Harpoon TDS-5
Harpoon Mitral Valve Repair System (Edwards Lifesciences, Irvine, CA) is a novel transapical off-pump mitral valve repair (MVr) system based on ePTFE chordal implantation. Differently from Neochord DS 1000 it was developed and tested to target severe DMR with isolated prolapsing Posterior Mitral Leaflet (PML). At present indeed, the device has not been evaluated for the treatment of Anterior Mitral Valve Leaflet (AML) disease, bileaflet prolapse and flail forms. Currently available for clinical use in Europe, it gained the CE mark in 20209.
The procedure is performed under transesophageal 2D /3D echocardiography guidance, general anesthesia, single lumen intubation. Trough anterior left mini-thoracotomy in the fifth intercostal space, the optimal entry site on LV apex is identified slightly more anterior than in Neochord procedure, and confirmed by finger testing under 2D TEE. Two small purse strings sutures are placed on-site and the ventricle is punctured, allowing for the positioning of a 14 Fr introducer. This is equipped with an inner hemostatic valve that allows for LV navigation without significant blood loss. The TEE X-plane view and 3D imaging assessment lead the positioning of the delivery system tip under the dome of the targeted scallop 11Gerosa, G., D’Onofrio, A., Besola, L., & Colli, A. (2018). Transoesophageal echo-guided mitral valve repair using the Harpoon system. European Journal of Cardio-Thoracic Surgery, 53(4), 871-873.. The needle passes through the leaflet tissue, far from the edge, releasing the suture. Then it’s automatically withdrawn, tightening the ePTFE coil and forming a double-helix knot on the atrial surface of the leaflet22Gammie, J. S., Bartus, K., Gackowski, A., D’Ambra, M. N., Szymanski, P., Bilewska, A., … & Duncan, A. (2018). Beating-heart mitral valve repair using a novel ePTFE cordal implantation device: a prospective trial. Journal of the American College of Cardiology, 71(1), 25-36. (Figure 3). The device is subsequently retrieved, carrying outside the neochordal free-end through the introducer. The procedure is repeated until the desired number of chords is implanted, using a different delivery system for each chord. Since the needle throw during device deployment is approximately 22 mm, Valsalva maneuver may be essential to promote an increase in left atrial volume and so increase the distance between the leaflet and the posterior LA wall to >25 mm during the leaflet piercing33Diprose, P., Fogg, K. J., Pittarello, D., Gammie, J. S., & D’Ambra, M. N. (2020). Intensive care and anesthesia management for HARPOON beating heart mitral valve repair. Annals of Cardiac Anaesthesia, 23(3), 321.. Under 2D/3D TEE guidance the chords are finally tightened to reach the best MR reduction, and then secured to the LV wall44Colli, A., Adams, D., Fiocco, A., Pradegan, N., Longinotti, L., Nadali, M., … & Gerosa, G. (2018). Transapical NeoChord mitral valve repair. Annals of cardiothoracic surgery, 7(6), 812..
To identify patients potentially suitable for the Harpoon MVRS, a careful preoperative screening is required, including detailed preoperative three-dimensional TEE. This allows to calculate the ratio of prolapsing PML length compared to the anteroposterior distance from the base of PML to the free edge of the AML, which is a predictor of adequate coaptation when the value is 1.5/155Gammie, J. S., Bartus, K., Gackowski, A., D’Ambra, M. N., Szymanski, P., Bilewska, A., … & Duncan, A. (2018). Beating-heart mitral valve repair using a novel ePTFE cordal implantation device: a prospective trial. Journal of the American College of Cardiology, 71(1), 25-36..
Since its first in human application in 201566Gammie, J. S., Wilson, P., Bartus, K., Gackowski, A., Hung, J., D’Ambra, M. N., … & Kapelak, B. (2016). Transapical beating-heart mitral valve repair with an expanded polytetrafluoroethylene cordal implantation device: initial clinical experience. Circulation, 134(3), 189-197., the device demonstrated to be safe and effective in reducing mitral regurgitation in patients with DMR. The TRACER trial (Mitral TransApical NeoChordal Echo-Guided Repair; NCT02768870) a prospective non-randomized multicenter clinical study45, enrolled 30 patients from April 2016 to November 2017, including subjects from 6 different European Centers with isolated severe degenerative MR due to P2 prolapse. Data published by Gammie et al. show how primary endpoint (30-day successful implantation of cords with MR reduction to moderate or less) was met in 27 out of 30 patients (90%). There were no deaths, strokes, or permanent pacemaker implantations. At 6 months, MR was mild or less in 85 % (22 of 26) and severe in 8% (2 of 26). A favorable cardiac reverse remodeling was demonstrated at 30 days.45 More recent clinical data from the TRACER CE trial were presented in June 2019 at TVT Structural Heart Summit (data lock on 17th December 2018).77https://www.tctmd.com/slide/harpoon-transapical-technology-and-clinical-updates The enrollment reached 65 patients; among them 62 had been successfully treated with Harpoon, 2 were converted to open surgery and 1 procedure had been aborted. No perioperative death or stroke were reported. Ten patients were later lost at follow up (2 of them died and 8 exit from the study for secondary intervention). Fifty-two patients reached 1 year of follow up, MR was mild or less in 75% (39 of 52) and severe in 2% (2 of 26). Positive reverse remodeling (in term of annular diameter and LEDV reduction) was confirmed at one year. The Harpoon program was also paused because of 4 additional cases of severe MR recurrence due to ePTFE chords rupture,9 then restarted and finally gained the CE mark in May 2020.

Conclusion

Transapical micro-invasive technologies are safe and effective options to treat MR in selected patients. Limitations are still present, first of all the lack of knowledge on durability. Moreover, the ability to treat a single component of the MV apparatus needs to face against the complexity of the mechanisms involving the disease.
Therefore, the cardiac mitral surgeon will have to fill these gaps by acting on a double front: on one hand he must extensively embrace micro-invasive solutions and apply them on well-selected patients; on the other hand he must gain a complete tool-box which allows for a tailored valve repair, based on combined multi-targeting procedures.
This evolution can guide the surgeon through the new revolution of MV micro-invasive tailored repair.