By Dr Bhushan Shinde

1. Graft thrombosis
Dr Bhushan Shinde
DNB Vascular surgery resident
Ruby hall clinic, Pune

2. Index ● Introduction
● Prevention of graft thrombosis
○ Intraoperative Graft assessment
■ Inspection, palpation
■ Arteriography
■ Ultrasonography
■ Angioscopy
■ Intravascular Ultrasonography
● Pathogenesis
● Therapeutic approach
○ Early graft failure
○ Late graft failure

3. INTRODUCTION
Discussion focused primarily on infrainguinal graft
thrombosis which forms largest cohort of failed
revascularization
● Graft thrombosis
○ Early= < 30 days
○ Delayed= > 30 days
● At 1 year after infrageniculate bypass
○ graft failure leads to
■ > 50% major amputations.
■ 25% rest pain
■ 15% mortality
● Technical errors accounts for 4% to 25% of early
failure.

5. PREVENTION
INTRAOPERATIVE GRAFT ASSESSMENT
● Inspection, Palpation.
○ Inspection of the graft for kinks, twists.
○ Examination of the distal target vessel and of the
revascularized tissue- pulses, capillary refill, colour
of foot
● Arteriography
○ Gold standard
○ Ability to assess anatomic arterial outflow— “runoff.”
○ Invasive procedure
○ Potential complications because of arterial puncture
■ Intimal injury, dissection
■ Air embolism
■ Use of radiographic contrast agents (renal
failure, anaphylaxis)
■ Radiation exposure

6. ○ Actual observed complication rate has been
negligible in large series.
○ Involves insertion of an 18 to 20-gauge plastic
angiocatheter or 4- to 5-Fr sheath into the
arterial graft to allow subsequent injection of 10
to 30 mL of radiographic contrast agent.
○ Proximal anastomosis is frequently not
evaluated.
○ Air bubbles or overlying structures- false-
positive interpretations.
○ Single plane of view to analyze a multidimensional
target
■ false-negative results
■ underestimation of the stenosis from a small
defect(intimal flap or platelet aggregate).
INTRA-OP ANGIOGRAPHY

7. ULTRASONOGRAPHY
○ Continuous wave doppler
■ Simple and inexpensive
■ 8- to 10- MHz pencil probe
■ Small size allows insonation of
arteries in areas less accessible
to larger probes.
■ Can be passed along the graft
and anastomosis can identify a
potential defect.
■ Patent residual vein branches of
in-situ saphenous vein bypasses
can be readily identified by locally
increased frequency.
■ Operator dependent

8. ● B-MODE ULTRASONOGRAPHY
○ Anatomic images
○ Used in conjunction with duplex ultrasonography
○ Ability to detect small defects
○ Ultrasonography has significantly greater sensitivity in detecting defects, 92%
overall,
■ serial biplanar arteriography at 70%
■ portable arteriography at 50%.
○ Kresowik et al. study
■ 106 patients
■ Intraoperative B-mode ultrasonography detected defects in 20% of patients
■ Half of these defects were deemed important enough to warrant correction.
■ In follow-up, there were no early graft occlusions, no residual defects were
discovered with duplex scanning follow-up in the postoperative period.
○ This modality does not evaluate blood flow
○ It cannot differentiate fresh thrombus from flowing blood.

9. ● DUPLEX ULTRASONOGRAPHY
○ Addition of flow-measuring capability to B-mode ultrasonography.
○ Color imaging facilitates identification of areas of higher velocity,
○ Easier mechanism for identifying defects in proximal arterial anastomoses
○ Can detect low graft velocities that are undetectable by arteriography
○ Unable to assess newly placed PTFE and Dacron grafts, because the graft walls
contain air, which prevents penetration of the ultrasound waves.
○ Low end-diastolic velocity (EDV) was both associated with and predictive of early
graft failure
○ Scali et al. validated the utility of intraoperative completion duplex scanning
following distal bypass, documenting that EDV measurements less than 5 cm/s
predicted early graft failure

