Prognostic Value of Delayed Enhancement Cardiac Magnetic Resonance Imaging in Mitral Valve Repair

Moving from left ventricular ejection fraction to deformation imaging in mitral valve regurgitation

The increasing prevalence of valvular heart diseases, specifically mitral regurgitation (MR), underscores the need for a careful and timely approach to intervention. Severe MR, whether primary or secondary, when left untreated leads to adverse outcomes, emphasizing the critical role of a timely surgical or transcatheter intervention. While left ventricular ejection fraction (LVEF) remains the guideline-recommended measure for assessing left ventricle damage, emerging evidence raises concerns regarding its reliability in MR due to its volume-dependent nature. This review summarizes the existing literature on the role of LVEF and deformation imaging techniques, emphasizing the latter's potential in providing a more accurate evaluation of intrinsic myocardial function. Moreover, it advocates the need for an integrated approach that combines traditional with emerging measures, aiming to optimize the management of patients with MR. It attempts to highlight the need for future research to validate the clinical application of deformation imaging techniques through large-scale studies.

Myocardial fibrosis in rheumatic heart disease: emerging concepts and clinical implications

Rheumatic heart disease (RHD) remains a significant cardiovascular burden in the world even though it is no longer common in affluent countries. Centuries of history surrounding this disease provide us with a thorough understanding of its pathophysiology. Infections in the throat, skin, or mucosa are the gateway for Group A Streptococcus (GAS) to penetrate our immune system. A significant inflammatory response to the heart is caused by an immunologic cascade triggered by GAS antigen cross-reactivity. This exaggerated immune response is primarily responsible for cardiac dysfunction. Recurrent inflammatory processes damage all layers of the heart, including the endocardium, myocardium, and pericardium. A vicious immunological cycle involving inflammatory mediators, angiotensin II, and TGF-β promotes extracellular matrix remodeling, resulting in myocardial fibrosis. Myocardial fibrosis appears to be a prevalent occurrence in patients with RHD. The presence of myocardial fibrosis, which causes left ventricular dysfunction in RHD, might be utilized to determine options for treatment and might also be used to predict the outcome of interventions in patients with RHD. This emerging concept of myocardial fibrosis needs to be explored comprehensively in order to be optimally utilized in the treatment of RHD.

Echocardiography vs. CMR in the Quantification of Chronic Mitral Regurgitation: A Happy Marriage or Stormy Divorce?

Quantification of chronic mitral regurgitation (MR) is essential to guide patients’ clinical management and define the need and appropriate timing for mitral valve surgery. Echocardiography represents the first-line imaging modality to assess MR and requires an integrative approach based on qualitative, semiquantitative, and quantitative parameters. Of note, quantitative parameters, such as the echocardiographic effective regurgitant orifice area, regurgitant volume (RegV), and regurgitant fraction (RegF), are considered the most reliable indicators of MR severity. In contrast, cardiac magnetic resonance (CMR) has demonstrated high accuracy and good reproducibility in quantifying MR, especially in cases with secondary MR; nonholosystolic, eccentric, and multiple jets; or noncircular regurgitant orifices, where quantification with echocardiography is an issue. No gold standard for MR quantification by noninvasive cardiac imaging has been defined so far. Only a moderate agreement has been shown between echocardiography, either with transthoracic or transesophageal approaches, and CMR in MR quantification, as supported by numerous comparative studies. A higher agreement is evidenced when echocardiographic 3D techniques are used. CMR is superior to echocardiography in the calculation of the RegV, RegF, and ventricular volumes and can provide myocardial tissue characterization. However, echocardiography remains fundamental in the pre-operative anatomical evaluation of the mitral valve and of the subvalvular apparatus. The aim of this review is to explore the accuracy of MR quantification provided by echocardiography and CMR in a head-to-head comparison between the two techniques, with insight into the technical aspects of each imaging modality.

Late plasma exosome microRNA-21-5p depicts magnitude of reverse ventricular remodeling after early surgical repair of primary mitral valve regurgitation

Introduction

Primary mitral valve regurgitation (MR) results from degeneration of mitral valve apparatus. Mechanisms leading to incomplete postoperative left ventricular (LV) reverse remodeling (Rev-Rem) despite timely and successful surgical mitral valve repair (MVR) remain unknown. Plasma exosomes (pEXOs) are smallest nanovesicles exerting early postoperative cardioprotection. We hypothesized that late plasma exosomal microRNAs (miRs) contribute to Rev-Rem during the late postoperative period.

