Impact of prosthetic mitral rings on aortomitral apparatus function: a cardiac magnetic resonance imaging study

BACKGROUND: The circumference of the aortic annulus adjusts proportionally with changes in left ventricular volume. These dimensional changes in the aortic annulus improve the left ventricular outflow tract (LVOT) hemodynamics and enhance the anterior mitral valve leaflet (AML) movement. In this study, we investigated the impact of circumferential and partial circumference prosthetic mitral rings on aortomitral apparatus function. METHODS: Forty patients who underwent coronary artery bypass graft surgery and restrictive annuloplasty of the mitral valve annulus through either a partial circumference flexible ring (group A = 20 patients) or a circumferential rigid ring (group B = 20 patients) were evaluated using cardiac magnetic resonance imaging. Imaging was performed at the end of a 2-year follow-up period. Variations in LVOT diameter, transmitral valve gradient, and effective mitral valve area were measured and compared. RESULTS: Mean variation in LVOT diameter was significantly higher in group A compared with group B (12.7% +/- 4% versus 3.6% +/- 5%, p = 0.0005). Transmitral valve gradient was higher in group B than in group A (6.2 +/- 3 mm Hg versus 4.6 +/- 2 mm Hg, p = 0.007), whereas effective mitral valve area was larger in group A than group B (3.9 +/- 4 cm(2) versus 3.1 +/- 6 cm(2), p = 0.009). The long-axis cardiac magnetic resonance imaging of patients in group B demonstrated that movement at the base of the AML was hindered with the AML pivotal point appearing to shift posteriorly. CONCLUSIONS: This study demonstrated that the use of circumferential annular rings significantly impairs overall aortomitral apparatus function by reducing outflow diameter and AML movement.