Ionizing Radiation in Cardiac Imaging

Ablation of Supraventricular Arrhythmias With as Low as Reasonably Achievable X-Ray exposure (AALARA): Results of Prospective, Observational, Multicenter, Multinational, Open-Label Registry Study on Real World Data Using Routine Ensite 3D Mapping During SVT Ablation

INTRODUCTION

The reduction of fluoroscopic exposure during catheter ablation of supraventricular arrhythmias is widely adopted by experienced electrophysiology physicians with a relatively short learning curve and is becoming the standard of care in many parts of the world. While observational studies in the United States and some parts of Western Europe have evaluated the minimal fluoroscopic approach, there are scarce real-world data for this technique and the generalizability of outcomes in other economic regions.

METHOD

The AALARA study is a prospective, observational, multicenter, and multinational open-label study. Patients were recruited from 13 countries across Central Eastern Europe, North and South Africa, the Middle East, and the CIS (Commonwealth of Independent States), with different levels of operator expertise using minimal fluoroscopic exposure techniques. Data on radiation exposure, procedural success, complications, recurrence, and quality of life changes were collected and analyzed.

RESULT

A total of 680 patients were enrolled and followed for 6 months. The majority were ablation naïve with the commonest arrhythmia ablated being typical AVNRT (58%) followed by Atrial Flutter (23%). Zero fluoroscopy exposure was observed in almost 90% of the cases. Fluoroscopy was most commonly used during the ablation phase of the procedure. We observed a high acute success rate (99%), a low complication rate (0.4%), and a 6-month recurrence rate of 3.8%. There was a significant improvement in the patient's symptoms and quality of life as measured by patient global assessment.

CONCLUSION

The routine use of a 3D mapping system during right-sided ablation was associated with low radiation exposure and associated with high acute success rate, low complications, and recurrence rate along with significant improvement in quality of life. The data confirm the reproducibility of this approach in real-world settings across different healthcare systems, and operator experience supporting this approach to minimize radiation exposure without compromising efficacy and safety.

TRIAL REGISTRATION

NCT04716270.

A simple method for radiation exposure reduction during atrial fibrillation ablation: the lead-apron-free approach

BACKGROUND

Radiofrequency catheter ablation (RFCA) is a well-established treatment for atrial fibrillation (AF). Fluoroscopy, a widely used imaging method for RFCA, has significant implications for human health. Although no fluoroscopy or near-zero fluoroscopy strategies have gained popularity, they have limitations, such as long procedure times, additional equipment, and expertise. A simple and cost-effective radiation reduction method is needed for treating AF and is compatible with the daily workflow. We aimed to compare the efficacy and safety of fluoroscopy-free and lead apron-free (LAF) after transseptal puncture AF ablation with conventional ablation (CON).

METHODS

This retrospective study included all patients who underwent RF catheter AF ablation. The lead apron used for protection was removed immediately before 3D reconstruction of the left atrium (LA) after transseptal puncture (TSP), while fluoroscopy was performed on stand-by and locked-in. The pulmonary vein isolation (PVI) was performed using a 3D mapping system, a multielectrode catheter, and a Smart Touch contact force (CF) sensing catheter, via the lead-apron-free (LAF) method, which is similar to the conventional ablation (CON) method.

RESULTS

This study enrolled 152 consecutive patients, with 72 and 80 patients in the LAF and CON groups, respectively. The LAF group demonstrated significantly lower values in total fluoroscopy time (6.9 vs. 14 min, P<0.001) and dose area product (DAP) values (15.4±12.1 vs. 31.5±17.4 G/m2, P<0.001) than the CON group. However, there was no significant difference in the total procedure time (83.6±21.1 vs. 77.2±11.4 min, P=0.12) between the two groups. Only four procedures (5.5%) required repositioning of the apron, and no complications were observed with the LAF method. Pulmonary vein isolation was achieved in all patients.

CONCLUSIONS

The LAF method reduced fluoroscopy use compared with CON, with no change in procedure time or efficacy.

The Fluoroless Future in Electrophysiology: A State-of-the-Art Review

Fluoroscopy has always been the cornerstone imaging method of interventional cardiology procedures. However, radiation exposure is linked to an increased risk of malignancies and multiorgan diseases. The medical team is even more exposed to X-rays, and a higher incidence of malignancies was reported in this professional group. In the last years, X-ray exposure has increased rapidly, involving, above all, the medical team and young patients and forcing alternative fluoroless imaging methods. In cardiac electrophysiology (EP) and pacing, the advent of 3D electroanatomic mapping systems with dedicated catheters has allowed real-time, high-density reconstruction of both heart anatomy and electrical activity, significantly reducing the use of fluoroscopy. In addition, the diffusion of intracardiac echocardiography has provided high anatomical resolution of moving cardiac structures, providing intraprocedural guidance for more complex catheter ablation procedures. These methods have largely demonstrated safety and effectiveness, allowing for a dramatic reduction in X-ray delivery in most arrhythmias' ablations. However, some technical concerns, as well as higher costs, currently do not allow their spread out in EP labs and limit their use to only procedures that are considered highly complex and time-consuming and in young patients. In this review, we aim to update the current employment of fluoroless imaging in different EP procedures, focusing on its strengths and weaknesses.

Zero-fluoro atrioventricular-nodal reentrant tachycardia ablation

BACKGROUND

Atrioventricular-nodal reentrant tachycardia (AVNRT) is a common supraventricular tachycardia, particularly in younger patients. The treatment of choice is radiofrequency catheter ablation (RFCA), traditionally necessitating ionizing radiation for catheter guidance.

OBJECTIVE

The authors aimed to demonstrate the feasibility and safety of zero-fluoroscopy RFCA of AVNRT using EnSite™ NavX™ as a three-dimensional (3D) electroanatomical mapping system (EAM).

METHODS

The authors retrospectively analyzed 68 patients that underwent AVNRT-RFCA. One group was a priori allocated to conventional fluoroscopy mapping (convFluoro, n = 30). In 38 cases, the electrophysiologist chose to use 3D-EAM for ablation. Of these patients, 20 could be ablated without fluoroscopy use (zeroFluoro). In 18 cases that were initially intended as 3D-EAM, additional fluoroscopy use was necessary due to difficult anatomic conditions (convertedFluoro). Procedure duration, fluoroscopy duration and dose, as well as complications were analyzed.

RESULTS

Procedure duration was similar for the convFluoro and zeroFluoro groups (74 ± 24 min vs. 80 ± 26 min, p = ns). The convertedFluoro group showed longer procedure duration compared to the convFluoro group (94 ± 30 min vs. 74 ± 24 min, p < 0.05). The use of 3D-EAM significantly reduced fluoroscopy duration comparing the convFluoro with the convertedFluoro group (12 ± 9 min vs. 7 ± 6 min, p < 0.05). The difference in fluoroscopy dose between convFluoro and convertedFluoro did not reach significance (169 ± 166 cGycm2 vs. 134 ± 137 cGycm2, p = ns). In zeroFluoro cases, no radiation was used at all. 3D-EAM-guided RFCA was primarily successful in all patients. Overall, there were only few minor complications in the different groups. No major complications occurred.

CONCLUSION

Zero-fluoro RFCA in patients with AVNRT is feasible and safe. 3D-EAM can reduce radiation exposure in the majority of patients without prolonging procedure duration or increasing complications.

Routine use of a 3D mapping system in the ablation of supraventricular arrhythmias with as low as reasonably achievable X-ray exposure (AALARA): protocol for a prospective, observational, multicentre, multinational, open-label registry study

INTRODUCTION

The reduction of fluoroscopic exposure during catheter ablation of supraventricular arrhythmias is widely adopted by experienced electrophysiology physicians with a relatively short learning curve and is becoming standard of care in many parts of the world. While observational studies in the USA and some parts of Western Europe have evaluated the minimal fluoroscopic approach, there are scarce real-world data for this technique and generalisability of outcome in other economic regions.

METHODS AND ANALYSIS

The arrhythmias with as low as reasonably achievable X-ray exposure study is a prospective, observational, multicentre and multinational open-label registry study. Up to 700 patients undergoing catheter ablation for right-sided supraventricular arrhythmias (according to national guidelines) will be enrolled for the routine use of the EnSite Precision 3D mapping system. Participating sites are distributed in 13 countries from Central Eastern Europe, North and South Africa, the Middle East and the CIS (Commonwealth of Independent States), with different levels of expertise using minimal fluoroscopic exposure techniques. After electrophysiological procedure, patients will be followed up for 6 months either in-clinic or via telephone interview. Patients will be asked to complete a study questionnaire at enrolment and 6 months after the invasive procedure to assess quality of life changes secondary to the procedure. The study's primary objective is to describe ionising radiation exposure during catheter ablation when the EnSite Precision 3D mapping system is used in supraventricular tachycardia ablation. The study's secondary objective is to assess the safety and efficacy of this method. Furthermore, fluoroscopy timing, total procedure time, success rate and complications will be reported.