Methods

Primary MR patients (n = 19; age, 45-71 years) underwent cardiac magnetic resonance imaging and blood sampling before (T0) and 6 months after (T1) MVR. The postoperative LV Rev-Rem was assessed in terms of a decrease in LV end-diastolic volume and patients were stratified into high (HiR-REM) and low (LoR-REM) LV Rev-Rem subgroups. Isolated pEXOs were quantified by nanoparticle tracking analysis. Exosomal microRNA (miR)-1, -21-5p, -133a, and -208a levels were measured by RT-qPCR. Anti-hypertrophic effects of pEXOs were tested in HL-1 cardiomyocytes cultured with angiotensin II (AngII, 1 μM for 48 h).

Results

Surgery zeroed out volume regurgitation in all patients. Although preoperative pEXOs were similar in both groups, pEXO levels increased after MVR in HiR-REM patients (+0.75-fold, p = 0.016), who showed lower cardiac mass index (-11%, p = 0.032). Postoperative exosomal miR-21-5p values of HiR-REM patients were higher than other groups (p < 0.05). In vitro, T1-pEXOs isolated from LoR-REM patients boosted the AngII-induced cardiomyocyte hypertrophy, but not postoperative exosomes of HiR-REM. This adaptive effect was counteracted by miR-21-5p inhibition.

Summary/Conclusion

High levels of miR-21-5p-enriched pEXOs during the late postoperative period depict higher LV Rev-Rem after MVR. miR-21-5p-enriched pEXOs may be helpful to predict and to treat incomplete LV Rev-Rem after successful early surgical MVR.

Myocardial extracellular volume assessed by cardiovascular magnetic resonance may predict adverse left ventricular remodeling in rheumatic heart disease after valvular surgery

BACKGROUND

Only a few studies to date have focused on the application of cardiovascular magnetic resonance (CMR) in rheumatic heart disease (RHD); in particular, research on the application of T1-mapping CMR sequences is limited. This study aimed to investigate whether diffuse myocardial fibrosis evaluated using preoperative T1 mapping and extracellular volume (ECV) fraction measurement could predict the progression of adverse left ventricular remodeling (LVR) after surgery.

METHODS

A total of 32 adult patients with RHD and 30 healthy controls were recruited. Baseline clinical characteristics, CMR findings, and T1 mapping measurements were compared between the two groups. Transthoracic echocardiography measurements were collected before and after surgery. Patients with an increase in left ventricular end-diastolic volume of >15% or a decrease in left ventricular ejection fraction of >10% were classified into the adverse remodeling group; otherwise, patients were categorized into the non-adverse remodeling group.

RESULTS

Compared with the healthy controls, patients with RHD had impaired biventricular function, enlarged ventricular volume, and increased native T1 and ECV values. Patients in the adverse remodeling group had higher ECV values than those in the non-adverse remodeling group (33.25%±3.67% vs. 28.45%±4.46%, P=0.002). Binary logistic regression analysis showed that the ECV value was associated with adverse LVR (odds ratio: 1.273, P=0.045). ECV was found to be a sensitive biomarker for predicting adverse LVR (area under the curve: 0.78; sensitivity: 75.0%; specificity: 77.3%).

CONCLUSIONS

ECV has potential value for predicting the progression of adverse LVR and for identifying non-responders among patients with RHD undergoing surgery.

Multimodality imaging in valvular heart disease: how to use state-of-the-art technology in daily practice

Our understanding of the complexities of valvular heart disease (VHD) has evolved in recent years, primarily because of the increased use of multimodality imaging (MMI). Whilst echocardiography remains the primary imaging technique, the contemporary evaluation of patients with VHD requires comprehensive analysis of the mechanism of valvular dysfunction, accurate quantification of severity, and active exclusion extravalvular consequences. Furthermore, advances in surgical and percutaneous therapies have driven the need for meticulous multimodality imaging to aid in patient and procedural selection. Fundamental decision-making regarding whom, when, and how to treat patients with VHD has become more complex. There has been rapid technological advancement in MMI; many techniques are now available in routine clinical practice, and their integration into has the potential to truly individualize management strategies. This review provides an overview of the current evidence for the use of MMI in VHD, and how various techniques within each modality can be used practically to answer clinical conundrums.

