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Blood Flow Across Intracardiac Shunts: Patent Ductus Arteriosus

You can see blood flow through a patent ductus arteriosus (PDA) from the left parasternal short-axis view and the high left parasternal view. In infants and children, the suprasternal and subcostal views may also provide adequate access to PDA flow. A PDA generally produces a left-to-right shunt, seen as turbulent blood flow that enters the left pulmonary artery and moves toward the main pulmonary artery. A PDA flow jet usually begins in systole, and persists throughout diastole. In patients with other associated cardiac anomalies, shunting can be right-to-left or bidirectional, depending on the pressures present. In a large shunt, you can see diastolic blood flow reversal in the descending aorta. Be aware that other defects can cause disturbed blood flow in the pulmonary artery. Use CFI in combination with spectral Doppler to precisely identify the source, direction, and timing of turbulent blood flow in the pulmonary artery. Summary Normal blood flow is usually laminar, although a small amount of turbulence adjacent to rapidly moving valves is common. Abnormal blood flow may be either laminar or turbulent. Thoroughly interrogate each blood flow area in all three dimensions by angling the transducer and using multiple imaging windows. In CFI, use any imaging view that allows you to see the structure in question.