ETHICS AND DISSEMINATION

The study was approved by the ethics committee at Mohammed Bin Khalifa Specialist Cardiac Centre (BDF/R&REC/2020-504) and the medical ethics committees of all participating sites. Participants will be required to provide informed consent before enrolment in the study. The study results will be published and presented at conferences.

TRIAL REGISTRATION NUMBER

NCT04716270.

Zero fluoroscopy catheter ablation for atrial fibrillation: a systematic review and meta-analysis

Introduction

Catheter ablation for atrial fibrillation (AF) is the most frequently performed cardiac ablation procedure worldwide. The majority of ablations can now be performed safely with minimal radiation exposure or even without the use of fluoroscopy, thanks to advances in 3-dimensional electroanatomical mapping systems and/or intracardiac echocardiography. The aim of this study was to conduct a meta-analysis to compare the effectiveness of zero fluoroscopy (ZF) versus non-zero fluoroscopy (NZF) strategies for AF ablation procedures.

Methods

Electronic databases were searched and systematically reviewed for studies comparing procedural parameters and outcomes of ZF vs. NZF approaches in patients undergoing catheter ablation for AF. We used a random-effects model to derive the mean difference (MD) and risk ratios (RR) with a 95% confidence interval (CI).

Results

Our meta-analysis included seven studies comprising 1,593 patients. The ZF approach was found to be feasible in 95.1% of patients. Compared to the NZF approach, the ZF approach significantly reduced procedure time [mean difference (MD): -9.11 min (95% CI: -12.93 to -5.30 min; p < 0.01)], fluoroscopy time [MD: -5.21 min (95% CI: -5.51 to -4.91 min; p < 0.01)], and fluoroscopy dose [MD: -3.96 mGy (95% CI: -4.27 to -3.64; p < 0.01)]. However, there was no significant difference between the two groups in terms of total ablation time [MD: -104.26 s (95% CI: -183.37 to -25.14; p = 0.12)]. Furthermore, there was no significant difference in the acute [risk ratio (RR): 1.01, 95% CI: 1.00-1.02; p = 0.72] and long-term success rates (RR: 0.96, 95% CI: 0.90-1.03; p = 0.56) between the ZF and NZF methods. The complication rate was 2.76% in the entire study population and did not differ between the groups (RR: 0.94, 95% CI: 0.41-2.15; p = 0.89).

Conclusion

The ZF approach is a feasible method for AF ablation procedures. It significantly reduces procedure time and radiation exposure without compromising the acute and long-term success rates or complication rates.

Radiation Dose Reduction for Coronary Artery Calcium Scoring Using a Virtual Noniodine Algorithm on Photon-Counting Detector Computed-Tomography Phantom Data

Background: On the basis of the hypothesis that virtual noniodine (VNI)-based coronary artery calcium scoring (CACS) is feasible at reduced radiation doses, this study assesses the impact of radiation dose reduction on the accuracy of this VNI algorithm on a photon-counting detector (PCD)-CT. Methods: In a systematic in vitro setting, a phantom for CACS simulating three chest sizes was scanned on a clinical PCD-CT. The standard radiation dose was chosen at volumetric CT dose indices (CTDI_Vol) of 1.5, 3.3, 7.0 mGy for small, medium-sized, and large phantoms, and was gradually reduced by adjusting the tube current resulting in 100, 75, 50, and 25%, respectively. VNI images were reconstructed at 55 keV, quantum iterative reconstruction (QIR)1, and at 60 keV/QIR4, and evaluated regarding image quality (image noise (IN), contrast-to-noise ratio (CNR)), and CACS. All VNI results were compared to true noncontrast (TNC)-based CACS at 70 keV and standard radiation dose (reference). Results: IN_TNC was significantly higher than IN_VNI, and IN_VNI at 55 keV/QIR1 higher than at 60 keV/QIR4 (100% dose: 16.7 ± 1.9 vs. 12.8 ± 1.7 vs. 7.7 ± 0.9; p < 0.001 for every radiation dose). CNR_TNC was higher than CNR_VNI, but it was better to use 60 keV/QIR4 (p < 0.001). CACS_VNI showed strong correlation and agreement at every radiation dose (p < 0.001, r > 0.9, intraclass correlation coefficient > 0.9). The coefficients of the variation in root-mean squared error were less than 10% and thus clinically nonrelevant for the CACS_VNI of every radiation dose. Conclusion: This phantom study suggests that CACS_VNI is feasible on PCD-CT, even at reduced radiation dose while maintaining image quality and CACS accuracy.

Radiation Doses in Cardiovascular Computed Tomography

We discussed the contemporary views on the effects of ionising radiation on living organisms and the process of estimating radiation doses in CT examinations and the definitions of the CTDI, CTDIvol, DLP, SSDE, ED. We reviewed the reports from large analyses on the radiation doses in CT examinations of the coronary arteries prior to TAVI procedures, including the CRESCENT, PROTECTION, German Cardiac CT Registry studies. These studies were carried out over the last 10 years and can help confront the daily practice of performing cardiovascular CT examinations in most centres. The reference dose levels for these examinations were also collected. The methods to optimise the radiation dose included tube voltage reduction, ECG-monitored tube current modulation, iterative and deep learning reconstruction techniques, a reduction in the scan range, prospective study protocols, automatic exposure control, heart rate control, rational use of the calcium score, multi-slices and dual-source and wide-field tomography. We also present the studies that indicated the need to raise the organ conversion factor for cardiovascular studies from the 0.014-0.017 mSv/mGy*cm used for chest studies to date to a value of 0.0264-0.03 mSv/mGy*cm.

Incorporating coronary artery calcium scoring in the prediction of obstructive coronary artery disease with myocardial ischemia: a study with sequential use of coronary computed tomography angiography and positron emission tomography imaging

BACKGROUND

Additional strategies are needed to refine the referral for diagnostic testing of symptomatic patients with suspected coronary artery disease (CAD). We aimed to compare various models to predict hemodynamically obstructive CAD.

METHODS AND RESULTS

Symptomatic patients with suspected CAD who underwent coronary artery calcium scoring (CACS) and sequential coronary computed tomography angiography (CCTA) and [15O]H2O positron emission tomography (PET) myocardial perfusion imaging were analyzed. Obstructive CAD was defined as a suspected coronary artery stenosis on CCTA with myocardial ischemia on PET (absolute stress myocardial perfusion ≤ 2.4 mL/g/min in ≥ 1 segment). Three models were developed to predict obstructive CAD-induced myocardial ischemia using logistic regression analysis: (1) basic model: including age, sex and cardiac symptoms, (2) risk factor model: adding number of risk factors to the basic model, and (3) CACS model: adding CACS to the risk factor model. Model performance was evaluated using discriminatory ability with area under the receiver-operating characteristic curves (AUC). A total of 647 patients (mean age 62 ± 9 years, 45% men) underwent CACS and sequential CCTA and PET myocardial perfusion imaging. Obstructive CAD with myocardial ischemia on PET was present in 151 (23%) patients. CACS was independently associated with myocardial ischemia (P < .001). AUC for the discrimination of ischemia for the CACS model was superior over the basic model and risk factor model (P < .001).

CONCLUSIONS

Adding CACS to the model including age, sex, cardiac symptoms and number of risk factors increases the accuracy to predict obstructive CAD with myocardial ischemia on PET in symptomatic patients with suspected CAD.

Coronary Artery Calcium Data and Reporting System (CAC-DRS): A Primer

The Coronary Artery Calcium Data and Reporting System (CAC-DRS) is a standardized reporting method for calcium scoring on computed tomography. CAC-DRS is applied on a per-patient basis and represents the total calcium score with the number of vessels involved. There are 4 risk categories ranging from CAC-DRS 0 to CAC-DRS 3. CAC-DRS also provides risk prediction and treatment recommendations for each category. The main strengths of CAC-DRS include a detailed and meaningful representation of CAC, improved communication between physicians, risk stratification, appropriate treatment recommendations, and uniform data collection, which provides a framework for education and research. The major limitations of CAC-DRS include a few missing components, an overly simple visual approach without any standard reference, and treatment recommendations lacking a basis in clinical trials. This consistent yet straightforward method has the potential to systemize CAC scoring in both gated and non-gated scans.