Myxomatous Mitral Valve Disease with Mitral Valve Prolapse and Mitral Annular Disjunction: Clinical and Functional Significance of the Coincidence

The morphological changes that occur in myxomatous mitral valve disease (MMVD) involve various components, ultimately leading to the impairment of mitral valve (MV) function. In this context, intrinsic mitral annular abnormalities are increasingly recognized, such as a mitral annular disjunction (MAD), a specific anatomical abnormality whereby there is a distinct separation between the mitral annulus and the left atrial wall and the basal portion of the posterolateral left ventricular myocardium. In recent years, several studies have suggested that MAD contributes to myxomatous degeneration of the mitral leaflets, and there is growing evidence that MAD is associated with ventricular arrhythmias and sudden cardiac death. In this review, the morphological characteristics of MAD and imaging tools for diagnosis will be described, and the clinical and functional aspects of the coincidence of MAD and myxomatous MVP will be discussed.

Impact of Myocardial Scar on Prognostic Implication of Secondary Mitral Regurgitation in Heart Failure

OBJECTIVES

The objective of the present study was to use cardiovascular magnetic resonance (CMR) to examine the natural history of secondary MR severity and the implication of left ventricular (LV) scar on its prognostic significance.

BACKGROUND

There is a need for further understanding of the prognostic implication of secondary mitral regurgitation (MR) given the heterogeneous findings of the 2 recent randomized trials on percutaneous mitral intervention in patients with secondary MR.

METHODS

Patients with heart failure were enrolled into a prospective observational registry between 2008 and 2019. Outcomes were a composite of all-cause death, heart transplantation, or LV assist device implantation at follow-up. CMR was used to quantify the mitral regurgitation volume and mitral regurgitation fraction (MRF) along with scar burden utilizing late gadolinium enhancement. Patients were categorized into 4 subgroups based on presence and tertiles of scar extent: no scar, limited scar (scar burden 1% to 4%), intermediate scar (scar burden 5% to 20%), and extensive scar (scar burden >20%).

RESULTS

Among patients (n = 441) included in the study (age 59 ± 14 years, 43% with ischemic etiology), 85 (19%) experienced an adverse event. MRF ≥30% was associated with increased risk of events among the study group (hazard ratio: 1.74; 95% confidence interval: 1.10 to 2.76; p = 0.02). When stratified by presence or absence of scar, MRF ≥30% was associated with events only among patients with scar (hazard ratio: 1.67; 95% confidence interval: 1.02 to 2.76; p = 0.04) but not among patients without scar. On further classification of patients with scar, the prognostic significance of secondary MR was observed primarily among patients with intermediate scar burden.

CONCLUSIONS

The natural history of secondary MR is complex, and outcomes are affected by severity of MR and vary depending upon the extent of scar. (DeBakey Cardiovascular Magnetic Resonance Study [DEBAKEY-CMR]; NCT04281823).

Left Ventricular Dimension after Mitral Valve Surgery in Rheumatic Mitral Stenosis: The Impact of Myocardial Fibrosis

Background: Patients with rheumatic mitral stenosis (MS) experience changes in left ventricular (LV) dimensions after mitral valve surgery. We sought to investigate changes in LV dimensional parameters after mitral valve surgery and find out whether the same changes occurred in different extents of myocardial fibrosis. Methods: This prospective observational study comprised 43 patients with rheumatic MS planned for mitral valve surgery between October 2017 and April 2018 in National Cardiovascular Center Harapan Kita (NCCHK) Jakarta. All the patients underwent cardiac magnetic resonance imaging based on the late gadolinium enhancement (LGE) protocol for myocardial fibrosis assessment prior to surgery. The patients were classified according to the estimated fibrosis volume considered to influence hemodynamic performance (myocardial fibrosis <5% and myocardial fibrosis ≥5%). Serial transthoracic echocardiographic examinations before and after surgery were performed to detect changes in LV dimensional parameters. Results: This study consisted of 31 (72.1%) women and 12 (27.9%) men at a mean age of 46±9 years. The LGE protocol revealed myocardial fibrosis of less than 5% in 32 (74.4%) patients. A significant increase was detected in the LV end-diastolic diameter postoperatively, specifically in the patients with myocardial fibrosis of less than 5% (44.0±4.8 mm vs 46.6±5.6 mm; P value=0.027). A similar significant increase was not found in the other group (45.0±6.6 mm vs 46.7±6.9 mm; P value=0.256). Other changes in echocardiographic parameters showed similar patterns in both groups. Conclusion: Our patients with rheumatic MS who had myocardial fibrosis of less than 5% demonstrated better improvements in terms of increased preload. Myocardial fibrosis of less than 5% is associated with more favorable improvements in LV geometry.

