Abstract 13617: Cardiac Resynchronization Therapy Increases Workload of the Right Ventricular Free Wall
Introduction: Right ventricular (RV) dysfunction is a predictor of reduced response to cardiac resynchronization therapy (CRT) in heart failure with left bundle branch block (LBBB). There is, however, limited insight into potential direct interactions between CRT and RV function.
Hypothesis: To investigate the effect of CRT on RV free wall function.
Methods: In 7 anesthetized dogs, LBBB was induced by radio frequency ablation. CRT was applied with septal and left ventricular lateral wall electrodes. RV pressure was measured by micromanometer and longitudinal strain in the RV free wall by sonomicrometry. Regional RV free wall work was calculated as the area of the RV pressure-strain loop.
Results: Induction of LBBB reduced RV free wall work from 39 ± 13 to 28 ± 14 mmHg*mm (± SD, p<0.05) and there was pronounced preejection shortening of total shortening (43 ± 11%). CRT restored RV free wall work to 39 ± 15 mmHg*mm (p<0.05) which was attributed to a reduction in preejection shortening to 17 ± 11% of total shortening (p<0.05, vs. LBBB). As illustrated in the figure, the increase in work was explained by an upward shift of the early systolic portion (preejection) of the RV pressure-strain loop (p<0.05). CRT increased RV dP/dtmax from 395 ± 69 to 467 ± 74 mmHg/s (p<0.05).
Conclusions: Induction of LBBB reduced RV free wall work and there was observed a substantial preejection shortening. CRT restored RV contraction pattern and work, consistent with a beneficial effect on RV function. However, in hearts with reduced RV function the CRT-induced increase in workload may not be well tolerated. Further studies are needed to explore if this interaction explains why RV dysfunction is a predictor of poor response to CRT.
Author Disclosures: P. Storsten: None. E.W. Remme: None. E. Boe: None. M. Eriksen: None. E. Kongsgaard: None. O.A. Smiseth: None. H. Skulstad: None.
- © 2014 by American Heart Association, Inc.