Different influences of left ventricular remodeling on anterior and posterior mitral leaflet tethering

Assessment of mitral valve geometry in nonvalvular atrial fibrillation patients with or without ventricular dysfunction: insights from high volume rate three-dimensional transesophageal echocardiography

Meticulous understanding of the mechanisms underpinning mitral regurgitation in atrial fibrillation (AF) patients is crucial to optimize therapeutic strategies. The morphologic characteristics of mitral valves in atrial functional mitral regurgitation (FMR) patients with and without left ventricular (LV) dysfunction were evaluated by high volume rate (HVR) three-dimensional transesophageal echocardiography (3D-TEE). In our study, 68 of 265 AF patients who underwent 3D-TEE were selected, including 36 patients with AF, FMR, and preserved LV function (AFMR group) and 32 patients with AF, FMR, and LV dysfunction (VFMR group). In addition, 36 fever patients without heart disease were included in the control group. Group comparisons were performed by one-way analysis of variance for continuous variables. The left atrium (LA) was enlarged in the AFMR and VFMR groups compared with the control group. The mitral annulus (MA) in the AFMR group was enlarged and flattened compared with the control group and was smaller than in the VFMR group. The annulus area fraction was significantly diminished in the AFMR and VFMR groups, indicative of reduced MA contractility. The posterior mitral leaflet (PML) angle was smallest in the AFMR group and largest in the control group, whereas the distal anterior mitral leaflet angle did not significantly differ among the three groups. LA remodeling causes expansion of the MA and reduced MA contractility, disruption of the annular saddle shape, and atriogenic PML tethering. Comparison of atrial FMR patients with and without LV dysfunction indicates that atriogenic PML tethering is an important factor that aggravates FMR. HVR 3D-TEE improves the 3D temporal resolution greatly.

Predictors of residual mitral regurgitation after left ventricular assist device implantation

Patients with advanced heart failure often have functional mitral regurgitation. Left ventricular assist device implantation improves functional mitral regurgitation through left ventricular unloading. However, residual mitral regurgitation after left ventricular assist device implantation leads to adverse outcomes, and whether patients need concomitant mitral valve surgery is not fully elucidated. Therefore, this study aimed to elucidate the predictors of residual mitral regurgitation and to describe the temporal changes in residual mitral regurgitation. We retrospectively enrolled 15 patients with implantable continuous-flow left ventricular assist device, who had significant mitral regurgitation on echocardiography before left ventricular assist device implantation. Three patients had residual mitral regurgitation (mitral regurgitation color jet area/left atrial area >0.2) 1 month after left ventricular assist device implantation. We investigated factors associated with residual mitral regurgitation and compared patients with or without residual mitral regurgitation. On univariate analysis, mitral valve tethering area and mitral regurgitation vena contracta before left ventricular assist device implantation were significantly associated with residual mitral regurgitation (odds ratio, 1.03; p = 0.036 and odds ratio, 10.45; p = 0.0087). One month after left ventricular assist device implantation, the mean pulmonary capillary wedge pressure and pulmonary artery pressure were higher in patients with residual mitral regurgitation (pulmonary capillary wedge pressure: 11.3 ± 3.5 vs 6.4 ± 3.4 mmHg, p = 0.029 and pulmonary artery pressure: 21.3 ± 4.0 vs 15.9 ± 3.3 mmHg, p = 0.023). However, the mitral regurgitation grading and hemodynamics were not significantly different 6 months after left ventricular assist device implantation. The hospitalization-free survival was not significantly different between the two groups. Mitral valve tethering area and mitral regurgitation vena contracta were predictors of residual mitral regurgitation. Residual mitral regurgitation improved until 6 months after left ventricular assist device implantation and might not affect the prognosis.

Ischemic Mitral Regurgitation: Current Understanding and Surgical Options

Secondary, or functional, mitral regurgitation (MR) occurs with impaired coaptation of structurally normal valve leaflets due to abnormal structure and/or function of the left ventricle (LV). A leading cause of functional mitral regurgitation is ischemic cardiomyopathy, resulting in left ventricular dysfunction and subsequent congestive heart failure (CHF) and ischemic mitral regurgitation (IMR). The value of surgical or transcatheter correction of IMR remains controversial, since the underlying pathology of IMR is attributed to a dysfunctional left ventricle. However, even mild IMR has been shown to be harmful to CHF patients, as IMR is both a surrogate of advanced CHF and an independent contributor to CHF morbidity and mortality. While observational and randomized studies have examined surgical treatment of IMR with conflicting outcomes, additional well-designed randomized controlled trials should be performed to further clarify the optimal treatment for IMR. Additionally, close attention should be paid to the quality of interventions performed, as durable reduction in IMR provides the best hope of a positive clinical outcome. This review focuses on the pathophysiology of IMR, current evidence regarding surgical and transcatheter interventions, and future directions in management of IMR.

Usefulness of three-dimensional spherical index to assess different types of left ventricular remodeling: A meta-analysis

BACKGROUND

Left ventricular (LV) remodeling after myocardial injury, volume or pressure overload is characterized by a change in LV shape from an ellipse to more of a sphere. The usefulness of 3-dimensional (3D) sphericity index (SpI) for accurate evaluation of LV remodeling remains uncertain despite extensive research.

