This document provides an overview of vascular laboratory assessments for peripheral arterial disease (PAD). It discusses the importance of noninvasive tests like ankle-brachial pressure index (ABPI) in evaluating PAD and outlines the history, indications, modalities, and clinical applications of various physiologic tests. These include segmental limb pressure monitoring, exercise testing, reactive hyperemia testing, toe-brachial indexing, and plethysmography for evaluating the severity and location of PAD.

1. Vascular Laboratory: Arterial Physiologic
Assessment & Arterial Duplex Scanning
Dr Rakesh Kumar Jha
Final Year Resident
Army Hospital Research & Referral Centre
New Delhi

2. Scope
 Introduction
 History/ Background
 Modalities
 Working Principal
 Guidelines
 Clinical Application

3. Introduction
 Peripheral arterial disease (PAD) is associated with an amplified risk of
cerebrovascular and cardiovascular morbidity and mortality
 Noninvasive tests are preformed To confirm and define the extent of vascular
disease in patients with
 Suspected lower extremity PAD based upon the history (e.g., symptoms of
intermittent claudication) and clinical examination
 Patients with risks factors for vascular disease (e.g., older age, smoking, diabetes
mellitus)

4. Introduction – Contd…..
 Physiological tests allow the clinician to determine the presence of disease, localize
lesions, and establish the severity of disease to determine the progression or its
response to therapeutic interventions.
 Physiological testing adds objectivity to subjective clinical evaluation
 Three general types of information.
 Anatomic
 Hemodynamic
 Functional

5. Introduction – Contd…..
 Anatomical
 Arterial Segment involved
 Type of lesion – Stenosis/ Occlusion
 Morphology of Plaque
 Haemodynamic
 Gradient across the lesion
 Severity of obstruction
 Functional
 Severity of impairment of limb function due to occlusive lesion
 Co relation between types of lesion and signs and symptoms

6. Indication

7. Importance
 Helpful when diagnosis is uncertain – e.g. Pseudo-claudication
 Determines extent of limitation caused by PAD in conditions like
- Orthopedic
- Neurological
 Detection of PAD in otherwise asymptomatic patients
 Identify patients with intermittent arterial obstruction
- Entrapment Syndromes (PAES)
 In advance disease – ability of ischemic ulcer to heal
 Guidance for optimal level of Amputation

8. Milestones – Physiological Arterial monitoring
 1733 - Steven Hales connected a glass tube to
the “crural artery” of a mare and determined the
systolic blood pressure
 Poiseuille invented the mercury manometer in
1828
 In 1847, Ludwig developed the kymograph,
which was a major breakthrough for obtaining
continuous BP recording and other
hemodynamic information.

9. Milestones – Physiological Arterial monitoring
 1940 - First non‐invasive vascular laboratory was established at Massachusetts
General Hospital
 1950 - Satomura’s developed basic ultrasonic Doppler
 1960 - Strandness and coworkers developed continuous wave Doppler
instruments to detect blood flow and velocity waveforms analysis.
 1970 - Yao showed correlation between reductions in limb blood pressure and
severity of PAD

10. Modalities
 Hand held Doppler
 ABPI/ TBI
 Segmental Limb Pressure (SLP)
 Segmental Limb Volume Plethysmography
 Transcutaneous Oximeter
 Laser Doppler
 Duplex USG Scanning
 Direct Pressure measurement

11. Doppler – Basic Principal
T - Wavelength of DUS R- Wavelength of RBC
Doppler Angle
Principal – Tip of the probe has a transmitting piezoelectric crystal that converts electrical
energy into ultrasound waves, as well as a receiving piezoelectric crystal that detects reflected
ultrasound waves. The probe converts frequency shift into an audible signal

12. Principal
 Transmitting frequency - 5 and 10 MHz
 Suitable for superficial arteries
 A fluid interface is required between the probe and the skin to prevent loss of
energy due to impedance mismatch
 Moving red blood cells act as reflectors that backscatter ultrasound waves

13. Aural Interpretation
 The velocity of blood flow is proportional to the frequency shift which is heard as a
change in pitch of the audio signal
 Loudness is proportional to the volume of red blood cells moving through the Doppler
signal path
 Turbulence due to obstruction/ stenosis causes non-uniform velocities and imparts a
harsh quality audible Doppler signal resulting in a noisy, high-pitched signal at the site
of stenosis.

