Prevalence of first-pass myocardial perfusion defects detected by contrast-enhanced dual-source CT in patients with non-ST segment elevation acute coronary syndromes. Eur Radiol. 2010;20:1607-1614. [PMID: 20155270 DOI: 10.1007/s00330-010-1725-7]

Case report of non-ST-segment elevation myocardial infarction diagnosed in spectral detector-based computed tomography performed for the diagnosis of acute pulmonary embolism

Background

Contrast-enhanced spectral detector-based computed tomography (SDCT) allows for the comprehensive and retrospective analysis. We report a case of pulmonary thromboembolism (PE) accompanied by non-ST-segment elevation myocardial infarction (NSTEMI) diagnosed by SDCT.

Case summary

A 72-year-old man with diabetes mellitus, hypertension, and prostate cancer suddenly developed chest and back pain and had difficulty in breathing at rest. Electrocardiography showed a right bundle branch block without significant ST-segment change. The initial serum troponin I level was 0.05 ng/mL, and the d-dimer level was 14.7 μg/mL. Spectral detector-based computed tomography showed bilateral scattered PE. After admission, his chest pain persisted, and the serum troponin I level 3 h after admission was elevated to 0.90 ng/mL. Reconstruction of SDCT images showed a perfusion defect of the posterolateral left ventricle myocardium. A coronary angiogram showed total occlusion of the obtuse marginal branch (OM); percutaneous coronary intervention was performed. Furthermore, we administered him with oral anticoagulants (OACs) for PE. Spectral detector-based computed tomography tests performed 6 months after the treatment was initiated, until when the dual antiplatelet therapy and OAC therapy were continued, showed improvement in perfusion defects of both pulmonary fields and the myocardium. His treatment was deescalated to single antiplatelet therapy and OAC, and the patient has had a good course.

Discussion

Non-ST-segment elevation myocardial infarction is sometimes difficult to diagnose accurately, especially in the hyper-acute phase or in the OM branch. The reconstruction of spectral images from enhanced SDCT was helpful to diagnose this unique combination of PE and NSTEMI and may be useful for evaluating therapeutic effects in such patients.

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.

Infarct characterization using CT

Myocardial infarction (MI) is a major cause of death and disability worldwide. The incidence is not expected to diminish, despite better prevention, diagnosis and treatment, because of the ageing population in industrialized countries and unhealthy lifestyles in developing countries. Nowadays it is highly requested an imaging tool able to evaluate MI and viability. Technology improvements determined an expansion of clinical indications from coronary plaque evaluation to functional applications (perfusion, ischemia and viability after MI) integrating additional phases and information in the mainstream examination. Cardiac computed tomography (CCT) and cardiac MR (CMR) employ different contrast media, but may characterize MI with overlapping imaging findings due to the similar kinetics and tissue distribution of gadolinium and iodinated contrast media. CCT may detect first-pass perfusion defects, dynamic perfusion after pharmacological stress, and delayed enhancement (DE) of non-viable territories.

Highly sensitive troponin and coronary computed tomography angiography in the evaluation of suspected acute coronary syndrome in the emergency department

The evaluation of patients presenting to the emergency department with suspected acute coronary syndrome (ACS) remains a clinical challenge. The traditional assessment includes clinical risk assessment based on cardiovascular risk factors with serial electrocardiograms and cardiac troponin measurements, often followed by advanced cardiac testing as inpatient or outpatient (i.e. stress testing, imaging). Despite this costly and lengthy work-up, there is a non-negligible rate of missed ACS with an increased risk of death. There is a clinical need for diagnostic strategies that will lead to rapid and reliable triage of patients with suspected ACS. We provide an overview of the evidence for the role of highly sensitive troponin (hsTn) in the rapid and efficient evaluation of suspected ACS. Results of recent research studies have led to the introduction of hsTn with rapid rule-in and rule-out protocols into the guidelines. Highly sensitive troponin increases the sensitivity for the detection of myocardial infarction and decreases time to diagnosis; however, it may decrease the specificity, especially when used as a dichotomous variable, rather than continuous variable as recommended by guidelines; this may increase clinician uncertainty. We summarize the evidence for the use of coronary computed tomography angiography (CTA) as the rapid diagnostic tool in this population when used with conventional troponin assays. Coronary CTA significantly decreases time to diagnosis and discharge in patients with suspected ACS, while being safe. However, it may lead to increase in invasive procedures and includes radiation exposure. Finally, we outline the opportunities for the combined use of hsTn and coronary CTA that may result in increased efficiency, decreased need for imaging, lower cost, and decreased radiation dose.

