Left ventricular remodelling in chronic primary mitral regurgitation: implications for medical therapy

Even mild mitral regurgitation is associated with incident atrial fibrillation in the general population

AIMS

Mitral regurgitation (MR) can be difficult to quantify. We sought to investigate whether the MR jet area to left atrial (LA) area ratio (MR/LA ratio) method for quantifying MRs can be used to predict incident atrial fibrillation (AF) in the general population.

METHODS AND RESULTS

The study included 4466 participants from the 5th Copenhagen City Heart Study, a prospective general population study, who underwent transthoracic echocardiography. MR jet area was measured and indexed to LA area. The endpoint was incident AF. MR was quantified in 4042 participants (mean age: 57 years, 43% men). Of these, 198 (4.9%) developed AF during a median follow-up period of 5.3 years (interquartile range: 4.4-6.1 years). MR was present in 1938 participants (48%) including 1593 (39%) trace/mild MRs (MR/LA ratio ≤ 20% and ≤4 cm2). In unadjusted analysis, MR/LA ratio was associated with incident AF [HR: 1.06 (1.00-1.13), P = 0.042 per 5% increase] but not after adjusting for CHARGE-AF score. However, the association was modified by age (P for interaction = 0.034), such that MR/LA ratio was associated with AF only in participants ≤ 73 years. In these participants, MR/LA ratio 'was' independently associated with AF after adjusting for CHARGE-AF score [HR: 1.14 (1.06-1.24), P = 0.001, per 5% increase]. This finding persisted when restricting the analysis to participants without moderate or severe MR and normal LA size [HR: 1.35 (1.09-1.68), P = 0.005, per 5% increase].

CONCLUSION

MR, including even trace regurgitations quantified by MR/LA ratio, is independently associated with incident AF in individuals ≤ 73 years of age.

Mitral regurgitation in the critically ill: the devil is in the detail

Mitral regurgitation (MR) is common in the critically unwell and encompasses a heterogenous group of conditions with diverging therapeutic strategies. MR may present acutely with haemodynamic instability or more insidiously with failure to wean from mechanical ventilation. Critical illness is associated with marked physiological stress and haemodynamic changes that dynamically influence the severity and implication of MR. The expanding role of critical care echocardiography uniquely positions the intensivist to apply advanced bedside valvular assessment to recognise haemodynanically significant MR, manipulate and optimise cardiopulmonary physiology and identify patients requiring urgent cardiology and surgical referral. This review will consider common clinical scenarios, therapeutic strategies and the pearls and pitfalls of echocardiographic assessment and quantification in the critically unwell.

An Image-Based Computational Fluid Dynamics Study of Mitral Regurgitation in Presence of Prolapse

PURPOSE

In this work we performed an imaged-based computational study of the systolic fluid dynamics in presence of mitral valve regurgitation (MVR). In particular, we compared healthy and different regurgitant scenarios with the aim of quantifying different hemodynamic quantities.

METHODS

We performed computational fluid dynamic (CFD) simulations in the left ventricle, left atrium and aortic root, with a resistive immersed method, a turbulence model, and with imposed systolic wall motion reconstructed from Cine-MRI images, which allowed us to segment also the mitral valve. For the regurgitant scenarios we considered an increase of the heart rate and a dilation of the left ventricle.

RESULTS

Our results highlighted that MVR gave rise to regurgitant jets through the mitral orifice impinging against the atrial walls and scratching against the mitral valve leading to high values of wall shear stresses (WSSs) with respect to the healthy case.

CONCLUSION

CFD with prescribed wall motion and immersed mitral valve revealed to be an effective tool to quantitatively describe hemodynamics in case of MVR and to compare different regurgitant scenarios. Our findings highlighted in particular the presence of transition to turbulence in the atrium and allowed us to quantify some important cardiac indices such as cardiac output and WSS.

Predicting Stroke and Mortality in Mitral Regurgitation: A Machine Learning Approach

We hypothesized that an interpretable gradient boosting machine (GBM) model considering comorbidities, P-wave and echocardiographic measurements, can better predict mortality and cerebrovascular events in mitral regurgitation (MR). Patients from a tertiary center were analyzed. The GBM model was used as an interpretable statistical approach to identify the leading indicators of high-risk patients with either outcome of CVAs and all-cause mortality. A total of 706 patients were included. GBM analysis showed that age, systolic blood pressure, diastolic blood pressure, plasma albumin levels, mean P-wave duration (PWD), MR regurgitant volume, left ventricular ejection fraction (LVEF), left atrial dimension at end-systole (LADs), velocity-time integral (VTI) and effective regurgitant orifice were significant predictors of TIA/stroke. Age, sodium, urea and albumin levels, platelet count, mean PWD, LVEF, LADs, left ventricular dimension at end systole (LVDs) and VTI were significant predictors of all-cause mortality. The GBM demonstrates the best predictive performance in terms of precision, sensitivity c-statistic and F1-score compared to logistic regression, decision tree, random forest, support vector machine, and artificial neural networks. Gradient boosting model incorporating clinical data from different investigative modalities significantly improves risk prediction performance and identify key indicators for outcome prediction in MR.