14. Aural Interpretation
 Arterial obstruction causes dampening of the
waveform distal to obstruction, which
becomes monophasic
 Extremely low flow may not be detectable by
hand-held Doppler due to cutoff of very low
frequencies by the filter that is used to
eliminate wall motion artifacts

15. Hand held Doppler – Clinical Application
 ABPI
 DBPI
 Segmental Pressure measurement
 PPCI
 Penile Brachial Index
 Stress tests

16. Ankle Brachial Pressure Index - Basic Technique
 The ABI is a relatively simple, inexpensive, and
reproducible method to confirm PAD
 The cuff is placed as low as possible on the leg above
the ankle, inflated above systolic pressure, and then
slowly deflated while the Doppler probe is held over the
PTA/DPA
 The ankle pressure is recorded as the highest
pressure at which the Doppler signal returns

17. ABPI – Calculation & Interpretation

18. Arterial Pressure – Physiological Variation
• The pressure wave changes as it moves
distally. Peak systolic pressure is
accentuated, and mean arterial pressure
decreases
• Ankle systolic pressure is approximately
10% higher than brachial pressure (ABI of
1.1)
• Lower extremity vasculature remodels in
reaction to increased intraluminal pressure
from gravity and upright posture to have
increased wall thickening and unchanged
inner radius, leading to increased arterial
stiffness

19. ABPI – fallacies
 Improper patient positioning
 Standing/sitting/ semi recumbent position
 < 10 min of bed rest
 Wheelchair bound patients.
 Faulty Cuff application – AHA Recommendation - bladder cuff length - 80% and width -
40% of the circumference of the extremity (length-to-width ratio - 2 : 1)
 Stiffened Artery – DM/CKD/ Calcified vessels
 Unilateral/ Bilateral upper extremity occlusive disease

20. Role of Ankle Brachial Pressure Index
 Role in PAD
 Screening
 Diagnosis
 Prognosis
 Follow up
 Normal ABI before and after
exercise in a nondiabetic has
a very high negative
predictive value for PAD

21. Comparative studies between ABI and Contrast Angiography
 The sensitivity and specificity associated with an ABI threshold of 0.90 or less have ranged
from a sensitivity of 79% to 95% and specificity of 96% to 100% compared with contrast
angiography.
 Fowkes et al - demonstrated that with an ABI, diagnostic threshold of 0.90, the sensitivity of
the ABI was 95% and specificity was 100% compared with angiography
 Feigelson et al -demonstrated using only posterior tibial measurements in assessing the ABI,
with an ABI diagnostic threshold of 0.8, the sensitivity of the ABI was 89% and specificity was
99% with a overall accuracy of 98% compared with angiography
 Lijmer et al - evaluated the ABI by using a receiver operating characteristic (ROC) to
determine its diagnostic accuracy depending on the localization of the disease. This study
demonstrated patients with significant PAD (lesions ≥50%), with an ABI diagnostic threshold
of 0.91, the sensitivity of the ABI was 79%, and specificity was 96%.

22. ABI and Cardiac and Neurological conditions
 Studies have also shown that an abnormal ABI is predictive of both cardiovascular and
cerebrovascular events
 Newman et al. - has shown an inverse relation between cardiovascular disease and ABI in a
cohort of 5084 participants. Patients with an ABI <0.8 were likely to have > twice the risk of
MI,CHF, stroke, angina, or TIA as compared to those with an ABI of 1.0 to 1.5.
 Multiple studies have shown the importance of the ABI as a predictor of cardiovascular or all-
cause mortality in asymptomatic patients.
 Criqui et al. has evaluated a 10 year follow up of 67 patients with a diagnosis of PAD and a
ABI of < 0.80, showing a dramatic increase in rate of mortality in both men (61.8%) and
women (33.3%) when compared with men (16.9) and women (11.6%) without disease.
 Mortality and morbidity in patients with lower extremity PAD has been quantitated by
McKenna et al., who demonstrated a 5-year mortality of 50% and 30% in patients with ABI of
0.40 and 0.70, respectively

23. ABI - Limitations
 The ABI may not be accurate in individuals with non-compressible arteries
 Patients with iliofemoral stenosis/ Occlusion may also occasionally present with a normal ABI
at rest because of the presence of collateral arterial networks
 In these cases, an alternative diagnostic test (e.g., toe-brachial pressure, Doppler waveform
analysis, PVR, exercise ABI test, or duplex ultrasound) should be performed

