Mean Ring Size Research Articles

Left ventricle–mitral valve ring size mismatch following ring annuloplasty for nonischemic dilated cardiomyopathy

BackgroundIn patients with ischemic mitral regurgitation (MR) undergoing restrictive mitral annuloplasty (RMA), the ratio of left ventricular (LV) end-systolic dimension (LVESD) to mitral valve (MV) ring size (ie, LV–MV ring mismatch) is associated with postoperative recurrent MR. However, the impact of LV–MV ring mismatch on postoperative recurrent MR, LV function recovery, and long-term survival in patients with nonischemic dilated cardiomyopathy (DCM) remains unknown. MethodsSixty-six patients with nonischemic DCM (mean LVESD, 62 mm) underwent RMA (mean ring size, 26 mm) between 2003 and 2014. Recurrent MR was defined as MR grade ≥2+ at a 6-month echocardiographic evaluation. ResultsAt the 6-month follow-up, 23 patients (35%) had developed recurrent MR. In univariable logistic regression analysis, larger LVESD (P = .012) and LVESD/ring size ratio (P = .008) were associated with recurrent MR. In multivariable models adjusted for age, sex, baseline LV ejection fraction, and severe MR, only LVESD/ring size ratio (odds ratio, 4.65; 95% confidence interval, 1.04-25.0; P = .048) remained significantly associated with MR recurrence. Receiver operating characteristic curve analysis demonstrated an optimal cutoff value for the LVESD/ring size ratio of 2.42. Patients with an LVESD/ring size ratio >2.42 (n = 30; mismatch) had a lower 5-year cumulative survival rate compared with those with an LVESD/ring size ratio ≤2.42 (n = 36; nonmismatch) (52% vs 71%; P = .045). Postoperatively, LV dimensions were significantly reduced in both groups; however, improvements in LVEF were only modest in the mismatched group (P = .091). ConclusionsLV–MV ring size mismatch was associated with an increased risk of recurrent MR in our series. This finding may aid the formulation of surgical strategies for patients with nonischemic DCM.

Implante de neocuerdas con una medida estándar para reparación de la válvula mitral

IntroductionMitral valve repair with polytetrafluoroethylene neochord is currently the gold standard of treatment, based on the respect rather than resect approach. Different challenging and complicated techniques have been developed to measure the exact length of the neochord. Our objective is to describe the loop technique with a standard measurement in mitral repair. Materials and methodsA descriptive study was conducted on a retrospective cohort of 34 consecutive patients, from January 2011 to October 2017. All patients underwent the implanting of a neochord using an in-house loop technique. The length of the neochord was pre-measured with 15mm for the posterior leaflet and 25mm for the anterior leaflet, based on the echocardiographic measurements of other authors. An evaluation was made of valvular competence at the weaning of extracorporeal circulation using transoesophageal echocardiography was evaluated, with an early follow-up with transthoracic echocardiography. ResultsThe video-assisted mini-thoracotomy approach was performed in 70.5% (24/34) of cases, and by conventional sternotomy in 29.4% (10/34). The anterior leaflet was repaired in 26.4% (9/34), the posterior in 61.7% (21/34), and both in 11.7% (4/34). Annuloplasty was performed with a rigid ring in 79.4%, and semi-rigid in 20% of cases. The mean ring size was 29.9±2.0. The intraoperative echocardiogram did not show any grade of failure in 82.3% (28/34), and mild insufficiency in 17.6% (6/34). No patient undergoing minimally invasive surgery required conversion. The extracorporeal circulation time was 158±38minutes and clamping 116±31min. No patient required resection or adjustment of the neochord measurement or conversion to replacement. There were 2cases of hospital mortality; the first due to hypovolaemic shock and the second due to septic shock of pulmonary origin. In the early follow-up with a mean of 8 months (1-40), 82.3% (28/34) did not present with mitral regurgitation, and 17.6% (6/34) had grade I insufficiency. ConclusionThe proposed technique with preformed loops of polytetrafluoroethylene neochord with standardised measurement showed reliable preliminary results. Studies with long-term follow-up would be necessary.