Impact of Rheumatic Process in Left and Right Ventricular Function in Patients with Mitral Regurgitation

Background

Mitral regurgitation (MR) burdens the left and right ventricles with a volume or pressure overload that leads to a series of compensatory adaptations that eventually lead to ventricular dysfunction, and it is well known that in rheumatic heart disease (RHD) that the inflammatory process not only occurs in the valve but also involves the myocardial and pericardial layers. However, whether the inflammatory process in rheumatic MR is associated with ventricular function besides hemodynamic changes is not yet established.

Purpose

Evaluate whether rheumatic etiology is associated with ventricular dysfunction in patients with chronic MR.

Methods

The study population comprised patients aged 18 years or older included in the registry who had echocardiography performed at the National Cardiovascular Center Harapan Kita in Indonesia during the study period with isolated primary MR due to rheumatic etiology and degenerative process with at least moderate regurgitation.

Results

The current study included 1,130 patients with significant isolated degenerative MR and 276 patients with rheumatic MR. Patients with rheumatic MR were younger and had a higher prevalence of atrial fibrillation and pulmonary hypertension, worse left ventricle (LV) ejection fraction and tricuspid annular plane systolic excursion (TAPSE) value, and larger left atrium (LA) dimension compared to patients with degenerative mitral regurgitation (MR). Gender, age, LV end-systolic diameter, rheumatic etiology, and TAPSE were independently associated with more impaired LV ejection fraction. Whereas low LV ejection fraction, LV end-systolic diameter, and tricuspid peak velocity (TR) peak velocity >3.4 m/s were independently associated with more reduced right ventricle (RV) systolic function (Table 3).

Conclusions

Rheumatic etiology was independently associated with more impaired left ventricular function; however, rheumatic etiology was not associated with reduced right ventricular systolic function in a patient with significant chronic MR.

Ultrastructural Adaptation of the Cardiomyocyte to Chronic Mitral Regurgitation

Introduction: Mitral regurgitation (MR) imposes volume overload on the left ventricle (LV) and elevates wall stress, triggering its adverse remodeling. Pronounced LV dilation, minimal wall thinning, and a gradual decline in cardiac ejection fraction (EF) are observed. The structural changes in the myocardium that define these gross, organ level remodeling are not known. Cardiomyocyte elongation and slippage have both been hypothesized, but neither are confirmed, nor are the changes to the cardiomyocyte structure known. Using a rodent model of MR, we used immunohistochemistry and transmission electron microscopy (TEM) to describe the ultrastructural remodeling of the cardiomyocyte.

Methods: Twenty-four male Sprague-Dawley rats (350–400 g) were assigned to two groups: group (1) rats induced with severe MR (n = 18) and group (2) control rats that were healthy and age and weight matched (n = 6). MR was induced in the beating heart using a 23-G ultrasound-guided, transapical needle to perforate the anterior mitral leaflet, and the rats were followed to 2, 10, and 20 weeks (n = 6/time-point). Echocardiography was performed to quantify MR severity and to measure LV volume and function at each time-point. Explanted myocardial tissue were examined with TEM and immunohistochemistry to investigate the ultrastructural changes.

Results: MR induced rapid and significant increase in end-diastolic volume (EDV), with a 50% increase by 2 weeks, compared with control. Rise in end-systolic volume (ESV) was more gradual; however, by 20 weeks, both EDV and ESV in MR rats were increased by 126% compared with control. A significant decline in EF was measured at 10 weeks of MR. At the ultrastructural level, as early as 2 weeks after MR, cardiomyocyte elongation and increase in cross-sectional area were observed. TEM depicted sarcomere shortening, with loss of Z-line and I-band. Desmin, a cytoskeletal protein that is uniformly distributed along the length of the cardiomyocyte, was disorganized and localized to the intercalated disc, in the rats induced with MR and not in the controls. In the rats with MR, the linear registry of the mitochondrial arrangement along the sarcomeres was lost, with mitochondrial fragmentation, aggregation around the nucleus, and irregularities in the cristae.

