Improved image quality in CT pulmonary angiography using deep learning-based image reconstruction.

We investigated the effect of deep learning-based image reconstruction (DLIR) compared to iterative reconstruction on image quality in CT pulmonary angiography (CTPA) for suspected pulmonary embolism (PE). For 220 patients with suspected PE, CTPA studies were reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASiR-V 30%, 60% and 90%) and DLIR (low, medium and high strength). Contrast-to-noise ratio (CNR) served as the primary parameter of objective image quality. Subgroup analyses were performed for normal weight, overweight and obese individuals. For patients with confirmed PE (n = 40), we further measured PE-specific CNR. Subjective image quality was assessed independently by two experienced radiologists. CNR was lowest for FBP and enhanced with increasing levels of ASiR-V and, even more with increasing strength of DLIR. High strength DLIR resulted in an additional improvement in CNR by 29-67% compared to ASiR-V 90% (p < 0.05). PE-specific CNR increased by 75% compared to ASiR-V 90% (p < 0.05). Subjective image quality was significantly higher for medium and high strength DLIR compared to all other image reconstructions (p < 0.05). In CT pulmonary angiography, DLIR significantly outperforms iterative reconstruction for increasing objective and subjective image quality. This may allow for further reductions in radiation exposure in suspected PE.

Native myocardial T1 mapping: influence of spatial resolution on quantitative results and reproducibility.

Background: Myocardial mapping techniques can be used to quantitatively assess alterations in myocardial tissue properties. This study aims to evaluate the influence of spatial resolution on quantitative results and reproducibility of native myocardial T1 mapping in cardiac magnetic resonance imaging (MRI). Methods: In this cross-sectional study with prospective data collection between October 2019 and February 2020, 50 healthy adults underwent two identical cardiac MRI examinations in the radiology department on the same day. T1 mapping was performed using a MOLLI 5(3)3 sequence with higher (1.4 mm × 1.4 mm) and lower (1.9 mm × 1.9 mm) in-plane spatial resolution. Global quantitative results of T1 mapping were compared between high-resolution and low-resolution acquisitions using paired t-test. Intra-class correlation coefficient (ICC) and Bland-Altman statistics (absolute and percentage differences as means ± SD) were used for assessing test-retest reproducibility. Results: There was no significant difference between global quantitative results acquired with high vs. low-resolution T1 mapping. The reproducibility of global T1 values was good for high-resolution (ICC: 0.88) and excellent for low-resolution T1 mapping (ICC: 0.95, P=0.003). In subgroup analyses, inferior test-retest reproducibility was observed for high spatial resolution in women compared to low spatial resolution (ICC: 0.71 vs. 0.91, P=0.001) and heart rates >77 bpm (ICC: 0.53 vs. 0.88, P=0.004). Apical segments had higher T1 values and variability compared to other segments. Regional T1 values for basal (ICC: 0.81 vs. 0.89, P=0.023) and apical slices (ICC: 0.86 vs. 0.92, P=0.024) showed significantly higher reproducibility in low-resolution compared to high-resolution acquisitions but without differences for midventricular slice (ICC: 0.91 vs. 0.92, P=0.402). Conclusions: Based on our data, we recommend a spatial resolution on the order of 1.9 mm × 1.9 mm for native myocardial T1 mapping using a MOLLI 5(3)3 sequence at 1.5 T particularly in individuals with higher heart rates and women.

Right ventricular dyssynchrony: from load-independent right ventricular function to wall stress in severe pulmonary arterial hypertension.

Right ventricular (RV) dyssynchrony has been related to outcome in pulmonary arterial hypertension. Prospectively, we performed echocardiography with measurement of right ventricular dyssynchrony and pressure-volume loop catheterization in 27 pulmonary arterial hypertension patients. Afterload and diastolic function emerged as determinates of wall stress, which results in dyssynchrony.

Association of right atrial conduit phase with right ventricular lusitropic function in pulmonary hypertension.

