Study Looks at First In-Human Use of Self-Expanding and Repositioning Transcatheter Heart Valve
Transcatheter aortic valve replacement (TAVR) is an innovative new therapy for treating patients with severe aortic stenosis. However, due to the newness of the treatment, continued research is necessary in order to ensure appropriate and effective use.
"The transformational technology of TAVR continues to transform itself with new data, new approaches and new technology," says ACC Immediate Past President David Holmes, Jr., MD, MACC. "This field represents a significant part of the future of interventional cardiovascular disease as the surgeons and cardiologists alike work together to provide the right approach to the right patient at the right time."
One of the challenges associated with TAVR to date is that suboptimal prosthesis positioning can contribute to paravalvular regurgitation, atrioventricular conduction block, and mitral or coronary compromise. To address this, St. Jude Medical in Minnesota developed a self-expanding and repositionable transcatheter heart valve.
A study published on July 16 in the Journal of the American College of Cardiology provides the first in-human look at the feasibility and procedural outcomes using this new repositionable Portico valve. The device, which was implanted in 10 patients with severe aortic stenosis utilizing percutaneous femoral arterial access, was deployed successfully in all patients with no major periprocedural complications. In addition, all patients in this high-risk cohort remained alive at 30 days with a marked improvement in functional class.
All patients underwent transthoracic and transesophageal echocardiography and multidetector computed tomography before and after valve implantation. Clinical and echocardiographic follow-up was also obtained at 30 days. The study authors note, that while this was a small series and follow-up remains limited, "the clinical and echocardiographic outcomes are encouraging." They suggest that further evaluation is warranted.
Frequent vascular complications after transfemoral (TF) TAVR are another issue being explored. Data from the PARTNER trial released on Aug. 5 in JACC found that major vascular complications are frequent after TF-TAVR when first-generation devices are used. Of the 419 patients studied, 64 (15.3 percent) had major vascular complications and 50 (11.9 percent) had minor vascular complications within 30 days of the procedure. The study authors noted that among patients with major complications, vascular dissection (62.8 percent), perforation (31.3 percent), and access-site hematoma (22.9 percent) were the most frequent. Major complications were also associated with significantly higher 30-day rates of major bleeding, transfusions, and renal failure requiring dialysis, and with a significantly higher rate of 30-day and one-year mortality. The only identifiable independent predictor of major vascular complications was female gender (hazard ratio [HR]: 2.31 [95 percent confidence interval (CI): 1.08 to 4.98], p 0.03). Major vascular complications, as well as renal disease at baseline, were also identified as independent predictors of one-year mortality.
"These findings underline the magnitude of impact and the synergy between enhanced operator skills, TAVR team experience, and device improvement," the study authors said. "These three factors are vital if the full clinical potential of the TAVR procedure is to be realized, especially when involving a lower-risk population."
Another challenge identified by recent studies is that TAVR can induce cardiac conduction abnormalities; the most frequent being left bundle branch block (LBBB). The incidence of TAVR-induced LBBB has been reported to vary between 7 percent and 83 percent. A new study published last month in Circulation investigated the impact of LBBB after TAVR on all-cause mortality in 679 patients who underwent TAVR between November 2005 and December 2010 in eight centers in the Netherlands.
Data from the study found that all-cause mortality is significantly higher in TAVR patients who developed LBBB as compared with TAVR patients who did not. "Previous TAVR-related studies have registered LBBB as a complication, but did not mention its possible clinical relevance, because little is known about the impact of LBBB in the setting of valvular heart disease," the study authors write. "However, multivariate analysis of our data indicate that TAVR-induced LBBB is an independent and important risk factor for all-cause mortality after TAVR. Although it is not possible to completely exclude that LBBB is a surrogate for another baseline or procedural characteristic, we think that our data strongly indicate that TAVR-induced LBBB itself is a risk factor for mortality."
The study also corroborates data from other studies, demonstrating that the incidence of TAVR-induced LBBB varies by devices. According to the study authors, the frequency of LBBB was higher for the Medtronic CoreValve System (MCS) as compared to the Edwards SAPIEN (ES) valve. After MCS implantation, a new LBBB occurred in 198 out of 387 patients (51.1 percent), as opposed to 35 out of 292 patients (12.0 percent) who had been implanted with an ES valve (P<0.001). "Our observation that TAVI-induced LBBB increases risk of mortality combined with a more than four times higher incidence of LBBB and PPM implantation in MCS implants, should be taken into consideration in making the choice between currently available devices and obtaining informed consent of the patient," the authors note.
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