Abstract
The use of resynchronization therapy for the treatment of left ventricular (LV) systolic dysfunction in children has been expanding. Because QRS duration is not a reliable indicator of the presence or severity of dyssynchrony in every case, additional methods of quantitation of dyssynchrony are needed. The purpose of this study was threefold: (1) to define normal values for LV real-time quantitative three-dimensional echocardiographic (3DE) dyssynchrony indices (DIs), (2) to analyze the feasibility and observer variability of 3DE DIs in a wide range of children, and (3) to determine the effects of age, heart rate, body surface area, and LV end-diastolic volume on these parameters. The two specific parameters studied were the standard deviation of the time to minimum systolic volume for the number of segments analyzed and the time difference between the earliest and latest contracting segments. Both parameters were expressed as a percentage of the cardiac cycle length. In 125 normal children aged 1 day to 19 years, adequate dyssynchrony studies were obtained in 102 (81.8%). The mean LV 3DE DIs expressed as the standard deviation of the time to minimum systolic volume for the number of segments analyzed were 1.16 ± 0.58 for 16 segments, 1.01 ± 0.60 for 12 segments, and 0.93 ± 0.68 for 6 segments. The mean LV 3DE DIs expressed as the time difference between the earliest and latest contracting segments were 3.80 ± 1.57 for 16 segments, 2.99 ± 1.42 for 12 segments, and 2.27 ± 1.35 for 6 segments. There were no effects of age, heart rate, body surface area, or LV end-diastolic volume on 3DE DIs. Intraobserver variability was 5.1%, and interobserver variability was 7.6%. Three-dimensional echocardiographic DI analysis is reproducible and feasible in most children. Three-dimensional echocardiographic DIs are not affected by growth-related parameters in children but are lower than previously reported adult values.
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