Reply to Walther and Falk.

We 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.

Comment – Reply to Tang.

We appreciate Dr Tang’s interest in our study and are grateful for the opportunity to answer her questions. The basis for treatment selection in our study was not elusive, but based on the decision of a surgeon to try a new management strategy. Innovation can only happen if individuals have the courage to commit themselves to a new way. We were intrigued by the assumption that our diagnosis of sternal osteomyelitis rested largely on a clinical impression and not on microbiological criteria. In the methods section we explicitely described the microbiological culture findings for all patients in both groups [1]. As the extent of infection and type of organisms were comparable in both groups, the presented data can not invalidate the comparison between these modalities. We agree that adequate wound debridement is an important corner stone for eventual successful outcome, and practice radical wound debridement of all avital and infected tissues. Repetitive wound debridement was not necessary in all but one of our patients (in the conventional group). Also, at 5 weeks follow up, after discharge from rehabilitation, none of the patients had developed late fistulas or sinus formation involving sequestrated pockets of infected or necrotic tissues. Dr Tang points out two ways in which vacuum assisted therapy contributes towards a successful outcome of a sternotomy wound infection. However, she does not mention the foremost advantage over conventional therapy, which is the accelerated formation of granulation tissue. We demonstrated that even large defects can be covered within a short period of time and additional mutilating surgery can be avoided. That is the essence of our single centre experience.

References

1. Doss M., Martens S., Wood J.P., Wolff J.D., Baier C., Moritz A. Vacuum-assisted suction drainage versus conventional treatment in the management of poststernotomy osteomyelitis. Eur J Cardiothorac Surg 2002;22:934-938

Author(s): Martens S, Matheis G, Wimmer-Greinecker G, Scherer M, Doss M, Moritz A.

in: Cardiovasc Surg. 2003 Apr;11(2):159-63.