25. Stress Test
 It is a useful, practical method for quantitating the functional effect of arterial
insufficiency.
 Basic Principal - Pressure reduction across a stenosis depends on the rate of flow
through it. This is the basis of exercise testing to detect stenoses that may not cause
abnormalities at rest
 Types
 Exercise testing
 Reactive Hyperaemia

26. Stress Test - Indication

27. Exercise Test - Method
 Patient rests supine for 20 minutes after which resting ABI is
measured
 Patient is asked to walk at 2 miles/h on a treadmill at a 12-
degree inclination for 5 min or until forced to stop because
of symptoms
 The patient’s leg symptoms, location of symptoms, and
their intensity should be recorded at onset of symptoms
and at the time of maximal discomfort
 ABI measured after 1 min and then every 2 minute for 10
minutes or until the pressure returns to resting levels

28. Exercise Test - Interpretation

29. Exercise Test - Interpretation
In normal limbs, Rt LL and both the arm
pressure rise with exercise. In limb with
PAD (left) ankle pressure falls following
exercise. The exercise capacity,
post‐exercise pressure fall, and pressure
recovery time reflect the severity of the
PAD
Exercise study in patient with left lower limb PAD
disease (PAD

30. Exercise Test - Interpretation
 The treadmill test (duration of walk) tends to be more
positive with proximal disease than with distal disease
 Exercise testing is not effective for detection of disease
below the level of the popliteal artery because the sural
branches to the gastrocnemius muscle off at or
proximal to this level
 In situations where ambulation is not feasible, protocols
involving dobutamine infusion or toe‐tip exercise may
be substitutes for walking protocols

31. Exercise Test - Limitations
Patients with
 rest pain
 Non-compressible vessels on a resting study
 Acute DVT
 Shortness of breath at rest or with minimal exertion
 Uncontrolled angina
 A physical disability

32. Alternative Stress tests
 Active pedal plantar flexion
 The patients raise their heels as high as possible and then immediately lower
them, repeating the cycle for up to 50 consecutive repetitions
 ABIs are measured immediately after completing the exercise with the patient
in a supine position
 Comparative study of active pedal plantar flexion technique Vs treadmill exercise
was conducted by McPhail et al which showed an excellent correlation (r = 0.95,
95% confidence interval 0.93 to 0.97) between mean post exercise ABI for treadmill
exercise and active pedal plantar flexion

33. Reactive Hyperaemia
 Indication - When exercise test is not possible because of comorbid conditions or during
situations when walking is not possible
 Method
 Standard blood pressure cuffs are placed around the thigh and ankle
 Thigh cuff inflated above systolic blood pressure for 3 to 5 minutes
 Once the thigh cuff is deflated, ankle cuff is inflated briefly above the systolic blood pressure, so that
using the Doppler instrument, Systolic arterial pressure can be immediately taken at both ankles
 Interpretation –
 > 50% decrease in ankle blood pressure indicates PAD.
 The magnitude of the drop in pressure and length of recovery to baseline correlates with the severity of
disease

34. Reactive Hyperaemia
 Advantages over treadmill testing
 Faster and less cumbersome
 Doesn’t depends on patient motivation
 Easily standardized
 Not affected by cardiovascular or orthopedic conditions
 Dis- advantages
 Low sensitivity and specificity when compared to exercise testing
 More operator dependent because of the need for rapid pressure measurements, and
 It does not directly test the patient's ability to walk

35. Segmental Leg Pressure (SLP) Monitoring
 ABI cannot determine the location of proximal
arterial lesions or the relative significance of lesions
at multiple levels.
 Measurement
 Patient rests in supine position for 20 minutes
 Pneumatic cuffs - upper and lower portions of thigh,
calf, above ankle, and often over mid foot and great
toe
 The Resting ABI is calculated, and then the pressure
is sequentially inflated in each cuff to 20 to 30 mmHg
above systolic pressure.
 Segmental systolic pressure between 2 adjacent
cuffs are recorded using hand held doppler.

