Ct Values Do Not Predict Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Transmissibility in College Students.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly contagious and has caused significant medical/socioeconomic impacts. Other than vaccination, effective public health measures, including contact tracing, isolation, and quarantine, is critical for deterring viral transmission, preventing infection progression and resuming normal activities. Viral transmission is affected by many factors, but the viral load and vitality could be among the most important ones. Although in vitro studies have indicated that the amount of virus isolated from infected individuals affects the successful rate of virus isolation, whether the viral load carried at the individual level would determine the transmissibility was unknown. We examined whether the cycle threshold (Ct) value, a measurement of viral load by RT-PCR assay, could differentiate the spreaders from the non-spreaders in a population of college students. Our results indicate that while at the population level the Ct value is lower, suggesting a higher viral load, in the symptomatic spreaders than that in the asymptomatic non-spreaders, there is a significant overlap in the Ct values between the two groups. Thus, Ct value, or the viral load, at the individual level could not predict the transmissibility. Instead, a sensitive method to detect the presence of virus is needed to identify asymptomatic individuals who may carry a low viral load but can still be infectious.

Fibromuscular dysplasia: A comprehensive review on evaluation and management and role for multidisciplinary comprehensive care and patient input model.

Fibromuscular dysplasia is a nonatherosclerotic, under-recognized disorder primarily seen in middle-aged women. It can lead to several complications, such as hypertension, headaches, dissections, aneurysms, myocardial infarctions, and cerebrovascular accidents, to name a few. This article provides a comprehensive review of current literature on epidemiology, etiology, diagnosis, treatment, and long-term surveillance and fibromuscular dysplasia management. In addition, it renders the role of education and prevention for patients living with this condition and family screening. Lastly, it emphasizes the importance of a comprehensive multidisciplinary care model and patient input, given the complexity of this disease and its systemic presence and protean manifestations.

Use of ascending aortic access for imaging and wire rail access for endograft delivery in complex aortic arch anatomy.

In cases of complex aortic arch anatomy, it can be difficult to obtain wire access into the ascending aorta for deployment of a thoracic endograft (thoracic endovascular aortic repair [TEVAR]) using a transfemoral approach. This can result from tortuosity or patulous aneurysmal areas, making platform stability difficult. We report the case of a young adult man with a large proximal left subclavian aneurysm that made zone 0 TEVAR placement very difficult with transfemoral access alone. Direct ascending aortic access through the open chest allowed for a stable through-and-through platform for endograft delivery, highlighting the efficacy of this seldom-needed technique during debranching TEVAR procedures.

Coronary Computed Tomography Angiography Demonstrates a High Burden of Coronary Artery Disease Despite Low-Risk Nuclear Studies in Pre-Liver Transplant Evaluation.

We investigated the presence and severity of coronary artery disease (CAD) in orthotopic liver transplantation (OLT) candidates using coronary artery calcium score (CACS) and coronary computed tomography angiography (CCTA) as compared with the prevalence of normal and abnormal single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). A total of 140 prospective OLT candidates without known CAD underwent coronary artery calcium (CAC) scans with (n = 77) or without CCTA and coronary computed tomography angiography-derived fractional flow reserve (FFRCT ; n = 57) using a dual-source computed tomography (CT) and were followed for 2.6 ± 1.4 years. Coronary plaque was quantified using the segment-involvement score (SIS) and segment stenosis score (SSS). The mean age was 59 ± 6 years, and 65.0% of patients were male. Mean Agatston CACS was 367 ± 653, and 15.0% of patients had CACSs of 0; 83.6% received a SPECT MPI, of which 95.7% were interpreted as normal/probably normal. By CCTA, 9.1% had obstructive CAD (≥70% stenosis), 67.5% had nonobstructive CAD, and 23.4% had no CAD. Nonobstructive CAD was diffuse with mean SIS 3.0 ± 2.9 and SSS 4.5 ± 5.4. Only 14 patients had high risk-findings (severe 3v CAD, n = 4, CACS >1000 n = 10) that prompted X-ray angiography in 3 patients who had undergone CCTA, resulting in revascularization of a high-risk obstruction in 1 patient who had a normal SPECT study. Patients with end-stage liver disease have a high prevalence of nonobstructive CAD by CCTA, which is undiagnosed by SPECT MPI, potentially underestimating cardiovascular risk. Deferring X-ray angiography unless high-risk CCTA findings are present is a potential strategy for avoiding unnecessary X-ray angiography.

