Slope of the Anterior Mitral Valve Leaflet: A New Measurement of Left Ventricular Unloading for Left Ventricular Assist Devices and Systolic Dysfunction

Left ventricular assist device (LVAD)-supported patients are evaluated routinely with use of transthoracic echocardiography. Values of left ventricular unloading in this unique patient population are needed to evaluate LVAD function and assist in patient follow-up.We introduce a new M-mode measurement, the slope of the anterior mitral valve leaflet (SLAM), and compare its efficacy with that of other standard echocardiographically evaluated values for left ventricular loading, including E/e′ and pulmonary artery systolic pressures. Average SLAM values were determined retrospectively for cohorts of random, non-LVAD patients with moderately to severely impaired left ventricular ejection fraction (LVEF) (<0.35, n=60). In addition, pre- and post-LVAD implantation echocardiographic images of 81 patients were reviewed.The average SLAM in patients with an LVEF <0.35 was 11.6 cm/s (95% confidence interval, 10.4–12.8); SLAM had a moderately strong correlation with E/e′ in these patients. Implantation of LVADs significantly increased the SLAM from 7.3 ± 2.44 to 14.7 ± 5.01 cm/s (n=42, P <0.0001). The LVAD-supported patients readmitted for exacerbation of congestive heart failure exhibited decreased SLAM from 12 ± 3.93 to 7.3 ± 3.5 cm/s (n=6, P=0.041). In addition, a cutpoint of 10 cm/s distinguished random patients with LVEF <0.35 from those in end-stage congestive heart failure (pre-LVAD) with an 88% sensitivity and a 55% specificity.Evaluating ventricular unloading in LVAD patients remains challenging. Our novel M-mode value correlates with echocardiographic values of left ventricular filling in patients with moderate-to-severe systolic function and dynamically improves with the ventricular unloading of an LVAD.     

Papillary Muscle Repositioning as a Subvalvular Apparatus Preservation Technique in Mitral Stenosis Patients with Normal Left Ventricular Systolic Function

Subvalvular apparatus preservation is an important concept in mitral valve replacement (MVR) surgery that is performed to remedy mitral regurgitation. In this study, we sought to determine the effects of papillary muscle repositioning (PMR) on clinical outcomes and echocardiographic left ventricular function in rheumatic mitral stenosis patients who had normal left ventricular systolic function.We prospectively assigned 115 patients who were scheduled for MVR surgery with mechanical prosthesis to either PMR or MVR-only groups. Functional class and echocardiographic variables were evaluated at baseline and at early and late postoperative follow-up examinations. All values were compared between the 2 groups.The PMR group consisted of 48 patients and the MVR-only group of 67 patients. The 2 groups’ baseline characteristics and surgery-related factors (including perioperative mortality) were similar. During the 18-month follow-up, all echocardiographic variables showed a consistent improvement in the PMR group; the mean left ventricular ejection fraction deteriorated significantly in the MVR-only group. Comparison during follow-up of the magnitude of longitudinal changes revealed that decreases in left ventricular end-diastolic and end-systolic diameters and in left ventricular sphericity indices, and increases in left ventricular ejection fractions, were significantly higher in the PMR group than in the MVR-only group.This study suggests that, in patients with rheumatic mitral stenosis and preserved left ventricular systolic function, the addition of papillary muscle repositioning to valve replacement with a mechanical prosthesis improves left ventricular dimensions, ejection fraction, and sphericity index at the 18-month follow-up with no substantial undesirable effect on the surgery-related factors.Key words: Cardiac output, chordae tendineae/surgery, left ventricular function, mitral valve replacement, mitral valve stenosis/surgery, papillary muscles/surgery, subvalvular apparatus, tissue preservation/methods, ventricular function, leftMitral valve replacement (MVR) with a mechanical or a bioprosthetic valve is one of the most performed cardiac surgical procedures. Although in recent years valve repair has usually been preferred to replacement, MVR is inevitable when repair is not feasible. After MVR, low cardiac output syndrome develops in some patients, because the subvalvular apparatus has not been spared.¹ Because the subvalvular apparatus provides continuity between the mitral annulus and the left ventricular (LV) wall through the leaflets, chordae tendineae, and papillary muscles, it plays an important role in LV function.² Several studies^3–3 have shown that protection of the subvalvular apparatus during MVR can decrease the risk of low cardiac output syndrome, reduce the operative mortality rate, and improve postoperative LV systolic function. Various approaches to subvalvular apparatus preservation have been developed.^6–9Papillary muscle repositioning (PMR) is a subvalvular apparatus-sparing method that can be applied to both the anterior and posterior mitral annulus. In patients with LV dysfunction and mitral regurgitation, several studies^10,11 have shown favorable effects of papillary muscle repositioning on LV remodeling; however, the effect of subvalvular-apparatus-sparing surgery (including PMR) on LV mechanics has not yet been fully elucidated in patients who have isolated mitral stenosis and preserved LV function.^12,13In this study, we examined the effectiveness of PMR on LV function and clinical outcome in patients with isolated mitral stenosis and preserved LV systolic function who undergo MVR.     