Discussion: In the setting of chronic mitral regurgitation, LV dilatation occured by cardiomyocyte elongation, which manifests at the subcellular level as distinct ultrastructural alterations of the sarcomere, cytoskeleton, and mitochondria. Since the cytoskeleton not only provides tensegrity but has functional consequences on myocyte function, further investigation into the impact of cytoskeletal remodeling on progressive heart failure or recovery of function upon correcting the valve lesion are needed.

Functional mitral regurgitation combined with increased early diastolic transmitral velocity to early mitral annulus diastolic velocity ratio is associated with a poor prognosis in patients with shock

BACKGROUND

Functional mitral regurgitation (FMR) is common in critically ill patients and may cause left atrial (LA) pressure elevation. This study aims to explore the prognostic impact of synergistic LA pressure elevation and FMR in patients with shock.

METHODS

We retrospectively screened 130 consecutive patients of 175 patients with shock from April 2016 to June 2017. The incidence and impact of FMR and early diastolic transmitral velocity to early mitral annulus diastolic velocity ratio (E/e') ≥ 4 within 6 h of shock on the prognosis of patients were evaluated. Finally, the synergistic effect of FMR and E/e' were assessed by combination, grouping, and trend analyses.

RESULTS

Forty-four patients (33.8%) had FMR, and 15 patients (11.5%) had E/e' elevation. A multivariate analysis revealed FMR and E/e' as independent correlated factors for 28-day mortality (P = 0.043 and 0.028, respectively). The Kaplan-Meier survival analysis revealed a significant difference in survival between patients with and without FMR (χ2 = 7.672, P = 0.006) and between the E/e' ≥ 14 and E/e' < 14 groups (χ2 = 19.351, P < 0.010). Twenty-eight-day mortality was significantly different among the four groups (χ2 = 30.141, P < 0.010). The risk of 28-day mortality was significantly higher in group 4 (E/e' ≥ 14 with FMR) compared with groups 1 (E/e' < 14 without FMR) and 2 (E/e' < 14 with FMR) (P = 0.001 and 0.046, respectively).

CONCLUSIONS

Patients with shock can be identified by the presence of FMR. FMR and E/e' are independent risk factors for a poor prognosis in these patients, and prognosis is worst when FMR and E/e' ≥ 14 are present. It may be possible to improve prognosis by reducing LA pressure and E/e'.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03082326.

Intrinsic cardiac elastography in patients with primary mitral regurgitation: predictive role after mitral valve repair

AIMS

Chronic volume-overload can impair systolic and diastolic myocardial properties. We tested the hypothesis that Intrinsic Cardiac Elastography may detect alterations in passive myocardial elasticity in patients with chronic severe mitral regurgitation (MR) and predict worsening left ventricular (LV) function after mitral valve repair (MVr).

METHODS AND RESULTS

Comprehensive transthoracic echocardiography and cardiac elastography were performed in 80 patients with primary MR (prolapse and/or flail leaflets) of varying severity and compared with 40 normal subjects. In patients who underwent MVr (n = 51), elastography measurements were related to changes in left ventricular ejection fraction (LVEF) at short-term (3-4 days post-op) and mid-term (1 year) follow-up. Most patients were asymptomatic or mildly symptomatic and had preserved LVEF (>60%). Intrinsic velocity propagation (iVP) of myocardial stretch, a direct measure of myocardial stiffness, was higher in patients with severe MR {median 2.0 [interquartile range (IQR) 1.5-2.2] m/s, range 1.1-3.4 m/s; n = 56} compared to normal subjects [median 1.7 (IQR 1.5-1.8) m/s; n = 40; P = 0.0005], but not in those with mild or moderate MR [median 1.7 (IQR 1.4-1.9) m/s; n = 24]. A higher iVP was associated with more severe LV volume-overload and LV and left atrial enlargement (P < 0.05 for all). In patients undergoing MVr, a higher iVP independently predicted a larger drop in LVEF post-intervention (short-term, P = 0.001; 1 year, P = 0.007), incrementally to pre-operative LVEF (P < 0.05).

CONCLUSION

Non-invasive measurements of myocardial stiffness were able to predict functional deterioration after MVr for chronic primary MR. Further studies should investigate the mechanisms and practical utility of this novel measurement.

