Intraoperative Duplex Evaluation of Arterial Repairs
Dennis F. Bandyk
Kelley D. Hodgkiss-Harlow
Assurance of technical adequacy is a fundamental principle of vascular surgery whether performed by an open surgical or endovascular technique. Unrecognized repair site defects can result in thrombosis, embolization, and stenosis and contribute to early hemodynamic failure. Verifying that the arterial reconstruction is technically “normal” should be routine and a step central to quality patient care.
How to best accomplish the intraprocedural assessment depends on the type of arterial intervention as well as preferences and experience of the surgeon or interventionist. While arteriography is considered the standard for evaluation after an endovascular intervention, routine use of arteriography in the operating room (OR) after open arterial repair may require additional arterial access, and it is best done in a dedicated hybrid OR suite, which is expensive and not always available. It can be cumbersome for OR staff to wear protective lead garments throughout the operation or to rescrub after donning lead. Multiple angiography runs are needed for complete anatomic imaging to exclude a significant abnormality.
Duplex scanning provides both anatomic and hemodynamic assessment and has been used for intraoperative evaluation after carotid endarterectomy; for renal and visceral artery reconstructions; and to confirm functional (stenosis-free) patency of lower limb bypass grafts or sites of endovascular therapies.1,2,3,4,5,6,7 Ultrasound imaging can be performed transcutaneously or by direct placement of the transducer on exposed vessels in the surgical field. Duplex scanning uses high-resolution B-mode imaging, both color and pulsed Doppler flow analysis to identify residual abnormalities, and the application of anatomic and velocity spectral criteria to confirm an acceptable technical result or to categorize the significance of residual abnormalities.8
Duplex ultrasound is a suitable alternative to arteriography in terms of accuracy, but it also has the advantages of being noninvasive and readily available in most vascular surgery suites. The diagnostic accuracy for excluding technical error is in the range of 90%. Importantly, a normal study is associated with a high negative predictive value for early repair site failure.1,2,3,5,7 The principal limitation of duplex scanning is the need for hands-on skills and experience to perform vessel imaging and to acquire the necessary pulsed Doppler velocity spectral recordings.
The goal of this intraoperative assessment is to optimize the technical precision of the arterial intervention and, in the process, to modify open surgical and endovascular interventions to improve outcome.7 Despite careful operative or endovascular technique, a variety of abnormalities ( stenosis, plaque dissection, platelet-thrombus, occlusion, low-flow state) can persist after an arterial intervention (Table 30.1). If the altered anatomy and associated flow disturbance are severe, the defect can induce blood coagulation to form platelet aggregates that can embolize or induce repair site thrombosis. Even without thrombosis, a residual stenosis alters hemodynamics in a way that predisposes to repair site myointimal hyperplasia and early failure.2,3,5 A secondary intervention in the immediate or early postprocedural period can often salvage this situation, but overall patient morbidity, health care costs, and the likelihood of reintervention are increased.
Intraoperative assessment with duplex scanning also provides a dynamic means to identify and characterize arterial pathology to be repaired. For example, intraoperative duplex scanning can find focal stenoses from extrinsic compression due to popliteal entrapment or median arcuate ligament compression, and then it can be used to verify normal hemodynamics after release of the compressive fibromuscular bands.9,10,11
TECHNIQUES FOR INTRAOPERATIVE ASSESSMENT
Duplex scanning is complementary to other intraoperative assessments such as visual inspection, pulse palpation, continuous-wave (CW) Doppler flow analysis, and angiography. Repair site imaging is typically performed after the intervention is completed but before the incision is closed or catheter access is terminated. At this point in the procedure, inspection and pulse assessment are considered to be normal or acceptable. In this setting, duplex scanning will identify an unsuspected problem in 3% to 15% of cases, with the nature of the problem dependent on the anatomic site of the arterial intervention.1,2,3,4,5 When the initial clinical assessment or a completion angiogram is abnormal or equivocal, duplex testing can be helpful in further defining the residual abnormality based on anatomic and hemodynamic criteria. Application of duplex ultrasound is feasible for all
open surgical arterial repairs and transcutaneous imaging of peripheral angioplasty procedures (Table 30.2); however, carotid, iliac, and mesenteric or renal artery angioplasty procedures are better assessed for technical adequacy with angiography, pressure measurements, or IVUS findings.
