Editor's Corner: TAVR Moving Forward: Good News, Important Reminders from EuroPCR and SCAI
Transcatheter aortic valve replacement (TAVR) continues to be a major topic in the yearly cycle of meetings – this time from EuroPCR and SCAI. For TAVR, there are a number of reports and trials that are indeed good news going forward. The first is REPRISE III – the long awaited safety and efficacy study of the Lotus valve (Boston Scientific). The novel Lotus valve allows functional assessment after placement but prior to release, and is repositionable and retrievable if positioning is not as expected. Like the currently approved Edwards and Medtronic valves it has a “skirt” to minimize paravalvular leak. REPRISE III is unique in that it is the first trial that compared valves head–to-head: Lotus versus Medtronic’s CoreValve classic and CoreValve Evolut R valves.
In REPRISE III, the Lotus valve was non-inferior to the CoreValves regarding patient safety at 30 days and one year. Importantly, the Lotus valve met its primary effectiveness endpoint, showing a significantly lower rate of disabling stroke and paravalvular leak compared with CoreValve. However, not all the news was perfect – there was almost twice the need for pacemaker implantation with the Lotus system and the stroke rate in the CoreValve arm was higher than expected. As with the CoreValve system, experience with implantation techniques will almost certainly decrease the rate of pacemaker need going forward. The data will certainly be used to try to gain approval from the U. S. Food and Drug Administration, but redesign issues are still in place for the Lotus valve, and final approval is likely not around the corner.
Good news for TAVR also came from updated numbers from the PARTNER 2 (Valve-in-Valve) Registry. The short version of the update is that there was improved mortality compared with previous reports. Earlier results showed 30-day and one-year mortality rates of 4.1 percent and 13.4 percent, respectively. In the updated registry, 30-day and one-year mortality rates were 2.7 percent and 12.4 percent, respectively. A learning curve is clearly in force for valve-in-valve procedures. Finally, the reported low rates of paravalvular regurgitation, new pacemaker implantation and no cases of annular rupture are no surprise, since the rigid annular ring of the previous prostheses limit these complications.
One issue that continues to vex interventionalists performing these procedures is the problem of patient-prosthesis mismatch in cases where the original surgically implanted valve is too small for the patient’s body mass index. Many surgical valves that are currently deteriorating have rigid sewing rings that cannot be expanded further when the valve-in-valve procedure is performed. Aside from ongoing patient-prosthesis mismatch, a valve-in-valve procedure done in a small surgical prosthesis may be a problem for valve longevity. Constrained valve expansion and/or malcoaptation may accelerate leaflet degeneration.
Notably in the report from EuroPCR, 27 percent of failed surgical bioprostheses were 21 mm or less. Attempts to fracture the rings to allow a larger “new” valve to be implanted have been largely unsuccessful, but this concept bears watching. The whole valve-in-valve issue has wider implications. For example, instead of implanting a surgical bioprosthetic valve in young patients, should the strategy be to do a TAVR (with its better hemodynamics, but possible future deterioration), thereby allowing for a future, more successful valve-in-valve procedure if needed? I doubt we are anywhere near that strategy yet. For my young patients with aortic stenosis, surgical options still seem the best until we know much more.
Further news concerning valve durability has also been positive. A study from Italy reported up to nine-year follow-up, with the study truncated at seven years. In 13 Italian centers with more than 2,300 patients, there was a low rate of bioprosthetic deterioration. Only 20 prosthesis-related events occurred (though with six deaths), which computes to an annual rate of 0.2 percent to 1.5 percent. Supporting studies from Denmark and Germany point out that surgical bioprosthetic valves seem much more likely than TAVR valves to demonstrate deterioration (though the differences were driven by moderate degeneration) and exhibit more central regurgitation. No cases of thrombosis were reported. In the German study, the rate of emergent cardiac surgery or PCI (presumably due to valve deterioration) was also only 2.8 percent, and the rates of paravalvular leak did not change over time.
The issue of valve deterioration, especially related to valve thrombosis, remains a challenge. The ongoing randomized Galileo trial (pitting standard dual antiplatelet therapy against anticoagulation with rivaroxaban) will hopefully give us considerable insight into the rates at which TAVR valves develop thrombosis and whether standard dual antiplatelet therapy is indeed the best option.
Finally, a reminder from SCAI that atrial fibrillation (AFib), even after TAVR, cannot be neglected. The BRAVO-3 trial randomized almost 1,000 patients to treatment with either bivalirudin or unfractionated heparin. Bleeding, the primary endpoint, was the same between the two groups. However, in a post-hoc analysis approximately one of three TAVR patients had AFib that was present at baseline or developed after TAVR. Surprisingly, patients with new-onset AFib had a nearly five-fold increased risk of stroke at 30 days, while patients with pre-existing AFib did not have an increased risk of stroke compared with patients without AFib. Patients without AFib had a 30-day stroke rate of 2.6 percent; those with presenting AFib had a rate of 3.1 percent; and new-onset AFib patients had a stroke rate of 10.5 percent. In the analysis, despite the high prevalence of AFib post TAVR and high CHA2DS2-VASc scores, only 65 percent of patients were treated with anticoagulants on discharge.
The message from BRAVO-3 seems clear, even if this is a post-hoc analysis – post-TAVR AFib is under-appreciated, and seems to present a high risk of post-TAVR stroke. Anticoagulation post TAVR can be tricky, with the standard need for additional antiplatelet therapy. Nonetheless, sending post-TAVR patients home without any anticoagulation does not seem appropriate. Clearly further data are needed to sort out this concerning issue.
Peter C. Block, MD, FACC is a professor of medicine and cardiology at Emory University Hospital and School of Medicine in Atlanta, GA.
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