From the Guidelines
A monophasic signal on Doppler ultrasound indicates significant arterial stenosis, and further imaging is required to determine the exact location and severity of the stenosis, such as CT angiography or magnetic resonance angiography, as suggested by guidelines for peripheral arterial disease management 1. The presence of a monophasic signal on Doppler ultrasound in the context of significant upstream narrowing suggests a high-grade stenosis that may be causing hemodynamic compromise.
- Key considerations in managing this patient include:
- Referral to a vascular specialist for comprehensive assessment
- Additional imaging to determine the exact location and severity of the stenosis
- Initiation of antiplatelet therapy and risk factor modification
- Consideration of revascularization procedures based on stenosis severity and symptoms Given the potential for significant morbidity and mortality associated with untreated peripheral arterial disease, an aggressive approach to diagnosis and management is warranted, as indicated by guidelines for patients with claudication or rest pain, absent foot pulses, and absent or monophasic Doppler signals 1.
- Initial management steps should include:
- Antiplatelet therapy with aspirin (75-100mg daily)
- Consideration of clopidogrel (75mg daily) for dual antiplatelet therapy
- Statin therapy (atorvastatin 40-80mg or rosuvastatin 20-40mg daily) for risk factor modification
- Blood pressure control (target <140/90 mmHg) and diabetes management (target HbA1c <7%)
- Smoking cessation and regular exercise Regular follow-up with ankle-brachial index measurements every 3-6 months is recommended to monitor disease progression and adjust management as needed, based on the most recent and highest quality evidence available 1.
From the Research
Management Approach for Significant Upstream Narrowing
The presence of a monophasic signal on Doppler ultrasound suggests significant upstream narrowing in the lower limb. To determine the best course of action, it is essential to consider the diagnostic accuracy and cost-effectiveness of various imaging modalities.
- Diagnostic Accuracy: Contrast-enhanced magnetic resonance angiography (CE MRA) has been shown to have the highest diagnostic accuracy for detecting stenosis greater than 50% in the lower limb, with a sensitivity ranging from 92 to 99.5% and specificity from 64 to 99% 2, 3.
- Cost-Effectiveness: Duplex ultrasonography (DUS) has been found to be the most cost-effective preoperative diagnostic strategy for assessing the whole leg, presenting higher effectiveness at a lower cost per quality-adjusted life-year (QALY) 2.
- Patient Preferences: Patients generally prefer CE MRA over contrast angiography, and half of patients express no preference between CE MRA and DUS 2, 3.
Need for Additional Imaging
Given the monophasic signal on Doppler ultrasound, additional imaging may be necessary to confirm the diagnosis and determine the extent of the narrowing.
- CE MRA or CTA: Consider using CE MRA or computed tomography angiography (CTA) to provide more detailed information about the location and severity of the narrowing 2, 3.
- DUS: DUS may be used as an alternative to CE MRA or CTA, especially if the patient has contraindications for these modalities or if the narrowing is suspected to be above the knee 2, 3.
Monophasic Waveforms
Monophasic waveforms in the common femoral vein are reliable indicators of proximal venous obstruction 4, 5. If a monophasic waveform is identified, further investigation is warranted to determine the cause of the obstruction.