Abstract 1942: The Natural History and Impact of Mechanical Dyssynchrony on Ventricular Function in Hypoplastic Left Heart Syndrome
The natural history of right ventricular mechanical dyssynchrony in hypoplastic left heart syndrome (HLHS) remains unclear. Results from cardiac resynchronization therapy in single ventricle patients in the intensive care setting are promising, with variable long-term success. To study the evolution of mechanical dyssynchrony in HLHS, we compared results prior to Norwood and bidirectional cavopulmonary connection (BCPC) palliation. The impact of mechanical dyssynchrony on RV function was compared with cardiac magnetic resonance imaging (CMRI).
Methods: We prospectively enrolled 14 HLHS patients prior to surgical palliation. Three patients were excluded from final analysis due to interstage mortality. All remaining patients had echocardiography pre-Norwood and pre-BCPC. Cardiac MRI was performed in 8 of 11 patients pre-BCPC. Mechanical dyssynchrony was assessed by STI in both longitudinal and circumferential planes. Mechanical dyssynchrony index (SDI) was measured by the standard deviation of time to peak strain reported as a percentage of systole.
Results: Mechanical dyssynchrony index of both longitudinal (21 ± 10% vs 16 ± 5%), basal circumferential (24 ± 11% vs 19 ± 11%) and apical circumferential (12 ± 5% vs13 ± 10%) contraction were not significantly different between pre-Norwood and pre-BCPC respectively (p>0.05). Basal circumferential SDI linearly correlated with abnormal RV parameters measured on CMRI: RVEDV (r=0.93, p<0.001), RVESV (r=0.92, p<0.002), RVEF (r= −0.83, p<0.01) and RV mass (r=0.80, p<0.02), indexed to body surface area. Apical circumferential SDI correlated with CMRI; RV mass/EDV ratio (r=0.95, p=0.003). Longitudinal SDI had a weaker correlation with CMRI: RV mass (r=0.74, p=0.03) and RV mass/EDV ratio (r=0.75, p=0.03). No correlation was observed between SDI and QRS duration (mean 71 ± 2ms). The SDI of patients excluded was not significantly different from the cohort.
Conclusion: Mechanical dyssynchrony in basal circumferential contraction correlates with CMRI assessment of ventricular dysfunction in HLHS. It remains unclear whether mechanical dyssynchrony is a reflection or result of ventricular dysfunction. No increase in mechanical dyssynchrony was observed in patients pre-Norwood compared to pre-BCPC.