Echocardiographic Parameters Continue to Improve in Patients with Self-Expandable Transcatheter Aortic Valve for Failing Bioprosthetic Aortic Valve Replacement

Since the initial TAVR in a degenerated surgical aortic bioprosthesis (ViV TAVR) in 2007,1.Wenaweser P Buellesfeld L Gerckens U Grube E Percutaneous aortic valve replacement for severe aortic regurgitation in degenerated bioprosthesis: the first valve in valve procedure using the corevalve revalving system.Catheter Cardiovasc Interv. 2007; 70 (doi: 10.1002/ccd.21300): 760-764Google Scholar ViV TAVR has grown in prominence in treating degenerative aortic bioprosthetic valves. Coupled with the current surgical trends, this less invasive procedure is likely to continue to increase for many years to come. Prior publications have suggested a mean gradient ≤ 20 mmHg is a desirable result post procedure, associated with reduced mortality in a series of balloon-expandable valves2.Webb J Mack M White J et al.Transcatheter aortic valve implantation within degenerated aortic surgical bioprostheses.JACC. 2017; 69 (doi: 10.1016/j.jacc.2017.02.057): 2253-2262Google Scholar but not noted with self-expandable valves3.Deeb M Chetcuti S Reardon M et al.One-year results in patients undergoing transcatheter aortic valve replacement with failed surgical bioprostheses.JACC Cardiovas Interv. 2017; 10 (doi: 10.1016/j.jcin.2017.03.018): 1034-1043Google Scholar We hypothesized that the reason for this difference is that the self-expandable valve platform continued to expand with continued decrease in mean gradients out to 1 year. We retrospectively reviewed detailed clinical, echocardiographic, and fluoroscopic data of patients who underwent ViV TAVR at our institution. Data was manually reviewed and abstracted from the electronic medical record, the echocardiographic studies and fluoroscopic images. This was a retrospective study approved by the Aurora IRB, and informed consent was waived. Data analysis was carried out using SAS Version 9.4 (SAS Institute, Cary, NC). Patient characteristics were calculated as mean ± standard deviation for continuous variables and counts (proportions) for categorical variables. Comparison of categorical variables was conducted using the Chi-square or Fisher’s exact test as appropriate. Repeated measures ANOVA was used to test differences in aortic gradient, aortic valve area, Doppler velocity index over time. The two sample t-test or the paired t-test was used to assess differences for continuous variables. All tests were performed at a 5% level of significance. We evaluated 93 high-risk patients (mean STS score 8.26 ± 6.47) with failing bioprostheses. Thirty-four (36.6%) were female, 59 (63.4%) were male with the mean age of 76 ± 10.1. The majority of patients were Caucasian (n = 87, 93.6%). In our population, 48.4% (n = 45) had essential hypertension, 45.2% (n = 42) had coronary disease, 21.5% (n = 20) had diabetes mellitus, 14% (n = 13) had chronic obstructive pulmonary disease, 8.6% (n = 8) had prior stroke, and 4.3% (n = 4) had pulmonary hypertension. The method of bioprosthetic failure was stenosis in 62 (67.7%), regurgitation in 18 (19.1%), and mixed stenosis and regurgitation in 13 (14%). All patients successfully underwent self-expanding ViV TAVR (n = 27 CoreValve, n = 66 Evolut; Medtronic, Minneapolis, MN). On 24-hour follow-up, 44 (47.3%) patients had elevated gradient (mean > 20 mmHg). There were no statistical differences among the various comorbidities between the gradient < 20mmHg cohort and the > 20mmHg cohort. Patient-prosthesis mismatch was present in 37 (39.3%) of patients (normal gradient n = 15, elevated gradient n = 22). The presence of patient-prosthesis mismatch (p = 0.04), small implanted TAVR size (64.4% in elevated group vs. 36.7% normal group for 23 mm valve, p = 0.01) and higher baseline mean (40.4 ± 15.2 vs. 33.4 ± 14.5; p = 0.26) and maximum gradients (73.8 ± 25.9 vs. 61.5 ± 24.4, p = 0.02) were univariate predictors of elevated gradient after ViV TAVR. At 1-year echocardiographic surveillance, the mean aortic valve area remained stable (Figure 1 – Panel A) (p = 0.83) and mean aortic gradients continued to decrease throughout 1 year (Figure 1 – Panel B). The absolute difference between the immediate procedural gradient (i.e., 24 hours) and one year was 5.7 mmHg (95% CI 3.64 mmHg−7.79 mmHg, p < 0.01); this was equivalent to a 26.75% percent change from 24 hours to 1 year (95% CI 26.73%–26.78%, p < 0.01). This change was not associated with significant change in stroke volume (24-hour post-TAVR 83.1 ± 25.5 vs. 1-year post-TAVR 84.09 ± 26.7, p = 0.98) or in left ventricular ejection fraction (24-hour post-TAVR 54.1% ± 1.5 vs. 1-year post-TAVR 55.4% ± 1.4, p = 0.75). Doppler velocity index also improved over one year (Panel C). In the 70 patients with 1 year of follow-up, mortality was 14.2% (5 cardiac and 5 non-cardiac deaths) and the mean time to death was 4.4 months ± 4.2; although sample size was small, elevated gradients did not predict mortality (OR 1.54, 95% CI 0.60–3.99; p = 0.37). In conclusion, echocardiographic hemodynamics continue to improve post-ViV TAVR in patients followed up to 1 year with self-expandable valve, even in patients with higher initial post-procedure gradients. This is similar to findings reported with self-expandable valve in native aortic valve stenosis.4.Oh JK Little SH Abdelmoneim SS et al.Regression of paravalvular aortic regurgitation and remodeling of self-expanding transcatheter aortic valve: an observation from the CoreValve U.S. Pivotal trial.JACC Cardiovasc Imaging. 2015; 8 (doi: 10.1016/j.jcmg.2015.07.012): 1364-1375Google Scholar In that study, evaluating 634 patients with self-expandable valves for native aortic stenosis, the authors noted that mean gradients, effective orifice area, and aortic valve velocity continued to improve up to 1 year. They postulated that the nitinol frame of the self-expandable valve continued to expand and remodel the aortic root out to 1 year. We hypothesize that expansion and remodeling also occur in valve-in-valve TAVR, and the improved parameters we observed are a reflection of the continued expansion and remodeling of the self-expandable valve, which sits mostly supra-annular to the bioprosthetic sewing ring. We also hypothesize that this may be part of the underlying reason that mean gradient > 20 mmHg was not found to be associated with clinical deterioration in patients with valve-in-valve using self-expandable TAVR.3.Deeb M Chetcuti S Reardon M et al.One-year results in patients undergoing transcatheter aortic valve replacement with failed surgical bioprostheses.JACC Cardiovas Interv. 2017; 10 (doi: 10.1016/j.jcin.2017.03.018): 1034-1043Google Scholar For a high, surgical-risk population with failing bioprosthetic aortic valve, ViV TAVR with self-expandable valves demonstrates continuous improvement in Doppler-derived parameters up to 1 year. Further research with more longitudinal information may continue to yield encouraging results. The authors gratefully acknowledge Jennifer Pfaff and Susan Nord of Aurora Cardiovascular Services for editorial preparation of the manuscript, and Brian Miller and Brian Schurrer of Aurora Research Institute for their help in preparing figures. No potential conflict of interest was reported by the authors.