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Is there a relationship between moderate prosthesis patient mismatch and long-term
- Murat Biteker, Mehmet Özkan (16 December 2008)
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Moderate patient-prosthesis mismatch can impact on mortality after aortic valve replacement
- Jean G. Dumesnil, Julien Magne, Nicolas Girerd, Philippe Pibarot (2 August 2008)
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Murat Biteker, Cardiology Resident Kosuyolu Heart and Research Hospital, Mehmet Özkan
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murbit2{at}yahoo.com Murat Biteker, et al.
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To the Editor: We read with great interest the article by Mascherbauer and coworkers, (1) in which they reported the short-term and long-term mortality results of moderate patient-prosthesis mismatch (PPM) after valve replacement for severe aortic stenosis. PPM, generates a great controversy with respect to its clinical relevance and in relation to its effect on survival after operation. Evidence of an association between PPM and survival is inconsistent. Although PPM is sub-classified according to the effective orifice index area (EOIA) of a prosthetic valve as mild (>0.85 cm²/m²), moderate (0.65–0.85 cm²/m²), or severe (<0.65 cm²/m²), several studies have debated whether PPM affects short and long-term survival (2). In the present study moderate PPM found to be no major impact on perioperative and long-term survival after valve replacement for isolated severe aortic stenosis. Since surgical procedures designed to avoid PPM, by enlarging the aortic root, increase the complexity of the operation and its operative mortality, the present study emphasizes that such an operative strategy may not be justified in patients undergoing aortic valve replacement (AVR) for isolated severe aortic stenosis to prevent moderate PPM. However, it is not clear why moderate PPM had no impact on long-term survival. Moderate PPM may have negative impact on actually long-term outcome which may be more than 4.2 years, that may relatively correspond to native aortic valve stenosis. Hence mean follow-up duration of 4.2 years may not be considered as ‘long-term’. In the previous studies PPM is a strong and independent predictor of short and long term mortality among patients undergoing AVR (3). Furthermore it was showed that the worse the degree of PPM and the severity of left ventricular dysfunction, the greater the impact of PPM on patients’ outcomes (4). In their series, authors reported only 5.6% patients presented with left ventricular dysfunction, therefore this subgroup appeared too small for seperate analysis as they mentioned. Hence, we think that including only the subgroup of patients undergoing AVR referred to surgery for isolated severe aortic stenosis, this should considered to be a limitation. While only 10.7% of the patients in the PPM group received mechanical valve 47.9% of these patients without PPM have mechanical valve. Moreover, 67% of the patients with bioprosthetic valve (175 out of 261) had suffered PPM which were relatively overrepresented as compared to previously reported bioprosthetic valves that were associated with high insidence of PPM (5). In conclusion, we think that further clinical trials focussed on patients with PPM especially who received bioprosthetic valves may be warranted before making any definitive recommendations References 1-Mascherbauer J, Rosenhek R, Fuchs C, et al. Moderate patient-prosthesis mismatch after valve replacement for severe aortic stenosis has no impact on short-term and long-term mortality. Heart 2008;94:1639-45. 2-Pibarot P, Dumesnil JG. Prosthesis-patient mismatch: definition, clinical impact, and prevention. Heart 2006;92;1022-1029 3-Tasca G, Mhagna Z, Perotti S, et al. Impact of prosthesis-patient mismatch on cardiac events and midterm mortality after aortic valve replacement in patients with pure aortic stenosis. Circulation 2006;113:570–6. 4-Blais C, Dumesnil JG, Baillot R, et al.Impact of Valve Prosthesis-Patient Mismatch on Short-Term Mortality After Aortic Valve Replacement. Circulation 2003;108;983-988. 5-Botzenhardt F, Eichinger WB, Bleiziffer S et al. Hemodynamic comparison of bioprostheses for complete supra-annular position in patients with small aortic annulus. J Am Coll Cardiol. 2005; 21:2054-60 |
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Jean G. Dumesnil, M.D Quebec Heart Institute, Julien Magne, Nicolas Girerd, Philippe Pibarot
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jean.dumesnil{at}med.ulaval.ca Jean G. Dumesnil, et al.
