The results of a combined analysis of the STS/ACC/TVT Registry and the Centers for Medicare and Medicare Services (CMS) were presented by Dr. Mayra Guerrero, an interventional cardiologist and Professor of Medicine at Mayo Clinic Hospital, at TCT 2019. The analysis suggests that a transcatheter mitral valve-in-valve implantation may be preferable to repeat mitral surgery and should be the standard of care in patients with favorable anatomy.
Patients who undergo surgical mitral valve replacement typically have a high risk of requiring a repeat procedure for a failing surgical prosthesis. In these patients who require repeat mitral valve surgery, the risk of operative mortality is also high, ranging from 6.3% to 17.8%. Mitral valve-in-valve implantation (MViV) has become an alternative to repeat surgery and has already received FDA approval. Previous registries have demonstrated that the 30-day mortality in patients who undergo MViV is approximately 8%. However, with the improvement in technology, it is not known whether MViV outcomes have changed over time. The investigators aimed to assess the more contemporary outcomes in patients who undergo MViV replacement, compare the different approaches to MViV replacement (Transseptal versus transapical) and to determine the predictors of procedural and 1-year mortality.
“The 30-day mortality in both groups was lower than predicted, it was about 5% in the transseptal group when the predicted mortality was 11%, so we have an observed to expected ratio of 0.45, and in the transapical arm, it was around 8% when the predicted was around 11.7% and still with a ratio that is very favorable of around 0.6. So both options are better than surgery.” – Dr. Mayra Guerrero, M.D.
This was a retrospective review of data from the STS/ACC/TVT Registry and the Centers for Medicare and Medicare Services (CMS). A total of 1,576 patients who underwent a MViV procedure between June 2015 and August 2019 were included in the analysis. Outcomes of transseptal and transapical procedures were compared. Also, an observed to predicted ratio of 30-day mortality was calculated for each group, with the predicted mortality rate calculated using the Society of Thoracic Surgery (STS score). Additionally, univariate and multivariable analyses were conducted to determine predictors of mortality by 1 year. Finally, in-hospital outcomes and 30-day mortality rates between the two groups were also assessed.
In the final analysis, 1,326 patients (86.7%) underwent a MViV procedure through a transseptal approach and 203 (13.3%) patients had their MViV procedure done through a transapical approach. While baseline characteristics and baseline echocardiographic characteristics were overall balanced between the two groups, patients in the transseptal group had a higher prevalence of atrial fibrillation and a lower proportion had a previous history of coronary artery bypass grafting (CABG). Patients in the transseptal group had a higher fluoroscopy time (37 minutes vs. 18.2 minutes, p < 0.0001) and a lower conversion rate to open surgery (0.7% vs. 2.5%). Both the transseptal approach and the transpical approach had a high success rate (97.1% and 94.6%, respectively). The overall 1-year mortality rate, when the two groups were combined, was 16.7%. However, patients in the transseptal group had a significantly lower 1-year mortality rate as compared to those in the transapical group (15.8% vs. 21.7%, HR 0.67, 95% CI 0.47-0.97, p = 0.03) and a lower rate of cardiovascular death (3.7% vs. 5.7%, p = 0.07), although the difference in cardiovascular death rates was not statistically significant. Additionally, patients in the transapical group had a higher rate of in-hospital cardiovascular death (4.4% vs. 1.8%, p = 0.03), longer length of stay (6 days vs. 2 days, p < 0.0001) and were less likely to be discharged home (59.1% vs. 82.5%, p < 0.0001). Also, 30-day all-cause mortality and cardiovascular death mortality was higher in the transapical group as compared to the transseptal group (All-cause mortality: 8.1% vs. 5%, p = 0.07; Cardiovascular death: 5.1% vs. 2.1%, p = 0.01). However, in both groups, the ratio of observed to predicted mortality was less than 1 indicating that patients in both groups had better outcomes than predicted (0.45 in the transseptal group and 0.69 in the transapical group).
Finally, when assessing the predictors of 1-year mortality, the investigators found that a transapical approach, a lower baseline Kansas City Cardiomyopathy Questionnaire (KCCQ) score, lower glomerular filtration rate, the occurrence of cardiogenic shock within 24 hours of admission, moderate to severe tricuspid insufficiency, the occurrence of perforation with or without tamponade during the procedure, and conversion to open surgery were all associated with an increased risk of mortality by 1 year.
“For the first time, we actually found a difference in mortality between the transseptal and transapical access. At 1 year, the difference became statistically significant with a p-value of 0.3. In 1 year, the mortality in the transseptal group was 15% and 21.7% in the transapical group. Just for comparison, in the TVT registry for high-risk TAVR population, it has been more than 20% in 1 year. So this is very encouraging.” – Dr. Mayra Guerrero, M.D.
In Dr. Guerrero’s interview with Dr. C. Michael Gibson, an interventional cardiologist at Beth Israel Deaconess Medical Center and Professor of Medicine at Harvard Medical School, she highlighted the relatively lower mortality rate in the two groups. She said, “the 30-day mortality in both groups was lower than predicted, it was about 5% in the transseptal group when the predicted mortality was 11%, so we have an observed to expected ratio of 0.45, and in the transapical arm, it was around 8% when the predicted was around 11.7% and still with a ratio that is very favorable of around 0.6. So, both options are better than surgery.”
Although the data would suggest that MViV is better than repeat mitral surgery, the study does come with limitations. The registry was non-randomized and the outcomes were reported sites. There was no independent adjudication of adverse events and the reported adverse event rate may be lower than the true event rate. Finally, the registry excluded patients enrolled in clinical trials. Therefore, more complicated patients who were excluded from the trials could have been enrolled in this registry.
Ultimately, the data seems to suggest that MViV could potentially be the standard of care for patients who have a failed mitral valve replacement and favorable anatomy. When commenting on the future direction of mitral valve repair, Dr. Guerrero noted, “I think now we have data to suggest that transcatheter mitral valve replacement, either transseptal or transapical, but particularly transseptal, is a better option than repeat surgery in high-risk patients.” She also said, “in terms of clinical practice, if we see a patient who has a high risk of surgery, I think transcatheter mitral valve should be the new standard of care. If we accept that as the new standard of care, it may impact the type of surgical valve that patients get now. If someone needs to have the first initial mitral valve replacement, perhaps, the discussion about the type of valve should involve maybe choosing a valve that can be favorable for a mitral valve in valve in the future.”
Click here to watch Dr. Guerrero’s interview with Dr. Gibson.
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