In-plane Extended Nano-coulter Counter (XnCC) for the Label-free Electrical Detection of Biological Particles

We report an in-plane extended nanopore Coulter counter (XnCC) chip fabricated in a thermoplastic via imprinting. The fabrication of the sensor utilized both photolithography and focused ion beam milling to make the microfluidic network and the in-plane pore sensor, respectively, in Si from which UV resin stamps were generated followed by thermal imprinting to produce the final device in the appropriate plastic (cyclic olefin polymer, COP). As an example of the utility of this in-plane extended nanopore sensor, we enumerated SARS-CoV-2 viral particles (VPs) affinity-selected from saliva and extracellular vesicles (EVs) affinity-selected from plasma samples secured from mouse models exposed to different ionizing radiation doses.

Low-Dose X-Ray Increases Paracellular Permeability of Human Renal Glomerular Endothelial Cells

Objective

Glomerular endothelium functions as a filtration barrier of metabolites in the kidney. Although X-ray irradiation modulated the permeability of the vascular endothelium, the response of human renal glomerular endothelial cells (HRGECs) to low-dose X-ray irradiation has not been investigated. We evaluated the impacts of low-dose X-ray irradiation on HRGECs and revealed the underlying mechanism.

Methods

HRGECs were exposed to X-ray with doses of 0, 0.1, 0.5, 1.0, and 2.0 Gy. The proliferation, viability, and apoptosis of HRGECs were examined by MTT assay, trypan blue staining assay, and TUNEL staining, respectively. The paracellular permeability was assessed by paracellular permeability assay. The expression of VE-cadherin was investigated via immunofluorescence assay. Western blot and qRT-PCR detected the expression levels of VE-cadherin and CLDN5. Besides, the expression levels of pVE-cadherin (pY658), TGF-β, TGF-βRI, Src, p-Src, Smad2, p-Smad2, Smad3, p-Smad3, SNAIL, SLUG, and apoptosis-related proteins were tested by Western blot.

Results

The proliferation, viability, and apoptosis of HRGECs were not affected by low-dose (<2.0 Gy) X-ray irradiation. X-ray irradiation dose-dependently reduced the level of VE-cadherin, and VE-cadherin and CLDN5 levels were reduced with X-ray irradiation. The levels of pY658, p-Src, p-Smad2, and p-Smad3 were upregulated with the increase in X-ray dose. Besides, the paracellular permeability of HRGECs was increased by even low-dose (<2.0 Gy) X-ray irradiation. Therefore, low-dose X-ray irradiation reduced the cumulative content of VE-cadherin and increased the level of pY658 via activation of the TGF-β signaling pathway.

Conclusion

Even though low-dose X-ray exposure had no impact on proliferation, viability, and apoptosis of HRGECs, it increased the paracellular permeability by deterioration and downregulation of VE-cadherin through stimulating the TGF-β signaling pathway. This study built the framework for kidney response to low-dose irradiation exposure.

Quantitative plaque analysis with A.I.-augmented CCTA in end-stage renal disease and complex CAD

BACKGROUND

Adverse cardiovascular events are a significant cause of mortality in end-stage renal disease (ESRD) patients. High-risk plaque anatomy may be a significant contributor. However, their atherosclerotic phenotypes have not been described. We sought to define atherosclerotic plaque characteristics (APC) in dialysis patients using artificial-intelligence augmented CCTA.

METHODS

We retrospectively analyzed ESRD patients referred for CCTA using an FDA approved artificial-intelligence augmented-CCTA program (Cleerly). Coronary lesions were evaluated for APCs by CCTA. APCs included percent atheroma volume(PAV), low-density non-calcified-plaque (LD-NCP), non-calcified-plaque (NCP), calcified-plaque (CP), length, and high-risk-plaque (HRP), defined by LD-NCP and positive arterial remodeling >1.10 (PR).

RESULTS

79 ESRD patients were enrolled, mean age 65.3 years, 32.9% female. Disease distribution was non-obstructive (65.8%), 1-vessel disease (21.5%), 2-vessel disease (7.6%), and 3-vessel disease (5.1%). Mean total plaque volume (TPV) was 810.0 mm³, LD-NCP 16.8 mm³, NCP 403.1 mm³, and CP 390.1 mm³. HRP was present in 81.0% patients. Patients with at least one >50% stenosis, or obstructive lesions, had significantly higher TPV, LD-NCP, NCP, and CP. Patients >65 years had more CP and higher PAV.

CONCLUSION

Our study provides novel insight into ESRD plaque phenotypes and demonstrates that artificial-intelligence augmented CCTA analysis is feasible for CAD characterization despite severe calcification. We demonstrate elevated plaque burden and stenosis caused by predominantly non-calcified-plaque. Furthermore, the quantity of calcified-plaques increased with age, with men exhibiting increased number of 2-feature plaques and higher plaque volumes. Artificial-intelligence augmented CCTA analysis of APCs may be a promising metric for cardiac risk stratification and warrants further prospective investigation.

[Cardiac computed tomography - Current diagnostic role in cardiology]

Computed tomography (CT) imaging of the heart requires specific equipment and protocols in order to synchronize image generation with the electrocardiogram (ECG), usually achieved via ECG-gated reconstruction or ECG-triggered acquisition. The main application of cardiac CT is coronary artery imaging. Contrast-enhanced coronary artery CT allows the identification and rule-out of stenoses and is a diagnostic approach to patients with suspected chronic coronary artery disease or acute chest pain, provided that patient characteristics are associated with a high likelihood of fully diagnostic image quality. In addition, CT has the potential to visualize coronary atherosclerotic plaque, even if non-obstructive, and data suggest that this may be a valuable guide towards more intensive risk modification strategy such as statin therapy. In recent years, the use of CT imaging to guide structural heart interventions has become another important application, and many interventions, such as transcatheter aortic valve implantation, substantially depend on CT imaging to plan the procedure, minimize risks, and optimize outcome.

Cardiac computed tomographic angiography after abnormal ischemia test as a gatekeeper to invasive coronary angiography

This study aimed to determine the impact of systematic coronary computed tomographic angiography (CCTA) use following an abnormal non-invasive ischemia test (NIST) on patient selection strategy for invasive coronary angiography (ICA). In patients with suspected stable coronary artery disease (CAD), NIST use frequently results in sub-optimal diagnostic and revascularization yields of ICA. This randomized clinical trial, conducted at a single academic tertiary center, selected 220 symptomatic patients with mild-to-moderately abnormal NIST results who were referred for ICA. Patients received either the originally intended ICA (n = 105) or CCTA (n = 115). The primary endpoint was the diagnostic yield of ICA in each group. Revascularization yield and major adverse cardiovascular events at 12 months were also assessed. The patients were 69 ± 9 years old, 60% were men, and 31% had typical angina. Mean pre-test probability of obstructive CAD was 34%. Overall prevalence of obstructive CAD was 37.7% on the index angiographic procedure. In the CCTA group, ICA was cancelled by referring physicians in 83 patients (72.2%) after receiving CCTA results. For those undergoing ICA, diagnostic (84.4% vs. 41.7%, p<0.001) and revascularization (71.9% vs. 38.8%, p = 0.001) yields were significantly higher for CCTA-guided ICA than for standard NIST-guided ICA. Mean cumulative radiation exposure was significantly lower in the CCTA-guided ICA arm than in the NIST-guided ICA arm (12 ± 9 vs. 16 ± 10 mSv, respectively, p = 0.024). There were no significant differences in the primary safety endpoint rates between the strategies (p = 0.439). In patients with suspected CAD and mild-to-moderately abnormal ischemia tests, a diagnostic strategy including CCTA as a gatekeeper is safe and effective and significantly improves diagnostic and revascularization yields of ICA.

Radiation Doses in Patients Undergoing Computed Tomographic Coronary Artery Calcium Evaluation With a 64-Slice Scanner Versus a 256-Slice Scanner

Computed tomographic coronary artery calcium scanning enables cardiovascular risk stratification; however, exposing patients to high radiation levels is an ongoing concern. New-generation computed tomographic systems use lower radiation doses than older systems do. To quantify comparative doses of radiation exposure, we prospectively acquired images from 220 patients with use of a 64-slice GE LightSpeed VCT scanner (control group, n=110) and a 256-slice GE Revolution scanner (study group, n=110). The groups were matched for age, sex, and body mass index; statistical analysis included t tests and linear regression. The mean dose-length product was 21% lower in the study group than in the control group (60.2 ± 27 vs 75.9 ± 22.6 mGy·cm; P <0.001) and also in each body mass index subgroup. Similarly, the mean effective radiation dose was 21% lower in the study group (0.84 ± 0.38 vs 1.06 ± 0.32 mSv) and lower in each weight subgroup. After adjustment for sex, women in the study group had a lower dose-length product (50.4 ± 23.4 vs 64.7 ± 27.6 mGy·cm) than men did and received a lower effective dose (0.7 ± 0.32 vs 0.9 ± 0.38 mSv) (P=0.009). As body mass index and waist circumference increased, so did doses for both scanners. Our study group was exposed to radiation doses lower than the previously determined standard of 1 mSv, even after adjustment for body mass index and waist circumference. In 256-slice scanning for coronary artery calcium, radiation doses are now similar to those in lung cancer screening and mammography.

