Pulmonary hypertension in children and young adults with sickle cell disease
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Abstract
INTRODUCTION: Primary pulmonary hypertension (PH) is a progressive disease that is characterized by restricted blood flow in the pulmonary vasculature, resulting in an increase in pulmonary vascular resistance (PVR) (McLaughlin et al., 2009). Patients with sickle cell disease (SCD), a monogenic blood disorder that causes red blood cells to form a sickle shape and decreases their ability to carry oxygen to the body’s tissues, can develop secondary pulmonary hypertension. Although there is significant data showing that pulmonary hypertension secondary to SCD increases morbidity and mortality in adult patients, there is little information regarding how PH affects children with SCD (Klings & Machado et al., 2014). Although diagnosing PH requires right heart catheterization, the American College of Cardiology Foundation and the American Heart Association recommend using Doppler echocardiography as a screening test for PH (McLaughlin et al., 2009). A tricuspid valve regurgitant jet velocity (TRV) of 2.5 m/s or higher, measured by Doppler echocardiography, is suggestive of PH (McLaughlin et al., 2009). Because Doppler echocardiography is non-invasive, there is much more information available regarding TRV than right heart catheterization, an invasive procedure. This study examines the prevalence and incidence of elevated TRV (≥ 2.5 m/s) in children with SCD as well as factors that may be associated with an elevated TRV.
MATERIALS AND METHODS: We conducted a retrospective longitudinal cohort study chart review for 83 subjects followed by pediatric hematology at Boston Medical Center; examining demographic information, pediatric and adult echocardiogram reports, SCD complications previously identified as being related to PH, laboratory results that have previously been identified as being related to PH while each subject was between the ages of 8 and 30 between July 31, 2003 and June 30, 2015.
RESULTS: We found that 11 (13%) of our study population had one or more elevated TRV value (≥ 2.5 m/s). Elevated TRV values ranged from 2.5 – 2.83 m/s. The average age for elevated TRV was 15.9 years old. Of the subjects with elevated TRV 6 (55%) were taking HU, as compared to 53 (64%) of the general study population. No SCD complications previously reported to be related to PH were found to be significantly associated with elevated TRV in our study population. The only laboratory value that we found to be associated with elevated TRV was an elevate reticulocyte count, with an average value of 11% of red blood cells in subjects with elevated TRV and 8.41% of red blood cells in the general study population (p = 0.04).
DISCUSSION/CONCLUSION: We found that 13% of children with SCD had at least one screening echocardiogram with TRV ≥ 2.5 m/s, which is in agreement with the prevalence estimates of 10-20% published by the American Thoracic Society (Klings & Machado et al., 2014). However, this is much lower than the 30% reported in the literature (Kato, Onyekwere, & Gladwin, 2007). This may be caused by more widespread use of hydroxyurea therapy at our academic institution. We also found no associated factors other than elevated reticulocyte count, while other studies found associations with a history of sepsis/bacteremia, history of ACS, history of asthma, Hb SS genotype, low hemoglobin levels, and elevated reticulocyte count (Hagar et al., 2007; Minniti et al., 2009; Pashankar et al., 2008; Ambrusko et l., 2006; Kato et al., 2007)