Computer-based comparison of different methods for selecting mitral annuloplasty ring size

BackgroundRing sizing for mitral valve annuloplasty is conventionally done intraoperatively using specific ‘sizer’ instruments, which are placed onto the valve tissue. This approach is barely reproducible since different sizing strategies have been established among surgeons. The goal of this study is to virtually apply different sizing methods on the basis of pre-repair echocardiography to find out basic differences between sizing strategies.MethodsIn three-dimensional echocardiographs of 43 patients, the mitral annulus and the contour of the anterior mitral leaflet were segmented using MITK Mitralyzer software. Similarly, three-dimensional virtual models of Carpentier-Edwards Physio II annuloplasty rings and their corresponding sizers were interactively generated from computer tomography images. For each patient, the matching annuloplasty ring was selected repeatedly according to popular sizing strategies, such as the height of anterior mitral leaflet, the intercommissural distance and the surface area of anterior mitral leaflet. The areas of the selected rings were considered as the neo-surface area of the mitral annulus after implantation.ResultsThe sizing of the mitral valve according to the height of anterior mitral leaflet (mean ring size = 29.9 ± 3.90), intercommissural distance (mean ring size = 37.5 ± 1.92) or surface area of anterior mitral leaflet (mean ring size = 32.7 ± 3.3) led to significantly different measurements (p ≤ 0.01). In contrary to intercommissural distance, height and surface area of the anterior mitral leaflet exhibited significant variations between the patients (p ≤ 0.01). The sizing according to the height of anterior mitral leaflet led to the maximal reduction of the mitral annulus surface area followed by the sizing according to the surface area of anterior mitral leaflet and finally by the intercommissural distance.ConclusionsThis novel comprehensive computer-based analysis reveals that the surveyed sizing methods led to the selection of significantly different annuloplasty rings and therefore underscore the ambiguity of routinely applied annuloplasty sizing strategies.

Technical aspects of mitral valve repair in Barlow's valve with prolapse of both leaflets: triangular resection for excess tissue, sophisticated chordal replacement, and their combination (the restoration technique).

Histological degeneration in Barlow's valve mainly starts in the rough zone, frequently expands toward the chordae, and advances to the clear zone, resulting in a saccular aneurysm-like morphology in the prolapsed region. On this basis, we have repaired the prolapsed segment by triangular resection, chordal replacement and the combination (the restoration technique). The aim of this study was to report our initial findings and evaluate the efficacy of our technique. Twelve patients diagnosed with Barlow's valve with prolapse of both leaflets (5 women; mean age, 49years) underwent the restoration technique between January 2008 and March 2013. We retrospectively reviewed short-term clinical outcomes. The mean duration of the clinical follow-up was 2.5±1.7years. The restoration technique was successfully performed in all patients. Predominant repair techniques were isolated triangular resection (anterior 8, posterior 9), a combination of triangular resection with chordal replacement (anterior 1, posterior 1), and isolated chordal replacement (anterior 3, posterior 1). All patients underwent complete mitral annuloplasty, and the mean ring size was 31±2mm. In-hospital mortality was not noted. Late transthoracic echocardiography showed no or trace mitral regurgitation without significant systolic anterior motion in all patients. The New York Heart Association functional class was significantly improved from 1.3±0.5 before surgery to 1.0±0.0 after it (p<0.01). There were no late thromboembolic or bleeding events. Initial experience with the restoration technique has provided excellent results without significant systolic anterior motion. Our technique may contribute to improve late results in Barlow's valve.

Free-standing silicene obtained by cooling from 2D liquid Si: structure and thermodynamic properties

The structure and various thermodynamic properties of free-standing silicene have been studied by computer simulation. Models are obtained by cooling from buckling two-dimensional (2D) liquid Si via molecular dynamics (MD) simulation with Stillinger–Weber interatomic potential. The temperature dependence of total energy, heat capacity, mean ring size and mean coordination number shows that silicenization of 2D liquid Si exhibits a first-order-like behavior. The evolution of radial distribution function upon cooling from the melt also shows that solidification occurs in the system. The final configuration of silicene is analyzed via coordination, bond-angle, interatomic distance and ring distributions or distribution of buckling in the system. 2D visualization of atomic configurations clearly demonstrated that silicene obtained ‘naturally’ by cooling from the melt exhibits various structural previously unreported behaviors. We find the formation of polycrystalline silicene with clear grain boundaries containing various defects including various vacancies, Stone–Wales defects or skew rings and multimembered rings unlike those proposed in the literature. However, atoms in the obtained silicene are mostly involved in six-fold rings, forming a buckling honeycomb structure like that found in practice. We find that buckling is not unique for all atoms in the models although the majority of atoms reveal buckling of the most stable low-buckling silicene found in the literature. The buckling distribution is broad and symmetric. Our comprehensive MD simulation of a relatively large silicene model containing 104 atoms and obtained ‘naturally’ by cooling from the melt provides original insights into the structure and thermodynamics of this important 2D material.

