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Endovascular Surgery for Occlusive Disease
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Peripheral Arterial
A Critical Review SAMUEL S. AHN, M.D., DARWIN ETON, M.D., and WESLEY S. MOORE, M.D.
Endovascular surgery is a new multidisciplinary field that applies the recently innovated techniques of angioscopy, intraluminal ultrasound, balloon angioplasty, laser, mechanical atherectomy, and stents. This field can be defined as a diagnostic and therapeutic discipline that uses catheter-based systems to treat vascular disease. As such, it integrates the subspecialties of vascular surgery, interventional radiology, interventional cardiology, and biomedical engineering for the common purpose of improving arterial hemodynamics. Endovascular surgery offers many potential benefits: long incisions are replaced with a puncture wound, the need for postoperative intensive care is significantly reduced, major cardiac and pulmonary complications from general anesthesia are side stepped, and the dollar savings could be dramatic as the need for intensive care unit and in-hospital stay diminishes. Despite these technological advancements, endovascular surgery is still in its infancy and currently has limited applications. This review provides an updated summary of endovascular surgery today and addresses some of the obstacles
From the Section of Vascular Surgery, UCLA Center for the Health Sciences, Los Angeles, California
valvulotomy and identification of side branches.7-'0 Integrated angioscopy/valvulotomy systems" with capabilities for side branch occlusion are being tested. Vascular endoscopy cannot visualize small runoff vessels, provide information on atheroma composition, or estimate percent stenosis. Images of a lumen visualized remotely may look quite small, whereas a lumen visualized close up may look quite large. Also, without fluoroscopy, it may be difficult to judge exactly where one is imaging. Furthermore, some injury to the intimal surface is inevitable while using the angioscope, the significance of which is not known yet. One should avoid a scopeartery size mismatch to minimize mechanical trauma, and long periods of illumination without irrigation to minimize thermal injury. Finally, excessive irrigation and volume overload must be avoided.
still preventing its widespread use. VAS ASCULAR ENDOSCOPY PROVIDES real-time color
images ofintra-arterial anatomy. The equipment consists of a flexible fiberoptic angioscope, a light source, irrigation system, camera, video recorder, and monitor, often mounted on a compact mobile cart. The angioscopy identifies intraluminal pathology, thereby assisting the interventionalist to judge the nature of the lesion before a procedure and then to follow the progress of the intervention. It has been helpful in monitoring the completeness of thrombectomy, 2 endarterectomy," 3 laser-assisted balloon angioplasty (LABA),4 and mechanical atherectomy.5 It also has been helpful in guiding flexible "cutters" and "grabbers" to retrieve thrombus, intimal flaps, atherosclerotic plaques, or even foreign bodies.6 During saphenous vein preparation for in situ lower extremity bypass, angioscopy has facilitated
Intravascular Ultrasound The equipment consists of a flexible catheter connected to a drive unit, a signal processor, a monitor, and a recorder. The catheter tip contains a millimeter-sized transducer that acts as a transmitter and receiver to interrogate the entire perimeter of the artery repetitively. Thus, whereas angioscopy assesses only the luminal topography, intravascular ultrasonography provides information about lesions beneath the luminal surface,'2 allowing the interventionalist the opportunity to select the most appropriate therapeutic instrument based on lesion composition. Furthermore, percent stenosis can be evaluated precisely, allowing one to pinpoint hemodynamically significant lesions for intervention. Also as an adjunct to endovascular procedures, intravascular ultrasonography can determine the completeness of atherectomy and angioplasty. The Simpson directional atherectomy catheter and some bal-
Address reprint requests to Samuel S. Ahn, M.D., Section of Vascular Surgery, UCLA Center for the Health Sciences, 10833 Le Conte Avenue, Los Angeles, CA 90024. Accepted for publication November 5, 1991.
