Expanded Use of the One-Step Technique for Simultaneous Landing Zone Stenting and Placement of the Melody Transcatheter Pulmonary Valve

Objectives. We report a multicenter experience with simultaneous right ventricular outflow tract (RVOT) stenting and transcatheter pulmonary valve implantation using the Melody valve (Medtronic). Background. Prestenting the RVOT before Melody valve implantation is now the standard of care. Prestenting is usually performed as a separate step. The “one-step” technique for simultaneous landing zone stenting and Melody delivery was previously reported using only Max LD stents (Medtronic). We report a multicenter experience of simultaneous stenting and Melody implantation using multiple stent types in combination. Methods. This retrospective cohort study includes 33 patients from 3 centers who underwent simultaneous stenting and Melody valve implantation between 2017 and 2020. Key variables were compared with 31 patients from the same centers who underwent standard (non-simultaneous) prestenting followed by Melody implantation during the same time frame. Results. The 2 groups were similar in terms of age, weight, sex, and total procedure time. The 2 groups had similar clinical results and safety profiles, with no difference between the postimplantation right ventricle (RV) to pulmonary artery systolic pressure gradient, RV to aortic pressure ratio, and complication rate. The simultaneous group had lower radiation exposure as measured by dose area product. Up to 3 stents were safely placed simultaneously with a Melody valve. Conclusions. Simultaneous RVOT stenting and Melody valve implantation can safely be used to place up to 3 stents outside a Melody valve. This approach can simplify the catheterization procedure and potentially reduce radiation dose.

J INVASIVE CARDIOL 2021;33(12):E954-E959. Epub 2021 November 18.

Key words: adult congenital heart disease, pediatric congenital heart disease, percutaneous valve therapy

Percutaneous pulmonary valve implantation (PPVI) corrects right ventricular outflow tract (RVOT) obstruction and/or regurgitation and delays or obviates the need for surgery in patients with dysfunctional RVOT.¹ Creating a so-called “landing zone” by stenting the RVOT prior to PPVI (“prestenting”) is now standard of care with the Melody valve (Medtronic) to prevent Melody stent fracture occurring without prestenting.² In some cases (eg, in postsurgical native RVOT), prestenting is performed as a separate preparatory procedure followed by implantation of a Melody valve weeks or months later.³ However, in many centers, it is performed as a separate step during the same catheterization as PPVI.

In 2018, Boudjemline reported an innovative “one-step” technique in which a Melody valve and up to 3 additional Max LD stents (Medtronic) were deployed simultaneously using a standard 22 mm Ensemble delivery system (Medtronic). A decrease in median procedure time, fluoroscopy time, and radiation exposure, as measured by dose-area product (DAP), were noted in the 1-step group compared with the standard 2-step group, while no differences in postimplantation hemodynamics or complications were observed.⁴

In 2018, our centers also began using the 1-step technique for simultaneous landing zone stenting during PPVI with the Melody valve, using a combination of up to 3 Palmaz XL stents (Cordis), CP covered stents (B. Braun), or Max LD stents. We report our experience with this simultaneous stenting and PPVI technique.

All patients who underwent the simultaneous implantation technique at 3 academic centers (Rady Children’s Hospital; University of California San Diego; and Texas Children’s Hospital) during the study period (2017-2020) were included in the analysis. Institutional review board approval was obtained from all 3 institutions for this study; a data use agreement between the centers allowed for sharing of deidentified data for the analysis. For comparison, a control group was randomly selected from the 3 centers consisting of patients who underwent standard 2-step prestenting prior to Melody valve implantation during the same time period (to minimize confounding that might be introduced due to differences in practice patterns over time).

Procedure description for simultaneous implantation technique. Simultaneous stenting during Melody valve implantation is achieved by some slight modifications to the typical set-up (Figure 1). It should be noted that there is no difference in preimplantation testing (3-dimensional [3D] rotation angiogram with simultaneous balloon sizing for coronary compression testing and/or preprocedural 3D imaging demonstrating that the coronaries are remote from the target implantation area) when utilizing the simultaneous technique. Additionally, the typical practice of balloon sizing was used to guide the valve size, location, and need for additional stents. In addition to the typical preparation of the Melody valve, which is crimped by hand onto the balloon of the Ensemble delivery system, an additional stent is prepared by partially dilating it to a diameter that will fit outside of the Melody valve once it is crimped onto the balloon. The additional stent is then placed over the Melody valve and balloon, and crimped onto the Melody valve as a single unit. Sterile umbilical tape can be used to provide even, firm, circumferential pressure to ensure the additional stent sits tightly over the valve and balloon unit. Additional stents may be added per operator preference. Up to 3 stents — a combination of 1 CP stent and 2 Palmaz XL stents in our multicenter experience — have been successfully mounted in this way. Once all desired stents have been loaded over the Melody valve, the white sheath of the Ensemble delivery system is carefully advanced to cover the combination of stents and Melody valve. After identifying optimal positioning by fluoroscopy, the Melody valve and stents are all deployed simultaneously during balloon inflation. Optional postdilation can be performed with a non-compliant balloon.

