Mitral valve opening in the ovine heart

Karlsson, Matts; Glasson, Julie R.; Bolger, Ann F.; Daughters, George T.; Komeda, Masashi; Foppiano, Linda E.; Miller, D. Craig; Ingels, Neil B.; Tye, Terrence

doi:10.1152/ajpheart.1998.274.2.h552

Cited by 39 publications

(39 citation statements)

References 25 publications

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“…It is difficult to differentiate whether delayed valve closure observed in our experiment was due to delayed annular reduction versus altered anterior leaflet motion, but total angular anterior leaflet excursion was not affected by phenol. The baseline shape of the anterior mitral leaflet during valve closure assumed a complex sigmoid curve, as reported previously (9). After phenol ablation, the anterior leaflet became entirely concave to the atrium during valve closure in contrast to the canine experiments of Curtis and Priola (4), who observed greater deflection of the anterior leaflet toward the atrium after phenol application.…”

Section: Discussionsupporting

confidence: 67%

Ablation of mitral annular and leaflet muscle: effects on annular and leaflet dynamics

Timek¹,

Lai²,

Dagum³

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

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Miller, and Neil B. Ingels, Jr. Ablation of mitral annular and leaflet muscle: effects on annular and leaflet dynamics. Am J Physiol Heart Circ Physiol 285: H1668-H1674, 2003 10.1152/ajpheart.00179.2003 and leaflet three-dimensional (3-D) dynamics were examined after circumferential phenol ablation of the MA and anterior mitral leaflet (AML) muscle. Radiopaque markers were sutured to the left ventricle, MA, and both mitral leaflets in 18 sheep. In 10 sheep, phenol was applied circumferentially to the atrial surface of the mitral annulus and the hinge region of the AML, whereas 8 sheep served as controls. Animals were studied with biplane video fluoroscopy for computation of 3-D mitral annular area (MAA) and leaflet shape. MAA contraction (MAACont) was determined from maximum to minimum value. Presystolic MAA (PSMAACont) reduction was calculated as the percentage of total reduction occurring before end diastole. Phenol ablation decreased PS-MAACont (72 Ϯ 6 vs. 47 Ϯ 31%, P ϭ 0.04) and delayed valve closure (31 Ϯ 11 vs. 57 Ϯ 25 ms, P ϭ 0.017). In control, the AML had a compound sigmoid shape; after phenol, this shape was entirely concave to the atrium during valve closure. These data indicate that myocardial fibers on the atrial side of the valve influence the 3-D dynamic geometry and shape of the MA and AML.anterior mitral leaflet; three-dimensional; end systole; end diastole TIMELY AND EFFECTIVE valve closure requires precise temporal and spatial coordination of the mitral leaflets, mitral annulus, and the subvalvular apparatus. The mitral annulus in humans (1) and other mammals (22) is a discontinuous fibrous ring with a variable insertion of atrial and ventricular myocardial fibers. Experimental (17,21) and clinical (13, 16) studies have shown that the mitral annulus has a "sphincteric" function during valve closure facilitating leaflet coaptation by reducing mitral valve area. Our previous experiments in ovine hearts revealed that 89% of annular reduction occurred before ventricular systole (7) and was abolished by ventricular pacing. Subsequently, mitral annular area change was shown to be closely linked with atrial dynamics during rapid pacing (18) and acute ischemia (19). These and other studies (16, 21) suggest an atrial influence on presystolic mitral annular dynamics. Anatomically, atrial myocardial fibers have been shown to insert on the annular portion of the anterior mitral leaflet in humans (2) and experimental animals (6, 22). Furthermore, these fibers have been demonstrated to have intrinsic contractile properties (6, 15) and dense neural innervation (10), suggesting a neuromuscular role in annular and leaflet dynamics, the significance of which is yet to be defined. Although intrinsic annular and leaflet contractile activity may play an important role in normal valve physiology, the in vivo function of these mitral complex components is not understood.Using miniature radiopaque marker technology, we studied mitral annular and leaflet dynamics after phenol ablation of mitral annular and anterior le...