Alterations of right atrial (RA) function have emerged as determinants of outcome in pulmonary hypertension (PH). We aimed to clarify the pathophysiological associations of impaired RA conduit function with right ventricular (RV) function in PH. In 51 patients with PH (48 with pulmonary arterial hypertension), RA conduit function was assessed as echocardiographic peak early diastolic strain rate (PEDSR). PEDSR and cardiac magnetic resonance parameters were measured within 24 h of right heart catheterization and generation of pressure-volume loops to assess RV diastolic (RV end-diastolic pressure [EDP] and relaxation [Tau]) and systolic function. Spearman rho correlation and linear regression analysis were used to determine the association of PEDSR with RV function. The impact of PEDSR on time to clinical worsening was assessed using Kaplan-Meier and Cox regression analyses. Median (interquartile range) PEDSR was - 0.56 s - 1 (- 1.08 to - 0.37). Impaired PEDSR was significantly correlated with RV diastolic stiffness [EDP (rho = 0.570; p < 0.001) and Tau (rho = 0.500; p < 0.001)] but not with RV contractility or coupling. In multivariate linear regression including parameters of RV lusitropic and inotropic function, EDP remained independently associated with impaired PEDSR. During a median follow-up of 9 months, 23 patients deteriorated. After multivariate adjustment, PEDSR remained associated with clinical worsening (hazard ratio: 2.85; 95% confidence interval: 1.20-6.78). Altered RV lusitropy is associated with impaired RA conduit phase. PEDSR emerged as a promising, non-invasive, bedside-ready parameter to evaluate RV diastolic function and to predict prognosis in PH.

Right ventricular function correlates of right atrial strain in pulmonary hypertension: a combined cardiac magnetic resonance and conductance catheter study.

The functional relevance of right atrial (RA) function in pulmonary hypertension (PH) remains incompletely understood. The purpose of this study was to explore the correlation of cardiac magnetic resonance (CMR) feature tracking-derived RA phasic function with invasively measured pressure-volume (P-V) loop-derived right ventricular (RV) end-diastolic elastance (Eed) and RV-arterial coupling [ratio of end-systolic elastance to arterial elastance (Ees/Ea)]. In 54 patients with severe PH, CMR was performed within 24 h of diagnostic right heart catheterization and P-V measurements. RA phasic function was assessed by CMR imaging of RA reservoir, passive, and active strain. The association of RA phasic function with indexes of RV function was evaluated by Spearman's rank correlation and linear regression analyses. Median [interquartile range] RA reservoir strain, passive strain, and active strain were 19.5% [11.0-24.5], 7.0% [4.0-12.0], and 13.0% [7.0-18.5], respectively. Ees/Ea was 0.73 [0.48-1.08], and Eed was 0.14 mmHg/mL [0.05-0.22]. RV diastolic impairment [RV end-diastolic pressure (EDP) and Eed] was correlated with RA phasic function, but Ea and Ees were not. In addition, RA phasic function was correlated with inferior vena cava diameter. In multivariate linear regression analysis, adjusting for key P-V loop indexes, Eed and EDP remained significantly associated with RA phasic function. We conclude that RA phasic function is altered in relation to impaired diastolic function of the chronically overloaded right ventricle and contributes to backward venous flow and systemic congestion. These results call for more attention to RA function in the management of patients with PH.NEW & NOTEWORTHY There is growing awareness of the importance of the right atrial (RA)-right ventricular (RV) axis in pulmonary hypertension (PH). Our results uncover alterations in RA phasic function that are related to depressed RV lusitropic function and contribute to backward venous return and systemic congestion in chronic RV overload. Assessment of RA function should be part of the management and follow-up of patients with PH.

Validation of the Tricuspid Annular Plane Systolic Excursion/Systolic Pulmonary Artery Pressure Ratio for the Assessment of Right Ventricular-Arterial Coupling in Severe Pulmonary Hypertension.