Comparison of radiation dose and its correlates between coronary computed tomography angiography and invasive coronary angiography in Northeastern Thailand

Background

The number of coronary computed tomography angiography (CCTA) exams is steadily growing. A novel computed tomography (CT) system has been developed to increase image quality while lowering patient radiation. The radiation dose attributed to CCTA has received considerable attention, whereas the dose associated with invasive catheter angiography (ICA) has received less. This study aims to investigate the radiation exposure of CCTA in patients and compare it to ICA.

Results

The mean effective dose of CCTA was 2.88 ± 0.85 mSv which was significantly lower than the mean effective dose of ICA (5.61 ± 0.55 mSv), p < 0.0001. The effective dose of CCTA correlated with the weight, height, and BMI, while the effective dose of ICA was associated with patient weight and BMI. The radiation exposure from CCTA has been considerably reduced over the last ten years by almost 2.5 folds. The mean radiation dose from the newer generation CT used in 2019 was significantly lower than that of the single-source CT in 2010 (2.88 ± 0.85 mSv vs. 7.15 ± 3.4 mSv, p < 0.001).

Conclusions

CCTA allows evaluation of CAD with a significantly less effective radiation dose to patients than diagnostic ICA. There was a significant decrease in radiation dose from CCTA over time. Regular measurement of patient doses is an essential step to optimize exposure. It makes operators aware of their performance and allows comparisons with generally accepted practices.

NON-INVASIVE CORONARY ARTERIES ATHEROSCLEROSIS CT-VISUALIZATION: UP-TO-DATE STANDARDS AND OWN CLINICAL EXPERIENCE STUDY

Non-invasive coronary arteries (CA) visualization experiences fast progress recently. Existing evidence-based dataand trials show that there is a great need in non-invasive technologies able to trustworthy and accurately identifyCA high risk atherosclerotic plaques (AP) and provide more insights into atherosclerosis pathophysiology in individ-ual patents, being accurate qualitative and quantitative methods of primary diagnosis and answer to therapeuticintervention indicators in patients with coronary artery (CAD). Until now in Ukraine there were no studies evaluat-ing accuracy of last generation 640-sliced computed tomography coronary angiography (CTCA) in diagnosing of dif-ferent CAD forms.Objective of the study was to study diagnostic accuracy of CTCA compared to invasive coronary angiography (iCAG)in the patients with different forms of chronic CAD before surgeon revascularization.Materials and methods. From I.2019 to V.2021 we prospectively studied 201 patients with different chronic CADforms (76.6 % men and 23.4 % women) aged (61.8 ± 9.2) years hospitalized to our center for diagnostic work-upand decision about primary or secondary revascularization (coronary aortic bypass (CABG) or percutaneous (PCI)intervention). All patients underwent planned CTCA and iCAG.Results and conclusions. There were no significant complication duing procedures performed. Totally 2412 coro-nary segments were visualized and studied. Coronary calcium index (CI) highly significantly correlated with overallburden and severity of atherosclerotic process (r = 0,73, р < 0.0001). CTCA compared to iCAG showed no false-nega-tive results and only 6 (2.99 %) false positive results in cases of insignificant lesions. There was no significant dif-ference in diagnostic accuracy for significant stenoses with very high accuracy for overall vessels lesions quantityand burden (r = 0.95, р < 0.0001) with very high prognostic method accuracy (AUC 0.99; OR >>1000, р < 0.0001),making high multi-sliced CTCA safe and extremely accurate method for qualitative and quantitative diagnosis of ath-erosclerotic CA lesions absolutely comparable to iCAG, including hemodynamic significance evaluation.

Blood lead level in Chinese adults with and without coronary artery disease

BACKGROUND

The Trial to Assess Chelation Therapy study found that edetate disodium (disodium ethylenediaminetetraacetic acid) chelation therapy significantly reduced the incidence of cardiac events in stable post-myocardial infarction patients, and a body of epidemiological data has shown that accumulation of biologically active metals, such as lead and cadmium, is an important risk factor for cardiovascular disease. However, limited studies have focused on the relationship between angiographically diagnosed coronary artery disease (CAD) and lead exposure. This study compared blood lead level (BLL) in Chinese patients with and without CAD.

METHODS

In this prospective, observational study, 450 consecutive patients admitted to Beijing Anzhen Hospital with suspected CAD from November 1, 2018, to January 30, 2019, were enrolled. All patients underwent coronary angiography, and an experienced heart team calculated the SYNTAX scores (SXscore) for all available coronary angiograms. BLLs were determined with atomic absorption spectrophotometry and compared between patients with angiographically diagnosed CAD and those without CAD.

RESULTS

In total, 343 (76%) patients had CAD, of whom 42% had low (0-22), 22% had intermediate (23-32), and 36% had high (≥ 33) SXscore. BLLs were 36.8 ± 16.95 μg/L in patients with CAD and 31.2 ± 15.75 μg/L in those without CAD (P = 0.003). When BLLs were categorized into three groups (low, middle, high), CAD prevalence increased with increasing BLLs (P < 0.05). In the multivariate regression model, BLLs were associated with CAD (odds ratio (OR): 1.023, 95% confidence interval (CI): 1.008-1.039; P = 0.0017). OR in the high versus low BLL group was 2.36 (95% CI: 1.29-4.42,P = 0.003). Furthermore, BLLs were independently associated with intermediate and high SXscore (adjusted OR: 1.050, 95% CI: 1.036-1.066; P < 0.0001).

CONCLUSION

BLLs were significantly associated with angiographically diagnosed CAD. Furthermore, BLLs showed excellent predictive value for SXscore, especially for complex coronary artery lesions.

The Influence of Mesenteric Defects Closure on the Use of Computed Tomography for Abdominal Pain 5 Years After Laparoscopic Gastric Bypass-a Post Hoc Analysis of a Randomized Clinical Trial

Background

Abdominal pain after laparoscopic Roux-en-Y gastric bypass (LRYGB) is a common and unwanted complication that typically leads to further exploration through radiology. Concerns have been raised regarding the consequences of this radiation exposure and its correlation with the lifetime risk of cancer. The aim of this study was to evaluate the differences in computed tomography (CT) use between LRYGB patients with open and closed mesenteric defects and to assess the radiological findings and radiation doses.

Methods

This subgroup analysis included 300 patients randomized to either closure (n = 150) or nonclosure (n = 150) of mesenteric defects during LRYGB. The total number of CT scans performed due to abdominal pain in the first 5 postoperative years was recorded together with the radiological findings and radiation doses.

Results

A total of 132 patients (44%) underwent 281 abdominal CT scans, including 133 scans for 67 patients with open mesenteric defects (45%) and 148 scans for 65 patients with closed mesenteric defects (43%). Radiological findings consistent with small bowel obstruction or internal hernia were found in 31 (23%) of the scans for patients with open defects and in 18 (12%) of the scans for patients with closed defects (p = 0.014). The other pathological and radiological findings were infrequent and not significantly different between groups. At the 5-year follow-up, the total radiation dose was 82,400 mGy cm in the nonclosure group and 85,800 mGy cm in the closure group.

Conclusion

Closure of mesenteric defects did not influence the use of CT to assess abdominal pain.

Graphical abstract

Assessing the downstream value of first-line cardiac positron emission tomography (PET) imaging using real world Medicare fee-for-service claims data

BACKGROUND

Higher imaging quality makes cardiac positron emission tomography (PET) desirable for evaluation of suspected coronary artery disease (CAD). High cost of PET imaging may be offset by reduced utilization and/or improved outcomes.

METHODS

This retrospective observational study utilized Medicare fee-for-service dataset. Study participants had no CAD diagnosis within 1 year prior to initial imaging. The PET group (PET imaging) and propensity score matched comparison group (single photon emission computed tomography or stress echocardiography) underwent index imaging between January 2014 and December 2016. Outcomes were analyzed using generalized linear models.

RESULTS

Among 144,503 study subjects, 4619 (3.2%) had PET and 139,884 (96.8%) had conventional imaging. After matching, each group had 4619 patients (mean age 74 years, 59% female). The PET group had lower radiation exposure (3.8 milliSievert less per year, 95% CI - 3.96 to - 3.64, P < .0001) and unstable coronary syndrome (incidence rate ratio (IRR) 0.77, 95% CI 0.64-0.94, P = .008). The PET group experienced more hospital admissions (IRR 1.10, 95% CI 1.06-1.15, P < .0001), more use of percutaneous coronary intervention (IRR 1.24, 95% CI 1.02-1.50, P = 0.03), while similar mortality rate (hazard ratio 0.95, 95% CI 0.78-1.14, P = 0.55). The PET group had higher medical spending ($2358.2 vs $1774.3, difference = $583.9 per patient per month, P < .0001).

