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Aims Cardiovascular magnetic resonance (CMR) with late-gadolinium enhancement (LGE) is increasingly being used in hypertrophic cardiomyopathy (HCM) for diagnosis, risk stratification, and monitoring. However, recent data demonstrating brain gadolinium deposits have raised safety concerns. We developed and validated a machine-learning (ML) method that incorporates features extracted from cine to identify HCM patients without fibrosis in whom gadolinium can be avoided. Methods and results An XGBoost ML model was developed using regional wall thickness and thickening, and radiomic features of myocardial signal intensity, texture, size, and shape from cine. A CMR dataset containing 1099 HCM patients collected using 1.5T CMR scanners from different vendors and centres was used for model development (n =882) and validation (n =217). Among the 2613 radiomic features, we identified 7 features that provided best discrimination between +LGE and −LGE using 10-fold stratified cross-validation in the development cohort. Subsequently, an XGBoost model was developed using these radiomic features, regional wall thickness and thickening. In the independent validation cohort, the ML model yielded an area under the curve of 0.83 (95% CI: 0.77–0.89), sensitivity of 91%, specificity of 62%, F1-score of 77%, true negatives rate (TNR) of 34%, and negative predictive value (NPV) of 89%. Optimization for sensitivity provided sensitivity of 96%, F2-score of 83%, TNR of 19% and NPV of 91%; false negatives halved from 4% to 2%. Conclusion An ML model incorporating novel radiomic markers of myocardium from cine can rule-out myocardial fibrosis in one-third of HCM patients referred for CMR reducing unnecessary gadolinium administration. [ABSTRACT FROM AUTHOR]

Background: The role of portable high-efficiency particulate air (HEPA) filters for supplemental aerosol mitigation during exercise testing is unknown and might be relevant during COVID-19 pandemic.Research Question: What is the effect of portable HEPA filtering on aerosol concentration during exercise testing and its efficiency in reducing room clearance time in a clinical exercise testing laboratory?Study Design and Methods: Subjects were six healthy volunteers aged 20 to 56 years. In the first experiment, exercise was performed in a small tent with controlled airflow with the use of a stationary cycle, portable HEPA filter with fume hood, and particle counter to document aerosol concentration. Subjects performed a four-stage maximal exercise test that lasted 12 min plus 5 min of pretest quiet breathing and 3 min of active recovery. First, they exercised without mitigation then with portable HEPA filter running. In a separate experiment, room aerosol clearance time was measured in a clinical exercise testing laboratory by filling it with artificially generated aerosols and measuring time to 99.9% aerosol clearance with heating, ventilation, and air conditioning (HVAC) only or HVAC plus portable HEPA filter running.Results: In the exercise experiment, particle concentrations reached 1,722 ± 1,484/L vs 96 ± 124/L (P < .04) for all particles (>0.3 μm), 1,339 ± 1,281/L vs 76 ± 104/L (P < .05) for smaller particles (0.3 to 1.0 μm), and 333 ± 209/L vs 17 ± 19/L (P < .01) for larger particles (1.0 to 5.0 μm) at the end of the protocol in a comparison of mitigation vs portable HEPA filter. Use of a portable HEPA filter in a clinical exercise laboratory clearance experiment reduced aerosol clearance time 47% vs HVAC alone.Interpretation: The portable HEPA filter reduced the concentration of aerosols generated during exercise testing by 96% ± 2% for all particle sizes and reduced aerosol room clearance time in clinical exercise testing laboratories. Portable HEPA filters therefore might be useful in clinical exercise testing laboratories to reduce the risk of COVID-19 transmission. [ABSTRACT FROM AUTHOR]

Background: Left atrial (LA) fibrosis is thought to be a substrate for atrial fibrillation (AF) and can be quantified by late gadolinium enhancement magnetic resonance imaging (LGE‐MRI). Fibrosis formation in LA is a dynamic process and may either progress or regress following AF ablation. We examined the impact of postablation progression in LA fibrosis on AF recurrence. Methods: LA enhancement in LGE‐MRI was quantified in 127 consecutive patients who underwent first time AF ablation. Serial LGE‐MRIs were done prior to AF ablation, 3 months postablation and at least 12 months after second LGE‐MRI. Transient postablation lesion (TL) was defined as atrial enhancement caused by ablation lesions that was detected on the first (3 month) but not on the second postablation LGE‐MRI. New fibrosis (NF) was defined as atrial enhancement detected on the most recent LGE‐MRI, at least 15 months after the ablation procedure. AF recurrence and its correlation with TL and NF was assessed in all patients during the follow‐up period. Results: An increase of 1% NF increased the chance of postablation AF recurrence by 3% (hazard ratio [HR] 1.03, 95% CI 1‐1.06, P =.05). TL had no significant impact on recurrence (P =.057). After adjusting for cardiovascular risk factors, HR increased as NF became greater. Greater volume of NF (≥21%) corresponded with lower arrhythmia‐free survival (37% vs 62%, P =.01). Conclusion: NF formation postablation of AF is a novel marker of long‐term procedural outcome. Extensive NF is associated with significantly higher risk of atrial arrhythmia recurrence. [ABSTRACT FROM AUTHOR]

