In some cases it can be desirable to deliver and position a medical device in or near the left side of a patient's heart for diagnosing and/or treating cardiovascular disease. As just one example, patients with heart failure can in some cases be treated with cardiac resynchronization therapy (CRT) delivered with a collection of electrical leads, one of which is placed proximate the left ventricle for bi-ventricular pacing. A traditional placement for a left ventricular (LV) lead is a transvenous placement into one of the tributaries of the coronary sinus (CS). By some estimates, however, up to 40-50% of CRT patients do not respond to CRT with a traditional CS lead placement. One alternative to a traditional CS lead placement is a left ventricular endocardial lead placement. An LV endocardial placement may be useful for patients with poor CS lead access or stability or those with failed CS implants. Accordingly, there is a growing interest in LV endocardial lead placement.
Delivery catheters are often used to position electrical leads (and other medical devices) at various cardiovascular sites (e.g., such as a LV endocardical placement) within a patient via minimally invasive techniques. These catheters are constructed having a lumen, which provides a pathway to the implant site, through which an implanting physician may pass the medical device without encountering anatomical obstructions. Some delivery catheters include mechanisms, such as pull-wire actuation, which allow the implanting physician to actively change a curvature of the catheter in order to direct a distal tip of the catheter to a target implant site. Such catheters may be referred to as being “steerable” or “deflectable.” Other delivery catheters have resilient, pre-formed curvatures tailored to position a distal tip thereof at a particular anatomical site from a particular percutaneous access site. Such “fixed-shape” catheters can thus eliminate or reduce the need to actively control the curvature during the implant procedure.
In some cases delivery systems may include combinations of two or more steerable and/or fixed shape catheters. U.S. Patent Application Publication 2003/0144657 discloses one example of a catheter assembly employing an outer catheter with a pre-formed distal end and an inner catheter with a pre-formed distal end. Relative rotation and extension of the inner and outer catheters provides adjustable shaping of the catheter assembly's distal tip for improved locating and cannulating of, e.g., the coronary sinus via the right atrium. Another example of a coronary sinus access system is the ATTAIN SELECT® II 6248DEL delivery catheter system available from Medtronic, Inc., which can be used with an outer catheter such as the ATTAIN® 6227DEF deflectable catheter delivery system, also available from Medtronic, Inc.
Another common approach for accessing the left side of the heart is a transseptal access from the right atrium through the intra-atrial septum to the left atrium. U.S. Pat. No. 7,678,081, and U.S. Patent Application Publication 2007/0083168 provide examples of catheter systems employing a right to left atrial transseptal approach. U.S. Pat. No. 7,678,081 discloses, among other things, a catheter system including a guiding catheter, an access catheter, and a guide wire, which may be introduced to the right atrium from an inferior or a superior route. The catheter system includes a tissue penetration member carried by the access catheter for penetrating the septal wall. U.S. Patent Application Publication 2007/0083168 discloses another catheter system that accesses the left atrium from the right atrium by penetrating the intra-atrial septal wall. Among other things, the publication discloses a system including a stabilizer sheath having a side port, a shaped guiding catheter configured to exit the side port, and a tissue penetration member disposed within the guide catheter.
Methods of transvenously accessing the left ventricle are also known in the art. For example, a left heart catheterization can provide access to the left ventricle in a retrograde direction across the aortic valve, or a transseptal cardiac catheterization can access the left ventricle from the right atrium through the intra-atrial septum and left atrium. U.S. Pat. No. 6,156,018 discloses at least one example of the latter approach using a right femoral vein/inferior vena cava access. Another transseptal approach to the left ventricle includes the use of a Medtronic ATTAIN® 6227DEF deflectable catheter delivery system with a right Judkins catheter. Berry M. van Gelder, PhD, et al. Transseptal endocardial left ventricular pacing: An alternative technique for coronary sinus lead placement in cardiac resynchronization therapy. Heart Rhythm, Vol 4, No 4, April 2007, 454-460.
While a large number of catheter systems and delivery methods are presently available for accessing the heart, there remains a need for improved systems, especially for accessing the left ventricle of the heart.