Portico Valve

Transcatheter aortic valve replacement (TAVR) has extended the therapeutic options for successful management of selected patients with severe aortic stenosis. To date, two different transcatheter heart valves (THVs), the balloon-expandable Sapien valve (Edwards Lifesciences, Irvine, CA) and the self-expandable CoreValve device (Medtronic, Inc., Minneapolis, MN), have been widely used with extensive data on feasibility, safety, and clinical outcomes.¹ However, new generations of THVs are emerging with several potential advantages that may improve upon the limitations of current systems. This article describes the self-expanding, repositionable Portico THV (St. Jude Medical, Inc., St. Paul, MN) and the possible implications it may have on the future of TAVR.

CHARACTERISTICS OF THE PORTICO VALVE AND DELIVERY SYSTEM

The Portico valve is a self-expandable prosthesis that consists of a trifoliate bovine pericardial valve and a porcine pericardial sealing cuff attached to a nitinol frame (Figure 1). The leaflet/cuff position (very low in the nitinol frame) is designed to allow both minimal protrusion of the stent frame into the left ventricular outflow tract and functioning valve leaflets once the valve has been partially deployed. The bovine leaflets and sealing cuff are treated with Linx anticalcification technology (St. Jude Medical, Inc.). The outflow portion of the self-expanding stent frame has three retention tabs to secure the crimped valve to the delivery system. The delivery system allows for full resheathing and repositioning prior to complete valve deployment, which is potentially one of the most important advantages of this THV. Larger cells in the stent frame are designed for easier access to the coronary ostia at the aortic level and tissue adaptation to calcific nodules to ensure effective sealing of the paravalvular space (Figure 1). The current available size is 23 mm (nominal external stent diameter at the leaflet level), and additional valve sizes of 25, 27, and 29 mm are anticipated (Figure 2A).

The transfemoral delivery system (Figure 2B) consists of a soft tapered nose cone, an 18-F (outer diameter) capsule that contains the crimped valve, and a 12-F shaft (Figure 2C). The handle incorporates a system to unsheath, resheath, reposition, and release the valve with a rotating thumbwheel (Figure 2D). The ability to resheath and reposition the valve may be helpful in reducing the risk of valve malpositioning or embolization, significant paravalvular regurgitation, coronary obstruction, interference of the mitral valve apparatus, and atrioventricular block.

The Portico valve is expected to be available for the transapical approach as well. The transapical delivery system, anticipated in a 24-F (outer diameter) size, is also designed for initial expansion of the nitinol frame at the aortic annulus level to allow functioning leaflets during the deployment process.

TRANSFEMORAL THV IMPLANTATION PROCESS

Following aortic balloon valvuloplasty, the valve implantation process commences with the advancement of the sheathed valve delivery catheter system into the left ventricle. The distal edge of the valve is positioned 1 to 6 mm below the native aortic valve leaflets. Rotating the thumbwheel unsheaths the inflow of the THV, after which, further rotation of the thumbwheel deploys the annular portion containing the bioprosthesis leaflets (Figure 3). A radiopaque marker in the delivery system guides the operator to align the annular portion at the level of the native aortic leaflets. Rapid pacing is not required for this maneuver. At this time, when the stent is partially unsheathed, the leaflets of the bioprosthesis are functional, avoiding hemodynamic instability during the final adjustment and positioning process (Figure 3). The retention tabs are still secured within the capsule that is attached to the delivery system. The position of the THV can be assessed at this time, and if the position is not satisfactory, THV repositioning can be accomplished by retraction of the delivery system.

Alternatively, and preferably, rotating the thumbwheel in a reverse direction allows the THV to be partially or completely resheathed. After recapture, the THV can be redeployed or removed. Preclinical testing by the manufacturer documented that the THV could be reliably resheathed and redeployed once. The safety of repeated resheathing is unknown. When a satisfactory position is achieved, the thumbwheel is fully rotated to release the outflow portion and the retention tabs.

FIRST-IN-HUMAN EXPERIENCE

To date, two clinical studies with the 23-mm Portico valve have been carried out in Canada (two centers) and Ireland (one center). The Canadian study² at two centers (St. Paul's Hospital, Vancouver, British Columbia, and the Quebec Heart and Lung Institute, Quebec City, Quebec) included 10 patients (all women; mean age, 82 ± 6 years) with a Society of Thoracic Surgeons (STS) score of 8.1% ± 3.2%. Baseline characteristics of the study population are shown in Table 1. The mean aortic annulus was measured at 19.4 ± 1.6 mm by transesophageal echocardiography (TEE) and 20.6 ± 1.7 mm by computed tomography. The procedures were performed under general anesthesia and with fluoroscopic/angiographic and TEE guidance.

Prosthetic valve delivery via the transfemoral approach, implantation, and removal of the delivery system was successful in all cases. Initial positioning of the expanded valve was suboptimal in four patients (40%), and recapture and repositioning was easily accomplished without removing the system from the aortic root. No complications concerning the recapturing and repositioning of the valve were noted. Thirty-day outcomes are shown in Table 2. No deaths, myocardial infarctions, major strokes, major vascular complications, or major/minor bleeding incidents occurred. One minor stroke (10%) and one minor vascular complication (10%) were registered. Pacemaker implantation was not required in any patient, but two patients developed a new left bundle branch block after valve deployment.

