Discordance between 2D and 4D flow in the assessment of pulmonary regurgitation severity: a right ventricular remodeling follow-up study.

OBJECTIVES: Pulmonary regurgitation (PR) is common in adult congenital heart disease (ACHD). 2D phase contrast MRI is the reference method for the quantification of PR and helps in the decision of pulmonary valve replacement (PVR). 4D flow MRI can be an alternative method to estimate PR but more validation is still needed. Our purpose was to compare 2D and 4D flow in PR quantification using the degree of right ventricular remodeling after PVR as the reference standard. METHODS: In 30 adult patients with a pulmonary valve disease recruited between 2015 and 2018, PR was assessed using both 2D and 4D flow. Based on the clinical standard of care, 22 underwent PVR. The pre PVR estimate of PR was compared using the post-operative decrease in right ventricle end-diastolic volume on follow-up exam as reference. RESULTS: In the overall cohort, regurgitant volume (Rvol) and regurgitant fraction (RF) of PR measured by 2D and 4D flow were well correlated but with moderate agreement in the overall cohort (r = 0.90, mean diff. -14 ± 12.5 mL; and r = 0.72, mean diff. -15 ± 13%; all p < 0.0001). Correlations between Rvol estimates and right ventricle end-diastolic volume decrease after PVR was higher with 4D flow (r = 0.80, p < 0.0001) than with 2D flow (r = 0.72, p < 0.0001). CONCLUSIONS: In ACHD, PR quantification from 4D flow better predicts post-PVR right ventricle remodeling than that from 2D flow. Further studies are needed to evaluate the added value of this 4D flow quantification for guiding replacement decision. KEY POINTS: • Using 4D flow MRI allows a better quantification of pulmonary regurgitation in adult congenital heart disease than 2D flow when taking right ventricle remodeling after pulmonary valve replacement as a reference. • A plane positioned perpendicular to the ejected flow volume as allowed by 4D flow provides better results to estimate pulmonary regurgitation.

4D flow magnetic resonance imaging to assess right ventricular outflow tract in patients undergoing transcatheter pulmonary valve replacement.

INTRODUCTION AND OBJECTIVES: Magnetic resonance imaging (MRI) including 4D flow is used before percutaneous pulmonary valve implantation (PPVI). As PPVI is limited by the size of the right ventricular outflow tract (RVOT), accurate sizing is needed to plan the intervention. The aim of this study was to compare different MRI modalities and invasive angiography to balloon sizing of RVOT. METHODS: Single-center prospective study of patients who underwent PPVI for isolated pulmonary regurgitation assessed by 4D flow MRI, 3D steady-state free precession/gradient echo (3D SSFP/GRE) and contrast magnetic resonance angiography. Balloon sizing was considered as the reference. RESULTS: A total of 23 adults were included (mean age, 38.4±12.5 years). Eighteen patients underwent successful primary PPVI. The average of the narrowest RVOT diameter was 25.4±4.3 mm by balloon sizing. Compared to balloon sizing, RVOT diameters were better correlated when estimated by systolic 4D flow MRI (r=0.89, P<.001) than by diastolic 4D flow MRI (r=0.71, P <.001), 3D contrast magnetic resonance angiography (r=0.73; P <.001) and 3D SSFP/GRE (r=0.50; P=.04) and was not significantly correlated when estimated by 2D in diastole and systole. The mean difference between systolic 4D flow MRI and balloon sizing was 0.2 mm (95%CI, -3.5 to 3.9 mm), whereas it was wider with other techniques. CONCLUSIONS: Beyond the quantification of pulmonary valve regurgitation, 4D flow allows accurate estimation of RVOT diameters, especially in systole, which is fundamental before planning PPVI.

Tuberculosis of the Heart: A Diagnostic Challenge.

