Dr. Martin B. Leon agreed with Dr. Mohr that a definitive determination of whether TAVR is at least as good as SAVR in intermediate-risk patients must await results from the two major, ongoing multicenter trials testing this hypothesis, the PARTNER II trial, using the Edwards balloon-expandable SAPIEN XT valve system, and the SURTAVI (Safety and Efficacy Study of the Medtronic CoreValve System in the Treatment of Severe, Symptomatic Aortic Stenosis in Intermediate Risk Subjects Who Need Aortic Valve Replacement) trial. But Dr. Leon also cautioned that possible confounders might be distorting the GARY results, creating what he calls the "GARY Fallacy."
"The GARY Fallacy is the absurd notion that you can compare SAVR and TAVR in various risk strata without formal risk-adjustment methods to account for imbalances in baseline variables that are not captured in standard risk scores," he said in a talk at the meeting. "Aortic-stenosis patients were selected for TAVR based on their presumed increased risk, including many variables that are not represented in the risk algorithms, such as frailty, liver disease, porcelain aorta, a hostile chest, dementia, and severe chronic obstructive pulmonary disease. Therefore, the risk scores for TAVR patients underrepresent their true risk," Dr. Leon said.
But it’s also possible that TAVR needs more refinement before it completely catches up with SAVR, especially in patients who have the best outcomes from SAVR.
Mitchel L. Zoler/IMNG Medical Media
Dr. Martin B. Leon
"I think SAVR outperforms TAVR in low-risk patients in the German registry because SAVR is a more mature procedure," said Dr. Raj R. Makkar, a TAVR operator and director of interventional cardiology at Cedars-Sinai Medical Center in Los Angeles. "Maybe this will change, as TAVR becomes safer with fewer valve leaks, strokes, and vascular complications."
Assessing patient risks
Experts also realize that the EuroSCORE, the AKL score, and the other risk-stratification tools now available have flaws when applied to TAVR patients. "Risk stratification for TAVR and SAVR is very problematic; the EuroSCORE has shown poor predictive value for mortality," Dr. Leon said. And while the AKL score was developed specifically for SAVR patients, its relevance to TAVR patients is suspect. In the first PARTNER trial, the multivariate predictors of mortality in the TAVR patients were "completely different" from the predictors in the SAVR patients, he noted.
"It’s tricky calculating scores," agreed Dr. Makkar. Both he and Dr. Mohr cited comorbidities such as pulmonary hypertension, cirrhosis, knee replacement producing impaired mobility, and porcelain aorta that each ratchet up a patient’s risk but have no effect whatsoever on a patient’s EuroSCORE or STS score.
The German cardiology and cardiac surgery societies recognize the limitations of current risk-scoring formulas and are developing a risk-stratification tool specifically designed for TAVR patients, Dr. Mohr said.
The way patients are assessed before, during, and after TAVR is receiving careful scrutiny from some investigators who reported their findings at the ACC meeting, with a particular focus on efforts to characterize and minimize aortic-valve regurgitation following TAVR.
One report, for example, reviewed 2,679 patients who underwent TAVR at any of 33 French centers and 1 in Monaco between January 2010 and October 2011, and were enrolled in the French Aortic National CoreValve and Edwards (FRANCE 2) Registry, established by the French cardiology and thoracic and cardiovascular surgery societies (N. Engl. J. Med. 2012;366:1705-15). FRANCE 2 includes nearly 1,900 patients who received the balloon-expandable Edwards SAPIEN valve, and nearly 900 treated with the self-expanding Medtronic CoreValve device.
Following TAVR, 60% of all patients in the registry had paravalvular aortic regurgitation: 45% with grade 1 regurgitation, 14% with grade 2, and 1% with grade 3 or 4. In a multivariate analysis, the self-expandable device was linked to twice the rate of higher-grade aortic regurgitation, grade 2 or higher, compared with the balloon-expandable valve; and TAVRs done via the femoral artery approach were also about twice as likely to result in higher-grade regurgitations compared with other catheterization routes, reported Dr. Eric Van Belle, a professor at the Cardiology Hospital in Lille, France.
Postprocedural paravalvular regurgitation of grade 2 or higher "was associated with a twofold increase in 1-year mortality, and was the strongest independent predictor of mortality," said Dr. Van Belle in his talk at the meeting. In addition, "annulus diameter and prosthesis diameter were major determinants of aortic regurgitation" in patients who received a balloon-expandable valve.
The FRANCE 2 results showed that postprocedural aortic regurgitation at grade 2 or higher "is a major issue and should be avoided, especially when there is no significant aortic regurgitation at baseline, or when a nonfemoral delivery approach is used." The link between nonfemoral delivery approaches and lower rates of aortic regurgitation suggests "good control of the depth of device delivery and improved catheter technology are key to reducing regurgitation rates," Dr. Van Belle said. "In addition, the prosthesis diameter relative to annulus diameter is key to preventing regurgitation with balloon-expandable devices. Prevention of aortic regurgitation is a major challenge for developing the next-generation device technology."