589 - Determinants of bradycardia in adolescents and young adults with atypical anorexia nervosa: baseline findings from the individualized-Study of Refeeding to Optimize iNpatient Gains (iStRONG)

Publication Number: 589.4304

Megen Vo, Stanford University School of Medicine, Palo Alto, CA, United States; Neville H. Golden, Stanford University School of Medicine, Palo Alto, CA, United States; Cynthia j.. Kapphahn, Stanford University School of Medicine, Palo Alto, CA, United States; Anna Kreiter, Stanford University School of Medicine, Palo Alto, CA, United States; Brooke Marsal, Lucile Packard Children's Hospital Stanford, Palo Alto, CA, United States; Kristene Hossepian, Stanford University School of Medicine, Mountain View, CA, United States; Amanda E. Downey, University of California, San Francisco, School of Medicine, San Francisco, CA, United States; Sara M. Buckelew, UCSF Benioff Children's Hospital San Francisco, Oakland, CA, United States; Andrea K. Garber, University of California, San Francisco, School of Medicine, San Francisco, CA, United States; Daniel Le Grange, UCSF Benioff Children's Hospital San Francisco, San Francisco, CA, United States; Louie M. Swander, University of California, San Francisco, School of Medicine, San Francisco, CA, United States; Arjun S.. Mehta, UCSF Benioff Children's Hospital San Francisco, Berkeley, CA, United States; Sasha Gorrell, PhD, University of California, San Francisco, School of Medicine, San Francisco, CA, United States; Anna Barbara Moscicki, University of California, Los Angeles David Geffen School of Medicine, Los Angeles, CA, United States

Background: Atypical anorexia nervosa (AAN) describes individuals who meet all criteria for anorexia nervosa (AN) except that despite significant weight loss, weight is in the normal or above normal range. As with AN, they may require medical hospitalization for vital sign instability. In AN, bradycardia and low weight are the most frequent reasons for hospitalization. We previously reported that rate of weight loss predicted degree of bradycardia, independent of admission weight.

Objective: To examine relationship between bradycardia and hypometabolism in adolescents and young adults (AYA) with AAN hospitalized for medical stabilization.

Design/Methods: Eligible participants were AYA aged 12 -24 years with AAN hospitalized for medical stabilization at two tertiary care pediatric hospitals, and enrolled in a randomized-controlled trial of refeeding in AAN. Diagnosis was determined by a child psychiatrist or psychologist. Inclusion criteria were weight > 85% median body mass index (%mBMI) and > 10% weight loss. Exclusion criteria were bulimia nervosa and ARFID. Duration of illness (mo.), amount of weight loss (kg), rate of weight loss (kg/mo.), demographic factors (age, race, gender), anthropometric measures (height, weight, BMI), and lab values including serum tri-iodothyronine (T3) were obtained on admission. Resting energy expenditure (REE, kcals/24h) was measured fasting the morning after admission and expressed as %predicted REE (%PREE) based on the Harris-Benedict equation. Lowest sustained heart rate (HR) was defined as the lowest HR sustained for at least 5 mins on cardiac telemetry on the first night of admission. Linear regression analyses of this preliminary baseline data examined the relation among lowest HR and admission %mBMI, amount of weight loss, rate of weight loss, T3 and %PREE.

Results: Of 61 participants enrolled, 3 withdrew leaving 58 active participants, mean age 15.1 ±16y, 48 F, 8 M, 2 transmale. Admission %mBMI was 96.4±11.3 and pulse nadir 41.0 ± 7.1 bpm. Bradycardia was the indication for hospitalization in 79.3% (46/58). In bivariate analyses, amount of weight loss, rate of weight loss, and admission %mBMI were not associated with lowest HR, but both T3 (p =.001) and %PREE (p =.002) were significantly related to lowest HR. Using stepwise regression, T3 was independently associated with lowest HR (β=.558, p<.001). The addition of %PREE did not contribute to the final model (p =.078).

Conclusion(s): Bradycardia was the most frequent reason for hospitalization in AYA with AAN and lowest HR on the first night of hospitalization was most strongly associated with T3 on admission.