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Cardiomyopathy in Adolescents and Adults with Barth Syndrome

BACKGROUND: Cardiomyopathy (CM) in Barth Syndrome (BTHS) is typically diagnosed in infancy and childhood. The most common form is dilated cardiomyopathy (DCM) with frequent left ventricular non-compaction (LVNC), although hypertrophic cardiomyopathy (HCM) is described. Natural history data suggests stabilization and even improvement in CM although death and transplant are common. Despite increased awareness of BHTS, cardiac phenotype and function in older patients is not well described.

METHODS: Individuals with BTHS age ≥15 years attending the Barth Syndrome Conference in 2016 and/or 2018 were included. Echocardiograms and ECG were performed; subjects provided medical history. Echocardiograms were performed using a standardized protocol evaluating cardiac phenotype, systolic and diastolic function and myocardial deformation. Subjects participating in clinical trials were excluded; subjects with heart transplants were excluded from cardiac analysis. For statistical analysis data is reported as median (IQR) or counts (percentages) in 2016 and 2018, respectively.

RESULTS: Eighteen subjects, age range 15.0 – 36.7 years including 2 heart transplants, were evaluated.  Left ventricle (LV) fractional shortening was 30% (26,34%) and 29.3% (27,34%), ejection fraction 56% (52,59%) and 55% (50,59%), average lateral/septal E:e’ ratio 8.03 (6.7,10.6) and 7.90 (6.9,93 ), global longitudinal strain -18.4 ( -19.4,-15.9) and -18.1  (-19.6,-16.5), and LVNC ratio 0.97 (0.73,1.5) and 1.18 (0.87,1.6). Body mass index was categorized as low in 47% and 50%, LV as dilated by volume in 33% and by dimension in 26% and 33%. Self-reported activity level corresponding to NYHA classes 1-4 were class 1 in only 7% and class 3 in 50% and 39%.  Heart transplant subjects reported activity class 2 and 3.  LVNC ratio >2 was present in 11%. One subject (6%) had HCM with the remainder having DCM or normal LV size with dysfunction (78%) or clinical history of DCM (16%). One subject had concern for restrictive DCM with left atrial enlargement and RV hypertension.  In 2016 the mean QTC was 436 (414, 445) with 2 subjects >450. Internal defibrillators were placed in 28%.

CONCLUSIONS: In older individuals living with BTHS the dominant phenotype is DCM with other forms also present. Primary cardiac features are borderline LV dilation and low normal systolic function by all measures.  Doppler data did not suggest frequent diastolic dysfunction. While some subjects have prominent trabeculations, only 11% met echo criteria for LVNC. Nearly 1/3 had a defibrillator.  BMI remains low in 50%. Despite nearly normal cardiac function as a group, many still have limited activity class, including transplanted subjects.

Shahryar Chowdhury, Mary Julia Buchanan, Tammy Churchill, Lanier Jackson, and Carolyn Taylor

Medical University of South Carolina

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