Emergency cardiac CT for suspected acute coronary syndrome: qualitative and quantitative assessment of coronary, pulmonary, and aortic image quality

Appropriateness criteria for the use of cardiac computed tomography, SIC-SIRM part 2: acute chest pain evaluation; stent and coronary artery bypass graft patency evaluation; planning of coronary revascularization and transcatheter valve procedures; cardiomyopathies, electrophysiological applications, cardiac masses, cardio-oncology and pericardial diseases evaluation

In the past 20 years, cardiac computed tomography (CCT) has become a pivotal technique for the noninvasive diagnostic workup of coronary and cardiac diseases. Continuous technical and methodological improvements, combined with fast growing scientific evidence, have progressively expanded the clinical role of CCT. Randomized clinical trials documented the value of CCT in increasing the cost-effectiveness of the management of patients with acute chest pain presenting in the emergency department, also during the pandemic. Beyond the evaluation of stents and surgical graft patency, the anatomical and functional coronary imaging have the potential to guide treatment decision-making and planning for complex left main and three-vessel coronary disease. Furthermore, there has been an increasing demand to use CCT for preinterventional planning in minimally invasive procedures, such as transcatheter valve implantation and mitral valve repair. Yet, the use of CCT as a roadmap for tailored electrophysiological procedures has gained increasing importance to assure maximum success. In the meantime, innovations and advanced postprocessing tools have generated new potential applications of CCT from the simple coronary anatomy to the complete assessment of structural, functional and pathophysiological biomarkers of cardiac disease. In this complex and revolutionary scenario, it is urgently needed to provide an updated guide for the appropriate use of CCT in different clinical settings. This manuscript, endorsed by the Italian Society of Cardiology (SIC) and the Italian Society of Medical and Interventional Radiology (SIRM), represents the second of two consensus documents collecting the expert opinion of cardiologists and radiologists about current appropriate use of CCT.

Computed Tomographic Angiography for Risk Stratification in Patients with Acute Chest Pain - The Triple Rule-out Concept in the Emergency Department

BACKGROUND

Acute chest pain is one of the most common reasons for Emergency Department (ED) visits and hospital admissions. As this could represent the first symptom of a lifethreatening condition, urgent identification of the etiology of chest pain is of utmost importance in emergency settings. Such high-risk conditions that can present with acute chest pain in the ED include Acute Coronary Syndromes (ACS), Pulmonary Embolisms (PE) and Acute Aortic Syndromes (AAS).

DISCUSSION

The concept of Triple Rule-out Computed Tomographic Angiography (TRO-CTA) for patients presenting with acute chest pain in the ED is based on the use of coronary computed tomographic angiography as a single imaging technique, able to diagnose or exclude three lifethreatening conditions in one single step: ACS, AAS and PE. TRO-CTA protocols have been proved to be efficient in the ED for diagnosis or exclusion of life-threatening conditions and for differentiation between various etiologies of chest pain, and application of the TRO-CTA protocol in the ED for acute chest pain of uncertain etiology has been shown to improve the further clinical evaluation and outcomes of these patients.

CONCLUSION

This review aims to summarize the main indications and techniques used in TRO protocols in EDs, and the role of TRO-CTA protocols in risk stratification of patients with acute chest pain.

Bursting pressure of triple-lumen central venous catheters under static and dynamic loads

INTRODUCTION

Central venous catheter (CVC) access is commonplace in intensive care units. Patients undergoing computed tomographic angiography require injection of contrast at high flow rates (4.5 mL/s), often CVC access is not used due to safety concerns. The CVC might rupture at high flow rates, resulting in CVC fragmentation and embolization or contrast extravasation.The objective of this study is to determine the pressure required to burst a CVC under static load and compare this to the pressure generated by injection of contrast at high flow rates (dynamic load) through the distal (16-g) lumen of a triple-lumen CVC.

METHODS

We gathered 16-cm long triple-lumen CVCs (n = 14) from patients with an average dwell time of 5.2 days (±2.7 days). Half the CVCs (n = 7) were subjected to static testing, where the distal lumen was occluded with the guidewire and super glue at the distal end of the catheter. The CVC was then placed into a 10-cm deep water bath at 37°C to simulate in vivo conditions and water was injected until catheter rupture. Dynamic pressure testing was done with the remaining catheters, with radio-contrast injected through the unoccluded distal lumen at flow rates of 4.5 mL/s, then 7 mL/s. Pressures were recorded throughout injection.