CONCLUSIONS

First-line PET imaging was not associated with reduced levels of utilization and spending. Clinical outcomes were mostly similar.

Simplifying the ISCHEMIA trial algorithm for clinical practice: Identifying left main coronary artery disease using coronary artery calcium scans

BACKGROUND

Several recent trials have evaluated invasive versus medical therapy for stable ischemic heart disease. Importantly, patients with significant left main coronary stenosis (LMCS) were excluded from these trials. In the ISCHEMIA trial, these patients were identified by a coronary CT angiogram (CCTA), which adds time, expense, and contrast exposure. We tested whether a coronary artery calcium scan (CACS), a simpler, less expensive test, could replace CCTA to exclude significant LMCS.

METHODS

We hypothesized that patients with ≥50% LMCS would have a LM CACS score > 0. As a corollary, we postulated that a LM CACS = 0 would exclude patients with LMCS. To test this, we searched Intermountain Healthcare's electronic medical records database for all adult patients who had undergone non-contrast cardiac CT for quantitative CACS scoring prior to invasive coronary angiography (ICA). Patients aged <50 and those with a heart transplant were excluded. Cases with incomplete (qualitative) angiographic reports for LMCS and those with incomplete or discrepant LM CACS results were reviewed and reassessed blinded to CACS or ICA findings, respectively.

RESULTS

Among 669 candidate patients with CACS followed by ICA, 36 qualifying patients were identified who had a quantitative CACS score and LMCS ≥ 50%. Their age averaged 71.8 years, and 81% were men. Angiographic LMCS averaged 72% (range 50%-99%). Median time between CACS and ICA was 6 days. Total CACS score averaged 2,383 Agatston Units (AU), range 571-6,636. LM CACS score averaged 197 AU, range 31-610. Importantly, no LMCS patient had a LM CACS score of 0 vs 57% (362/633) of non-LMCS controls (P < .00001).

CONCLUSIONS

Our results support the hypothesis that an easily administered, inexpensive, low radiation CACS can identify a large subset of patients with a very low risk of LMCS who would not have the need for routine CCTA. Using CACS to exclude LMCS may efficiently allow for safe implementation of an initial medical therapy strategy of patients with stable ischemic heart disease in clinical practice. These promising results deserve validation in larger data sets.

In vivo Cell Tracking Using Non-invasive Imaging of Iron Oxide-Based Particles with Particular Relevance for Stem Cell-Based Treatments of Neurological and Cardiac Disease

Stem cell-based therapeutics is a rapidly developing field associated with a number of clinical challenges. One such challenge lies in the implementation of methods to track stem cells and stem cell-derived cells in experimental animal models and in the living patient. Here, we provide an overview of cell tracking in the context of cardiac and neurological disease, focusing on the use of iron oxide-based particles (IOPs) visualized in vivo using magnetic resonance imaging (MRI). We discuss the types of IOPs available for such tracking, their advantages and limitations, approaches for labeling cells with IOPs, biological interactions and effects of IOPs at the molecular and cellular levels, and MRI-based and associated approaches for in vivo and histological visualization. We conclude with reviews of the literature on IOP-based cell tracking in cardiac and neurological disease, covering both preclinical and clinical studies.

Visually estimated coronary artery calcium score improves SPECT-MPI risk stratification

Aims

Computed tomographic attenuation correction (CTAC) scans for single photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) may reveal coronary artery calcification. The independent prognostic value of a visually estimated coronary artery calcium score (VECACS) from these low-dose, non-gated scans is not established.

Methods & Results

VECACS was evaluated in 4,720 patients undergoing SPECT-MPI with CTAC using a 4-point scale. Major adverse cardiac events (MACE) were defined as all-cause mortality, acute coronary syndrome, or revascularization > 90 days after SPECT-MPI. Independent associations with MACE were determined with multivariable Cox proportional hazards analyses adjusted for age, sex, past medical history, perfusion findings, and left ventricular ejection fraction. During a median follow up of 2.9 years (interquartile range 1.8 - 4.2), 494 (10.5%) patients experienced MACE. Compared to absent VECACS, patients with increased VECACS were more likely to experience MACE (all log-rank p < 0.001), and findings were similar when stratified by normal or abnormal perfusion. Multivariable analysis showed an increased MACE risk associated with VECACS categories of equivocal (adjusted hazard ratio [HR] 2.54, 95% CI 1.45-4.45, p = 0.001), present (adjusted HR 2.44, 95% CI 1.74-3.42, p < 0.001) and extensive (adjusted HR 3.47, 95% CI 2.41-5.00, p < 0.001) compared to absent. Addition of VECACS to the multivariable model improved risk classification (continuous net reclassification index 0.207, 95% CI 0.131 - 0.310).

Conclusion

VECACS was an independent predictor of MACE in this large SPECT-MPI patient cohort. VECACS from CTAC can be used to improve risk stratification with SPECT-MPI without additional radiation.

Radiation exposure after myocardial perfusion imaging with Cadmium-Zinc-Telluride camera versus conventional camera

BACKGROUND

Patient exposure to radiation during the management of coronary heart disease (CHD) can be reduced with more efficient technologies in nuclear medicine, such as the Cadmium-Zinc-Telluride (CZT) gamma-camera for myocardial perfusion imaging (MPI) studies. However, it has been suggested that CZT has lower specificity, which might lead to more downstream radiological procedures, particularly among obese individuals.

METHODS AND RESULTS

We evaluated 244 patients with suspected CHD who underwent CZT-SPECT and matched 1:1 according to sex, age, and body mass index (BMI) with those undergoing MPI study with the Anger gamma-camera (Anger-SPECT). The outcome was the total radiation exposure from the MPI study added to the radiation exposure from all subsequent cardiac examinations during a 90-day follow-up. The total radiation dose after 90 days was significantly lower in the CZT-SPECT group (6.4 ± 4.8 vs 9.5±4.9 mSv, P < .001). After adjusting for potential confounders, CZT-SPECT remained associated with lower total radiation dose, but it significantly attenuated among obese individuals (Beta coefficient - 3.73 ± 0.86 for BMI < 30 vs - 2.30 ± 0.92 for BMI ≥ 30 Kg/m2, P for interaction < 0.032).

CONCLUSIONS

CZT-SPECT was associated with lower total radiation doses compared to Anger-SPECT, albeit this benefit may be attenuated in obese individuals.

Safety and effectiveness of strategies to reduce radiation exposure to proceduralists performing cardiac catheterization procedures: a systematic review

OBJECTIVE

The objective of this systematic review was to synthesize the best available evidence on the effect of various radiation protection strategies on radiation dose received by proceduralists performing cardiac catheterization procedures involving fluoroscopy.

INTRODUCTION

Cardiac catheterization procedures under fluoroscopy are the gold standard diagnostic and treatment method for patients with coronary artery disease. The growing demand of procedures means that proceduralists are being exposed to increasing amounts of radiation, resulting in an increased risk of deterministic and stochastic effects. Standard protective strategies and equipment such as lead garments reduce radiation exposure; however, the evidence surrounding additional equipment is contradictory.

INCLUSION CRITERIA

Randomized controlled trials that compared the use of an additional radiation protection strategy with conventional radiation protection methods were considered for inclusion. The primary outcome of interest was the radiation dose received by the proceduralist during cardiac catheterization procedures.

METHODS

A three-step search was conducted in MEDLINE, CINAHL, Embase, and the Cochrane Library (CENTRAL). Trials published in the English language with adult participants were included. Trials published from database inception until July 2019 were eligible for inclusion. The methodological quality of the included studies was assessed using the JBI critical appraisal checklist for randomized controlled trials. Quantitative data were extracted from the included papers using the JBI data extraction tool. Results that could not be pooled in meta-analysis were reported in a narrative form.

RESULTS

Fifteen randomized controlled trials were included in the review. Six radiation protection strategies were assessed: leaded and unleaded pelvic or arm drapes, transradial protection board, remotely controlled mechanical contrast injector, extension tubing for contrast injection, real-time radiation monitor, and a reduction in frame rate to 7.5 frames per second. Pooled data from two trials demonstrated a statistically significant decrease in the mean radiation dose (P < 0.00001) received by proceduralists performing transfemoral cardiac catheterization on patients who received a leaded pelvic drape compared to standard protection. One trial that compared the use of unleaded pelvic drapes placed on patients compared to standard protection reported a statistically significant decrease (P = 0.004) in the mean radiation dose received by proceduralists.Compared to standard protection, two trials that used unleaded arm drapes for patients, one trial that used a remotely controlled mechanical contrast injector, and one trial that used a transradial protection board demonstrated a statistically significant reduction in the radiation dose received by proceduralists.Similarly, using a frame rate of 7.5 versus 15 frames per second and monitoring radiation dose in real-time radiation significantly lowered the radiation dose received by the proceduralist. One trial demonstrated no statistically significant difference in proceduralist radiation dose among those who used the extension tubing compared to standard protection (P = 1).

