SAN FRANCISCO, CALIF.—The Nov. 2 FDA approval of the first transcatheter aortic valve for replacing a native valve damaged by severe aortic stenosis marks an exciting time in the field of interventional cardiology, according to TCT Course Director Martin B. Leon, MD. However, it is important to step back and examine potential complications of this relatively new technique, he said during a plenary session at TCT 2011.
With regards to transcatheter aortic valve replacement (TAVR), Leon, of Columbia University Medical Center, said recent growth has been phenomenal. Estimates from Europe, for example, indicate that the number of TAVR procedures performed there in 2011 will exceed 17,500.
Yet, he acknowledged, this is “still in the beginning of a long process.”
Identifying clinical endpoints
Leon and colleagues initiated the Valve Academic Research Consortium, also known as VARC, to identify the most relevant clinical endpoints and endpoint definitions in response to what he called a tidal wave of uncontrolled TAVR clinical research.
He referenced new, never-before-presented data on outcomes after TAVR using VARC criteria. Phillipe Genereux, MD, also of Columbia University Medical Center, and Stuart Head, MD, of Erasmus University Medical Center, the Netherlands, reviewed the literature and completed a study-level meta-analysis of more than 3,500 patients from 17 studies. Most patients were older (mean age, 81 years) and female. Clinical outcomes, including all-cause and CV mortality at 30 days and 1 year, were reported (see Table).
“We are beginning to see associated events that occur during this procedure in the real world,” Leon said. “These are interesting new data using more validated definitions.”
Moving forward, validation of VARC definitions from ongoing clinical trials will help to uncover strengths and weaknesses of the current definitions and help inform future refinement efforts, he noted.
Complications of TAVR
Stroke definition and ascertainment are highly variable in surgical aortic valve replacement (AVR) and TAVR literature. Stroke frequency is increased after TAVR — about two to three times compared with AVR — and the difference is an early peaking hazard, and appears largely due to ischemic embolic events, Leon said. Transcranial Doppler studies suggest that native valve manipulation may be an important contributor to early stroke. Cerebral embolic protection and increased pharmacotherapy are currently under investigation. Although there is much to learn about stroke and TAVR, Leon said it is not an unmanageable complication.
Vascular complications after TAVR, including hematomas, dissections and perforations, are frequent and have been associated with increased mortality. Vessel-sheath size ratio, calcification and center experience appear to be important predictors. Meticulous CTA screening, site/operator experience, reduced caliber devices and dedicated access site closure systems will improve future outcomes, he said.
Paravalvular leak after TAVR occurs frequently in up to 80% of patients, according to Leon. However, definitions and grading of paravalvular severity remain inconsistent and problematic, he said. Causes and predictors of paravalvular leak are multifactorial, and may include optimal valve sizing, calcification and valve position. Operator experience and post-dilatation have been associated with reduced paravalvular leak. Significant paravalvular leak has been a predictor of subsequent mortality, although observation is limited. New TAVR designs may reduce paravalvular leak in the future.
According to Leon, the need for permanent pacemakers after TAVR is an important complication that requires more intense and prolonged in-patient monitoring and exposes patients to lifelong hazards. The threshold for needing a permanent pacemaker after TAVR is extremely variable and better guidelines are required. In the future, improved implantation techniques and modified TAVR systems will reduce the rates of permanent pacemakers after TAVR to levels similar to surgical AVR, he said.
Short- and mid-term TAVR system durability appears encouraging, with infrequent endocarditis, maintained hemodynamic performance and no other signs of structural valve deterioration. However, several caveats exist, including a lack of long-term data and unknown “imponderables” such as late effects on coronary arteries and the mitral valve.
“I don’t think these complications are going to be the Achilles’ heel. I think they will be manageable in the future with time and understanding and a variety of changes in the devices and operator techniques,” Leon concluded. “We should proceed, but with caution.