Alterations in lateral left ventricular wall transmural strains during acute circumflex and anterior descending coronary occlusion.

Background: Increased circumferential-radial shear in the midlateral left ventricle adjacent to ischemic myocardium has been observed during acute midcircumflex ischemia in open-chest animals. Extending this work, we studied transmural strains in closed-chest animals during acute proximal-circumflex (pCX) and proximal-left anterior descending (pLAD) occlusions.

Methods: Six sheep had radiopaque markers implanted to silhouette the left ventricle and measure regional systolic fractional area shortening; three transmural bead columns were inserted into the midlateral wall for transmural myocardial strain analysis.

Tenting volume: three-dimensional assessment of geometric perturbations in functional mitral regurgitation and implications for surgical repair.

Background And Aim Of The Study: Functional mitral regurgitation (FMR) often complicates dilated cardiomyopathy (DCM), and portends a poor prognosis. Debate over the optimal treatment continues, underscoring the present incomplete understanding of the patho-anatomic mechanisms of this disease. Studies of mitral tenting volume and tenting area, and echocardiographic measures of abnormal apical systolic leaflet geometry have linked mitral leaflet deformation with subvalvular left ventricular (LV) remodeling in chronic ischemic MR.

Posterior mitral leaflet extension: an adjunctive repair option for ischemic mitral regurgitation?

Background: Residual or recurrent mitral regurgitation frequently occurs after mitral valve repair for ischemic mitral regurgitation with an annuloplasty ring. Because annuloplasty primarily addresses annular dilatation, we studied an adjunctive technique that might correct restricted leaflet (Carpentier type IIIb) systolic closing motion, which often accompanies annular dilatation in patients with ischemic mitral regurgitation.

Methods: Six sheep had radiopaque markers placed on the left ventricle, mitral leaflets and annulus, and mitral subvalvular apparatus.

Effect of cutting second-order chordae on in-vivo anterior mitral leaflet compound curvature.

Background And Aim Of The Study: Leaflet curvature determines leaflet stress. In order to assess the influence of second-order chordae (2 degrees CT) on anterior mitral valve leaflet (AMVL) geometry, AMVL curvature was measured before (Baseline) and after (CUT) cutting the 2 degrees CT.

Methods: Miniature radiopaque markers were sutured onto the AMVL in eight sheep: four along the central-meridian from mid-septal annulus to the free-margin; and one each at the 2 degrees CT insertion.

Subvalvular repair: the key to repairing ischemic mitral regurgitation?

Background: Residual or recurrent mitral regurgitation frequently occurs after mitral ring annuloplasty repair for ischemic mitral regurgitation (IMR), because annuloplasty primarily addresses annular dilatation. We describe a subvalvular repair technique addressing posterior papillary muscle (PPM) displacement.

Methods And Results: Ten sheep had radiopaque markers placed on the left ventricle (LV) and mitral apparatus.

Altered mitral valve kinematics with atrioventricular and ventricular pacing.

Background And Aim Of The Study: Pacing-induced mitral regurgitation contributes to the 'pacemaker syndrome', which usually is observed with ventricular (V) pacing, but has also been reported with atrioventricular (AV) sequential pacing. Effects of different pacing modes on 3-D kinematics of the mitral apparatus are incompletely understood.

Methods: Radio-opaque markers were placed on the left ventricular (LV) and mitral apparatus including the annulus, leaflets and papillary muscles of eight sheep.

Annular or subvalvular approach to chronic ischemic mitral regurgitation?

Objective: We sought to investigate whether annular or subvalvular interventions corrected chronic ischemic mitral regurgitation differently.

Methods: Sheep underwent placement of markers on the left ventricle, mitral annulus, papillary muscles (anterior and posterior), and both leaflet edges. A transannular suture (septal-lateral annular cinching) was anchored to the midseptal mitral annulus and externalized through the midlateral mitral annulus.

Increases in mitral leaflet radii of curvature with chronic ischemic mitral regurgitation.

Background And Aim Of The Study: Leaflet curvature is a primary determinant of leaflet stress, but no quantitative in-vivo leaflet curvature data exist. Chronic ischemic mitral regurgitation (CIMR) is associated with remodeling of the valvular-ventricular complex. It was hypothesized that leaflet radii of curvature (ROC) would change with such remodeling.