Early resting myocardial computed tomography perfusion for the detection of acute coronary syndrome in patients with coronary artery disease

BACKGROUND

Acute rest single-photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) has high predictive value for acute coronary syndrome (ACS) in emergency department patients. Prior studies have shown excellent agreement between rest/stress computed tomography perfusion (CTP) and SPECT-MPI, but the value of resting CTP (rCTP) in acute chest pain triage remains unclear. We sought to determine the diagnostic accuracy of early rCTP, incremental value beyond obstructive coronary artery disease (CAD; ≥50% stenosis), and compared early rCTP to late stress SPECT-MPI in patients with CAD presenting with suspicion of ACS to the emergency department.

METHODS AND RESULTS

In this prespecified subanalysis of 183 patients (58.1±10.2 years; 33% women), we included patients with any CAD by coronary computed tomography angiography (CCTA) from Rule Out Myocardial Infarction Using Computer-Assisted Tomography I. rCTP was assessed semiquantitatively, blinded to CAD interpretation. Overall, 31 had ACS and 48 had abnormal rCTP. Sensitivity and specificity of rCTP for ACS were 48% (95% confidence interval [CI], 30%-67%) and 78% (95% CI, 71%-85%), respectively. rCTP predicted ACS (adjusted odds ratio, 3.40 [95% CI, 1.37-8.42]; P=0.008) independently of obstructive CAD, and sensitivity for ACS increased from 77% (95% CI, 59%-90%) for obstructive CAD to 90% (95% CI, 74%-98%) with addition of rCTP (P=0.05). In a subgroup undergoing late rest/stress SPECT-MPI (n=81), CCTA/rCTP had noninferior discriminatory value to CCTA/SPECT-MPI (area under the curve, 0.88 versus 0.90; P=0.64) using a noninferiority margin of 10%.

CONCLUSIONS

Early rCTP provides incremental value beyond obstructive CAD to detect ACS. CCTA/rCTP is noninferior to CCTA/SPECT-MPI to discriminate ACS and presents an attractive alternative to triage patients presenting with acute chest pain.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00990262.

Cardiac computed tomography in patients with acute chest pain

The efficient and reliable evaluation of patients with acute chest pain is one of the most challenging tasks in the emergency department. Coronary computed tomography (CT) angiography may play a major role, since it permits ruling out coronary artery disease with high accuracy if performed with expertise in properly selected and prepared patients. Several randomized trials have established early cardiac CT as a viable safe and potentially more efficient alternative to functional testing in the evaluation of acute chest pain. Ongoing investigations explore whether advanced anatomic and functional assessments such as high-risk coronary plaque, resting myocardial perfusion, and left ventricular function, or the simulation of the fractional coronary flow reserve will add information to the anatomic assessment for stenosis, which would allow expanding the benefits of cardiac CT from triage to treatment decisions. Especially, the combination of high-sensitive troponins and coronary computed tomography angiography may play a valuable role in future strategies for the management of patients presenting with acute chest pain.

Comparison of quantitative atherosclerotic plaque burden from coronary CT angiography in patients with first acute coronary syndrome and stable coronary artery disease

BACKGROUND

Coronary CTA allows characterization of non-calcified and calcified plaque and identification of high-risk plaque features.

