Balloon Aortic Valvuloplasty in the Transcatheter Aortic Valve Replacement Era: A “Die-Hard” Procedure

Percutaneous balloon aortic valvotomy (also known as balloon aortic valvuloplasty [BAV]) was first described in 1984 by Lababidi and Neuhaus1Lababidi Z Wu JR Walls JT Percutaneous balloon aortic valvuloplasty: results in 23 patients.Am J Cardiol. 1984; 53 (doi: 10.1016/0002-9149(84)90709-4): 194-197Google Scholar and was reported for the treatment of congenital aortic stenosis (AS) in children and young adults. In 1986 Cribier was the first to perform BAV in adults with calcific AS.2Cribier A Sasin T Saondi N et al.Percutaneous transluminal valvuloplasty of acquired aortic stenosis in elderly patients: an alternative of valve replacement?.Lancet. 1986; 1 (doi: 10.1016/S0140-6736(86)90716-6): 63-67Google Scholar In this setting the procedure was so successful that it led to the birth of registries for the analysis of the results.3Otto CM Mickel MC Kennedy JW et al.Three-year outcome after balloon aortic valvuloplasty. Insights into prognosis of valvular aortic stenosis.Circulation. 1994; 89 (doi: 10.1161/01. CIR. 89.2.642): 642-650Google Scholar,4NHLB Balloon Registry ParticipantsPercutanous balloon aortic valvuloplasty. Acute and 30-day follow-up results in 674 patients from the NHLBI Balloon Valvuloplasty Registry.Circulation. 1991; 84 (doi: 10.1161/01. CIR. 84.6.2383): 2383-2387Google Scholar Aortic valvuloplasty turned out to be a simple and reproducible procedure, but with a high recurrence of early restenosis, and with a very limited effect on survival and disease progression.3Otto CM Mickel MC Kennedy JW et al.Three-year outcome after balloon aortic valvuloplasty. Insights into prognosis of valvular aortic stenosis.Circulation. 1994; 89 (doi: 10.1161/01. CIR. 89.2.642): 642-650Google Scholar,4NHLB Balloon Registry ParticipantsPercutanous balloon aortic valvuloplasty. Acute and 30-day follow-up results in 674 patients from the NHLBI Balloon Valvuloplasty Registry.Circulation. 1991; 84 (doi: 10.1161/01. CIR. 84.6.2383): 2383-2387Google Scholar Therefore, this procedure was selectively used as a palliative remedy, in cases of patients with severe AS with no surgical alternatives.5Nishimura RA Otto CM Bonow RO et al.AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.Circulation. 2017; 2017 (doi: 10.1161/CIR.0000000000000503): e1159-e1195Google Scholar The introduction of transcatheter aortic valve replacement (TAVR) and its global adoption by a growing number of centers worldwide6Barbanti M Webb JG Gilard M Capodanno D Tamburino T Transcatheter aortic valve implantation in 2017: state of the art.Eurointervention. 2017; 13: AA11-AA21Google Scholar has produced two scenarios that are conceptually opposite: on one hand, it has renewed the interest in BAV procedures, mostly due to the willingness of operators to familiarize themselves with materials and techniques that would be useful later for TAVR procedures; on the other hand, TAVR has further reduced the indications of BAV to very compromised patients with poor life expectancy.5Nishimura RA Otto CM Bonow RO et al.AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.Circulation. 2017; 2017 (doi: 10.1161/CIR.0000000000000503): e1159-e1195Google Scholar Furthermore, BAV has also been proposed as a “bridge procedure,” to determine the therapeutic response of a reduction in aortic gradient in borderline patients, to assess symptomatic and hemodynamic improvement prior to consideration of definitive TAVR or surgical intervention.7Ussia GP Capodanno D Barbanti M et al.Balloon aortic valvuloplasty for severe aortic stenosis as a bridge to high-risk transcatheter aortic valve implantation.J Invasive Cardiol. 2010; 22: 394-399Google Scholar Over the last years, several valvuloplasty devices have become available with different features: Basically, there exist semi-compliant or non-compliant aortic balloons. Semi-compliant balloons usually have a lower profile and therefore require smaller vascular access sheaths, which can help in reducing vascular complications in elderly and very high-risk patients. The drawback, however, is that they have less predictable inflation diameters than the non-compliant balloons and have lower-rated burst pressures.8Keeble TR Khokhar A Akhtar MM et al.Percutaneous balloon aortic valvuloplasty in the era of transcatheter aortic valve implantation: a narrative review.Open Heart. 2016; 3 (doi: 10.1136/openhrt-2016-000421): e000421Google Scholar In this issue of Structural Heart, Htun and colleagues report the first-in-human study of a novel AngioSculpt valvuloplasty scoring balloon catheter (Spectranetics Corporation, Colorado, USA) for the treatment of severe calcific aortic valve stenosis.9Htun NM Perlman GY Dvir D et al.A novel valvuloplasty scoring balloon catheter for aortic stenosis.Structural Heart. 