Diagnostic Significance of Monophasic Waveforms in Upper Extremity Arteries

Introduction to Monophasic Waveforms

The European Society of Cardiology recommends that monophasic waveforms detected in the right ulnar, left proximal, and mid subclavian arteries indicate significant arterial stenosis or obstruction proximal to the site of measurement, requiring urgent vascular imaging to identify the location and severity of occlusive disease 1, 2
Monophasic waveforms represent a pathologic dampening of normal arterial flow patterns and serve as a critical indirect marker of upstream obstruction, with normal arterial waveforms being triphasic or biphasic, reflecting the pulsatile nature of arterial flow 3

The 2024 ESC Guidelines state that monophasic post-stenotic waveforms detected by duplex ultrasound indicate significant subclavian stenosis, with 50% stenosis corresponding to peak systolic velocity ≥230 cm/s and 70% stenosis to PSV ≥340 cm/s 1, 2
Proximal subclavian stenosis or occlusion is most commonly atherosclerotic in origin, and the risk of subclavian steal syndrome is high, where >90% of patients with at least 50% proximal subclavian stenosis demonstrate vertebral artery flow reversal 1, 2, 4

Bilateral arm blood pressure measurement is mandatory for all patients with suspected peripheral arterial disease, as recommended by ESC Guidelines (Class I, Level B), with an inter-arm systolic blood pressure difference >10-15 mmHg suggesting subclavian stenosis 1, 2
Complete duplex ultrasound assessment should evaluate peak systolic velocities and velocity ratios at stenotic sites, vertebral artery flow direction, and hyperemia testing if subclavian steal syndrome is suspected 1, 2, 4

Revascularization should be considered (Class IIa, Level B) in symptomatic patients with TIA/stroke related to subclavian disease, coronary subclavian steal syndrome, ipsilateral hemodialysis access dysfunction, severe upper extremity ischemia, or planned coronary artery bypass grafting using the ipsilateral internal mammary artery 1, 2, 4
Endovascular revascularization may be considered over surgery (Class IIb, Level B) due to lower complication rates, despite similar long-term outcomes 1, 2

All patients with upper extremity arterial disease require aggressive cardiovascular risk modification, as subclavian stenosis prevalence is 11.4% in patients with peripheral arterial disease and indicates systemic atherosclerosis 1, 2
Dual antiplatelet therapy should be initiated if revascularization is planned, and statin therapy, blood pressure control, and smoking cessation are essential 1, 2