BACKGROUND: The ratios of tricuspid annular plane systolic excursion (TAPSE)/echocardiographically measured systolic pulmonary artery pressure (PASP), fractional area change/invasively measured mean pulmonary artery pressure, right ventricular (RV) area change/end-systolic area, TAPSE/pulmonary artery acceleration time, and stroke volume/end-systolic area have been proposed as surrogates of RV-arterial coupling. The relationship of these surrogates with the gold standard measure of RV-arterial coupling (invasive pressure-volume loop-derived end-systolic/arterial elastance [Ees/Ea] ratio) and RV diastolic stiffness (end-diastolic elastance) in pulmonary hypertension remains incompletely understood. We evaluated the relationship of these surrogates with invasive pressure-volume loop-derived Ees/Ea and end-diastolic elastance in pulmonary hypertension. METHODS: We performed right heart echocardiography and cardiac magnetic resonance imaging 1 day before invasive measurement of pulmonary hemodynamics and single-beat RV pressure-volume loops in 52 patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. The relationships of the proposed surrogates with Ees/Ea and end-diastolic elastance were evaluated by Spearman correlation, multivariate logistic regression, and receiver operating characteristic analyses. Associations with prognosis were evaluated by Kaplan-Meier analysis. RESULTS: TAPSE/PASP, fractional area change/mean pulmonary artery pressure, RV area change/end-systolic area, and stroke volume/end-systolic area but not TAPSE/pulmonary artery acceleration time were correlated with Ees/Ea and end-diastolic elastance. Of the surrogates, only TAPSE/PASP emerged as an independent predictor of Ees/Ea (multivariate odds ratio: 18.6; 95% CI, 0.8-96.1; P=0.08). In receiver operating characteristic analysis, a TAPSE/PASP cutoff of 0.31 mm/mm Hg (sensitivity: 87.5% and specificity: 75.9%) discriminated RV-arterial uncoupling (Ees/Ea <0.805). Patients with TAPSE/PASP <0.31 mm/mm Hg had a significantly worse prognosis than those with higher TAPSE/PASP. CONCLUSIONS: Echocardiographically determined TAPSE/PASP is a straightforward noninvasive measure of RV-arterial coupling and is affected by RV diastolic stiffness in severe pulmonary hypertension. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT03403868.

Impaired right ventricular lusitropy is associated with ventilatory inefficiency in pulmonary arterial hypertension.

Cardiopulmonary exercise testing (CPET) is an important tool for assessing functional capacity and prognosis in pulmonary arterial hypertension (PAH). However, the associations of CPET parameters with the adaptation of right ventricular (RV) function to afterload remain incompletely understood.In this study, 37 patients with PAH (idiopathic in 31 cases) underwent single-beat pressure-volume loop measurements of RV end-systolic elastance (Ees), arterial elastance (Ea) and diastolic elastance (Eed). Pulmonary arterial stiffness was assessed by magnetic resonance imaging. The results were correlated to CPET variables. The predictive relevance of RV function parameters for clinically relevant ventilatory inefficiency, defined as minute ventilation/carbon dioxide production (V' E/V' CO2 ) slope >48, was evaluated using logistic regression analysis.The median (interquartile range) of the V' E/V' CO2 slope was 42 (32-52) and the V' E/V' CO2 nadir was 40 (31-44). The mean±sd of peak end-tidal carbon dioxide tension (P ETCO2 ) was 23±8 mmHg. Ea, Eed and parameters reflecting pulmonary arterial stiffness (capacitance and distensibility) correlated with the V' E/V' CO2 slope, V' E/V' CO2 nadir, P ETCO2 and peak oxygen pulse. RV Ees and RV-arterial coupling as assessed by the Ees/Ea ratio showed no correlations with CPET parameters. Ea (univariate OR 7.28, 95% CI 1.20-44.04) and Eed (univariate OR 2.21, 95% CI 0.93-5.26) were significantly associated with ventilatory inefficiency (p<0.10).Our data suggest that impaired RV lusitropy and increased afterload are associated with ventilatory inefficiency in PAH.

Cardiac Magnetic Resonance Imaging-Based Right Ventricular Strain Analysis for Assessment of Coupling and Diastolic Function in Pulmonary Hypertension.