The transaortic gradient decreased from 45 ± 17 mm Hg to 10.7 ± 4.5 mm Hg (P < .001), and the aortic valve area increased from 0.6 ± 0.1 cm² to 1.4 ± 0.2 cm² (P < .001). Paravalvular regurgitation at hospital discharge was none/ trace in four patients (40%), mild in five (50%), and moderate in one (10%). At 30 days, all patients were alive with a New York Heart Association (NYHA) class I and II in six (60%) and four (40%) patients, respectively. Improvements in hemodynamic valve performance were sustained at 30-day follow-up, and paravalvular regurgitation remained stable, except in one patient who improved from mild to trace. Computed tomography was performed prior to hospital discharge in all patients (Figure 4). Eccentricity of the THV was maximal at the inflow (12.8% ± 6.1%) and valvular level (12% ± 7.3%) and minimal at the outflow (2.4% ± 1.2%). Expansion of the stent at inflow and the valvular level was 88% compared to 65% at the outflow (Figure 4C). The single-center UK experience3 (Royal Victoria Hospital, Belfast, Ireland) consisted of 10 patients (all women; mean age, 86 ± 3 years) with an STS score of 6.5% ± 2.4% (Table 3). The procedures were performed with sedation and local anesthesia, with fluoroscopic/angiographic guidance only (no TEE). Valve implantation was successful in all patients. Valve resheathing was performed in two patients without complications. Outcomes at 1- and 6-month follow-up are shown in Table 4. Study results showed no device- or procedure-related adverse events or deaths. Four patients developed a new left bundle branch block. The mean gradient decreased from 40.7 mm Hg to 7.8 mm Hg, and the aortic valve area increased from 0.7 cm² to 1.5 cm². These improvements were sustained at 6-month follow-up.

Postprocedure paravalvular aortic regurgitation was only mild or less in all cases, and there was no evidence of progression at follow-up. Significant improvements in NYHA functional class and exercise performance, as evaluated with a 6-minute walk test, were observed at 1- and 6-month follow-up.

In summary, the first-in-human Canadian and European experiences showed that the implantation of the new Portico valve for the treatment of patients with severe, symptomatic aortic stenosis was feasible. Also, the procedure is associated with a low rate of complications and excellent short-term clinical outcomes and valve hemodynamics. These initial results will have to be confirmed by larger studies.

FUTURE PERSPECTIVES

St. Jude Medical registered its 23-mm Portico valve in a European clinical study in December 2011.⁴ The European trial has been designed to evaluate the safety and efficacy of the Portico THV in patients with severe aortic stenosis, and the results from this pivotal study are expected to support the device's European CE Mark clinical approval. Five European centers are currently participating in this observational prospective study, with an estimated enrollment of 50 patients who are being monitored for 1 year. The primary endpoint of the study is 30-day all-cause mortality; safety and efficacy (device success and functional improvement) at 30 days are the secondary endpoints. St. Jude Medical is currently in discussion with the FDA for a future randomized trial in the United States.

CONCLUSION

The new self-expandable Portico THV incorporates novel capabilities, such as valve recapturing and redeploying, which may be particularly helpful when the initial valve positioning is suboptimal or associated with complications (eg, coronary obstruction). Although initial experience with the Portico THV in humans has been associated with promising clinical and hemodynamic results, larger series and longer follow-up are needed to confirm these initial positive results. Also, only a randomized trial will fully demonstrate whether the potential advantages of the Portico THV translate into a clinically significant benefit compared to the currently available THVs.

Luis Nombela-Franco, MD, is with the Quebec Heart & Lung Institute, Laval University, Quebec City in Quebec, Canada. He has disclosed that he has no financial interests related to this article.

Josep Rodés-Cabau, MD, is with the Quebec Heart & Lung Institute, Laval University, Quebec City in Quebec, Canada. He has disclosed that he is a consultant to St. Jude Medical, Inc. and Edwards Lifesciences. Dr. Rodés-Cabau may be reached at (418) 656-8711; josep.rodes@criucpq.ulaval.ca.

1. Rodes-Cabau J. Transcatheter aortic valve implantation: current and future approaches. Nat Rev Cardiol. 2011;9:15-29.
2. Willson AB, Rodès-Cabau J, Wood DA, et al. Transcatheter aortic valve replacement with the St. Jude Medical Portico valve: first-in-human experience. J Am Coll Cardiol. 2012;60:581-586.
3. Manoharan G. St. Jude Medical Portico first-in-human clinical study. Presented at: 2011 TCT conference; November 7-11, 2011; San Francisco, CA.
4. Manoharan G. Assessment of the 23 mm St. Jude Medical Portico transcatheter aortic valve Portico 23-TF EU (Portico 23TFEU). ClinicalTrials.gov website. Available at: www.clinicaltrials.gov/ct2/show/NCT01493284. Accessed July 10, 2012.