Preprocedural Imaging Evaluation of Pulmonary Valve Replacement After Repair of Tetralogy of Fallot: What the Radiologist Needs to Know.

Tetrallogy of Fallot (TOF) is the most frequent form of cyanotic congenital heart disease. Despite advances in surgical and medical treatment, mortality remains high. Residual dysfunction of the pulmonary valve (PV) after correction of right ventricular outflow tract obstruction is an important cause of morbidity, leading to irreversible right ventricular dysfunction, arrhythmias, heart failure and occasionally, death. The strategies for PVR have evolved over the last decades, and the timing of the intervention remains the foundation of the decision-making process. Symptoms of heart failure are unreliable indicators for optimal timing of repair. Imaging plays an essential role in the assessment of PV integrity and dysfunction. The identification of the best timing for PVR requires a multimodality approach. Transthoracic echocardiography is the most commonly used imaging modality for the initial assessment and follow-up of TOF patients, although its utility has technical limitations, especially in adults. Cardiac computed tomography and magnetic resonance imaging are now routinely used for preoperative and postoperative evaluation of these patients, and provide highly valuable information about the anatomy and pathophysiology. Imaging evidence of disease progression is now part of the major guidelines to define the best timing for reintervention. The purpose of this article is to review the pathophysiology after TOF repair, identify the main imaging anatomic and physiologic features, describe the indications for PVR and recognize the role of imaging in the assessment of these patients to define the appropriate timing of PVR.

Spontaneous Coronary Artery Dissection and Its Association With Fibromuscular Dysplasia and Other Vascular Abnormalities.

Fibromuscular dysplasia (FMD) has recently been associated with spontaneous coronary artery dissection (SCAD). We sought to further elucidate the association of FMD with SCAD. We performed a retrospective cohort review of patients with SCAD evaluated at our institution from 2008 to 2019. Baseline characteristics, coronary angiographic data, and screening for FMD were recorded. In patients who completed screening for FMD, variables were compared between patients with FMD and those without. We identified 51 patients with SCAD, all of whom were female, with a mean age of 46.8 years. A quarter of patients underwent percutaneous coronary intervention (PCI) and half of those suffered a complication during PCI. 78% of patients underwent complete screening for FMD, of which 63% were diagnosed with multifocal FMD. Vascular abnormalities other than FMD were found in 70% of screened patients. Patients with FMD were older than those without FMD (50.7 vs 42.6 years, p = 0.006). FMD was more frequently associated with type 2 SCAD (84% vs 47%, p = 0.025), tortuous non-SCAD coronaries (96% vs 53%, p = 0.002), and other vascular abnormalities (84% vs 47%, p = 0.03). In conclusion, the majority of patients within the all-female cohort with SCAD were found to have FMD. Other vascular abnormalities were also common. Patients with FMD were older and were more likely to have type 2 SCAD, tortuous non-SCAD coronary arteries, and other vascular abnormalities.

ACR Appropriateness Criteria® Lower Extremity Arterial Revascularization-Post-Therapy Imaging.

Peripheral arterial disease (PAD) affects millions across the world and in the United States between 9% to 23% of all patients older than 55 years. The refinement of surgical techniques and evolution of endovascular approaches have improved the success rates of revascularization in patients afflicted by lower extremity PAD. However, restenosis or occlusion of previously treated vessels remains a pervasive issue in the postoperative setting. A variety of different imaging options are available to evaluate patients and are reviewed within the context of asymptomatic and symptomatic patients with PAD who have previously undergone endovascular or surgical revascularization. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Pulsatile Abdominal Mass Suspected Abdominal Aortic Aneurysm.

Clinical palpation of a pulsating abdominal mass alerts the clinician to the presence of a possible abdominal aortic aneurysm (AAA). Imaging studies are important in diagnosing and categorizing the extent of the aneurysm and may aid in treatment planning. The consensus of the literature supports the use of ultrasound as the initial screening test in patients with suspected AAA. Population-based ultrasound screening studies have been recommended and have proved effective for male patients > 65 years of age. For diagnosis and pre-intervention evaluation, either multidetector CT or CT angiography is the optimal choice for detailed characterization of the aneurysm. MR angiography may be substituted if CT cannot be performed (for example, because the patient is allergic to iodinated contrast material). Invasive angiography has little role in the diagnosis of AAA and PET and CT remain experimental in patients with suspected aneurysms. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Sudden Onset of Cold, Painful Leg.

