Abstract 10622: Z Scores in Pediatric Cardiac Magnetic Resonance: Reclassification of Smaller, Younger Hearts with Novel Calculator

Abstract

Introduction: The use of z scores to describe growth of normal structures is necessary in the management of pediatric cardiac disorders, particularly in babies and toddlers. Z score calculators for cardiac magnetic resonance (CMR) have traditionally relied on a convenience sample given complexity of the test. A recently published, novel z score calculator from prospectively-imaged, awake, healthy children ages 0-12 years may add value to assessments of ventricular size compared to traditional calculators. Hypothesis: A novel z score calculator (“Olivieri et al”) with robust prediction in younger, smaller children may reclassify right and left ventricular end diastolic volumes and mass (RVEDV, LVEDV, LVM) compared to the traditional calculator (“Buechel et al”). Methods: A retrospective cohort of subjects less than 12 years of age who underwent clinical CMR imaging on a 1.5T scanner (n=96; median age 5.5 years (IQR 3.7-7.6 years); 42% female) was studied. Z scores were calculated using both novel and traditional models for RVEDV, LVEDV and LVM. Subjects were categorized into the agreement group (both calculators agree) or disagreement groups, where novel calculator reclassified to normal (z< ± 2) or abnormal (z> ±2). Reclassified subject characteristics were compared with ANOVA and t-test. Results: Novel and traditional z scores agreed for 77%, 58% and 62% of cases for RVEDV, LVEDV and LVM, respectively. Amongst disagreements, subjects reclassified from abnormal to normal by the novel calculator had significantly lower age, BSA and RV size (Table 1). Reclassified subjects showed no association with specific diagnoses. Conclusion: The novel z score calculator reclassifies younger, smaller children away from severe z scores into more normal z scores. Ventricular volume assessment is highly relevant to critical decision-making in the first years of life in borderline lesions.