In cardiac surgery, neurological complications rank as the second cause of morbidity and mortality, following heart failure. These complications often leave severe sequelae, necessitating extended care. Stroke incidence attributable to cardiac surgery varies from 0.4% to as high as 14%, depending on the population studied, the type of procedure, and the number of concurrent interventions. According to data from the Society of Thoracic Surgeons (STS) database, stroke incidence shows variability, reaching 1.4% in isolated coronary surgery. This rate increases to between 1.3%-2.3% for isolated aortic or mitral valve repairs, respectively. In combined surgeries involving aortic or mitral valve replacement along with revascularization, stroke incidence rises to 1.9%-3.1%, respectively. For isolated aortic valve replacement, in alignment with the study under analysis, the incidence stands at 1.2%. 

Multiple studies on stroke related to cardiac surgery provide daily references, aiding surgeons in informing patients about early and late risks associated with this complication. However, for transcatheter therapies, long-term neurological complication data are lacking. Given the industry’s push to expand these therapies to low- or intermediate-risk patients, it is crucial to assess the impact of stroke in patients who have already received a TAVI. Without such data, the extended life years of a younger population with inherently longer life expectancy are at risk. 

Today’s study aims to investigate the short- and long-term incidence and predictors of stroke following TAVI implantation. The study used the SwissTAVI registry, analyzing all patients enrolled from February 2011 to June 2021. To compare stroke incidence with the general population, data from the 2019 Global Burden of Disease study was employed, using an age- and sex-matched cohort to calculate stroke trends in TAVI-treated patients. 

A total of 11,957 patients with an average age of 82 years, half of whom were women, were studied. One-third of patients had a history of atrial fibrillation, and 12% had experienced prior cerebrovascular accidents. The 30-day cumulative stroke incidence was 3%, with more than two-thirds of events occurring within the first 48 hours post-implantation. This incidence rose to 4.3% by the first year and 7.8% by the fifth year. When compared with an age- and sex-matched population, TAVI patients exhibited a higher stroke risk during the first two years: with a standardized stroke ratio (SSR) of 7.26 for men and 6.82 for women in the first year. In the second year, SSR decreased to 1.98 and 1.48 for men and women, respectively. From the third year onward, the stroke risk in the TAVI group became comparable to that of the general population. Age and moderate-to-severe paravalvular regurgitation were independent predictors of stroke within the first 30 days post-TAVI, while dyslipidemia, atrial fibrillation, and prior stroke history were independent predictors of late stroke. 

The authors concluded that TAVI patients have an elevated stroke risk in the first two years following the procedure, which aligns with the general population thereafter. 

COMMENTARY: 

The SwissTAVI registry is a national, prospective, multicenter registry for all patients receiving TAVI treatment in Switzerland. Enrollment in this registry is mandated by the Swiss Federal Office of Public Health and is a prerequisite for reimbursement by health insurance companies. Data from the registry are managed by an independent clinical trials unit that verifies accuracy, completeness, and statistical analysis. Given these strengths and a sample size of nearly 12,000 cases over a decade, this study may be one of the most robust on TAVI-related stroke. 

The reasons behind the elevated stroke risk during the first two years post-procedure are unclear. Excluding events occurring within the first 30 days post-procedure, the cumulative stroke incidence in TAVI patients was 1.4% in the first year and 1.2% in the second, decreasing to less than 1% from the third year onwards. One hypothesis for this increased risk involves prosthetic leaflet thrombosis, which lodges in the neosinuses formed between the native aortic valve on which the TAVI stent rests and the prosthetic leaflets. This phenomenon could be clinically relevant in 0.6%-2.6% of cases. Similarly, studies indicate that subclinical leaflet thrombosis prevalence is detected in up to 17% of patients within the first three months, increasing to 31% within the first year. Unfortunately, data beyond one year for this entity is unavailable, and its association with stroke remains inconsistent in the literature. Subclinical thrombosis has been observed to appear and disappear spontaneously, even with anticoagulant therapy. Other theories suggest endothelial dysfunction post-TAVI implantation or, more intriguingly, the onset of atrial fibrillation in up to 20% of patients within months following implantation. In this case, we lack a control group to determine if the incidence of silent atrial fibrillation increases post-procedure relative to a normal population. 

In closing, it is essential to consider study limitations. As registry data, critical information such as the incidence of clinical or subclinical prosthetic thrombosis is missing. Anticoagulation therapy protocols are also non-standardized, leaving the decision to the local Heart Team based on patient risk factors. Since 2015, cerebral protection devices have been used in Switzerland, although they are not universally adopted, as hospitals employ varying protocols. This variability introduces a confounding factor in data analysis. The control group was a Swiss population, making it unclear if findings would apply to a Hispanic population. Finally, it is important to remember that the average age of the study population was 82 years, meaning the conclusions should not be extrapolated to younger patients. 

In conclusion, this study is among the most significant on late neurological events post-TAVI, showing an elevated stroke risk within the first two years, with most early strokes occurring within the first 48 hours. These findings should prompt reconsideration of using these prostheses in younger patients and reconsider policies for early discharge within 48 hours. 

REFERENCE: 

Okuno T, Alaour B, Heg D, Tueller D, Pilgrim T, Muller O, et al. Long-Term Risk of Stroke After Transcatheter Aortic Valve Replacement: Insights From the SwissTAVI Registry. JACC Cardiovasc Interv. 2023 Dec 25;16(24):2986-2996. doi: 10.1016/j.jcin.2023.10.021.