Apical cardiac resynchronization therapy significantly improved left ventricular torsion compared with right ventricular pacing (7.7 vs. 5.1 degrees, P<0.05), whereas free wall CRT did not.
Does cardiac resynchronization therapy improve left ventricular torsion and global systolic performance in a canine model of dyssynchrony?
In a canine model, LV torsion is primarily altered by dyssynchrony, and CRT that restores LV performance also restores torsion, which correlates strongly with stroke work and stroke volume.
Absolute Event Rate: 7.7% vs 5.1%
p-value: p=<0.05
Left ventricular (LV) systolic torsion is a primary mechanism contributing to stroke volume (SV). We hypothesized that change in LV torsion parallels changes in global systolic performance during dyssynchrony and cardiac resynchronization therapy (CRT). Seven anesthetized open chest dogs had LV pressure-volume relationship. Apical, basal, and mid-LV cross-sectional echocardiographic images were studied by speckle tracking analysis. Right atrial (RA) pacing served as control. Right ventricular (RV) pacing simulated left bundle branch block. Simultaneous RV-LV free wall and RV-LV apex pacing (CRTfw and CRTa, respectively) modeled CRT. Dyssynchrony was defined as the time difference in peak strain between earliest and latest segments. Torsion was calculated as the maximum difference between the apical and basal rotation. RA pacing had minimal dyssynchrony (52 ± 36 ms). RV pacing induced dyssynchrony (189 ± 61 ms, P < 0.05). CRTa decreased dyssynchrony (46 ± 36 ms, P < 0.05 vs. RV pacing), whereas CRTfw did not (110 ± 96 ms). Torsion during baseline RA was 6.6 ± 3.7°. RV pacing decreased torsion (5.1 ± 3.6°, P < 0.05 vs. control), and reduced SV, stroke work (SW), and dP/dt(max) compared with RA (21 ± 5 vs. 17 ± 5 ml, 252 ± 61 vs. 151 ± 64 mJ, and 2,063 ± 456 vs. 1,603 ± 424 mmHg/s, respectively, P < 0.05). CRTa improved torsion, SV, SW, and dP/dt(max) compared with RV pacing (7.7 ± 4.7°, 23 ± 3 ml, 240 ± 50 mJ, and 1,947 ± 647 mmHg/s, respectively, P < 0.05), whereas CRTfw did not (5.1 ± 3.6°, 18 ± 5 ml, 175 ± 48 mJ, and 1,699 ± 432 mmHg/s, respectively, P < 0.05). LV torsion changes covaried across conditions with SW (y = 0.94x+12.27, r = 0.81, P < 0.0001) and SV (y = 0.66x+0.91, r = 0.81, P < 0.0001). LV dyssynchrony changes did not correlate with SW or SV (r = -0.12, P = 0.61 and r = 0.08, P = 0.73, respectively). Thus, we conclude that LV torsion is primarily altered by dyssynchrony, and CRT that restores LV performance also restores torsion.
Lamia et al. (Fri,) conducted a other in Left ventricular dyssynchrony (n=7). Apical cardiac resynchronization therapy (CRTa) vs. Right ventricular (RV) pacing was evaluated on Left ventricular torsion (degrees) (p=<0.05). Apical cardiac resynchronization therapy significantly improved left ventricular torsion compared with right ventricular pacing (7.7 vs. 5.1 degrees, P<0.05), whereas free wall CRT did not.
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