10. ● ANGIOSCOPY
○ Requires irrigation with saline accompanied by occlusion of inflow, and sometimes
outflow
○ Many scopes have a separate lumen incorporated for irrigation or suctioning.
○ Widely used for inspection of
■ in-situ saphenous vein grafts to ensure complete valve lysis,
■ to exclude unligated venous branches
■ assess the quality of the venous conduit
■ particularly important in detecting abnormalities within an arm vein conduit
■ evaluations of venovenostomy anastomoses
■ mild intimal injury may occur with angioscopy
● repeated passages of larger diameter scopes.
● a small-diameter (1.4 mm) angioscope in human vein grafts appear to have no
significant late clinical consequences

11. ● In a 2002 study from Sweden,documented
○ successful application of intraoperative angioscopy in a
group of patients who underwent below-knee in-situ
saphenous vein graft bypass;
○ concluded that angioscopy has an impact on primary
graft patency rates and therefore reduces the need for
subsequent reintervention.

12. ● Intravascular Ultrasonography
○ Flexible catheter system
○ Generates two-dimensional cross-sectional images
○ Circumferential rotation of a miniaturized (10 to 30 MHz) ultrasound crystal at the
catheter tip
○ Proved to be accurate in measuring luminal diameter and identifying stenoses
caused by atherosclerosis or intimal hyperplasia.
● Miscellaneous Modalities
■ distal extremity pressure with a sterile blood pressure cuff during surgery.
■ pulse volume recording (plethysmography)
■ photoplethysmography,
■ transcutaneous oxygen tension measurement

13. PATHOGENESIS
● Several studies have identified a variety of
factors potentially contributing to graft failure,
○ Patient demographics
○ Risk factors
○ Comorbid diseases
○ Conduit characteristics
○ Anesthesia type
○ Adjuvant medical therapy
○ Technical precision
● National Surgical Quality Improvement
Program (NSQIP) database from 1995 to
2003 to elucidate risk factors predictive of
graft failure in patients who underwent
infrainguinal arterial bypass revealed that
○ Younger age (<60 years),
○ African American race,
○ Crural target vessel

14. PATHOGENESIS
● Giswold et al. documented reversed vein graft
occlusion
○ Dialysis dependency,
○ Known hypercoagulable state,
○ Ongoing smoking,
○ Failure to undergo routine graft duplex
surveillance
● Oresanya et al. added
○ Small vein graft diameter (<3 mm)
○ Nonadherence to ultrasound
surveillance are independently associated
with graft failure.
● Nolan et al. studied bypass grafts performed
in limbs where a previous endovascular
intervention was performed
○ have higher failure rate (28% occlusion
rate versus 18% occlusion rate without
any prior intervention)

15. PATHOGENESIS
● HYPERCOAGULABILITY
○ The role of hypercoagulability as a
cause of graft failure has become
increasingly recognized in
contemporary practice.
○ Impact of hypercoagulability in light of
the inherent multiple previous
exposures to heparin.

17. THERAPEUTIC
APPROACH
GRAFT THROMBOSIS DIAGNOSIS
● Absence of previously palpable pulse combined with
dramatic progression or return of ischaemic
symptoms
● In less obvious circumstances
○ Noninvasive testing to measure the ankle-brachial
index
○ Duplex ultrasonography
○ to determine location of the occlusion or restenosis
may obviate the need for administration of contrast
material with axial imaging
Assessment of Neurologic Status
● A primary determinant of the necessity for and
urgency of aggressive intervention

18. Anticoagulation
Immediate anticoagulation becomes imperative to minimize or halt thrombus
propagation
Etiologic Assessment
● Any graft failure should be investigated
● Failure to recognize this insidious condition can lead to poor clinical outcomes
and recurrent graft thrombosis
○ Hypercoagulability
○ Thrombocytosis-NSQIP implicated as being independently associated with early graft failure
○ Acute or chronic cardiac decompensation
○ Technical errors account for 20% or less of thromboses in arterial reconstructions in the early
postoperative period.

19. Vascular Study Group of New England, a regional quality improvement
initiative revealed predictives of diminished graft patency.
● Below-knee target
● Tarsal distal target
● Secondary reconstruction
● “Redo” revascularization in the early postoperative period.
● Diabetes
● Preoperative tissue loss
● Greater body mass index (>35 kg/m2 )
● Reconstructions requiring early revision (primary-assisted patency)

20. The five elements critical for sustained function of an arterial reconstruction
● Inflow
● Outflow
● Conduit
● Operative technique
● Coagulation profile
Compromised inflow noted by a gradient between the proximal reconstruction and
central systemic arterial pressure demonstrates the existence of a significant
proximal arterial stenosis. If uncorrected, suboptimal clinical outcomes and graft
durability can be expected.

