236 - Impact of Therapeutic Hypothermia on Echocardiography Indices of Pulmonary Hemodynamics

Poster Number: 236
Publication Number: 236.222

Angelica M. Vasquez, UIOWA, Coralville, IA, United States; Adrianne Rahde Bischoff, University of Iowa, Iowa city, IA, United States; Patrick J. McNamara, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA, United States; Regan E. Giesinger, University of Iowa, Iowa City, IA, United States

Background: Impaired right ventricular (RV) function is independently associated with mortality, brain injury and adverse neurodevelopmental outcome in patients with hypoxic-ischemic encephalopathy (HIE) undergoing Therapeutic Hypothermia (TH). Animal literature suggests that TH has a negative modulator effect on pulmonary vascular resistance (PVR) however, human neonatal studies are not available.

Objective: To elucidate the modulator role of TH on pulmonary hemodynamics, ventricular performance among HIE patients undergoing TH.

Design/Methods: Neonates >34 weeks’ gestation (GA) with a diagnosis of moderate-severe HIE, treated with TH (11/2019 to 10/2020), where targeted neonatal echocardiography (TnECHO) before and within 2h of achieving target temperature (33.5° C). Images were analyzed by a single evaluator and cardiovascular management was at the discretion of the medical team. The primary outcome was systolic eccentricity index (sEI), which positively correlates with pulmonary artery (PA) pressure. Based on preliminary data, for a desired power of 0.9 and a Type I error of 0.01, a sample size of 9 patients was needed to detect a 20% difference in systolic eccentricity index (sEI). Univariate analysis was performed.

Results: A total of 14 patients were evaluated during the study period, of which 10 satisfied eligibility criteria [Exclusions: n=3 due to 2nd TnECHO >2h after target temperature; n=1 insufficient imaging windows]. Patients were equally distributed between moderate and severe encephalopathy [Table 1]. At baseline, 2 patients (20%) were treated with empiric low dose epinephrine at doses of 0.03 and 0.08mcg/kg/min and no infants were receiving nitric oxide; no change in cardiovascular therapy occurred between TnECHOs. Minor clinical changes occurred [Figure 1, Table 2]. Initiation of TH was followed by an increase in sEI (p=0.01) [Figure 1]. Other indices of pulmonary hemodynamics [notching of PA doppler (p=0.016), ratio of right ventricular ejection time to PA acceleration time (PAAT) (p=0.02), and %right-to-left transductal shunt (p=0.01) also worsened. [Table 2] Both RVO (p=0.02) and LVO (p=0.02) fell. Although a trend towards lower tricuspid annulus plane systolic excursion (TAPSE) was noted, TAPSE:PAAT was unchanged reflecting preservation of RV-PA coupling. [Table 2]Conclusion(s): In neonates with HIE, TH is associated with increased PA pressure and worsening pulmonary hemodynamics but with negligible impact on cardiac function. Caution is advised when initiating TH among patients with clinically significant pulmonary hypertension.
Table 1 - Patient Characteristics
Table 2 - Pre and Post TH Clinical and Echocardiography Measures of Pulmonary Hemodynamics, RV and LV performance