CONCLUSIONS

This review provides evidence to support the use of leaded pelvic drapes for patients as an additional radiation protection strategy for proceduralists performing transradial or transfemoral cardiac catheterization. Further studies on the effectiveness of using a lower fluoroscopy frame rate, real-time radiation monitor, and transradial protection board are needed.

Segmental Evaluation of Thoracic Aortic Calcium and Their Relations with Cardiovascular Risk Factors in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Thoracic aortic calcium (TAC) appears to be a subclinical marker of cardiovascular disease (CVD) and to predict cardiovascular (CV) mortality. However, studies on TAC use tomographic scans obtained for coronary artery calcium (CAC) score, which does not include the aortic arch. This study evaluates TAC prevalence in aortic arch (AAC), ascending (ATAC) and descending thoracic aorta (DTAC) and verify whether they are associated with the same CV risk factors. Cross-sectional analysis, including 2427 participants (mean age 55.6 ± 8.7; 54.1% women) of the ELSA-Brasil cohort. Nonenhanced ECG-gated tomographies were performed in 2015–2016. Multivariable logistic regression estimated the CV risk factors associated with calcium in each segment. Overall prevalence of ATAC, AAC and DTAC was, 23.1%, 62.1%, and 31.2%, respectively. About 90.4% of the individuals with TAC had AAC and only 19.5% had calcium in all segments. In the multivariable analysis, increasing age, lower levels of schooling, current smoking, higher body mass index, and hypertension remained associated with calcium in all segments. No sex or race/ethnicity differences were found in any aortic segment. Diabetes and dyslipidemia were associated with ATAC and DTAC, but not with AAC, suggesting that AAC may reflect an overlap of mechanisms that impact vascular health, including atherosclerosis.

Patient first versus computed tomography first strategy in testing for stable coronary artery disease: dispelling the prevailing myths and biases

We advocate an evidence-based discussion for a patient first philosophy when considering "the right test for the right patient." Numerous test options exist for the evaluation of symptoms of possible stable ischemic heart disease. Major guidelines have traditionally focused on functional testing with or without imaging to clarify symptoms, diagnose ischemia, stratify prognosis, and guide management. Recently, industry advocates have emphasized modality-specific approaches such as computed tomography (CT First) as an initial test strategy for possible stable CAD. We review the key evidence to demonstrate that current best practice would focus on a patient first approach rather than a modality-specific approach.

[Assessment of the practices and knowledge among cardiologists regarding radiation protection in Tunisia]

Introduction

les procédures de cardiologie interventionnelle sont devenues complexes et chronophages avec un sur-risque d´exposition aux rayonnements ionisants. L’objectif de notre étude était d’évaluer le niveau des connaissances et des pratiques en radioprotection des cardiologues Tunisiens exposés au rayon X.

Méthodes

notre étude est descriptive analytique réalisée en octobre 2019, organisée sous forme de questionnaire anonyme des connaissances et pratiques en radioprotection et envoyé à tous les Cardiologues Tunisiens exposés aux rayons X.

Résultats

parmi 126 cardiologues exposés aux rayons X et ayant reçu le questionnaire, 58 médecins ont répondu au questionnaire (48%), avec une prédominance masculine (72%, n=42). Trente-huit médecins (65%) exerçaient dans le secteur public. L´expérience professionnelle était en moyenne de 12,02 ans (ET 6,88 ans). La moitié des médecins avaient un score de connaissances inférieur à 50%. La moyenne du score des pratiques était de 43,83 (ET 13,95%). Le port du tablier en plomb, de la cache thyroïde, du dosimètre, des lunettes en plomb, du calot en plomb était respectivement de 100% (n=58), 86,2% (n=50), 30,7% (n=18), 12,1% (n=7) et 1,7% (n=1). Il n´y avait pas de corrélation entre les scores et l´âge du médecin ainsi que la durée de l´expérience professionnelle. Les scores de connaissances ne différaient pas statistiquement entre les 2 sexes (p=0,06) ni entre le secteur public et le secteur privé (p=0,9). Le score de pratique était significativement plus élevé chez les hommes (0.007) et les cardiologues interventionnels comparés aux rythmologues et cardiopédiatres (p<0.001).

Conclusion

le niveau des connaissances et des pratiques des cardiologues Tunisiens en radioprotection est globalement insuffisant. Ce qui interpelle les autorités sanitaires à organiser un plan de formation régulier pour cette population.

Zero-fluoroscopy catheter ablation for atrial fibrillation: a transitional period experience

BACKGROUND

Radiofrequency catheter ablation for atrial fibrillation (AF) without using fluoroscopy has been getting popular. In this study, we reported the transition period experience of the zero-fluoroscopy procedure by an experienced operator and shared our zero-fluoroscopy protocol.

METHOD

A total of consecutive 30 AF ablation cases attempted to be treated without fluoroscopy were investigated. Ten serial cases were grouped as fluoroscopy-guided period, and period 1-3 in chronological order. All zero-fluoroscopy attempted cases were assisted with an intracardiac echocardiography device with a three-dimensional electroanatomical system.

RESULTS

Complete zero-fluoroscopy procedure was achieved at the 6th case during the transitional period. During the first period, the total procedure time slightly increased in, but afterward, procedure time was continuously decreased, and it became significantly shorter in the third period than the previous fluoroscopy-guided period. Any additional use of fluoroscopy during the transitional period was mainly for transseptal puncture and diagnostic catheter placement into the coronary sinus. Pulmonary vein isolation was achieved in all patients, and there was one case of hemodynamically insignificant moderate amount pericardial effusion.

CONCLUSION

For an experienced operator, complete zero-fluoroscopy AF ablation might be achieved safely and feasibly within 5-10 cases. Fluoroscopy equipment backup might be useful during the learning period for beginners in the zero-fluoroscopy procedure.

Coronary artery calcium testing in low-intermediate risk symptomatic patients with suspected coronary artery disease: An effective gatekeeper to further testing?

Computed tomography for quantification of coronary artery calcium (CAC) is a simple non-invasive tool to assess atherosclerotic plaque burden. CAC is highly correlated with coronary atherosclerosis and is a robust predictor of cardiovascular outcomes. Recently, the 2018 ACC/AHA Cholesterol Guidelines endorsed the use of CAC scores in asymptomatic, intermediate risk individuals where the decision to initiate stain therapy is uncertain. However, whether quantification of CAC may play a role in the assessment of symptomatic individuals remains a matter of debate. In this review, we examine the evidence for the use of CAC in low-intermediate risk patients with chest pain. This appraisal places a particular focus on the growing body of literature supporting the negative predictive value of a CAC score of zero to rule out significant coronary artery disease in those without high-risk features. We also evaluate current guidelines, limitations, and future research directions for CAC scoring in this important subgroup of patients.

Non-invasive imaging of the coronary arteries

Non-invasive imaging of the coronary arteries is an enterprise in rapid development. From the research perspective, there is great demand for in vivo techniques that can reliably identify features of high-risk plaque that may offer insight into pathophysiological processes and act as surrogate indicators of response to therapeutic intervention. Meanwhile, there is clear clinical need for greater accuracy in diagnosis and prognostic stratification. Fortunately, ongoing technological improvements and emerging data from randomized clinical trials are helping make these elusive goals a reality. This review provides an update on the current status of non-invasive coronary imaging with computed tomography, magnetic resonance, and positron emission tomography with a focus on current clinical applications and future research directions.

