Localization of CRT According to Echocardiography: LOCATE-Pilot Study

CRT is a promising treatment modality for medically-refractory New York Heart Association (NYHA) class III or IV heart failure (HF) patients with intraventricular conduction delay (QRS > 130 ms). The randomized trials also suggest that a substantial minority of patients do not benefit, either echocardiographically or clinically, from CRT. In the MIRACLE trial, for instance, 35% of patients did not clinically improve after CRT. Objective reverse remodeling, typically defined as >15% reduction in the end-systolic volume, occurs in approximately 60% of patients. Most echocardiographic studies to date have reported only short- and intermediate-term results.

The objectives of the LOCATE-Pilot study are as follows: 1) to determine the proportion of patients undergoing CRT or CRT with defibrillator (CRT-D) with interpretable pulsed-wave tissue Doppler echocardiographic signals to quantitate and localize mechanical dyssynchrony; 2) to determine how frequently the LV lead can be successfully implanted in the most delayed basal segment (area of maximal delay); 3) to determine whether TDI guidance of CRT improves the proportion of patients with an echocardiographic response to treatment (reverse remodeling) at 6 months; 4) to determine whether TDI guidance of CRT improves the proportion of patients with a clinical response to treatment (6 min walk time, major clinical vascular events, or Minnesota Living with Heart Failure Quality of Life score); 5) to confirm that echocardiographic targeting of LV lead implantation is safe and does not hamper efficiency in the electrophysiological laboratory; 6) to validate the peak velocity delay (PVD) as a predictor of CRT response using pulsed-wave Doppler tissue imaging.

The LOCATE-pilot is a randomized, prospective study of 60 patients undergoing implantation of a Medtronic market approved CRT system. All patients will undergo a comprehensive baseline echocardiographic study in which a 6-segment model will be used to quantify dyssynchrony by the pulsed-wave Doppler technique. Myocardial viability will be assessed by conventional 2D criteria and nuclear perfusion data when available. Patients will be randomized to 1 of 2 groups with 30 patients per group on an intention-to-treat basis: 1) Control group: the implanting physician will have no knowledge of the baseline dyssynchrony assessment and use the current standard of care in the LV lead implantation; and 2) Echo-Guided group: the implanting physician will have full knowledge of baseline echocardiographic study and will use the dyssynchrony and viability data to guide final LV lead placement.

For this pilot study, patients will be followed for 6 months with a repeat Echocardiogram at 6 months. The primary endpoint of the study is indexed end systolic volume decrease >15% by biplane Simpson's technique.