Introduction

Noninvasive arterial and venous Doppler exams are a primary diagnostic tool in the diagnosis of arterial and venous disease. Spectral Doppler waveform analysis is a critical component of these examinations. Over the years, there have been conflicting Doppler waveform terminologies applied to the interpretation of these exams between various interpreting physicians. These conflicting interpretations have caused confusion for ordering and interpreting physicians, sonographers, and patients resulting in the increase of missed diagnoses or unnecessary duplication of Doppler testing. In 2020 the Society for Vascular Medicine and the Society for Vascular Ultrasound joined forces to publish a consensus for the interpretation of peripheral arterial and venous Doppler waveforms to help standardize reporting procedures and improve consistency in patient care. This course will discuss the prior nomenclature, problems with the prior nomenclature, the new nomenclature, and the benefits of standardization. This course will clarify descriptors that are crucial to the interpretation of arterial and venous Doppler waveforms.

Prior Waveform Nomenclature

Since the beginning of the use of noninvasive arterial Doppler testing, waveform descriptions of triphasic, biphasic, and monophasic have been used. Some of these descriptors have some overlap in their interpretation which is a contributing factor to the confusion in terminology.

Triphasic waveforms were described as waveforms that have 3 phases and are generally used to describe normal arterial blood flow. These 3 phases are defined by how the waveform is displayed in relation to the zero-flow baseline on the spectral Doppler display. The systolic portion of the waveform is above the zero-flow baseline, the early diastolic portion of the waveform is below the zero-flow baseline, and the late diastolic portion is again above the zero-flow baseline ending that cardiac cycle. These waveforms have also been called multiphasic. Triphasic waveforms are generally high resistance with diastolic flow reversal and continued forward flow through the remainder of diastole. Triphasic waveforms also demonstrate the sharp upstroke and brisk downstroke.

Fig 1. Spectral Doppler image of a triphasic waveform as identified by prior nomenclature

Biphasic waveforms are similar to triphasic waveforms but have lost the late diastolic forward flow portion of the waveform above the zero-flow baseline. They are referred to as having 2 phases. The first phase is again the high resistance systolic portion above the zero-flow baseline, brisk downstroke with the diastolic portion below the zero-flow baseline with the late diastolic portion having been lost. Biphasic waveforms have also been described as having a sharp systolic upstroke, brisk downstroke, diastolic flow reversal, and continuous forward flow throughout diastole above the zero-flow baseline. These waveforms are often used to describe normal arterial flow. However, there are situations where biphasic waveforms are abnormal which will be discussed later in this course.

Fig 2. Spectral Doppler image of a biphasic waveform as identified by prior nomenclature.

Monophasic waveforms are described as only having 1 phase. These waveforms are displayed on one side of the zero-flow baseline and are generally low resistance. In general monophasic waveforms represent abnormal blood flow, most commonly distal to an area of hemodynamically significant stenosis due to the stenotic area slowing down the blood flow and decreasing the resistance in the distal vessel.

Fig 3. Spectral Doppler image of a monophasic waveform as identified by the prior nomenclature.

Importantly, the presence of a triphasic, biphasic, or monophasic waveform may be entirely normal depending on the vessels that are being measured. For example, a vessel feeding a muscle should have a high-resistance waveform, whereas the internal carotid artery should have a low-resistance waveform.

Updated Consensus Approved Arterial Doppler Nomenclature

In order to clarify and standardize the waveform characteristics, the committee recommends the following nomenclature be adopted. Arterial Doppler waveform interpretation and evaluation should evaluate certain key factors of phasicity, direction of flow, and resistance.

Direction of Flow

In regards to the direction of flow, waveform components above the zero-flow baseline should be referred to as antegrade, and waveform components below the zero-flow baseline should be referred to as retrograde. Waveforms with components above and below (antegrade and retrograde) the zero-flow baseline are bidirectional. Waveforms with no flow on either side of the zero-flow baseline are considered absent.