3
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AHN, ETON, AND MOORE
loon angioplasty catheters already have prototypes that integrate ultrasonography into their design. Yock et al have also used ultrasonography to evaluate the precision of stent expansion.'2 Unlike angioscopy, ultrasonography is not hampered by blood flow. All air needs to be flushed from the system to prevent artifact, however. The most difficult part of intraluminal ultrasound is obtaining a clear signal. In some models, artifacts can occur by inadvertently looping the catheter on itself, or by selecting a catheter that is so long that it may serve as an antenna to pick up ambient electrical noise. Finally, air bubbles distort the image and must be avoided. Once a good signal is obtained, correct interpretation requires patience and experience. Pitfalls occur in differentiating fat, fresh thrombus, and dissection planes, all of which are not echogenic. Additionally, in calcified arteries, the shadow behind the calcium can obscure underlying wall details and prevent accurate area measurement. Lastly, there is no "look ahead" capability without moving the catheter forward. The size of artery that can be imaged is limited by catheter size, the arterial size, and the tightness of the stenosis.
Percutaneous Transluminal Angioplasty Introduction Percutaneous transluminal angioplasty (PTA) is being used at an increasing rate to treat peripheral vascular disease, with estimates of 120,000 procedures/year in 1990.'" Rather than compressing the atheroma, balloon angioplasty cracks the confining atherosclerotic intimal shell and stretches the freed underlying medial to enlarge the lumen. The medial smooth muscles, elastin, and collagen fibers are damaged in the process. The enlarged vessel's new dimensions are maintained by the increased pulsatile luminal blood flow.
Technique The PTA catheter selection parameters include balloon diameter, balloon length, balloon distention pressure, catheter circumference, and catheter length. These are selected based on the size of the native artery, the length of the stenosis, the balloon properties, the per cent stenosis, and the lesion distance from the access site, respectively. Although multiple dilations of sequential lesions are feasible, matching the length of a diffusely stenotic segment to the length of the PTA balloon is optimal to prevent injury to the lesser or nondiseased adjoining vessel. After proper placement of the balloon across the lesion, balloon inflation is performed manually with contrast so that the contour of the balloon can be watched fluoroscopically during dilatation. Hand-held units calibrated in atmospheres are available. The recommended inflation pressure is usually written on the PTA catheter package.
Ann. Surg. * July 1992
The time it takes for the residual stenosis ("waist") to go away depends on the composition of the lesion, the rate of inflation, and the balloon pressure. The procedure is usually repeated at least once. If on deflating the balloon the stenosis recurs, further PTA may be performed, maybe at a higher pressure or with a larger balloon. Occasionally a stent may be applied. Seeing a dissection angiographically is typical after successful PTA. Angioscopically, intimal flaps as well as mural thrombus may be seen. The hemodynamic success of the PTA is ascertained by measuring the pressure gradient across the treated lesion. Pharmacologic support used during PTA includes anticoagulants such as heparin, dextran, aspirin, and Persantine (Boehringer Ingelheim, Ridgefield, CT), and spasmolytic agents such as calcium channel blockers, nitroglycerine, papaverine, and tolazoline.
Results Percutaneous transluminal angioplasty has been used with varying success to treat hemodynamically significant lesions, aortic, iliac, femoral, popliteal, mesenteric, and renal circulations as well as hemodialyis arteriovenous shunts. Results for PTA at select levels are summarized below. Aorta. Johnston et al.'4 reported 3-year patency rates of 70% after PTA in 17 patients. Belli et al.5 described successful PTA ofinfrarenal abdominal aortic stenoses in 13 patients. No complications occurred, and no restenosis was seen with follow-up 7 to 70 months later (mean = 27 months). Iliac. Van Andel et al.'6 reported a 95% initial success rate and a 90% patency at 7 years for 154 patients treated for favorable iliac disease.'6 Johnston et al.'4 reported 5year patency rates for all PTA-treated lesions of 59% in the common iliac artery and 47% in the external iliac artery. Zeitler et al.'7 reported a 50% 5-year patency after iliac artery PTA (80% in patients with claudication). Samson et al.'8 reported patency rates for 61 initially successful PTAs (69 attempts): 91% at 6 months, 86% at 1 year, and 78% at 2 to 4 years. Most (90%) of these patients were in a limb salvage situation. Two limbs eventually were amputated. Kumpe and Rutherford'9 reported a 5year patency of at least 80% for discrete stenoses, and 50% to 60% for diffuse stenoses. Results were better in the common than in the external iliac artery. Percutaneous transluminal angiography of iliac occlusions (as opposed to stenoses) was addressed by Colapinto et al.20 Initial success was 78%, and 4-year cumulative patency of the successfully treated lesions was 78%. The length ofthe occlusion adversely impacted initial success, but not long-term patency. There was a 3% incidence of peripheral embolization requiring surgical intervention.
