In vitro study of percutaneous aortic valve replacement: selection of a tissue valve.

Background: Selection of the best tissue valve is an essential step before percutaneous aortic valve replacement (PAVR) becomes a clinical reality. The aim of this study was to evaluate in vitro three different tissue valves mounted within the same endovascular stent.

Methods: Thirty stented valves (10 aortic porcine, 10 pulmonary porcine, and 10 pericardial tubular) were sutured within a 32-mm long by 23-mm diameter cobalt-nickel stent.

Further information from a sonometric study of the normal tricuspid valve annulus in sheep: geometric changes during the cardiac cycle.

Background And Aim Of The Study: In a previous sono-metric study, changes were described that occurred in the normal tricuspid valve during the cardiac cycle. However, the wealth of data available suggested the need for reporting further findings that should contribute to a better understanding of the dynamics of the tricuspid valve.

Methods: Thirteen sonomicrometry transducers were placed in the hearts of each of seven sheep.

Mitral valve basal chordae: comparative anatomy and terminology.

Background: Recent awareness of the importance of the mitral valve's basal chordae stimulated a comparative anatomic study of these chordae in 11 human, 10 ovine, and 10 porcine hearts.

Methods: The basal chordae were defined as the chordae that arise from the papillary muscles and insert into the ventricular aspect of the leaflets.

Results: All leaflet insertions of the basal chordae were close to the annulus, except at the anterior mitral leaflet, where insertion was at the junction of the smooth and rough zones.

Dimensional ratios of normal mitral valve structures: a tool for determining the degree of geometric distortion in individual patients.

Background And Aim Of The Study: One objective of mitral valve repair is to restore the distorted mitral apparatus geometry to its normal dimensions specific for each patient. Because all dimensions of the normal aortic and mitral valves should be related, it was hypothesized that, in the presence of a normal aortic annulus, it would be possible to determine the dimensions of the structures needed for mitral valve repair.

Methods: In seven sheep, sonometric ultrasound crystals were implanted at the left and right trigones (T1, T2), lateral annulus (P1, P2), and the tips of the anterior and posterior papillary muscles (Ml, M2).

Coronary flow obstruction in percutaneous aortic valve replacement. An in vitro study.

Objective: Coronary flow obstruction is a serious complication reported in percutaneous aortic valve replacement. In an in vitro study of porcine hearts, the effects of valved stent implantation on coronary artery flow were studied with the native valve's leaflets intact and excised.

Methods: The right and left main coronary arteries of porcine hearts were dissected 20mm distal to the aortic root and directed into lengths of latex tubing leading to collection flasks.

The papillary muscles as shock absorbers of the mitral valve complex. An experimental study.

Objective: Although it is known that the papillary muscles ensure the continuity between the left ventricle (LV) and the mitral apparatus, their precise mechanism needs further study. We hypothesize that the papillary muscles function as shock absorbers to maintain a constant distance between their tips and the mitral annulus during the entire cardiac cycle.

Materials And Methods: Sonomicrometry crystals were implanted in five sheep in the mitral annulus at the trigones (T1 and T2), mid anterior annulus (AA) mid posterior annulus (PA), base of the posterior lateral scallops (P1 and P2), tips of papillary muscles (M1 and M2), and LV apex.

Sutureless stented aortic valve implantation under direct vision: lessons from a negative experience in sheep.

Background And Aim Of The Study: Percutaneous aortic valve replacement has been proposed as a valid alternative to surgery in selected cases; however, it still has many problems. As a less radical preliminary step, we implanted a balloon-expandable stented aortic valve under direct vision in sheep.

Methods: Under cardiopulmonary bypass (CPB) and through a transverse aortotomy, an aortic valve mounted in a long tubular balloon-expandable stent was implanted in six acute sheep.

Evidence of mitigated calcification of the Mosaic versus Hancock Standard valve xenograft in the mitral position of young sheep.

Objectives: Durability remains the main problem of all bioprosthetic valves, and calcification is the major cause of failure. New tissue treatment processes are expected to reduce mineralization. A comparative animal study was undertaken to evaluate the behavior of a new-generation porcine bioprosthesis in contrast with a first-generation porcine bioprosthesis.

Kinking of the atrioventricular plane during the cardiac cycle.

Systolic descent of the atrioventricular plane toward the relatively stationary left ventricular apex is well described. As the atrioventricular plane includes two separate valvular units, systolic atrioventricular plane displacement should not be homogenous. In 6 sheep, sonomicrometric crystals were implanted at the base of the right coronary sinus, anterolateral and posteromedial fibrous trigones, posterior mitral annulus, left ventricular apex, and the tips of the anterior and posterior mitral leaflets.

Functional terminology for the tricuspid valve.

Background And Aim Of The Study: Advances in echocardiography have awoken new interest in the tricuspid valve, which otherwise has been largely ignored by cardiologists and surgeons. These advances demand a precise terminology for the description of the tricuspid valve's different anatomic structures in health and disease. While simple nomenclatures have been developed for the mitral valve, no such system has been described for the tricuspid valve.

