OBJECTIVE: Percutaneous aortic valve implantation has been performed in patients with severe aortic stenosis judged as nonsurgical candidates. We evaluated a facilitated transapical antegrade approach for potential use in surgical high-risk patients.
METHODS: A pericardial xenograft fixed within a 23-mm stent (Cribier-Edwards aortic prosthesis, Edwards Inc., Irvine, CA, USA) was implanted using a transapical approach in fifteen 35-45 kg pigs. A limited or a full sternotomy was used to transapically introduce a crimped valve through a 24-F sheath. Deployments were performed on the beating heart either with ventricular unloading using femoro-femoral cardiopulmonary bypass (CPB) or rapid ventricular pacing (RVP), all under fluoroscopic and echocardiographic visualization.
RESULTS: All valves were successfully deployed at the target site with acceptable visualization of the noncalcified annulus. Valve migration occurred in six procedures (three distal and three retrograde) secondary to inadequate reduction of ventricular output, unfavorable annular anatomy, excessive crimping of the valve, and dislodgement by the delivery balloon. Exact positioning of the valve into the target area was confirmed by autopsy at the end of the procedures. Paravalvular leak was noted in five implants.
CONCLUSIONS: The transapical approach provides a safe, accurate, and effective route for facilitated antegrade delivery of a stent-fixed valve. Advanced stent design will lead to better stability of the implant and may minimize the risk of paravalvular leakage in future. Identifying the appropriate population for human feasibility trials remains a challenge.
Author(s): Walther T, Dewey T, Wimmer-Greinecker G, Doss M, Hambrecht R, Schuler G, Mohr FW, Mack M
in: Eur J Cardiothorac Surg. 2006 May;29(5):703-8. Epub 2006 Apr 5.
This paper was presented at the Annual Meeting of the European Society of Thoracic Surgeons No13, Barcelona , Spain (25. Sept. 2005)
PMID: 16600616 [PubMed - indexed for MEDLINE]
Reply to Walther and Falk.
August 21, 2003 — dossmedicalWe appreciate the attention that Walther et al. showed in our recent article and would like to point out the following issues in response to their comments. Walther and colleagues suggest that our patient cohort is to small to allow for a meaningful analysis. We disagree! Without employing any statistical tests, any clinician will agree, that there is no clinically relevant difference between a mean gradient of 6.5 mmHg and one of 7.4 mmHg, or an ejection fraction of 64.6% and one of 66.6%. Also, a posterior wall thickness of 1.32 cm or one of 1.26 cm has no clinical relevance for the patient. Medically speaking, we would expect to need at least 15–20% differences between the groups to get a clinical relevance. The differences between the groups however, are in the region of 1–2%. Based on the relatively small sample size, after consulting our statisticians and the statisticians from Edwards Life Sciences, who have helped us design and evaluate our study, we can expect to pick up differences of 20% under this constellation.
With regard to intraoperatively measured annular diameters, we found no relevant differences between the groups (21.6 versus 22.4 mm). The subsequently implanted valve sizes are shown in Table 2 of our article [1]
Walther et al. imply that our article lacks information on indexed differences of left ventricular (LV) mass. We would like to call to their attention that we have separately reported all measurements that run into the equation of determining LV-mass index in Tables 1 and 3 of our article for both groups [1].We feel that the reader can thus better understand that there were no significant differences in the single components, rather than just seeing that the indexed end product did not differ.
Walther et al. go on to cite their article in which they report a significantly enhanced LV-mass regression after stentless aortic valve replacement [2]. They compared two different types of stentless valves with one stented valve, in groups that were of different sizes (n=49+n=57 versus n=74). Looking at the gradients that they report it appears that a reduction in transvalvular gradient by 1.4 mmHg (from postop 18.1 mmHg to 16.7 mmHg for stentless valves, with the stented valve gradients remaining at 20.1 mmHg) is statistically significant.
Furthermore, it appears that a pressure difference of 3.4 mmHg is enough to cause a significant reduction in LV-mass hypertrophy.
In our experience these minimal changes in pressure gradients cannot be held accountable for a more complete or faster regression of LV-mass. Our findings were similar to the findings of Cohen et al. from the Cleveland Clinic, who also conducted a prospectively randomized trial comparing stentless with stented aortic valves, and who also found no significant differences in hemodynamic performance or reduction in LV-mass between the groups [3].
In the current environment of science it is, however, not uncommon that different groups, investigating similar projects, come to different conclusions.
References
1. Doss M., Martens S., Wood P., Aybek T., Kleine P., Wimmer-Greinecker G., Moritz A. Performance of stentless versus stented aortic valve bioprostheses in the elderly patient: a prospective randomized trial. Eur J Cardiothorac Surg 2003;23:299-304.
2. Walther T., Falk V., Langebartels G., Krüger M., Bernhardt U., Diegeler A., Gummert J., Autschbach R., Mohr F.W. Prospectively randomized evaluation of stentless versus conventional biological aortic valves: impact on early regression of left ventricular hypertrophy. Circulation 1999;100(19 Suppl):II6-II10
3. Cohen G., Christakis G.T., Joyner C.D., Morgan C.D., Tamariz M., Hanayama N., Mallidi H., Szalai J.P., Katic M., Rao V., Fremes S.E., Goldman B.S. Are stentless valves hemodynamically superior to stented valves? A prospective randomized trial. Ann Thorac Surg 2002;73:767-778.
Author(s): Doss M.
in: Eur J Cardiothorac Surg. 2003 Aug;24(2):335-6.