Vol. 216 -No. I
ENDOVASCULAR SURGERY
Other studies report 20% to 50% higher incidences of embolization requiring surgery and thus do not recommend dilation of longer occlusions.2' Iliac occlusions may be more safely treatable by PTA once the thrombus is lysed and an underlying short iliac stenosis is uncovered.22'23 Femoropopliteal. Morgenstern et al.24 reported a technical success rate of 95% (39/41) for lesions 1 to 4 cm long, and 86% (25/29) for lesions 5 to 10 cm long. Zeitler et al.'7 reported a 68% (90/133) technical success rate for lesions greater than 10 cm long. Patency data are not as impressive, however. Adar et al.25 analyzed multiple studies and, using the Confidence Profile Method, reported that the largest decline of patency after femoropopliteal PTA occurred within the first 6 to 12 months. After 2 years there was little further attrition. Three-year patency was 62% ± 9% for patients with intermittent claudication, and 43% ± 7% for limb salvage. Reported 5-year patency rates vary from 39% to 70%.15,19,26 Sampson et al.'8 reported patency rates of 73% at 6 months, 54% at 1 year, and 50% at 2 to 4 years. Most (90%) of these patients were in a limb salvage situation. Six limbs eventually were amputated. Johnston et al.'4 reported 5year patency rates for all PTA-treated lesions of 39%. They also reported a 3-year patency rate of 37% (n = 18) after PTA of the common femoral artery, and a 1-year patency of 23% (n = 13) after PTA of the profunda femoris artery. The primary determinant of patency appears to be the length of the diseased segment. Long-term patency rates as high as 70% have been reported for focal short (
I
Endovascular Surgery for Occlusive Disease
VAa
Mi i
Ija
U
Peripheral Arterial
A Critical Review SAMUEL S. AHN, M.D., DARWIN ETON, M.D., and WESLEY S. MOORE, M.D.
Endovascular surgery is a new multidisciplinary field that applies the recently innovated techniques of angioscopy, intraluminal ultrasound, balloon angioplasty, laser, mechanical atherectomy, and stents. This field can be defined as a diagnostic and therapeutic discipline that uses catheter-based systems to treat vascular disease. As such, it integrates the subspecialties of vascular surgery, interventional radiology, interventional cardiology, and biomedical engineering for the common purpose of improving arterial hemodynamics. Endovascular surgery offers many potential benefits: long incisions are replaced with a puncture wound, the need for postoperative intensive care is significantly reduced, major cardiac and pulmonary complications from general anesthesia are side stepped, and the dollar savings could be dramatic as the need for intensive care unit and in-hospital stay diminishes. Despite these technological advancements, endovascular surgery is still in its infancy and currently has limited applications. This review provides an updated summary of endovascular surgery today and addresses some of the obstacles
From the Section of Vascular Surgery, UCLA Center for the Health Sciences, Los Angeles, California
valvulotomy and identification of side branches.7-'0 Integrated angioscopy/valvulotomy systems" with capabilities for side branch occlusion are being tested. Vascular endoscopy cannot visualize small runoff vessels, provide information on atheroma composition, or estimate percent stenosis. Images of a lumen visualized remotely may look quite small, whereas a lumen visualized close up may look quite large. Also, without fluoroscopy, it may be difficult to judge exactly where one is imaging. Furthermore, some injury to the intimal surface is inevitable while using the angioscope, the significance of which is not known yet. One should avoid a scopeartery size mismatch to minimize mechanical trauma, and long periods of illumination without irrigation to minimize thermal injury. Finally, excessive irrigation and volume overload must be avoided.
