Echocardiographic automated cardiac output measurement of pulmonary output and quantification of intracardiac shunt

Pulmonary Vascular Resistance Measurement Remains Keystone in Congenital Heart Disease Management

Pulmonary vascular resistance (PVR) plays a major role in congenital heart management and critical decision. The impact of pulmonary vascular disease in the early and late morbidity and mortality after cardiac surgery and interventional catheterization in congenital heart defect (CHD) highlights the importance of critical evaluation for PVR. Currently, PVR is evaluated with invasive cardiac catheterization for hemodynamic data collection, processing, and analysis. Despite the limitation of hemodynamic evaluation in the setting of CHD, accurate data analysis, and interpretation have significant impact on clinical outcome and procedure success. This article reviews the basic calculation of PVR in the setting of congenital heart disease with diagrammatic illustration for easy understanding of the hemodynamic.

Clinical utility of the ventricular septal defect diameter to aorta root diameter ratio to predict early childhood developmental defects or lung infections in patients with perimembranous ventricular septal defect

BACKGROUND

Ventricular septal defect (VSD) is the most frequent type of congenital heart disease. Conventional methods to evaluate VSD size and severity are both invasive and cumbersome to perform. We investigated whether the ratio between the diameter of the defect and the aortic root diameter (DVSD/DAR) would accurately reflect the degree of shunted blood and the severity of VSD in children with perimembranous VSD.

METHODS

We recruited 987 children with perimembranous VSD (pmVSD) and used color Doppler echocardiography to calculate DVSD/DAR. 987 healthy children were recruited as control group. The pmVSD group was further stratified into four groups according to age (1 to 4 y) and again into four groups according to the DVSD/DAR ratio: children whose DVSD/DAR was 1/5 to <1/4, 1/4 to <1/3, 1/3 to 1/5, or 1/2 to <2/3 were assigned to groups A, B, C, and D, respectively. Height, weight, infection scores and systemic-pulmonary circulation ratio (QP/QS ratio) were compared among groups A, B, C and D. Then the relationship between the DVSD/DAR ratio and height, weight, QP/QS ratio, infection score were analysed by linear regression analysis.

RESULTS

Compared to age-matched children without VSD (the controls), the mean height and weight of children in the pmVSD group were lower, and heights and weights were negatively correlated with the DVSD/DAR ratio. This ratio was significantly reduced in groups C and D compared to control group (both P<0.05). Infection scores of groups A and B were significantly higher only in the one-year-old subgroup, but were significantly higher in groups C and D for all ages compared to the control group (both P<0.05). QP/QS ratio of group C and D were higher than group A and group B (all P<0.05). Moreover, QP/QS ratio of group D for all ages were more than 2. In addition, linear regression analysis revealed that the DVSD/DAR ratio negatively correlated with height and weight and positively correlated with the QP/QS ratio and infection score.

CONCLUSIONS

Our results suggest that the DVSD/DAR ratio accurately reflects the growth and pulmonary infection rates in children with pmVSD. This ratio, therefore, may be a useful additional reference index to predict the consequences of pmVSD.

Cardiac output can be measured with the transpulmonary thermodilution method in a paediatric animal model with a left-to-right shunt

BACKGROUND

The transpulmonary thermodilution (TPTD) technique for measuring cardiac output (CO) has never been validated in the presence of a left-to-right shunt.

METHODS

In this experimental, paediatric animal model, nine lambs with a surgically constructed aorta-pulmonary left-to-right shunt were studied under various haemodynamic conditions. CO was measured with closed and open shunt using the TPTD technique (CO(TPTD)) with central venous injections of ice-cold saline. An ultrasound transit time perivascular flow probe around the main pulmonary artery served as the standard reference measurement (CO(MPA)).

RESULTS

Seven lambs were eligible for further analysis. Mean (sd) weight was 6.6 (1.6) kg. The mean CO(MPA) was 1.21 litre min(-1) (range 0.61-2.06 l min(-1)) with closed shunt and 0.93 litre min(-1) (range 0.48-1.45 litre min(-1)) with open shunt. The open shunt resulted in a mean Q(p)/Q(s) ratio of 1.8 (range 1.6-2.4). The bias between the two CO methods was 0.17 litre min(-1) [limits of agreement (LOA) of 0.27 litre min(-1)] with closed shunt and 0.14 litre min(-1) (LOA of 0.32 litre min(-1)) with open shunt. The percentage errors were 22% with closed shunt and 34% with open shunt. The correlation (r) between the two methods was 0.93 (P<0.001) with closed shunt and 0.86 (P<0.001) with open shunt. The correlation (r) between the two methods in tracking changes in CO (ΔCO) during the whole experiment was 0.94 (P<0.0001).

CONCLUSIONS

The TPTD technique is a feasible method of measuring CO in paediatric animals with a left-to-right shunt.