Acute limb ischemia (ALI) requires urgent diagnosis and treatment to prevent limb loss. Invasive digital subtraction arteriography (DSA) is the gold standard for diagnosing ALI. DSA is the only diagnostic modality that permits simultaneous treatment of acute arterial occlusion. Noninvasive imaging with MRA or CT angiography may also be appropriate before treatment, especially when the diagnosis of ALI is in doubt or where DSA is unavailable. Other imaging and noninvasive physiologic tests may prove important for longer term management but are less recommended in the acute setting. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Effect of ablation pattern on mechanical function in the atrium.

BACKGROUND: Atrial fibrillation (AF) is often treated with catheter ablation, which induces scar formation to isolate misfiring electrical signals in the left atrium. Successful ablation restores sinus rhythm at the cost of replacing viable myocardium with scar. The impact of ablation scar on mechanical function of the left atrium is poorly understood. OBJECTIVE: We used a computational model to simulate various ablation patterns and determine their effect on atrial global and regional mechanical function. METHODS: A coupled finite-element and hemodynamic circuit model of the left atrium that represents the regional and global mechanics in paroxysmal AF patients was modified to simulate different ablation patterns: step-wise pulmonary vein isolation (PVI), wide area circumferential ablation (WACA), and a posterior ablation developed by nContact, Inc (Morrisville, NC, USA). Atrial pressure-volume relationships and regional wall motion were compared among the models. RESULTS: Ablation increased passive stiffness and decreased active work performed by the atrium. Active emptying volume decreased with increasing scar by up to 44% (11 mL) at a scar volume of 31%. At matched scar volumes, WACA decreased active emptying more severely than PVI and nContact. Similarly, wall motion was depressed most in the WACA model because WACA involved portions of the lateral wall with higher baseline motion. CONCLUSION: Simulated ablation depressed atrial mechanical function to an extent that depended on both scar volume and location, primarily through reducing active emptying. Placing ablation scar in regions with high baseline motion resulted in greater depression of active function, while ablation of the posterior wall was less disruptive.

Effectiveness of integrating delayed computed tomography angiography imaging for left atrial appendage thrombus exclusion into the care of patients undergoing ablation of atrial fibrillation.

BACKGROUND: Computed tomography angiography (CTA) can identify and rule out left atrial appendage (LAA) thrombus when delayed imaging is also performed. OBJECTIVE: In patients referred for CTA to evaluate pulmonary vein anatomy before the ablation of atrial fibrillation (AF) or left atrial flutter (LAFL), we sought to determine the effectiveness of a novel clinical protocol for integrating results of CTA delayed LAA imaging into preprocedure care. METHODS: After making delayed imaging of the LAA part of our routine preablation CTA protocol, we integrated early reporting of preablation CTA LAA imaging results into clinical practice as part of a formal protocol in June 2013. We then analyzed the effectiveness of this protocol by evaluating 320 AF/LAFL ablation patients with CTA imaging during the time period 2012-2014. RESULTS: In CTA patients with delayed LAA imaging, the sensitivity and negative predictive values for LAA thrombus using intracardiac echocardiography or transesophageal echocardiography (TEE) as the reference standard were both 100%. Intracardiac echocardiography during ablation confirmed the absence of thrombus in patients with negative CTA or negative TEE results. No patients with either negative CTA results or equivocal CTA results combined with negative TEE results had strokes or transient ischemic attacks. Overall, the need for TEE procedures decreased from 57.5% to 24.0% during the 3-year period because of the CTA protocol. CONCLUSION: Clinical integration of CTA delayed LAA imaging into the care of patients having catheter ablation of AF or LAFL is feasible, safe, and effective. Such a protocol could be used broadly to improve patient care.

Development of bilateral coronary artery aneurysms in a child with Noonan syndrome.

Noonan syndrome is a constellation of congenital malformations including heart defects, facial anomalies and short stature. The cardiovascular defects are variable and extensive, with the most common being pulmonary stenosis and hypertrophic cardiomyopathy. Coronary artery anomalies have only been reported in a few cases. We report a child with Noonan syndrome status post pulmonary stenosis and atrial septal defect repair, who developed bilateral coronary artery aneurysms. The aneurysms were diagnosed with both cardiac magnetic resonance imaging and coronary computed tomography angiography. There had been no evidence of them on a cardiac MR exam 5 years previously.

Computed tomography angiography and magnetic resonance angiography imaging of the mesenteric vasculature.

Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are highly accurate cross-sectional vascular imaging modalities that have almost completely replaced diagnostic catheter angiography for the evaluation of the mesenteric vasculature. CTA is the technique of choice when evaluating patients with suspected mesenteric ischemia; it permits to differentiate between occlusive and nonocclusive etiologies, to evaluate indirect signs of bowel ischemia, and in some instances, to provide alternative diagnoses. MRA has the advantage of not using ionizing radiation and iodinated contrast agents and can be appropriate in the nonacute setting. Both CTA and MRA are suitable for the assessment of patients with suspected chronic mesenteric ischemia, allowing to evaluate the degree of atherosclerotic steno-occlusive disease and the existence of collateral circulation, as well as other nonatherosclerotic vascular pathologies such as fibromuscular dysplasia and median arcuate ligament syndrome. CTA provides excellent depiction of visceral aneurysms and has an important role to plan therapy for both occlusive and aneurysmal diseases and in the follow-up of patients after open or endovascular mesenteric revascularization procedures. This article provides an introduction to the CTA and MRA imaging protocol to study the mesenteric vasculature, the imaging findings in patients presenting with acute and chronic mesenteric ischemia and visceral aneurysms, and the value of these imaging techniques for therapy planning and follow-up.

Changes in Global and Regional Mechanics Due to Atrial Fibrillation: Insights from a Coupled Finite-Element and Circulation Model.

Atrial fibrillation (AF) is a rhythm disorder with rapidly increasing prevalence due to the aging of the population. AF triggers structural remodeling and a gradual loss of function; however, the relative contributions of specific features of AF-induced remodeling to changes in atrial mechanical function are unclear. We constructed and validated a finite-element model (FEM) of the normal human left atrium using anatomic information from cardiac magnetic resonance imaging, material properties and fiber orientations from published studies, and an iterative algorithm to estimate unloaded geometry. We coupled the FEM to a circuit model to capture hemodynamic interactions between the atrium, pulmonary circulation, and left ventricle. The normal model reproduced measured volumes within 1 SD, as well as most metrics of regional mechanics. Using this validated human model as a starting point, we explored the impact of individual features of atrial remodeling on atrial mechanics and found that a combination of dilation, increased pressure, and fibrosis can explain most of the observed changes in mechanics in patients with paroxysmal AF. However, only impaired ventricular relaxation could reproduce the increased reliance on active emptying we observed in these patients. The resulting model provides new insight into the mechanics of AF and a platform for exploring future therapies.

Noncontrast peripheral MRA with spiral echo train imaging.

PURPOSE: To develop a spin echo train sequence with spiral readout gradients with improved artery-vein contrast for noncontrast angiography. THEORY: Venous T2 becomes shorter as the echo spacing is increased in echo train sequences, improving contrast. Spiral acquisitions, due to their data collection efficiency, facilitate long echo spacings without increasing scan times. METHODS: Bloch equation simulations were performed to determine optimal sequence parameters, and the sequence was applied in five volunteers. In two volunteers, the sequence was performed with a range of echo times and echo spacings to compare with the theoretical contrast behavior. A Cartesian version of the sequence was used to compare contrast appearance with the spiral sequence. Additionally, spiral parallel imaging was optionally used to improve image resolution. RESULTS: In vivo, artery-vein contrast properties followed the general shape predicted by simulations, and good results were obtained in all stations. Compared with a Cartesian implementation, the spiral sequence had superior artery-vein contrast, better spatial resolution (1.2 mm(2) versus 1.5 mm(2) ), and was acquired in less time (1.4 min versus 7.5 min). CONCLUSION: The spiral spin echo train sequence can be used for flow-independent angiography to generate three-dimensional angiograms of the periphery quickly and without the use of contrast agents.

Glomuvenous malformation: magnetic resonance imaging findings.

We report a case of a glomuvenous malformation involving the dorsal aspect of the right hand and distal forearm in an 11-year-old boy. He had a history of multiple vascular anomalies since birth and presented with increasing right hand pain. MRI played an important role in characterizing and determining the extent of the lesion. In particular, dynamic time-resolved contrast-enhanced MR angiography precisely defined its vascularity. The diagnosis was made histopathologically after partial resection of the lesion. Glomuvenous malformation is a rare developmental hamartoma that originates from the glomus body. Clinically they usually resemble a venous malformation but they are a different entity. In the appropriate clinical setting this rare condition must be included in the differential diagnosis of a vascular malformation, especially when subtle arterial enhancement, early venous shunting and progressive filling of dilated venous spaces are depicted on MRA.