Minimizing aortic regurgitation
Two ways to cut aortic regurgitation rates following TAVR are to better match the valve to the annulus size, and when possible not finish a TAVR procedure until regurgitation has been minimized.
Two-dimensional transthoracic echocardiography had been the standard approach for annulus sizing as recently as 3 years ago, but it has been replaced with more accurate approaches, either three-dimensional transthoracic echo or CT. "Two-dimensional measurements are seriously limited due to variations and noncircular annular anatomy," Dr. Makkar said in a talk at the meeting. "CT provides the best overall assessment, because in addition to the cross-sectional measurement of the annulus it provides the best assessment of calcification," and three-dimensional transthoracic echo is now standard for intraprocedural assessments, he said.
The impact that a concerted effort to minimize aortic regurgitation can have on outcomes was examined in a single-center study reported by Dr. Jan-Malte Sinning, a cardiologist at University Hospital in Bonn, Germany. Last year, Dr. Sinning and his associates reported developing a quantitative measure of aortic regurgitation immediately following TAVR, the aortic regurgitation (AR) index, based on the difference between a patient’s diastolic blood pressure in the aorta and the left ventricular end-diastolic pressure (J. Am. Coll. Cardiol. 2012;59:1134-41). They then calculated the AR index immediately after TAVR in a prospective series of 167 patients, and set themselves the goal of immediately taking whatever steps were needed to bring the AR index above 25, a cutoff that seemed to correspond to no worse than mild regurgitation.
In their series, 62 patients underwent immediate post-TAVR corrective steps to reduce aortic regurgitation and bring their AR index above 25, most commonly additional balloon dilatation of the valve. The result was that while 16 patients had severe regurgitation before these steps, no patient had severe regurgitation following the corrective measures. The adjustments also cut the incidence of moderate regurgitations from 41 patients to 10, Dr. Sinning reported.
The consequence was that the 30-day stroke rate in the new cohort was 1%, compared with a 6% rate in a historical TAVR cohort at University Hospital in Bonn. The need for pacemaker implants was also cut in half by the intervention compared with the historical group, and 30-day mortality was 3% with these interventions, compared with 7% in the historical controls.
The results suggest that using the AR index as a trigger for taking corrective measures can help improve survival, and that post-TAVR dilatation can successfully decrease regurgitation without increasing patients’ stroke risk, Dr. Sinning concluded.
U.S. operators who perform TAVR say they take similar steps these days to deal with aortic regurgitation after TAVR. "We all understand that you don’t want patients to leave with a leak," said Dr. Popma. "We do everything we can to minimize leaks. When a patient leaves the lab with a moderate or severe leak, there wasn’t anything we could do about it."
Finding TAVR’s limits
Even as TAVR has become the go-to method for high-risk patients, operators have also tried to define the procedure’s outer limit, the point of disease severity when a patient is dying with aortic stenosis rather than because of aortic stenosis, and performing TAVR doesn’t make sense.
Dr. Makkar analyzed 369 inoperable patients who underwent TAVR in both the PARTNER I trial and the nonrandomized continued-access phase that followed. The patients fell into three groups: those who were inoperable because of technical reasons, such as a porcelain aorta or prior chest irradiation; patients who were inoperable because of comorbidities, such as frailty or severe lung disease; and those with both limitations. The 85 patients who were inoperable only because of a technical limitation had a 2-year mortality rate of 23% following TAVR; the other 284 patients who all had comorbidities had a 2-year mortality rate of about 43%.
Last year, Dr. Makkar reported that analysis of these 369 inoperable patients showed a 2-year mortality rate of 20% in the subgroup with an STS score of less than 5%, a mortality rate of 40% among those with a score of 5%-14.5% (but still significantly below the 60% 2-year mortality among similar inoperable patients managed by standard medical therapy only), and a 60% mortality rate among patients with a baseline STS score of 15% or more, an outcome that was no better than that of patients managed without TAVR (N. Engl. J. Med. 2012;366:1696-704).
In a multivariate analysis he recently ran on the data from these 369 patients, the likelihood of 2-year mortality rose by a statistically significant 3% for every 1% increase in the patient’s baseline STS risk score.