Abstract 2822: A Novel Method for Assessing Left Ventricular Dyssynchrony
Background: The search for better echocardiographic markers of dyssynchrony has been hampered by the lack of a precise reference method for timing LV electromechanical activation. In the present study we propose a new method for defining onset of regional mechanical activation (OMA) and validate its ability to reflect onset of electrical activation as defined by regional intramyocardial ECG (IM-ECG).
Methods: In 12 anesthetized dogs with LV micromanometers we measured segment length in each LV wall by sonomicrometry and speckle tracking echocardiography (STE) (n=10) and electrical activation as onset of R in regional IM-ECG. OMA was defined as the time when the myocardial pressure-segment length coordinate deviated from its passive-elastic curve (Fig 1⇓). Timing was calculated relative to onset of R in ECG at baseline, caval constriction (n=7), during LBBB (n=5) and during LAD-occlusion (n=8).
Results: During all interventions we observed a small and essentially constant delay of OMA by sonomicrometry relative to electrical activation (14±8 (mean±SD).There was a close correlation between timing of electrical activation and OMA; R=0.88 and R=77, for sonomicrometry and STE, respectively, while correlation was moderate between electrical activation and time to peak S. Main results are displayed in Figures 2⇓ and 3⇓.
Conclusions: Timing of regional LV mechanical activation by OMA showed close correlation with regional electrical activation over a wide range of hemodynamic conditions and during LBBB. These findings indicate that assessment of LV dyssynchrony by this combined invasive and non-invasive approach may be superior to conventional echocardiographic methods.