36. SLP - Interpretation
 A Vertical blood pressure gradient >20
mm of Hg signifies significant occlusive
disease between the cuffs.
 The horizontal gradients between
corresponding segments of the two legs
may also indicate the presence of
occlusive lesions

37. SLP- Limitations
 Disease distal to the ankle is not detected
 It doesn’t detect disease in nonaxial vessels, such as the profunda femoris
 Multilevel disease can be difficult to identify if there is significant proximal
stenosis

38. PPCI – Profunda- Popliteal Collateral Index
 An estimate of the extent of collateralization around the knee in patients with
superficial femoral artery occlusion
 Calculation - Above-knee pressure - Below knee pressure
above-knee pressure
 Interpretation
< 0.25 - Good result from Profundaplasty without infra-inguinal bypass
> 0.50 - No improvement with Profundaplasty alone
 A low index indicates good collateral development (little pressure drop across
the knee)

39. Toe Brachial Index
 As digital arteries are less commonly calcified
than tibial arteries, toe pressures are useful in
patients prone to arterial calcification, such as
diabetics and patients with chronic kidney
disease
 A toe-brachial index < 0.7 is considered
abnormal
 However, even digital arteries can be calcified
and non-compressible, at which point
waveform analysis or transcutaneous oxygen
tension (tcPO2) may be helpful

40. Toe Pressure Monitoring – Clinical Implication
 Toe Pressures of 30 mm Hg or
lower are associated with ischemic
symptoms
 Foot lesions usually heal when the
toe pressure is greater than 50 mm
Hg (or slightly higher in diabetics)
(From Bakker K, Apelqvist J, Schaper NC; International Working Group on the
Diabetic Foot Editorial Board. Practical guidelines on the management and
prevention of the diabetic foot 2011. Diabetes Metab Res Rev. 2012;28:225–231.)

41. Vasculogenic Impotence - PBPI
 Of the three paired penile arteries, arise from the internal
pudendal artery, cavernosal artery is the most important for
erectile function
 Proximal occlusive disease can be responsible for
vasculogenic impotence
 Pneumatic cuff applied at the base of the penis. Return of
blood flow when the cuff is deflated can be detected by a PPG
or Doppler flow probe.
 Penile-brachial indices greater than 0.75 to 0.80 are
considered compatible with normal erectile function
 An index of < 0.60 is diagnostic of vasculogenic impotence

42. Plethysmography
 Principal - Measurement of
variation in volume of an
extremity in a segmental
manner from the thigh to the
ankle during cardiac cycle.

43. Plethysmography - Types
1. Mercury strain gauge - Change in volume causes
a change in circumference and therefore in the
length and electrical resistance of the strain gauge
2. Impedance plethysmography - It monitors
electrical impedance, which is inversely
proportional to volume
3. Air plethysmography - Monitors pressure in
multiple cuffs placed around the extremity
inflated to 65 mm Hg. Limb expansion
displaces air from the cuff, creating changes in
volume and pressure
 The resistance is measured and plotted on a strip
chart, which results in a waveform or PVR

44. Pulse Volume Recording
 Like SLP, PVR can be used to infer the presence and
location of arterial occlusive disease
 The normal pulse contour has a rapid upslope, a sharp
systolic peak, a dicrotic notch, and a downslope that
bows toward the baseline
 Downstream from stenotic segments, the waveform
becomes dampened—the upstroke becomes less
steep, the dicrotic notch is lost, and the overall
amplitude is decreased

45. PVR-Characteristics
 Waveform degradation follows a
typical pattern
 Early loss of the dicrotic notch
 Increased upstroke time
 Widening of the peak
 Loss of amplitude

47. PVR - Advantages
 Useful in patients with noncompressible vessels in whom ABIs and segmental pressures are
spuriously elevated
 Useful diagnostic test for patients with suspected PAD and assesses limb perfusion after
revascularization
 It also can predict limb ischemia and foot at risk of amputation
 Provide information regarding small-vessel disease when applied to the feet
 Reported diagnostic accuracy of 97%

48. PVR Vs Doppler
 Like Doppler, plethysmography can be used to assess arterial patency in two major
ways
 Pulse detection;
 Waveform changes
 PVR is easier to apply, simple to use, and more reproducible than the Doppler in
routine clinical practice
 Presence or absence of edema have surprisingly little effect on amplitude
 In contrast, changes in physiological variables such as vasoconstriction/ vasodilation
dramatically influence pulse amplitude.

