Vascular applications of laser

Clinical Experience with a New Nitinol Self-Expanding Stent in Peripheral Arteries

Purpose:

To evaluate a new self-expanding nitinol coil stent in stenotic or occluded peripheral arteries.

Methods:

Seventy-three symptomatic patients (58 men; mean age 67 years) were treated with nitinol stents for lesions in the iliac artery (9 stenoses); superficial femoral artery (SFA) (39 stenoses, 6 occlusions); popliteal artery and tibioperoneal trunk (9 stenoses, 7 occlusions); and 3 bypass grafts. Mean diameter stenosis was 84.4% ± 9.9% (range 75% to 100%), and mean lesion length was 45 ± 23 mm (range 20 to 120 mm).

Results:

Eighty-eight 40-mm-long stents with diameters between 5 and 8 mm were implanted percutaneously for suboptimal dilation (n = 45); dissection (n = 21); and restenosis (n = 7). All stents but one were implanted successfully; the malpositioned stent was removed, and another stent was successfully deployed. There were 3 (4.1%) failures due to thrombosis at 24 hours. During the mean 16-month follow-up (range to 44 months), 4 restenoses (3 femoral, 1 popliteal) have occurred; 2 were treated with repeat dilation and 2 underwent bypass. Primary and secondary patency rates at 18 months were 87% and 90%, respectively, for all lesions (iliac: 100% for both; femoral: 85% and 88%; popliteal: 87% and 100%).

Conclusions:

This new nitinol stent seems to be safe and effective with favorable long-term results, even in distal SFA lesions and popliteal arteries. Its flexibility and resistance to external compression allow its placement in tortuous arteries and near joints.

Initial Experience with the Cragg Endopro System 1 for Intraluminal Treatment of Peripheral Vascular Disease

Purpose:

To evaluate the safety and efficacy of a new covered stent, the Cragg Endopro System 1, for intraluminal treatment of peripheral vascular disease in the iliac and femoropopliteal arteries.

Methods:

Forty symptomatic patients with predominantly lengthy stenotic (24) or occlusive (13) lesions or aneurysms (3) in the iliac (19), femoral (19), or popliteal (2) arteries were treated percutaneously with balloon angioplasty followed by implantation of the self-expanding nitinol Cragg stent covered by a woven polyester fabric coated with low-molecular-weight heparin. The mean length of femoropopliteal lesions was 13.0 ± 1.8 cm, as compared to 6.7 ± 0.8 cm (p < 0.01) for iliac lesions. Mean percent stenosis was 89% ± 2% with no significant difference between the arterial segments.

Results:

With a total of 52 covered stents implanted, technical success was achieved in 98% (39/40 patients). One tortuous femoral artery aneurysm was not satisfactorily excluded to prevent leakage. Clinical success was seen in all patients with demonstrable improvements in the claudication stage and the ankle-brachial index from a mean 0.54 to 0.92. Three local complications (one hematoma, two false aneurysms) required surgical repair. One distal embolism, one acute thrombosis, and three subacute thromboses were encountered and successfully treated by thrombolysis and/or surgery. One patient with two iliac stents developed contralateral common iliac artery occlusion from a stent partially obstructing the aorta; placement of a covered stent in the blocked artery re-established normal flow. Over an 8-month follow-up with arteriographic re-examination, all iliac stents remained patent. At the femoropopliteal level, two stents were occluded at 4 months; one was successfully dilated, but the other required surgical bypass grafting. A third patient developed a stenotic lesion proximal to the stent; dilation restored adequate inflow to the stent.

Conclusions:

The Cragg Endopro System 1 appears to be effective as an “internal bypass” for iliac and femoropopliteal occlusive disease. More complications and restenosis were seen in femoropopliteal implantations; however, a change in postoperative medication may improve these results. Long-term results will determine if the Cragg Endopro System 1 can achieve a patency equal to conventional bypass grafting.

Surgically Relevant Normal and Variant Renal Parenchymal and Vascular Anatomy in Preoperative 16-MDCT Evaluation of Potential Laparoscopic Renal Donors

OBJECTIVE

Using 16-MDCT, we describe and quantify the frequency and types of renal anatomic variants and findings relevant for preoperative evaluation and surgical planning for potential laparoscopic renal donors.