RESULTS

During static testing, 6/7 CVCs burst at the distal lumen where the glue was applied, the remaining CVC burst proximal to the hub. PSI at burst during static testing was 184.2 PSI (95% confidence interval [CI] 174.3-194.1 PSI). During dynamic testing the mean peak pressures at 7 mL/s was 81.1 PSI (95% CI 73-89.2 PSI). At 4.5 mL/s the mean peak pressure was 47.9 PSI (95% CI 42.9-52.9 PSI).

CONCLUSIONS

No CVCs failed under dynamic loading with injection of contrast at flow rates (4.5 and 7 mL/s) high enough to support computed tomographic angiography. This suggests 16-cm triple-lumen CVCs can be used safely.

Effectiveness of Adaptive Statistical Iterative Reconstruction for 64-Slice Dual-Energy Computed Tomography Pulmonary Angiography in Patients With a Reduced Iodine Load: Comparison With Standard Computed Tomography Pulmonary Angiography

OBJECTIVE

The aim of the study was to assess the effectiveness of the adaptive statistical iterative reconstruction (ASIR) for dual-energy computed tomography pulmonary angiography (DE-CTPA) with a reduced iodine load.

MATERIALS AND METHODS

One hundred forty patients referred for chest CT were randomly divided into a DE-CTPA group with a reduced iodine load or a standard CTPA group. Quantitative and qualitative image qualities of virtual monochromatic spectral (VMS) images with filtered back projection (VMS-FBP) and those with 50% ASIR (VMS-ASIR) in the DE-CTPA group were compared. Image qualities of VMS-ASIR images in the DE-CTPA group and ASIR images in the standard CTPA group were also compared.

RESULTS

All quantitative and qualitative indices, except attenuation value of pulmonary artery in the VMS-ASIR subgroup, were superior to those in the VMS-FBP subgroup (all P < 0.001). Noise and signal-to-noise ratio of VMS-ASIR images were superior to those of ASIR images in the standard CTPA group (P < 0.001 and P = 0.007, respectively). Regarding qualitative indices, noise was significantly lower in VMS-ASIR images of the DE-CTPA group than in ASIR images of the standard CTPA group (P = 0.001).

CONCLUSIONS

The ASIR technique tends to improve the image quality of VMS imaging. Dual-energy computed tomography pulmonary angiography with ASIR can reduce contrast medium volume and produce images of comparable quality with those of standard CTPA.

Contrast material and radiation dose reduction strategy for triple-rule-out cardiac CT angiography: feasibility study of non-ECG-gated low kVp scan of the whole chest following coronary CT angiography

BACKGROUND

Dedicated coronary computed tomography (CT) scan has been proven to be an accurate diagnostic modality in evaluating coronary artery disease. A second phase scan starting immediately after the coronary CT scan might enable visualization of the different vascular territories of the entire chest.

PURPOSE

To investigate the feasibility of a contrast material and radiation dose reduction triple-rule-out (TRO) CT angiography (CTA) protocol with serial non-ECG-gated low kVp scan of the whole chest, which utilizes a recirculated contrast agent.

MATERIAL AND METHODS

Thirty patients were scanned with the new TRO-CTA protocol; after the coronary scan with retrospective ECG-gating, non-ECG-gated whole-chest CTA was performed at 80 kVp to evaluate aortic arch (AAr) and pulmonary trunk (PT). Another 30 patients were scanned by our conventional TRO-CTA protocol at 120 kVp with retrospective ECG-gating. We compared the estimated effective dose (ED), contrast material (CM) dose, contrast-to-noise ratio (CNR) of the ascending aorta (AAo), and the rate of patients who could achieve adequate attenuation of the AAr and PT between the two protocols.

RESULTS

The total ED of the new TRO-CTA protocol was 29.6% lower than that of the conventional protocol (P < 0.01). The amount of CM used for the new TRO-CTA protocol was significantly lower than in the conventional protocol (60.1 ± 9.6 mL vs. 91.8 ± 22.6 mL, P < 0.01). The CNR of the AAo was 30.2% higher with the new TRO-CTA protocol than with the conventional protocol (P < 0.01). There was no significant difference in the success rate of adequate attenuation of the AAr and PT between the two protocols (P > 0.05).