Idiopathic Focal Ventricular Arrhythmias Originating from the Anterior Papillary Muscle in the Left Ventricle

Introduction: Focal ventricular arrhythmias (VAs) have been reported to arise from the posterior papillary muscle in the left ventricle (LV). We report a distinct subgroup of idiopathic VAs arising from the anterior papillary muscle (APM) in the LV.
Methods and Results: We studied 432 consecutive patients undergoing catheter ablation for VAs based on a focal mechanism. Six patients were identified with ventricular tachycardia (VT, n = 1) or premature ventricular contractions (PVCs, n = 5) with the earliest site of ventricular activation localized to the base (n = 3) or middle portion (n = 3) of the LV APM. No Purkinje potentials were recorded at the ablation site during sinus rhythm or the VAs. All patients had a normal baseline electrocardiogram and normal LV systolic function. The VAs exhibited a right bundle branch block (RBBB) and right inferior axis (RIA) QRS morphology in all patients. Oral verapamil and/or Na⁺ channel blockers failed to control the VAs in 4 patients. VT was not inducible by programmed electrical stimulation in any of the patients. In 4 patients, radiofrequency current with an irrigated or conventional 8-mm-tip ablation catheter was required to achieve a lasting success. Two patients had recurrent PVCs after a conventional radiofrequency ablation with a 4-mm-tip ablation catheter had initially suppressed the arrhythmia.
Conclusions: VAs may arise from the base or middle portion of the APM and are characterized by an RBBB and RIA QRS morphology and focal mechanism. Catheter ablation of APM VAs is typically challenging, and creation of a deep radiofrequency lesion may be necessary for long-term success.     

左心室向心性肥厚发展与收缩功能

目的与方法:运用M型超声心动图探讨高血压病向心性肥厚程度与收缩功能的相关关系.结果:收缩功能(心率校正的FS,y轴)与向心性肥厚程度(左室重量与左室容积之比LVM/LVCV,x轴)的呈曲线相关关系,其曲线方程为y=-31.139x2+146.192x1-130.43.LVM/LVCV为2.35时,其心率校正的FS为最大41.63.结论:在心肌肥厚的初期,心肌肥厚使左心室的收缩功能起代偿性增强,当心肌增厚到一定程度时,左室收缩功能随心肌进一步肥厚而呈下降趋势.     

左心室向心性肥厚发展与收缩功能

目的与方法：运用Ｍ型超声心动图探讨高血压病向心性脑厚程度与收缩功能的相关关系。方法：收缩功能（心率校正的ＦＳ,ｙ轴）与向心性肥厚程度（左室重量与左室容积之比ＬＶＭ／ＬＶＣＶ,ｘ轴）的呈曲线相关关系,其曲线方程为ｙ＝－３１．１３９ｘ２＋１４６．１９２ｘ１－１３０．４３。ＬＶＭ／ＬＶＣＶ为２．３５时,其心率校正的ＦＳ为最大４１．６３。结论：在心肌肥厚的初期,心肌肥厚使左心室的收缩功能起代偿性增强,当心肌增厚到一定程度时,左室收缩功能随心肌进一步肥厚而呈下降趋势。     

单纯收缩期高血压患者左心室肥厚与室性心律失常的关系

目的探讨单纯收缩期高血压的病人左室肥厚与心律失常的关系。方法采用２４ｈ动态心电图和彩色多普勒超声观察患者左室肥厚及心律失常的发生情况，并观察单纯收缩期高血压与舒张期高血压左室结构改变。结果左室肥厚组室性心律失常发生率明显高于非左室肥厚组（Ｐ＞０．０１），单纯收缩期高血压组左室肥厚高于舒张期高血压组。结论左室肥厚可使室性心律失常发生率增加，收缩压增高较舒张压增高更易导致左室肥厚。     

组织运动二尖瓣环位移自动追踪技术对正常人左心室收缩功能的评价

目的探讨组织运动二尖瓣环位移自动追踪技术(TMAD),作为评价左心室整体收缩功能的可行性和准确性。方法选择健康志愿者50名,采用常规二维超声测量其左心室舒张末期内径(LVEDd)、舒张末期容积(LVEDV)、收缩末期容积(LVESV),用简化双平面Simpson法计算左心室射血分数(LVEF),通过TMAD技术测量二尖瓣环6个位点的收缩期最大位移(Ds),并计算其平均值(MDs),对LVEF和MDs进行相关性分析。结果二尖瓣环6个位点MDs,与简化双平面Simpson法计算的LVEF呈显著正相关(r=0.86,P<0.01),同时发现LVESV与LVEF、MDs有较好的相关性(r=0.51,P<0.05;r=0.480,P<0.05),而LVEDd、LVEDV与LVEF、MDs无较好的相关性。结论 TMAD技术可以用来作为评价左心室收缩功能的一个新方法,其远期效果有待进一步探讨。     

