported data on patient clinical events and changes in therapy.

Data Extraction and Synthesis

Two reviewers independently extracted data from and assessed the quality of the trials. This analysis followed the PRISMA statement for reporting systematic reviews and meta-analyses and used the Cochrane Collaboration's tool for assessing risk of bias in randomized trials. The Mantel-Haenszel method was used to conduct the primary analysis. Summary relative risks were calculated with a random-effects model.

Main Outcomes and Measures

The outcomes of interest were all-cause mortality, cardiac hospitalization, myocardial infarction, invasive coronary angiography, coronary revascularization, new CAD diagnoses, and change in prescription for aspirin and statins.

Results

Thirteen trials were included, with 10 315 patients in the CCTA arm and 9777 patients in the functional stress testing arm who were followed up for a mean duration of 18 months. There were no statistically significant differences between CCTA and functional stress testing in death (1.0% vs 1.1%; risk ratio [RR], 0.93; 95% CI, 0.71-1.21) or cardiac hospitalization (2.7% vs 2.7%; RR, 0.98; 95% CI, 0.79-1.21), but CCTA was associated with a reduction in the incidence of myocardial infarction (0.7% vs 1.1%; RR, 0.71; 95% CI, 0.53-0.96). Patients undergoing CCTA were significantly more likely to undergo invasive coronary angiography (11.7% vs 9.1%; RR, 1.33; 95% CI, 1.12-1.59) and revascularization (7.2% vs 4.5%; RR, 1.86; 95% CI, 1.43-2.43). They were also more likely to receive a diagnosis of new CAD and to have initiated aspirin or statin therapy.

Conclusions and Relevance

Compared with functional stress testing, CCTA is associated with a reduced incidence of myocardial infarction but an increased incidence of invasive coronary angiography, revascularization, CAD diagnoses, and new prescriptions for aspirin and statins. Despite these differences, CCTA is not associated with a reduction in mortality or cardiac hospitalizations.

Prognostic Utility of a Modified HEART Score in Chest Pain Patients in the Emergency Department

BACKGROUND

The TRAPID-AMI trial study (High-Sensitivity Troponin-T Assay for Rapid Rule-Out of Acute Myocardial Infarction) evaluated high-sensitivity cardiac troponin-T (hs-cTnT) in a 1-hour acute myocardial infarction (AMI) exclusion algorithm. Our study objective was to evaluate the prognostic utility of a modified HEART score (m-HS) within this trial.

METHODS AND RESULTS

Twelve centers evaluated 1282 patients in the emergency department for possible AMI from 2011 to 2013. Measurements of hs-cTnT (99th percentile, 14 ng/L) were performed at 0, 1, 2, and 4 to 14 hours. Evaluation for major adverse cardiac events (MACEs) occurred at 30 days (death or AMI). Low-risk patients had an m-HS≤3 and had either hs-cTnT<14 ng/L over serial testing or had AMI excluded by the 1-hour protocol. By the 1-hour protocol, 777 (60%) patients had an AMI excluded. Of those 777 patients, 515 (66.3%) patients had an m-HS≤3, with 1 (0.2%) patient having a MACE, and 262 (33.7%) patients had an m-HS≥4, with 6 (2.3%) patients having MACEs (P=0.007). Over 4 to 14 hours, 661 patients had a hs-cTnT<14 ng/L. Of those 661 patients, 413 (62.5%) patients had an m-HS≤3, with 1 (0.2%) patient having a MACE, and 248 (37.5%) patients had an m-HS≥4, with 5 (2.0%) patients having MACEs (P=0.03).

CONCLUSIONS

Serial testing of hs-cTnT over 1 hour along with application of an m-HS identified a low-risk population that might be able to be directly discharged from the emergency department.

Coronary Artery Disease - Reporting and Data System (CAD-RADS): An Expert Consensus Document of SCCT, ACR and NASCI: Endorsed by the ACC

The intent of CAD-RADS - Coronary Artery Disease Reporting and Data System is to create a standardized method to communicate findings of coronary CT angiography (coronary CTA) in order to facilitate decision-making regarding further patient management. The suggested CAD-RADS classification is applied on a per-patient basis and represents the highest-grade coronary artery lesion documented by coronary CTA. It ranges from CAD-RADS 0 (Zero) for the complete absence of stenosis and plaque to CAD-RADS 5 for the presence of at least one totally occluded coronary artery and should always be interpreted in conjunction with the impression found in the report. Specific recommendations are provided for further management of patients with stable or acute chest pain based on the CAD-RADS classification. The main goal of CAD-RADS is to standardize reporting of coronary CTA results and to facilitate communication of test results to referring physicians along with suggestions for subsequent patient management. In addition, CAD-RADS will provide a framework of standardization that may benefit education, research, peer-review and quality assurance with the potential to ultimately result in improved quality of care.