Fig 4. Spectral Doppler image of an antegrade waveform.

Fig 5. Spectral Doppler image of a retrograde waveform.

Waveform Resistance

In regards to the resistance of a waveform, the waveform should be described as having a high, intermediate, or low resistance. High-resistance waveforms have a sharp systolic upstroke, and a brisk downstroke and can be multiphasic, monophasic, and/or bidirectional.

Fig 6. Spectral Doppler image of a High Resistance waveform.

Low resistance waveforms have a prolonged upstroke and a prolonged downstroke, have lost the end-systolic notch and continuous antegrade flow through diastole, and are monophasic.

Fig 7. Spectral Doppler image of a Low resistance waveform.

An intermediate resistance waveform has been most commonly referred to in the past as a biphasic waveform causing some confusion. This waveform is bidirectional and demonstrates a sharp upstroke, brisk downstroke, an end systolic notch present below the zero-flow baseline, and continuous forward flow throughout diastole. Waveforms that are completely on one side of the zero-flow baseline but have the end systolic notch present above the zero-flow baseline are also referred to as intermediate resistance waveforms, versus in the past, these may have been referred to as monophasic waveforms.

Fig 8. Spectral Doppler image of an intermediate resistance waveform.

Waveform Phasicity

In regards to the phasicity of an arterial waveform, the waveform should be described as Multiphasic or monophasic, eliminating the terms triphasic and biphasic. A waveform that crosses the zero-flow baseline should be referred to as multiphasic. A waveform that does not cross the baseline should be referred to as monophasic. Using past nomenclature, a biphasic or triphasic waveform is now just considered multiphasic, eliminating the confusion and overlapping of the terms biphasic and monophasic.

Fig 9. Spectral Doppler image of multiphasic arterial Doppler waveforms previously identified as triphasic and biphasic.

Fig 10. Spectral Doppler images of a monophasic arterial and venous Doppler waveforms.

Consensus Approved Venous Doppler Nomenclature

Venous Doppler waveform interpretation and evaluation should evaluate the certain key factors of direction of flow, flow pattern, and spontaneity in flow.

Direction of Flow

In regards to the direction of flow, waveform components of a venous Doppler waveform are reported the same as those for an arterial Doppler. The waveform descriptors of antegrade, retrograde, and absent should be used for both arterial and venous Doppler waveform interpretation and evaluation.

Fig 11. Spectral Doppler images of antegrade and retrograde waveforms.

Flow Pattern

In regards to the flow pattern of venous Doppler waveform, the waveform should be described as Respirophasic, Decreased, Pulsatile, continuous, and regurgitant.

Respirophasic waveforms should be used to describe a cyclical increase and decrease in flow velocity which correlates with respiratory phases. This was commonly referred to as respiratory phasicity using the previous nomenclature.

Fig 12. Spectral Doppler image of a Respirophasic venous Doppler Waveform.

Decreased waveforms should be used to describe respirophasic flow that demonstrates less variation with the respiratory cycle than normal for the segment or in comparison to the contralateral segment. This was commonly referred to as dampened or blunted using the previous nomenclature.

Fig 13. Spectral Doppler image of a decreased respirophasic venous Doppler waveform.

Pulsatile should be used to describe a waveform that shows cyclical increases and decreases which inversely correlates with the cardiac cycle. This was commonly referred to as cardiophasic using the prior nomenclature.

Fig 14. Spectral Doppler image of a pulsatile venous Doppler waveform.

Continuous waveforms are characterized by the lack of respiratory or cardiac influice on flow velocity variation resulting in steady and consistent Doppler signal with minimal to no variation in flow.

Fig 15. Spectral Doppler image of a continuous venous Doppler waveform.

Regurgitant waveforms are similar to pulsatile flow demonstrating cyclical increased and decreased flow that varies with cardiac cycle. This flow has similar amplitude in forward and reverse directions.

Fig 16. Spectral Doppler image of a regurgitant venous Doppler waveform.