Systolic High-Pitch Coronary CT Angiography for Evaluation of the Coronary Arteries in Heart Transplant Recipients

OBJECTIVE. The purpose of this study was to evaluate the feasibility, image quality, and radiation dose of high-pitch coronary CT angiography (CCTA) in orthotopic heart transplant (OHT) recipients. SUBJECTS AND METHODS. Twenty-two consecutive OHT recipients (16 men, six women; median age, 66.5 years [interquartile range, 51.3-70.3 years]; median heart rate, 91 beats/min [interquartile range, 79.3-97.3 beats/min]) underwent CCTA with a third-generation dual-source CT scanner in high-pitch mode to rule out coronary allograft vasculopathy. Data acquisition was triggered at 30% of the R-R interval. Two independent observers blindly assessed image quality on a per-segment, per-vessel, and per-patient basis using a 4-point scale (4, excellent; 1, not evaluative). Scores 2-4 indicated diagnostic quality. Studies were compared with previously performed retrospective ECG-gated examinations, when available. Interobserver agreement on the image quality was assessed with kappa statistics. Radiation dose was recorded. RESULTS. A total of 322 coronary segments were evaluated. Diagnostic image quality was observed in 97.5% of the segments. Interobserver agreement for image quality assessment was very good on a per-patient (κ = 0.82), per-vessel (κ = 0.83), and per-segment basis (κ = 0.89). The median per-patient image quality score was 4.0 (3.0-4.0) for the entire coronary tree. A comparison of image quality scores between high-pitch and retrospective ECG-gated CCTA examinations showed no significant differences, but the estimated mean radiation dose was significantly lower for the high-pitch mode (median dose-length product, 31.6 mGy × cm [interquartile range, 23.1-38.8 mGy × cm] vs 736.5 mGy × cm [interquartile range, 655.5-845.7 mGy × cm], p < 0.001). CONCLUSION. Performing single-heartbeat high-pitch CCTA during the systolic phase of the cardiac cycle in OHT recipients results in diagnostic image quality in coronary angiograms at very low radiation dose.

Role of pre-procedural CT imaging on catheter ablation in patients with atrial fibrillation: procedural outcomes and radiological exposure

BACKGROUND

Cardiac computed tomography (CT) is commonly used to study left atrial (LA) and pulmonary veins (PVs) anatomy before atrial fibrillation (AF) ablation. The aim of the study was to determine the impact of pre-procedural cardiac CT with 3D reconstruction on procedural outcomes and radiological exposure in patients who underwent radiofrequency catheter ablation (RFA) of AF.

METHODS

In this registry, 493 consecutive patients (age 62 ± 8 years, 70% male) with paroxysmal (316) or persistent (177) AF who underwent first procedure of RFA were included. A pre-procedural CT scan was obtained in 324 patients (CT group). Antral pulmonary vein isolation was performed in all patients using an open-irrigation-tip catheter with a 3D electroanatomical navigation system. Procedural outcome, including radiological exposure, and clinical outcomes were compared among patients who underwent RFA with (CT group) and without (no CT group) pre-procedural cardiac CT.

RESULTS

Acute PV isolation was obtained in all patients, with a comparable overall complication rate between CT and no CT group (4.3% vs 3%, p = 0.7). No differences were observed about mean duration of the procedure (231 ± 60 vs 233 ± 58 min, p = 0.7) and fluoroscopy time (13 ± 10 vs 13 ± 8 min, p = 0.6) among groups. Cumulative radiation dose resulted significantly higher in the CT group compared with no CT group (8.9 ± 24 vs 4.8 ± 15 mSv, P = 0.02). At 1 year, freedom from AF/atrial tachycardia were comparable among groups (CT group, 227/324 (70%), vs no CT group,119/169 (70%), p = ns).

CONCLUSIONS

Pre-procedural CT does not improve safety and efficacy of AF ablation, increasing significantly the cumulative radiological exposure.

Safety and Effectiveness of a Novel Fluoroless Transseptal Puncture Technique for Lead-free Catheter Ablation: A Case Series

Increasing awareness of the health risks associated with the exposure of patients and staff in the catheterization laboratory to radiation has encouraged the pursuit of efforts to reduce the use of fluoroscopy during catheter ablation procedures. Although nonfluoroscopic guidance of ablation catheters has been previously described, transseptal access is still perceived as the last remaining barrier to completely fluoroless ablations. This study examined the safety and effectiveness of transseptal puncture and radiofrequency (RF) catheter ablation using a completely fluoroless approach. Three hundred eighty-two consecutive cases that had undergone completely nonfluoroscopic RF catheter ablation were evaluated. Ablation procedures were performed for atrial fibrillation, atrial flutter, atrioventricular reentry tachycardia, and pulmonary vein complex/ventricular tachycardia. Transseptal puncture and RF ablation were conducted under three-dimensional electroanatomic mapping and intracardiac echocardiography image guidance. Fluoroless transseptal puncture and catheter ablation were completed successfully in all cases, with no intraoperative complications. One patient required minimal use of fluoroscopy to visualize sheath advancement through an existing inferior vena cava filter. Procedural time was approximately 2.2 hours from transvenous access until case conclusion; transseptal access was obtained within 28 minutes of procedure initiation. Arrhythmia was found to recur in 27% of cases on average three months after the procedure. We demonstrate the safety and effectiveness of a completely fluoroless transseptal puncture and RF ablation technique that eliminates radiation exposure and enables complex electrophysiology procedures to be performed in a lead-free environment.

Vascular Inflammation in Subclinical Atherosclerosis Detected by Hybrid PET/MRI

BACKGROUND

Atherosclerosis is a chronic inflammatory disease, but data on arterial inflammation at early stages is limited.

OBJECTIVES

The purpose of this study was to characterize vascular inflammation by hybrid ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/magnetic resonance imaging (PET/MRI).

METHODS

Carotid, aortic, and ilio-femoral ¹⁸F-FDG PET/MRI was performed in 755 individuals (age 40 to 54 years; 83.7% men) with known plaques detected by 2-/3-dimensional vascular ultrasound and/or coronary calcification in the PESA (Progression of Early Subclinical Atherosclerosis) study. The authors evaluated the presence, distribution, and number of arterial inflammatory foci (increased ¹⁸F-FDG uptake) and plaques with or without inflammation (coincident ¹⁸F-FDG uptake).

RESULTS

Arterial inflammation was present in 48.2% of individuals (24.4% femorals, 19.3% aorta, 15.8% carotids, and 9.3% iliacs) and plaques in 90.1% (73.9% femorals, 55.8% iliacs, and 53.1% carotids). ¹⁸F-FDG arterial uptakes and plaques significantly increased with cardiovascular risk factors (p < 0.01). Coincident ¹⁸F-FDG uptakes were present in 287 of 2,605 (11%) plaques, and most uptakes were detected in plaque-free arterial segments (459 of 746; 61.5%). Plaque burden, defined by plaque presence, number, and volume, was significantly higher in individuals with arterial inflammation than in those without (p < 0.01). The number of plaques and ¹⁸F-FDG uptakes showed a positive albeit weak correlation (r = 0.25; p < 0.001).

CONCLUSIONS

Arterial inflammation is highly prevalent in middle-aged individuals with known subclinical atherosclerosis. Large-scale multiterritorial PET/MRI allows characterization of atherosclerosis-related arterial inflammation and demonstrates ¹⁸F-FDG uptake in plaque-free arterial segments and, less frequently, within plaques. These findings suggest an arterial inflammatory state at early stages of atherosclerosis. (Progression of Early Subclinical Atherosclerosis [PESA]; NCT01410318).

Impact of Slice Thickness on the Predictive Value of Lung Cancer Screening Computed Tomography in the Evaluation of Coronary Artery Calcification

Background

Image reconstruction thickness may impact quantitative coronary artery calcium scoring (CACS) from lung cancer screening computed tomography (LCSCT), limiting its application in practice.

Methods and Results

We evaluated Agatston‐based quantitative CACS from 1.25‐mm LCSCT and cardiac computed tomography for agreement in 87 patients. We then evaluated Agatston‐based quantitative CACS from 1.25‐, 2.5‐, and 5.0‐mm slice thickness LCSCT for agreement in 258 patients. Secondary analysis included the impact of slice thickness on predictive value of 4‐year outcomes. Median age of patients who underwent 1.25‐mm LCSCT and cardiac computed tomography was 63 years (interquartile interval, 57, 68). CACS from 1.25‐mm LCSCT and cardiac computed tomography demonstrated a strong Pearson correlation, R=0.9770 (0.965, 0.985), with good agreement. The receiver operating characteristic curve areas under the curve for cardiac computed tomography and LCSCT were comparable at 0.8364 (0.6628, 1.01) and 0.8208 (0.6431, 0.9985), respectively (P=0.733). Median age of patients who underwent LCSCT with 3 slice thicknesses was 66 years (interquartile interval, 63, 73). Compared with CACS from 1.25‐mm scans, CACS from 2.5‐ and 5.0‐mm scans demonstrated strong Pearson correlations, R=0.9949 (0.9935, 0.996) and R=0.9478 (0.9338, 0.959), respectively, though bias was largely negative for 5.0‐mm scans. Receiver operating characteristic curve areas under the curve for 1.25‐, 2.5‐, and 5.0‐mm scans were comparable at 0.7040 (0.6307, 0.7772), 0.7063 (0.6327, 0.7799), and 0.7194 (0.6407, 0.7887), respectively (P=0.6487). When using individualized high‐risk thresholds derived from respective receiver operating characteristic curves, all slice thicknesses demonstrated similar prognostic value.

