Should TAVI be extended to lower risk patients?
The relatively new procedure for aortic valve replacement, namely Transcatheter Aortic Valve Implantation (TAVI), first performed in 2002, is considered to be an appropriate approach when conventional surgical aortic valve replacement (SAVR) for severe aortic stenosis is contraindicated because patients have left ventricular dysfunction or are very elderly with comorbidities. During the procedure a catheter with a balloon at its tip loaded with a new tissue valve is inserted into a femoral artery and is passed to the opening of the aortic valve where the inflation of the balloon allows the new valve to be positioned and expanded prior to the removal of the catheter and deflated balloon. Trials including two year follow ups comparing TAVI with conservative treatment in high risk, inoperable patients all show that the procedure is associated with higher survival time. However recent results also suggest that TAVI may be superior to SAVR in intermediate risk patients. So should TAVI be extended to intermediate and even low risk, younger patients or is this inadvisable?
Earlier data have shown that significantly more patients suffered from stroke after TAVI compared with patients undergoing SAVR, as the former procedure tended to produce debris from the degenerated aortic valve and aorta. Paravalvular leaks have also been reported more frequently after TAVI, impacting on patient survival time. There is also a reported higher incidence in conduction abnormalities after the procedure, often occurring because of too deep implantation of the new valve; in such cases it becomes necessary to implant a pacemaker. Less common complications have included arterial dissection and perforation, myocardial ischemia and cardiogenic shock. However, during the decade since TAVI became the standard of care for inoperable patients with severe aortic stenosis, three major factors have contributed to the substantially lowered risk of complications following the procedure. Firstly preoperative assessment has benefitted from the many recent advances in cardiac diagnostic imaging. Secondly both valve delivery systems and valves have evolved, with the better controlled positioning of more compact, newer generation valves, preceded by pre-implantation site preparation, all allowing superior annular sealing and appropriate valve expansion without causing significant tissue trauma. Last but not least, surgical teams have now acquired a wealth of experience in performing the procedure. The results of randomized trials could well demonstrate that TAVI has even become a prudent therapy choice for younger patients with a low perioperative risk.