49. Digital Plethysmography
 Useful when calcified tibial vessels causes false elevation in ankle pressure or when occlusive
disease is distal to the ankle level
 Changes in the plethysmographic waveform in the digit reflect proximal disease
 Digital PVR is also useful for determining the extent of sympathetic activity in patients with
cold sensitivity or significant steal syndrome caused by dialysis access grafts.

50. Digital Plethysmography
 Response to Reactive hyperaemia
 Technique - A cuff is placed at the ankle, inflated above systolic pressure for
3 to 5 minute and rapidly deflated while the digital PVR is monitored
 In normal limbs pulse returns rapidly, attains half its baseline amplitude
within a few seconds, and then rises quickly to twice baseline
 With PAD, reappearance of the waveform and return to half the resting
value are markedly delayed
 The response to reactive hyperemia requires resting sympathetic tone.
Therefore this test is also useful for predicting the response to
sympathectomy
 If the increase in PVR amplitude is less than twice the resting level in
case of reactive hyperemia, sympathectomy unlikely to improve skin
blood flow

51. Transcutaneous Oxygen Tension (TCPO2)
 Transcutaneous oximetry (tcpO2) measures local oxygen released from the capillaries,
reflecting metabolic state of the lower limb
 Principal - Electrodes containing a circular silver–silver chloride anode surrounding
a central platinum cathode are placed at
- Dorsum of foot
- Antero-medial aspect of calf 10 cm below patella and
- 10 cm above the patella.
The sub-clavicular region of the chest has been used as a reference site
 The electrode has a heating element that raises the skin temperature to 45° C which
causes vasodilatation and diffusion of oxygen.

52. TCPO2 – Interpretation
 Normal - >50 mm Hg
 20 - 40 mm Hg - Wound healing is not reliable.
 < 20 mm of Hg – No healing
 Positional Variation – TcPo2 increases with limb
dependency

53. TCPO2 - Uses
 Classification of peripheral arterial disease
 Healing prediction and outcome of chronic wounds
 Serial assessment of peri-wound oxygenation
 Prediction and optimal level of amputation
 The selection of patients for hyperbaric oxygen therapy (HBOT).

55. TCPO2- Important consideration
 Exercise decreases skin tcPO2 because of shunting of blood away from the skin by dilatation
of intramuscular vessels
 The tcPO2 response to hyperemia is similar to that of ABI ; it decreases after inflow
obstruction and slower to recover in patients with severe PAD
 TcPO2 not affected by arterial calcification - useful in diabetic patients
 tcPO2 measurement is relatively insensitive to mild or moderate degrees of PAD because the
oxygen supplied to the skin is far greater than the demand and oxyhemoglobin dissociation
curve does not change significantly until oxygen saturation drops to < 80%,

56. Laser Doppler and Skin Perfusion Pressure (SPP)
 The laser Doppler uses monochromatic light to detect
motion of red blood cells to a depth of approximately
1.5 mm in the skin
 Principal – Transmitted light is backscattered by RBCs,
The frequency of received light with change in
frequency and wavelength interpreted
 Normal pressures of 50 to 70 mm Hg
 Pressures less than 30 mm Hg are predictive of critical
limb ischemia
 A combination of SPP > 40 mm Hg and toe blood
pressure > 30 mm Hg has been associated with
successful wound healing

58. Non- invasive Vascular studies in Clinical scoring

59. Near-infrared spectroscopy (NIRS)
 NIRS is a technique to determine muscle tissue
oxygenation
 The devices consist of a laser light source and photo
detectors. The light is partly absorbed and scattered by
the examined tissue, and the light that is reflected back
is recorded by the detector
 NIRS uses the absorption spectra of the tissue
chromophores oxyhemoglobin and deoxyhemoglobin to
calculate the tissue saturation
 These values can be expressed as tissue oxygen
saturation (StO2), regional haemoglobin oxygen
saturation (rSO2) or skeletal muscle oxygen saturation
(SmO2).
 StO2 has significant lower values in patients with PAD
compared with healthy controls

60. Capillaroscopy
 Blood flow in the microcirculation is composed of the
skin nutritional capillaries and thermoregulatory
arteriovenous (AV) shunts
 Basic light microscopy can be used to study skin
capillaries, usually in the nail skin folds.
 Dynamic capillaroscopy with sophisticated computer
software programs has been used to measure
microvascular dynamics, flow distribution, and
permeability
 The addition of fluorescent dyes to dynamic
capillaroscopy distinguishes microvascular from the
interstitial compartments and assess transcapillary
diffusion.

