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2017-05-01  Premature constriction of the ductus arteriosus  © Sameh Abdel Latif Abdel Salam  www.TheFetus.net

Premature constriction of the ductus arteriosus
Sameh Abdel Latif Abdel Salam, M.D*; Mohammad Gibreel, M.Sc**; Islam Badr, M.Sc***;
 
*Radiology department, Kasr Alainy hospitals, Cairo University, Egypt;
**Aswan Heart Centre, Egypt;
*** Fetal medicine unit, Cairo University, Egypt.
 

Case report

A 28-year old woman (G1P0) was referred to our institution at 35 weeks and 3 days of gestational age for detailed fetal cardiac assessment after a previous diagnosis of fetal hypoplastic left heart syndrome one week earlier.
There was a history of maternal intake of potassium diclofenac two weeks before the scan with a high dose over a period of 5 days. 
Ultrasound examination revealed the following findings:

- Dilated RV showing thickened and hypertrophied free wall and interventricular septum with systolic and early diastolic septal bouncing. Severe ventricular discrepancy was noted attributed to RV dilatation and hypertrophy while the left ventricle appeared well formed with its anechoic lumen reaching cardiac apex denoting no evidence of left ventricular hypoplasia with normal LV free wall myocardial thickness. Mild cardiomegaly is noted with heart size (heart to chest area) reaching 0.42 

- Reduced RV contractility compared to normal LV contractility (evidenced by reduced tricuspid annular plane systolic excursion compared to normal mitral annular plane systolic excursion, however the estimated Tie index of the RV appeared on the upper limit of normal values (0.53) denoting still preserved overall systolic and diastolic function of the right ventricle enough to maintain rather normal RV stroke volume.

- Moderate early systolic tricuspid regurgitation with estimated peak velocity 1.7 m/sec.
 
- Dilated right atrium compared to left one with leftward bowing of the foramen ovale flap but not to the degree to form foramen ovale aneurysm (stretched foramen ovale flap attributed to elevated right atrial pressure secondary to tricuspid regurgitation). Normal right to left continuous flow across foramen ovale is also noted.

- Normal pulmonary valve appearance regarding leaflet thickness and free mobility with no evidence of infundibular, valvular or supra valvular stenosis. No significant valvular pulmonary regurgitation could be detected. 
 The main pulmonary artery appears dilated with good systolic distensiblity. Normal appearance of central pulmonary branches with no evidence of hypoplasia or focal tight stenosis. 

- The ductus arteriosus appeared small in size compared to main pulmonary artery or ascending aorta. Estimated angle corrected peak systolic velocity of the ductus arteriosus was 2.7 m/sec in its pulmonary end while 2.2 m/sec in the aortic end. 

- Normal appearance of both AV valves (mitral and tricuspid) regarding leaflet thickness and free mobility. Preserved biphasic inflow pattern (E/A) across tricuspid valve.

- Normal looking aortic valve leaflets with no evidence of aortic stenosis (whether sub valvular, valvular or supra valvular). Left sided aortic arch with no coarctation or significant collaterals.

- Normal systemic and pulmonary venous drainage. No evidence of anomalous pulmonary venous drainage, systemic venous drainage or persistent left SVC. 

- Subtle increase in pulsatility index of ductus venosus Doppler waveform with still positive A wave.
- Moderate, free pericardial effusion.

- Normal Doppler study of the examined umbilical artery (RI 0.45, PI 0.8). No evidence of fetal growth restriction. Estimated fetal weight was 2880 gm.


 

Images 1-6; videos 1-4: shows the hypertrophied dilated RV (RV remodeling) with apical trabecular hypertrophy making the RV rather of bipartite morphology, reduced tricuspid annular plane systolic excursion compared to that of mitral valve, pericardial effusion, vigorous LV free wall inward systolic motion rather due to the large septal contribution to RV systolic function, biphasic inflow pattern across tricuspid valve with early systolic moderate TR.

     


 
Image 7, video 5: show the normal connection and drainage of inferior pulmonary veins into left atrium excluding the presence of TAPVD, normal right to left forward flow through patent, stretched foramen ovale.

 



Images 8-18; videos 6-12: 2D and color Doppler views of the dilated MPA with good distensibility, absence of proximal RPA or LPA stenosis, constricted ductus arteriosus more at the pulmonary end, elevated peak systolic velocities in the ductus, rather normal ductus venosus waveform pattern.

         



Images 19-25; videos 13-17
: STIC acquired images and videos representing the turbulent flow in the apical and septal RV trabeculations,  Pericardial effusion, normal right to left forward flow across the FOV, tricuspid regurgitation, small ductus arteriosus and the good distensiblity of the LPA and the dilated MPA.

      



Image 25 and 27; video 18
: STIC acquired thick slice Glass Body rendered images and video showing the digital inflow across the hypertrophied apical RV trabeculations (making RV having bipartite morphology), dilated MPA and LPA compared to ductus arteriosus with absence of valvular pulmonary regurgitation.  