Tuberculosis of the heart is relatively rare and presents a significant diagnostic difficulty for physicians. It is the leading cause of death from infectious illness. It is one of the top 10 leading causes of death worldwide, with a disproportionate impact in low- and middle-income nations. The radiologist plays a pivotal role as CMR is a non-invasive radiological method that can aid in identifying potential overlap and differential diagnosis between tuberculosis, mass lesions, pericarditis, and myocarditis. Regardless of similarities or overlap in observations, the combination of clinical and certain particular radiological features, which are also detected by comparison to earlier and follow-up CMR scans, may aid in the differential diagnosis. CMR offers a significant advantage over echocardiography for detecting, characterizing, and assessing cardiovascular abnormalities. In conjunction with clinical presentation, knowledge of LGE, feature tracking, and parametric imaging in CMR may help in the early detection of tuberculous myopericarditis and serve as a surrogate for endomyocardial biopsy resulting in a quicker diagnosis and therapy. This article aims to explain the current state of cardiac tuberculosis, the diagnostic utility of CMR in tuberculosis (TB) patients, and offer an overview of the various imaging and laboratory procedures used to detect cardiac tuberculosis.

Left ventricular diastolic early and late filling quantified from 4D flow magnetic resonance imaging.

PURPOSE: The purpose of this study was to investigate the value of 4D flow MRI for mitral filling measurements, using transthoracic echocardiography (TTE) and 2D flow MRI as references, as well as identify relationships with age and left ventricle (LV) remodeling in healthy volunteers. MATERIAL AND METHODS: Fifty healthy volunteers (22 men, 28 women; mean age, 51.3 ± 16.9 [SD] years; age range: 20-80 years) prospectively underwent TTE and MRI on the same day. 4D flow volume acquisition was done at 3T with reconstructed spatial/temporal resolutions: 1 × 1.48 × 2.38 mm3/34 ms. Early (E) and late (A) flow rate and maximal velocity peaks were measured from 4D flow data with three strategies: static planes at 1) the mitral valve leaflets tip (4DLT) and 2) annulus (4Dann); and 3) while tracking the annulus through time (4Dtrack). RESULTS: 4DLT- and 4Dtrack-derived E/A ratios were in good agreement with 2D flow and TTE estimates with a superiority over maximal velocities (4DLT: r = 0.71 and r = 0.66; 4Dtrack: r = 0.74 and r = 0.71, respectively) of flow rates (4DLT: r = 0.89 and 0.72; 4Dtrack: r = 0.91 and 0.76, respectively). Measurements of 4DLT and 4Dtrack were highly reproducible (ICC = 0.89 and 0.95, respectively) and significantly correlated with age and LV remodeling (4DLT: r = -0.76 and ρ = -0.49; 4Dtrack: r = -0.79 and ρ = -0.51, respectively). CONCLUSION: E/A ratio can be accurately measured using 4D flow MRI either at a fixed mitral leaflet tip location or through annulus plane time-resolved tracking.

Changes in QTc interval after hydroxychloroquine therapy in patients with COVID-19 infection: a large, retrospective, multicentre cohort study.

OBJECTIVE: To evaluate the extent of hydroxychloroquine-induced corrected QT (QTc) prolongation and its relation to COVID-19 infection severity and incidence of polymorphic ventricular arrhythmias and sudden arrhythmic deaths. DESIGN: A large-scale cohort study with retrospective analysis of baseline and on-therapy QT interval corrected using Bazett and Fridericia formulas. SETTING: A multicentre study involving eight secondary and tertiary care hospitals of the Abu Dhabi Health Services Company (SEHA), United Arab Emirates. PARTICIPANTS: 2014 patients consecutively admitted with PCR-confirmed SARS-CoV-2 infection between 1 March 2020 and 1 June 2020. INTERVENTIONS: Treatment with hydroxychloroquine alone or in combination with azithromycin for at least 24 hours and with a baseline ECG and at least one ECG after 24 hours of therapy. MAIN OUTCOME MEASURES: Maximal QTc interval prolongation and its relationship to clinical severity, polymorphic ventricular tachycardia and sudden arrhythmic death while on treatment. RESULTS: The baseline QTc(Bazett) was 427.6±25.4 ms and the maximum QTc(Bazett) during treatment was 439.2±30.4 ms (p<0.001). Severe QTc prolongation (QTc ≥500 ms) was observed in 1.7%-3.3% of patients (Fridericia and Bazett, respectively). There were no cases of polymorphic ventricular arrhythmia or hydroxychloroquine-related arrhythmic death. QTc prolongation was more pronounced in combination therapy compared with hydroxychloroquine alone (22.2 ms vs 11.0 ms, p<0.001) and in patients with higher COVID-19 clinical severity (asymptomatic: 428.4±25.4 ms, severe COVID-19 infection: 452.7±35.7 ms, p<0.001). The overall in-hospital mortality was 3.97% and deceased patients had longer on-therapy QTc(Bazett) than survivors (459.8±21.4 ms vs 438.4±29.9 ms, p<0.001). CONCLUSIONS: The incidence of severe QTc prolongation with hydroxychloroquine was low and not associated with ventricular arrhythmia. The safety concerns surrounding the use of hydroxychloroquine may have been overestimated; however, caution should be exercised when using hydroxychloroquine in patients with risk factors for QT prolongation.