still preventing its widespread use. VAS ASCULAR ENDOSCOPY PROVIDES real-time color
images ofintra-arterial anatomy. The equipment consists of a flexible fiberoptic angioscope, a light source, irrigation system, camera, video recorder, and monitor, often mounted on a compact mobile cart. The angioscopy identifies intraluminal pathology, thereby assisting the interventionalist to judge the nature of the lesion before a procedure and then to follow the progress of the intervention. It has been helpful in monitoring the completeness of thrombectomy, 2 endarterectomy," 3 laser-assisted balloon angioplasty (LABA),4 and mechanical atherectomy.5 It also has been helpful in guiding flexible "cutters" and "grabbers" to retrieve thrombus, intimal flaps, atherosclerotic plaques, or even foreign bodies.6 During saphenous vein preparation for in situ lower extremity bypass, angioscopy has facilitated
Intravascular Ultrasound The equipment consists of a flexible catheter connected to a drive unit, a signal processor, a monitor, and a recorder. The catheter tip contains a millimeter-sized transducer that acts as a transmitter and receiver to interrogate the entire perimeter of the artery repetitively. Thus, whereas angioscopy assesses only the luminal topography, intravascular ultrasonography provides information about lesions beneath the luminal surface,'2 allowing the interventionalist the opportunity to select the most appropriate therapeutic instrument based on lesion composition. Furthermore, percent stenosis can be evaluated precisely, allowing one to pinpoint hemodynamically significant lesions for intervention. Also as an adjunct to endovascular procedures, intravascular ultrasonography can determine the completeness of atherectomy and angioplasty. The Simpson directional atherectomy catheter and some bal-
Address reprint requests to Samuel S. Ahn, M.D., Section of Vascular Surgery, UCLA Center for the Health Sciences, 10833 Le Conte Avenue, Los Angeles, CA 90024. Accepted for publication November 5, 1991.
3
4
AHN, ETON, AND MOORE
loon angioplasty catheters already have prototypes that integrate ultrasonography into their design. Yock et al have also used ultrasonography to evaluate the precision of stent expansion.'2 Unlike angioscopy, ultrasonography is not hampered by blood flow. All air needs to be flushed from the system to prevent artifact, however. The most difficult part of intraluminal ultrasound is obtaining a clear signal. In some models, artifacts can occur by inadvertently looping the catheter on itself, or by selecting a catheter that is so long that it may serve as an antenna to pick up ambient electrical noise. Finally, air bubbles distort the image and must be avoided. Once a good signal is obtained, correct interpretation requires patience and experience. Pitfalls occur in differentiating fat, fresh thrombus, and dissection planes, all of which are not echogenic. Additionally, in calcified arteries, the shadow behind the calcium can obscure underlying wall details and prevent accurate area measurement. Lastly, there is no "look ahead" capability without moving the catheter forward. The size of artery that can be imaged is limited by catheter size, the arterial size, and the tightness of the stenosis.
Percutaneous Transluminal Angioplasty Introduction Percutaneous transluminal angioplasty (PTA) is being used at an increasing rate to treat peripheral vascular disease, with estimates of 120,000 procedures/year in 1990.'" Rather than compressing the atheroma, balloon angioplasty cracks the confining atherosclerotic intimal shell and stretches the freed underlying medial to enlarge the lumen. The medial smooth muscles, elastin, and collagen fibers are damaged in the process. The enlarged vessel's new dimensions are maintained by the increased pulsatile luminal blood flow.
Technique The PTA catheter selection parameters include balloon diameter, balloon length, balloon distention pressure, catheter circumference, and catheter length. These are selected based on the size of the native artery, the length of the stenosis, the balloon properties, the per cent stenosis, and the lesion distance from the access site, respectively. Although multiple dilations of sequential lesions are feasible, matching the length of a diffusely stenotic segment to the length of the PTA balloon is optimal to prevent injury to the lesser or nondiseased adjoining vessel. After proper placement of the balloon across the lesion, balloon inflation is performed manually with contrast so that the contour of the balloon can be watched fluoroscopically during dilatation. Hand-held units calibrated in atmospheres are available. The recommended inflation pressure is usually written on the PTA catheter package.
