Noninvasive assessment of pulmonary arterial capacitance by pulmonary annular motion velocity in children with ventricular septal defect

Abstract

Background: We hypothesized that longitudinal pulmonary arterial deformation during the cardiac cycle reflects pulmonary arterial capacitance. To examine this hypothesis, we assessed whether tissue Doppler-derived pulmonary annular motion could serve as a novel way to evaluate pulmonary arterial capacitance in pediatric patients with ventricular septal defect (VSD).

Methods: In this prospective study, pulmonary annular velocity was measured in children (age, 6 months-5 years) with a preoperative VSD (VSD group, n = 35) and age-matched healthy children (Control group, n = 23). Pulmonary artery capacitance was calculated by two methods. Systolic pulmonary arterial capacitance (sPAC) was expressed as the stroke volume/pulmonary arterial pulse pressure. Diastolic pulmonary arterial capacitance (dPAC) was determined according to a two-element windkessel model of the pulmonary arterial diastolic pressure profile.

Results: Pulmonary annular velocity waveforms comprised systolic bimodal (s1' and s2') and diastolic e' and a' waves in all participants. The peak velocities of s1', s2', and e' were significantly lower in the VSD group than in the Control group. On multiple regression analysis, sPAC was an independent variable affecting the peak velocities of the s1', s2', and e' waves (β = 0.41, 0.62, and 0.35, respectively). The dPAC affected the s1' wave peak velocity (β = 0.34). The time durations of the s1' and e' waves were independently determined by the sPAC (β = 0.49 and 0.27).

Conclusion: Pulmonary annular motion velocity evaluated using tissue Doppler is a promising method of assessing pulmonary arterial capacitance in children with VSD.

Keywords: Children; Pulmonary annular motion; Pulmonary arterial compliance; Tissue Doppler imaging.

Fig. 1

Recording of pulmonary annular motion velocity and measurement of pulmonary arterial capacitance. A representative recording of pulmonary annular motion evaluated by tissue Doppler imaging in a healthy 2-year-old boy is shown. The long-axis view of the right ventricular outflow tract and main pulmonary artery (PA) is visualized, and the sample volume is positioned on the RV free wall side of the pulmonary annulus, as indicated by the yellow arrow (a). Pulmonary annular velocity of the RV free wall side is determined (b). The tricuspid annular motion waveform from the same individual is also evaluated for the sake of comparison (c). The tissue Doppler-derived annular velocity waveform comprises s1′, s2′, e’, and a’ for the pulmonary annulus, and s’, e’, and a’ for the tricuspid annulus. Simultaneous recordings of pulmonary annular motion and RV and PA pressure curves in a 4-year-old girl with a ventricular septal defect (VSD) are shown (d). The measurements of systolic pulmonary arterial capacitance (sPAC) and diastolic pulmonary arterial capacitance (dPAC) are shown (e). The calculations to obtain sPAC and dPAC are described in the methods section. The comparison between sPAC and dPAC is shown in panel f. Boxes show the distribution (25th and 75th percentiles; central line, median). Vertical lines represent the range between the 5th and 95th percentiles. The relationship between sPAC and dPAC is shown in panel g. Ao, aorta; PA, pulmonary artery; RV, right ventricle; ICT, isovolumic contraction time; IRT, isovolumic relaxation time; sPAC, systolic pulmonary arterial capacitance; dPAC, diastolic pulmonary arterial capacitance; SPAP, systolic pulmonary arterial pressure; DPAP, diastolic pulmonary arterial pressure; PAPP, pulmonary arterial pulse pressure

Fig. 2

Comparison of pulmonary annular and tricuspid annular motion velocities between the Control group and the VSD group. The comparison is shown in terms of peak velocity (a–d) and time duration (e–j). Boxes show the distribution of peak velocity (25th and 75th percentiles; central line, median). Vertical lines represent the range between the 5th and 95th percentiles. ICT, isovolumic contraction time; IRT, isovolumic relaxation time

Fig. 3

The relationship between the pulmonary annular motion waveform and systolic pulmonary arterial capacitance (sPAC) in the VSD group. The relationship was evaluated in terms of peak velocity (a–d) and time duration (e–j) in each wave. There are significant correlations between the peak velocities of pulmonary s1′, s2′, e’, and sPAC (a–c). The pulmonary s1′, e’, and a’ wave durations are significantly correlated with sPAC (g, i, and j, respectively). Linear regression lines with 95 % confidence interval (dashed lines) are indicated. sPAC, systolic pulmonary arterial capacitance; ICT, isovolumic contraction time; IRT, isovolumic relaxation time

Fig. 4

The relationship between the pulmonary annular motion waveform and diastolic pulmonary arterial capacitance (dPAC) in the VSD group. The relationship was evaluated in terms of peak velocity (a–d) and time duration (e–j) in each wave. There are significant correlations between the peak velocities of pulmonary s1′, s2′, e’ and dPAC (a–c). The e’ wave duration is significantly correlated with dPAC (I). Linear regression lines with 95 % confidence interval (dashed lines) are indicated. dPAC, diastolic pulmonary arterial capacitance; ICT, isovolumic contraction time; IRT, isovolumic relaxation time