Statistical analysis. Demographic, procedural, and complication data were compiled for both groups. The 2-sample t-test was used to compare continuous variables between the 2 groups and the Chi-square test was used to compare categorical variables. Fisher’s exact test was used to compare complications since the number of events was small. All statistical analyses were performed using R, version 4.0.0 (The R Foundation for Statistical Computing).

The simultaneous stenting technique was used in 33 patients. In 12/33 patients, only the simultaneous stenting technique was used and no other prestents were deployed. In the remaining 21/33 patients, separate RVOT prestenting was performed, followed by the simultaneous deployment of an additional stent or stents over a Melody valve. The majority of the 21 patients who underwent both separate prestenting followed by simultaneous stenting were patients with conduits, and in 20/21 cases, only 1 separate prestent was placed followed by additional stent(s) simultaneously with the Melody valve. In these patients, the separate prestent implantation was used to gauge the amount of recoil in the conduit, helping to determine how many total stents would be needed (the rest being placed using the simultaneous technique). An additional 31 patients who underwent standard Melody PPVI during approximately the same time period served as the comparison group.

The simultaneous group and standard group were similar in terms of preprocedural demographic data, including age, weight, sex, underlying congenital heart disease, and indication for PPVI. The simultaneous group had a larger proportion of patients with native RVOT and fewer patients with a bioprosthetic valve (Table 1). Differences in preprocedural hemodynamics between the 2 groups were statistically significant, with lower right ventricle (RV) to aortic pressure ratio and lower RV to pulmonary artery pressure gradient in the simultaneous vs standard groups (Table 2). After PPVI, there was no significant difference in the RV to aortic pressure ratio or RV to pulmonary artery pressure gradient between groups (Table 2).

There was no difference between the total procedure time, complication rates, or total number of stents placed during the procedure. The dose-area product (DAP) and DAP indexed to weight were lower in the simultaneous group compared with the standard group (Table 3).

In addition to reporting the total number of stents and the frequency with which we placed either 1, 2, or 3 simultaneous stents as noted above, we report an initial guideline to the maximum number and combination of simultaneous stents that can be placed using a given delivery system based on our experience (Table 4). Note that delivery of a Melody valve with a simultaneous stent at 24 mm diameter was accomplished using a 4010 Palmaz Stent over a Melody valve, all mounted on a 24 mm balloon-in-balloon catheter, which was positioned and delivered using a 22 Fr DrySeal sheath (W.L. Gore & Associates).

We report the safe and effective simultaneous deployment of up to 3 stents during PPVI with the Melody valve in patients with conduits, bioprosthetic valves, and native RVOT. We also report decreased DAP with this approach when compared with the standard group. Our experience did not demonstrate a statistically significant difference in the total procedure time, nor did we see a difference in procedural complications. Our data reinforces Boudjemline’s work and also suggests safe expansion of the underlying concept of simultaneous stenting to include the use of a combination of up to 3 Palmaz XL, CP Covered, and Max LD stents.

Expanding the use of the simultaneous stenting technique represents an evolution in PPVI toward greater simplicity and reproducibility. Boudjemline’s findings as well as our own suggest its adoption will likely reduce total radiation exposure. Cumulative radiation exposure from cardiac catheterizations is linked to higher lifetime attributable risk of malignancy;^5,6 thus, any innovation that can reduce radiation with a similar safety and effectiveness profile is preferred. Although there was no statistically significant difference in the incidence of complications between the 2 groups, the authors’ position is that simultaneous prestenting simplifies the procedure and could theoretically reduce prestent dislodgment by using fewer balloon inflations and fewer interruptions to reposition wires, balloons, and stents. This technique will likely be most helpful in patients with native RVOT in whom the risk of dislodgment of the landing zone stent during subsequent valve delivery is highest.

An anticipated effect of simultaneous prestenting was a decrease in the overall procedure time owing to the simplified technique for implantation. While our analysis did not show a difference in the total procedure time, our primary operators report that subjectively simultaneous deployment simplifies the procedure and reduces the risk of dislodging prestents and risk of suboptimal Melody positioning within the prestents. Even when separate prestenting followed by simultaneous additional stenting was performed, the subsequent simultaneous implantation eliminates at least 1 additional step and additional risk of dislodgment or malposition.

Our work demonstrates that the simultaneous technique need not be limited to the use of Max LD stents. We have found that the 1-step technique can be used with multiple stents and in various combinations. A recent meta-analysis of prestenting with the Melody valve demonstrated that multiple prestents provide better protection against stent fracture than just 1 prestent;^2,7 however, the optimal number of prestents for a given clinical picture is not yet known. Thus, there is currently no evidence-based recommendation for the optimal number and combination of prestents for a given RVOT substrate or size.

