Examination of epimysial leads used to stimulate the latissimus dorsi muscle

Cardiomyoplasty is a new surgical treatment for heart failure in which the patient´s latissimus dorsi muscle (LDM) is isolated, wrapped around the heart, and electrically stimulated to provide cardiac assistance. At present, long term stimulation of the LDM is achieved with intramuscular electrodes, which produce minimal nerve damage. This study examined the use of epimysial electrodes by measuring the epimysial lead characteristics during a four-week LDM training. Lead resistance started at 463±41 Ω after implantation, decreased during the following week (251±16 Ω), and remained less than the initial value during the last three weeks (week two: 282±19 Ω and week four: 341±28 Ω). The recruitment properties were similar to nervecuff electrodes: low threshold voltages (week one: 0.75±0.12, week two: 0.90±0.33, week four: 0.52±0.10 V) and a very steep recruitment curve with low saturation voltages. Histological examination revealed normal muscle fibers with no inflammatory response. Epimysial leads may be more convenient for most surgeons because the design does not require any free-dissection of the nerve nor guiding a needle around the nerve with the risk of perforating vessels or nerve branches. These results indicate that epimysial leads are worthy of further investigation.