Since the first report on percutaneous pulmonary valve implantation (PPVI) in a 12-year-old boy was published in 2000 by Philip Bonhoeffer, ^{Reference Bonhoeffer, Boudjemline and Saliba1} this catheter interventional treatment modality has been widely used in clinical practice with excellent results. ^{Reference Stefanescu Schmidt, Armstrong and Aboulhosn2} For thousands of patients worldwide with right ventricular outflow tract (RVOT) dysfunction, it offers a less-invasive alternative treatment option to surgery with a similar long-term result. ^{Reference Georgiev, Ewert and Eicken3} Until recently, three valves were available on the European market: Melody valve (Medtronic, Minneapolis, MN, USA), the Sapien valve (Edwards Lifesciences, Irvine, CA, USA), and the Venus P-valve (VenusMedtech, Hangzhou, China). However, the implantation of these valves is only possible in patients with a limited maximal RVOT diameter (Melody valve <25 mm, Sapien valve <31 mm, and Venus P-valve <34 mm). In patients in whom the RVOT is too large and too compliant for safe implantation of the above-mentioned valves, surgical treatment has remained the only possible treatment modality until recently. The evident necessity for inventing an alternative, percutaneous treatment option for patients with RVOT wider than 34 mm in diameter resulted in developing other self-expandable devices dedicated to the pulmonary position. One of these is the Harmony transcatheter pulmonary valve (Medtronic, Minneapolis, MN, USA), a porcine pericardial tissue valve attached to a self-expandible nitinol frame (Fig. 1a). It is the first US Food and Drug Administration-approved valve for patients with severe pulmonary regurgitation in the native and surgically repaired RVOT. It is commercially available in two versions with 22- and 25-mm diameter valves and a larger self-expanding nitinol frame. Both valves are implantable through a 25-French sheath. Although the initial experience is promising, this valve has not been implanted in Europe until recently and has been commercially available on the European market since December 2024. We report on four implantations of the Harmony valve performed in our centre with special access permission granted upon our application to BfArM in Germany.

Figure 1.

( a ) Harmony valve (source: https://www.medtronic.com/en-us/healthcare-professionals/products/cardiovascular/heart-valves/transcatheter-valves/harmony-transcatheter-pulmonary-valve.html). ( b ) Initial angiography was performed in the patient who underwent valve implantation via jugular access due to inferior vena cava interruption with azygos vein continuation. (patient no. 3); ( c ) the process of implantation of the Harmony valve, with the valve still attached to the delivery system; ( d ) final angiography after successful valve implantation.

In August 2024, four young adult patients with initial pulmonary stenosis (n = 3) and tetralogy of Fallot (n = 1) with severe pulmonary valve regurgitation were scheduled for PPVI with Harmony valve implantation. All interventions were conducted through individual patient-based exceptions. All procedures were performed after obtaining the patients’ informed consent and receiving individual approval for special access to a nob CE-marked device by the German authorities (BfArM). The patient characteristics are presented in Table 1. Prior to the procedure, a cardiac MRT and cardiac CT were performed in all cases. All procedures were performed using a biplane angiographic platform. Interventions were conducted under intravenous sedation in spontaneously breathing patients. The valve implantation was performed with the use of a 26-French-long Gore DrySeal sheath (W. L. Gore & Associates, Flagstaff, Ariz, USA) from venous femoral access in three cases and from jugular venous access in one patient due to interruption of the inferior vena cava with azygos vein continuation (Fig. 1b–d). No ultrasound guidance was used during the procedures. No vascular complications were recorded. All four implantations were successful, and the patients showed good function of the newly implanted valve without a significant gradient or regurgitation. There were no adverse events during implantation and within 72 hours after the procedure. There was no increase in the frequency of arrhythmias, recorded in the early 72-hour Holter electrocardiogram (ECG) compared to the pre-procedure Holter ECG in all patients. In the echocardiogram at discharge, neither pulmonary regurgitation, paravalvular leak, nor stenosis was recorded. All patients receive ASA for 6 months post-intervention. No complications occurred in the short-term follow-up (n = 3).

Table 1.

Patient characteristics

ToF = tetralogy of Fallot; PS = pulmonary stenosis; PR = pulmonary regurgitation; RV = right ventricle; MPA = main pulmonary artery; EDVI = end-diastolic volume index; EF = ejection fraction.

