Tachycardia-induced cardiomyopathy in the ovine heart: mitral annular dynamic three-dimensional geometry.
BACKGROUND
Ring annuloplasty has been used to correct annular dilatation and mitral regurgitation in dilated cardiomyopathy, but little is known about the dynamic precise 3-dimensional geometry of the mitral annulus in this condition.


METHODS
Nine sheep had radiopaque markers sewn to the mitral annulus, creating 8 distinct segments beginning at the posterior commissure (segments 1-4, septal mitral annulus; segments 5-8, lateral mitral annulus). Biplane videofluoroscopy and transesophageal echocardiography were performed before and after rapid pacing (180-230 min(-1) for 15 +/- 6 days) sufficient to develop tachycardia-induced cardiomyopathy and mitral regurgitation. Mitral annular segment contraction was defined as the percentage difference between maximum and minimum lengths. Mitral annular area and mitral annular septal-lateral and commissure-commissure diameters and 3-dimensional shape were determined from marker coordinates.


RESULTS
With tachycardia-induced cardiomyopathy, end-diastolic mitral annular area, septal-lateral diameter, and commissure-commissure diameter increased by 36% +/- 14%, 25% +/- 12%, and 9% +/- 5%, respectively (P <.01), whereas mitral regurgitation increased from 0.3 +/- 0.2 to 2.2 +/- 0.9 (P <.0001). All annular segments dilated at end-diastole with tachycardia-induced cardiomyopathy, except the segment between the midseptal annulus and the left fibrous trigone. Annular segment contraction was significantly decreased with tachycardia-induced cardiomyopathy in the lateral, but not in the septal, regions. Three-dimensional reconstruction of annular shape revealed a saddle shape of the annulus at baseline; this shape was also measured with tachycardia-induced cardiomyopathy, but there was some flattening of the septal annulus.


CONCLUSIONS
With tachycardia-induced cardiomyopathy, the mitral annulus dilated substantially, being more in the septal-lateral than in the commissure-commissure dimension. Greater annular segmental dilatation and decreased contraction occurred in the lateral annulus. The saddle shape of the annulus was retained but flattened.
Timek
Tomasz A
TA
Department of Cardiothoracic Surgery, Stanford University School of Medicine, CA 94305-5247, USA.
Dagum
Paul
P
Lai
David T
DT
Liang
David
D
Daughters
George T
GT
Tibayan
Frederick
F
Ingels
Neil B
NB
Miller
D Craig
DC
D000818:Animals; D002304:Cardiac Pacing, Artificial; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D019560:Echocardiography, Three-Dimensional / Q000295:instrumentation / Q000379:methods; D005471:Fluoroscopy; D006439:Hemodynamics; D008943:Mitral Valve / Q000000981:diagnostic imaging* / Q000473:pathology; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D012756:Sheep; D013610:Tachycardia / Q000150:complications*; D014741:Video Recording