Electrosurgical Detachment of MitraClips From the Anterior Mitral Leaflet Prior to Transcatheter Mitral Valve Implantation

ObjectivesThe aim of this study was to test the hypothesis that transcatheter electrosurgery might allow intentional detachment of previously placed MitraClip(s) from the anterior leaflet to recreate a single mitral orifice for transcatheter mitral valve implantation (TMVI), leaving the retained MitraClip(s) securely fastened to the posterior leaflet and without interfering with the mitral bioprosthesis.BackgroundPatients with severe mitral regurgitation or stenosis despite edge-to-edge mitral repair with the MitraClip typically have few therapeutic options because the resultant double orifice precludes TMVI. Transcatheter electrosurgery may allow detachment of failed MitraClip(s) from the anterior leaflet to recreate a single orifice for TMVI.MethodsThis was a single-center, 5-patient, consecutive, retrospective observational cohort. Patients underwent transcatheter electrosurgical laceration and stabilization of failed MitraClip(s) to recreate a single orifice, leaving the MitraClip(s) securely fastened to the posterior leaflet. Subsequently, patients underwent TMVI with an investigational device, the Tendyne mitral bioprosthesis, on a compassionate basis. Patients were followed up to 30 days.ResultsMitraClip detachment from the anterior leaflet and Tendyne implantation were successful in all patients. All patients survived to discharge. All patients were discharged with grade 0 central mitral regurgitation. Two patients had moderate perivalvular mitral regurgitation that did not require reintervention. During the follow-up period of 30 days, there were no deaths, cases of valve dysfunction, or reintervention. There was no evidence of erosion or bioprosthetic valve dysfunction attributable to the retained MitraClip(s) still attached to the posterior leaflet.ConclusionsTranscatheter electrosurgical detachment of failed MitraClips from the anterior leaflet followed by TMVI is technically feasible and safe at 30 days. Longer term study is needed to determine the clinical benefit of this approach and new algorithms for TMVI sizing following electrosurgical laceration and stabilization of a failed MitraClip to avoid perivalvular leak.     

Systolic Papillary Muscle Dyssynchrony Predicts Recurrence of Mitral Regurgitation in Patients with Ischemic Cardiomyopathy (ICM) Undergoing Mitral Valve Repair

Objective: We investigated the impact of papillary muscle dyssynchrony (DYS‐PAP) in predicting recurrent mitral regurgitation (MR) in patients with ischemic cardiomyopathy (ICM) undergoing undersized mitral ring annuloplasty (UMRA). Methods: One hundred forty‐four ICM patients (left ventricular ejection fraction <35%) in sinus rhythm undergoing UMRA between January 2001 and December 2010 at three Institutions (University Hospital, Maastricht, The Netherlands; Careggi Hospital, Florence, Italy; Civic Hospital, Brescia, Italy) were recruited. The primary endpoint was the recurrence of MR at the latest echocardiographic study defined as insufficiency ≥2+ in patients with no/trivial MR at discharge. The assessment of DYS‐PAP was performed by applying two‐dimensional (2D) speckle‐tracking imaging. Results: In patients with MR recurrence, DYS‐PAP significantly worsened (84.1 ± 8.8 msec vs.65.4 ± 8.8 msec at baseline, P < 0.001) whereas in patients with no MR recurrence, DYS‐PAP did not vary (22.3 ± 5.3 msec vs. 25.9 ± 7.2 msec at baseline, P = 0.8). Recurrent MR was positively correlated with preoperative DYS‐PAP (P < 0.001), baseline anterior mitral leaflet tethering angle α (P < 0.001) and tethering symmetry index α/β before surgery (P < 0.001). There was no significant correlation between MR recurrence and other echocardiographic parameters. Logistic regression analysis revealed that baseline values of DYS‐PAP (OR: 5.4 [95% CI: 3.1–7.7], P < 0.001), α (OR: 5.0 [2.6–6.7], P < 0.001), and α/β (OR: 3.9 [2.5–5.7], p < 0.001) were predictors of recurrent MR. A DYS‐PAP value ≥ 58 msec predicted recurrence of MR with 100% sensitivity and 83% specificity (area under the curve [AUC]: 0.92 [0.7–1], P < 0.001). Conclusions: A DYS‐PAP cutoff value of 58 msec is useful to identify patients in whom UMRA is likely to fail. That way decision making in ischemic functional MR might be facilitated.     