Cardiac Magnetic Resonance Analysis of Mitral Annular Dynamics after Mitral Valve Repair

OBJECTIVES

The aim of this study was to analyze mitral annulus (MA) dynamics using cardiac magnetic resonance (CMR) in patients with degenerative mitral insufficiency who underwent mitral valve repair (MVR).

METHODS

Mitral valve imaging was performed by CMR in twenty-nine patients with degenerative mitral insufficiency who underwent MVR between July 2014 and August 2016, with quadrangular resection of the posterior leaflet without ring annuloplasty. They were prospectively followed up from the preoperative period up to 2 years postoperatively.

RESULTS

We observed a significant reduction in all measurements of the MA after surgery. The mean systolic circumference of the MA was reduced from 13.28±1.95 cm to 11.50±1.59 cm, and the diastolic circumference was reduced from 12.51±2.01 cm to 10.66±2.09 cm in the immediate postoperative period, measures that remained stable 2 years after MVR (p<0.001). The mean maximum area of the MA was significantly reduced from 14.34±4.03 to 10.45±3.17 cm2 when comparing the immediate postoperative period and the 2 year follow-up (p<0.001). The same occurred with the mean minimum area of the MA, which was reduced from 12.53±3.68 cm2 to 9.23±2.84 cm2 in the same period, and this reduction was greater in the antero-posterior diameter than in the mid-lateral diameter. The mobility of the MA was preserved after surgery, ranging between 19.6% and 25.7% at 2-year follow-up.

CONCLUSION

We observed a significant reduction in the MA size after MVR, with preservation of the MA mobility at the 2-year follow-up.

Relationship of extracellular volume assessed on cardiac magnetic resonance and serum cardiac troponins and natriuretic peptides with heart failure outcomes

Measures of serum cardiac troponins and natriuretic peptides have become established as prognostic heart failure risk markers. In addition to detecting myocardial fibrosis through late gadolinium enhancement (LGE), extracellular volume fraction (ECV) measures by cardiac magnetic resonance (CMR) have emerged as a phenotypic imaging risk marker for incident heart failure outcomes. We sought to examine the relationship between cardiac troponins, natriuretic peptides, ECV and their associations with incident heart failure events in a CMR referral base. Mid short axis T1 maps were divided into 6 cardiac segments, each classified as LGE absent or present. Global ECV was derived from T1 maps using the area-weighted average of only LGE-absent segments. ECV was considered elevated if measured >30%, the upper 95% bounds of a reference healthy group without known cardiac disease (n = 28). Patients were dichotomized by presence of elevated ECV. High-sensitivity cardiac troponin T (hs-cTnT) and N-terminal B-type natriuretic peptide (NT-proBNP) were measured using serum samples acquired and stored at time of CMR scan, and patients were categorized into 3 groups for each blood marker based on recommended cutoff values. Subsequent heart failure admission and any death were ascertained. Relationships with ECV, hs-cTnT, and NT-proBNP were examined separately and as a composite with Cox proportional hazard models. Of 1,604 serial patients referred for a clinical CMR with myocardial T1 maps, 331 were eligible after exclusions and had blood available and were followed over a median 25.0 [interquartile range 21.8, 31.7] months. After adjustments for age (mean 57.3 [standard deviation (SD) 15.1 years), gender (61% male), and ethnicity (12.7% black), elevated ECV remained a predictor of a first composite heart failure outcome for patients with high levels of hs-cTnT (≥14 ng/L; hazard ratio [HR] 2.42 [95% confidence interval (CI) 1.17, 5.03]; p = 0.02) and NT-proBNP (≥300 pg/mL; HR 2.28 [95% CI 1.24, 4.29]; p = 0.01). Similar trends were seen for lower category levels of blood markers, but did not persist with minimal covariate adjustments. Elevated measures of ECV by CMR are associated with incident heart failure outcomes in patients with high hs-cTnT and NT-proBNP levels. This imaging marker may have a role for additional heart failure risk stratification.