61. Direct Pressure Measurement
 Gold standard to which indirect methods are compared
 Invasive
 When other physiological tests are inconclusive
 Most definitive test is direct pressure measurement
 Done intraoperatively or at the time of percutaneous angiography
 Vasodilators can be used when results are equivocal
 Measurement of pressure along the course of a bypass can be a useful, rapid means of locating
technical problems

62. Direct Pressure Measurement
 Technique -The artery (generally CFA) is
punctured with a 18 -gauge needle and
connected to a standard strain gauge with stiff
tubing.
 Compared with a reference pressure, such as the
radial artery
 The same pressure transducer is used to make it
easy to switch between the two pressure lines and
to eliminate errors that may be caused by having
the two transducers at different heights

63. Arterial Duplex scanning

64. Arterial Duplex scanning
 In 1974 Strandness introduced ultrasonic duplex scanning into clinical practice
 It combines 2D gray scale ultrasound imaging with velocity measurements and provides anatomic
as well as hemodynamic information
 Principal - Uses transducers fabricated from piezoelectric crystals to convert electrical energy to
mechanical energy (ultrasound) and thereby allowing the same device to transmit and receive
ultrasound signals.
 By processing retrieved ultrasound beam signals from the transducer array, a scan converter
organizes both horizontal and vertical pixels to yield a two-dimensional view of tissue being
scanned
 Higher frequency (5 to 12 MHz ) and linear probe is used for superficial arteries
 Smaller frequency (2 – 3.5-MHz ) and curvilinear probe is used for visceral /Deeper artery

65. DUS - Imaging Technique
 Technique
 B-flow (Brightness Mode)
 Color Doppler
 Power Doppler

66. B Mode Imaging
 Flowing blood and the surrounding structures are
depicted in shades of gray in 2D
 Provides Anatomical details of vessels
 Doesn’t provide velocity information
 Usually, 100 to 200 separate ultrasound beam lines
are used to construct each image.

67. B Mode Imaging – Clinical Implication
 Identify and localize
 Areas of arterial narrowing,
 Aneurysms (both true and false)
 Extrinsic arterial compression
 Calcifications
 Graft abnormalities
 Plaque morphology
 Complex flow patterns seen at bypass graft anastomoses and arteriovenous
fistulae and within dialysis access conduits
 Assess the carotid intimal medial thickness (CIMT) – a potential risk factor for
the development of CVA/ PAD– has become an area of intense research
interest

68. Color Doppler
 In color doppler, Color is superimposed on a conventional gray-scale image to enhance
the image of the Doppler frequency shift
 Depicts both flow direction (toward and away from the transducer) and mean velocity
(MV)
 By convention, positive Doppler shifts, caused by blood moving toward the transducer, are
encoded as red and negative shifts are encoded as blue
 In healthy individuals, arterial flow is pulsatile and laminar, whereas stenoses, angles, or
branching may cause the laminar flow pattern to be disturbed
 Additionally, turbulence at the stenosis and distal to the area causes an increase in the
rage of flow velocities known as spectral broadening

69. DUS – Flow Pattern
 Normal peripheral arteries at rest have a triphasic
(Upstroke systolic flow component, early diastolic flow
reversal, and late diastolic forward flow) or biphasic flow
pattern
 When the PVR is low, either due to the arterial bed
downstream or after exercise, hyperemia, or vasodilating
drugs, velocity waveform loses the reverse flow
component and becomes monophasic
Biphasic Flow

70. DUS – Pathological Flow Pattern
 The earliest change at the site of stenosis
spectral broadening in early diastole,
when flow is decelerating and least stable
 The higher-frequency components of the
pressure waveform are more sensitive to
the dampening effect of stenoses
 A peak systolic pressure drop across an
arterial segment of 10 mm Hg at rest or
15 mm Hg after hyperemia, exercise,
ischemia, or administration of
vasodilators indicates significant stenosis

71. DUS – Tardus Parvus Pattern
 Tardus parvus refers to a pattern of Doppler
ultrasound spectral waveform resulting from arterial
stenosis.
 The phenomenon is observed distal to the site of
stenosis due to reduced magnitude of blood flow
through the narrowed vessel.
• Tardus: prolonged systolic acceleration (i.e. slow
upstroke)
• Parvus: small systolic amplitude and rounding of
systolic peak

