Obesity is associated with higher long-term mortality after aortic valve replacement with small prosthesis. 
Although many studies have evaluated the impacts of obesity on various medical treatments, it is not known whether obesity is related to late mortality with implantation of small aortic prosthesis.  This study evaluated the effect of obesity on late survival of patients after aortic valve replacement (AVR) with implantation of small aortic prosthesis (size ≤ 21 mm).  From January 1998 to December 2008, 536 patients in our institution who underwent primary AVR (307 patients with smaller prostheses) survived the 30 days after surgery.  Patients were categorised as normal weight if body mass index (BMI) was ≤ 25 kg/m(2), as overweight if BMI 25-30 kg/m(2), and as obese if BMI ≥ 30 kg/m(2).  Data were collected at the third-month (M), sixth-M, first-year (Y), third-Y, fifth-Y, and eighth-Y after operation.  By multivariable analysis, obesity was a significant independent factor of late mortality (hazard ratio [HR]: 1.59; p=0.006).  The obese and overweight groups of patients exhibited lower survival (p<0.001) and a higher proportion in NYHA class III/IV (p<0.01) compared with the normal group.  Lower EOAI and higher left ventricular mass index were found in the obese and overweight groups, but we saw no significant variance in LVEF among the three groups.  Obesity was associated with increased late mortality of patients after AVR with implantation of small aortic prosthesis.  Being obese or and overweight may also affect the NYHA classification, even in the longer term.