Background
The acute response to cardiac resynchronization therapy (CRT) has been shown to be
due to 3 mechanisms: resynchronization of ventricular contraction, efficient preloading
of the ventricles by a properly timed atrial contraction, and mitral regurgitation
reduction. However, the contribution of each of the 3 mechanisms to the acute response
to CRT, specifically stroke work improvement, has not been quantified.
Objective
To use a magnetic resonance image-based anatomically accurate 3-dimensional model
of failing canine ventricular electromechanics to quantify the contribution of each
of the 3 mechanisms to stroke work improvement and identify the predominant mechanisms.
Methods
An MRI-based electromechanical model of the failing canine ventricles assembled previously
by our group was further developed and modified. Three different protocols were used
to dissect the contribution of each of the 3 mechanisms to stroke work improvement.
Results
Resynchronization of ventricular contraction did not lead to a significant stroke
work improvement. Efficient preloading of the ventricles by a properly timed atrial
contraction was the predominant mechanism underlying stroke work improvement. Stroke
work improvement peaked at an intermediate atrioventricular delay, as it allowed ventricular
filling by atrial contraction to occur at a low diastolic left ventricular pressure
but also provided adequate time for ventricular filling before ventricular contraction.
Reduction of mitral regurgitation by CRT led to stroke work worsening instead of improvement.
Conclusion
Efficient preloading of the ventricles by a properly timed atrial contraction is responsible
for a significant stroke work improvement in the acute CRT response.
Abbreviations:
AV (atrioventricular), CRT (cardiac resynchronization therapy), DHF (dyssynchronous heart failure), LA (left atrium), LBBB (left bundle branch block), LRd (Luo-Rudy dynamic), LV (left ventricle/ventricular), MRI (magnetic resonance image), RA (right atrium), RV (right ventricle/ventricular)Keywords
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Article info
Publication history
Published online: August 07, 2013
Footnotes
Dr Trayanova is a cofounder of CardioSolv, LLC. CardioSolv was not involved in this research. Dr Gurev is employed by the IBM T.J. Watson Research Center. There are no patents, products in development, or marketed products to declare.
This work was funded by the National Institutes of Health (NIH) grant R01-HL103428, National Science Foundation grants CBET-0933029 and IOS-1124804 (to Dr Trayanova), and NIH fellowship F31-HL103090 (to Dr. Constantino).
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© 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.
