A mechanism for immediate reduction in mitral regurgitation after cardiac resynchronization therapy
Insights from mechanical activation strain mapping
Hideaki Kanzaki, MD,
Raveen Bazaz, MD,
David Schwartzman, MD, FACC,
Kaoru Dohi, MD,
L. Elif Sade, MD and
John Gorcsan, III, MD, FACC*
University of Pittsburgh, Pittsburgh, Pennsylvania
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Figure 1 An example of acute reduction in mitral regurgitation by color Doppler before (left) and immediately after (right) cardiac resynchronization therapy.
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Figure 2 Echocardiographic strain images from the four-chamber view and two-chamber view, with corresponding time-strain plots from sites adjacent to papillary muscles before and after cardiac resynchronization therapy. Baseline plots demonstrate late peak strain occurring in the anterolateral papillary muscle site compared with the posteromedial papillary muscle site. Peak strain is aligned after cardiac resynchronization therapy in these sites.
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Figure 3 Construction of bull's-eye plot from multiple time-strain curves from the basal and mid-ventricular levels, demonstrating the anatomic location of papillary muscles in a "bull's-eye" plot.
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Figure 4 Pooled data demonstrating reductions in mitral regurgitant volume (left) and mitral regurgitant fraction (right) from immediately before to the day after initiation of cardiac resynchronization therapy. *p < 0.001.
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Figure 5 Mechanical activation maps in the "bull's-eye" projection from representative heart failure patients before and after cardiac resynchronization therapy (CRT). (A) A patient with LBBB. (B) A patient who previously received a right ventricular pacer (RV) for bradycardia and was RV paced at baseline. Time to peak systolic strain was color coded with lines representing isochrones of mechanical activation times at 50-ms intervals. The X indicates sites of lead placement, and the arrow indicates the direction of the propagating mechanical activation. Time to peak strain of sites adjacent to anterolateral (AL P) and posteromedial (PM P) papillary muscles are shown. A decrease in interpapillary muscle time delay was associated with decreased mitral regurgitation (MR).
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Figure 6 Pooled data demonstrating reductions in interpapillary muscle activation delay (left) from before to after cardiac resynchronization therapy (CRT). This was calculated as the difference between time to peak strain in papillary muscle sites. The change in interpapillary muscle activation delay after CRT (right) was significantly correlated with decreases in mitral regurgitant fraction.
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