Mitral Annular Dilatation and Papillary Muscle Dislocation Without Mitral Regurgitation in Sheep

Green, G. Randall; Dagum, Paul; Glasson, Julie R.; Daughters, George T.; Bolger, Ann F.; Foppiano, Linda E.; Berry, Gerald J.; Ingels, Neil B.; Miller, D. Craig

doi:10.1161/01.cir.100.suppl_2.ii-95

Cited by 27 publications

(24 citation statements)

References 32 publications

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“…It is also noteworthy that the delay in valve closure reported in the current experiment is similar to that described with ventricular pacing (17). A previous study (8) from this laboratory after phenol ablation of only the anterior mitral leaflet musculature also did not reveal any increase in mitral regurgitation. The commissure-commissure annular diameter dilated in that experiment but did not do so in the current study.…”

Section: Discussionmentioning

confidence: 49%

“…After completion of marker placement, the control group animals (n ϭ 8) underwent no further treatment, whereas the phenol group (n ϭ 10) had a 95% phenol solution (Sigma Chemical; St. Louis, MO), a histotoxic chemical, applied (as described previously in Ref. 8) for 2 min on the atrial side of the hinge region of the anterior mitral leaflet and septal annulus and for 5 min on the atrial side of the remaining portions of the annulus. Longer application time was chosen for the lateral annulus because it is known to have a higher myocardial fiber content than the more fibrous septal annulus (2).…”

Section: Surgical Preparationmentioning

confidence: 99%

See 1 more Smart Citation

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: Discussionmentioning

confidence: 49%

Section: Surgical Preparationmentioning

confidence: 99%

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

View full text Add to dashboard Cite

show abstract

“…19,20 On the other hand, whereas isolated commissure-commissure annular dilation is apparently not sufficient to cause IMR, 21 it may stretch the leaflets over a larger area thereby limiting the available leaflet surface for coaptation. 22 Normal annular dynamics play a role in both LV filling and ejection.…”

Section: Discussionmentioning

confidence: 99%

Paneth Suture Annuloplasty Abolishes Acute Ischemic Mitral Regurgitation but Preserves Annular and Leaflet Dynamics

Tibayan

Rodriguez²,

Liang³

et al. 2003

Circulation

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Background-Ring annuloplasty, the standard treatment for ischemic mitral regurgitation (IMR), abolishes normal annular dynamics and freezes the posterior leaflet. We examined the impact of Paneth suture annuloplasty during acute IMR on motion of the mitral annulus and leaflets in an ovine model. Methods and Results-Eight sheep had radiopaque markers placed on the left ventricle, anterior mitral leaflet, posterior mitral leaflet, and mitral annulus. A Paneth suture annuloplasty that could be reversibly tightened was anchored to each fibrous trigone and externalized through the mid-lateral mitral annulus. Acute IMR was induced by proximal circumflex artery occlusion. Transesophageal echocardiography assessed the degree of IMR, and biplane cinefluoroscopy measured 3-dimensional marker coordinates before and during circumflex ischemia, and tightening of the Paneth suture. Paneth suture annuloplasty eliminated acute IMR, and reduced septal-lateral and commissure-commissure mitral annular dimensions. Tightening of the annuloplasty sutures, even beyond the degree necessary to eliminate mitral regurgitation (MR), did not reduce septal-lateral or commissure-commissure annular shortening, shortening of the muscular annular perimeter, annular flexion, or angular excursion of the anterior or posterior leaflets relative to ischemic conditions. Conclusions-In contrast to ring annuloplasty, annular reduction sufficient to restore mitral competence during acute IMR can be achieved with a Paneth suture annuloplasty while simultaneously maintaining normal annular and leaflet dynamic motion. These findings should prompt additional investigation and design of repair methods that preserve the mobility of the mitral apparatus.

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“…Septal-lateral diameter is often implicated in leaflet malcoaptation in acute ischemic MR and functional MR or CIMR, 12,13 whereas the mechanistic importance of commissure-to-commissure annular dilatation has been debated. 14 Green et al used topical phenol to create mitral annular dilation in the commissure-commissure (but not septal-lateral) direction without MR. Commissurecommissure annular dilatation was similar in the CIMR(ϩ) and CIMR(Ϫ) animals, suggesting that remodeling in this dimension is not sufficient to produce functional MR. These increases in annular dimensions require the mitral leaflets to cover more area, exhausting the normal excess "reserve" of leaflet tissue, which is additionally compounded by less effective leaflet closure because of apical tethering or tenting of the leaflets.…”

Section: Annular Geometrymentioning

confidence: 99%

Geometric Distortions of the Mitral Valvular-Ventricular Complex in Chronic Ischemic Mitral Regurgitation

et al. 2003

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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). After 8 days, cinefluoroscopy provided 3-dimensional marker data, and snare occlusion of obtuse marginal branches created inferior myocardial infarction, including the posterior papillary muscle. After 7 weeks, the 16 surviving animals were studied again and grouped by mitral regurgitation grade (≥ 2+, n=10 versus ≤ 1+, n=6). End-systolic mitral annulus dimensions, components of papillary muscle and leaflet displacement, were calculated. After inferior myocardial infarction, total displacement of the posterior papillary muscle from the midseptal annulus (“saddle horn”) was greater in CIMR(+) animals: 6.5±3.2 versus 3.1±2.7 ( P =0.02), with the posterior papillary muscle moving more laterally (6.8±3.4 versus 2.5±3.5 mm, P =0.01). Increase in mitral annular septal-lateral diameter was greater in animals with CIMR (4.9±2.7 versus 2.3±2.0, P =0.02), and apical displacement of the posterior leaflet (PL) margin was also greater in the CIMR(+) group (1.7±1.0 versus 0.3±0.5, P =0.01). Conclusions— The CIMR(+) group had greater septal-lateral annular dilatation, lateral posterior papillary muscle displacement, and apical PL restriction, indicating that these associated geometric alterations may be important in the pathogenesis of CIMR. Treatment of CIMR should address both annular septal-lateral dilatation and lateral displacement of the posterior papillary muscle.

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Mitral Annular Dilatation and Papillary Muscle Dislocation Without Mitral Regurgitation in Sheep

Cited by 27 publications

References 32 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

Paneth Suture Annuloplasty Abolishes Acute Ischemic Mitral Regurgitation but Preserves Annular and Leaflet Dynamics

Geometric Distortions of the Mitral Valvular-Ventricular Complex in Chronic Ischemic Mitral Regurgitation

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