Abstract 12961: Activation Imaging: A Novel Approach to Three-Dimensional Mechanical Mapping in Native Conduction Delays and Pacing Using Speckle Tracking Echocardiography

Abstract

Background: Quantification of electro-mechanical activation is clinically important, but previous three-dimensional (3-D) mapping approaches have been technically difficult requiring catheter intervention.

Objective: To test the feasibility of a novel 3-D noninvasive approach, known as Activation Imaging (AI) to quantify LV mechanics in heart failure (HF) patients with native conduction delays and pacing induced activation.

Methods: We studied 66 subjects; 53 NYHA Class III-IV HF patients (age 66±10 yrs) referred for cardiac resynchronization therapy (CRT) with LV ejection fraction 27±7% (all ≤35%) and QRS duration 159±24 ms (all ≥120 ms). 31 patients had left bundle branch block (LBBB), and 22 had chronic right ventricular (RV) pacing. We also studied 13 normal volunteer subjects. AI utilized a 3-D speckle tracking endocardial area strain (combining factors of longitudinal and circumferential strain) and a pre-determined threshold to color-code mechanical activation (Aplio Artida, Toshiba Corp).

Results: AI was feasible in 92% (49/53) of HF patients and 100% (13/13) of normal subjects. The time difference between earliest and latest activation site (ΔT) both in LBBB (206±80 ms) and RV paced patients (190±52 ms) was similar (p=NS), but significantly greater than that in normal subjects (85±23 ms, p<0.0001 for both). A subset of 10 LBBB and 8 RV paced patients had repeat 3-D speckle tracking studies the day after CRT. Significant improvements in biventricular pacing in ΔT were observed both for LBBB (196±50 to 145±32 ms, p=0.002) and RV paced patients (193±29 to 149±24 ms, p=0.001). Sites of latest mechanical activation were most often posterior or lateral in LBBB and RV paced patients, while RV paced patients had sites of earliest activation more often from the apical septum (p=0.001).

Conclusion: AI in a novel 3-D strain imaging system to map electro-mechanical activation and has promise for clinical applciations in CRT patients.