MATERIALS AND METHODS

On 16-MDCT, 126 consecutive potential donors underwent scanning before contrast administration and after i.v. power injection of nonionic contrast material during the arterial, nephrographic, and excretory phases. On a 3D workstation, CT images were evaluated retrospectively in consensus by three abdominal imagers. The number and branching pattern of bilateral renal arteries and veins, including anomalies of the inferior vena cava and lumbar-gonadal axis, were categorized along with the frequency of incidental findings of the renal parenchyma and collecting system.

RESULTS

Major arterial variants including supernumerary and early branching arteries were present in 16% and 21%, respectively, of left kidneys and 22% and 15%, respectively, of right kidneys. Major and minor venous variants were detected in 11% and 58% of left kidneys and 24% and 3% of right kidneys. Late confluence of the venous trunk was identified in 17% of left kidneys and 10% of right kidneys. Incidental parenchymal and urothelial abnormalities, most commonly cysts and calyceal calcifications, were identified in 30% of the kidneys. Other relevant incidental findings included focal infarcts, cortical scars, atrophic scarred kidney, and bilateral papillary necrosis. Urothelial variants included bilateral simple ureteroceles and rightsided complete duplicated collecting system.

CONCLUSION

16-MDCT angiography and urography allow confident detection and classification of a variety of anatomic and incidental anomalies relevant to the preoperative selection of potential laparoscopic renal donors and to surgical planning.

Fibromuscular dysplasia of the renal arteries: a radiological review

Fibromuscular dysplasia is the most common cause of renovascular hypertension in young patients. Digital subtraction angiography is still the best investigation used to determine the location, extent and complication of renal artery involvement. String of beads appearance (reflecting multiple stenoses), aneurysms, focal or tubular stenosis are classic angiographic appearances. The aim of this pictorial essay is to illustrate the various imaging findings of renal artery fibromuscular dysplasia.

Contrast-enhanced MR angiography and digital subtraction angiography in living renal donors: diagnostic agreement, impact on decision making, and costs

OBJECTIVE

The objective of our study was to evaluate the diagnostic agreement, the impact on decision making, and the costs of contrast-enhanced MR angiography and digital subtraction angiography in the workup of living renal donors.

CONCLUSION

Contrast-enhanced MR angiography for the preoperative evaluation of renal donors is superior to digital subtraction angiography in revealing vascular anomalies and depicting parenchymal abnormalities and is less costly; furthermore, it does not lead to preoperative decisions that differ from those based on digital subtraction angiography. If contrast-enhanced MR angiography does not provide sufficient information to make a confident decision, an additional digital subtraction angiography examination should be performed.

Fibromuscular dysplasia

The most common clinical manifestations of fibromuscular dysplasia (FMD) are hypertension due to renal artery involvement and transient ischemic attack or stroke due to carotid or vertebral artery involvement. Patients with renal artery FMD and hypertension should undergo primary angioplasty with the goal of curing the hypertension. If the blood pressure fails to normalize following angioplasty, the physician should institute antihypertensive medications according to the recommendations of the Joint National Committee on the Prevention, Detection, and Treatment of High Blood Pressure VII. In patients with cerebrovascular FMD, antiplatelet agents represent the cornerstone of therapy. Percutaneous angioplasty has emerged as the preferred treatment for symptomatic cerebrovascular FMD.

Rapid progression of native renal artery fibromuscular dysplasia following kidney donation

Fibromuscular dysplasia is the second commonest anatomical abnormality apart from multiple renal arteries in the potential live donors. Pretransplant evaluation of the donors may include an angiography to evaluate the renal arteries, and failure to recognize renal arterial stenosis, particularly fibromuscular dysplasia, by noninvasive methods may eventually lead to hypertension and ischemic renal failure. We report a case of fibromuscular dysplasia that was undetected by computed tomographic angiography prior to donation. One year after kidney donation, it rapidly progressed to severe symptomatic stenosis with hypertension and acute renal failure. Following renal artery angioplasty, her blood pressure normalized over a period of 2 weeks without any need for antihypertensive medications and the serum creatinine returned to her baseline. The acceptability of renal donors with fibromuscular dysplasia depends on the age, race and the availability of the other suitable donors. Mild fibromuscular dysplasia in a normotensive potential renal donor cannot be considered a benign condition. Such donors need regular follow-up postdonation for timely detection and treatment.

