Background: Four-dimensional flow cardiac magnetic resonance (4D flow CMR) is an emerging non-invasive imaging technology that can be used to quantify mitral regurgitation (MR) volume. Current methods of quantification have demonstrated limitations in accurate analysis, particularly in difficult cases such as complex congenital heart disease. 4D flow CMR methods aim to circumvent these limitations and allow accurate quantification of MR volume even in complex cases. This systematic review aims to summarize the available literature on 4D flow CMR MR quantification methods and examine their ability to accurately classify MR severity. Methods: Structured searches were carried out on Medline and EMBASE in December 2018 to identify suitable research outcome studies. The titles and abstracts were screened for relevance, with a third adjudicator utilized when study suitability was uncertain. Results: Seven studies met the eligibility criteria and were included in the systematic review. The most widely used 4D flow MRI method was retrospective valve tracking (RVT) which was examined in five papers. The key finding of these papers was that RVT is a reliable and accurate method of regurgitant volume quantification. Conclusions: MR quantification through 4D flow MRI is both feasible and accurate. The evidence gathered suggests that for MR assessment, 4D flow MRI is potentially as accurate and reliable to echocardiography and may be complementary to this technique. Further work on MR quantification 4D flow image analysis is needed to determine the most accurate analysis technique and to demonstrate 4D flow MRI as a predictor of clinical outcome. PROSPERO Registration Number: CRD42019122837, http://www.crd.york.ac.uk/PROSPERO/display_record.php?ID=CRD42019122837

Background: There are several methods to quantify mitral regurgitation (MR) by cardiovascular magnetic resonance (CMR). The interoperability of these methods and their reproducibility remains undetermined. Objective: To determine the agreement and reproducibility of different MR quantification methods by CMR across all aetiologies. Methods: Thirty-five patients with MR were recruited (primary MR = 12, secondary MR = 10 and MVR = 13). Patients underwent CMR, including cines and four-dimensional flow (4D flow). Four methods were evaluated: MR Standard (left ventricular stroke volume -aortic forward flow by phase contrast), MR LVRV (left ventricular stroke volume -right ventricular stroke volume), MR Jet (direct jet quantification by 4D flow) and MR MVAV (mitral forward flow by 4D flow -aortic forward flow by 4D flow). For all cases and MR types, 520 MR volumes were recorded by these 4 methods for intra−/inter-observer tests. Results: In primary MR, MR MVAV and MR LVRV were comparable to MR Standard (P > 0.05). MR Jet resulted in significantly higher MR volumes when compared to MR Standard (P < 0.05) In secondary MR and MVR cases, all methods were comparable. In intra-observer tests, MR MVAV demonstrated least bias with best limits of agreement (bias = −0.1 ml, −8 ml to 7.8 ml, P = 0.9) and best concordance correlation coefficient (CCC = 0.96, P < 0.01). In interobserver tests, for primary MR and MVR, least bias and highest CCC were observed for MR MVAV . For secondary MR, bias was lowest for MR Jet (−0.1 ml, P_NS). Conclusion: CMR methods of MR quantification demonstrate agreement in secondary MR and MVR. In primary MR, this was not observed. Across all types of MR, MR MVAV quantification demonstrated the highest reproducibility and consistency.

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The management of patients with aortic stenosis (AS) crucially depends on accurate diagnosis. The main aim of this study were to validate the four-dimensional flow (4D flow) cardiovascular magnetic resonance (CMR) methods for AS assessment. Eighteen patients with clinically severe AS were recruited. All patients had pre-valve intervention 6MWT, echocardiography and CMR with 4D flow. Of these, ten patients had a surgical valve replacement, and eight patients had successful transcatheter aortic valve implantation (TAVI). TAVI patients had invasive pressure gradient assessments. A repeat assessment was performed at 3–4 months to assess the remodelling response. The peak pressure gradient by 4D flow was comparable to an invasive pressure gradient (54 ± 26 mmHG vs 50 ± 34 mmHg, P = 0.67). However, Doppler yielded significantly higher pressure gradient compared to invasive assessment (61 ± 32 mmHG vs 50 ± 34 mmHg, P = 0.0002). 6MWT was associated with 4D flow CMR derived pressure gradient (r = −0.45, P = 0.01) and EOA (r = 0.54, P < 0.01) but only with Doppler EOA (r = 0.45, P = 0.01). Left ventricular mass regression was better associated with 4D flow derived pressure gradient change (r = 0.64, P = 0.04). 4D flow CMR offers an alternative method for non-invasive assessment of AS. In addition, 4D flow derived valve metrics have a superior association to prognostically relevant 6MWT and LV mass regression than echocardiography.

Background. Four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) is a noninvasive novel imaging technology that can be used to visualise and assess right ventricular function. The aim of this systematic review is to summarise the literature available on 4D flow CMR methods used to determine right ventricular diastolic function. Methods. A systematic review of current literature was carried out to ascertain what is known about right ventricular assessment by quantification of 4D flow CMR. Structured searches were carried out on Medline and EMBASE in December 2018. PG and NB screened the titles and abstracts for relevance. Results. Of the 20 articles screened, 5 studies met eligibility for systematic review. After a further search on pubmed 1 more relevant article was found and added to the review. Conclusions. These proposed methods using 4D flow CMR can quantify right ventricular diastolic assessment. The evidence gathered is mainly observational, featuring single-centred studies. Larger, multicentre studies are required to validate the proposed techniques, evaluate reproducibility, and investigate the clinical applicability that 4D flow CMR offers compared to standard practices. PROSPERO registration number is CRD42019121492.

