Variations in annuloplasty ring and sizer dimensions may alter outcome in mitral valve repair

Sizing the mitral annulus remains one of the more subjective areas of annuloplasty surgery. We compared the dimensions of annuloplasty rings to annuloplasty sizers and to human mitral valve annuli to determine whether any discrepancies exist that might impact repair results.

The anterior and posterior length of rigid rings, flexible rings, and corresponding sizers were measured. The ratio of the anterior length to the total length was calculated (A/T ratio) and compared to normal human ratios.

Nearly all rings had A/T ratios between 30% and 35% (except for the 32-mm rigid ring at 37.5%). For both rigid and flexible rings, the ring A/T ratios and the sizer A/T ratios differed significantly (except for the 28-mm rigid ring and sizer). In comparison to the average human A/T ratio (36.6%), the ratio for most rings was significantly lower.

The mismatch between rings and sizers results in three possible scenarios: the length of the anterior portion of the ring can be equal to, smaller than, or larger than the anterior portion of the sizer. The clinical implications are that the valve could become stenotic when the ring is implanted or that the anterior portion of the annulus could be altered (stretched or buckled). We feel that to assure improved long-term results, more accurate matching of sizers to rings is essential and that better matching to normal human anatomical ratios would be ideal.