OBJECTIVE

We aimed to quantitatively characterize and compare coronary plaque burden from CTA in patients with a first acute coronary syndrome (ACS) and controls with stable coronary artery disease.

MATERIALS AND METHODS

We retrospectively analyzed consecutive patients with non-ST-segment elevation myocardial infarction (NSTEMI) or unstable angina with a first ACS, who underwent CTA as part of their initial workup before invasive coronary angiography and age- and gender-matched controls with stable chest pain; controls also underwent CTA with subsequent invasive angiography (total n = 28). Culprit arteries were identified in ACS patients. Coronary arteries were analyzed by automated software to quantify calcified plaque (CP), noncalcified plaque (NCP), and low-density NCP (LD-NCP, attenuation <30 Hounsfield units) volumes, and corresponding burden (plaque volume × 100%/vessel volume), stenosis, remodeling index, contrast density difference (maximum percent difference in attenuation/cross-sectional area from proximal cross-section), and plaque length.

RESULTS

ACS patients had fewer lesions (median, 1), with higher total NCP and LD-NCP burdens (NCP: 57.4% vs 41.5%; LD-NCP: 12.5% vs 8%; P ≤ .04), higher maximal stenoses (85.6% vs 53.0%; P = .003) and contrast density differences (46.1 vs 16.3%; P < .006). Per-patient CP burden was not different between ACS and controls. NCP and LD-NCP plaque burden was higher in culprit vs nonculprit arteries (NCP: 57.8% vs 9.5%; LD-NCP: 8.4% vs 0.6%; P ≤ .0003); CP was not significantly different. Culprit arteries had increased plaque lengths, remodeling indices, stenoses, and contrast density differences (46.1% vs 10.9%; P ≤ .001).

CONCLUSION

Noninvasive quantitative coronary artery analysis identified several differences for ACS, both on per-patient and per-vessel basis, including increased NCP, LD-NCP burden, and contrast density difference.

Role of cardiovascular magnetic resonance in assessment of acute coronary syndrome

Cardiovascular disease (CVD) is the leading cause of death in the western world and is becoming more important in the developing world. Recently, advances in monitoring, revascularisation and pharmacotherapy have resulted in a reduction in mortality. However, although mortality rates have declined, the burden of disease remains large resulting in high direct and indirect healthcare costs related to CVDs. In Australia, acute coronary syndrome (ACS) accounts for more than 300000 years of life lost due to premature death and a total cost exceeding eight billion dollars annually. It is also the main contributor towards the discrepancy in life expectancy between indigenous and non-indigenous Australians. The high prevalence of CVD along with its associated cost urgently requires a reliable but non-invasive and cost-effective imaging modality. The imaging modality of choice should be able to accelerate the diagnosis of ACS, aid in the risk stratification of de novo coronary artery disease and avail incremental information of prognostic value such as viability which cardiovascular magnetic resonance (CMR) allows. Despite its manifold benefits, there are limitations to its wider use in routine clinical assessment and more studies are required into assessing its cost-effectiveness. It is hoped that with greater development in the technology and imaging protocols, CMR could be made less cumbersome, its imaging protocols less lengthy, the technology more inexpensive and easily applied in routine clinical practice.

Role of non-electrocardiogram-gated contrast-enhanced computed tomography in the diagnosis of acute coronary syndrome