Comparison of mid- to long-term clinical outcomes between anatomical testing and usual care in patients with suspected coronary artery disease: A meta-analysis of randomized trials

BACKGROUND

Controversies remain regarding clinical outcomes following initial strategies of coronary computed tomography angiography (CCTA) vs usual care with functional testing in patients with suspected coronary artery disease (CAD).

HYPOTHESIS

CCTA as initial diagnostic strategy results in better mid- to long-term outcomes than usual care in patients with suspected CAD.

METHODS

We searched PubMed, Embase, and Cochrane Library for randomized controlled trials comparing clinical outcomes during ≥6 months' follow-up between initial anatomical testing by CCTA vs usual care with functional testing in patients with suspected CAD. Occurrence of all-cause mortality, nonfatal myocardial infarction (MI), and major adverse cardiovascular events (MACE), and use of invasive coronary angiography and coronary revascularization, were compared between the 2 diagnostic strategies.

RESULTS

Twelve trials were included (20 014 patients; mean follow-up, 20.5 months). Patients undergoing CCTA as initial noninvasive testing had lower risk of nonfatal MI compared with those treated with usual care (risk ratio [RR]: 0.70, 95% confidence interval [CI]: 0.52-0.94, P = 0.02). There was a tendency for reduced MACE following initial CCTA strategy, but not for risk of all-cause mortality. Compared with functional testing, the CCTA strategy increased use of invasive coronary angiography (RR: 1.53, 95% CI: 1.12-2.09, P = 0.007) and coronary revascularization (RR: 1.49, 95% CI: 1.11-2.00, P = 0.007).

CONCLUSIONS

Anatomical testing with CCTA as the initial noninvasive diagnostic modality in patients with suspected CAD resulted in lower risk of nonfatal MI than usual care with functional testing, at the expense of more frequent use of invasive procedures.

Age- and sex-based resource utilisation and costs in patients with acute chest pain undergoing cardiac CT angiography: pooled evidence from ROMICAT II and ACRIN-PA trials

OBJECTIVES

To determine resource utilisation according to age and gender-specific subgroups in two large randomized diagnostic trials.

METHODS

We pooled patient-specific data from ACRIN-PA 4005 and ROMICAT II that enrolled subjects with acute chest pain at 14 US sites. Subjects were randomized between a standard work-up and a pathway utilizing cardiac computed tomography angiography (CCTA) and followed for the occurrence of acute coronary syndrome (ACS) and resource utilisation during index hospitalisation and 1-month follow-up. Study endpoints included diagnostic accuracy of CCTA for the detection of ACS as well as resource utilisation.

RESULTS

Among 1240 patients who underwent CCTA, negative predictive value of CCTA to rule out ACS remained very high (≥99.4%). The proportion of patients undergoing additional diagnostic testing and cost increased with age for both sexes (p < 0.001), and was higher in men as compared to women older than 60 years (43.1% vs. 23.4% and $4559 ± 3382 vs. $3179 ± 2562, p < 0.01; respectively). Cost to rule out ACS was higher in men (p < 0.001) and significantly higher for patients older than 60 years ($2860-5935 in men, p < 0.001).

CONCLUSIONS

CCTA strategy in patients with acute chest pain results in varying resource utilisation according to age and gender-specific subgroups, mandating improved selection for advanced imaging.

KEY POINTS

• In this analysis, CAD and ACS increased with age and male gender. • CCTA in patients with acute chest pain results in varying resource utilisation. • Significant increase of diagnostic testing and cost with age for both sexes. • Cost to rule out ACS is higher in men and patients >60 years. • Improved selection of subjects for cardiac CTA result in more resource-driven implementation.

Acute chest pain evaluation using coronary computed tomography angiography compared with standard of care: a meta-analysis of randomised clinical trials

Objective

Coronary CT angiography (CCTA) has certain advantages compared with stress testing including greater accuracy in identifying obstructive coronary disease. The aim of the study was to perform a systematical review and meta-analysis comparing CCTA with other standard-of-care (SOC) approaches in evaluation of patients with acute chest pain.

Methods

Electronic databases were systematically searched to identify randomised clinical trials of patients with acute chest pain comparing CCTA with SOC approaches. We examined the following end points: mortality, major adverse cardiac events (MACE), myocardial infarction (MI), invasive coronary angiography (ICA) and revascularisation. Pooled risk ratios (RR) and their 95% CIs were calculated using random-effects models.

Results

Ten trials with 6285 patients were included. The trials used different definitions and implementation for SOC but all used physiologic testing. The clinical follow-up ranged from 1 to 19 months. There were no significant differences in all-cause mortality (RR 0.48, 95% CI 0.17 to 1.36, p=0.17), MI (RR 0.82, 95% CI 0.49 to 1.39, p=0.47) or MACE (RR 0.98, 95% CI 0.67 to 1.43, p=0.92) between the groups. However, significantly higher rates of ICA (RR 1.32, 95% CI 1.07 to 1.63, p=0.01) and revascularisation (RR 1.77, 95% CI 1.35 to 2.31, p<0.0001) were observed in the CCTA arm.