Percutaneous Mitral Valve Repair with the MitraClip System in the Current Clinical Practice

Severe mitral valve regurgitation (MR) carries a significant burden both in prognosis and quality of life of patients, as well as on healthcare systems, with high rates of hospitalization for heart failure. While mitral valve surgery constitutes the first-line treatment option for primary MR in suitable patients, surgical treatment for secondary severe MR remains controversial, with a substantial lack of evidence on a survival benefit. In recent decades, percutaneous mitral valve repair has emerged as an alternative treatment for patients deemed not suitable for surgery. Among several devices under development or evaluation, the MitraClip system is the most widespread and is supported by the strongest evidence. While the role of MitraClip in patients with chronic primary MR who are not deemed suitable for surgery is well established, with consistent data showing improvement in both prognosis and quality of life, MitraClip treatment in secondary MR is a rapidly evolving field. Two recent randomized clinical trials generated apparently controversial results but actually provided an interesting pathophysiologic frame that could help discerning patients who will benefit from the procedure versus patients who will not. In this review, we will discuss current treatment options for mitral regurgitation, focusing on percutaneous mitral valve repair with the MitraClip system.

An Image Guided Transapical Mitral Valve Leaflet Puncture Model of Controlled Volume Overload from Mitral Regurgitation in the Rat

Mitral regurgitation (MR) is a widely prevalent heart valve lesion, which causes cardiac remodeling and leads to congestive heart failure. Though the risks of uncorrected MR and its poor prognosis are known, the longitudinal changes in cardiac function, structure and remodeling are incompletely understood. This knowledge gap has limited our understanding of the optimal timing for MR correction, and the benefit that early versus late MR correction may have on the left ventricle. To investigate the molecular mechanisms that underlie left ventricular remodeling in the setting of MR, animal models are necessary. Traditionally, the aorto-caval fistula model has been used to induce volume overload, which differs from clinically relevant lesions such as MR. MR represents a low-pressure volume overload hemodynamic stressor, which requires animal models that mimic this condition. Herein, we describe a rodent model of severe MR in which the anterior leaflet of the rat mitral valve is perforated with a 23G needle, in a beating heart, with echocardiographic image guidance. The severity of MR is assessed and confirmed with echocardiography, and the reproducibility of the model is reported.

Impact of Mitral Surgery for Mitral Regurgitation on Coexisting Aortic Regurgitation

Background: There is no clear finding on the course of coexisting aortic regurgitation (AR) after treatment of mitral regurgitation (MR). We investigated the effect of mitral surgery for MR on coexisting AR.

Methods: Between January 2008 and December 2016, 75 patients underwent mitral surgery for MR coexisting mild AR. Of these, 65 patients who were available to follow-up postoperative echocardiographic tests 1 year after surgery were included in the present study. Patients were divided into two groups according to the degree of postoperative AR. We investigated the predictive factors for continued AR and perioperative cardiac function.

Results: In all, 22 patients’ AR improved and became less than mild and 43 patients’ persisted at mild or increased. The predictive factor for continued AR was left atrial diameter >50 mm (P = 0.021, odds ratio = 4.739, 95% confidence interval: 1.259–17.846) in multivariate logistic regression analysis. No patients underwent reoperation for continued AR in both groups. However, one patient was rehospitalized for heart failure in the continued AR group.

Conclusion: Left atrial diameter may be an important prognostic factor for continued AR after mitral surgery for MR. MR with mild AR should be treated as soon as before the left atrium expands.

Cardiac remodeling secondary to chronic volume overload is attenuated by a novel MMP9/2 blocking antibody

Objective

Monoclonal antibody derivatives are promising drugs for the treatment of various diseases due to their high matrix metalloproteinases (MMP) active site specificity. We studied the effects of a novel antibody, SDS3, which specifically recognizes the mature active site of MMP9/2 during ventricular remodeling progression in a mouse model of chronic volume overload (VO).

Methods

VO was induced by creating an aortocaval fistula (ACF) in 10- to 12-week-old C57BL male mice. The VO-induced mice were treated with either vehicle control (PBS) or with SDS3 twice weekly by intraperitoneal (ip) injection. The relative changes in cardiac parameters between baseline (day 1) and end-point (day 30), were evaluated by echocardiography. The effects of SDS3 treatment on cardiac fibrosis, cardiomyocyte volume, and cardiac inflammation were tested by cardiac staining with Masson's trichrome, wheat Germ Agglutinin (WGA), and CD45, respectively. Serum levels of TNFα and IL-6 with and without SDS3 treatment were tested by ELISA.