Aims: We aimed to assess the effect of cardiac resynchronization on left ventricular (LV) function, volumes, geometry, and mechanics in order to demonstrate reverse remodelling using cardiac magnetic resonance (CMR) with resynchronization on.Methods and Results: New York Heart Association (NYHA) Class II-III patients on optimal medical therapy with LV ejection fraction (LVEF) ≤35%, and complete LBBB with broad QRS (>150 ms) were prospectively recruited. Cardiac magnetic resonance examination was performed at baseline and at 6-month follow-up, applying both biventricular and AOO pacing. The following data were measured: conventional CMR parameters, remodelling indices, global longitudinal, circumferential, radial strain, global dyssynchrony [mechanical dispersion (MD) defined as the standard deviation of time to peak longitudinal/circumferential strain in 16 LV segments], and regional dyssynchrony (maximum differences in time between peak septal and lateral transversal displacement). Thirteen patients (64 ± 7 years, 38% male) were enrolled. Comparing the baseline and follow-up CMR parameters measured during biventricular pacing, significant increase in LVEF, and decrease in LV end-diastolic volume index (LVEDVi) and LV end-systolic volume index (LVESVi) were found. Left ventricular remodelling indices, global longitudinal, circumferential, and radial strain values showed significant improvement. Circumferential MD decreased (20.5 ± 5.5 vs. 13.4 ± 3.4, P < 0.001), while longitudinal MD did not change. Regional dyssynchrony drastically improved (362 ± 96 vs. 104 ± 66 ms, P < 0.001). Applying AOO pacing resulted in an immediate deterioration in LVEF, LVESVi, circumferential strain, global and regional dyssynchrony.Conclusion: Cardiac magnetic resonance imaging during biventricular pacing is feasible and enables a more precise quantification of LV function, morphology, and mechanics. As a result, it may contribute to a better understanding of the effects of resynchronization therapy and might improve responder rate in the future. [ABSTRACT FROM AUTHOR]

Introduction: Left atrial (LA) volume and function are related to success of atrial fibrillation (AF) ablation. However, the relationship between LA structure and function is not well understood. Magnetic resonance imaging (MRI) is a non-invasive method to assess LA fibrosis and LA function. Hypothesis: Our goal is to evaluate the left atrial functional recovery after successful atrial fibrillation ablation procedure focusing on the ablation lesion sets. Methods: CMR scans were performed in 55 AF patients (66.1±10.5 years) without AF recurrence, at three time points: prior to ablation procedure, in the acute post-ablation period (<48 hours) and at 3 months follow-up. We categorized patients into three groups according to the ablation lesion sets: Gr1{n=11} pulmonary vein isolation only (PVI); Gr2{n=33} PVI, roof line (RL) and posterior wall homogenisation (PH), Gr3{n=11} PVI, RL, PH and additional anterior wall fibrosis homogenization (AH). Maximum (maxLAV), minimum (minLAV) and pre-atrial contraction LA volumes (pre-aLAV) were measured according to the biplane area-length method with CMR. Total, passive and active LA ejection fractions (LAEF) were calculated, and LA fibrosis was quantified using late-gadolinium enhancement images. Results: Comparing the three groups, baseline pre-ablation atrial volumes and function were not significantly different among groups, but Gr3 had higher pre-ablation LA fibrosis% (Gr1 vs Gr2 vs Gr3 11.5±5.1% vs 11.7±4.1% vs 14.8±5.9% p<0.05). In the acute phase, the lowest total LA-EF was identified in Gr3 (Gr1 vs Gr3 total LAEF: 56.9±16.0% vs 37.2±14.9 p<0.05), but during follow-up no significant difference was identified. After 3 months Gr2 showed functional recovery, and total and also active LAEF was significantly higher compared to the baseline function (Gr3 pre-ablation vs follow-up LAEF: 42.5±12.5 vs 51.1±16.5% p<0.005) (Figure). Conclusions: In patient with posterior wall ablation LA function recovered, and additional left atrial fibrosis homogenization did not decrease LA function significantly at follow-up. [ABSTRACT FROM AUTHOR]