open surgical arterial repairs and transcutaneous imaging of peripheral angioplasty procedures (Table 30.2); however, carotid, iliac, and mesenteric or renal artery angioplasty procedures are better assessed for technical adequacy with angiography, pressure measurements, or IVUS findings.
TABLE 30.1 INTRAOPERATIVE DUPLEX ULTRASOUND IDENTIFIED ABNORMALITIES RELATIVE TO ARTERIAL REPAIR, IN DECREASING ORDER OF FREQUENCY | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ||||||||||||||||
TABLE 30.2 DIAGNOSTIC METHODS AND “NORMAL” THRESHOLD CRITERIA FOR INTRAPROCEDURAL ASSESSMENTS OF OPEN SURGICAL AND ENDOVASCULAR PERIPHERAL ARTERIAL REPAIRS | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Transducer Selection
A high-frequency (10 to 15 MHz) hockey stick-shaped, linear array transducer is preferred for detailed intraoperative imaging. Asepsis is maintained by placing the transducer in a sterile plastic sleeve, with gel for acoustic coupling (Fig 30.1). To image deeper vessels (carotid stent, lower limb angioplasty sites, anatomic tunneled bypass grafts), a 5- to 7-MHz linear array transducer is used to scan transcutaneously over the area of interest.
Scanning Technique
The assistance of a vascular technologist to optimize instrument settings facilitates testing, whether performed in the operating room or interventional angiography suite. The surgeon manipulates the transducer over the arterial repair, assessing the B-mode image and color Doppler display, and directs where velocity spectra should be recorded, including any identified abnormalities. Sterile saline is instilled into the operative wound for acoustic coupling, and the transducer is positioned over the artery for scanning in sagittal and transverse planes (Fig. 30.2). Pulsed Doppler velocity spectra should be recorded from a longitudinal image of the artery using an ultrasound beam angle of 60 degrees or less to the vessel wall. The entire arterial repair should be imaged to assess lumen caliber and identify major anatomic defects such as residual plaque, stenosis, or wall dissection. Color Doppler imaging is useful to detect and interrogate sites of flow disturbance produced by flaps, kinks, stenosis, and retained vein conduit valves.
The sequence of scanning should begin at the inflow artery of the repair and proceed distally with imaging of the entire reconstruction and outflow artery. For carotid endarterectomy or visceral artery repairs, only a 10 to 15 cm vessel segment needs to be imaged, while evaluation of an infrainguinal vein bypass requires additional time to image the vein conduit, anastomotic regions, and the inflow/outflow arteries. Testing should be performed when the patient’s hemodynamic status is normal. If hypotension is present, the condition should be corrected before scanning commences. If arterial
spasm, a high-resistance flow state, or low graft flow velocity is detected, direct intra-arterial injection of papaverine (30 to 60 mg) can augment flow by reducing peripheral vascular resistance, thereby enhancing diagnostic accuracy for stenosis detection. Of note, papaverine should not be injected into the cerebral circulation. (Intra-arterial nitroglycerine 100 to 200 µg can be used to reduce carotid vasospasm.)
spasm, a high-resistance flow state, or low graft flow velocity is detected, direct intra-arterial injection of papaverine (30 to 60 mg) can augment flow by reducing peripheral vascular resistance, thereby enhancing diagnostic accuracy for stenosis detection. Of note, papaverine should not be injected into the cerebral circulation. (Intra-arterial nitroglycerine 100 to 200 µg can be used to reduce carotid vasospasm.)
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
