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Expanding indications for TAVR: The preferred procedure in intermediate-risk patients?

December 1, 2017|Cleveland Clinic Journal of Medicine
David L. Brown, MD
Author and Disclosure Information

David L. Brown, MD
The Heart Hospital Baylor Plano, Baylor Scott & White Health, Plano, TX

Correspondence: David L. Brown, MD, 1100 Allied Drive, Plano, TX 75093; David.brown@BSWHealth.org

This article is based on Dr. Brown’s presentation at the Sones/Favaloro Scientific Program, “Transforming the Delivery of Cardiovascular Care: Research and Innovation in the Heart & Vascular Institute,” held in Cleveland, OH, November 18, 2016. The article was drafted by Cleveland Clinic Journal of Medicine and was then reviewed, revised, and approved by Dr. Brown.

Dr. Brown reported no financial interests or relationships that pose a potential conflict of interest with this article.

ABSTRACT

Transcatheter aortic valve replacement (TAVR) has steadily replaced surgical aortic valve replacement (SAVR) in symptomatic patients with severe aortic stenosis, primarily those at high risk for surgical complications. As TAVR use increases, spurred by technological advances in valve design and patient preferences for the less-invasive procedure, studies have provided data supporting the efficacy and safety of TAVR. Recently, TAVR has expanded to intermediate-risk patients, increasing the potential patient population. Although emerging evidence supports its use in lower-risk patients, some adverse events may limit its adoption in a wider patient population. These include stroke, paravalvular leak, valve durability, valve thrombosis, and need for pacemaker replacement. Ongoing clinical trials are expected to provide answers.

KEY POINTS

  • TAVR has become the preferred alternative to SAVR in inoperable and high-risk patients.
  • The US Food and Drug Administration has approved TAVR with open-heart surgery.
  • Initial outcomes support expanding TAVR to intermediate-risk patients, including mortality and stroke data, but concerns exist related to valve durability, valve thrombosis, and rates of permanent pacemaker implantation.

DOWNSIDE OF TAVR

Although results with TAVR appear promising, there are important issues to address before it can be adopted in a wider patient population (ie, low-risk patients). These primarily focus on the following:

  • Stroke
  • Paravalvular leak
  • Need for pacemaker replacement
  • Valve durability
  • Leaflet immobility or valve thrombosis.

Stroke

The incidence of stroke associated with TAVR is a concern, but it has decreased with the introduction of the Sapien 3 valve. In the PARTNER 2 trial, the 30-day stroke rate in intermediate-risk patients who received the Sapien 3 valve was 2.6%.1 This compares with a 5.6% overall rate in the PARTNER 1A trials using the first Sapien valve.2 The rate of stroke events is expected to decrease further as TAVR is expanded into healthier populations with better vasculature.

Paravalvular leak

Rates of moderate or severe paravalvular leak at 30 days have also decreased with the Sapien 3 valve and were 4.2% overall in the PARTNER S3i trial.6 These rates have ranged from 11.5% overall in the PARTNER 1A trial2 to 4.2% in the PARTNER 2B trial1 that used the Sapien XT valve for transfemoral-access TAVR.

New pacemakers

The percentage of TAVR procedures that result in a new requirement for a pacemaker increased to about 11% in 2014, up from 6.8% in 2012 to 2013.8 The requirement for a new pacemaker within 30 days following TAVR appeared to decrease again in the PARTER 2 trial, to 8.5%.1 

Durability

Evidence is emerging showing the limited durability of bioprosthetic aortic valve. Multiple studies have reportedly shown this, and this is true for all tissue valves, including those surgically inserted. A study assessing data from 357 patients showed that structural valve degeneration begins at 7 years post­operatively. By 10 years, only about 86% of valves were free from degeneration. At 12 years, that dropped to 69%.9

A study comparing TAVR vs SAVR showed that under identical loading conditions and with identical leaflet tissue properties, leaflets of valves placed via TAVR sustained higher stresses, strains, and fatigue damage.10

Overall, these results provide the possibility that TAVR valves may have reduced valve life compared with SAVR valves. Unknown durability may be an issue to consider when evaluating TAVR for implantation in intermediate- and low-risk patients.

Leaflet immobility and valve thrombosis

In the past 2 years, the problem of potential subclinical valve leaflet thrombosis, on both surgically inserted and TAVR valves, has emerged.11 The FDA is monitoring these complications because of their potential impact on the safety and efficacy of these valves.

This complication was first reported as an unexpected finding of reduced leaflet motion on 4-dimensional computed tomography, a sign suspicious for valve thrombosis, in a subgroup of patients evaluated 30 days after implantation.12 A study from Denmark found a 7% incidence of valve thrombosis in TAVR valves. They reported that warfarin could prevent thrombosis.13

At the Heart Hospital Baylor Plano, our TAVR team has identified approximately 50 cases of thrombosis that caused partial valve occlusion. Administering warfarin for 3 months resolved the thrombosis in virtually all cases. In 1 case, a thrombosed valve was surgically explanted with good patient outcome. Pathological analysis confirmed that reduced leaflet motion seen on 4-dimensional CT was valve thrombosis, as suspected by imaging specialists.14

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