This small series of patients shows that the Harmony valve may offer a feasible and safe treatment option for patients with severe pulmonary regurgitation and dilated RVOT after surgical transannular patch augmentation of the RVOT or balloon valvuloplasty in early childhood. The accessibility of this valve on the European market offers an alternative, less-invasive treatment option for many patients with variable RVOT anatomy, in whom the other available balloon-expandable valves offer only limited applicability.

The Harmony valve as a self-expandable valve offers a different treatment concept in comparison to the balloon-expandable valves (Melody and Sapien valves) mentioned above. Due to the one-step delivery process, its deployment in the intended landing zone does not require pre-stenting and is therefore technically less demanding and faster. Its broad applicability is reflected in several studies showing promising results of Harmony valve implantations in large patient groups. On the contrary, data on the Venus P-valve—an alternative self-expandable valve—are limited.

Gillespie et al. ^{Reference Gillespie, McElhinney and Jones4} report on 87 patients in whom the Harmony valve was implanted with a 1-year follow-up time to date. The results of the study are promising. Twelve months after valve implantation, there were no deaths within the study group. The authors report on the freedom from significant pulmonary regurgitation, pulmonary stenosis, or re-intervention of 98% for the 22 mm valve and 91% for the 25 mm valve.

In the above-mentioned study, 16 % of patients presented non-sustained ventricular tachycardia at follow-up. Taylor et al. ^{Reference Taylor, Yang and Dubin5} report on non-sustained ventricular tachycardia in 40% of patients after 25 mm Harmony valve implantation within the first 24 hours after the procedure. The authors noticed that ventricular tachycardia episodes occurred only in patients with annular valve positioning, which was supposed to be a risk factor for arrhythmias. These arrhythmias lessened with time. The Early Feasibility Study in patients with a 22 mm Harmony valve demonstrated ventricular tachycardia in only 5% of patients. ^{Reference Benson, Gillespie and Bergersen6} In light of the described potential complication, all patients in our study group underwent 72-hour Holter ECG monitoring during their hospitalisation. We did not observe an increase in the frequency of arrhythmias in any of the patients from our study group. A second Holter ECG is planned 1 month after implantation. A larger study on PPVI with the Harmony valve was published recently. ^{Reference Goldstein, McElhinney and Gillespie7}

It is worth noting that the population of patients with severe pulmonary regurgitation and indication for PPVI who present dilated, compliant RVOTs is already large and still growing. Although balloon valvuloplasty of the pulmonary valve or surgical transannular patch augmentation of the RVOT offers a successful long-term result and the remaining pulmonary regurgitation is initially well tolerated, it was shown that, over time, it leads to serious adverse outcomes, ^{Reference Gatzoulis, Balaji and Webber8} so the intervention is needed in many patients to avoid re-operation. The optimal timing for abolishment of pulmonary regurgitation is yet still under debate.

Initial clinical experience with other self-expanding valves dedicated to patients with wide RVOT and severe pulmonary regurgitation like the Venus P-valve or the Pulsta valve (TaeWoong Medical Co., Gyeonggi-do, South Korea) is also promising in short- and mid-term follow-up in small patients’ cohort, ^{Reference Jin, Long and Zhang9,Reference Odemis, Yenidogan and Kizilkaya10} However, available data are very limited, and longer follow-up and larger patient groups are needed. It is worth mentioning that the Pulsta valve is still not available on the European market. Another alternative treatment modality that proved to be successful in a small patient cohort is Alterra Adaptive Prestent with SAPIEN 3 THV (Edwards Lifesciences, Irvine, CA, USA). ^{Reference Dimas, Babaliaros and Kim11} However, for this system, as well as for the two other aforementioned devices, the available data remain insufficient.

In conclusion, the Harmony valve offers a less-invasive and safe treatment alternative to surgery. Market accessibility of the Harmony valve has already extended the limits of the balloon-expandable pulmonary valves in the USA, Canada, Japan, and several other countries with promising results reported recently. We are delighted to note that this device has been accessible to European patients since December 2024. The initial reports on this valve in clinical practice are very promising, as also shown in our small study group. Nevertheless, a longer follow-up time is needed.