Table 1.

Essential echocardiographic requirements for assessing the hemodynamic significance of patent ductus arteriosus and transductal shunt volume

Echocardiographic indexes	Shunt volume
	Small	Moderate	Large
Patent ductus arteriosus dimension and flow
Diameter (mm)	<1.5	1.5–2.0	≥2.0
Flow direction (left to right, bidirectional with right to left ≤ or >30% of the cardiac cycle, right to left)	-	-	-
Transductal peak systolic velocity (m/sec)	>2.0	1.5–2.0	<1.5
Transductal systolic-to-diastolic velocity gradient	<2.0	2.0–4.0	>4.0
Pulmonary overcirculation
Left ventricular output (mL/kg/min)	<200	200–300	>300
Left heart volume loading: choose one parameter
Left atrium to aortic root ratio, left ventricular end-diastolic diameter (mm)	<1.5	1.5–2.0	>2.0
Pulmonary vein d wave velocity (cm/sec)	<0.3	0.3–0.5	>0.5
Left pulmonary artery end-diastolic velocity (cm/sec)	<20	20–50	>50
Left side pressure loading: choose one parameter
Mitral valve E to A wave ratio	<1	1	>1
Isovolumic relaxation time (msec)	>40	30–40	<30
Systemic shunt effect
Flow direction in one of the following postductal artery	Antegrade	Absent	Retrograde
Aorta descendant or
Celiac trunk
Middle cerebral artery (forward, absent, reversed)

Modified from de Boode WP, et al., Semin Fetal Neonatal Med 2018;23:292-7, with permission of Elsevier. [23]