Altered hemodynamics by 4D flow cardiovascular magnetic resonance predict exercise intolerance in repaired coarctation of the aorta: an in vitro study.

BACKGROUND: Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair. Altered flow patterns have been identified due to abnormal aortic arch geometry. Our previous work demonstrated aorta size mismatch to be associated with exercise intolerance in this population. In this study, we studied aortic flow patterns during simulations of exercise in repaired CoA using 4D flow cardiovascular magnetic resonance (CMR) using aortic replicas connected to an in vitro flow pump and correlated findings with exercise stress test results to identify biomarkers of exercise intolerance. METHODS: Patients with CoA repair were retrospectively analyzed after CMR and exercise stress test. Each aorta was manually segmented and 3D printed. Pressure gradient measurements from ascending aorta (AAo) to descending aorta (DAo) and 4D flow CMR were performed during simulations of rest and exercise using a mock circulatory flow loop. Changes in wall shear stress (WSS) and secondary flow formation (vorticity and helicity) from rest to exercise were quantified, as well as estimated DAo Reynolds number. Parameters were correlated with percent predicted peak oxygen consumption (VO2max) and aorta size mismatch (DAAo/DDAo). RESULTS: Fifteen patients were identified (VO2max 47 to 126% predicted). Pressure gradient did not correlate with VO2max at rest or exercise. VO2max correlated positively with the change in peak vorticity (R = 0.55, p = 0.03), peak helicity (R = 0.54, p = 0.04), peak WSS in the AAo (R = 0.68, p = 0.005) and negatively with peak WSS in the DAo (R = - 0.57, p = 0.03) from rest to exercise. DAAo/DDAo correlated strongly with change in vorticity (R = - 0.38, p = 0.01), helicity (R = - 0.66, p = 0.007), and WSS in the AAo (R = - 0.73, p = 0.002) and DAo (R = 0.58, p = 0.02). Estimated DAo Reynolds number negatively correlated with VO2max for exercise (R = - 0.59, p = 0.02), but not rest (R = - 0.28, p = 0.31). Visualization of streamline patterns demonstrated more secondary flow formation in aortic arches with better exercise capacity, larger DAo, and lower Reynolds number. CONCLUSIONS: There are important associations between secondary flow characteristics and exercise capacity in repaired CoA that are not captured by traditional pressure gradient, likely due to increased turbulence and inefficient flow. These 4D flow CMR parameters are a target of investigation to identify optimal aortic arch geometry and improve long term clinical outcomes after CoA repair.

Impact of Transcervical Ultrasound for the Diagnosis of Pediatric Peritonsillar Abscesses on Emergency Department Performance Measures.

OBJECTIVES: To evaluate the impact of transcervical ultrasound (US) as the initial imaging study for suspected peritonsillar abscesses (PTAs) on pediatric emergency department (ED) throughput measures. METHODS: A retrospective cohort study of patients evaluated for suspected PTAs between January 2009 and April 2017 was conducted. We compared the ED length of stay (LOS) before and after implementation of transcervical US to diagnose a PTA. The balancing measure was the rate of return visits within 2 weeks. RESULTS: There were 387 eligible patients over the study period. A total of 101 patients were evaluated for PTAs with computed tomography and 286 with US. The mean LOS was significantly less for patients who had US (347 minutes; 95% confidence interval [CI], 330, 364 minutes) compared to computed tomography (426 minutes; 95% CI, 392, 459 minutes), with an absolute difference of 79 minutes (95% CI, 44, 113 minutes). Patients who were evaluated with US did not have an increased rate of return visits (5.9% versus 8.0%; P = .66). CONCLUSIONS: The introduction of transcervical US was associated with a decrease of greater than 1 hour in the ED LOS for patients with suspected PTAs. Given the better radiation profile of US and no increase in the rate of return visits after its implementation, we propose the adoption of a transcervical US-first approach for the diagnosis of PTAs in pediatrics.

Right ventricular afterload in repaired D-TGA is associated with inefficient flow patterns, rather than stenosis alone.

Treatment of D- transposition of great arteries (DTGA) involves the Arterial Switch Operation (ASO), which can create PA branch stenosis (PABS) and alter PA blood flow energetics. This altered PA flow may contribute to elevated right ventricular (RV) afterload more significantly than stenosis alone. Our aim was to correlate RV afterload and PA flow characteristics using 4D flow cardiac magnetic resonance (CMR) imaging of a mock circulatory system (MCS) incorporating 3D printed replicas. CMR imaging and clinical characteristics were analyzed from 22 ASO patients (age 11.9 ± 8.7 years, 68% male). Segmentation was performed to create 3D printed PA replicas that were mounted in an MRI-compatible MCS. Pressure drop across the PA replica was recorded and 4D flow CMR acquisitions were analyzed for blood flow inefficiency (energy loss, vorticity). In post-ASO patients, there is no difference in RV mass (p = 0.07), nor RV systolic pressure (p = 0.26) in the presence or absence of PABS. 4D flow analysis of MCS shows energy loss is correlated to RV mass (p = 0.01, r = 0.67) and MCS pressure differential (p = 0.02, r = 0.57). Receiver operating characteristic curve shows energy loss detects elevated RV mass above 30 g/m2 (p = 0.02, AUC 0.88) while index of PA dimensions (Nakata) does not (p = 0.09, AUC 0.79). PABS alone does not account for differences in RV mass or afterload in post-ASO patients. In MCS simulations, energy loss is correlated with both RV mass and PA pressure, and can moderately detect elevated RV mass. Inefficient PA flow may be an important predictor of RV afterload in this population.

Pediatric Residency Point-of-Care Ultrasound Training Needs Assessment and Educational Intervention.

Background Prior studies showed that point-of-care ultrasound (POCUS) training is not commonly offered in pediatric residency. We assessed the need for a pediatric POCUS curriculum by evaluating pediatric trainees' attitudes toward the use of POCUS and identifying barriers to training. We also aimed to evaluate the impact of a POCUS educational intervention on self-efficacy and behavior. Methods We conducted a cross-sectional survey of pediatric residents in a single large freestanding children's hospital distributed via an institutional listserv and administered online. The survey included opinion-rating of statements regarding POCUS and barriers to training. We also offered a two-week POCUS course with online modules and hands-on scanning. Participating residents completed pre- and post-course knowledge assessments and follow-up surveys up to 12 months following the course to assess POCUS use and self-report confidence on POCUS indications, acquisition, interpretation, and clinical application. Results Forty-nine respondents were included in the survey representing all three pediatric levels with 16 specialty interest areas. Ninety-six percent of trainees reported that POCUS is an important skill in pediatrics. Ninety-two percent of trainees reported that residency programs should teach residents how to use POCUS. The most important perceived barriers to POCUS training were scheduling availability for POCUS rotations and lack of access to an ultrasound machine. Fourteen participants completed the pre- and post-course knowledge tests, with eight and six participants also completing the six- and 12-month follow-up surveys, respectively. Self-ratings of confidence were significantly improved post-intervention in indications (P = 0.007), image acquisition (P = 0.002), interpretation (P = 0.002), and clinical application (P = 0.004). This confidence improvement was sustained up to 6-12 months (P = 0.004-0.032). Participants also reported higher categorical POCUS use after course completion (P = 0.031). Conclusions Pediatric trainees perceive POCUS as an important skill, hold favorable opinions towards the use of POCUS, and support POCUS training within a pediatric residency. A POCUS course can improve resident POCUS knowledge, instill confidence, and motivate higher POCUS use. Further study is needed to evaluate POCUS applications in pediatric medicine to develop a standardized POCUS curriculum and establish a training guideline for pediatric residency.