CONCLUSION

The new TRO-CTA protocol can reduce the total dose of radiation and the contrast dose and yield adequate vascular enhancement compared with the conventional protocol.

Triple rule-out computed tomographic angiography for chest pain: a diagnostic systematic review and meta-analysis

OBJECTIVES

The objective was to compare the image quality, diagnostic accuracy, radiation exposure, and contrast volume of "triple rule-out" (TRO) computed tomography (CT) to other diagnostic modalities commonly used to evaluate patients with nontraumatic chest pain (dedicated coronary, pulmonary embolism [PE], and aortic dissection CT; invasive coronary angiography; and nuclear stress testing).

METHODS

Four electronic databases were searched, along with reference lists and contacted content experts, for relevant studies from inception until October 2012. Eligible studies enrolled patients with nontraumatic chest pain, shortness of breath, suspected acute coronary syndrome (ACS), PE, or aortic dissection; used at least 64-slice CT technology; and compared TRO CT to another diagnostic modality.

RESULTS

Eleven studies enrolling 3,539 patients (791 TRO and 2,748 non-TRO) were included (one randomized controlled trial and 10 observational). There was no significant difference in image quality between TRO and dedicated CT scans. TRO CT had the following pooled diagnostic accuracy estimates for coronary artery disease: sensitivity of 94.3% (95% confidence interval [CI] = 89.1% to 97.5%), specificity of 97.4% (95% CI = 96.1% to 98.4%), positive likelihood ratio (LR+) of 17.71 (95% CI = 3.92 to 79.96), and negative likelihood ratio (LR-) of 0.08 (95% CI = 0.02 to 0.27). There were insufficient numbers of patients with PE or aortic dissection to generate diagnostic accuracy estimates for these conditions. Use of TRO CT involved greater radiation exposure (mean difference [MD] = 4.84 mSv, 95% CI = 1.65 to 8.04 mSv) and contrast exposure (MD = 38.0 mL, 95% CI = 28.1 to 48.0 mL) compared to non-TRO CT patients.

CONCLUSIONS

Triple rule-out CT is highly accurate for detecting coronary artery disease. Given the low (<1%) prevalence of PE and aortic dissection in the included studies, and the increased radiation and contrast exposure, there are insufficient data to recommend use of TRO CT in the diagnosis of these conditions.

Evaluation of acute chest pain in the emergency department: "triple rule-out" computed tomography angiography

Triage of patients with acute, potentially life-threatening chest pain is one of the most important issues currently facing physicians in the emergency department. Appropriate evaluation of these patients begins with a skilled assessment of the individual patient's presenting symptoms and a careful review of his or her history and physical examination, often followed by serial recording of electrocardiograms and measurement of serum biochemical markers such as troponin and d-dimer. Stress testing, often accompanied by rest and stress myocardial perfusion imaging or echocardiography, and other diagnostic testing such as radionuclide lung scanning and invasive angiography may be required. A rapid, accurate, and cost-effective approach for the evaluation of emergency department patients with chest pain is needed. Development of newer generations of multidetector computed tomographic (MDCT) scanners, which are capable not only of performing high-quality noninvasive coronary angiography, but also concurrent aortic and pulmonary angiography, has led to increased use of MDCT for the so-called "triple rule out." MDCT is used for the detection of 3 of the most common life-threatening causes of chest pain-coronary artery disease, acute aortic syndrome, and pulmonary emboli. While triple rule-out protocol can be very useful and potentially cost effective when used appropriately, concern has risen regarding the overuse of this technology, which could expose patients to unnecessary radiation and iodinated contrast. The triple rule-out protocol is most appropriate for patients who present with acute chest pain, but are judged to have low to intermediate increased risk for acute coronary syndrome, and whose chest pain symptoms might also be attributed to acute pathologic conditions of the aorta or pulmonary arteries. MDCT should not be used as a routine screening procedure. Continued technical improvements in acquisition speed and spatial resolution of computed tomography images, and development of more efficient image reconstruction algorithms which reduce patient exposure to radiation and contrast, may result in increased popularity of MDCT for "triple rule-out."

