Color flow mapping to document normal pulmonary venous return in neonates with persistent pulmonary hypertension being considered for extracorporeal membrane oxygenation

Changes in pulmonary venous flow pattern during early neonatal life

OBJECTIVE

To investigate serial changes in the pattern of flow in the pulmonary vein during the early neonatal period.

METHODS

Pulsed Doppler echocardiography was used to measure flow in the right upper pulmonary vein in 26 normal newborn infants. Peak flow velocity during systole (S) and diastole (D) and flow velocity at indents between the systolic and diastolic fraction (O) and between the diastolic and systolic fraction (X) were measured 1, 4-8, 24, and 96 hours after birth. The heart rate and diameter of the ductus arteriosus were measured simultaneously.

RESULTS

Continuous and phasic high flow velocity waveforms were seen 1 and 4-8 hours after birth. The mean (SD) peak flow velocities of X, S, O, and D an hour after birth were 35.2 (13.6) cm/s, 73.1 (23.1) cm/s, 58.5 (20.5) cm/s, and 81.5 (19.2) cm/s respectively. There were significant decreases in X, S, O, and D by 24 hours of age (p < 0.01 v 1 hour after birth) to 8.1 (10.3) cm/s, 52.8 (18.0) cm/s, 38.6 (14.5) cm/s, and 54.4 (11.2) cm/s respectively. These results indicate intermittent flow in the pulmonary vein, with flow stopping between diastole and systole. These flow velocities, X, S, O, and D, correlated well with the diameter of the ductus arteriosus (r = 0.80 v X, r = 0.62 v S, r = 0.63 v O, r = 0.75 v D).

CONCLUSION

This serial study showed changes in normal pulmonary vein flow patterns during the early neonatal period. The continuous and high flow velocity waveform that was seen immediately after birth resembled the pattern of pulmonary vein flow seen in congenital pulmonary stenosis and in cases of acute volume overload. This waveform may reflect a sudden increase in pulmonary circulatory volume with additional left to right shunting through the ductus arteriosus in relatively hypoplastic pulmonary veins.

Verification bias in pediatric studies evaluating diagnostic tests

Improperly designed evaluations of diagnostic tests may lead to inaccurate conclusions about a test's accuracy. One problem, verification bias, occurs if subjects are not equally likely to have the diagnosis verified by a gold-standard evaluation and if selection for further evaluation is dependent on the diagnostic test result. To determine whether verification bias is a problem in pediatric studies of diagnostic tests, we conducted a critical appraisal of all studies evaluating diagnostic tests published in three pediatric journals during a 3-year period. Thirty-six percent were subject to verification bias. The most prevalent cause was restriction of the patient sample to those whose diagnosis had been verified by a gold standard evaluation, when the decision to obtain the gold standard was influenced by the diagnostic test result. Verification bias may have serious effects on the estimated sensitivity and specificity of a test. Improved awareness of the potential for verification bias may help physicians improve their selection and interpretation of diagnostic tests and thereby improve the quality and efficiency of patient care.

When is echocardiography unreliable in patients undergoing catheterization for pediatric cardiovascular disease?

Technologic advances in echocardiography (e.g., better spatial resolution, Doppler, and color flow mapping) have improved our ability to demonstrate anatomy and physiology in previously problematic conditions, precluding catheterization and angiography in some instances. However, diagnostic catheterization remains necessary in other instances. The aims of this study were to determine whether echocardiography alone was sufficient to delineate the anatomic and flow abnormalities in patients subsequently selected to undergo catheterization and, if not, under what circumstances was echocardiography unable to establish the definitive diagnosis. Echocardiograms of 252 infants and children who underwent catheterization during a 14-month interval were analyzed retrospectively to determine whether the echographic assessment was nondiscrepant (group 1) or discrepant (group 2) with the catheterization assessment. Any deviation in the complete accurate assessment constituted a discrepancy; identification of more than one discrepancy in a single patient was possible. Independent variables included patient's age, weight, operative status, use of color flow mapping, echocardiograph operator, and interval between echocardiogram and catheterization. To determine whether the discrepancies were clinically significant, data from patients in group 2 were reviewed independently by three cardiologists to determine whether patient management would have changed given the added data provided by catheterization. Echocardiographic evaluations were discrepant in 155 instances. In 54 of 155 instances (35%), discrepancies were judged to be clinically significant (group 3). Twenty-three of 54 cases (43%) involved extracardiac lesions (i.e., aortic arch, pulmonary arterial, bronchial collateral, and pulmonary venous anomalies), 20 of 54 (37%) involved pressure gradients, 7 of 54 (13%) involved intracardiac lesions, and 4 of 54 (7%) involved coronary arterial lesions.(ABSTRACT TRUNCATED AT 250 WORDS)