Assessment of right ventricular (RV) diastolic function is not routinely carried out. This is due to standard two-dimensional imaging techniques being unreliable. Four-dimensional flow (4D flow) derived right ventricular blood flow kinetic energy assessment could circumvent the issues of the current imaging modalities. It also remains unknown whether there is an association between right ventricular blood flow kinetic energy (KE) and healthy ageing. We hypothesise that healthy ageing requires maintaining normal RV intra-cavity blood flow as quantified using KE method. The main objective of this study was to investigate the effect of healthy ageing on tricuspid through-plane flow and right ventricular blood flow kinetic energy. In this study, fifty-three healthy participants received a 4D flow cardiovascular magnetic resonance (CMR) scan on 1.5 T Philips Ingenia. Cine segmentation and 4D flow analysis were performed using dedicated software. Standard statistical methods were carried out to investigate the associations. Both RV E-wave KEi EDV (r = −0.3, P = 0.04) and A-wave KEi EDV (r = 0.42, P < 0.01) showed an association with healthy ageing. Additionally, the right ventricular blood flow KEi EDV E/A ratio demonstrated the strongest association with healthy ageing (r = −0.53, P < 0.01) when compared to all RV functional and haemodynamic parameters. Furthermore, in a multivariate regression model, KEi EDV E/A ratio and 4D flow derived tricuspid valve stroke volume demonstrated independent association to healthy ageing (beta −0.02 and 0.68 respectively, P < 0.01). Ageing is independently associated with 4D flow derived tricuspid stroke volume and RV blood flow KE E/A ratio. These novel 4D flow CMR derived imaging markers have future potential for RV diastolic assessment. Age is an independent risk factor for the development of heart failure(HF), and acute heart failure is the commonest presentation in the elderly 1,2. With ageing, the heart undergoes structural and functional changes. With ageing, the heart adapts to vascular stiffening associated with increased thickness of the left ventricular wall and fibrosis. These changes, in turn, leads to diastolic failure secondary to increased afterload. Additionally, pulmonary vasculature is likely to get affected by age-associated arterial remodelling, resulting in the stiffness of pulmonary vasculature thus leading to elevated PAPs. The ability of the heart to adapt to physiological changes and compensatory mechanisms also diminishes with ageing including changes in contractility, maximal heart rate, end-systolic and diastolic volumes and increased pulse pressure with elevated left heart filling pressures due to blood vessel stiffening. These changes lower the threshold for the development of hypertension, diastolic dysfunction and heart failure 3,4. The left ventricular (LV) functional and structural changes associated with ageing are well established and are in routine use for the assessment of systolic and diastolic LV function 5. The LV ageing process can potential...

Background: Left ventricular (LV) kinetic energy (KE) assessment by four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) may offer incremental value over routine assessment in aortic stenosis (AS). The main objective of this study is to investigate the LV KE in patients with AS before and after the valve intervention. In addition, this study aimed to investigate if LV KE offers incremental value for its association to the six-minute walk test (6MWT) or LV remodelling post-intervention. Methods:We recruited 18 patients with severe AS. All patients underwent transthoracic echocardiography for mean pressure gradient (mPG), CMR including 4D flow and 6MWT. Patients were invited for post-valve intervention follow-up CMR at 3 months and twelve patients returned for follow-up CMR. KE assessment of LV blood flow and the components (direct, delayed, retained and residual) were carried out for all cases.LV KE parameters were normalised to LV end-diastolic volume (LVEDV).Results: For LV blood flow KE assessment, the metrics including time delay (TD) for peak E-wave from base to mid-ventricle (14±48 vs. 2.5±9.75 ms, P=0.04), direct (4.91±5.07 vs. 1.86±1.72 μJ, P=0.01) and delayed (2.46±3.13 vs. 1.38±1.15 μJ, P=0.03) components of LV blood flow demonstrated a significant change between pre-and post-valve intervention. Only LV KEi EDV (r=−0.53, P<0.01), diastolic KEi EDV (r=−0.53, P<0.01) and E wave KEi EDV (r=−0.38, P=0.04) demonstrated association to the 6MWT. However, Pre-operative LV KEi EDV (r=0.67, P=0.02) demonstrated association to LV remodelling post valve intervention. Conclusions: LV blood flow KE is associated with 6MWT and LV remodelling in patients with AS. LV KE assessment provides incremental value over routine LV function and pressure gradient (PG) assessment in AS.

acquisition. The velocity encoded images were analysed for the following: mean pulmonary artery pan-systolic velocity (PASV), MPA stroke volume, MPA wall shear stress (WSS) and wall shear rate (WSR). The 4-chamber cine was used to measure end-diastolic right atrial area. Right ventricular volumes were analysed using standard methods. Stepwise multiple regression model of significantly associated parameters (p<0.05) was developed. Results Mean age of the 18 patients was 68.78±7.46 years (44% males). The following CMR metrics demonstrated significant association to the measured mPAP: RA area (r=0.65 p=0.03); MPA mean pan-systolic velocity (r=À0.57 p=0.01); RVEDV (r=0.52 p=0.03); RVEF (r=À0.40 p=0.10); RVESV (r=0.58 p=0.01). In stepwise multiple regression, only two parameters demonstrated independent association to mPAP -RA Area and MPA mean pan-systolic velocity. The predicted mPAP demonstrated good correlation to the measured mPAP (R=0.76, p<0.001). Conclusion(s) Mean pulmonary artery systolic velocity and right atrial area are independently associated with mPAP.Our novel CMR prediction model for mPAP, comprising of these two metrics, demonstrates high association to the measured mPAP by invasive haemodynamic study.