Myocardial Extracellular Volume Fraction Adds Prognostic Information Beyond Myocardial Replacement Fibrosis

BACKGROUND

Cardiac magnetic resonance techniques permit quantification of the myocardial extracellular volume fraction (ECV), representing a surrogate marker of reactive interstitial fibrosis, and late gadolinium enhancement (LGE), representing replacement fibrosis or scar. ECV and LGE have been independently linked with heart failure (HF) events. In deriving ECV, coronary artery disease type LGE, but not non-coronary artery disease type LGE, has been consistently excluded. We examined the associations between LGE, global ECV derived from myocardial tissue segments free of any detectable scar, and subsequent HF events.

METHODS

Mid short-axis T1 maps were divided into 6 cardiac segments, each classified as LGE absent or present. Global ECV was derived from only segments without LGE. ECV was considered elevated if >30%, the upper 95% bounds of a reference group without known cardiac disease (n=28). Patients were divided into 4 groups by presence of elevated ECV and of any LGE. Subsequent HF hospitalization and any death were ascertained. Their relationship with ECV was examined separately and as a composite with Cox proportional hazard models.

RESULTS

Of 1604 serial patients with T1 maps, 1255 were eligible after exclusions and followed over a median 26.3 (interquartile range, 15.9-37.5) months. Patients with elevated ECV had increased risk for death (hazard ratio [HR] 2.45 [95% CI, 1.76-3.41]), HF hospitalization (HR, 2.45 [95% CI, 1.77-3.40]), and a combined end point of both outcomes (HR, 2.46 [95% CI, 1.94-3.14]). After adjustments for covariates including LGE, the relationship persisted for death (HR, 1.82 [95% CI, 1.28-2.59]), hospitalization (HR, 1.60 [95% CI, 1.12-2.27]), and combined end points (HR, 1.73 [95% CI, 1.34-2.24]).

CONCLUSIONS

ECV measures of diffuse myocardial fibrosis were associated with HF outcomes, despite exclusion of replacement fibrosis segments from their derivation and even among patients without any scar. ECV may have a synergistic role with LGE in HF risk assessment.

Prognostic Value of Late Gadolinium Enhancement in Postoperative Morbidity following Mitral Valve Surgery in Rheumatic Mitral Stenosis

Myocardial fibrosis in rheumatic mitral stenosis (MS) is caused by chronic inflammatory process. Its occurrence may lead to hemodynamic problems, especially after cardiac surgery. Myocardial fibrosis predicts worse morbidity after cardiac surgery, notably in coronary heart disease and aortic valve abnormalities. However, this issue has not been explored yet among patients with rheumatic MS. The aim of the study was to investigate prognostic impact of myocardial fibrosis to postoperative morbidity after mitral valve surgery in patients with rheumatic MS. This is a prospectively enrolled observational study of 47 consecutive rheumatic MS patients. All patients had preoperative evaluation with cardiac magnetic resonance imaging (CMR) including late gadolinium enhancement (LGE) protocol for left ventricular myocardial fibrosis assessment prior to mitral valve surgery. All patients were followed during hospitalization period. Postoperative morbidities were defined as stroke, renal failure, and prolonged mechanical ventilation. This study involved 33 women (70.2%) and 14 men (29.8%) with a mean age of 46 ± 10 years. Preoperative myocardial fibrosis was identified in 43 patients (91.5%). Estimated fibrosis volume ranged from 0% to 12.8% (median 2.8%). Postoperative morbidities occurred in 11 patients (23.4%). Significant mean difference of myocardial fibrosis volume was observed between patients with and without morbidity after mitral valve surgery (5.97 ± 4.16% and 3.12 ± 2.62%, p  = 0.04). This significant association was allegedly influenced by different postoperative hemodynamic changes between the two groups. More extensive myocardial fibrosis is associated with postoperative morbiditiy after mitral valve surgery in patients with rheumatic MS.