72. Power Doppler
 This imaging mode is a newer technique and termed
as “color angio”
 It is based on amplitude of the backscattered
Doppler signal represented by color
 Doesn’t provide info velocity or direction of flow
 It increases the sensitivity of flow detection three to
five times with respect to color Doppler imaging
 Advantage
 Independence from the angle of insonation,
 Absence of aliasing, and
 the ability to detect very low flows

73. Spectral Doppler Waveform
 It consists of a continuous and pulsed-wave form.
 Continuous wave Doppler uses two piezoelectric crystal transducers where one crystal
continuously emits doppler waves toward the region of interest and the other
continuously receives reflected echoes
 Represented by audible frequencies
 No information about the depth of the tissue
 No image is produced
 Pulsed-wave spectral Doppler shows the “spectrum” of the returned Doppler
frequencies in a characteristic 2D display.

74. DUS - Indices
 PSV
On a Doppler waveform, the peak
systolic velocity corresponds to
each tall “peak” in the spectrum
window
Uses - interpretation of normal
arterial flow, critical limb ischemia
and for grading of arterial stenosis
The ratio of PSV (Vr) across a
stenosis is a useful parameter for
grading the severity of stenosis
 Vr > 2 - > 50% and > 4 correlates
with > 70% stenosis

75. DUS - Indices
 Pulsatility index (PI) = Peak systolic velocity - Minimal diastolic velocity / (mean
velocity)
 Normal - For peripheral arteries > 4.0 (femoral artery, >6; popliteal artery, >8).
 < 4 reflects proximal inflow or occlusive disease
 “Damping factor;” Division of distal artery PI by proximal artery PI . Normal value
is > 0.9, value < 0.9 is diagnostic of occlusive disease.
 The EDV measurement is used in conjunction with PSV for evaluating high-grade
stenosis (>70% diameter reduction)

76. DUS - Indices
 Resistive Index (RI) = PSV – EDV
PSV
 Normal value < 0.7
 > 0.85 – represents increased vascular bed resistance and decreased end-organ
perfusion
 It assess the renal and cerebral circulations for abnormal peripheral resistance
 Systolic acceleration time (AT)
 Time taken to reach the peak velocity from base line
 Normal value is <133 ms.
 Influenced by cardiac conditions (cardiomyopathy, aortic valve disease)
 Downstream occlusive disease has no influence

77. AT, Systolic acceleration time; EDV, end-diastolic velocity; PI, pulsatility index; PSV, peak systolic
velocity; RI, resistive index.

78. Arterial Duplex scanning - Uses
 Screening for arterial disease
 Enhance diagnostic accuracy
 Intraoperative assessment
 Surveillance after arterial intervention
 Evaluation of plaque morphology

81. Carotid diseases

82. Renal artery stenosis

83. Mesenteric vessel
 Peak systolic velocity (PSV)
 SMA - > 275 cm/s, or no flow
 Coeliac trunk - >200 cm/s
 Indicator of > 70% angiographic stenosis

84. Intra op and post op surveillance
 Endo leak
 Endo tension
 Thrombosis of false lumen
 Thrombosis of sac
 Patency of graft/ stents
 Instent restenosis
 Neo intimal hyperplasia
 Stent/ graft thrombosis
 Pseudoaneurysm
 Graft infection
 AV fistulsa

85. Surveillance
 Baseline examination
within 30 days of surgery,
subsequent examinations
at 6-month and then
annually after the first
year for vein grafts.
 Post Intervention - criteria
for repeat angiography
included a PSV above 300
cm/s and a Vr of 2, which
is commonly predicated
on a clinical deterioration,
an ABI decrease by 0.15

86. DUS Vs CTA and MRA
 Collins et al performed a systematic review of the literature comparing the three
different imaging modalities. In detecting a greater than 50% stenosis
 contrast-enhanced MRA demonstrated a median sensitivity and specificity of
95% and 97%, respectively
 CTA showed a sensitivity and specificity of 91% and 91%, respectively
 DUS showed a sensitivity and specificity of 88% and 96%, respectively

87. Advantages
 Easy availability
 Non- invasive
 No contrast use
 No Ionizing radiation
 Cost-effective
 Suitable for serial examination

