Small aortic annulus: a functional definition.

BACKGROUND & OBJECTIVE: Small aortic annulus is conventionally associated with poor outcome after aortic valve replacement (AVR). Contrarily, several patients have excellent follow-up results after AVR with 19, 20 or 21 size Medtronic Hall (MH) or Sorin Carbocast (SC) prostheses. This disparity prompted a relook at the semantics of a small aortic annulus.

METHODS

Available survivors of isolated AVR with #19, #20 or #21 prostheses - 13 with 19 SC or 20 MH valves (Group A) and 29 with 21 SC or MH valves (Group B) were studied. Disparity between actually implanted prostheses versus predicted prosthetic size (tissue annulus diameter) was analysed according to nomograms of Rowlatt et al, NIH Plehn, Kishimoto formula and Sievers composite criteria. Preoperative and follow-up echocardiographic assessments were used for hemodynamic and prosthetic function indices.

RESULTS

Both groups were similar in age, height, weight, BSA, BMI, mean NYHA class, CTR, preoperative peak gradient (PG) (92. 0 +/- 29.55 vs 102.88 +/- 33.65), mean gradient (MG) (56.8 +/- 24.6 vs 61.55 +/- 16.56), LVEDD (50.75 +/- 10.92 vs 56.0 +/- 13.5), LVESD (34.37 +/- 13.32 vs 38.52 +/- 13.85) and LVEF (67.5 +/- 12.5 vs 63.9 +/- 14.3). By developmental indices of Rowlatt et al. and NIH, no valve annulus could be designated as narrow. By Sievers composite nomogram all implanted valves were undersized by echocardiographic parameters, in normal range by angiographic criteria and oversized by anatomic autopsy data. Implanted valves in both groups were bigger than Plehn-predicted size (18.16 +/- 1.48 in GrA, 19.46 +/- 1. 10 in GrB). Valve size indices (VSI) (GrA 16.16 +/- 2.85 GrB 14.24 +/- 1.64) and geometric orifice area indices (VAI: valve area index) (GrA 1.50 +/- 0.28 vs 1.41 +/- 0.19) and postoperative rest PG (GrA 47.2 +/- 18.6 GrB 33.8 +/- 9.9) and MG (GrA 27.2 +/- 12.9 vs 19.0 +/- 9.9) were acceptable. LVEDD and LVESD regressed in both groups. LV mass indices regressed from 218.56 +/- 100.85 to 128.17 +/- 27.7 in GrA and 238.94 +/- 102.5 to 134.22 +/- 34.72 in GrB. Performance indices of implanted valves and postoperative aortic valve resistances were correlative.

CONCLUSIONS

The size of the implanted prostheses per se does not denote narrowness. Patient-prosthesis mismatch may be considered if predicted prosthesis has VSI <12 mm/m2, VAI <1.31 cm2/m2 or prosthesis orifice diameter <19 mm which may indicate annular enlargement.