Bipolar Leads: New Options for CRT Implants

Cardiac resynchronization therapy (CRT), also known as biventricular pacing, provides symptomatic relief, clinical improvement, prolonged survival, and a better quality of life for many heart failure patients. CRT defibrillators (CRT-D) also provide potentially life-saving tachyarrhythmia therapies for these patients. Many of the challenges that occur during the implantation of CRT devices are due not only to venous anatomy, but to diaphragmatic stimulation and/or high left ventricular (LV) thresholds while positioning the LV lead. In August 2004, the FDA approved EASYTRAK ® 2 and EASYTRAK 3, the first bipolar LV leads in the United States. These leads, manufactured by Guidant Corporation, now give the physicians the ability to program around diaphragmatic stimulation and elevated thresholds. The testing and programming can be done either during implantation or post procedure. If the patient develops stimulation or elevated thresholds days, weeks, or even months post-implant, the vectors can be reprogrammed at that time as well. With older unipolar technology, the pacing vector for CRT therapy utilizes the tip of the LV lead along with the right ventricular (RV) lead coil. This is called the extended bipolar configuration. The advanced technology of Guidant Corporation s devices, programmers, and bipolar leads provide new options for physicians. Electronic Repositioning enables physicians to program around diaphragmatic stimulation and elevated thresholds without physically moving the LV lead. With Electronic Repositioning, there are now four pacing vector options for CRT-D (Figures 1-4) and six pacing vectors for CRT-P implants. These two new bipolar leads capable of providing Electronic Repositioning were recently introduced at the Mayo Clinic. Having a family of EASYTRAK leads gives the implanter the opportunity to inject contrast dye for a venogram, which allows lead selection based on the patient s anatomy (Figure 5). The new bipolar lead design and handling are similar to the original unipolar EASYTRAK lead. All of the leads are steroid-eluting and have a combination of polyurethane for abrasion resistance and silicone rubber for flexibility. The EASYTRAK 2 (Figure 7) is similar in shape to the EASYTRAK (Figure 6). The EASYTRAK 3 has a flexible fixation and is designed to provide stability in large branch veins and to allow repositioning within the same vein. The fluoroscopic marker assists in the correct placement within the vessel (Figure 8). The first challenge in the LV lead implant procedure is the cannulation of the coronary sinus (CS) ostium. The shape of the guide catheter plays a key role in the cannulation of the CS. Guidant s new RAPIDO ® ADVANCE guide catheter derives support from the superior vena cava (SVC) instead of the wall and floor of the often-dilated right atrium. The new guide catheter also has more support in the mid-shaft section for pushability, and softer distal segments to enhance access and tracking into coronary branch veins. The new 8 French (Fr) guide catheter works in concert with a 6 Fr inner catheter. This RAPIDO dual-catheter system has the ability to sit in a stable position and selectively deliver contrast medium, guidewires and a LV lead directly into a branch vein (Figures 9-10). Optimal LV lead location is important for maximizing CRT benefit. The implant challenge of getting into a tortuous branch is simplified by branch vein cannulation and Direct Delivery. RAPIDO ADVANCE, with its longer length, enables deeper fixation in the vessel, and enables Direct Delivery of the LV lead into the target vein. All of these improvements can help physicians achieve the goal of fast, predictable LV lead implants. In addition, Guidant provides guide catheters specifically designed for right-sided implants (Figure 11). The Mayo Clinic recently has had several clinical experiences with this new technology. The following case scenario demonstrates the application of this new technology. The benefits of this new technology extend beyond the implant by allowing programmable pacing vector options during patient follow-up. Mr. Smith is an 82-year-old male with a history of ischemic cardiomyopathy status post out-of-hospital cardiac arrest (OHCA). At that time, he received a Guidant 1831 DR ICD. His past medical history is significant for myocardial infarction and coronary artery bypass grafting. In the past year, Mr. Smith was hospitalized for congestive heart failure with complaints of fatigue. During hospitalization, his medical therapy was optimized. In November, Mr. Smith s ICD reached ERI. At that time, he was considered for CRT-D. His underlying rhythm showed atrial flutter with LBBB with a QRS duration of 146 msec. His ejection fraction was 15-20%, with associated Class III NYHA heart failure symptoms. The decision was made to proceed with upgrade to CRT-D. At the time of procedure, accessing the CS proved to be quite difficult. Once access to the CS was obtained, initial attempts at LV lead placement were unsuccessful. Balloon angiography was performed and showed scant tributaries in the distal CS with a large branch that tracked to the postero-lateral wall. The lead was ultimately placed in this large branch. Initial threshold via the analyzer using the bipolar Tip to Ring configuration was 0.5 msec/2.3 volts; the lead impedance was 1,097 ohms. However, thresholds through the device were elevated at 0.5 msec/3.5 volts in the same configuration. Since we were using Guidant s EASYTRAK 2 lead, we were able to utilize Electronic Repositioning. Through the device, the following thresholds were obtained using each of the four programmable pacing vector options: Tip to Ring: 0.5 msec/3.5 volts Ring to Tip: 0.5 msec/2.8 volts Tip to Coil: 0.5 msec/2.2 volts Ring to Coil: 0.5 msec/1.8 volts Based on the above thresholds, the final programmed pacing vector was Ring to Coil. As this case demonstrates, the technology of the Guidant EASYTRAK 2 bipolar LV lead allows physicians the option of Electronic Repositioning, which in this case resulted in a shorter procedure time benefiting both the patient and the practitioner.