Aortic stenosis is the most prevalent cardiac valve pathology in the population, affecting approximately 12% of those over the age of 75, with severe cases present in 3.4%. The primary etiology of this condition is degenerative, particularly in developed and aging countries like Spain. 

It is well known that the classic definitive treatment of choice for this condition has traditionally been surgical aortic valve replacement (SAVR), and it continues to be for patients with low surgical risk. However, in recent years, there has been an observed increase in transcatheter aortic valve implantation (TAVI), primarily among patients with intermediate and high surgical risk, although it is now also being considered in some low-risk cases. 

On the other hand, there are two main challenges in universalizing TAVI as the treatment of choice: one is determining the ideal procedure based on patient type; the other is the controversy over whether this procedure should be performed in centers with on-site cardiac surgery. Regarding the procedure, recent results from the PARTNER 3 study indicate similar outcomes between surgical and percutaneous approaches in low-risk patients, which we will discuss in detail later. As for the formation of a Heart Team, having multidisciplinary teams, including cardiac surgeons to support the rest of the team in urgent conversions from percutaneous to surgical procedures (emergency open-heart surgery or E-OHS), seems logical, especially for certain risk groups. 

This brings us directly to the featured article of this entry, a multicenter analysis conducted in Germany between 2009 and 2021, involving 14 centers, on outcomes following E-OHS in patients undergoing TAVI. Out of the total 40557 patients who received TAVI, 216 required conversion to open surgery; however, only 152 met the inclusion criteria for this study. The main inclusion criterion consisted of patients who underwent transfemoral TAVI and experienced major intraprocedural complications requiring immediate open conversion. Exclusion criteria included non-transfemoral access, clinical and hemodynamic post-TAVI status, as well as interventions considered “minor” during the procedure (pacemaker implantation, pericardiocentesis, pleural drain insertion, etc.). Notably, all procedures were performed with a full Heart Team and, therefore, in centers with immediate cardiac surgery availability. The primary endpoint was all-cause one-year mortality. Secondary endpoints included intraprocedural mortality, in-hospital mortality, and various postoperative complications. 

For statistical analysis, the sample was divided according to different surgical risk groups based on the cutoffs established in the European clinical practice guidelines (CPG) using the EuroSCORE II scale: low-risk patients with EuroSCORE II <4%, intermediate-risk patients with a score between 4–8%, and high-risk patients with >8% risk. Respectively, these groups consisted of 46, 37, and 69 patients, making the high-risk group the largest, comprising nearly half of the total included patients. Variables indicating the need for surgical conversion included valve displacement or positioning failure (the most common, found in 31.6% of cases), left ventricular perforation, aortic annular rupture, events compatible with acute aortic syndrome, and/or dissection/obstruction of a coronary artery. Intraprocedural mortality was 12.5%, while in-hospital mortality rose to 49.3%, leaving 58 survivors. Common intraoperative complications included acute renal failure requiring renal replacement therapy, low cardiac output syndrome, and major bleeding, without forgetting stroke/neurological damage events, a complication that must always be considered in such patients and in this critical context, as we will discuss later. 

While statistical analysis showed no significant differences in intraprocedural mortality between groups, the authors observed a significant increase in in-hospital mortality in the high-risk group (59.4%). The estimated one-year mortality rate in Kaplan-Meier curves was 57.2%, also significantly higher in the high-risk group. 

Among the indications for E-OHS, coronary obstruction was identified as an independent predictor of increased one-year mortality rate, with no other statistically significant differences noted in other variables. 

In summary, half of the patients requiring E-OHS from a TAVI procedure survived the immediate postoperative period. Among them, those in the low and intermediate-risk groups had better outcomes than those in the high-risk group. Additionally, among those requiring surgical conversion, a low post-surgery event rate was observed, contributing to the high likelihood of adequate recovery and eventual discharge. 

COMMENTARY: 

Current guidelines from the European Society of Cardiology recommend TAVI for patients >75 years and/or at high surgical risk or considered inoperable, with a level of evidence I. Following the introduction, several studies have been published in recent years comparing TAVI with SAVR in high and intermediate-risk surgical patients, with some even suggesting potential benefits in the low-risk group. 

