Surgical aortic valve replacement (SAVR) has consistently demonstrated favorable outcomes in both short- and long-term contexts. The advent of transcatheter aortic valve implantation (TAVI), initially designed for patients with prohibitive surgical risk and later extended to those with intermediate or even low risk, particularly those over 75 years of age, has led to exponential growth in its application across industrialized nations. This trend has consequently increased the number of patients with these percutaneous biological prostheses. Over time, it is expected that some of these prostheses may experience structural degeneration or prosthetic dysfunction due to complications such as endocarditis or paravalvular leaks, necessitating further surgical intervention. Moreover, these patients may develop other cardiovascular conditions, especially given that lower-risk patients with high long-term survival prospects are now being treated, which were either not present or untreated at the time of the TAVI procedure, thus requiring subsequent intervention. It is anticipated that in the coming years, the number of reinterventions in patients with these prostheses will increase in line with their expanded use. 

This study aimed to analyze the current trends and outcomes of cardiac surgery in patients who had previously undergone TAVI in the United States. For this purpose, the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database was used to evaluate all adult patients who had undergone cardiac surgery after receiving a TAVI between January 2012 and March 2023. A general cohort and two subcohorts were identified: non-SAVR cardiac surgeries and SAVR after TAVI. These cohorts were analyzed through descriptive statistics, trend analysis, and 30-day outcome evaluation. 

A total of 5457 patients were identified, of whom 2485 (45.5%) underwent non-SAVR cardiac surgery and 2972 (54.5%) underwent SAVR. The frequency of cardiac surgery after TAVI increased by 4235.3% overall, with an annual increase of 144.6% throughout the study period. Operative mortality and stroke rates were 15.5% and 4.5%, respectively. Existing STS risk models performed poorly, as observed versus expected mortality ratios were significantly disparate. Among those who underwent SAVR after TAVI, preoperative surgical urgency, age, dialysis, and concomitant procedures were associated with increased mortality, while the type of explanted TAVI prosthesis was not. 

The authors concluded that the demand for cardiac interventions, including SAVR after TAVI, is rapidly increasing. Associated risks are higher, and outcomes are worse than anticipated. 

COMMENTARY: 

Since TAVI approval for intermediate- or low-risk patients (over 75 years of age) as it was deemed non-inferior to SAVR in this patient group, and with the aging population, the indications for TAVI use have grown exponentially. However, numerous criticisms surround the conduct and evaluation of results from these clinical trials, which are shifting TAVI indications. These criticisms include highly selected study populations (patients without bicuspid aortic valves, average age above 70 years, preserved cardiac function, etc.), high pacemaker implantation and paravalvular leak rates, lack of long-term durability data, and 5-year results seemingly favoring surgery (as recently discussed on our blog). Conversely, the favorable outcomes of SAVR in low-risk, younger patients and even those with bicuspid aortic valves fuel ongoing controversy. 

Regardless, TAVI’s advancement is relentless, meaning we face the inevitability of reintervening on many of these patients in the near future. Two contrasting reintervention approaches merit attention: valve-in-valve versus surgical reintervention. These two alternatives yield notably different outcomes, as we discussed in detail on our blog. For example, Makkar et al., in a recent study published in The Lancet, demonstrated that redo-TAVI using the “valve-in-valve” technique with balloon-expandable prostheses resulted in low procedural complication rates and mortality and stroke rates comparable to those seen in patients undergoing TAVI for native aortic valve stenosis with a similar clinical and predicted risk profile. This suggests that “valve-in-valve” could be a reasonable option for selected patients with dysfunctional percutaneous bioprostheses, where feasible. Conversely, many patients with dysfunctional percutaneous prostheses are unsuitable for percutaneous treatment, as in cases of endocarditis, paravalvular leaks, mismatch with the second implant, technical factors such as coronary occlusion risk, among others. Thus, surgical treatment remains the only viable alternative. Reintervention in patients with percutaneous prostheses proves to be a high-risk operation, as demonstrated in numerous publications, including Fukuhara et al., which we reviewed on our blog nearly a year ago. 

The present study refutes what seemed to be a trend in outcomes and provides valuable insights into this type of intervention: 

• Firstly, the annual incidence of cardiac surgery following TAVI is exponentially increasing, particularly SAVR, since low-risk TAVI approval in 2019. 

