Abstract 10232: Mechanistic Evaluation of Mechanical Dyssynchrony Indices and Their Ability to Predict Response to Cardiac Resynchronization Therapy
Introduction: Clinical studies highlight variable power of traditional echocardiographic dyssynchrony parameters to predict response to cardiac resynchronization therapy (CRT) and attribute it mostly to poor reproducibility.
Objective: Investigate whether this variability of predictive power can be explained by the operational definition of these dyssynchrony indices.
Methods: Four echocardiographic mechanical dyssynchrony measures (septal systolic rebound stretch [SSRS], interventricular mechanical dyssynchrony [IVMD], septal-to-lateral peak shortening delay [Strain-SL], and septal-to-posterior wall motion delay [SPWMD]) were quantified at baseline in 132 CRT-candidates (LVEF 19±6%; QRS 170±22ms). CRT-response was quantified as 6-months %-change of left ventricular (LV) end-systolic volume (ΔLVESV). A multiscale computer model of the human heart and circulation was used to assess the relationships between CRT-response and these indices within a wide range of LV dyssynchrony (50 combinations of delayed septal and LV free wall activation).
Results: In patients, SSRS showed best correlation with CRT-response followed by IVMD, Strain-SL, and SPWMD (Figure, all p<0.05). Patient data and simulations showed that SSRS and IVMD were linearly related to CRT-response, but that Strain-SL and SPWMD were discontinuously related to CRT-response as evidenced by data clusters (Figure). Simulations revealed that this data clustering originates from the complex septal deformation pattern, where a small increase in asynchrony of LV activation caused an abrupt shift of peak septal shortening from end-systole to early-systole. The broad correlation spectrum of IVMD originates from its large sensitivity to interventricular activation delay (red points in Figure).
Conclusion: Variability in predictive power of mechanical dyssynchrony indices to predict CRT-response is to a large extent determined by differences in their operational definition.
- © 2011 by American Heart Association, Inc.