Cardiac CT in the emergency department: convincing evidence, but cautious implementation

In clinical practice, assessment of chest pain patients presenting to the emergency department is difficult and the work-up can be lengthy and costly. There is growing evidence supporting the use of coronary computed tomography angiography (CTA) in early assessment of patients presenting with acute chest pain to the emergency department. CTA appears to be a faster and more accurate way to diagnosis or rule out coronary stenosis, leading to reduced hospital admissions, decreased time in the ED and lower costs. The focus of this article is to review the current literature of the use of Coronary CTA and "triple rule out" protocols in the emergency department setting and to provide a chest pain algorithm, showing how Coronary CTA can be implemented effectively in clinical practice. Potential pitfalls and requirements for implementation will also be discussed.

Clinical benefit of power-injectable port systems: a prospective observational study

OBJECTIVE

To prospectively evaluate the clinical benefit of a central venous port system, which is approved for contrast media injection during contrast enhanced computed tomography.

MATERIALS AND METHODS

At a university teaching hospital, 98 patients (59 female, 39 male; median age 61.7 years; range 23-83) had a power-injectable central venous port catheter system implanted. All implantations were performed under ultrasonographic and fluoroscopic guidance by interventional radiologists. Procedure related immediate (up to 24 h after implantation), early (<30 days after implantation) and late complications were documented. The frequency of port system use for contrast enhanced computed tomography scans was also considered. Any port capsule migration was assessed indirectly by determining the catheter tip position. The intended follow-up period was 180 days.

RESULTS

An overall complication rate of 0.69 for 1,000 catheter days in 78 evaluated ports was recorded (12 ports affected, 15.4%). During the observational period, 40 of 104 contrast enhanced computed tomography scans were performed utilizing the port for contrast media administration (38.5%). 30 catheter tip retractions of more than 3 cm were observed in 82 patients (36.6%). Overall, tip dislocations were statistically more frequent in the female subgroup.

CONCLUSION

The complication rate found in this study is comparable to those, which have been published for standard port systems. The utilization of the device for contrast media injection during contrast enhanced computed tomography scans should be increased. Finally, the port capsule has to be carefully positioned and fixed to prevent migration.

Triphasic contrast bolus for whole-chest ECG-gated 64-MDCT of patients with nonspecific chest pain: evaluation of arterial enhancement and streak artifact

OBJECTIVE

The purpose of this study was to evaluate the use of a triphasic contrast bolus for ECG-gated CT in the assessment of chest pain by measuring vascular luminal attenuation and determining the degree of contrast-related streak artifact.

MATERIALS AND METHODS

We reviewed the images from 44 ECG-gated CT examinations performed with a coronary contrast bolus modified for imaging of the entire chest. Luminal attenuation achieved with the resulting triphasic bolus was measured at specified vascular locations in the right side of the heart, pulmonary arteries, coronary arteries, and thoracic aorta. The occurrence of contrast-related streak artifact was recorded, and artifact severity was scored on a subjective 4-point scale.

RESULTS

The mean attenuation values in the pulmonary arteries (345.3 +/- 136.7 HU), coronary arteries (340.8 +/- 82.5 HU), and thoracic aorta (386.4 +/- 67.2 HU) were above a diagnostic threshold of 200 HU. Although there was no significant difference between the mean arterial values, the right-heart attenuation (281.6 +/- 121.8 HU) was significantly lower than the attenuation in the other two locations. On a location basis, 92.2% of the 1,972 arterial measurements were above the 200-HU threshold. Streak artifacts were found in 21 examinations (47.7%), and none was scored as severe. Statistical analysis revealed that the occurrence of streak artifact increased with higher right-heart attenuation.

CONCLUSION

In this series, a triphasic contrast bolus for ECG-gated whole-chest CT consistently achieved arterial attenuation above a diagnostic threshold in the pulmonary arteries, coronary arteries, and aorta. Right-heart attenuation was simultaneously reduced, which is important for decreasing the prevalence and severity of streak artifacts.

