A Retrospective Analysis of Standardized Gradient Calculations for Evaluating Patient-Prosthesis Mismatch Following Mechanical Aortic Valve Replacement.

Abstract

Background: Aortic stenosis (AS) is one of the most common valvular heart diseases, particularly in the elderly, with a prevalence of approximately 3% in individuals over 75 years of age. Aortic valve replacement (AVR) remains the standard treatment, yet postoperative hemodynamic assessment is often complicated by variations in prosthetic valve size, left ventricular ejection fraction (LVEF), effective orifice area (EOA), and body surface area (BSA). These factors significantly influence prosthetic valve function and contribute to patient-prosthesis mismatch (PPM), which has been associated with worse clinical outcomes. Traditional transvalvular gradient measurements often fail to account for these patient-specific variables. This study introduces a novel approach to standardized gradient calculations, aiming to enhance the accuracy and comparability of prosthetic valve assessments. Methods: A retrospective analysis was conducted on 115 patients who underwent mechanical AVR at a single center. Patients were categorized into three groups based on the prosthetic valve type: St. Jude Medical (SJM) HP (n = 31); SJM Regent (n = 54); and those who underwent aortic root enlargement (ARE) (n = 30). Preoperative and postoperative transthoracic echocardiography (TTE) was performed to measure conventional and standardized transvalvular gradients. Four novel standardized gradient calculations were developed to adjust for individual hemodynamic differences, improving the accuracy of prosthetic valve function assessment. Results: Standardized gradient calculations demonstrated significant differences between prosthesis types. Postoperative standardized gradients were significantly higher in the SJM HP group compared to the SJM Regent and aortic-root-enlargement groups (p < 0.001, p < 0.05). The lowest standardized gradients were observed in patients who received the SJM Regent prostheses (p < 0.05). Although conventional measurements showed no significant differences, standardized calculations revealed that patients with 19 mm prostheses exhibited significantly higher transvalvular gradients than those with 21 mm prostheses (p < 0.05), emphasizing the clinical importance of prosthesis size in postoperative hemodynamics. Conclusions: Standardized gradient calculations provide a more objective, reliable, and patient-specific assessment of prosthetic valve function by minimizing interpatient variability. This approach improves the detection of patient-prosthesis mismatch and optimizes postoperative hemodynamic evaluation, potentially leading to better prosthesis selection and surgical decision-making. However, further validation is required in larger cohorts before these methods can be widely adopted into clinical practice. Future studies should assess their impact on long-term clinical outcomes, including left ventricular remodeling and patient survival.