TAVR enters a new risk-scoring era

In the 14 years since the first transcatheter aortic valve replacement in 2002, devices and delivery methods have undergone several generations of improvement, but one facet of the procedure remained largely unchanged: When prospective patients underwent preprocedural assessment to gauge their risk level, the long-standing approach to quantify their disease severity and 30-day mortality risk was to run their clinical and demographic numbers through the risk calculator developed by the Society of Thoracic Surgeons.

Although determining a patient’s Society of Thoracic Surgeons (STS) risk score using a formula based on extensive experience performing surgical aortic valve replacement (SAVR) by open surgery made a lot of sense during an era when the preeminent question was how transcatheter aortic valve replacement (TAVR) compared with SAVR, it also carried the inherent limitation of estimating a patient’s risk when undergoing TAVR based on SAVR’s track record.

That limitation is now gone.

In December 2015, a team of cardiothoracic surgeons and interventional cardiologists assembled by the STS and the American College of Cardiology placed a new risk calculator online to estimate a prospective TAVR patient’s risk for dying in hospital following a TAVR procedure. The panel developed this risk calculator with data from nearly 14,000 U.S. TAVR patients enrolled in the STS/ACC Transcatheter Valve Replacement Registry during November 2011–February 2014 and then validated it with data from another nearly 7,000 U.S. TAVR patients who underwent their procedure during March-October 2014. This created the first mortality-risk calculator for TAVR patients based entirely on experience with such patients (JAMA Cardiology. 2016 Apr;1[1]:46-52).

In May 2016, a second, independent risk calculator will go live, also based exclusively on experience in TAVR patients, that estimates a patient’s risk for either dying or having a worsened or unimproved and poor quality of life during the 6 months following TAVR. This risk calculator, developed by a team led by researchers based at Saint Luke’s Mid America Heart Institute in Kansas City, Mo., used data collected from more than 2,000 TAVR patients enrolled in the PARTNER trial or in the continued-access PARTNER registry (Circulation. 2014 June 24;129[25]:2682-90), and is offered to users by Health Outcomes Sciences, a Kansas City–based company that’s affiliated with Saint Luke’s.

Although use of these two TAVR-specific risk calculators during their early days of availability remains relatively light, TAVR experts see them as marking a new era in the workup of TAVR candidates.

Dr. Fred H. Edwards

“There is universal agreement that risk models must be developed based on the history of patients who actually received the treatment,” said Dr. Fred H. Edwards, the cardiothoracic surgeon at the University of Florida, Jacksonville, who led the team that developed the transcatheter valve therapy (TVT)-derived in-hospital mortality risk calculator. “Everyone realized that the STS score and the EuroScore [another operative-risk calculator historically used for prospective TAVR patients] were inadequate to extrapolate to TAVR patients.” But development had to wait until an adequately-sized experience with TAVR had accumulated. “We started the process [to develop the TVT risk calculator] when we reached about 10,000 patients” enrolled in the registry, after which it took “close to 2 years” to produce the finished product, Dr. Edwards said in an interview.

The TVT in-hospital mortality predictor gradually goes mainstream

“There is consensus that the new TVT calculator will be more reliable than the STS operative-risk model” for assessing patients being considered for TAVR, but it has not yet gained widespread use “because it is so new,” noted Dr. Edwards.

“It will take a while to incorporate it into routine practice, but I think it will be used quite a bit,” especially for “trickier and harder cases,” commented Dr. George Dangas, a professor of medicine at the Mount Sinai School of Medicine in New York and an interventional cardiologist who performs TAVR.

Dr. George Dangas

He also predicted that prospective patients and their families will become frequent users of the TVT in-hospital risk calculator. He sees the new risk tool as a complement to the STS risk score rather than something to replace it.

“Patients find it useful to receive an estimate of their surgical risk, and they’ll want to compare that” with their TAVR risk. “It helps to know both,” Dr. Dangas said in an interview. “Patients will likely compute it themselves.”

He foresees fairly quick integration of the new TVT score into heart team discussions as well. “The STS score will always be part of the discussion, but over time as people grow accustomed to the TVT score they will incorporate it as well. The [TAVR] community has to figure out how to use the two scores in combination.”