Quantitative image analysis for the detection of motion artefacts in coronary artery computed tomography

Multi detector-row CT (MDCT), the current preferred method for coronary artery disease assessment, is still affected by motion artefacts. To rule out motion artefacts, qualitative image analysis is usually performed. Our study aimed to develop a quantitative image analysis for motion artefacts detection as an added value to the qualitative analysis. An anthropomorphic moving heart phantom with adjustable heart-rate was scanned on 64-MDCT and dual-source-CT. A new software technique was developed which detected motion artefacts in the coronaries and also in the myocardium, where motion artefacts are more apparent; with direct association to the qualitative analysis. The new quantitative analysis managed to detect motion artefacts in phantom scans and relate them to artefact-induced vessel stenoses. Quantifying these artefacts at corresponding locations in the myocardium, artefact-induced vessel stenosis findings could be avoided. In conclusion, the quantitative analysis together with the qualitative analysis rules out artefact-induced stenosis.

Triple-rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndrome

Triple-rule-out (TRO) computed tomographic (CT) angiography can provide a cost-effective evaluation of the coronary arteries, aorta, pulmonary arteries, and adjacent intrathoracic structures for the patient with acute chest pain. TRO CT is most appropriate for the patient who is judged to be at low to intermediate risk for acute coronary syndrome (ACS) and whose symptoms may also be attributed to acute pathologic conditions of the aorta or pulmonary arteries. Although a regular cardiac rhythm remains an important factor in coronary CT image quality, newer CT scanners with 64 or more detector rows afford rapid electrocardiographically (ECG) gated imaging to provide high-quality TRO CT studies in patients with a heart rate of up to 80 beats per minute. Injection of iodinated contrast material (< or = 100 mL) is tailored to provide simultaneous high levels of arterial enhancement in the coronary arteries and aorta (> 300 HU) and in the pulmonary arteries (> 200 HU). To limit radiation exposure, the TRO CT examination does not include the entire chest but is constrained to incorporate the aortic arch down through the heart. Scanning parameters, including prospective ECG tube current modulation and prospective ECG gating with the "step-and-shoot" technique, are tailored to reduce radiation exposure (optimally, 5-9 mSv). When performed with appropriate attention to timing and technique, TRO CT provides coronary image quality equal to that of dedicated coronary CT angiography and pulmonary arterial images that are free of motion artifact related to cardiac pulsation. In an appropriately selected emergency department patient population, TRO CT can safely eliminate the need for further diagnostic testing in over 75% of patients.

Comparison of image quality and arterial enhancement with a dedicated coronary CTA protocol versus a triple rule-out coronary CTA protocol

RATIONALE AND OBJECTIVES

To compare the image quality of dedicated coronary computed tomography angiography (cCTA) to that of triple rule-out (TRO) CTA designed to evaluate the coronary arteries, thoracic aorta, and pulmonary arteries.

MATERIALS AND METHODS

Consecutive cCTA examinations performed by a single radiologist over 1 year were reviewed. Biphasic injection protocols were employed: 70 mL of optiray-350 followed by 40 mL of saline injected at 5.5 mL/second for dedicated cCTA; 70 mL of optiray-350 followed by 25 mL of the contrast diluted with 25 mL of saline injected at 5.0 mL/second for TRO-CTA. Two independent cardiovascular radiologists reviewed the coronary vessels in each case and rated diagnostic image quality on a 5 point scale (1, suboptimal; 3, adequate; 5, excellent). Vascular enhancement was measured in the coronary arteries, aorta, and pulmonary arteries.

RESULTS

There was excellent interobserver agreement between the cardiovascular radiologists (kappa = 0.91). Coronary image quality score were similar among 260 dedicated cCTA studies and 168 TRO-CTA studies (mean: 3.8-3.9. P > .18). At least one coronary segment demonstrated suboptimal image quality in 8% of examinations, including 18 dedicated cCTA studies and 16 TRO studies (P = .94). Enhancement was greater in the distal thoracic aorta of TRO patients (336 vs. 311 Hounsfield units; P = .01); no other significant differences in enhancement were identified in the aorta and coronary arteries of dedicated cCTA and TRO studies. Vascular enhancement was adequate for diagnostic evaluation of the pulmonary arteries in all TRO studies.

CONCLUSIONS

A TRO-CTA protocol using 95 mL of contrast can provide comparable coronary image quality and coronary vascular enhancement as compared to dedicated cCTA with 70 mL of contrast.