|
|
Ventricular Restraint Decreases RV Diastolic Compliance and Prevents RV Dilatation in Heart Failure
Lawrence S Lee, Ravi K Ghanta, Vakhtang Tchantchaleishvili, Daihei Wang, Suyog Mokashi, Rita G Laurence, O Coelho-Filho, Raymond Kwong, Ralph M Bolman, *Lawrence H Cohn, Frederick Y Chen
Brigham and Women's Hospital, Boston, MA
Background: Our previous studies have shown that ventricular restraint decreases left ventricular (LV) transmural pressure (Ptm) and indices of myocardial oxygen consumption (MvO2) to promote LV reverse remodeling in heart failure (HF). No study has yet evaluated the acute and chronic effects of restraint on the right ventricle (RV). We hypothesized that ventricular restraint decreases RV Ptm and effective diastolic compliance and prevents RV remodeling in HF.
Methods: A fluid-filled epicardial balloon was implanted around the ventricles of 10 adult sheep. Restraint levels were defined by the maximum pressure applied by the balloon to the epicardium. This occurred at end-diastole. In each animal, aortic, LV, RV, and epicardial pressures, and RV volume were measured at 5 increasing restraint levels (0, 1.5, 3.0, 5.0, and 8.0 mmHg) in an acute study. Ptm was defined as ventricular pressure minus epicardial pressure. At each restraint level, a caval occlusion was performed to determine the effective RV systolic (Cs) and diastolic (Cd) compliance. Effective RV Cs and Cd is a combination of restraint wrap and RV compliance. Indices of myocardial oxygen consumption, tension-time index (TTI) and pressure volume area (PVA) were then calculated for each restraint level. The chronic effects of restraint on the RV remodeling were then evaluated by implanting a passive ventricular restraint wrap around the ventricles in a chronic HF sheep model. HF developed in 3 animals 2 months after ligation of diagonal coronary arteries. RV end-diastolic volume (EDV) and ejection fraction (EF) were assessed with cardiac MRI over a 4 month interval. Changes in RV mechanics and size were assessed using a mixed-model.
Results: Unlike the LV, ventricular restraint had no significant effect on RV Ptm (p=0.92) or indices of RV MvO2 (p=0.90). As restraint level was increased, diastolic RV pressure increased correspondingly. Restraint had no effect on RV systolic contractility (p=0.43). Restraint decreased RV diastolic compliance and shifted the diastolic pressure-volume relationship to the left (p<0.05). In chronic studies, progressive RV dilatation was prevented with restraint therapy. RV EDV was 64+6 ml at the start of therapy and 67 +7 ml after 4 months of therapy (p=0.2). RV EF was 60+4% at baseline and 61+8% after 4 months of therapy (p=0.7).
Conclusions: Ventricular restraint affects the RV differently than the LV. Restraint decreases effective diastolic compliance of the RV but unlike the LV, does not decrease RV Ptm and indices of MvO2. The decrease in effective diastolic compliance may prevent further RV dilatation in HF. Because RV Ptm and indices of MvO2 are not reduced with restraint, unlike the LV, higher levels of restraint may not induce reverse RV remodeling.
Table 1: | | | | | | | Restraint Level
(mmHg) | LV | RV | | Mean Ptm (mmHg) | Mean Ptm (mmHg) | Mean TTI
(mmHg*sec) | Mean PVA (mmHg * mL) | Cs
(mL/mmHg) | Cd
(mL/mmHg) | | 0 | 32.3 | 12.4 | 6.5 | 901 | 0.6 | 12.1 | | 1.5 | 32.0 | 10.2 | 5.0 | 1000 | 0.8 | 11.8 | | 3.0 | 27.5* | 13.2 | 6.7 | 1486 | 0.9 | 7.9* | | 5.0 | 23.8* | 13.2 | 6.9 | 1331 | 0.7 | 5.4* | | 8.0 | 16.8* | 13.6 | 7.2 | 1164 | 0.9 | 3.1* | | *p<0.05 change from baseline |
Back to 2009 Annual Meeting
Back to Main Program
|
