Background
Cardiac synchronization therapy (CRT) is recognized as effective adjunctive therapy for heart failure; however, up to 40% of patients who undergo CRT device placement do not have a favorable response to therapy and are labeled non-responders. The lateral wall of the left ventricle (LV) is generally regarded as the optimal site for LV lead placement and some non-responders with LV leads not on the lateral wall can be converted to responders by repositioning the LV lead to the lateral wall. However, recent studies indicate that in some patients LV lead placement at a site other than the lateral wall may result in a better response to CRT. In such circumstances, empiric lateral wall lead positioning/repositioning may expose patients to the risks of another invasive procedure (including an increased risk of infection); in the case of lead repositioning to improve response to CRT the additional risk is doubled, as there is no certainty that the new position will be superior to the old.
Several investigators have used the acute hemodynamic response to biventricular pacing to determine the optimal LV lead position. To make these measurements some groups used a Millar pigtail catheter (Millar Instruments, Houston, Texas) while other groups used real-time pressure volume loops with a combined pressure-conductance catheter (CD Leycom, Zoetermeer, the Netherlands). One criticism of this method is that acute hemodynamic measurements may not correlate to long term response. However, Delnoy et al demonstrated that acute improvements in LV function as measured by pressure-volume loops during implantation corresponded to clinical and echocardiographic improvement during follow-up. In addition, Duckett et al demonstrated that the acute dP/dt response to LV pacing is useful for predicting which patients are likely to remodel in response to CRT, for both dilated and ischemic cardiomyopathy.
Despite these observations, few practitioners routinely utilize acute hemodynamic measurements for LV lead placement at the time of device implantation. Many practitioners believe targeted LV lead placement is impractical due to the time required to determine hemodynamic response to CRT and reposition the LV lead, and that venous anatomy, phrenic nerve pacing, and high pacing thresholds severely limit options for LV lead placement.
Study Hypothesis
It is hypothesized that it is both safe and feasible to use an interventional approach to LV lead placement (placing the LV lead guided by acute hemodynamic measurements), and that the LV lead can be placed in a position that is superior to the initial empiric lateral wall LV lead location in less than 30 minutes without significant risk to patients. The time from RV capture to LV activation correlates with the optimal pacing site based on stroke volume \& dP/dt measurements.
Study Purpose
The purpose of this study is to determine whether utilizing the CD Leycom pressure-conductance catheter to measure dP/dt and pressure volume loops at the time of LV lead implant (whether for the initial CRT implant or revision of an existing system) is both safe and feasible. It is hoped that the study will determine whether it is possible to use a patient's hemodynamic response to pacing to locate an LV pacing site that provides better hemodynamic response to CRT than the empirically selected lateral wall pacing site without significant patient risk (in terms of radiation exposure, amount of contrast received, procedure time, potential injury).