Cooling rate effects on structure of amorphous graphene

Simple monatomic amorphous 2D models with Honeycomb structure are obtained from 2D simple monatomic liquids with Honeycomb interaction potential (Rechtsman et al., Phys. Rev. Lett. 95, 228301 (2005)) via molecular dynamics (MD) simulations. Models are observed by cooling from the melt at various cooling rates. Temperature dependence of thermodynamic and structural properties including total energy, mean ring size, mean coordination number is studied in order to show evolution of structure and thermodynamics upon cooling from the melt. Structural properties of the amorphous Honeycomb structures are studied via radial distribution function (RDF), coordination number and ring distributions together with 2D visualization of the atomic configurations. Amorphous Honeycomb structures contain a large amount of structural defects including new ones which have not been previously reported yet. Cooling rate dependence of structural properties of the obtained amorphous Honeycomb structures is analyzed. Although amorphous graphene has been proposed theoretically and/or recently obtained by the experiments, our understanding of structural properties of the system is still poor. Therefore, our simulations highlight the situation and give deeper understanding of structure and thermodynamics of the glassy state of this novel 2D material.

Configurational entropy of hydrogen-disordered ice polymorphs.

The configurational entropy of several H-disordered ice polymorphs is calculated by means of a thermodynamic integration along a path between a totally H-disordered state and one fulfilling the Bernal-Fowler ice rules. A Monte Carlo procedure based on a simple energy model is used, so that the employed thermodynamic path drives the system from high temperatures to the low-temperature limit. This method turns out to be precise enough to give reliable values for the configurational entropy sth of different ice phases in the thermodynamic limit (number of molecules N → ∞). The precision of the method is checked for the ice model on a two-dimensional square lattice. Results for the configurational entropy are given for H-disordered arrangements on several polymorphs, including ices Ih, Ic, II, III, IV, V, VI, and XII. The highest and lowest entropy values correspond to ices VI and XII, respectively, with a difference of 3.3% between them. The dependence of the entropy on the ice structures has been rationalized by comparing it with structural parameters of the various polymorphs, such as the mean ring size. A particularly good correlation has been found between the configurational entropy and the connective constant derived from self-avoiding walks on the ice networks.

Predicting systolic anterior motion after mitral valve reconstruction: using intraoperative transoesophageal echocardiography to identify those at greatest risk

We set out to determine if intraoperative pre-bypass transoesophageal echocardiography could assist in predicting which patients are at greatest risk for systolic anterior motion (SAM) after mitral valve repair (MVR). Three hundred and seventy-five consecutive patients who underwent reconstructive MVR surgery for degenerative disease were included. Data were collected using intraoperative echocardiographic images taken prior to the initiation of cardiopulmonary bypass. Based on the physiology of SAM, we postulated that 11 parameters could be potential risk factors for SAM: left ventricular ejection fraction (LVEF), left ventricular end-systolic dimension, left ventricular end-diastolic dimension (LVEDD), basal septal diameter (basal-interventricular septal diameter in diastole (IVDd)), mid-ventricular septal diameter (mid-IVDd), coaptation-septal distance (c-sept), anterior leaflet height, posterior leaflet height, aorto-mitral angle, mitral annular diameter and left atrial diameter. These parameters were measured and recorded by a blinded single operator. Independent predictors of SAM were identified using multiple logistic regression analysis. Of the 375 patients, 345 (92%) did not develop SAM (No-SAM group), while 30 (8%) developed intraoperative or postoperative SAM (SAM group). The mean age was 56.8 ± 12.8 and 56.7 ± 13.8 in the No-SAM and SAM groups, respectively. The incidence of fibroelastic deficiency, forme fruste and Barlow's disease was similar in both groups. All patients received a complete annuloplasty ring as part of the repair. There was no statistical difference in the mean ring size used in each group. EF was similar in the No-SAM (56.2% ± 8.1) and SAM (57.0% ± 9.2) P = 0.63) groups. Independent predictors of developing SAM after valve repair were: EDD <45 mm [odds ratio (OR) 3.90; P = 0.028], aorto-mitral angle <120° (OR 2.74; P = 0.041), coaptation-septum distance <25 mm (OR 5.09; P = 0.003), posterior leaflet height >15 mm (OR 3.80; P = 0.012) and basal septal diameter ≥ 15 mm (OR 3.63; P = 0.039). The risk for SAM can be predicted using intraoperative transoesophageal echocardiography. The combination of a smaller left ventricle, tall posterior leaflet, narrow aorto-mitral angle and enlarged basal septum significantly increases the risk for SAM. Knowing these parameters prior to valve repair can assist the surgeon in adjusting their repair technique to minimize the risk.