21. Early graft
failure <30
days
● Early (<30 days) thrombosis of vascular reconstructions
has historically been attributed to technical error.
● In a review of the Dartmouth-Hitchcock experience, it
was found that technical errors accounted for roughly
25% of early graft failures.
● Since that time, the number of graft failures referable to
technical error has declined sharply (10%)
● This improvement can be directly attributed to the
routine use of angioscopy, duplex ultrasound scanning,
and DSA to confirm the technical adequacy of the
arterial reconstruction.
● Thorough graft interrogation greatly simplifies further
therapeutic clinical decision-making
● Commonly used options include
○ Surgical thrombectomy
○ Thrombolysis.

22. THROMBOLYSIS IN EARLY
FAILURE
Thrombolysis places the patient at
significant bleeding risk, especially at
recent surgical sites
After thrombolysis is attempted in the
early postoperative period, the
extended patency of thrombosed vein
grafts ranges between 15% and 20%
at 1 year
Results with thrombolysis of prosthetic
grafts are slightly better, although this
difference is probably related to the
better runoff.
Specifically, a shorter interval to graft
failure will have a diminished likelihood
for success with thrombolytic therapy,
particularly in patients with diabetes
Review of the Dartmouth experience
found that no patient with diabetes
and a recently placed graft achieved
reasonable secondary graft patency
with thrombolysis

23. Surgical thrombectomy
The results of surgical
thrombectomy were
significantly improved if
technical problems (e.g., a
twist in the graft or a retained
valve cusp in an in-situ
saphenous vein bypass graft)
were identified at exploration
Review of the Dartmouth
experience was again similar,
with long-term graft patency
rates for grafts in which
thrombosis occurred
because of correctable,
underlying technical
problems approaching that for
grafts without complications.
If attempts to salvage a
thrombosed infrainguinal graft
remain unsuccessful in the
early postoperative period, two
options remain
● expectant therapy with
anticoagulation.
● Second bypass
procedure

24. LATE GRAFT FAILURE >30
DAYS
Technical errors no longer constitute a
significant cause of graft pathology.
Thrombolytic therapy offers greater
therapeutic utility in this time interval.
Greater magnitude of technical difficulty can be
anticipated in the surgical dissection of
previously operated vessels.
Two factors have been noted in the Dartmouth
experience to be critical in predicting success
after lytic therapy: graft age (since time of
placement) of approximately 1 year or older,
and the absence of diabetes.
After restoration of graft patency, it has been
well-documented that further endovascular or
surgical therapy may be required in up to 85%
of cases to achieve sustained patency

25. Available therapeutic options in this setting include
(1) Balloon angioplasty of an intragraft or juxta-anastomotic stenoses,
(2) Open surgical vein patch angioplasty,
(3) Interposition bypass reconstruction.
In a patient with a failed prosthetic bypass graft secondary to progressive
advanced atherosclerotic disease compromising outflow circulation- percutaneous
treatment with angioplasty or other endovascular adjuncts is justified when no
reasonable surgical alternatives are available.

26. CHOICE OF
CONDUIT
● The optimal autogenous vein conduit for replacement of
a short segment of vein graft is ideally derived from
either the remaining ipsilateral saphenous vein or the
lesser saphenous vein.
● Arm veins, when deemed acceptable on preoperative
duplex evaluation and intraoperative angioscopy
examination, remain an appropriate alternative conduit
for graft revision or secondary bypass.
○ need for graft revision remains greater in
reconstructions in which an arm vein was used as the
conduit, documented assisted primary patency rates
approach 72% over 5 years.
● Although alternative vein grafts spliced graft from the
lesser saphenous vein and the remaining ipsilateral
saphenous vein have been documented to have
equivalent patency to that of an arm vein
○ the associated added morbidity of distal incisions.

27. ● Use of the profunda femoris artery and endarterectomy of the superficial
femoral artery to lessen the requisite conduit length for bypass are important
surgical adjuncts that should be incorporated into treatment paradigms.
● Repeat infragenicular bypass with cadaveric vein
○ in the setting of infection/tissue loss where prosthetic conduit might be at risk to become
infected.

28. THANK YOU