METHODS

We searched Pubmed, Embase, Web of Science, and Cochrane databases to identify relevant studies from January 1, 1990 to August 1, 2016. The quality of each study was evaluated using the Newcastle-Ottawa Scale. Meta regression and sensitivity and subgroup analyses based on patterns of LV remodeling were performed.

RESULTS

Thirteen studies with a total of 1064 patients were included in this meta-analysis. There was evidence of obvious heterogeneity (I = 82.4%; P < .001), which was mainly accounted for by the pattern of remodeling according to meta-regression. The result of subgroup meta-analyses suggested that SpI in patients with eccentric remodeling was significantly higher compared with control group (95% confidence interval [CI], 0.78-1.10). No statistic difference was found in LV SpI between healthy controls and patients with concentric hypertrophy (95% CI, -0.89 to 0.16) or myocardial injury (95% CI, -0.13 to 0.41).

CONCLUSION

3D SpI can be widely used to assess LV remodeling in patients with eccentric remodeling, but has limitations in predicting concentric hypertrophy and regional or chronic myocardial injury.

Assessment of deformation of the mitral valve complex during off-pump coronary artery bypass surgery using three-dimensional echocardiography in a porcine model

BACKGROUND

This study aimed to assess the deformation of the mitral valve complex during the displacement of the beating heart by using three-dimensional echocardiography in a porcine off-pump coronary artery bypass grafting (OPCAB) model.

METHODS

In nine healthy swine, we positioned the beating heart as an OPCAB model, i.e. control, left anterior descending artery (LAD), right coronary artery (RCA), and left circumflex artery (LCX) positions. In each position, three-dimensional echocardiography was performed to assess the mitral valve complex with hemodynamic parameters. We analyzed the deformation of the mitral valve and the three-dimensional coordinates of the papillary muscles.

RESULTS

There was a significant increase in maximum tenting length and tenting volume (control 0.70±0.30, LAD 0.65±0.27, RCA 0.79±0.23, LCX 0.95±0.34cm³, p<0.05) in the LCX position compared with the other positions. The posterior papillary muscle (PPM) angle had a significant relationship with the tenting volume (r=-0.643, p<0.001). The PPM was displaced to the medial side in the LAD and LCX positions (p<0.01).

CONCLUSIONS

The prime cause of the deformation of the mitral leaflets is suggested to be the displacement of the PPM associated with the change in geometry of the left ventricle in a porcine model.

Numerical prediction of thrombus risk in an anatomically dilated left ventricle: the effect of inflow cannula designs

BACKGROUND

Implantation of a rotary blood pump (RBP) can cause non-physiological flow fields in the left ventricle (LV) which may trigger thrombosis. Different inflow cannula geometry can affect LV flow fields. The aim of this study was to determine the effect of inflow cannula geometry on intraventricular flow under full LV support in a patient specific model.

METHODS

Computed tomography angiography imaging of the LV was performed on a RBP candidate to develop a patient-specific model. Five inflow cannulae were evaluated, which were modelled on those used clinically or under development. The inflow cannulae are described as a crown like tip, thin walled tubular tip, large filleted tip, trumpet like tip and an inferiorly flared cannula. Placement of the inflow cannula was at the LV apex with the central axis intersecting the centre of the mitral valve. Full support was simulated by prescribing 5 l/min across the mitral valve. Thrombus risk was evaluated by identifying regions of stagnation. Rate of LV washout was assessed using a volume of fluid model. Relative haemolysis index and blood residence time was calculated using an Eulerian approach.

RESULTS

The inferiorly flared inflow cannula had the lowest thrombus risk due to low stagnation volumes. All cannulae had similar rates of LV washout and blood residence time. The crown like tip and thin walled tubular tip resulted in relatively higher blood damage indices within the LV.

CONCLUSION

Changes in intraventricular flow due to variances in cannula geometry resulted in different stagnation volumes. Cannula geometry does not appreciably affect LV washout rates and blood residence time. The patient specific, full support computational fluid dynamic model provided a repeatable platform to investigate the effects of inflow cannula geometry on intraventricular flow.

Surgical strategy for ischemic mitral regurgitation adopting subvalvular and ventricular procedures

PURPOSE

The progression of left ventricular (LV) remodeling and subsequent mitral valve tethering impair the results of reduction annuloplasty for ischemic mitral regurgitation (MR).

METHODS

We studied 90 patients who underwent surgical repair of ischemic MR between 1999 and 2013 according to our surgical strategy adding submitral and ventricular procedures to annuloplasty as follows: annuloplasty alone (stage 1, n = 30), additional papillary muscle approximation (PMA) for progression of tethering (stage 2, n = 26), and additional left ventriculoplasty with PMA for progression of LV remodeling and tethering (stage 3, n = 34).

