Insights from what was described as the “largest and most comprehensive” analysis of isolated surgical aortic valve replacement (SAVR) procedures in bicuspid aortic valve stenosis were presented at the 58th annual meeting of The Society of Thoracic Surgeons (STS 2022; 29–30 January, virtual).
Research presented by Sameer Hirji from the group led by Tsuyoshi Kaneko (Brigham and Women’s Hospital, Boston, USA) aimed to quantify the longitudinal impact of isolated SAVR in bicuspid valves compared to tricuspid valves, to establish a five-year benchmark for outcomes in bicuspid stenosis patients.
There is an increasing interest in performing transcatheter aortic valve implantation (TAVI) in this group given recent expansion of indications, Hirji said in his STS presentation. However, he noted that currently there is much to be learned about this patient population due to their exclusion from all of the major randomised trials for SAVR versus TAVI.
Through their study, utilising data from the STS Adult Cardiac Surgery Database, the research team said their analysis would help to improve heart team decision making, and for use in the design of future trials.
“To better inform conversations around SAVR in bicuspid patients, the aim of the study was to analyse the short-term and five-year longitudinal cardiovascular outcomes of isolated SAVR in bicuspid compared to tricuspid aortic valve patients, particularly those at low risk,” Hirji said.
The retrospectively-analysed prospective cohort study included all adults undergoing index isolated SAVR procedures for aortic stenosis between 2011–2018 in the STS database, which collected data from over 1,200 participating centres. In total this included 9,131 bicuspid patients and 56,556 tricuspid patients.
The study’s primary outcomes were 30-day mortality or five-year mortality, while secondary outcomes included major bleeding, permanent stroke, acute kidney injury, pacemaker implantation, hospital and intensive care unit (ICU) length of stay.
Hirji detailed that in terms of demographics and comorbidities, the bicuspid cohort was significantly younger, with a mean age of 70 compared to 75 in the tricuspid cohort.
“The bicuspid patient cohort was younger, with lower risk profiles and categorically there was a higher proportion of bicuspid valve patients with low risk scores,” Hirji said.
Furthermore, he detailed that bicuspid patients had a lower rate of urgent surgery, but without a meaningful difference in cardiopulmonary bypass times. Bioprosthetic valves were placed in more than 90% of both patient groups.
Turning to the results of the analysis, Hirji detailed that the unadjusted operative mortality (1.3% vs. 2.3%) and major morbidity (8.3% vs. 11.3%) were lower in bicuspid patients, but noted that operative mortality and major morbidity were similar after risk adjustment (both p>0.05).
Furthermore, long-term mortality was significantly lower in the bicuspid patient cohort after risk adjustment (aHR 0.72 (95% confidence interval [CI]: 0.660.77), mainly driven by the low-risk (PROM <3%; aHR 0.68 (95%CI: 0.62‒0.75) and intermediate-risk score patients (PROM 3‒8%; aHR 0.77 (95% CI: 0.67‒0.89)), and normal LVEF patients (aHR 0.69, 95%CI: 0.63‒0.75).
Additionally, there was a significant long-term readmission risk reduction in the bicuspid cohort for heart failure, stroke, bleeding, and any cardiovascular causes (all p<0.05), he said.
In his concluding remarks, Hirji described the research as the largest and most comprehensive analysis of isolated SAVR procedures in bicuspid patients, noting that 30-day mortality and morbidity were low in both patient cohorts.
“Importantly, this study emphasises the fact that SAVR outcomes are excellent, which should facilitate informed decision making and patient counselling in the context of lifetime management of aortic valve stenosis,” he said.
However, Hirji noted that limitations of the research include that it was an observational study, that there was a lack of independent adjudication or adverse events, and that researchers could not account for the variability of surgeons or patient selection biases
In a question and answer session following the presentation, Tom Nguyen (University of California San Francisco, San Francisco, USA) noted that bicuspid valves are important but under-studied disease process both in surgery and the transcatheter space, commenting: “There is still so much that we do not know”.
He asked Hirji to comment on the fact that five-year mortality was lower in the bicuspid valve cohort. “Doing a SAVR in a bicuspid valve patient is tricky, so in terms of the long-term outcomes, we think that there are potentially multiple variables that could account for the differences in survival that we are seeing,” said Hirji in response, citing unmeasured confounding and differences in genetic risk inherent in both bicuspid and tricuspid aortic stenosis.
Further to this, Nguyen asked whether, given recent data showing worse outcomes from TAVI in bicuspid versus tricuspid valves—should the findings from Hirji and team point toward greater utilisation of SAVR rather than TAVI for bicuspid valves patients.
“There is definitely emerging data showing the feasibility of TAVI in this patient population,” said Hirji, pointing to a recent analysis by Raj Makkar (Cedars-Sinai, Los Angeles, USA) et al published in the Journal of the American Medical Association (JAMA) which found that there were no significant differences in outcomes among patients at low surgical risk who had undergone TAVI for bicuspid aortic stenosis, as well data from the Evolut Low Risk study programme, which suggest that patients with bicuspid aortic stenosis may benefit as much from TAVI as those with tricuspid aortic stenosis.
“For TAVI, the outcomes and complications are highly dependent on the anatomy itself and it depends on the bulk of the calcium leaflet, the morphology, [and] the sub annular calcium—so it is hard to compare the two populations without a head-to-head comparison, because there is so much nuance to the approach in clinical decision-making for the TAVI population at this point,” said Hirji.
The decision to opt for TAVI or SAVR should be weighed against three factors, he said; one is the anatomical risk, the second of which is the presence of existing aortopathies, and finally, the risk for reintervention. “Without a formal head-to-head comparison, equipoise between the two procedures continues,” he noted.