Case - Left to right ductus in a premature infant

Case by Gabriel Altit (Neonatologist, Montreal Children's Hospital). September 2023. 

Case Report: A male preterm infant born at 28 weeks and 5 days gestation, weighing 1430 grams, was delivered via cesarean section due to maternal cervical insufficiency, which had been managed with a cerclage. Initially, the infant demonstrated stability on bubble continuous positive airway pressure (BCPAP) but subsequently developed worsening respiratory distress, necessitating endotracheal intubation at 4 hours of life. The baby received surfactant and was managed with high-frequency oscillatory ventilation (HFOV). Patient was initiated on caffeine therapy. The baby was successfully extubated on Day of Life (DOL) 2 and transitioned to BCPAP. Enteral feeding was initiated, and was increased to full per os, while weaning intravenous support. We assessed this patient on DOL 8. At this time, his systemic blood pressure was 49/24, the patient was 29+5 weeks corrected age and at a weight of 1340 grams. The patient was fully fed enterally with a total fluid intake (TFI) of 160 mL/kg/day. The patient was on BCPAP+5 on FiO2 21-23%. 

The infant was weaned to room air by DOL 40, corresponding to 34 weeks and 5 days corrected gestational age. Head ultrasound scans conducted at 3 days and 10 days of life revealed no abnormalities. Notably, no interventions for ductal closure were undertaken during the hospitalization, and the infant experienced an uncomplicated clinical course, with no instances of necrotizing enterocolitis, feeding intolerance, or renal issues. However, this case report outline that on day of life 8 the echocardiography demonstrated the presence of a left to right patent ductus arteriosus. The goal of this case report, is to outline all the measurements performed in the context of a PDA. Echocardiography repeat at 36 weeks corrected age demonstrated a spontaneously closed ductus with no presence of pulmonary hypertension.

PDA View

Here we can appreciate the PDA view in B-mode (bidimensionnal) as well as in Colour, simultaneously.

In these 3 pannels, we can see in 2D the course of the PDA. We can also appreciate the caliber of the left pulmonary artery in comparison.

The PDA must be measured at its narrowest point. Here 3 examples outlining that in various angle of the ductus, one may obtain variation in the caliber. Here we kept the smallest diameter (0.24 cm) in comparaison to the left pulmonary artery (0.27 cm).  Ratio of 0.89 (PDA/LPA). Ratio of 0.18 for PDA/body weight (1.8 mm/kg). 

Pulse Wave Doppler (on the left) and Continuous Wave Doppler (on the right) outlining that the left to right shunt is pulsatile and unrestrictive (diastolic velocities that are low, outlining rapid equalization of pressure between the Aortic and Pulmonary end). This means that the ductus is transmitting flow to the pulmonary circulation and the systemic pressure into the pulmonary compartiment, by the fact that the 2 circulations are connected by a lesion that does not restrict flow/pressure transmission. The Peak systolic velocity is 17 mmHg (outlining that the systolic pulmonary arterialpressure is 17 mmhg below the systemic systolic blood pressure). The end Diastolic velocity is 2 mmHg, outlining that the diastolic pressure in the pulmonary artery is 2 mmHg below the diastolic pressure in the aorta (near systemic because of the pressure equalization via the ductus).  Ratio of end diastolic to peak systolic velocity = 0.71/2.04 = 0.35

Parasternal views

Parasternal long axis view outlining that there is some trival mitral insufficiency, possibly secondary to the increase pulmonary venous return leading to left atrial dilation and mitral annulus dilation, which leads to some valvular loss of the coaptation. 

M-Mode in the PLAX for the LA/Ao ratio. The Ao is measured at the closure of the valve (0.76 cm). The LA is 1.13 cm. The ratio is 1.13/0.76 = 1.43. A value abouve 1.4 is considered to showcase increased LA dilatation (or decreased Aortic size, or a mix of both). 

Zoom on the aortic valve and LVOT.

Measurement of the LVOT diameter at 0.54 cm. 

Here the LV diastolic internal diameter is of 1.92 cm. Z-score of 3.32. Indiating that the LV is dilated. 

The left atrium is subjectively dilated, possibly secondary to the increased pulmonary venous return. 

Parasternal short axis. Subjective dilation of the LV.

View of the branch pulmonary artery. The RPA and the LPA measure 0.41 cm at their largest diameter.

Presence of continuous diastolic flow in the RPA and LPA. In the RPA at a velocity of 0.51 m/s. In the LPA at a end-diastolic velocity of 0.45 m/s.