Conclusions

Slice thickness is an important consideration when interpreting Agatston CACS from LCSCTs. Despite the absence of ECG gating, it appears reasonable to report CACS from either 1.25‐ or 2.5‐mm slice thickness LCSCT to help stratify cardiovascular risk. Conversely, 5.0‐mm scans largely underidentify calcium, limiting practical use within the established CACS values used to categorize cardiovascular risk.

Coronary computed tomography angiography using model-based iterative reconstruction algorithms in the detection of significant coronary stenosis: how the plaque type influences the diagnostic performance

Purpose

To evaluate the ability of coronary computed tomography angiography (CCTA) with model-based iterative reconstruction (MBIR) algorithm in detecting significant coronary artery stenosis compared with invasive coronary angiography (ICA).

Material and methods

We retrospectively identified 55 patients who underwent CCTA using the MBIR algorithm with evidence of at least one significant stenosis (≥ 50%) and an ICA within three months. Patients were stratified based on calcium score; stenoses were classified by type and by coronary segment involved. Dose-length-product was compared with the literature data obtained with previous reconstruction algorithms. Coronary artery stenosis was estimated on ICAs based on a qualitative method.

Results

CCTA data were confirmed by ICA in 89% of subjects, and in 73% and 94% of patients with CS < 400 and ≥ 400, respectively. ICA confirmed 81% of calcific stenoses, 91% of mixed, and 67% of soft plaques. Both the dose exposure of patients with prospective acquisition (34) and the exposure of the whole population were significantly lower than the standard of reference (p < 0.001 and p = 0.007).

Conclusions

CCTA with MBIR is valuable in detecting significant coronary artery stenosis with a solid reduction of radiation dose. Diagnostic performance was influenced by plaque composition, being lower compared with ICA for patients with lower CAC score and soft plaques; the visualisation of an intraluminal hypodensity could cause false positives, particularly in D1 and MO segments.

Reduction in radiation exposure in cardiovascular computed tomography imaging: results from the PROspective multicenter registry on radiaTion dose Estimates of cardiac CT angIOgraphy iN daily practice in 2017 (PROTECTION VI)

Aims

Advances of cardiac computed tomography angiography (CTA) have been developed for dose reduction, but their efficacy in clinical practice is largely unknown. This study was designed to evaluate radiation dose exposure and utilization of dose-saving strategies for contrast-enhanced cardiac CTA in daily practice.

Methods and results

Sixty one hospitals from 32 countries prospectively enrolled 4502 patients undergoing cardiac CTA during one calendar month in 2017. Computed tomography angiography scan data and images were analysed in a central core lab and compared with a similar dose survey performed in 2007. Linear regression analysis was performed to identify independent predictors associated with dose. The most frequent indication for cardiac CTA was the evaluation of coronary artery disease in 89% of patients. The median dose-length product (DLP) of coronary CTA was 195 mGy*cm (interquartile range 110-338 mGy*cm). When compared with 2007, the DLP was reduced by 78% (P < 0.001) without an increase in non-diagnostic coronary CTAs (1.7% in 2007 vs. 1.9% in 2017 surveys, P = 0.55). A 37-fold variability in median DLP was observed between the hospitals with lowest and highest DLP (range of median DLP 57-2090 mGy*cm). Independent predictors for radiation dose of coronary CTA were: body weight, heart rate, sinus rhythm, tube voltage, iterative image reconstruction, and the selection of scan protocols.

Conclusion

This large international radiation dose survey demonstrates considerable reduction of radiation exposure in coronary CTA during the last decade. However, the large inter-site variability in radiation exposure underlines the need for further site-specific training and adaptation of contemporary cardiac scan protocols.

Evaluation of a new ultralow-dose radiation protocol for electrophysiological device implantation: A near-zero fluoroscopy approach for device implantation

BACKGROUND

Radiation is one of the main hazards of electrophysiological device implantation, and insertion of cardiac resynchronization therapy (CRT) devices in particular is associated with high radiation doses.

OBJECTIVE

The purpose of this study was to evaluate the impact of a new ultralow-dose radiation protocol on radiation doses, success rate, and safety of electrophysiological device implantations.

METHODS

In 2018, we established a new ultralow-dose radiation protocol (reduced pulse width, increased thickness of minimum copper filters, reduced detector entrance dose, reduced pulse rate, optimized image postprocessing settings) for de novo device implantation at our hospital. A total of 1173 patients (11% single-chamber devices, 69% dual-chamber devices, 20% CRT devices) were analyzed. Five hundred twelve patients (44%) in the ultralow-dose group were compared to 661 patients (66%) treated during 2017 with a conventional low-dose protocol.

RESULTS

With the ultralow-dose radiation protocol, effective doses could be reduced by 59% (median 0.25 [interquartile range: 0.11-0.63] vs median 0.10 [interquartile range: 0.03-0.28] mSv; P <.0001) per procedure without a significant change in procedure time (P = .5). This dose reduction could be achieved without decreasing procedure success (P = 1) or increasing complication rate (P = .8). Male gender, higher body mass index, increased procedure and fluoroscopy times, and use of the conventional radiation protocol were independent predictors of higher radiation doses in multivariate regression analysis.

CONCLUSION

By establishing a new ultralow-dose radiation protocol, we could significantly decrease radiation exposure, reaching the lowest radiation doses for electrophysiological device implantation reported to date.

Fluoroscopy reduction during device implantation by using three-dimensional navigation. A single-center experience

BACKGROUND AND OBJECTIVES

The use of nonfluoroscopic three-dimensional electroanatomic mapping (3DM) systems reduces radiation exposure during ablation procedures. In this study, we sought to determine the value of 3DM during routine device implant procedures.

METHODS

Seventy nonselected patients underwent implantation of a single chamber, dual chamber, or biventricular device guided by Ensite (Abbott Laboratories) to limit fluoroscopy use and compared with 70 consecutive patients, who underwent matching procedures with standard fluoroscopy use (FL) in the period immediately preceding the use of 3DM. The venous anatomy, right atrium, and ventricle and coronary sinus were mapped with 0.035 inch J-wire, quadripolar catheter, and/or angioplasty wire. The leads were advanced under real-time visualization in Ensite.

RESULTS

3DM reduced both fluoroscopy time and dose. Median fluoroscopy time for FL vs 3DM was 5.5 minutes (interquartile range [IQR]: 3.8-8.1) vs 0.9 minutes (IQR: 0.6-1.9) (P < .001) for single chamber devices, 6.3 minutes (IQR: 5.1-7.9) vs 3.3 minutes (IQR: 1.9-4) (P < .001) for dual-chamber devices, and 28.6 minutes (IQR: 19.6-36.2) to 14.7 minutes (IQR: 10.4-22.3) (P = .009) for biventricular devices, respectively. The median air kerma for FL vs 3DM was 15.4 mGy (IQR: 8.1-30.2) vs 4 mGy (IQR: 1.8-8) (P < .001) for single chamber devices, 16 mGy (IQR: 12-18.5) to 9.4 mGy (IQR: 7.5-11.3) (P = .001) for dual-chamber devices, and 324 mGy (IQR: 143-668.7) to 115 mGy (IQR:77-204) (P = .014) for biventricular devices, respectively. There were no procedural complications. At 3-month follow-up, there was no difference in voltage threshold measurements between the groups.

CONCLUSION

The use of 3DM leads to significantly reduced fluoroscopy time and fluoroscopy dose during routine device implantation.

Flexible Modeling of the Association Between Cumulative Exposure to Low-Dose Ionizing Radiation From Cardiac Procedures and Risk of Cancer in Adults With Congenital Heart Disease

Adults with congenital heart disease are increasingly being exposed to low-dose ionizing radiation (LDIR) from cardiac procedures. In a recent study, Cohen et al. (Circulation. 2018;137(13):1334-1345) reported an association between increased LDIR exposure and cancer incidence but did not explore temporal relationships. Yet, the impact of past exposures probably accumulates over years, and its strength may depend on the amount of time elapsed since exposure. Furthermore, LDIR procedures performed shortly before a cancer diagnosis may have been ordered because of early symptoms of cancer, raising concerns about reversal causality bias. To address these challenges, we combined flexible modeling of cumulative exposures with competing-risks methodology to estimate separate associations of time-varying LDIR exposure with cancer incidence and all-cause mortality. Among 24,833 patients from the Quebec Congenital Heart Disease Database, 602 had incident cancer and 500 died during a follow-up period of up to 15 years (1995-2010). Initial results suggested a strong association of cancer incidence with very recent LDIR exposures, likely reflecting reverse causality bias. When exposure was lagged by 2 years, an increased cumulative LDIR dose from the previous 2-6 years was associated with increased cancer incidence, with a stronger association for women. These results illustrate the importance of accurate modeling of temporal relationships between time-varying exposures and health outcomes.