88. Disadvantages
 Shadowing from overlying vessel calcification
 Inaccuracy due to refraction, and aliasing
 Spectral Doppler aliasing is the most common artifact recognized by a “characteristic”
signal wraparound in the spectral display
 Gender and physiologic condition also affect the outcomes of DUS evaluations
 Carotid PSV measurements in women average 10% higher than in men
 Congestive heart failure, dysrhythmias, and artificial support measures
(ventilators, intra-aortic balloon pumps, or pacemakers) can alter cardiac
output, which in turn can affect PSV.
 Operator variability

89. Trans Cranial Doppler
 Transcranial Doppler mostly uses a 2 -5 MHz pulsed,
ranged-gated Doppler device
 Four main ultrasound approaches
 Transtemporal,
 Transorbital,
 Transoccipital
 Submandibular
 The transtemporal approach is used to evaluate the
middle cerebral artery, posterior cerebral artery,
anterior cerebral artery, and terminal internal carotid
artery
 Uses
 Detection of cerebral arterial stenosis
 Monitoring during CAS/CEA/ Thrombolysis for HITS (High
Intensity Transient signal)
 Cerebral perfusion

90. Ultrasonographic Virtual Histology
 Different tissues reflect ultrasound differentially,
resulting in B- mode images with variable
brightness or pixel intensities
 Echogenicity of key histologic components of
atherosclerotic plaques (calcium, fibromuscular
tissue, LRNC, and IPH)
 Pixel distribution analysis (PDA) approach
provides quantification of carotid plaque
histomorphology using simple and readily
available B mode ultrasound technology

91. 3 D DUS
 Principal - Collating a series of 2D cross-sectional
slices in a computer and reconstructing them into a
3D volume
 Uses
 Reproducible quantitative monitoring of plaque
progression, regression and response to therapy
 Aneurysms and aortic dissections
 Advantage - It reduces the operator variability
inherent in traditional 2D imaging
 Disadvantages
 Slow frame rate,
 Lengthy analysis time and
 Limited spatial resolutions

92. Contrast-enhanced ultrasound (CEUS)
 Principal –Administration of IV contrast agents
containing microbubbles of perfluorocarbon or
nitrogen gas.
 Microbubble contrast agents, consists of gas
core. And external shell typically composed
of albumin, galactose, lipids, or polymers
 Microbubbles have a high degree
of echogenicity and act as nearly perfect
intravascular reflectors of acoustic ultrasound
energy without local disruption

93. CEUS - Diagnostic Role
 Extracranial carotid occlusive disease
 Plaque morphology and vulnerability
 Detects neovascularization which plays a role in carotid plaque progression
 Abdominal Aortic Aneurysms
 Visualization of the aneurysmal wall and real-time leakage of extravascular
fluid as well as identification of retroperitoneal hematomas
 intraoperative three-dimensional (3D) CEUS imaging can accurately identify
endoleaks
 Peripheral Arterial Disease
Real-time skeletal muscle perfusion of the lower extremity

94. CEUS - Therapeutic Role
 Targeted drug delivery into arterial walls and thrombi
 Tachibana et al are credited with pioneering the use of microbubbles in
sonothrombolysis. In an in vitro study, they were able to demonstrate that
insonation of Albunex (Molecular Biosystems Inc, San Diego, Calif)
with urokinase led to increased thrombolytic efficacy
K.B. Bader, G. Bouchoux, C.K. Holland. Sonothrombolysis Adv Exp Med Biol, 880 (2016),
pp. 339-362

95. IVUS
 Intravascular ultrasound (IVUS) has emerged as an
important adjunctive modality to angiography.
 IVUS-guided treatment has superior yield when compared to
angiography-only guided therapy
 Real time 360 Degree vessel anatomy and morphology
 Uses
- Precise imaging of the vessel size and plaque
morphology
- Detection of Intimal flap and dissections
- Guides interventional procedures including stent sizing
- Assess residual narrowing, stent apposition and expansion
- Detects Intraluminal webs, mass lesion, residual thrombus
and extraluminal compression

96. Take Home Message
 PAD affects large number of people worldwide and is associated with serious cardiac, Renal
and Neurological morbidity and mortality.
 Early identification of PAD not only allows treatment but also helps in risk factors
modification, to reduce the risks associated with it.
 Non-invasive physiological modalities are important tools in screening, diagnosis,
management and follow up of PAD patients.
 None of these modalities are ideal in isolation. However When interpreted in conjunction
provides a better results.

97. Thank You