By Michael H. Crawford, MD, Editor
Synopsis: A large U.S. database study comparing mechanical vs. bioprostheses for surgical aortic valve replacement in patients 40 to 75 years of age has shown that all-cause mortality is reduced with a mechanical valve in those age 60 years or younger.
Source: Bowdish ME, Mehaffey JH, Chang SC, et al. Bioprosthetic vs mechanical aortic valve replacement in patients 40-75 years. JACC. 2025; Jan 25. doi: 10.1016/j.jacc.2025.01.013. [Online ahead of print].
Current surgical practice in the United States has shown a trend toward using bioprosthetic aortic valves for adults of all ages. However, there is a paucity of data about the outcomes of this practice in patients < 65 years of age. Thus, this study of all adult isolated surgical aortic valve replacements (SAVRs) from the Society of Thoracic Surgeons (STS) database, which captures 97% of all U.S. cardiothoracic surgeries, is of interest.
The STS database was integrated with the U.S. National Death Index from the Centers for Disease Control and Prevention to determine the primary endpoint of all-cause mortality in this retrospective observational study. First, SAVR procedures from 2008 until 2019 were examined. Excluded were those < 40 years of age or > 75 years of age, emergency surgeries, cardiogenic shock patients, patients with left ventricular ejection fraction < 25%, and patients with prior heart surgery.
Several sensitivity analyses were performed: excluding pure aortic regurgitation patients, excluding those with an STS predicted risk of operative mortality (PROM) > 4%, and excluding those who received discontinued bioprosthetic valves. From the 109,842 SAVR patients in 1,082 programs, 86% had a bioprosthetic valve replacement and 14% had a mechanical one. Over the course of the study, mechanical valve use decreased from 20% in 2008 to 10% in 2019. Bioprosthetic valve patients were older (mean age 65 years) than mechanical prosthesis patients (mean age 56 years). Also, mechanical prosthesis patients had higher PROM scores.
Over the mean 5.4-year follow-up, raw outcome data showed that all-cause mortality was less in those receiving mechanical valves up to about age 60 years. Risk-adjusted outcome data mirrored this result. All the sensitivity analyses also confirmed these results. The authors concluded that a mechanical aortic valve prothesis had a risk-adjusted survival advantage compared to a bioprosthetic valve with SAVR in those 60 years of age or younger.
Commentary
With more than 100,000 patients, this is the largest observational study of isolated SAVR to date. It has shown that despite declining use of mechanical prostheses in the United States for SAVR, all-cause mortality was significantly lower than that observed with bioprostheses in those aged 40-60 years. Previous studies were not only smaller but were based on institutional- or state-level data that mainly used billing codes or claim data and lacked the robust clinical detail available in the STS database.
The STS includes comorbidities, procedural characteristics, and other factors that could introduce bias if not taken into consideration. The factors thought to be of the most potential effect were studied using sensitivity analyses in the STS study and confirmed the main results.
There are limitations to the STS study. Since it is a retrospective observational study, causality cannot be demonstrated. There was no assessment of frailty, which has been shown in other studies to be predictive of outcomes. The use of transcutaneous aortic valve replacement (TAVR) after SAVR also was not assessed. The possibility of a future valve-in-valve TAVR is one of the rationales used for selecting a bioprosthesis over a mechanical one. In addition, there was no consideration of long-term bleeding or thromboembolic outcomes. Finally, these were isolated SAVR patients, and those with concomitant coronary bypasses were not included.
Current U.S. guidelines recommend SAVR in those < 65 years of age, TAVR in those > 80 years of age, and either procedure in those 65-80 years of age. It is estimated that in current U.S. practice, about 50% of those < 65 years of age receive a TAVR. This analysis of the STS data suggests that SAVR with a mechanical prothesis may be a better option in those < 60 years of age.
Michael H. Crawford, MD, is Professor of Medicine and Consulting Cardiologist, University of California Health, San Francisco.
A large U.S. database study comparing mechanical vs. bioprostheses for surgical aortic valve replacement in patients 40 to 75 years of age has shown that all-cause mortality is reduced with a mechanical valve in those age 60 years or younger.
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