Results

SDS3 significantly reduced cardiac dilatation, left ventricular (LV) mass, and cardiomyocyte hypertrophy compared to the vehicle treated animals. The antibody also reduced the heart-to-body weight ratio of the ACF animals to values comparable to those of the controls. Interestingly, the SDS3 group underwent significant reduction of cardiac inflammation and pro-inflammatory cytokine production, indicating a regulatory role for MMP9/2 in tissue remodeling, possibly by tumor necrosis factor alpha (TNFα) activation. In addition, significant changes in the expression of proteins related to mitochondrial function were observed in ACF animals, these changes were reversed following treatment with SDS3.

Conclusion

The data suggest that MMP9/2 blockage with SDS3 attenuates myocardial remodeling associated with chronic VO by three potential pathways: downregulating the extracellular matrix proteolytic cleavage, reducing the cardiac inflammatory responses, and preserving the cardiac mitochondrial structure and function.

Dynamic Changes in the Molecular Signature of Adverse Left Ventricular Remodeling in Patients With Compensated and Decompensated Chronic Primary Mitral Regurgitation

BACKGROUND

There is no proven medical therapy that attenuates adverse left ventricular remodeling in patients with chronic primary mitral regurgitation (CPMR). Identification of molecular pathways important in the progression of left ventricular remodeling in patients with CPMR may lead to development of new therapeutic strategies.

METHODS AND RESULTS

We performed baseline echocardiographic, cardiac catheterization, and serum NT-pro-BNP analysis in patients with severe CPMR awaiting mitral valve surgery and stratified the study population into compensated or decompensated CPMR. We obtained left ventricular endomyocardial biopsies (n=12) for mRNA expression analysis, and compared baseline transcript levels of 109 genes important in volume-overload left ventricular remodeling with levels in normal hearts (n=5) and between patients with compensated (n=6) versus decompensated (n=6) CPMR. Patients were then randomized to treatment with and without carvedilol and followed until the time of surgery (mean follow-up 8.3 months) when repeat endomyocardial biopsies were obtained to correlate transcriptional dynamics with indices of adverse remodeling. CPMR was associated with increased NPPA expression levels (21.6-fold, P=0.004), decreased transcripts of genes important in cell survival, and enrichment of extracellular matrix genes. Decompensated CPMR was associated with downregulation of SERCA2 (0.77-fold, P=0.009) and mitochondrial gene expression levels and upregulation of genes related to inflammation, the extracellular matrix, and apoptosis, which were refractory to carvedilol therapy.

CONCLUSIONS

Transition to decompensated CPMR is associated with calcium dysregulation, increased expression of inflammatory, extracellular matrix and apoptotic genes, and downregulation of genes important in bioenergetics. These changes are not attenuated by carvedilol therapy and highlight the need for development of specific combinatorial therapies, targeting myocardial inflammation and apoptosis, together with urgent surgical or percutaneous valve interventions.

Mesenchymal stem cell therapy for heart failure: a meta-analysis

BACKGROUND

Mesenchymal stem cell (MSC) treatment has emerged as an important adjunct therapy for heart failure. However, the use of MSC to treat heart failure has not been well established. We conducted a systematic review and meta-analysis to evaluate the efficacy of MSC treatment for heart failure.

METHODS

PubMed, Embase, and the Cochrane Central Register of Controlled Trials were searched. Randomized controlled trials (RCTs) assessing the influence of MSC treatment on cardiac function in heart failure were included in this analysis. Two investigators independently searched the articles, extracted data, and assessed the quality of the included studies. Meta-analysis was performed using the fixed-effect model or random-effect model when appropriate.

RESULTS

Six RCTs involving 625 patients were included in the meta-analysis. Compared with control interventions in heart failure patients, MSC treatment had no significant influence on cardiovascular death (RR = 0.76; 95% CI = 0.38-1.52; p = 0.43); however, it was associated with significantly increased left ventricular ejection fraction (LVEF; mean = 9.64; 95% CI = 7.56-11.71; p < 0.00001) and reduced rehospitalization rate (RR = 0.41; 95% CI = 0.23-0.73; p = 0.003). In addition, no significant difference between the two groups was observed for the incidence of myocardial infarction (RR = 0.72; 95% CI = 0.10-5.02; p = 0.74), the recurrence of heart failure (RR = 0.88; 95% CI = 0.28-2.81; p = 0.83), and total death (RR = 0.68; 95% CI = 0.37-1.25; p = 0.21).

CONCLUSION

Although MSC treatment can significantly improve LVEF and reduce rehospitalization rates, it does not have a significant influence on cardiovascular death, myocardial infarction, heart failure, and total death.