Progression of tricuspid regurgitation after repaired functional ischemic mitral regurgitation.

Background: Despite correction of left-sided cardiac lesions, associated functional tricuspid regurgitation (TR) that was surgically ignored can persist. It can also appear de novo. The aim of this study was to analyze TR in a group of patients who underwent successful revascularization and mitral valve repair (MVRep) for functional ischemic mitral regurgitation (MR).

Aortic root dynamics are asymmetric.

Background And Aim Of The Study: The presence of conformational changes in the aortic root during the cardiac cycle is well known, but precise information on time-related changes at each level of the root is lacking.

Methods: High-resolution, 3D sonomicrometry (200 Hz) was applied in an acute sheep model. Twelve crystals were implanted in eight sheep at each base (n = 3), commissure (n = 3), sinotubular junction (n = 3) and ascending aorta (n = 3).

Three-dimensional asymmetrical modeling of the mitral valve: a finite element study with dynamic boundaries.

Background And Aim Of The Study: Previous computational studies of the normal mitral valve have been limited because they assumed symmetrical modeling and artificial boundary conditions. The study aim was to model the mitral valve complex asymmetrically with three-dimensional (3-D) dynamic boundaries obtained from in-vivo experimental data.

Methods: Distance tracings between ultrasound crystals placed in the sheep mitral valve were converted into 3-D coordinates to reconstruct an initial asymmetric mitral model and subsequent dynamic boundary conditions.

Anterior mitral basal 'stay' chords are essential for left ventricular geometry and function.

Background And Aim Of The Study: Among the anterior mitral basal chords, two particularly strong and thick stay chords (SC) remain under tension during the entire cardiac cycle. Collagen fibers of the anterior mitral leaflet (AML) are oriented from insertion of the SC on the AML to the fibrous trigones (FT), suggesting that local stress is directed from the papillary muscles (PM) over the SC and AML to the FT, maintaining left ventricular (LV) geometry.

Methods: Sonomicrometry crystals were implanted in sheep at the LV apex (A), the anterior (AW) and septal (SW) LV wall, the PM tips (M1 and M2), the SC insertion into the AML (S1 and S2), the posterior (PMA) and lateral (P1 and P2) mitral annulus, the FT (T1 and T2), the tips of the anterior (AL) and posterior (PL) mitral leaflets, and the base of the aortic right coronary sinus (RCS).

Left ventricular endocardial longitudinal and transverse changes during isovolumic contraction and relaxation: a challenge.

Left ventricular (LV) longitudinal and transverse geometric changes during isovolumic contraction and relaxation are still controversial. This confusion is compounded by traditional definitions of these phases of the cardiac cycle. High-resolution sonomicrometry studies might clarify these issues.

External aortic annuloplasty ring for valve-sparing procedures.

Two different surgical approaches have been suggested for aortic valve-sparing surgery. My colleagues and I suggest combining the advantages of both approaches by adding an external subvalvular prosthetic ring annuloplasty to the remodeling procedure.

Flat or curved pericardial aortic valve cusps: a finite element study.

Background And Aim Of The Study: The finite element method (FEM) has frequently been used to investigate the behavior of the aortic valve, but studies on the performance and behavior of free-hand autologous pericardial aortic valves reconstructed using specially designed valve molds have not been performed. The study aim was to demonstrate the effectiveness of a three-dimensional (3-D) cusp of the authors' design (H-Mold) versus a two-dimensional (2-D) (flat) cusp using a FEM to compare stress distribution and leaflet contact properties.

Methods: Solid models of the aortic root and valve cusps were constructed using a computer-aided design package.

Mechanism of recurrent ischemic mitral regurgitation after annuloplasty: continued LV remodeling as a moving target.

Background: Patients who undergo ring annuloplasty for ischemic mitral regurgitation (MR) often have persistent or recurrent MR. This may relate to persistent leaflet tethering from left ventricle (LV) dilatation that is not relieved by ring annuloplasty. Therefore, the purpose of this study was to test the hypothesis that recurrent MR in patients after ring annuloplasty relates to continued LV remodeling.

Halofuginone inhibits serum-stimulated pericardial tissue retraction in vitro.

We developed an in vitro model of tissue contraction in which living pericardium, in response to serum, contracted and the cells in situ expressed proliferating cell nuclear antigen (PCNA) and synthesized collagen. Here we evaluated the effects of halofuginone on these serum-stimulated pericardial tissue responses. Parietal pericardium was incubated with media containing increasing doses of halofuginone and evaluated for tissue contraction, evident by tissue curling.

Sonometric study of the normal tricuspid valve annulus in sheep.

Background And Aim Of The Study: Mitral valve dynamic changes during the cardiac cycle have been previously studied in sheep using sonomicrometry. The study aim was to analyze geometric changes of the normal tricuspid annulus in sheep using a similar methodology. This is most likely the first tricuspid valve study using high temporal resolution (200 Hz = 200 data points per second).