Ideal weight-based adjustment of overweight patients in aortic valve replacement

pp 90-95

Abstract

Study Objective

The indexed effective orifice area (EOA) calculated at the time of operation to predict patient-prosthesis mismatch after an aortic valve replacement is determined from the EOA of the prothesis and the patient's body surface area (BSA). The aim of this study was to establish whether the incidence of mismatch predicted at the time of an aortic valve replacement could be reduced when the BSA is calculated with the patient's ideal lean weight instead of his actual weight. 

Research design and methods

Seventy-seven consecutive adult patients undergoing aortic valve replacement with a bi-leaflet mechanical valve were evaluated. Obesity or overweight prevalence and patient-prosthesis mismatch projected with the indexed EOA were calculated. Indexed EOA determined by using preoperative patient's weight tabulated for sex, age and height. Cross-comparison between males and females with or without overweight were also performed. An indexed EOA < 0.85 cm²/m² was established to define mistmatch.

Results

Patient-prosthesis mismatch rate was 28.6% (22/77) for the whole sample and was reduced to 12.9% (10/77) when it was based on ideal tabulated weight (RR = 2.20, CI_95% 1.12 to 4.33, p= 0.017). Group with overweight had larger incidence of mismatch than patients with normal weight (43.3% (13/30) vs 19.1% (9/47), RR=2.26, CI_95% 1.11 4.63, p=0.022); this difference was corrected when mismatch was based on patients' ideal weight (6.67% 2/30) vs 17.0%  (8/47), RR=0.39, CI_95% 0.09 to 1.72, p=0.299). Coincidently with the initial hypothesis, the most important reduction in mismatch incidence was found among patients with overweight from 43.3% (13/30) to 6.67% (2/30), when determinations were done with actual and ideal weight respectively (RR=6.50, CI_95% 1.60 to 26.36, p=0.002).

Conclusions

Ideal weight-based indexed EOA calculation reduces patient-prosthesis mismatch in individuals with overweight and aortic valve replacement. Since obesity and overweight are modifiable risk factors, the former conclusion would reflect the requirement for patients undergoing valve replacement to be referred to surgery on ideal weight.