Spontaneity

A venous Doppler waveform spontaneity should be described as either spontaneous or nonspontaneous. A venous Doppler waveform is spontaneous when it is observed that the blood flow is actively moving in a vein without any external maneuvers such as valsalva or augmentation. A nonspontaneous venous Doppler waveform is when the blood flow is not actively observed in a vein and only noted with maneuvers such as augmentation and valsalva.

Fig 17. Spectral Doppler Image of a spontaneous venous Doppler waveform.

Terms That Are No Longer Recommended

No longer recommended-“Triphasic” and “Biphasic”

The recommended term to be used for these descriptors is Multiphasic. This describes a waveform that crosses the zero-flow baseline and contains both forward and reverse velocity components.

Fig 18. Spectral Doppler image of a Multiphasic waveform.

No longer recommended: “Tardus et parvus,” “Attenuated,” or “Blunted”

The recommended term to be used for these descriptors is Dampened. This describes a combined finding of an abnormal upstroke (delayed) and peak (broad), often with decreased velocity.

No longer recommended: “Tardus,” “Delayed,” or “Damped”

The recommended term to be used for these descriptors is Prolonged Upstroke. This describes an abnormally gradual slope to peak systole.

Fig 19. Spectral Doppler image of a Dampened Waveform with a Prolonged Upstroke

No longer recommended: “Non-Laminar,” “Turbulent,” “Disordered,” or “Chaotic”

The recommended term to be used for these descriptors is Spectral Broadening. This describes a widening of the velocity band in the spectral waveform, a “filling in” of the clear “window” under the systolic peak.

Fig 20. Spectral Doppler image of waveform displaying Spectral Broadening.

No longer recommended: “Forward Flow” or “Central”

The recommended term to use for this descriptor is Antegrade. This describes blood that is flowing in the normal direction for the artery or vein being evaluated.

Fig 21. Spectral Doppler image of an Antegrade arterial waveform.

No longer recommended: “Reverse Flow” or “Peripheral”

The recommended term to be used for this descriptor is Retrograde. This describes blood that flows opposite to the normal direction for the artery or vein being evaluated.

Fig 22. Spectral Doppler image of an abnormal Retrograde Venous Doppler waveform.

No longer recommended: “To-Fro”

The recommended term to be used for this descriptor is Bidirectional. This describes blood flow that enters and leaves a contained space via the same orifice.

No longer recommended: “Pre-Steal,” “Competitive Flow,” or “Oscillating”

The recommended term to be used for this descriptor is Flow Reversal. This describes blood flow that changes direction, not as part of a normal diastolic flow reversal, which may be transient (positional) or consistent with each cardiac cycle (systole/diastole).

Fig 23. Spectral Doppler image of a Bidirectional waveform with Flow Reversal.

No longer recommended: “Respiratory Phasicity”

The recommended term to be used for this descriptor is Respirophasic. This describes a cyclical increase and decrease in flow velocity, which correlates with respiratory phases.

Fig 24. Spectral Doppler image of a Respirophasic waveform.

No longer recommended: “Cardiophasic”

The recommended term to be used for this descriptor is Pulsatile. This describes blood flow that shows a cyclical increase and decrease, which inversely correlates with the cardiac cycle.

Fig 25. Spectral Doppler image of a Pulsatile venous Doppler waveform.

Summary

Arterial and Venous Doppler waveform interpretation and evaluation has been the primary diagnostic tool for noninvasive peripheral arterial and venous disease since the 1980s. Since then, the terminology used to evaluate and interpret these exams has been a long-standing point of controversy and confusion. The absence of uniformly accepted terminology has contributed to this. With the consensus statement developed by the Society for Vascular Medicine and the Society for Vascular Ultrasound, standardization of the evaluation and interpretation of these exams can be accomplished as long as physicians and sonographers adapt to this terminology and incorporate it into their practices.

Arterial and Venous Doppler Waveform Nomenclature

Arterial and Venous Doppler Waveform Nomenclature