In a patient with subclavian artery obstruction, what would be observed in the left vertebral artery waveform?

In a patient with a subclavian artery obstruction, the left vertebral artery may exhibit retrograde flow during systole due to collateral circulation. When the subclavian artery is obstructed, the blood flow to the affected side can be compromised. In an attempt to compensate for this decreased flow, blood may not move in the typical antegrade direction within the vertebral artery during systole. Instead, retrograde flow can occur as blood is redirected to maintain perfusion in the affected areas, particularly when the proximal segments of the subclavian provide insufficient supply.

This phenomenon illustrates the body's adaptive mechanisms in the presence of vascular obstruction. In contrast, antegrade flow would indicate normal perfusion, and a constant triphasic waveform is characteristic of healthy arterial circulation, typically observed in the periphery rather than in a compromised state. Additionally, an abnormal systolic window would suggest altered flow dynamics but does not specifically indicate retrograde flow.