RESULTS

The preoperative New York Heart Association (NYHA) functional classes (2.5 ± 0.7, 3.1 ± 0.7 and 3.3 ± 0.7 for stages 1, 2 and 3, respectively, P <0.001), LV end-diastolic diameters (56 ± 7 mm, 66 ± 5 mm and 70 ± 7 mm, P <0.001), and LV ejection fractions (45 ± 12%, 32 ± 9% and 27 ± 9%, P <0.001) significantly differed among the stages. In contrast, the MR grades did not significantly differ (2.9 ± 0.8, 3.0 ± 1.0, and 2.9 ± 1.1, respectively; P = 0.93). Both the rates of cardiac-related survival and freedom from reoperation were comparable among the 3 groups (log-rank P = 0.92 and 0.58, respectively).

CONCLUSION

Additional submitral and ventricular procedures can compensate for the possible impairment of the outcomes after annuloplasty alone for ischemic MR in patients with severe LV remodeling and tethering.

Posterior leaflet segment 2 plication in ischemic mitral regurgitation repair

Aim

To evaluate the medium-term results of plication of posterior leaflet segment 2 in addition to ring annuloplasty in patients with functional ischemic mitral regurgitation.

Methods

The study included 136 patients who underwent mitral valve repair with plication of posterior leaflet segment 2 for ischemic mitral regurgitation between 2004 and 2012. The direction and correlation of left ventricle sphericity and tethering area were established by Pearson correlation analysis in patients with or without recurrent mitral regurgitation in the medium term.

Results

Medium-term survival was 91.9% and freedom from moderate or severe mitral regurgitation was 89.6%. In medium-term follow-up, transthoracic echocardiography found a significant decrease in tethering area, coaptation height, and distance between the commissures compared to the pre-surgery values ( p = 0.0001 in all). The distance between the papillary muscles was reduced compared to the pre-surgery period but it was not significant ( p = 0.204). Pearson correlation analysis found no significant correlation between the tethering area and left ventricle sphericity in patients without recurrent mitral regurgitation ( r = 0.15, p = 0.36), a highly positive correlation ( r = 0.44, p < 0.001) in patients with mild recurrent mitral regurgitation, and a moderately positive correlation ( r = 0.71, p < 0.01) in patients with moderate or severe recurrent mitral regurgitation.

Conclusions

The tethering area, coaptation height, and distance between the commissures decreased significantly, thus posterior leaflet segment 2 plication in addition to ring annuloplasty may be the optional procedure to ensure freedom from moderate or severe mitral regurgitation.

Benefits of submitral procedures for ischemic mitral regurgitation

The surgical strategy for ischemic mitral regurgitation (MR) remains controversial. Ischemic MR is a secondary valve disease caused by left ventricular (LV) remodeling and subsequent papillary muscle displacement, usually without structural valve lesions. Reduction annuloplasty is the standard surgical procedure for this condition, though it cannot clearly provide a survival benefit for those with LV dysfunction and is associated with a high prevalence of late recurrence of MR. The valvular procedure alone could be insufficient to treat ischemic MR in terms of long-term survival and the prevention of recurrence because ischemic MR is primarily a ventricular disorder. Thus, recent studies have focused on alternative procedures that target the primary cause of ischemic MR, the papillary muscles and left ventricle. We believe that the appropriate selection of surgical procedures among valvular, subvalvular, and even ventricular ones, considering the severity of LV remodeling for each patient would be more beneficial. Here we review recent studies featuring various surgical approaches to ischemic MR, especially with submitral procedures.

Pre-operative echocardiographic features associated with persistent mitral regurgitation after left ventricular assist device implantation

BACKGROUND

Previous studies have shown remarkable decrease in size of the left ventricle after left ventricular assist device (LVAD) implantation due to mechanical unloading. However, a certain number of patients continue to have significant mitral regurgitation (MR) under LVAD support. We investigated pre-operative echocardiographic features associated with persistent MR after LVAD implantation.

METHODS

We retrospectively reviewed 82 consecutive patients undergoing continuous-flow LVAD implantation between 2007 and 2010. We obtained echocardiograms performed within 2 weeks before and 1 week after surgery. We investigated the pre-operative echocardiographic findings associated with significant MR post-LVAD and compared 1-year mortality after LVAD surgery between patients with and without significant MR post-LVAD.

RESULTS

MR was significant in 43 patients (52.4%) before LVAD surgery. Among those, 5 underwent concomitant mitral valve repair (MVr) at the time of LVAD implantation. Of the remaining 38 patients, 25 (65.8%) showed improvement of MR, whereas 13 patients (34.2%) continued to have significant MR post-LVAD. Multivariate analysis revealed that posterior displacement of the coaptation point of mitral leaflets was significantly associated with significant MR post-LVAD (hazard ratio, 1.335; 95% confidence interval, 1.035-1.721; p = 0.026) even after adjusting for the amount of pre-operative MR flow. Post-LVAD 1-year survival of patients with and without significant MR post-LVAD was not significantly different (92.3% vs 89.1%, p = 0.826).

CONCLUSIONS

Pre-LVAD posterior displacement of mitral leaflets may be indicative of post-operative significant MR, which would help identify echocardiographic features of functional MR refractory to simple volume reduction of the ventricle.