2017; 1Google Scholar The investigators enrolled 25 very elderly (mean age 83.6 ± 5.8 years) consecutive patients treated in two Canadian centers during a timeframe of 25 months. Although this device has been demonstrated to be fairly safe, with no cases reported of severe aortic regurgitation, in-hospital death, stroke or emergency cardiac surgery, the primary efficacy endpoint (defined as a > 50% increase in the aortic valve effective orifice area or a ≥ 30% decrease in the mean aortic valve gradient and ≤ 2+ valvular regurgitation post-BAV) was only met in one third of the patients, with an average of ~6 mmHg reduction of transaortic gradient at discharge. This value is less than these reported by previous series using convectional aortic valvuloplasty balloons.8Keeble TR Khokhar A Akhtar MM et al.Percutaneous balloon aortic valvuloplasty in the era of transcatheter aortic valve implantation: a narrative review.Open Heart. 2016; 3 (doi: 10.1136/openhrt-2016-000421): e000421Google Scholar Unfortunately, a high proportion of patients left the study before the final follow-up, thus making it impossible to assess even the mid-term efficacy of BAV using this novel device. Also, it is not possible to draw a meaningful conclusion on the change in New York Heart Association (NYHA) functional class due to the small sample size and a high rate of early study exit. The reasons for such somewhat disappointing results can be several: the first regards the methodology of the study, which encompasses a very small cohort of patients with poor adherence to the study protocol. The second probably stands in the mechanism of function of this device: The AngioSculpt valvuloplasty scoring balloon catheter incorporates a semi-compliant balloon with an attached nitinol spiral cage (scoring element). The scoring element has 12 spiral struts and four cross-linking stabilizing rings that wrap around the balloon. Theoretically, these struts should create focal amplification of the forces exerted by the valvuloplasty balloon along the edges of the scoring element. As for other valvuloplasty balloons, the predominant mechanism of dilatation of the AngioSculp balloon is the fracture of calcified nodules, the separation of fused commissures in rheumatic valve disease, and microfractures along stromal cleavage planes10Safian RD Mandell VS Thurer RE et al.Post-mortem and intra-operative balloon valvuloplasty of calcific aortic stenosis in elderly patients: mechanism of successful dilatation.J Am Coll Cardiol. 1987; 9 (doi: 10.1016/S0735-1097(87)80061-X): 665-670Google Scholar; restenosis has been correlated, instead, to remodeling with fibrotic scarring of the fissures created by the balloon on calcified nodules, to a mechanism of heterotopic ossification and to the elastic rebound of the previously dilated aortic annulus.10Safian RD Mandell VS Thurer RE et al.Post-mortem and intra-operative balloon valvuloplasty of calcific aortic stenosis in elderly patients: mechanism of successful dilatation.J Am Coll Cardiol. 1987; 9 (doi: 10.1016/S0735-1097(87)80061-X): 665-670Google Scholar According to the observations made by Htun and coworkers, a clinically significant and lasting reduction of the transaortic gradient probably cannot be obtained by only increasing the forces exerted by the scoring valvuloplasty balloon. The investigators used the most accurate strategies for choosing the correct balloon diameter (transesophageal echocardiography or computed tomography angiography), thus assuming that sub-optimal balloon sizing was not responsible for this minor effect on the post-procedure aortic gradients. It is also hard to tell if different valvuloplasty techniques (additional and more prolonged inflations) may translate in more favorable outcomes; for sure these can increase the risk of developing valve rupture and significant aortic regurgitation. In conclusion, Htun and colleagues should be congratulated for exploring new solutions for a technique that also in the future will maintain its niche in the management of very complex populations affected by severe AS. This first-in-human study demonstrates only the feasibility of BAV using the AngioSculpt valvuloplasty scoring balloon catheter; however, larger and more accurate analyses should assess the real efficacy of this new technology in comparison with standard balloons. Marco Barbanti is a consultant for Edwards Lifesciences.

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