The Use of Doppler Echocardiography for Detection and Estimation of Severity of Patent Ductus Arteriosus, Ventricular Septal Defect, and Atrial Septal Defect

Quantification of pulmonary/systemic shunt ratio by single-acquisition phase-contrast cardiovascular magnetic resonance

PURPOSE

Phase-contrast cardiovascular magnetic resonance (PC-CMR) quantification of intracardiac shunt (measuring the pulmonary to systemic flow ratio, Qp/Qs) is typically determined by measuring flow through planes perpendicular the pulmonary trunk (PA) and ascending aorta (Ao). This method is subject to error from presence of background velocity offsets and requires two scan acquisitions. We evaluated an alternate PC-CMR technique for quantifying Qp/Qs using a single modified plane that encompasses both the PA and Ao.

MATERIAL AND METHODS

In 53 patients evaluated for intracardiac shunting, PC-CMR measurement in the individual Ao and PA planes and also in a single-acquisition plane was obtained and Qp/Qs calculated by each method. Bland-Altman analysis was performed to evaluate the agreement between the two methods.

RESULTS

The 95% confidence limits of agreement ranged from -0.52 to +0.34 indicating good agreement between the two methods. There was excellent agreement on the clinically relevant threshold value of Qp/Qs ratio of 1.5 (representing criteria for surgical correction of shunt).

CONCLUSIONS

Qp/Qs determined from the single-acquisition approach agrees well with that of the individual PA and Ao method and offers potential improved accuracy (due to background velocity offset).

Pulmonary venous flow index as a predictor of pulmonary vascular resistance variability in congenital heart disease with increased pulmonary flow: a comparative study before and after oxygen inhalation

AIMS

There is no definitive and reliable echocardiographic method for estimating the pulmonary vascular resistance (PVR) to differentiate persistent vascular disease from dynamic pulmonary hypertension. The aim of this study was to analyze the relationship between the pulmonary venous blood flow velocity-time integral (VTIpv) and PVR.

METHODS AND RESULTS

Eighteen patients (10 females; 4 months to 22 years of age) with congenital heart disease and left to right shunt were studied. They underwent complete cardiac catheterization, including measurements of the PVR and Qp:Qs ratio, before and after 100% oxygen inhalation. Simultaneous left inferior pulmonary venous flow VTIpv was obtained by Doppler echocardiography. The PVR decreased significantly from 5.0 ± 2.6 W to 2.8 ± 2.2 W (P = 0.0001) with a significant increase in the Qp:Qs ratio, from 3.2 ± 1.4 to 4.9 ± 2.4 (P = 0.0008), and the VTIpv increased significantly from 22.6 ± 4.7 cm to 28.1 ± 6.2 cm (P = 0.0002) after 100% oxygen inhalation. VTIpv correlated well with the PVR and Qp:Qs ratio (r = -0.74 and 0.72, respectively). Diagnostic indexes indicated a sensitivity of 86%, specificity of 75%, accuracy of 83%, a positive predictive value of 92% and a negative predictive value of 60%.

CONCLUSION

The VTIpv correlated well with the PVR. The measurement of this index before and after oxygen inhalation may become a useful noninvasive test for differentiating persistent vascular disease from dynamic and flow-related pulmonary hypertension.

Uses and limitations of transthoracic echocardiography in the assessment of atrial septal defect in the adult

Two-dimensional and color Doppler echocardiography accurately detected the presence of an atrial septal defect (ASD) in 47 of 50 adults (mean age 40 years) confirmed by surgery or cardiac catheterization, or both. It correctly categorized all patients with ostium secundum and ostium primum ASD but misdiagnosed 3 of 5 patients with surgically proven sinus venosus ASD. The shunt flow volume across the ASD was calculated with the standard Doppler equation, and assuming the ASD to be circular correlated with shunt flow volume obtained by cardiac catheterization (r = 0.74). The maximum width of the color flow signals moving across the ASD was taken as its diameter. Mean flow velocity was determined either by placing a pulsed Doppler sample volume parallel to the flow across the ASD as visualized by color Doppler or by color M-mode examination, which allowed determination of flow velocities using a previously validated method that incorporates a computer analysis of pixel color intensity. The pulmonary to systemic blood flow ratio obtained by color-guided conventional Doppler interrogation of the left and right ventricular outflow tracts correlated poorly with cardiac catheterization results (r = 0.38). In patients with associated tricuspid regurgitation, the peak systolic pulmonary artery pressure obtained by color Doppler-guided continuous-wave Doppler correlated well with that obtained at cardiac catheterization (r = 0.89). The maximum color Doppler jet width of the flow across the ASD poorly correlated with ASD size estimated at surgery (r = 0.50).

Patency of foramen ovale--does it influence haemodynamics in newborn infants?

Colour-coded Doppler ultrasound examination was carried out in 37 healthy newborns at 24 h of age to determine the patency of the foramen ovale. In addition, Doppler-derived cardiac output was measured 5 times during the first 2 days of life in the same infants. Our aim was to examine the influence of foramen ovale on Doppler-derived cardiac output and its association with left-to-right shunting through the ductus arteriosus. In 22 infants the foramen ovale was patent at 24 h of age and in 15 it was closed. Haemodynamic variables measured using non-imaging Doppler-ultrasonic methods did not differ between these two groups. The closure of left-to-right shunt at the ductus was similar in both groups. In a follow-up examination at the age of 1 year, one child had an open foramen ovale without haemodynamic consequences. This study provides evidence that patency of foramen ovale does not influence hemodynamics in early infancy.

Doppler echocardiographic evaluation of congenital cardiac disease. An introduction

M-mode and two-dimensional echocardiography have greatly enhanced the evaluation of animals with congenital cardiac disease. Structural abnormalities can be seen and hemodynamic alterations inferred, e.g., ventricular wall concentric hypertrophy indicating pressure overload to the respective ventricle. Interrogation of the diseased heart by Doppler echocardiography allows acquisition of more direct hemodynamic information without cardiac catheterization, which enables the clinician to give a more precise description of a congenital abnormality. The purpose of this study is to illustrate and describe abnormal blood-flow patterns in selected congenital cardiac defects in animals. Basic background information concerning Doppler echocardiographic principles, flow patterns, and calculations will be briefly discussed. For more detailed descriptions other references should be sought. Interpretation of Doppler echocardiography in animals is based primarily on data derived from human studies since studies involving measurable numbers of veterinary patients have not yet been completed.

Two-dimensional Doppler echocardiographic flow imaging--exploration of clinical impact and problems

Recent advances in electronic engineering have allowed Doppler echocardiography to be presented in the form of a real-time two-dimensional image. The resulting image of blood flow has been described as a 'non-invasive angiogram', but the analogy with angiography should not be pushed too far since the technical determinants of these images are entirely different. Nevertheless, the colour flow map does allow rapid and direct exclusion, detection and quantitation of regurgitant and stenotic lesions, and semi-quantitative assessment of valvular regurgitation and shunts. To achieve optimum results, it is necessary to standardise recording procedure, to take account of patient variables which influence the image appearance and quality and to be aware of the possibility of artefact. As for all investigations, results which are not coherent with other echocardiographic data, with other investigations and with the clinical assessment should be subjected to particular scrutiny with the possibility of false diagnosis in mind.