Early outcomes of chordal reconstruction for posterior mitral leaflet prolapse

We retrospectively reviewed 16 patients (7 men and 9 women, aged 36 to 77 years) who underwent mitral valve repair with chordal reconstruction for isolated posterior mitral leaflet prolapse. Preoperative echocardiography demonstrated moderate mitral regurgitation in 1, and severe regurgitation in 15. We routinely used expanded polytetrafluoroethylene sutures as artificial chords, and ring annuloplasty was performed in all cases (mean ring size, 30 ± 2 mm). After implanting the ring, the length of the artificial chords was adjusted repeatedly using saline solution. Early postoperative echocardiography at 7.1 ± 1.1 days after surgery showed mitral regurgitation grades reduced to none or trivial in 15/16 patients. One required reoperation for recurrent mitral regurgitation 1.5 years after surgery. In the other patients, intermediate-term echocardiography at 9.1 ± 10.1 months after surgery demonstrated that residual mitral regurgitation was less than mild. We concluded that chordal reconstruction is an effective and highly reproducible procedure for the repair of isolated posterior mitral leaflet prolapse. Artificial chords for the posterior mitral leaflet should not be too long, to avoid systolic anterior motion or recurrent mitral regurgitation after surgery.

Butterfly Resection Is Safe and Avoids Systolic Anterior Motion in Posterior Leaflet Prolapse Repair

Quadrangular resection is a standard repair technique for prolapsing posterior leaflet; however, systolic anterior motion (SAM) sometimes occurs. Butterfly resection combines a triangular resection from the prolapsing edge and a reverse triangular resection to the annulus to remove redundancy, reduce leaflet height without annular plication, and minimize SAM. We assessed short-term and midterm outcomes and mitral leaflet configuration after repair vs quadrangular resection. Between 2002 and 2009, 53 patients underwent posterior leaflet resection with mitral annuloplasty, including quadrangular resection in 24 and butterfly resection in 29. The butterfly group had a significantly larger mean ring size (29.0 vs 27.8 mm, p = 0.04). SAM occurred in 2 patients in the quadrangular group and in none in the butterfly group. SAM completely resolved in 1 patient after inotropes were weaned, but the other needed a mitral valve replacement. Predischarge echocardiography showed the butterfly group had a significantly larger anterior leaflet/posterior leaflet ratio (3.05 vs 1.53, p < 0.01) and greater length from the coaptation point to the septum (2.91 vs 2.50 cm, p = 0.02) than the quadrangular group. Measurements at 3 months showed that the differences between the two groups persisted. During follow-up, no patients died or needed reoperation for recurrence. Moderate mitral regurgitation occurred in 1 in the quadrangular group. Butterfly resection can be safely performed without SAM and is durable in midterm follow-up. By echocardiography, this technique reduces the height of the posterior leaflet and shifts the coaptation point further away from the septum.

Outcomes Following Use of a Modified Duran Ring Tricuspid Valve Reconstruction Procedure for Secondary Tricuspid Regurgitation