Ann. Surg. * July 1992
The time it takes for the residual stenosis ("waist") to go away depends on the composition of the lesion, the rate of inflation, and the balloon pressure. The procedure is usually repeated at least once. If on deflating the balloon the stenosis recurs, further PTA may be performed, maybe at a higher pressure or with a larger balloon. Occasionally a stent may be applied. Seeing a dissection angiographically is typical after successful PTA. Angioscopically, intimal flaps as well as mural thrombus may be seen. The hemodynamic success of the PTA is ascertained by measuring the pressure gradient across the treated lesion. Pharmacologic support used during PTA includes anticoagulants such as heparin, dextran, aspirin, and Persantine (Boehringer Ingelheim, Ridgefield, CT), and spasmolytic agents such as calcium channel blockers, nitroglycerine, papaverine, and tolazoline.
Results Percutaneous transluminal angioplasty has been used with varying success to treat hemodynamically significant lesions, aortic, iliac, femoral, popliteal, mesenteric, and renal circulations as well as hemodialyis arteriovenous shunts. Results for PTA at select levels are summarized below. Aorta. Johnston et al.'4 reported 3-year patency rates of 70% after PTA in 17 patients. Belli et al.5 described successful PTA ofinfrarenal abdominal aortic stenoses in 13 patients. No complications occurred, and no restenosis was seen with follow-up 7 to 70 months later (mean = 27 months). Iliac. Van Andel et al.'6 reported a 95% initial success rate and a 90% patency at 7 years for 154 patients treated for favorable iliac disease.'6 Johnston et al.'4 reported 5year patency rates for all PTA-treated lesions of 59% in the common iliac artery and 47% in the external iliac artery. Zeitler et al.'7 reported a 50% 5-year patency after iliac artery PTA (80% in patients with claudication). Samson et al.'8 reported patency rates for 61 initially successful PTAs (69 attempts): 91% at 6 months, 86% at 1 year, and 78% at 2 to 4 years. Most (90%) of these patients were in a limb salvage situation. Two limbs eventually were amputated. Kumpe and Rutherford'9 reported a 5year patency of at least 80% for discrete stenoses, and 50% to 60% for diffuse stenoses. Results were better in the common than in the external iliac artery. Percutaneous transluminal angiography of iliac occlusions (as opposed to stenoses) was addressed by Colapinto et al.20 Initial success was 78%, and 4-year cumulative patency of the successfully treated lesions was 78%. The length ofthe occlusion adversely impacted initial success, but not long-term patency. There was a 3% incidence of peripheral embolization requiring surgical intervention.
Vol. 216 -No. I
ENDOVASCULAR SURGERY
Other studies report 20% to 50% higher incidences of embolization requiring surgery and thus do not recommend dilation of longer occlusions.2' Iliac occlusions may be more safely treatable by PTA once the thrombus is lysed and an underlying short iliac stenosis is uncovered.22'23 Femoropopliteal. Morgenstern et al.24 reported a technical success rate of 95% (39/41) for lesions 1 to 4 cm long, and 86% (25/29) for lesions 5 to 10 cm long. Zeitler et al.'7 reported a 68% (90/133) technical success rate for lesions greater than 10 cm long. Patency data are not as impressive, however. Adar et al.25 analyzed multiple studies and, using the Confidence Profile Method, reported that the largest decline of patency after femoropopliteal PTA occurred within the first 6 to 12 months. After 2 years there was little further attrition. Three-year patency was 62% ± 9% for patients with intermittent claudication, and 43% ± 7% for limb salvage. Reported 5-year patency rates vary from 39% to 70%.15,19,26 Sampson et al.'8 reported patency rates of 73% at 6 months, 54% at 1 year, and 50% at 2 to 4 years. Most (90%) of these patients were in a limb salvage situation. Six limbs eventually were amputated. Johnston et al.'4 reported 5year patency rates for all PTA-treated lesions of 39%. They also reported a 3-year patency rate of 37% (n = 18) after PTA of the common femoral artery, and a 1-year patency of 23% (n = 13) after PTA of the profunda femoris artery. The primary determinant of patency appears to be the length of the diseased segment. Long-term patency rates as high as 70% have been reported for focal short (