Association between late gadolinium enhancement and global longitudinal strain in patients with rheumatic mitral stenosis

The correlation between the extent of myocardial fibrosis and subclinical left ventricle (LV) systolic dysfunction in rheumatic mitral stenosis (MS) has not been widely studied. We sought to evaluate the correlation between the extent of LV myocardial fibrosis quantified by late gadolinium enhancement (LGE) using cardiac magnetic resonance (CMR) and global longitudinal strain (GLS) by speckle tracking echocardiography (STE) in patients with rheumatic MS. We prospectively evaluated 36 consecutive rheumatic MS patients who were planning to undergo mitral valve surgery. Then we evaluate the correlation between the extent of LV myocardial fibrosis quantified by LGE CMR and the systolic LV function by GLS using STE. Thirty-six patients with mean age of 45.7 ± 9.9 years old, showed mean LGE was 4.9 ± 2.7%. The mean LV ejection fraction (EF) measured by CMR was 50 ± 10.8%, and the mean LV GLS was 13.5 ± 3.9%. There was a moderate correlation between GLS and LGE (r - 0.432, p = 0.009). There were no correlations between GLS with mitral valve area (MVA) with r 0.149, p = 0.385, mean mitral valve gradient (MVG) with r -0.078, p = 0.653, and LVEF (r 0.299, p = 0.076). There was a moderate correlation between LGE and GLS in patients with rheumatic MS.

Computed tomography angiography for imaging results of neochordal mitral valve repair

Introduction

Degenerative mitral regurgitation is currently the most frequent indication for mitral valve repair.

Aim

To visualize and assess the mid-term results of mitral valve repair with neochordae implantation, using computed tomography angiography (CTA) imaging.

Material and methods

The CTA with ECG gating and without modulation was applied in 10 patients to assess the results of a mitral valve sparing procedure. The results of 3 patients are presented. The patients were operated on for severe symptomatic degenerative mitral regurgitation, defined according to a modified Carpentier’s functional classification.

Results

Neochordal repair, by placing expanded polytetrafluoroethylene sutures between the leading edge of the prolapsing segment and the corresponding papillary muscle, was conducted. From 1 to 3 double Gore-Tex loops were used. Leaflet clefts, if present, were sutured. All repairs included mitral valve ring annuloplasty. The CTA was performed at 20–24 months after the surgery. Long-axis views, reconstructed during mid-systole, seemed to be the most valuable. Good quality cardiac images, precisely presenting the mitral valve complex with its constituents, were obtained in the case of patients without obesity, with a relatively small anterior-posterior thorax dimension, with sinus, slow heart rhythm and quite good left ventricle contractility. The evaluation of the mitral valve included presence of calcifications, fibrosis or thickening, chordal insertion and coaptation points, and papillary muscle locations. Primary and secondary native chordae tendineae and artificial chordae were visualized.

Conclusions

Contrast material-enhanced ECG-gated CTA applied after mitral valve repair with Gore-Tex neochordae allows one to obtain satisfactory mitral valve images, especially during mid-systole, and evaluate mid-term results of the surgery in chosen patients.

Cardiovascular magnetic resonance imaging to assess myocardial fibrosis in valvular heart disease

The left ventricular (LV) remodeling process associated with significant valvular heart disease (VHD) is characterized by an increase of myocardial interstitial space with deposition of collagen and loss of myofibers. These changes occur before LV systolic function deteriorates or the patient develops symptoms. Cardiovascular magnetic resonance (CMR) permits assessment of reactive fibrosis, with the use of T1 mapping techniques, and replacement fibrosis, with the use of late gadolinium contrast enhancement. In addition, functional consequences of these structural changes can be evaluated with myocardial tagging and feature tracking CMR, which assess the active deformation (strain) of the LV myocardium. Several studies have demonstrated that CMR techniques may be more sensitive than the conventional measures (LV ejection fraction or LV dimensions) to detect these structural and functional changes in patients with severe left-sided VHD and have shown that myocardial fibrosis may not be reversible after valve surgery. More important, the presence of myocardial fibrosis has been associated with lesser improvement in clinical symptoms and recovery of LV systolic function. Whether assessment of myocardial fibrosis may better select the patients with severe left-sided VHD who may benefit from surgery in terms of LV function and clinical symptoms improvement needs to be demonstrated in prospective studies. The present review article summarizes the current status of CMR techniques to assess myocardial fibrosis and appraises the current evidence on the use of these techniques for risk stratification of patients with severe aortic stenosis or regurgitation and mitral regurgitation.