Non-electrocardiogram-gated contrast-enhanced computed tomography (non-ECG-gated CT) is available in most hospitals where patients with chest and/or back pain are admitted to the emergency department. Although it has been established as the initial diagnostic imaging modality for acute aortic dissection (AAD) and pulmonary thromboembolism (PE), its diagnostic ability for acute coronary syndrome (ACS) in the emergency department has not been elucidated. We retrospectively investigated 154 consecutive patients who required non-ECG-gated CT to differentiate AAD and PE in the emergency department, but had no evidence of them on CT. Furthermore, a subanalysis was performed in the patients who were subsequently suspected of ACS and underwent emergent invasive coronary angiography followed by CT. We evaluated left ventricular enhancement to detect myocardial perfusion deficit by calculating Hounsfield units, and the results were compared with ultimate diagnoses and angiography findings. A perfusion deficit was detected in 43 patients, among whom 26 were ultimately diagnosed with acute myocardial infarction (AMI); 24 patients required emergent revascularization. The subanalysis indicated that perfusion abnormalities corresponded with the territory of the culprit artery in all except one patient. In the remaining 111 patients without perfusion deficit, only two required emergent revascularization, and their levels of creatine kinase MB were not elevated. The sensitivity, specificity, and positive and negative predictive values of non-ECG-gated CT in predicting AMI/emergent revascularization were 93 %, 87 %, 61 %, and 98 %/92 %, 85 %, 56 %, and 98 %, respectively. Non-ECG-gated CT facilitates the diagnosis of ACS and the decision on emergent catheterization, providing information on the ischemic myocardial area by detection of a localized decrease in left ventricular enhancement.

Myocardial perfusion imaging with cardiac computed tomography: state of the art

Cardiac computed tomography (CCT) has become an important tool for the anatomic assessment of patients with suspected coronary disease. Its diagnostic accuracy for detecting the presence of underlying coronary artery disease and ability to risk stratify patients are well documented. However, the role of CCT for the physiologic assessment of myocardial perfusion during resting and stress conditions is only now emerging. With the addition of myocardial perfusion imaging to coronary imaging, CCT has the potential to assess both coronary anatomy and its functional significance with a single non-invasive test. In this review, we discuss the current state of CCT myocardial perfusion imaging for the detection of myocardial ischemia and myocardial infarction and examine its complementary role to CCT coronary imaging.

Left ventricular thrombus attenuation characterization in cardiac computed tomography angiography

BACKGROUND

Because of their similar visual appearance, differentiation of left ventricular thrombotic material and myocardial wall can be difficult in contrast-enhanced coronary computed tomography (CT) angiography.

OBJECTIVE

We identified typical thrombi attenuation of left ventricular thrombi with the use of CT measurement.

METHODS

Over a time period of 6 years, we retrospectively identified 31 patients who showed a left ventricular thrombus in CT angiography datasets. Patients underwent routine contrast cardiac CT to investigate coronary artery disease. CT attenuation of each thrombus was assessed in the 4-chamber view. CT densities were also determined in the ascending aorta, left ventricle, and myocardial wall both in the mid-septal and mid-lateral segments. The mean CT attenuation of thrombi and the difference between attenuation in thrombi, left ventricular cavity, and myocardial wall were determined. The ratio of attenuation values in thrombus versus aorta and myocardium versus aorta were also determined.

RESULTS

Mean (±SD) CT attenuation of all left ventricular thrombi in 31 patients was 43.2 ± 15.3 HU (range, 25-80 HU). Mean CT densities of septal and lateral myocardial wall were 102.9 ± 23.1 HU (range, 63-155 HU) and 99.3 ± 28.7 HU (range, 72-191 HU), respectively, and were thus significantly higher than the CT attenuation of thrombi (P < 0.001). A threshold of 65 HU yielded a sensitivity, specificity, and positive and negative predictive values of 94%, 97%, 94%, and 97%, respectively, to differentiate thrombus from the myocardial wall. The mean ratio between CT attenuation of thrombus and CT attenuation within the ascending aorta was 0.11 ± 0.05 (range, 0.04-0.23), which was significantly lower compared with the mean ratio between CT attenuation of the myocardial wall and the CT attenuation within the ascending aorta.

CONCLUSION

CT attenuation within left ventricular thrombi was significantly lower than myocardial attenuation in CT angiography datasets. Assessment of CT attenuation may contribute to the differentiation of thrombi.

