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eComment: Prosthesis-patient mismatch: a need to individualize the preventive strategy according to the baseline characteristics of the patient

Quebec Heart and Lung Institute, 2725 Chemin Sainte-Foy, Quebec City, Que G1V 4G5, Canada

Is patient-prosthesis mismatch an independent risk factor for early and mid-term overall mortality in adult patients undergoing aortic valve replacement?

I read with great interest the article of Urso et al. [1] and agree with their conclusions. Several recent studies have emphasized that the clinical impact of prosthesis-patient mismatch (PPM) is not equivalent in all patients. First, it is highly dependent on its degree of severity, severe PPM having a more detrimental impact on outcomes than mild or moderate PPM. Second, the clinical consequences of PPM vary markedly depending on the preoperative characteristics of the patient. The impact of PPM is indeed more pronounced in younger patients, in patients with pre-existing LV systolic dysfunction and in those with severe LV hypertrophy. On the other hand, moderate PPM is generally well tolerated in elderly sedentary patients with preserved LV function, who represent the majority of patients undergoing aortic valve replacement (AVR). Moreover, it is important to emphasize that the utilization of the effective orifice area indexed to the body surface area may overestimate the degree of PPM in obese patients. Obesity thus needs to be taken into account when assessing the risk of PPM.

These findings underscore the importance of individualizing the PPM preventive strategy according to the severity of the anticipated PPM and to the patient’s baseline characteristics. Severe PPM should ideally be avoided in every patient undergoing AVR, whereas moderate PPM should be avoided in specific subsets of patients such as the young patients and those with depressed LV function and/or severe LV hypertrophy. So to the question: should we enlarge the aortic root to avoid a moderate PPM in the elderly patient presented in the article of Urso et al.? The answer is no. The scenario would be different if the patient was younger or had reduced LV ejection fraction. Even in this situation, the first line of prevention, prior to considering root enlargement, would be to implant another model of prosthesis with a better hemodynamic performance. In the prosthesis selection process, the first priority is to target models of bioprostheses that have a good track record in terms of durability (or thromboresistance for mechanical valves) and thereafter to select, among these models, the one providing the best hemodynamic performance. Moreover, the surgeon needs to take into account the implantability of the selected prosthesis because some models are more complex to implant, which may in turn increase operative risk. Root enlargement should be considered only in very specific cases when a severe PPM can not be avoided with the current models of prostheses and when the risk-benefit ratio is considered advantageous. Finally, transcatheter valve implantation may provide a promising alternative to prevent PPM in high-risk patients [2].

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1. Urso S, Sadaba R, Aldamiz-Echevaria G. Is prosthesis-patient mismatch an independent risk factor for early and mid-term mortality in adult patients undergoing aortic valve replacement. Interact CardioVasc Thorac Surg 2009;9:510–519.[Abstract/Free Full Text]
2. Clavel MA, Webb JG, Pibarot P, Altwegg L, Dumont E, Thompson C, De Larochellière R, Doyle D, Masson JB, Bergeron S, Bertrand OF, Rodés-Cabau J. Comparison of the hemodynamic performance of percutaneous and surgical bioprostheses for the treatment of severe aortic stenosis. J Am Coll Cardiol 2009;53:1883–1891.[Abstract/Free Full Text]

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