Conclusions

Compared with other SOC approaches use of CCTA is associated with similar major adverse cardiac events but higher rates of revascularisation in patients with acute chest pain.

Comparative effectiveness of coronary CT angiography vs stress cardiac imaging in patients following hospital admission for chest pain work-up: The Prospective First Evaluation in Chest Pain (PERFECT) Trial

BACKGROUND

Because the frequency of cardiac event rates is low among chest pain patients following either performance of coronary CT angiography (CCTA) or stress testing, there is a need to better assess how these tests influence the central management decisions that follow from cardiac testing. The present study was performed to assess the relative impact of CCTA vs stress testing on medical therapies and downstream resource utilization among patients admitted for the work-up of chest pain.

METHODS

The admitted patients were randomized in a 1:1 ratio to either cardiac imaging stress test or CCTA. Primary outcomes were time to discharge, change in medication usage, and frequency of downstream testing, cardiac interventions, and cardiovascular re-hospitalizations. We randomized 411 patients, 205 to stress testing, and 206 to CCTA.

RESULTS

There were no differences in time to discharge or initiation of new cardiac medications at discharge. At 1 year follow-up, there was no difference in the number of patients who underwent cardiovascular downstream tests in the CCTA vs stress test patients (21% vs 15%, P = .1) or cardiovascular hospitalizations (14% vs 16%, P = .5). However, there was a higher frequency of invasive angiography in the CCTA group (11% vs 2%, P = .001) and percutaneous coronary interventions (6% vs 0%, P < .001).

CONCLUSIONS

Randomization of hospitalized patients admitted for chest pain work-up to either CCTA or to stress testing resulted in similar discharge times, change in medical therapies at discharge, frequency of downstream noninvasive testing, and repeat hospitalizations. However, a higher frequency of invasive coronary angiography and revascularization procedures were performed in the CCTA arm. (ClinicalTrials.gov number, NCT01604655.).

High-Pitch Coronary CT Angiography at 70 kVp Adopting a Protocol of Low Injection Speed and Low Volume of Contrast Medium

Objective

To evaluate the feasibility and image quality (IQ) of prospectively high-pitch coronary CT angiography (CCTA) with low contrast medium injection rate at 70 kVp.

Materials and Methods

One hundred and four patients with suspected coronary artery disease (body mass index < 26 kg/m², sinus rhythm and heart rate < 70 beats/min) were prospectively enrolled and randomly divided into two groups. In group A and group B, 28 mL and 40 mL of 370 mgI/mL iodinated contrast media was administrated at a flow rate of 3.5 and 5 mL/s, respectively. CT values, noise, signal-to-noise ratio, contrast-to-noise ratio (CNR) of the proximal segments of coronary arteries and subjective IQ were evaluated.

Results

The CT values and noise in group A were significantly lower than those in group B (434–485 Hounsfield units [HU] vs. 772–851 HU, all p < 0.001; 17.8–22.3 vs. 23.3–26.4, all p < 0.005). The CNRs of the right coronary artery and left main artery showed no statistical difference between the two groups (42.1 ± 13.8 vs. 36.8 ± 16.0, p = 0.074; 38.7 ± 10.6 vs. 38.1 ± 17.0, p = 0.819). No statistical difference was observed between the two groups in IQ scores (3.04 ± 0.75 vs. 3.0 ± 0.79, p = 0.526) and diagnostic ratio (96.1% [50/52] vs. 94.2% [49/52], p = 0.647).

Conclusion

Prospective high-pitch CCTA at 70 kVp with 28 mL of contrast media and injection rate of 3.5 mL/s could provide diagnostic IQ for normal-weight patients with heart rate of < 70 beats/min.

The clinical utility of new cardiac imaging modalities in Australasian clinical practice

Cardiac imaging is a rapidly evolving field, with improvements in the diagnostic capabilities of non-invasive cardiac assessment. We review the two main emerging technologies in cardiac imaging: computed tomography coronary angiography (CTCA) to evaluate chest symptoms and to exclude coronary artery disease; and cardiovascular magnetic resonance (CMR) for evaluating cardiac morphology, function and presence of scar. CTCA is an excellent "rule out" test, with a negative predictive value approaching 100%. Radiation exposure is no longer a concern for CTCA, with doses routinely < 5 mSv, and as low as < 1 mSv in selected patients. CTCA is useful for excluding coronary artery disease, investigating the anatomy of coronary anomalies or fistulae, and for the patency of coronary bypass grafts. CMR is the reference test for the accurate quantitation of left ventricular and right ventricular size and function. CMR has no ionising radiation, making it particularly suitable for patients with heart failure or congenital heart disease who require longitudinal follow-up. Evaluation of cardiomyopathies (hypertrophic, ischaemic, infiltrative, myocarditis, iron overload or idiopathic) is a unique strength of CMR. Stress perfusion CMR has a strong evidence base and improved spatial and temporal resolution compared with nuclear single-photon emission computed tomography.