The medical community continues to debate the optimal timing for aortic valve replacement in patients with severe asymptomatic aortic stenosis (AS). A 2018 paper raised concerns about the reliability of unblinded trials, highlighting terms like "faith healing" and "subtraction anxiety." Additionally, the distinction between soft clinical endpoints, such as symptoms and hospital admissions, and more objective endpoints, like mortality, remains a critical point of discussion. This debate is fueled by evolving guidelines and recent trial outcomes, influencing decisions for both Transcatheter Aortic Valve Replacement (TAVR) and Surgical Aortic Valve Replacement (SAVR).
The 2020 guidelines from the American College of Cardiology (ACC) and American Heart Association (AHA) provide a class I indication for aortic valve replacement in patients with severe asymptomatic AS if certain conditions are met. These include impaired left ventricular (LV) ejection fraction below 50% or concurrent cardiac surgery. Expert authors, including Eugene Braunwald, MD, advocate for earlier valve replacement in such patients.
Trial Outcomes and Clinical Implications
Recent randomized controlled trials (RCTs) have provided insights into the benefits of SAVR and TAVR. These trials have demonstrated positive outcomes for the endpoints evaluated. For instance, the EVOLVED trial showed no superiority of SAVR over surveillance for a composite endpoint comprising death or unplanned AS-related hospitalization. This result may be attributed to the extended delay between assignment and intervention, as noted by JAMA Cardiology editorialists.
“In our opinion, the routine and preferred strategy for asymptomatic patients with severe AS (stage C1) should shift from clinical surveillance, the current default strategy, to prompt performance of aortic valve replacement” – JAMA Cardiology editorialists.
Conversely, the AVATAR trial indicated that SAVR outperformed watchful waiting for a composite endpoint of death, stroke, myocardial infarction, or heart failure hospitalization. The RECOVERY trial further supported SAVR's superiority for a composite endpoint involving operative mortality and cardiovascular death after a median follow-up of six years. These findings underscore the need for nuanced decision-making in clinical practice.
TAVR Versus SAVR: Weighing Risks and Benefits
The procedural risks associated with TAVR have significantly diminished over the past 35 years, with substantial evidence supporting its benefits. However, questions about the relative durability of TAVR compared to SAVR remain pertinent due to younger patients' longer life expectancy following valve replacement.
“Advocating for TAVR in asymptomatic younger patients — many if not most of whom may have bicuspid aortopathy — is a triumph of interventional optimism over actual evidence” – Joanna Chikwe, MD.
Mechanical valves used in SAVR may offer better long-term performance than TAVR devices, adding another layer to the decision-making process. Moreover, SAVR might prove more cost-effective than TAVR, potentially influencing treatment choices based on economic considerations.
The 2021 guidelines from the European Society of Cardiology emphasize impaired LV function as the sole class I indication for aortic valve replacement in asymptomatic AS. This highlights the ongoing debate within the medical community regarding appropriate intervention strategies.
Expert Opinions and Future Directions
Prominent cardiologists continue to weigh in on these complex issues. Samin Sharma, MD, suggests that TAVR or SAVR could be recommended for asymptomatic severe AS patients above 75 years of age due to available clinical evidence and prosthetic valve degeneration considerations.
“Based on the available clinical evidence and factoring in the prosthetic valve degeneration, it will be prudent to recommend TAVR or SAVR in asymptomatic severe AS patients above 75 years of age,” – Samin Sharma, MD.
Despite such recommendations, he also urges caution in making final recommendations, advocating for further research before definitive guidelines are established.
“we need to wait a little more before making the final recommendation” – Samin Sharma, MD.
Similarly, Christopher Rajkumar, MD, PhD, cautions against drawing premature conclusions from RCTs that show rapid divergence in Kaplan-Meier curves post-randomization without clear evidence of disease progression.
“In a chronic progressive condition like AS, we expect to see events accumulate steadily with time. But if Kaplan-Meier curves diverge immediately and rapidly after randomization, we have to question whether these events reflect disease progression” – Christopher Rajkumar, MD, PhD.
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