Outcomes of one of the largest clinical trials comparing transcatheter aortic valve implantation (TAVI) to open heart surgery aortic valve replacement (AVR) were published. Non-inferiority of the TAVI procedure has been demonstrated for mortality and overall clinical outcomes (1).

The PARTNER Trial is a multicentre, prospective randomised clinical trial on 699 randomised high – risk patients (2). At two years, clinical outcomes and echocardiographic imaging have been assessed (1). Overall mortality at 2 years was not dissimilar between groups with 33.9% for TAVI and 35.0% for AVR group (p=0.78) (Kaplan-Meier analysis) (1). Stroke rates did not differ between the groups at 2 years (7.7% vs 4.9%, p=0.17) as opposed to a 1 year results which showed higher major stroke rates for TAVI group (5.1% vs 2.4%, p=0.07) (2). The results have also demonstrated increased rate of paravalvular regurgitation after TAVI (p<0.001) (1). This finding has been linked to an increased risk of late mortality (p<0.001) (1). This update follow up on the clinical outcomes gives evidence for feasibility of TAVI at 2 years.

At present majority of the aortic valve replacements are performed using a gold standard open heart surgery. Rapid technological revolution in recent years enabled development of endovascular approach. Initial clinical use raise concerns regarding complication rates in TAVI, with a high embolisation rates and up to 10% stroke rates being reported (3). No long term outcomes are known and the recent publication of a 2 year follow up adds a great value to the evidence available on that matter.

TAVI is recommended by the National Institute for Clinical Excellence (NICE) guidelines for patients with stenosis of >0.6 cm2, mean transaortic valve gradient >40 mmHg (peak >65 mmHg) and otherwise assessed as not fit for surgery due to other co-morbidities (4). What is interesting, recent trend to perform TAVI on patients with a better functional status has been reported, indicating possible shift towards adoption of TAVI for operable patients as well (5).

Further development of the technology with better instruments, overcoming learning curve and improved visualisation methods may further improve TAVI approach. Future development will inevitably bring further improvements in TAVI procedure. Risk of embolisation and stroke needs to be further reassessed. Reduction of embolisation during TAVI procedure could be of a great value, improving clinical outcomes. Technical adaptation of equipment and grafts used during TAVI is a one possible method of reducing embolisation risk (6,7). Use of endovascular protection devices may also be feasible (8). Improvement in imaging and navigation systems could also enable more accurate positioning of the instruments, translating into better clinical outcomes. Real time cardiovascular magnetic resonance (rtCMR) and electromagnetic 3D navigation system are examples of the new imaging technology under development (9,10). New challenges will be realised as further data on long term outcomes gets published. Follow up on PARTNER Trial exposed a problem of paravalvular regurgitation (1). This data will hopefully lead to a reassessment of the technical aspects of the procedure and further improvements in grafts, limiting regurgitation in a long term.

TAVI is internationally accepted as an alternative to open surgery in inoperable cases of sever aortic stenosis and it is to stay as a mainstream intervention for those patients. Further data on a long term outcomes in terms of complications rate and quality of life will provide evidence for evaluation of the approach for lower surgical risk patients.

Author: Radoslaw A Rippel

Conflict of interest: none

References
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(2) Smith CR, Leon MB, Mack MJ, Miller DC, Moses JW, Svensson LG, et al. Transcatheter versus surgical aortic-valve replacement in high-risk patients. N Engl J Med 2011 Jun 9;364(23):2187-2198.
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(4) National Institute for Health and Clinical Excellence (NICE). Interventional Procedures Programme; Interventional procedure overview of transcatheter aortic valve implantation for aortic stenosis. April 2011.
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(6) Omran H, Schmidt H, Hackenbroch M, Illien S, Bernhardt P, von der Recke G, et al. Silent and apparent cerebral embolism after retrograde catheterisation of the aortic valve in valvular stenosis: a prospective, randomised study. Lancet 2003 Apr 12;361(9365):1241-1246.
(7) Rodes-Cabau J, Dumont E, Boone RH, Larose E, Bagur R, Gurvitch R, et al. Cerebral embolism following transcatheter aortic valve implantation: comparison of transfemoral and transapical approaches. J Am Coll Cardiol 2011 Jan 4;57(1):18-28.
(8) Naber CK, Ghanem A, Abizaid AA, Wolf A, Sinning JM, Werner N, et al. First-in-man use of a novel embolic protection device for patients undergoing transcatheter aortic valve implantation. EuroIntervention 2012 May 15;8(1):43-50.
(9) Kahlert P, Parohl N, Albert J, Schafer L, Reinhardt R, Kaiser GM, et al. Towards real-time cardiovascular magnetic resonance guided transarterial CoreValve implantation: in vivo evaluation in swine. J Cardiovasc Magn Reson 2012 Mar 27;14:21.
(10) Sidhu R, Weir-McCall J, Cochennec F, Riga C, DiMarco A, Bicknell CD. Evaluation of an electromagnetic 3D navigation system to facilitate endovascular tasks: a feasibility study. Eur J Vasc Endovasc Surg 2012 Jan;43(1):22-29.

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