Decreased Pulmonary Arterial Compliance is a Predictor for Poor Outcomes in Infants with Isolated Atrial Septal Defect and Pulmonary Hypertension

Comprehensive assessments of pulmonary circulation in children with pulmonary hypertension associated with congenital heart disease

Pulmonary hypertension associated with congenital heart disease (CHD-PH) encompasses different conditions confounded by the left-to-right shunt, left heart obstruction, ventricular dysfunction, hypoxia due to airway obstruction, dysplasia/hypoplasia of the pulmonary vasculature, pulmonary vascular obstructive disease, and genetic variations of vasoactive mediators. Pulmonary input impedance consists of the pulmonary vascular resistance (Rp) and capacitance (Cp). Rp is calculated as the transpulmonary pressure divided by the pulmonary cardiac output, whereas Cp is calculated as the pulmonary stroke volume divided by the pulmonary arterial pulse pressure. The plots of Rp and Cp demonstrate a unique hyperbolic relationship, namely, the resistor-capacitor coupling curve, which represents the pulmonary vascular condition. The product of Rp and Cp is the exponential pressure decay, which refers to the time constant. Alterations in Cp are more considerable in CHD patients at an early stage of developing pulmonary hypertension or with excessive pulmonary blood flow due to a left-to-right shunt. The importance of Cp has gained attention because recent reports have shown that low Cp potentially reflects poor prognosis in patients with CHD-PH and idiopathic pulmonary hypertension. It is also known that Cp levels decrease in specific populations, such as preterm infants and trisomy 21. Therefore, both Rp and Cp should be individually evaluated in the management of children with CHD-PH who have different disease conditions.

Pulmonary vascular resistance and compliance in individuals with trisomy 18

Individuals with trisomy 18 (T18) usually have congenital heart disease, often with pulmonary hypertension, which is associated with poor outcomes. This study aimed to explore the characteristics of pulmonary circulation including pulmonary vascular resistance (Rp) and compliance (Cp) among them. We retrospectively reviewed cardiac catheterization data in subjects with T18, trisomy 21 (T21), and without chromosomal anomaly (control group) who were referred due to heart failure associated with ventricular septal defect between 2000 and 2020. Pulmonary hemodynamic parameters including Rp and Cp were compared between these groups. We studied 20 subjects with T18, 88 subjects with T21, and 240 control subjects. There was no significant difference in age (T18: 4.6 [3.0-6. 9] vs. T21: 2.8 [1.9-4.0] vs. control: 2.9 [1.6-3.2] months, p = 0.06) and mean pulmonary arterial pressure (T18: 41 [33-49] vs. T21: 35 [30-41] vs. control: 36 [28-43] mmHg, p = 0.121) between the groups. The pulmonary to systemic blood flow ratio (Qp/Qs) (p = 0.983), Rp (p = 0.449), and Cp (p = 0.195) did not differ between T18 and control groups. However, Qp/Qs and Cp in T18 group were significantly greater than that in T21 group (T18: Qp/Qs: 3.4 [2.3-5.2] vs. T: 21 2.3 [1.7-3.7], p = 0.001. Cp: 3.5 [2.3-5.5] vs. 2.3 [1.6-3.1] mmHg/mL/m² , p = 0.007), while Rp was identical between the groups (T18: 2.0 [1.6-3.3] vs. T21: 2.3 [1.7-3.7], p = 0.386). The pulmonary circulation in T18 subjects differed from that observed in T21 subjects, and identical to that observed in control subjects. Pulmonary hypertension is expected to be normalized after reasonable corrective surgery in T18 patients with congenital heart disease.