Non-invasive imaging in acute chest pain syndromes

This review has the purpose of informing the reader about the current use of imaging techniques in patients presenting with acute chest pain to the emergency department. We will focus on three aspects of managing the patient with acute chest pain: Imaging to increase the number of correct diagnoses in the acute situation; Imaging to rule out other than coronary causes of chest pain; Use of imaging for risk stratification once myocardial infarction has been ruled out in the CPU. Special emphasis is given to how these management aspects are discussed in current guidelines on the management of patients with acute chest pain or acute coronary syndrome.

Computed tomography imaging in myocardial infarction

Over recent decades, noninvasive imaging has become well established in the diagnostic work-up of patients suffering from myocardial infarction. It provides insights into the individual patient's prognosis and guides therapeutic decisions. MRI has long been considered the standard of reference in the noninvasive imaging of myocardial infarction. Only recently have different multidetector-row spiral computed tomography (MDCT) techniques successfully been evaluated for the visualization of myocardial infarction. This article describes different concepts of cardiac MDCT imaging in acute and chronic myocardial infarction. MDCT assessment of myocardial edema, myocardial perfusion and delayed myocardial contrast enhancement are introduced, with the latter evolving as key concept of viability imaging by means of MDCT. The current status of MDCT in the diagnostic work-up of myocardial infarction is reviewed.

Diagnostic performance of computed tomography angiography for differentiating ischemic vs nonischemic cardiomyopathy

BACKGROUND

Although the use of computed tomography angiography (CTA) is considered "appropriate" to distinguish ischemic vs nonischemic etiology in patients with cardiomyopathy under the current clinical practice guideline, the evidence to support this has not been evaluated in larger scale studies. Thus, we conducted a meta-analysis of available studies published by October 2010 to address this question.

METHODS

Studies evaluating the diagnostic accuracy of CTA versus invasive coronary angiography (as the gold standard) for significant coronary artery disease (CAD) detection (ischemic cardiomyopathy) in patients with no known history of CAD with significantly depressed left ventricular function (ejection fraction; EF < 35%) were selected for the meta-analysis. Sensitivity, specificity, positive, and negative likelihood ratios were calculated on per patient and per segment basis using random effects model (DerSimonian-Laird Method) for computing summary estimates and receiver operator curve (ROC) analysis for evaluating overall diagnostic accuracy.

RESULTS

Six studies comprising 452 patients met the selection criteria for the meta-analysis. The pooled patient population was 62 ± 3 years old, with 29% females, 16% diabetics, and 43% with a history of hypertension. Mean EF was 32% ± 1%. The pooled summary estimate of sensitivity of CTA for diagnosis of ischemic cardiomyopathy was 98% [95% confidence interval (CI); 94% to 99%] and specificity was 97% (CI 94% to 98%), yielding a negative likelihood ratio of 0.06 (CI 0.02 to 0.13) and positive likelihood ratio of 20.85 (CI 12 to 36). There was no significant heterogeneity between studies for these estimates. The receiver operator curve analysis showed a robust discriminate diagnostic accuracy of ischemic etiology with an area under curve of 0.99 (P < .00001).

CONCLUSION

CTA appears as a clinically applicable accurate diagnostic modality to exclude ischemic etiology in patients with cardiomyopathy of undetermined cause and this further supports the appropriateness of the use of CTA to determine the cause of new onset cardiomyopathy of unknown etiology.

Myocardial perfusion imaging and infarct characterization using multidetector cardiac computed tomography

Until recently, computed tomography coronary angiography was restricted to the anatomical assessment of coronary stenosis, whereas the functional significance of coronary lesions remained outside of its scope. Nevertheless, the kinetics of iodinated contrast is similar to gadolinium-diethylenetriamine pentaacetic acid used in contrast-enhanced magnetic resonance imaging, allowing assessment of myocardial perfusion and viability by cardiac computed tomography.