Rationale for lumenless leads
Lumenless leads were first developed over 20 years ago with an aim to reduce the diameter of pacing leads and allow precise catheter delivery while improving reliability[1]. Smaller diameter leads reduce subclavian crush, venous and valvular stenosis, and improve the ease of extraction[1-3] . Currently, the model 3830 lead (Medtronic, Inc., Minneapolis, MN) is the only available lumenless pacing lead. This lead has demonstrated excellent acute and long- term electrical performance[4, 5]. Figure one depicts the difference between the design of this lead and others. This lead utilizes a flexible inner cable as the core conductor coupled to a fixed, electrically active helix. The flexible central cable is intended to reduce the risk of fracture, while also providing a stable platform for lead extraction. There is now a similarly designed defibrillation lead in clinical trial[6].
These leads were initially used for standard endocardial pacing but are now commonly used for selective conduction system pacing. The steerability of the delivery system allows for ease of site selection, while the small diameter of the lead allows for ease of tissue penetration. Interest in directly pacing the conduction system began in 1978[7]. Modern conduction system pacing first targeted the bundle of His and now more commonly targets the matrix of the left bundle by attempting to penetrate into the interventricular septum[8, 9].