Background: Mechanical dyssynchrony is described in hypoplastic left heart (HLH). However the "normal" contraction pattern at each stage of palliation is not well understood. This prospective study aims to describe the ventricular contraction pattern in HLH prior to bidirectional cavopulmonary connection (BCPC).
Method: Fifteen infants (mean age 4.7±2.1mths) prior to BCPC (HLHS=11, unbalanced AVSD=4) with ECG, echocardiography and magnetic resonance imaging were analyzed. Longitudinal and circumferential global and segmental time to peak strain (tmS), time to peak strain rate (tmSR) and time to peak early systolic lengthening (tmEL) were measured from the 4 chamber and basal short axis view with speckle tracking imaging on commercially available software. All time variables were reported as a percentage of systole, and MRI volume and mass were indexed to body size. Standard deviation (SD) of tmS, tmSR and tmEL were calculated as a measure of synchrony.
Results: Ventricular contraction pattern is displayed in Figure 1. Significant linear relationship exists between RV mass/volume ratio and SD of both longitudinal tmSR (r=0.81,p<0.01) and tmS (r=0.52,p<0.05). Mass/volume ratio correlated to mass (r=0.69,p<0.01) but not to EDV. Systolic blood pressure was negatively related to stroke volume (r=-0.55,p<0.05) but no other RV volumetric parameters. QRS duration (77±13ms) had no significant correlations.
Conclusion: The sequence of systemic RV contraction is from apex to base, and at the basal level, from posterior to anterior. Longitudinal SD of tmSR and tmS may be a useful measure of dyssynchrony. Increased mass/volume ratio may reflect compensatory hypertrophy secondary to mechanical dyssynchrony in HLH.