Mitral Valve Repair for Anterior/Bi-leaflet Versus Posterior Leaflet Degenerative Mitral Valve Disease: A Systematic Review and Meta-analysis

Mitral valve repair (MVr) secondary to degenerative anterior/bi-leaflet mitral valve disease is more challenging than posterior leaflet repair. However, conclusive evidence is needed to make decisions based on the outcomes rather than technical difficulties. This meta-analysis compares anterior/bi-leaflet MVr with isolated posterior leaflet repair in patients with mitral regurgitation (MR) due to degenerative mitral valve disease. The outcomes of interest were long-term (≥ 5 years) survival and freedom from re-operation and moderate-to-severe MR. Meta-analysis of 10 studies showed that there was no significant difference in long-term survival (risk ratio, RR: 1.00; 95% confidence interval, 95% CI 0.96-1.04), freedom from moderate-to-severe MR (RR: 0.95; 95% CI 0.87-1.03), and freedom from re-operation (RR: 0.96; 95% CI 0.90-1.02) between anterior/bi-leaflet MVr and posterior leaflet repair. As outcomes of anterior/bilateral repair were comparable with those of isolated posterior leaflet repair, our findings do not support the inclination towards replacement over repair for MR caused by anterior/bilateral degenerative mitral disease.     

Transesophageal Echocardiographic Analysis of the Systolic Pattern of the Anterior Mitral Leaflet in Patients with Flat Chest

Transesophageal echocardiography was conducted to determine the systolic pattern of the anterior mitral leaflet in patients with flat chest, and to differentiate it from that associated with mitral valve prolapse. The fronto-sagittal index (an index of chest flattening) was determined in 50 subjects using chest radiographs, and was used to classify them into a flat chest group (index < 0.38, n = 28) and a normal chest group (index ≥ 0.38, n = 22). We then used transesophageal echocardiography to examine the anterior leaflet in these subjects. A significant positive correlation was observed between the fronto-sagittal index and the short-to long-axis diameter ratio of the left ventricle in all patients. These parameters, and the left atrial dimension were lower in the flat than the normal chest group. The clear zone area of the anterior leaflet during mid-to late-systole was significantly larger in the flat chest group. However, no intergroup differences existed in the rough zone area of the anterior leaflet or in the middle scallop area of the posterior leaflet. Mitral regurgitation was observed in 20 and 12 subjects in the flat and normal chest groups, respectively. The maximum mitral regurgitant area did not differ between the two groups. The clear zone area of the anterior leaflet increased significantly following inhalation of amyl nitrite in 22 subjects of both groups, but the other areas did not increase. The mitral regurgitant area decreased or disappeared after amyl nitrite at a similar rate in each group. Thus, the decrease in the antero-posterior dimension of the thorax in subjects with flat chest affects the systolic pattern of the clear zone of the anterior leaflet more than that of the rough zone of the anterior leaflet or the posterior leaflet. This systolic pattern in such patients differs from that associated with mitral valve prolapse.     

Temporal Changes in Interpapillary Muscle Dynamics as an Active Indicator of Mitral Valve and Left Ventricular Interaction in Ischemic Mitral Regurgitation

Background

Regional subpapillary myocardial hypokinesis may impair lateral reduction in the interpapillary muscle distance (IPMD) from diastole to systole, and adversely affect mitral valve geometry and tethering.

Objectives

The goal of this study was to investigate the impact of impaired lateral shortening in the interpapillary muscle distance on mitral valve geometry and function in ischemic heart disease.

Methods

To quantify ventricular size/shape, regional myocardial contraction, lateral shortening of the IPMD, mitral valve geometry, and severity of mitral regurgitation, 67 patients with ischemic heart disease underwent cardiac magnetic resonance imaging, and a correlation analysis of measured parameters was performed. The impact of reduced IPMD shortening on mitral valve (dys)function was confirmed in swine and in a physiological computational mitral valve model.

Results

Lateral shortening of the IPMD from diastole to systole was severely reduced in patients with moderate/severe ischemic mitral regurgitation (9.6 ± 2.8 mm), but preserved in mild IMR (11.5 ± 3.4 mm). Left ventricular size and ejection fraction did not differ between the groups. In swine with subpapillary infarction and impaired IPMD, mitral regurgitation was evident within 1 week, compared to those pigs with a nonpapillary infarction and preserved IPMD. In the controlled computational valve model, IPMD had the maximal impact on regurgitation, and was exacerbated with additional annular dilation.

Conclusions

By using cardiac magnetic resonance imaging in humans, we demonstrated that it is the impairment of lateral shortening between the papillary muscles, and not passive ventricular size, that governs the severity of mitral regurgitation. Loss of lateral shortening of IPMD tethers the leaflet edges and impairs their systolic closure, resulting in mitral regurgitation, even in small ventricles. Understanding the lateral dynamics of ventricular-valve interactions could aid the development of new repair techniques for ischemic mitral regurgitation.