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Dear Editor, We have read with interest the article of Mascherbauer et al.[1] recently published in Heart and we congratulate our colleagues for an honest effort on shedding some light on an important issue which is still generating some controversy. Nonetheless, based on the title and the conclusions of both the abstract and the paper, we are concerned that the paper may unfortunately convey the wrong message i.e. that moderate prosthesis-patient mismatch should never be a concern in patients undergoing aortic valve replacement. Moreover, from the introduction, justification for the study appears to be based on the perception that our previous papers were recommending “that even left ventricular outflow tract enlargement may be justified to prevent moderate PPM”. In fact, we have never made such an unqualified recommendation. Indeed, our findings as well as those of others [2] show that the impact of moderate PPM on outcomes is most significant in patients with LV dysfunction as compared to patients without dysfunction (e.g. early mortality = 16% vs 5%, p< 0.001) and our recommendation has always been that if PPM is anticipated, alternative options should be considered in light of the patient’s overall clinical condition and the risk to benefit ratio of doing such procedures. Unfortunately, the number of patients with LV dysfunction in the present study is too small to do any analysis in this regard. Moreover, LV dysfunction might even be a confounding variable since it was significantly more prevalent (15.2% vs 5.6%, p = 0.003) in the patients without PPM and hence, it could explain the relatively high mortality observed in this group (5.5%). Indeed, operative mortality for AVR in patients without LV dysfunction is usually 1-4% and if such had been the case, the markedly higher operative mortality (10.2%) observed in the group with PPM might have become statistically significant. Notwithstanding this consideration, the statistical power of the study is clearly limited. Indeed, the difference in short-term mortality (5.5% vs. 10.2%) between the 2 groups did not reach statistical significance (i.e. p=0.14 with Yates correction in the results section and in Table 4, or p=0.098 without Yates correction in the Table 3). However, considering the previous study of Blais et al. [3] for sample size estimation, the inclusion of 361 patients leads to a statistical power of only 43% for the analysis of operative mortality. Moreover, using the same percentage of operative mortality in the two groups, but with a sample size of 880 patients (i.e. corresponding to the number of patients which would have result in a 80% a priori statistical power), the p-value would have been of 0.009 (without Yates correction). Hence, had the same sample size been closer to that of previous series, the findings and conclusions of the paper could have been entirely different. Furthermore, as opposed to the perception given in the article of Mascherbauer et al., aortic root enlargement is certainly not the only and/or first line option to avoid PPM. The preventive strategy should rather be focused primarily on the implantation of prosthesis models providing a better hemodynamic performance and thereby a larger EOA in relation to patient’s annulus size. And in this regard, several recent studies have demonstrated that PPM can successfully be avoided or its severity reduced with the use of such strategy. [4-6] Given these limitations, the present paper provides little new information and the findings certainly do not justify the unqualified conclusion that moderate PPM has no impact on short or long term mortality which implies that it can almost be ignored. To the contrary, we reiterate that the projected indexed EOA should always be calculated at the time AVR and that the decision with regards to the prosthesis to be implanted should be made in light of the patient’s overall clinical condition. Clearly and based on many concurring data in the literature, every effort should be made to avoid severe PPM in every patient undergoing aortic valve replacement and moderate PPM if LV dysfunction and/or severe LVH is present. Finally, it should be mentioned that the underestimation of EOA in bi-leaflet prosthesis is based on in vitro studies and that this has not been shown to be a consistent finding in vivo. Indeed, recent studies using either the indexed EOA measured at predischarge exam or the projected indexed EOA derived from in vivo reference values demonstrated that the same cut-off values for indexed EOA were valid to predict outcomes in their series of patients with bi-leaflet mechanical prosthesis. [7;8] Moreover, in one of these studies, even a moderate PPM was shown to negatively impact long- term survival after adjustment for other risk factors. [8] References [1]. Mascherbauer J, Rosenhek R, Fuchs C, Pernicka E, Klaar U, Scholten C, Heger M, Wollenek G, Maurer G, Baumgartner H. [2]. Ruel M, Al-Faleh H, Kulik A, Chan K, Mesana TG, Burwash IG. [3]. Blais C, Dumesnil JG, Baillot R, Simard S, Doyle D, Pibarot P. [4]. Bleiziffer S, Eichinger WB, Hettich I, Guenzinger R, Ruzicka D,
Bauernschmitt R, Lange R. [5]. Dalmau MJ, Gonzalez-Santos JM, Lopez-Rodriguez J, Bueno M,
Arribas A, Nieto F. [6]. Kunadian B, Vijayalakshmi K, Thornley AR, de Belder MA, Hunter
S, Kendall S, Graham R, Stewart M, Thambyrajah J, Dunning J. [7]. Mohty D, Malouf JF, Girard SE, Schaff HV, Grill DE, Enriquez-
Sarano ME, Miller FA, Jr. [8]. Kohsaka S, Mohan S, Virani S, Lee VV, Contreras A, Reul GJ,
Coulter SA. |
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