One of the most recently published studies supporting the percutaneous approach was DEDICATE, a clinical trial in which the authors concluded that TAVI was non-inferior to SAVR concerning all-cause mortality or stroke at one-year follow-up among patients with severe aortic stenosis and low surgical risk (although these results were questionable due to study design, among other factors, as previously discussed in this blog). 

However, the opposing side of this scientific evidence is portrayed in the extensively discussed PARTNER 3 study. Contrary to supporting the results of other studies, this trial shows that among low-risk patients with severe symptomatic aortic stenosis who underwent TAVI or surgery, there were no significant differences between groups in the two primary composite outcomes at five years (with an initially favorable trend for TAVI reversing at one and two years of follow-up). In fact, the short-term specific benefits of TAVI (lower mortality and stroke, shorter hospital stay, reduced rehospitalization, and lower bleeding rates) were diminished over time, with increased mortality and stroke rates in the TAVI group from the first year of follow-up. Thus, it is easy to understand why SAVR remains the therapy of choice for low-risk patients. 

So, what do we need to address these dichotomies in scientific evidence? Is the TAVI procedure still as safe and effective as we thought? Probably, this controversy highlights a reality we must not overlook and that, in fact, I would like to emphasize: 

• First, the gap in evidence regarding the prognosis of patients undergoing such interventions in terms of risk stratification. We are currently extrapolating TAVI risk based on risk scales traditionally used for surgery, and this is the case because a specific risk calculation system has not yet been developed for these patients undergoing percutaneous procedures, despite the expansion of the technique and the volume of data available today. Some have even proposed basing the indication on an arbitrary age criterion rather than focusing efforts on more prudent patient selection, as initially proposed with risk scales. Clearly, this shows that we cannot apply a class effect between the two treatments, and the need for a definitive risk quantification tool in this particular population is becoming increasingly urgent. 

• Moreover, many published studies do not have consistent inclusion (such as the type of individuals recruited, the type of percutaneous access, the types of valves used, etc.) and exclusion criteria (in fact, in this article, reference is made to a series of minor complications which, in my opinion, due to their incidence and impact on prognosis, introduce a bias per se at the time of analysis). This could potentially be a confounding factor that might go unnoticed without a thorough analysis of the collected data, and which, in my opinion, inexorably biases the evidence obtained, causing the current dichotomies we encounter. 

• Finally, returning to the title, while the percutaneous implant is a less invasive intervention than its surgical counterpart, with overall fewer risks, at least in the short term, it is still associated with potentially fatal complications. This is unacceptable in intermediate and, especially, low-risk patients (since in our setting, they constitute a significant proportion of the target population). Despite the high mortality, it is necessary to put it into perspective, considering that having the support of a cardiac surgery team for an emergency surgical conversion can save more than half of the patients who would otherwise present intraprocedural injuries incompatible with survival beyond the catheterization lab or hybrid operating room. 

Therefore, maintaining programs without a supporting cardiac surgery team seems negligent. The perspective of cardiovascular surgeons remains indispensable, from the initial patient assessment, technical implant alternatives (including open vascular access and managing their complications), to active participation during the procedure, beyond mere coverage for potential complications. Indeed, beyond the already argued surgical risk, the surgeon’s role is essential in determining whether, in the event of a severe complication, the patient is “operable” (able to receive extracorporeal circulatory support to resolve the complication or undergo conventional SAVR), “assistable, non-operable” (able to receive extracorporeal circulatory support as a bridge to recovery from hemodynamic complications or for intraprocedural complication management but not for conventional SAVR), or “non-assistable, non-operable” (close to the context of high surgical risk and potential futility, which would be the only alternative to consider in centers without Heart Team support). These practices were more frequent in the early days of TAVI programs over a decade ago. However, they have fallen out of favor and are now rare in our setting. The full integration of the surgeon into the Heart Team is a reality outside our borders from which we cannot, nor should we, remain isolated. 

REFERENCE: 

Marin-Cuartas M, de Waha S, de la Cuesta M, Deo SV, Kaminski A, Fach A, et al. Incidence and Outcomes of Emergency Intraprocedural Surgical Conversion During Transcatheter Aortic Valve Implantation: A Multicentric Analysis. J Am Heart Assoc. 2024 Jul 16;13(14):e033964. doi: 10.1161/JAHA.123.033964. Epub 2024 Jul 3.