OBJECTIVES: This study sought to compare cardiac magnetic resonance (CMR) imaging-derived right ventricular (RV) strain and invasively measured pressure-volume loop-derived RV contractility, stiffness, and afterload and RV-arterial coupling in pulmonary hypertension (PH). BACKGROUND: In chronic RV pressure overload, RV-arterial uncoupling is considered the driving cause of RV maladaptation and eventual RV failure. The pathophysiological and clinical value of CMR-derived RV strain relative to that of invasive pressure-volume loop-derived measurements in PH remains incompletely understood. METHODS: In 38 patients with PH, global RV CMR strain was measured within 24 h of diagnostic right heart catheterization and conductance (pressure-volume) catheterization. Associations were evaluated by correlation, multivariate logistic binary regression, and receiver operating characteristic analyses. RESULTS: Long-axis RV longitudinal and radial strain and short-axis RV radial and circumferential strain were -18.0 ± 7.0%, 28.9% [interquartile range (IQR): 17.4% to 46.6%]; 15.6 ± 6.2%; and -9.8 ± 3.5%, respectively. RV-arterial coupling (end-systolic [Eds]/arterial elastance [Ea]) was 0.76 (IQR: 0.47 to 1.07). Peak RV strain correlated with Ees/Ea, afterload (Ea), RV diastolic dysfunction (Tau), and stiffness (end-diastolic elastance [Eed]) but not with contractility (Ees). In multivariate analysis, long-axis RV radial strain was associated with RV-arterial uncoupling (Ees/Ea: <0.805; odds ratio [OR]: 5.50; 95% confidence interval [CI]: 1.50 to 20.18), whereas long-axis RV longitudinal strain was associated with increased RV diastolic stiffness (Eed: ≥0.124 mm Hg/ml; OR: 1.23; 95% CI: 1.10 to 1.51). The long-axis RV longitudinal strain-to-RV end-diastolic volume/body surface area ratio strongly predicted RV diastolic stiffness (area under receiver operating characteristic curve: 0.908). CONCLUSIONS: In chronic RV overload, CMR-determined RV strain is associated with RV-arterial uncoupling and RV end-diastolic stiffness and represents a promising noninvasive alternative to current invasive methods for assessment of RV-arterial coupling and end-diastolic stiffness in patients with PH. (Right Ventricular Haemodynamic Evaluation and Response to Treatment [Rightheart I]; NCT03403868).

Reserve of Right Ventricular-Arterial Coupling in the Setting of Chronic Overload.

BACKGROUND: Right ventricular (RV) maladaptation and failure determine outcome in pulmonary hypertension. The adaptation of RV function to loading (RV-pulmonary arterial coupling) is defined by a ratio of end-systolic to arterial elastances (Ees/Ea). How RV-pulmonary arterial coupling relates to pulmonary hypertension severity and onset of RV failure (defined by excessive volume increase and ejection fraction [EF] decrease) is not exactly known. METHODS AND RESULTS: We performed cardiac magnetic resonance (CMR) imaging within 24 hours of a diagnostic right heart catheterization and invasive measurement of RV pressure-volume loops in 42 patients with pulmonary hypertension. Median (interquartile range) Ees and Ea were 0.49 (0.35-0.74) and 0.74 (0.45-1.04) mm Hg/mL, respectively; Ees/Ea was 0.73 (0.47-1.07). End-diastolic elastance (Eed) was 0.14 (0.06-0.24) mm Hg/mL. RV EF was 39±13%. End-systolic volume and end-diastolic volume/body surface area (BSA) were 62 (45-101) and 104 (83-143) mL/m2, respectively. Ees/Ea decreased with increasing RV end-diastolic volume/BSA, mass/BSA, and pulmonary arterial stiffness, and with decreasing EF, from 0.89 to 1.09 in the least impaired tertiles to 0.55 to 0.61 in the most impaired tertiles. Eed increased with increasing RV mass/BSA, end-diastolic volume/BSA, and T1 mapping and with decreasing EF. Receiver operating characteristic analysis identified an Ees/Ea cutoff of 0.805 associated with onset of RV failure defined by increased RV volumes with EF <35%. CONCLUSIONS: RV-pulmonary arterial coupling (Ees/Ea) has considerable reserve, from normal values of 1.5-2 to <0.8, and has the ability to detect pending RV failure in patients with pulmonary hypertension. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT03403868.