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Section: Discussionsupporting

confidence: 67%

Ablation of mitral annular and leaflet muscle: effects on annular and leaflet dynamics

Timek¹,

Lai²,

Dagum³

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

Self Cite

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“…It is important to note, however, that the time of maximum RA volume does not necessarily correspond to the time of tricuspid valve opening. On the left side of the heart, Karlsson et al (21), using myocardial markers on the mitral valve, demonstrated that the mitral valve moves toward its open position in the isovolumic phase but that the leaflets do not separate until minimum left ventricular pressure is obtained. A similar phenomenon could occur on the right side of the heart with the tricuspid valve, and the RA appendage also may play a role.…”

Section: Discussionmentioning

confidence: 99%

Reservoir and conduit function of right atrium: impact on right ventricular filling and cardiac output

Gaynor¹,

Maniar²,

Prasad³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

118

106

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The purpose of this study was to investigate the relationship between right atrial (RA) reservoir and conduit function and to determine how hemodynamic changes influence this relationship and its impact on cardiac output. In 11 open-chest sheep, RA reservoir and conduit function were quantified as RA inflow with the tricuspid valve closed versus open, respectively. Conduit function was separated into early (before A wave) and late (after A wave) components. The effects of inotropic stimulation, partial pulmonary artery occlusion, and pericardiotomy were tested. At baseline with the pericardium intact, reservoir function accounted for 0.56 (SD 0.13) of RA inflow, early conduit for 0.29 (SD 0.07), and late conduit (during RA contraction) for 0.16 (SD 0.11). Inotropic stimulation decreased conduit function and increased reservoir function, but these effects did not reach statistical significance. With partial pulmonary artery occlusion, early conduit function fell to 0.20 (SD 0.11) (P Ͻ 0.04), and the conduit-to-reservoir ratio decreased by 41% (P Ͻ 0.03). Similarly, after pericardiotomy, early conduit function fell to 0.14 (SD 0.09) (P Ͻ 0.004), reservoir function increased to 0.72 (SD 0.08) (P Ͻ 0.04), and, consequently, the early conduit-to-reservoir ratio decreased by 63% (P Ͻ 0.006). Cardiac output was inversely related to the conduit-to-reservoir ratio (r ϭ 0.39, P Ͻ 0.001). This study demonstrated that the right atrium adjusts its ability to act more as a reservoir than a conduit in a dynamic manner. The RA conduit-to-reservoir ratio was directly related to the right ventricular pressure-RA pressure gradient at the time of maximum RA volume, with increased ventricular pressures favoring conduit function, but it was inversely related to cardiac output, with an increase in the reservoir contribution favoring improved cardiac output. right atrial function; conductance catheter; right ventricular afterload; inotropic stimulation; pulmonary artery occlusion THE RIGHT ATRIUM is a dynamic structure whose role is to assist filling of the right ventricle. Ideally, the right atrium should transfer a high volume of blood rapidly to the ventricle at low pressure to prevent peripheral edema and hepatic congestion. The three components of atrial function are 1) reservoir function, storing blood when the tricuspid valve is closed and releasing stored blood when it opens; 2) conduit function, passive blood transfer directly from the coronary and systemic veins to the right ventricle when the tricuspid valve is open; and 3) booster pump function, atrial contraction in late diastole to complete ventricular filling (10,13,31). Previous studies have demonstrated that pathologically altered left atrial conduit-to-reservoir function is an important determinant of left heart function and can profoundly affect cardiac performance (2, 4, 14 -17, 30, 33, 34, 38), but studies examining right atrial (RA) reservoir and conduit function are limited.The mechanics of the right atrium are complex (5,8,24,26). In 1628, William Harvey was the...

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“…In addition to closing later and over a longer period, the xenograft leaflets were convex toward the atrium during closure, whereas the native mitral leaflets are concave toward the atrium. 26 The natural "sigmoid" or concave shape of the native leaflets is probably maintained by tension on the second-order chordae tendineae, which are inserted on the mid-portion of the leaflet at the junction of the rough and smooth zones. 26 If that mechanistic hypothesis is operant, it would suggest that inadequate tension on the secondorder chordae tendineae of the xenograft valve may explain the convex shape of the leaflets.…”

Section: Discussionmentioning

confidence: 99%

Functional Evaluation of the Medtronic Stentless Porcine Xenograft Mitral Valve in Sheep

Dagum

Green²,

Timek³

et al. 1999

Circulation

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Background-Recently, renewed interest in allograft and stentless "freehand" bileaflet xenograft mitral valve replacement has arisen. The variability of human papillary tip anatomy and scarcity of donors limit allograft availability, making xenograft mitral valves an attractive alternative; however, these valves require new surgical implantation techniques, and assessment of their hemodynamics and functional geometry is lacking. Methods-Seven

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Mitral valve opening in the ovine heart

Cited by 39 publications

References 25 publications

Ablation of mitral annular and leaflet muscle: effects on annular and leaflet dynamics

Ablation of mitral annular and leaflet muscle: effects on annular and leaflet dynamics

Reservoir and conduit function of right atrium: impact on right ventricular filling and cardiac output

Functional Evaluation of the Medtronic Stentless Porcine Xenograft Mitral Valve in Sheep

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