Closed-form approximation of symmetric thin-film multi-layer plasmonic dispersion equation solutions.

An original asymptotic method is developed and used to find closed-form approximations to the symmetric thin-film three- and multi-layer plasmonic dispersion equations. Closed-form analysis of three-layer metal-insulator-metal (MIM: "M" is metal and "I" is insulator) and IMI devices shows a complementary physics underpinning their properties. Analysis of multi-layer symmetric devices, considered for a seven-layer MIMIMIM example, uncovers a remarkable departure from the physics governing MIM and IMI features. Multi-layer propagation length and attenuation are determined by proximity, in the space of cladding thickness and wavelength, to singularities that exist in the limit of vanishing imaginary part of the cladding dielectric constant. Exploitation of this phenomenon will expand the development of a broader range of thin-film applications in optoelectronics.

A new era in gated myocardial perfusion imaging: Feasibility of data-driven cardiac contraction gating with multiple pinhole CZT SPECT.

BACKGROUND: We previously validated the use of a data-driven cardiac respiratory-motion (RM) correction method (REGAT) applicable to CZT SPECT myocardial perfusion imaging (MPI). In this study, we adapted the same process used with REGAT for RM to generate data-driven cardiac contraction triggers and corresponding cardiac contraction-gated SPECT studies (GSPECT-DD). We aimed to study its feasibility and compare its performances to GSPECT studies generated with ECG monitor-based triggers (GSPECT-ECG). METHODS: We included seven non-consecutive randomly chosen patients addressed for 1-day 99mTc-Tetrofosmin stress/rest MPI acquired with multi-pinhole CZT SPECT. We studied the degree of agreement between GSPECT-DD and GSPECT-ECG for the classification of acquired images into the 16 categories of mean cardiac cycle, and compared between the two methods the cine image quality and global LV systolic function of reconstructed studies. RESULTS: We found almost perfect agreement between cardiac contraction triggers generated with data-driven and ECG monitor-based methods. As compared to GSPECT-ECG, GSPECT-DD provided comparable and well-correlated LV global systolic function parameters and similar cine image quality at both stress and rest. CONCLUSIONS: Data-driven cardiac contraction gating using REGAT is feasible with low-dose and high-dose MPI CZT SPECT. It provides GSPECT-DD studies comparable to GSPECT-ECG.

Semiconductor-based plasmonic interferometers for ultrasensitive sensing in a terahertz regime.

A robust plasmonic semiconductor-based Mach-Zehnder interferometer (MZI), which consists of a semiconductor layer with a microslit flanked by two identical microgrooves, is proposed and investigated for the terahertz sensing. The microgrooves reflect the surface plasmon polariton waves toward the microslit, where they interfere with the transmitted terahertz wave. The interference pattern is determined by the permittivities of the sensing material and semiconductor (i.e., temperature dependent), making the structure useful for the refractive index (RI) and temperature detection. A quantitative theoretical model is also developed for performance prediction and validated with a finite element method. The numerical results show that the Mach-Zehnder interferometer sensor possesses an RI sensitivity as high as 140000 nm/RIU (or 0.42 THz/RIU) and a relative intensity sensitivity of 1200%RIU-1. In addition, a temperature sensitivity of 1470 nm/K (or 4.7×10-3 THz/K) is determined. Theoretical calculations indicate that the further improvement in sensing performance is still possible through optimization of the structure. The proposed sensing scheme may pave the way for applications in terahertz sensing and integrated terahertz circuits.