Detachment Force of the Helical Anchor in Mitral Annulus

Abstract

Helical anchors are used in transcatheter mitral valve repair. The aim of the current study was to investigate effect of helical anchor design, anchored position and biting depth on the detachment force in an in-vitro experiment. Mitral annulus was excised from 36 fresh porcine hearts and mounted in an unaxial test rig. Seven helical anchors were made of stainless steel based on the geometric parameters: outer diameter, wire diameter, and pitch. The helical anchors were screwed in at 3 to 9 o'clock positions of the posterior annulus, namely, P3-9, and pulled out. The pullout force was measured with the maximal pullout force defined as the detachment force. The detachment force within the medial, lateral and central positions were comparable (p ​> ​=0.069). The detachment force at P6 was lowest compared with the medial and lateral positions, and was 5.459 ​± ​0.193 ​N, 5.586 ​± ​0.113 ​N, 8.911 ​± ​0.250 ​N for the anchors in the outer diameters of 3, 4, 5 ​mm, respectively at the pitch of 2 ​mm and the wire diameter of 0.4 ​mm and biting depth of 3 coils. The detachment force increased with the outer and wire diameters, but was not affected by the pitch at the biting depth of 3 coils (p ​≥ ​0.279). The detachment force of the helical anchor is lowest in the central posterior annulus region, and the biting depth in 3 or more coils is recommended. The helical anchor is stronger than the suture.