Background: In patients with severe aortic valve stenosis, transcatheter aortic valve replacement (TAVR) originally represented a therapeutic option for patients at high risk for surgical replacement of the valve (SAVR). However, recent data has shown non-inferiority of TAVR in patients with lower operative risk when compared to SAVR. This has led to a more liberal application of TAVR in patients at lower risk, but real-world data on these patients is still limited.

Objective: With this retrospective study we aimed to investigate clinical, procedural and prognostic differences of TAVR patients in low (LR), intermediate (IR) and high risk (HR) patients and to identify risk factors for an impaired cardiovascular outcome in patients within the LR group.

Methods: Patients with severe aortic stenosis, that were treated with TAVR, were stratified into three risk groups based on the Society of Thoracic Surgeons (STS) score (<4% LR, ≥4-8% IR, ≥8% HR). Clinical, procedural and post-procedural characteristics were compared between the three risk groups. Patients were followed up in order to assess the endpoints of all-cause mortality, stroke, bleeding complications and rehospitalization. Cox regression analyses were performed to investigate potential predictors of the combined endpoint in LR patients.

Results: We included 1461 patients with available STS scores, out of which 675 (46.2%) were in the LR, 566 (38.7%) in the IR  and 220 (15.1%) in the HR group. Patients in the LR group were significantly younger (median 81 years (interquartile range (IQR) 78-84 years vs. 84 years (IQR 81-87 years) vs. 86 years (IQR 82-89 years), p<0.001) and more often male (51.7% vs. 32.9% vs. 40.5%, p<0.001). There were no significant differences in the frequencies of cardiovascular risk factors between the groups except for diabetes, which was more common in the IR and HR groups (26.2% vs. 33.9% vs. 41.4%, p<0.001). Median high-sensitivity cardiac troponin, creatinine and CRP concentrations at admission increased with higher STS scores. In LR patients, the most common indications for TAVR were age and frailty. LR patients were treated more often with balloon-expandable valves than the other two groups (71.3% vs. 67.0% vs. 65.9%, p=0.161). The length of the procedure and the hospital stay were both significantly shorter in LR patients. LR patients received more often a permanent pacemaker (12.1% vs. 7.6% vs. 10%, p<0.001), but other intra- and postprocedural complications occurred less often. The endpoint of all-cause mortality (Figure 1) and the combined cardiovascular endpoint took place less often in the LR group and in all three groups in-hospital mortality was lower than predicted by the STS score (1.0% vs. 2.5% vs 2.7%). Higher creatinine concentration was found as the only independent predictor for an impaired cardiovascular outcome in LR patients (hazard ratio 1.27 (95% confidence interval 1.01-1.59) p=0.04).

Conclusion: In this real-world cohort, we were able to show that TAVR is safe and effective in patients with a low STS score. However, the rate of pacemaker implantations was higher in low risk patients as compared to intermediate and high risk groups. Impaired renal function was identified as a significant predictor for a poor cardiovascular outcome in low risk patients.

Figure 1: Kaplan-Meier survival curves for the endpoint all-cause mortality for patients in the low, intermediate and high risk groups treated with TAVR.