Pulmonary hypertension during acute respiratory diseases in infants

The study was undertaken to assess whether previously healthy infants with acute respiratory diseases develop elevated pulmonary artery pressures and to identify which type of disease is associated with pulmonary hypertension.

We performed 2D and Doppler echocardiography in 137 infants, aged between 1 and 12 month, from November 2007 to December 2009. 75 infants had acute respiratory diseases (49 bronchiolitis, 16 interstitial pneumonia, 3 bronchopneumonia, 6 episodic wheezing, 1 lobar pneumonia) and 62 were in the control group. We excluded children with congenital heart diseases and other conditions associated with pulmonary hypertension. The method of time to peak velocity corrected for heart rate was used to estimate pulmonary arterial pressure (PAP). We analysed 2 age-subgroups: 1-2 months and 2-12 months. A Student's t-test for independent samples was used to compare the mean values of variables.

Increased mean pulmonary pressures (>25mmHg) were measured in 18 infants with respiratory diseases, with the next distribution: 14 bronchiolitis, 2 bronchopneumonia, 1 episodic wheezing, 1 interstitial pneumonia. The values were categorized as mild-moderate pulmonary hypertension. Mean PAP were significantly increased in subjects with clinically bronchoobstructive disease (bronchiolitis, episodic wheezing, bronchopneumonia) vs. control (p=0.05 in first age-subgroup and<0.001 in second age-subgroup). In infants with bronchoobstructive disease hospitalization was significantly longer in patients with pulmonary hypertension vs. normal PAP (p= 0.04 in first age-subgroup and 0.005 in second age-subgroup). In patients with bronchoobstructive diseases, mean PAPm and PAPs were significantly increased in subjects with a moderate/severe episode of wheezing at admission vs. a mild episode (p=0.02). Mean PAPm and PAPs were increased in subjects with interstitial pneumonia vs. control, but without statistic significance.

Echocardiography is a non-invasive investigation, which brings valuable information regarding pulmonary hypertension in infantile acute respiratory pathology. We found increased PAP almost exclusively in bronchoobstructive diseases; the mechanic effect of hyperinflation on pulmonary vessels is probably the dominant mechanism. PHT could be a criterion in establishing the severity of an acute wheezing episode, a prognosis factor and an element of therapeutic guidance.