Bioprosthesis degeneration is an event that, in the past, surgeons preferred to avoid and would send patients home after the initial consultation and consent signing, often reassuring them, “don’t worry, this prosthesis will last longer than you.” When early structural degeneration occurred, the initial annoyance was followed by a phase of concern, eventually leading to resignation to a new surgery, which was sometimes delayed if the dysfunction had no symptomatic impact or ventricular function repercussions. Many cases of early degeneration likely slowed the enthusiasm that initially led to the implantation of bioprostheses in younger patients, due to the lack of long-term data we now possess. Despite our hopes, we were essentially replacing one valvular disease with another, inevitably linked to the prosthesis’ performance. 

The advent of transcatheter aortic valve implantation (TAVI), combined with a more active lifestyle, encouraged the liberal use of bioprosthetic implants, either to compete with the percutaneous option or out of confidence in the concept of re-valving, initially termed “valve-in-valve (ViV)” or, more accurately, “valve-in-prosthesis.” As with all trends, the preference for bioprostheses recurred, further fueled by limitations of mechanical valves, especially the inability to use new oral anticoagulants in patients with atrial fibrillation. 

This study raises questions about the appropriateness of the liberal use of bioprostheses and, if degeneration occurs, whether the best option is reoperation (Re-SVA) or percutaneous treatment in patients with comparable and acceptable surgical risk. As a prelude to the results, it is worth mentioning a recently published study comparing bioprostheses to mechanical prostheses for aortic valve replacement in patients of similar age, which found better long-term survival with mechanical prostheses, especially when avoiding patient-prosthesis mismatch and the use of small 19 mm prostheses. 

With this premise in mind, we reviewed the study, which included patients from across the United States, from centers located in New York and New Jersey on one coast, and California on the other. Between 2015 and 2020, a total of 1,771 patients with degenerated bioprostheses underwent invasive procedures. After propensity score matching, 375 patients were included in each group: those undergoing ViV versus Re-SVA. As previously noted, the methodology of propensity score adjustment has significant limitations if not executed correctly. However, it is worth highlighting that this study employed an extensive variable model with comprehensive stratification and subsequent bias control, achieving truly comparable groups with notable morbidity. High rates of severe morbidities were reported, including diabetes mellitus in over 40%, peripheral arterial disease in more than 25%, cerebrovascular disease in 20%, atrial fibrillation in nearly half of the sample, chronic obstructive pulmonary disease (COPD) in about one-fifth, and a concerning proportion of patients (20%) with a history of cancer, with a mean age of 68 years. A notable limitation is that patients did not initially undergo isolated aortic valve procedures, as many had concomitant surgeries, though these were comparable between groups. Moreover, a distortion remains, as the study included patients reoperated for procedures unrelated to the aortic valve, with or without associated procedures during follow-up. 

The findings were clear: 

• A lower rate of periprocedural complications and early mortality with the percutaneous option, likely reflecting good case selection for the interventional approach. These differences did not reach statistical significance for all-cause mortality at two years. 

• Higher rates of mortality and heart failure from two years onward with the percutaneous option, with statistically significant divergence of survival curves extending to the maximum five-year follow-up. 

The authors concluded that the percutaneous approach yielded poorer long-term outcomes, though they suggested that prospective, randomized studies are warranted to confirm these results, considering potential confounding factors. 

COMMENTARY: 

The study presented adheres to the familiar narrative in cardiology literature when compared to surgical options: hastily selected patients with a “whatever works” approach, incomplete or omitted data, and conclusions reluctantly accepted when the findings are not favorable to their interests. 

First, in studies focused on this subject, the absolute number of bioprosthetic implants remains undisclosed, preventing the determination of degeneration rates or the number of patients with degenerated prostheses who were not deemed candidates for successive treatments. This crucial information is systematically omitted, aligning with the general medical and cardiology approach of treating at all costs, even if this leads to morbidity from previous treatments that generate preventable clinical scenarios. Put differently, by prioritizing beneficence (sometimes questionably, regarding for whom it serves), the principle of primum non nocere—or, at least, minimizing harm—is often overlooked. 

As surgeons, we must distinguish ourselves from this approach. In my view, most cases of bioprosthesis degeneration, even if not early, are undesirable events and should unequivocally be considered complications. Exceptions could include cases where the patient consents to bioprosthesis implantation despite a high degeneration risk, for reasons such as avoiding the risks or interference of oral anticoagulation, underlying pathologies contraindicating anticoagulation, or the reproductive desires of young women, among others. However, I do not consider it appropriate to turn this exception into the rule, nor to advise patients toward the “biological pathway,” especially if they are young and low-risk. 

Second, the reported outcomes may have been affected by a lack of control over confounding factors, which may have escaped propensity score adjustment. In the absence of randomization, if local Heart Teams chose who to operate on and who to treat percutaneously (with percutaneous treatment theoretically offering better morbidity and mortality profiles given equal risk and strong predictors against technical complications), they likely did so for good reason. This could explain the survival curve divergence observed at the two-year mark. 

A more skeptical view would highlight what is not stated over what is. Notably absent are post-procedural gradient data once bioprosthesis dysfunction has been addressed. As a clue, the heart failure rate aligns with the all-cause mortality rate, suggesting that percutaneous approaches may not be systematically advisable for operable degenerating bioprostheses. This insight is crucial not only for interventional cardiologists but also for surgeons, who must acknowledge responsibility for both the prosthesis agreed upon with the patient and the obligation to reoperate when complications arise. The current approach advocated by interventional cardiology to perform disproportionate and theoretically non-mismatched “oversized” aortic implants for future re-valvings appears unjustifiable. It doubles the procedural risk by adding an “aortic surgery” score item in risk assessments and seems inappropriate when the patient, at that moment, may not benefit and instead may face complications. Besides potential prosthesis-patient mismatch, re-valving carries additional morbidities, such as an increased thrombotic event rate, which was also not reported in this study. 

In summary, this commentary, more than the study itself, serves as a call for all members of the Heart Team to exercise responsibility in decision-making with patients. Each prosthesis has its specific indication and therapeutic niche, and as specialists, we are obligated to identify this. Sometimes, certain options may lack glamour, excitement, or immediate benefit; however, given the evidence and independent of industry interests, we are responsible for providing the best option for each patient at the time. If this doesn’t satisfy us, perhaps it’s time to reflect. 

REFERENCE:

Tran JH, Itagaki S, Zeng Q, et al. Transcatheter or surgical replacement for failed bioprosthetic aortic valves. JAMA Cardiol. 2024;9(7):631-639. doi:10.1001/jamacardio.2024.1049.