Abstract 2474: Dynamic Change in LV Twist Mechanics in a Canine Model of Pacing-Induced Heart Failure
Background: LV twist may reflect LV contractility under different conditions. This study investigated LV twist dynamics and its determinants in a canine model of congestive heart failure (CHF).
Methods: Pacemakers and percutaneous leads were implanted in 8 adult hound dogs (mean weight, 38 kg), and continuous chronic RV pacing was applied at 230–250 bpm until CHF induction. Subsequently, pacing was turned off to allow the heart to recover. Echocardiography and LV catheterization were performed simultaneously at baseline, during CHF while pacing was temporarily switched off, and during recovery from CHF after pacing was stopped. CHF induction by pacing was repeated in 4 dogs. Apical and basal rotations were measured using 2D speckle tracking, and LV twist was calculated as the difference between apical and basal rotations. Untwisting rate was calculated as the peak diastolic time derivative of LV twist.
Results: CHF developed after 2–4 wks of pacing with LV end-diastolic volume (LVEDV), end-systolic volume (LVESV), end-diastolic pressure (LVEDP), and time constant of LV relaxation during isovolumic relaxation period (tau) all increasing significantly compared to baseline (Table⇓), and recovering to baseline levels 2–4 wks after pacing was stopped. LV twist and untwisting rate decreased with CHF compared to baseline, and improved during recovery from CHF although the change in untwisting rate between CHF and baseline was not significant. In pooled data, LV twist was significantly related to LVEDV (r=-0.60, P<0.001), LVESV (r=-0.59, P=0.001), LVEF (r=0.81, P<0.001), LVEDP (r=0.41, P=0.03) and +dp/dt (r=0.71, P<0.001), but not with end-systolic pressure (r=0.06, P=0.77). In multiple analysis, +dp/dt was the only independent predictor of twist (P < 0.001).
Conclusions: LV twist dynamics can reflect the presence of pacing-induced CHF and its recovery. LV contractility appears to be the only determinant of LV twist in CHF.