Case - RV Hypertrophy and Diastolic Dysfunction

Case by Dr Floriane Brief - Neonatal Hemodynamics Fellow at CHU-Sainte-Justine and Dr. Gabriel Altit - Neonatologist at the Montreal Children's Hospital.

Abstract: We present a challenging case of a preterm infant with asphyxia, born at 26 weeks, who experienced hypoxic respiratory failure secondary to severe right ventricular hypertrophy, leading to a right to left shunt at the atrial level. This led to hypoxic blood enteric the systemic circulation, decreased pulmonary blood flow from low RV output and decreased left ventricular preload. This patient had a restrictive ductus, which was left to right on initial evaluation, when the patient was on 100% oxygen requirements with systemic saturations hovering in the high 70s. This case report outlines the use of prostaglandin to increase pulmonary blood flow to give time for the RV to remodel. With increasing pulmonary blood flow via the duct and increasing left atrial pre-load, the right to left shunting at the atrial level decreased and the baby was weaned to 30% FiO2 quite rapidly. The baby remained on PGE for 10 days, which were stopped once the right ventricular hypertrophy had recovered. Following which, the baby was extubated and placed on CPAP. 

Case Report: At 26 weeks, the mother experienced a rupture of membranes. A single dose of betamethasone was administered, and no signs of chorioamnionitis were observed. Due to significant fetal bradycardia, an emergency C-section was performed (birth weight of 900 grams and Apgar scores of 1-5-7). Umbilical cord blood gas analysis revealed a venous pH of 7.19 and an arterial pH of 6.88. Upon birth, the infant exhibited bradycardia (70 bpm) and required immediate Positive Pressure Ventilation (PPV) with FiO2 100%. Subsequently, the neonate was transferred to the Neonatal Intensive Care Unit (NICU) and placed on Continuous Positive Airway Pressure (CPAP) with a high level of oxygen requirements (60%). Within the first hour of life, the infant experienced episodes of desaturation (<50%) necessitating intubation and surfactant administration. After intubation, the baby initially received conventional mechanical ventilation and was later transitioned to High-Frequency Oscillatory Ventilation (HFOV) due to increasing FiO2 requirements (90%). Hemodynamically, the infant received a 10 mL/kg bolus of normal saline for borderline blood pressure and started on dopamine at 2.5 mcg/kg/min. Hydrocortisone was initiated at 1 mg q8h. Although there were no clinical signs of seizures, the newborn had a pH <7.2 for the first 6 hours of life (with progressive recovery), likely due to perinatal depression.

The neonate's clinical course presented numerous challenges, including persistent hypoxia, escalating oxygen requirements, and hemodynamic instability. On day of life 8, a targeted neonatal echocardiography (TNE) was requested, since the patient was on 100% oxygen requirements with systemic saturations of 75% in the pre and post-ductal limbs. At that time, the patient was only on hydrocortisone 0.5 mg/kg/dose intravenous q12hours (weaning) and on high frequency jet ventilation with high settings (mean airway pressure of 14). The CO2 was within the 40s and the pH was 7.32. The TNE revealed severe right ventricular (RV) hypertrophy, low RV output, a restrictive patent ductus arteriosus (left to right), and a strict right-to-left atrial shunt. Systolic function of the RV and LV remained preserved. To address the complex hemodynamics, w initiated prostaglandin E1 (PGE1) at 0.01 mcg/kg/min, resulting in an immediate reduction in oxygen requirements to 25-30% and significant ventilator weaning (mean airway pressure dropped to 10). Attempts to discontinue PGE were made but were unsuccessful due to rebound oxygen needs a few hours following cessation. The patient remained on PGE for 10 days until a repeat TNE indicated improved right ventricle filling and a large, left-to-right duct. PGE was then safely discontinued. One week and a half later, the baby was extubated and maintained on CPAP. This case emphasizes the intricate management required for neonates with complex hemodynamics contributing to hypoxic respiratory failure. Timely interventions, including the use of PGE1, played a crucial role in stabilizing the patient's condition. Further assessment and ongoing monitoring were planned to ensure optimal outcomes for this challenging neonatal case.

Initial assessment

Some patient with pulmonary atresia / severe stenosis may present with significant RV hypertrophy. Other patient may have such severe RV systolic dysfunction that it may not generate enough blood flow to open the pulmonary valve (often termed: "functional pulmonary valvular atresia"). Of interest - these patients have often ductal dependent pulmonary circulation (with a left to right shunt at the ductus allowing retrograde filling of the main pulmonary artery) - they do not have pre/post ductal saturation differences despite their significantly high PA afterload. Indeed, cases with functional pulmonary atresia often have concomitant high pulmonary vascular resistances, which led to the severely struggling RV. Some of these infants may start manifesting right to left shunting at the ductus once iNO is started (with pre-post saturation differences), since iNO may help decrease PVR which may improve RV output and lead to the right to left shunt by the ductus. 

 Apical 4 chamber views outlining that the RV is significantly hypertrophied with small residual RV diastolic cavity upon maximal filling. The Tricuspid and Mitral valves are opening and closing. This outlined that there is some blood flow that goes anterograde from the atriums to the corrresponding ventricles. 

By increasing pulmonary blood flow, one may increase left atrial pulmonary venous return and re-balance the pressures across the inter-atrial septum, which may improve forward flow from the RA to the RV, and eventually towards the RVOT and pumonary vasculature. This may limit the fraction of deoxygenated blood entering the systemic circulation at the atrial level. 

Follow-up TNE