Importance of mitral valve second-order chordae for left ventricular geometry, wall thickening mechanics, and global systolic function.

Background: Mitral valvular-ventricular continuity is important for left ventricular (LV) systolic function, but the specific contributions of the anterior leaflet second-order "strut" chordae are unknown.

Methods And Results: Eight sheep had radiopaque markers implanted to silhouette the LV, annulus, and papillary muscles (PMs); 3 transmural bead columns were inserted into the mid-lateral wall between the PMs. The strut chordae were encircled with exteriorized wire snares.

Alterations in left ventricular torsion and diastolic recoil after myocardial infarction with and without chronic ischemic mitral regurgitation.

Background: Chronic ischemic mitral regurgitation (CIMR) is associated with heart failure that continues unabated whether the valve is repaired, replaced, or ignored. Altered left ventricular (LV) torsion dynamics, with deleterious effects on transmural gradients of oxygen consumption and diastolic filling, may play a role in the cycle of the failing myocardium. We hypothesized that LV dilatation and perturbations in torsion would be greater in animals in which CIMR developed after inferior myocardial infarction (MI) than in those that it did not.

Cutting second-order chords does not prevent acute ischemic mitral regurgitation.

Background: Cutting anterior mitral leaflet second-order chordae has been proposed for repair in ischemic mitral regurgitation (IMR). We examined the efficacy of such chordal cutting in preventing acute IMR.

Methods And Results: Six sheep underwent radiopaque marker placement (left ventricle, mitral annulus, papillary muscles [PMs], and leaflets).

Does septal-lateral annular cinching work for chronic ischemic mitral regurgitation?

Objectives: Ring annuloplasty, the current treatment of choice for chronic ischemic mitral regurgitation, abolishes dynamic annular motion and immobilizes the posterior leaflet. In a model of chronic ischemic mitral regurgitation, we tested septal-lateral annular cinching aimed at maintaining normal annular and leaflet dynamics.

Methods: Twenty-five sheep had radiopaque markers placed on the mitral annulus and anterior and posterior mitral leaflets.

Annular remodeling in chronic ischemic mitral regurgitation: ring selection implications.

Background: More precise understanding of annular remodeling in the evolution of chronic ischemic mitral regurgitation is needed to provide a more rational basis for optimal annuloplasty ring sizing and selection as well as the design of new reparative techniques. Three-dimensional in vivo data describing these geometric perturbations however are lacking. Using an ovine model of chronic myocardial infarction we determined the three-dimensional distortions of the mitral annulus associated with the development of chronic ischemic mitral regurgitation.

Geometric distortions of the mitral valvular-ventricular complex in chronic ischemic mitral regurgitation.

Background: Better understanding of the precise 3-dimensional geometric changes of the mitral valvular-ventricular complex in chronic ischemic mitral regurgitation (CIMR) is needed in order to devise better surgical repair techniques. We hypothesized that changes after inferior myocardial infarction would be different in hearts that developed CIMR compared with those that did not.

Methods And Results: Twenty-four sheep underwent coronary snare and marker placement (annulus, papillary muscles, and anterior and posterior leaflets).

Alterations in left ventricular curvature and principal strains in dilated cardiomyopathy with functional mitral regurgitation.

Background And Aim Of The Study: Functional mitral regurgitation (FMR) is increasingly recognized as a left ventricular (LV) disease. Dilated cardiomyopathy (DCM) is commonly accompanied by FMR and reduction of LV torsion. Therapeutic targets for DCM include LV size reduction, altered LV shape, elimination of MR, and increasing LV torsion.

Ischemia in three left ventricular regions: Insights into the pathogenesis of acute ischemic mitral regurgitation.

Background: Acute posterolateral left ventricular ischemia in sheep results in ischemic mitral regurgitation, but the effects of ischemia in other left ventricular regions on ischemic mitral regurgitation is unknown.

Methods: Six adult sheep had radiopaque markers placed on the left ventricle, mitral annulus, and anterior and posterior mitral leaflets at the valve center and near the anterior and posterior commissures. After 6 to 8 days, animals were studied with biplane videofluoroscopy and transesophageal echocardiography before and during sequential balloon occlusion of the left anterior descending, distal left circumflex, and proximal left circumflex coronary arteries.