Crab view of pulmonary veins

Here we visualize the right upper and lower pulmonary veins. Cursor on the right upper pulmonary vein. 

D wave velocity at 0.64 m/s in the right upper pulmonary vein

Visualization of the left upper and lower pulmonary veins

D wave velocity at 0.67 m/s in the left lower pulmonary vein

Cursor on the right lower pulmonary vein.

Velocity at 0.83 m/s (D velocity) in the right lower pulmonary vein.

Left upper pulmonary vein with a velocity at 0.48 m/s

Right upper pulmonary vein with a velocity of 0.37 m/s (lower value than estimated from the crab view). 

Apical views

LV and LA subjectively dilated in the apical 4 chamber view. 

Septal TDI: s' at 0.04 m/s, e' velocity at 0.04 m/s and a' at 0.08 m/s

End diastolic volume is 3.35 mL and end systolic volume at 1.22 mL. EF at 64% = (EDV-ESV)/EDV.

LV dilated by 3D echocardiography. RV within normal limit with appropriate function by 3D echocardiography.

Mitral insufficiency (trivial) by colour

Tapse of 9.2 mm (normal)

IVRT of 39.61 msec

E of mitral valve: 0.88 m/s; A of mitral valve of 0.70 m/s.

E/A ratio: 1.26

Left ventricular output

Here the VTI is 0.150 m in the LVOT

Here the heart rate is (60000/356.51) = 168 bpm

If you put the parameters in the Cardiac Output calculator, you obtain 385 mL/kg/min

Right ventricular output

The RVOT PW-Doppler may be contaminated by PDA flow in the PSAX or PLAX. Here we obtain the RVOT Doppler from the Apical view. Outlining that VTI just below the valve is 0.068 m.

RVOT measurement in the parasternal short axis view. Measurement at peak of systole at 0.70 cm. 

Example of the PW-Doppler at the RVOT in the PSAX. Here we obtain some contamination of the PDA flow, rendering more challenging the measurement of the VTI of the RVOT. 

Here the LVO/RVO ratio is 1.23

Subcostal view

Subcostal short-axis view outlining that the PFO is left to right with a high velocity (Nyquist / Velocity filter at 110 cm/s). This outlines that the Left to Right PFO shunt is under high velocity, possibly from the high LA pressure decompressing into the RA. LA may be under higher pressure due to excessive pulmonary blood flow from the PDA.

Re-demonstration of a PFO that is left to right under higher velocity.

CW-Doppler through the PFO outlines that there is a LA-RA gradient of 11 mmHg, indicating that the LA has 11 mmHg higher than the RA at its peak of pressure.

IVC view - the IVC is not dilated and collapses with breathing. 

View of the Celiac artery and Superior mesenteric artery.

Occasional retrograde flow in diastole in the superior mesenteric artery.

Occasional holodiastolic retrograde flow in the celiac artery.

Suprasternal View

Aortic arch showing to signs of hypoplasia or obstruction.

PW-Doppler showcasing Ascending Aortic blood flow velocities. 

One may appreciate here that there is no retrograde flow in diastole in the pre-ductal portion of the descending aorta. 

Contrary to the pre-ductal position, one may appreciate the holodiastolic retrograde flow in the post-ductal descending aorta. This outlines that the flow in the post-ductal aorta will retrogradely feed the pulmonary circulation during diastole. 

Cerebrovascular profile

Colour outlining the Anterior Cerebral Artery by trans-fontanel ultrasound

Here, the blood flow is maintained anterograde in systole and diastole.

PDA in context of Scoring Systems

Jain A, Shah PS. Diagnosis, Evaluation, and Management of Patent Ductus Arteriosus in Preterm Neonates. JAMA Pediatr. 2015 Sep;169(9):863-72. doi: 10.1001/jamapediatrics.2015.0987. PMID: 26168357.

Iowa Scoring System

Value for our case is 9. A value ≥ 6 is considered indicating echocardiographic signs of hemodynamics significance.

Scoring by El-Khuffash et al.

In RCT, infants with risk score of ≥5.0 deemed at high risk for chronic lung disease or death and were randomized. Please note that the score was done for evaluations performed in the first 48 hours of life. Our echocardiography was performed at 8 days of life. However, the score is 4 and predicts rightly that this patient is at low risk of chronic lung disease. This patient was free of respiratory support at 36 weeks. 

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