Tricuspid valve (TV) repair using ring annuloplasty is reportedly to be superior to suture annuloplasty for treating tricuspid regurgitation (TR). The Duran ring TV annuloplasty technique was modified in order to reduce the risk of complete atrioventricular block and aortic valve injury and the outcomes are reported here. The modification involved not suturing half of the septal annulus. Between January 1998 and July 2007, 219 patients diagnosed with secondary TR underwent TV repair using a modified Duran ring procedure. The mean patient age was 54.2+/-12.7 years, and 65 (29.7%) patients were male. The median follow-up duration was 35.8 months (range, 0.03-122.6 months). The mean ring size was 27.4+/-2.0 mm. The prevalence of 3+ or 4+ regurgitation was 9.5% (21/218) at 1 week postoperatively, and 9.4% at more than 2 years postoperatively (mean, 57 months; 96 patients assessed). The in-hospital mortality rate was 1.4% (3/219). The overall survival rate was 95+/-1.5% at 1 year, 86.2+/-3.0% at 5 years, and 79.9+/-4.2% at 8 years. Multivariate analysis showed that atrial fibrillation at the last follow-up (P<0.001) and cardiopulmonary bypass time (P=0.016) were risk factors for recurrent or persistent significant TR. The modified Duran ring TV repair procedure for secondary TR patients was safe and durable. Notably, postoperative atrial fibrillation was found to be a significant risk factor for recurrent TR.

Visual field of high-pass resolution perimetry in normal subjects.

To investigate the properties of the visual field of high-pass resolution perimetry in normal subjects. Four centers collected normative data for high-pass resolution perimetry. In two of the centers the subjects were stratified by age. One eye was tested per subject using high-pass resolution perimetry (Ophthimus). We tested 640 normal subjects and describe their visual field results by test location. We also analyzed the data by concentric zone, age, and by testing center. The individual test location averages confirmed a reduction in resolution with eccentricity. Resolution thresholds increased with age by 0.025 dB per year (P < 0.001). The mean ring size increased by about 1 dB from age 20 to 70. Among centers there were significant differences in the means and the change in threshold with age (P = 0.009). The normal visual field of high-pass resolution perimetry is characterized by an increase in threshold with eccentricity. We found significant differences among the centers that were likely due to multiple factors including differences in subject selection criteria. Whether such differences occur with other perimetric techniques is unknown.

Polymer rings and chains consisting of doubly silyl-bridged metallocenes.

With the formation of novel organometallic macromolecules in mind, the polycondensation of transition metal ions and bridged cyclopentadienyl ligands was studied. To this end solvated salts MX2 (M = Fe, Ni, and Cr) were treated with a ligand that consisted of two doubly silyl-bridged cyclopentadienyl anions. For M = Fe and diluted solutions a series of rings Oi was obtained that consisted of a minimum of six (O6) and up to 17 (O17) ferrocene moieties in the backbone. They were separated partly by medium pressure liquid chromatography. The macrocycles were established by high-resolution MALDI-TOF mass spectroscopy which also yielded the molecular weight, the polydispersion, and the mean ring size, chi n, of the mixture of reaction products. When the reaction temperature was decreased from 25 degrees C to -20 degrees C, chi n increased from 8.1 to 10.8. Ferrocene-containing chains, lambda j, with 2 < or = j < or = 12 were obtained in addition to rings in the presence of water; the terminal groups were cyclopentadiene moieties. The reaction of two ferrocene-fused cyclopentadienyl anions with [FeCl2(thf)1.5] gave chains consisting of exclusively uneven numbers of ferrocenes. For M = Ni and Cr the formation of doubly silyl-bridged nickelocenes and chromocenes was proven by NMR spectroscopy. MALDI-TOF mass spectroscopy showed nickelocene-containing chains accompanied by some rings. For M = Fe the H,H-DQF COSY spectra established the structure of O7, O8, and O9. The oxidation of the ferrocene-containing ring O7 with I2, NOPF6, and AgPF6 gave ionic species [O7]n+ which suffered from low stability. The ring-closing reaction is discussed, and the relative abundance of the various rings is related to MNDO calculations.

Hypothetical graphite structures with negative gaussian curvature

We consider the geometries of hypothetical structures, derived from a graphite net by the inclusion of rings of seven or eight bonds, which may be periodic in three dimensions. Just as the positive curvature of fullerene sheets is produced by the presence of pentagons, so negative curvature appears with a mean ring size of more than six. These structures are based on coverings of periodic minimal surfaces, and surfaces parallel to these, which are known as exactly defined mathematical objects. In the same way that the cylindrical and conical structures can be generated (geometrically) by curving flat sheets so that the perimeter of a ring can be identified with a vector in the two-dimensional planar lattice, so these structures can be related to tessellations of the hyperbolic plane. The geometry of transformations at constant curvature relates various surfaces. Some of the proposed structures, which are reviewed here, promise to have lower energies than those of the convex fullerenes