Background: Most current indices of synchrony quantify left ventricular (LV) contraction pattern in terms of a single, global (integrated) measure. We report the development and physiological relevance of a novel method to quantify LV segmental contraction synchrony. Methods: LV pressure-volume and echocardiographic data were collected in seven anesthetized, opened-chest dogs under several pacing modes: right atrial (RA) (control), right ventricular (RV) (dyssynchrony), and additional LV pacing at either apex (CRTa) or free wall (CRTf). Cross-correlation-based integrated (CCSI int) and segmental (CCSI seg) measures of synchrony were calculated from speckle-tracking derived radial strain, along with a commonly used index (maximum time delay). LV contractility was quantified using either E es (ESPVR slope) or ESPVR area (defined in the manuscript). Results: RV pacing decreased CCSI int at LV base (0.95 ± 0.02 [RA] vs 0.64 ± 0.14 [RV]; P < 0.05) and only CRTa improved it (0.93 ± 0.03; P < 0.05 vs RV). The CCSI seg analysis identified anteroseptal and septal segments as being responsible for the low CCSI int during RV pacing and inferior segment for poor resynchronization with CRTf. Changes in ESPVR area, and not in E es, indicated depressed LV contractility with RV pacing, an observation consistent with significantly decreased global LV performance (stroke work [SW]: 252 ± 23 [RA] vs 151 ± 24 [RV] mJ; P < 0.05). Only CRTa improved SW and contractility (SW: 240 ± 19 mJ; ESPVR area: 545 ± 175 mmHg•mL; both P < 0.01 vs RV). Only changes in CCSI seg and global LV contractility were strongly correlated (R 2= 0.698, P = 0.005). Conclusion: CCSI seg provided insights into the changes in LV integrated contraction pattern and a better link to global LV contractility changes.
All Science Journal Classification (ASJC) codes
- Cardiology and Cardiovascular Medicine