Background:
Surgical aortic valve replacement (SAVR) has long been the standard treatment for severe aortic valve stenosis. This study analyzes the current state of in-hospital mortality and complication rates for stroke, acute kidney injury (AKI), delirium, and ventilation >48h in the context of annual hospital case numbers and further influencing factors.

Methods:
All isolated SAVR procedures and in-hospital outcomes in 2017 were identified by ICD and OPS codes. Hospitals were divided into 5 volume groups from ≤25 until >100 annual procedures. Logistic regression analysis was carried out to evaluate risk factors.

Results:
In 2017, 5,533 patients underwent SAVR in Germany, of these 154 in the lowest volume group. Patients in all groups had comparable risk (mean logistic EuroSCORE 5.12-4.80%) and age (66.6-68.1 years). Unadjusted rates of in-hospital mortality as well as complications were lowest in highest volume group (0.98%; 1.64%; 6.27%; 9.66%; 4.95%). Using centers with ≤25 cases per year as reference, risk-adjusted data showed a significant inverse volume-outcome relationship for AKI in the highest volume group (OR=0.53; p=0.036). No significant correlation was seen in mortality, stroke, and ventilation >48h after risk-adjustment. Significant risk factors for in-hospital mortality were previous cardiac surgery (OR=5.75, p<0.001), high grade renal disease with glomerular filtration rate (GFR) <15ml/min (OR=5.61, p=0.002), surgery in emergency cases (OR=2.71, p=0.002), higher grade heart failure NYHA III/IV (OR=1.80, p=0.022), and age (OR=1.03, p=0.031). Risk factors on all four in-hospital complications were atrial fibrillation and diabetes mellitus. Risk factors on at least one complication were EuroSCORE, coronary artery disease, and higher grade renal disease. As also seen in in-hospital mortality, a higher grade heart failure NYHA III/IV was related to a higher rate of AKI and ventilation >48h, while a lower one showed a lower rate of ventilation >48h. Also, lower rates of at least one in-hospital complication were observed in patients with female gender and previous coronary artery bypass graft.

Conclusion:
Data show that low and high volume centers have comparably good outcomes in SAVR. While a further high concentration of operations remains in high volume centers in Germany, small hospitals are also important in order to ensure sufficient supply with SAVR.


Figure: Outcomes in SAVR per hospital category in 2017