Limitations in the Assessment of Prosthesis-Patient Mismatch

Abstract

Background Prosthesis-patient mismatch (PPM) after aortic valve replacement (AVR) may affect survival but data are conflicting. It is assessed by relating effective orifice area (EOA) to body surface area (EOAi). EOA is patient-specific as the result of flow-velocity times area at the individual patient's outflow tract levels (LVOTA) divided by trans-prosthetic flow velocity. However, some studies use projected EOAs (i.e., valve size associated EOAs from other patient populations) to assess how PPM affects outcome. Methods We analyzed 76 studies addressing hemodynamic outcome and/or mortality after bioprosthetic AVR. Results In 48 studies, projected or measured EOA for calculation of EOAi and PPM assessment was used (of which 25 demonstrated an effect on survival). We identified 28 additional studies providing measured EOA values and the corresponding Bernoulli's pressure gradients after AVR. Despite EOA being a patient-specific parameter, 77% of studies assessing a PPM impact on survival used projected EOAs. The 28 studies are providing measured EOA values and the corresponding Bernoulli's pressure gradients in patients after AVR showed a highly significant, linear relationship between EOA and Bernoulli's gradient. Considering this relationship, it is surprising that relating EOA to body surface area (BSA) (EOAi) is standard but relating pressure gradients to BSA is not. Conclusion We conclude that the majority of studies assessing PPM have used false assumptions because EOA is a patient-specific parameter and cannot be transferred to other patients. In addition, the use of EOAi to assess PPM may not be appropriate and could explain the inconsistent relation between PPM and survival in previous studies.

Patient Prosthesis Mismatch After SAVR and TAVR

“…Recently, the value of indexing EOA for PPM measurement has been discussed and re-evaluated, as it relates a measure of flow velocity to individual parameters two times (i.e., left ventricular outflow tract [LVOT] area and BSA) ( 13 ). In addition, based on a series of studies having measured Bernoulli's pressure gradients and patient-specific EOAs, Amorim et al identified a significant correlation of transprosthetic pressure gradients to EOA.…”

“…In particular, a low-flow state might result in a pseudo-severe PPM. In addition, depending on the aortic root anatomy, the echocardiographic cross-sectional transprosthetic jet area may differ more or less from the real area available for blood flow ( 13 ).…”

Editorial comment: “Plug‐In Hybrid”—Are we ready for this in heart valve surgery?

“…This risk can easily be avoided by using pledgeted sutures, although some surgeons may argue that in small aortic annuli, the placement of pledgets into the outflow tract may limit hemodynamic performance. 16 Supraannular placement of an aortic valve prosthesis has been described as a risk factor for PVL. 12,13 This may at first be surprising because a properly placed supra-annular prosthesis should be pushed onto the annulus during diastole, a mechanism which counteracts the development of PVL.…”

“…It should be clear that using upledgeted sutures (mainly for the aortic position) and running sutures may carry a greater risk of cutting through potentially friable tissue. This risk can easily be avoided by using pledgeted sutures, although some surgeons may argue that in small aortic annuli, the placement of pledgets into the outflow tract may limit hemodynamic performance 16 . Supraannular placement of an aortic valve prosthesis has been described as a risk factor for PVL 12,13 .…”

Effective orifice area is patient-specific!

“…Thus, it is patient-specific and the same prosthesis in 2 anatomically different patients will result in 2 different EAOs despite the same GOA of the prostheses. 2,3 What is referred to in the text as reference values for EAOs of SHV can therefore only be the mean of all individually measured EOAs after aortic valve replacement. The value thereby reflects the average hemodynamic result of what we do daily.…”