 

 

Our final diagnosis based upon imaging findings and maternal history of drug intake was premature constriction of the ductus arteriosus.
We recommended delivery within one week after our diagnosis. After delivery (4 days from our scan), the baby was admitted to NICU for 7 days managed by O2 therapy and pulmonary vasodilators and then discharged with good general condition and recommendation of follow up echocardiography 3 months later to re assess resolution of RV hypertrophy.


 
Discussion

Premature closure of the ductus arteriosus carries wide range of fetal and postnatal presentations; starting from mild asymptomatic disease with transient neonatal tricuspid and pulmonary regurgitation, passing by persistent pulmonary hypertension of the newborn ending by severe perinatal lethal condition (intra uterine death or early postnatal functional pulmonary atresia with consequent neonatal death). Several factors determine the postnatal presentation, the most important of which are fetal hydrops, complete ductal closure and the duration of prenatal ductal closure.
Premature ductal closure shows multi-level downstream consequences on different right heart structures (RA, RV, Pulmonary valve, MPA, central pulmonary arteries and peripheral pulmonary vascular bed). The overall pathologic findings are due to prenatal elevation of pulmonary systolic and diastolic pressures. While both fetal lung fields are fluid filled and show high resistive pulmonary vascular flow pattern, most of the RV stroke volume (about 90%) will be ejected through ductus arteriosus into systemic circulation, thus its premature constriction will eventually shift most of the RV output into both lung fields with significant pressure load exerted on the right ventricle. 
The pressure load on the RV will cause variable degrees of remodeling to overcome the sustained elevation of pulmonary pressures owing to both ductal closure and the high resistivity in fetal pulmonary vascular bed. Initially, adaptive concentric right ventricular hypertrophy will occur then systolic dysfunction (mainly the longitudinal shortening component with concurrent moderate to severe tricuspid regurgitation and consequent RA dilatation), leading to progressive RV dilatation pooling more blood to compensate for rather normal stroke volume till the degree where a decompensated RV failure occurs (elevated RV filling pressure “diastolic pressure” with systolic dysfunction and consequently severe pan systolic tricuspid regurgitation, monophasic filling across tricuspid valve, severe RA dilatation, severe systemic venous congestion and finally hydrops with decline in cardiac output).  This picture is prenatally reflected initially by the reversal of A wave in ductus venosus till reaching pulsatile flow pattern in umbilical vein itself with fetal hydrops carrying very high mortality risk at this stage. 
Shift of the RV output into the high resistive pulmonary circulation will lead to high volume load on both lungs carrying the risk of pulmonary vascular remodeling and postnatal persistent pulmonary hypertension of the newborn (PPHN) and functional pulmonary atresia. During fetal life, complete ductal closure, duration of closure as well as the progressive pulmonary regurgitation could be key features to define such neonatal risk. 
Premature ductal constriction also has an impact on pulmonary trunk and central pulmonary arteries with consequent pulmonary regurgitation and changes in pulmonary artery distensibility and degree of dilatation. Preserved good arterial distensibility reflects a favorable prognosis in early neonatal life , while progressive dilatation with poor distensibility carries a risk of neonatal bronchomalacia and air trapping.
In absence of fetal hydrops, the preserved RV function, incomplete ductal closure, the absence of pulmonary regurgitation as well as good pulmonary arterial distensibility represent good indicators of fetal and neonatal outcome. In our case, these markers were assessed to evaluate neonatal prognosis. The most important of which is preserved RV ejection capacity manifested by preserved normal Tie index and the early systolic TR (reflecting good systolic ejection capacity despite reduced longitudinal shortening component evidenced by reduced TAPSI compared to MAPSI) and the normal biphasic inflow pattern across tricuspid valve (reflecting still preserved normal filling pressure) with moderate RA dilatation but still no significant elevation of systemic venous pressure (Ductus venosus). The second important one is incomplete closure of ductus arteriosus for short duration reflecting still opened, yet stenotic, pathway for RV stroke volume into systemic circulation. The third one is the ability of pulmonary circulation to accommodate the increased pulmonary flow volume manifested by absence of pulmonary valvular regurgitation and the good distensiblity of main and central pulmonary arteries. According to fetal cardiovascular profile score, our case was given a score of 8 (due to presence of pericardial effusion and mild cardiomegaly) representing a good neonatal outcome.
In conclusion, study of all downstream effects of premature ductal constriction is of great importance prior to taking a decision about delivery time to avoid complicated neonatal chest condition and enhance early complete recovery.


References
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  2. Ishida, H., Kawazu, Y., Kayatani, F., & Inamura, N. (2016). Prognostic factors of premature closure of the ductus arteriosus in utero: a systematic literature review. Cardiology in the Young, 1-5.
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  4. Ghawi, H., Gendi, S., Mallula, K., Zghouzi, M., Faza, N., & Awad, S. (2013). Fetal left and right ventricle myocardial performance index: defining normal values for the second and third trimesters—single tertiary center experience. Pediatric cardiology, 34(8), 1808-1815.
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