[Risk factors for syncope in children with severe idiopathic pulmonary arterial hypertension]

Objective: To explore the risk factors for syncope in children with severe idiopathic pulmonary arterial hypertension (IPAH). Methods: Forty-four patients (age<18 years) with IPAH admitted to the Department of Pediatric Cardiology, Beijing Anzhen Hospital between May 2011 and October 2021 were retrospectively included. Patients were devided into syncope group and non-syncope group. Clinical manifestation and hemodynamic parameters including echocardiography, blood tests, right heart catheterization and acute pulmonary vascular expansion test were compared between two groups. Comparisons between groups were performed with unpaired Student t test, or Mann-Whitney U test or chi-square test. Logistic regression was used to calculate the odds ratio (OR) for parameters with statistically significant differences between groups and analyze the statistical correlation. Results: Among the 44 patients, 16 were males, the onset age was (7.2±3.9) years. Twenty-four (55%) children presented with 1 to 11 times of episodes of syncope, and 18 cases of whom induced by physical activity. Syncope group had a larger proportion of New York Heart Association (NYHA) heart function class Ⅲ-Ⅳ (67% (16/24) vs. 25% (5/20), χ²=7.59, P=0.006), higher brain natriuretic peptide (BNP) value ((251±39) vs. (61±40) pg/L, t=-2.18, P=0.035), higher pulmonary-to-aorta diameter ratio (1.6±0.4 vs. 1.4±0.2, t=-2.25, P=0.030) and larger pulmonary vascular resistance index ((22±11) vs. (16±7) WU/m², t=-2.13, P=0.039) compared with non-syncope group. The proportion of patent foramen ovale (4% (1/24) vs. 45% (9/20), χ²=10.36, P=0.001), left ventricular ejection fraction (LVEF) ((68±5)% vs. (72±8)%, t=2.23, P=0.031) and the positive rate of acute pulmonary vascular expansion test (8% (2/24) vs. 35% (7/20), χ²=4.77, P=0.029) of syncope group were significantly lower than those of non-syncope group. Multiple Logistic regression analysis showed that NYHA heart function Ⅲ-Ⅳ (OR=6.787, 95%CI 1.445-31.880), pulmonary vascular resistance index (OR=1.247, 95%CI 1.020-1.525) and BNP (OR=1.036, 95%CI 1.007-1.066) were independent risk factors for syncope. The patent foramen ovale (OR=0.010, 95%CI 0.000-0.586) was a protective factor for syncope. Conclusions: NYHA cardiac function grade, pulmonary vascular resistance index and BNP are independent risk factors for syncope. Patent foramen ovale is a protective factor for syncope. Exercise is the main inducement of syncope in children with IPAH.