• Secondly, the observed operative mortality for SAVR following TAVI is high, with an overall mortality rate of 15.8%, consistent with previous studies. 

• Thirdly, TAVI explant and subsequent surgical implant required an operation involving the aortic sinuses or root in 28.8%, with full root replacement necessary in 13.4%. 

Given all the aforementioned doubts about the outcomes of recent low-risk clinical trials, we now face the fact that the risk of mortality and morbidity associated with SAVR following TAVI is 5 to 10 times higher than with a primary SAVR. This further complicates decision-making by the Heart Team when evaluating aortic stenosis in patients potentially eligible for either alternative. 

Several contemporary reports, including large institutional series, have observed a recent increase in high-risk TAVI explant and SAVR for premature structural valve degeneration or paravalvular leaks. Other national multicenter registries further confirm the technical complexity and elevated mortality of TAVI explant and SAVR, ranging from 13% to 19%. The present study provides the most up-to-date STS analysis, examining national trends and outcomes for this rapidly expanding operation. Compared to the predicted risk of primary SAVR for aortic stenosis, typically between 1% and 2% mortality for most patients, the mortality risk for non-urgent SAVR following TAVI was over 15%. The corresponding increase in major morbidity risk, such as stroke (4.5%) and renal failure (11.1%), and the need to perform an aortic or root procedure in nearly a third of patients, clearly differentiate non-AVR cardiac surgery and SAVR following TAVI as more complex operations from both technical and outcome perspectives. This might warrant exploration of a new independent risk model for these operations in the future. 

There are no significant tips or tricks regarding surgical technique, but from the description of multiple published clinical cases, several recommendations can be drawn: 

• The recommended approach is median sternotomy, as hemi- or mini-sternotomy may be insufficient for repairing damage and/or replacing the aortic root, performing coronary bypass surgery, or conducting concomitant mitral valve surgery. 

• Retrograde cardioplegia administration is highly recommended due to the low viability of direct cardioplegia perfusion through the coronary ostia. 

• A high aortotomy is advised, especially with self-expanding prostheses, following a “J” shape. Once the prosthesis is identified, the aortotomy is extended to the aortic annulus in the noncoronary sinus. 

• The next step is to find a dissection plane between the aortic valve and the prosthesis. Cold solution is recommended to help contract the nitinol frame of self-expanding prostheses (cold cardioplegia aids in this effect). For balloon-expandable prostheses, two Kocher clamps or similar tools can be used to maneuver and deform the frame. 

• Some authors also recommend placing a silk or 3-0 polypropylene suture through each of the three proximal cells of the prosthesis and tightening it to counteract the radial force during extraction, allowing a deeper dissection to the prosthesis’s lowest point. 

Despite these steps, damage to the aortic root is often inevitable when tissues are calcified, fragile, and highly compressed. 

The STS database, although voluntary, is estimated to capture 97% of all procedures performed and is considered one of the most rigorously validated surgical registries in healthcare, with 98% audited accuracy in 2022. However, this database presents other relevant limitations, such as the lack of predicted SAVR mortality risk calculation at the time of TAVI or information on the temporal relationship between prior TAVI and subsequent cardiac surgery. It also lacks specific echocardiographic parameters that could provide additional insights into aortic valve pathoanatomy, and follow-up imaging was not available. The reported outcomes are limited to 30 days, restricting the current observations to short-term insights. 

In light of these findings, TAVI explant could become a high-risk procedure that will likely grow increasingly common in cardiac surgery. Prior to performing this procedure, thorough preoperative planning is essential due to the significant technical challenges involved in explanting the percutaneous prosthesis without damaging the aortic root. With this in mind, as TAVI indications continue to expand, it is incumbent upon surgeons to advocate for rational decision-making within the Heart Team to make the best choice for patients with aortic stenosis. 

REFERENCE:

Bowdish ME, Habib RH, Kaneko T, Thourani VH, Badhwar V. Cardiac Surgery after Transcatheter Aortic Valve Replacement: Trends and Outcomes. Ann Thorac Surg. 2024 Apr 3:S0003-4975(24)00254-6. doi: 10.1016/j.athoracsur.2024.03.024.