FRANK A. CUOCO, MD, J. LACY STURDIVANT, MD, ROBERT B. LEMAN, MD, J. MARCUS WHARTON, MD and MICHAEL R. GOLD, MD, PhD
Division of Cardiology, Section of Cardiac Electrophysiology, Department of Medicine, Medical University of South Carolina, Charleston, SC
Dr. Cuoco reports receiving honoraria as well as clinical trial support from St. Jude Medical, Inc.
Dr. Sturdivant and Dr. Leman report receiving clinical trial support from SJM.
Dr. Wharton reports receiving honoraria from SJM and is a member of the SJM Advisory Board and Data Safety and Monitoring Committee.
Dr. Gold reports receiving honoraria and clinical trial support from SJM and serves as a consultant for the company.
Manuscript submitted August 4, 2010, final version accepted August 13, 2010.
Address correspondence to: Frank A. Cuoco, MD, Division of Cardiology, Section of Cardiac Electrophysiology, Department of Medicine, Medical University of South Carolina, 25 Courtenay Drive, ART 7054, MSC 592, Charleston, SC 29425. E-mail: firstname.lastname@example.org
Patient JC is an 81-year-old male with a history of atrial fibrillation, congestive heart failure (NYHA Class III), ischemic cardiomyopathy with an ejection fraction of 25%, coronary artery bypass grafting, porcine aortic and mitral valve replacements, and a left bundle branch block (QRS duration 155 ms). He was referred for cardiac resynchronization therapy (CRT). A CRT pacemaker was planned due to the patient’s advanced age and preference not to have a defibrillator.
At the initial implantation procedure, coronary sinus (CS) cannulation was very difficult secondary to a posteriorly located CS ostium with a tortuous proximal course. After CS cannulation was achieved and a suitable posterolateral branch was identified, a left ventricular (LV) lead could not be delivered using a standard over-guidewire approach due to a lack of sheath support. Figure 1 illustrates the venogram from the initial procedure. Attempts to cannulate the lateral target vein directly with the CS lead delivery sheath failed, again due to tortuous anatomy and lack of sufficient support (this is best illustrated below in images obtained during the second implant procedure). Multiple leads (unipolar and bipolar), guidewires, subselection catheters, and electrophysiology catheters were utilized to facilitate lead delivery. After more than 3 h of procedure time over 60 min of fluoroscopy, attempts to implant an LV lead were abandoned, and plans were made for a repeat attempt in 1 month.
Figure 1: Coronary sinus venogram at initial implant (right anterior oblique projection).
At the second attempt, a new LV lead and delivery system was available. This system allows for delivery of a downsized bipolar LV lead directly through a subselection catheter. Using this system, the CS was cannulated and a coronary guidewire was advanced into the lateral target vein. The subselection catheter was advanced over this guidewire and a subselected venogram was performed (Figure 2). The support provided by the subselection catheter allowed for delivery of the downsized bipolar LV lead into the target vein with minimal difficulty (Figure 3). Once suitable thresholds without diaphragmatic stimulation were confirmed, the lead delivery system was slit. Final left anterior oblique (LAO) and right anterior oblique (RAO) images of the LV lead position are represented in Figures 4 and 5, respectively (note the tortuous course of the CS lead in the RAO image that caused difficulty in the initial implant procedure). Total procedure and fluoroscopy times for the second case were 25 and 4 min, respectively.
Figure 2: Subselected venogram of target vein (right anterior oblique projection).
Figure 3: Delivery of left ventricular lead through telescoping subselection catheter system (right anterior oblique projection).
Figure 4: Final left ventricular lead position (left anterior oblique projection).
CRT therapy has been shown to reduce hospitalizations, promote beneficial ventricular remodeling, and improve survival and symptoms in patients with advanced systolic heart failure and electrical dysynchrony.1,2 Recent studies support its use in broader heart failure populations with less severe symptoms.3,4 Other than proper patient selection, the ability to obtain optimal lead position at implant is probably the most important factor in achieving optimal response with CRT;5 recently, however, data from the COMPANION trial has called this into question.6 Initially, operators had limited options for implant tools, but in the past decade many advances have been made, resulting in improved implant success rates and decreased procedure and fluoroscopy times. However, different anatomic challenges still exist, as do problems with lead dislodgement, phrenic nerve stimulation, and exit block. Ideally, in order to deal with these issues, transvenous leads need to be small, fixate well at various locations, and allow for multiple pacing vectors.
Industry and operators developed various tools and techniques to improve implant success rates, access smaller and more tortuous vessels, achieve stable fixation, and pace from multiple locations using different vectors to attain lower pacing thresholds and to avoid phrenic stimulation. Over-the-wire leads and multishaped, atraumatic guides were some of the first developments.7 Telescoping lead delivery systems improve the ability to subselect and directly cannulate CS tributaries that may be ideal targets, but up until recently, leads could not be directly delivered through these sheaths due to size limitations.8–10 Magnetic navigation has also been used to facilitate transvenous LV lead delivery.11 CS venoplasty and stenting have also been used to enable delivery into small, tortuous and stenosed vessels, and even employed to aid in fixation of leads.12–14 Newer, “active” fixation LV leads (Medtronic, Minneapolis, MN) were developed and released, but they currently only allow for unipolar LV pacing. Also in development are multipolar LV leads, which will allow for markedly increased vector options, as well as simultaneous pacing from multiple sites within the target vein in efforts to achieve more “uniform” synchronization. Finally, new techniques are in development to achieve CRT from a non-transvenous approach, including endocardial LV lead placement using transseptal catheterization and transapical approaches.15,16
This case exemplifies the utility of using a downsized bipolar LV lead that could be delivered through a subselection catheter. In this case, there was extremely tortuous anatomy from the CS ostium to the target vein take-off that was under-appreciated by the initial venograms (see Figures 1 and 5 above). Additionally, as is often seen, the coronary guidewire could not provide adequate support for lead delivery due to this difficult venous anatomy. The angulation of the subselection catheter was ideal for cannulating the target vessel and performing a subselected venogram to identify the tributaries and potential locations for lead placement within the target vessel. Additionally, the support provided by the subselection catheter allowed for delivery of the lead directly from within the target vessel, avoiding the tension and torque that prevented implantation at the first procedure. Finally, this lead was a bipolar lead that allowed for multiple pacing vectors, optimizing LV capture thresholds while avoiding diaphragmatic stimulation. Having multiple pacing vector options can also be extremely useful at follow-up if thresholds increase or phrenic stimulation occurs due to lead movement, positional changes, or other dynamic factors.
Figure 5: Final left ventricular lead position (right anterior oblique projection). Note the extremely tortuous course that the left ventricular lead takes through the coronary sinus and target vein anatomy.
In conclusion, advances in CRT lead and delivery system technology, as well as development of new techniques for LV pacing, are resulting in increased implant success rates, improved patient response, and decreased procedure and fluoroscopy times. Using a telescoping system in conjunction with downsized, multipolar LV leads will likely become the new standard during transvenous lead placement and should help implanters to achieve better procedural and clinical success with greater efficiency and less radiation exposure.