Compression coil provides increased lead control in extraction procedures.

AIMS: We investigated a new lead extraction tool (Compression Coil; One-Tie, Cook Medical) in an experimental traction force study. METHODS AND RESULTS: On 13 pacemaker leads (Setrox JS53, Biotronik) traction force testing was performed under different configurations. The leads were assigned to three groups: (i) traction force testing without central locking stylet support (n = 5), (ii) traction force testing with the use of a locking stylet (Liberator, Cook Medical) and a proximal ligation suture (n = 4), (iii) traction force testing with the use of a locking stylet and a compression coil (n = 4). The following parameters were obtained for all groups: stress-strain curves, maximal forces, elastic modulus, post-testing lead length and lead elongation. In Groups 2 and 3 retraction of the locking stylet within the lead was measured [lead tip-locking stylet distance (LTLSD)]. Maximal forces for the three groups were: (i) 28.3 ± 0.3 N; (ii) 30.6 ± 3.0 N; (iii) 31.6 ± 2.9 N (1 vs. 2, P = 0.13; 1 vs. 3, P = 0.04; 2 vs. 3, P = 0.65). Elastic modulus was (i) 22.8 ± 0.1 MPa; (ii) 2830.8 ± 351.1 MPa; (iii) 2447.0 ± 510.5 MPa (1 vs. 2, P < 0.01; 1 vs. 3, P < 0.01; 2 vs. 3, P = 0.26). Mean LTLSD in Group 2 was 19.8 ± 3.2 cm and was 13.8 ± 1.7 cm in Group 3 (P = 0.02). The ratio of LTLSD/post-testing lead length was 0.37 ± 0.03 for Group 2 and 0.24 ± 0.03 for Group 3 (P < 0.01). CONCLUSION: The application of a compression coil leads to an increased lead control expressed by less retraction of the locking stylet within the lead. This enables improved central support of extraction sheaths in the case of challenging extraction procedures.

Concept and first experimental results of a new ferromagnetic assist device for extra-aortic counterpulsation.

OBJECTIVES: Based on a ferromagnetic silicone cuff for extra-aortic counterpulsation, a new assist device concept was developed. The driving force is generated by an external magnetic field, which leads to contraction of a soft magnetic cuff. The force generation capacity of the device was tested in a silicone aorta model. METHODS: Magnetic elastomers can be constructed through dispersion of micro- or nanoparticles in polymer matrices and were designed to act as soft actuators. Two magnetically active silicone cuffs were produced with a nanomagnet loading of 250 wt% (Cuff 1) and a micromagnet loading of 67 wt% (Cuff 2). The magnetic cuffs were applied on a silicone aorta model and contracted against hydrostatic pressure. RESULTS: A full contraction of Cuff 1 was possible against a maximal hydrostatic pressure of 30 cmH2O (22 mmHg) at a magnetic flux density of 0.4 T (Tesla) and 65 cmH2O (48 mmHg) at a magnetic flux density of 1.2 T. A 50% contraction of Cuff 2 was possible against a maximal hydrostatic pressure of 80 cmH2O (59 mmHg) at a magnet-cuff-distance (MCD) of 0 cm. At MCDs of 1 and 2 cm a 50% contraction was possible against 33 cmH2O (24 mmHg) and 10 cmH2O (7 mmHg), respectively. CONCLUSIONS: Combining the advantages of magnetic elastomers with the principle of extra-aortic counterpulsation in a new assist device concept avoids the need for anticoagulation (no contact with bloodstream). With regard to the magnetic principle of action, no intra- to extracorporeal connection is needed. More experimental work is needed to further increase the force generated by the silicone cuff and to transfer the device concept into an in vivo setting.