It follows that we do not have an evidence-based algorithm for determining the optimal number and combination of simultaneous stents to be used; however, we offer some introductory ideas from our experience. When the RVOT substrate is a conduit, the total number of the stents is chosen to overcome conduit recoil forces. We often used a strategy whereby we placed 1 prestent separately to gauge the strength of the recoil forces, and then placed additional simultaneous stents with the Melody valve based off the initial recoil. This strategy accounts for a majority of the 21 patients in whom we used both separate and simultaneous stenting. One further element in the decision-making process was whether or not to use a covered stent during the procedure. Although the details are controversial, some preprocedural factors predict which patients have a higher risk for an RVOT/conduit tear during PPVI, including the pre-PPVI peak RVOT conduit gradient, conduit size, and conduit type.^2,8-10 Thus, when using simultaneous stenting in conduits with a higher risk of tear, a covered stent can be placed, either separately when measuring the recoil forces early in the case, or with simultaneous Melody implantation in order to cover potential conduit tears that might occur during the dilation.

When the RVOT substrate is native, the number and combination of stents is not usually selected based on recoil, but rather on size. In native RVOTs <22 mm in diameter, we often use 1 simultaneous stent (Palmaz), since the recoil forces are assumed to be low and the valve is well supported by tissue. In native RVOTs >22 mm in diameter, we sometimes opt for additional simultaneous stents to increase the effective outer diameter of the valve unit during implantation and allow for implantation of the Melody valve unit in patients with native RVOTs beyond 24 mm (the reported outer diameter of the Melody valve inflated with the standard 22 mm Melody ensemble balloon).¹¹ It should be noted that some patients with large (usually native) RVOTs are good candidates for the Edwards Sapien S3 valve (Edwards Lifesciences), which is available in larger diameters (26 mm and 29 mm) than the Melody valve. However, in order to avoid damage to the tricuspid valve, we prefer to implant larger Sapien valves in the pulmonary position using a long 24 Fr or 26 Fr sheath.¹² This presents a problem for patients who have RVOT measurements >24 mm, but have smaller veins that may not accommodate the larger-size sheath needed to safely implant the Sapien valve. This subset of patients theoretically benefits from using a Melody valve delivered with an Ensemble (22 Fr) with simultaneous prestents to increase the outer diameter. Based upon the assumption that an additional stent would add ~1 mm to the diameter of a stent/valve unit, 2 additional stents placed simultaneously over a 22 mm Melody ensemble would provide an actual outer diameter of close to 26 mm. Further postdilation (which has been shown to be safe without significant valve regurgitation)¹¹ might even facilitate an even greater outer diameter, allowing a Melody valve to be implanted in a native RVOT as large as 27-28 mm.

Finally, some preprocedural factors also predict stent fracture or need for reintervention¹³ after Melody valve implantation, which might signal the proactive use of the maximum number of prestents that can fit on the assembly (Table 4), regardless of the recoil or size of the outflow tract.

We should note that the preprocedural hemodynamics differed between our groups, with the simultaneous group having a lower baseline RV to systemic pressure ratio and a lower RV to pulmonary artery gradient. Although the differences were statistically significant, the clinical significance of these differences is unclear, since both 55% and 63% RV to systemic ratios are slightly over “half-systemic,” and a difference of 20 and 30 mm Hg RV to pulmonary artery gradient are both in the “mild stenosis” (<36 mm Hg) category.

We did have 1 complication where we underestimated the size of a native RVOT; as a result, a Melody valve with 2 simultaneous stents dislodged, ultimately requiring the first Melody to be pinned in place by an additional stent and Melody valve. It should be noted that this dislodgment was not related to any particular technical difficulties with simultaneous stent deployment; however, the event reinforces the need to carefully measure the RVOT, especially in patients with native substrate, even when using the simultaneous deployment technique.

Study limitations. Our study is not exempted from the inherent limitations of a retrospective study. Additionally, it should be noted that there were some preprocedural differences between our simultaneous group and the standard group. As reported, there were more patients with native RVOT in the simultaneous group compared with the standard group. This may reflect a perception in our operators that patients with native RVOT were more likely to benefit from simultaneous prestenting owing to a lower risk of landing zone stent dislodgment. Lastly, we note that while we did have a similar number of patients in both groups, we did not have true matched controls, and the comparison group was comprised of those patients who underwent standard prestenting during a similar time frame as the simultaneous cohort in order to minimize chronology bias.

In this study, we demonstrated the feasibility of simultaneous stenting with a combination of up to 3 stents over the Melody valve without major complications. Moreover, this technique showed a reduction in DAP when compared with the conventional 2-step prestenting method. This small study provides preliminary support for safety and demonstrates some potential use cases for the technique. Further studies with a larger cohort are needed to clearly demonstrate safety and to more clearly define which cohort of patients will benefit from this technique.

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