Abstract 8949: Intermittent Systolic Overload induces Rapid Ventricular Hypertrophy and Promotes Better Ventricular Function in Young Goats
Introduction: Anatomical repair of transposition of the great vessels beyond the neonatal period requires preparation of the left ventricle for the 2-stage Jatene operation. Previous studies have demonstrated myocardial edema and necrosis in hearts that experience abrupt systolic overload, followed by late ventricular failure.
Hypothesis: Subpulmonary ventricle retraining with intermittent systolic overload could minimize the inadequacy of conventional pulmonary artery banding and promote better LV function under pharmacologic stress testing.
Methods: Nineteen young goats were divided into 3 groups: Sham (n=7; no systolic pressure overload), Continuous (n=6; systolic overload maintained for 96 hours) and Intermittent (n=6; 4 periods of 12-hour systolic overload, paired with a 12-hour resting period). Echocardiographic and hemodynamic evaluations were performed every day. Myocardial performance index and ejection fraction were evaluated at rest and during dobutamine stress. The animals were then killed for morphologic evaluation.
Results: Systolic overload area of Intermittent group, measured by RV to PA pressure gradient over time, was significantly smaller than Continuous group (p<0.05). Nevertheless, both groups had increased RV and septal masses, as compared to Sham (p<0.0002). Echocardiography revealed a major increase in the RV wall thickness of the Intermittent group (+64.8% ± 23.37%), when compared to Continuous group (+43.9% ± 19.26%; p=0.015). RV dilation and dysfunction was observed in both study groups after starting systolic overload (p<0.002). However, only Continuous group remained with significant RV dilation throughout the protocol (p <0.006). Intermittent group presented a significantly better myocardial performance index at the end of protocol, under resting and dobutamine infusion, when compared to Continuous group (p<0.012).
Conclusions: Both systolic overload protocols have induced a rapid RV hypertrophy. However, only Intermittent group had a better preservation of RV function, at the end of the protocol, both at rest and under dobutamine infusion. This study suggests that intermittent systolic overload may favorably affect the results for 2-stage Jatene operation.
- © 2011 by American Heart Association, Inc.