Fibromuscular hyperplasia as a cause of transplant renal artery stenosis

There are several causes of transplant renal artery stenosis, resulting in hypertension and renal dysfunction. Rarely, fibromuscular hyperplasia may cause such a presentation, and this case report discusses the historical, diagnostic and management issues pertaining to this rare situation.

Technology coverage decisions by health care plans and considerations by medical directors

OBJECTIVES

Decisions made by private health care plans as to whether to cover new medical technology have a significant impact on access, diffusion, and costs. This study describes the variation in health plan coverage of different laser technologies and the types of considerations used in making coverage decisions for them.

METHODS

In a cross-sectional national survey of medical directors at private plans, medical directors indicated current coverage of 15 different laser therapies, and then ranked the top five considerations both in favor and against recommending coverage for three of the laser therapies (angioplasty, discectomy, and photodynamic therapy). The influence of explicit clinical information and/or plan characteristics on coverage and the importance of considerations was examined through multivariate analyses (multiple logistic or linear regression analysis).

RESULTS

Overall, 231 medical directors responded from plans representing 66% and 72% of persons in US health maintenance organization and indemnity plans, respectively. Current coverage for 13 of the 15 laser therapies varied between 20% and 90%. For-profit and indemnity plans covered approximately two more of the different laser technologies than nonprofit plans and health maintenance organizations. Considerations most frequently listed in favor of and against recommending coverage across the three laser technologies were clinical, economic, and regulatory. Legal, competitive, and compassionate concerns were listed less frequently. Considerations were not uniform across laser therapies; they reflected the specifics of the technology under review. Plan characteristics influenced the ranking of considerations as well. For instance, health maintenance organizations were two to three times more likely than indemnity plans to list potential for decreased cost in favor of recommending coverage.

CONCLUSIONS

These findings demonstrate that there is substantial variation in coverage of new technologies, indicating that a large proportion of the population covered by private health plans are ineligible for treatments that are routinely available to others. A greater range of medical therapy may be available for persons enrolled in indemnity and for-profit plans should their physicians choose to prescribe it. Clinical and economic considerations, including cost-effectiveness, predominate in coverage decisions for new technologies. The importance of considerations appears sensitive not only to specific clinical information, however, but also to characteristics of health plans.

Clinical experience with a new nitinol self-expanding stent in peripheral arteries

PURPOSE

To evaluate a new self-expanding nitinol coil stent in stenotic or occluded peripheral arteries.

METHODS

Seventy-three symptomatic patients (58 men; mean age 67 years) were treated with nitinol stents for lesions in the iliac artery (9 stenoses); superficial femoral artery (SFA) (39 stenoses, 6 occlusions); popliteal artery and tibioperoneal trunk (9 stenoses, 7 occlusions); and 3 bypass grafts. Mean diameter stenosis was 84.4% +/- 9.9% (range 75% to 100%), and mean lesion length was 45 +/- 23 mm (range 20 to 120 mm).

RESULTS

Eighty-eight 40-mm-long stents with diameters between 5 and 8 mm were implanted percutaneously for suboptimal dilation (n = 45); dissection (n = 21); and restenosis (n = 7). All stents but one were implanted successfully; the malpositioned stent was removed, and another stent was successfully deployed. There were 3 (4.1%) failures due to thrombosis at 24 hours. During the mean 16-month follow-up (range to 44 months), 4 restenoses (3 femoral, 1 popliteal) have occurred; 2 were treated with repeat dilation and 2 underwent bypass. Primary and secondary patency rates at 18 months were 87% and 90%, respectively, for all lesions (iliac: 100% for both; femoral: 85% and 88%; popliteal: 87% and 100%).

CONCLUSIONS

This new nitinol stent seems to be safe and effective with favorable long-term results, even in distal SFA lesions and popliteal arteries. Its flexibility and resistance to external compression allow its placement in tortuous arteries and near joints.

Balloon-expandable endobypass for femoropopliteal atherosclerotic occlusive disease. A preliminary evaluation of fifty-five patients

PURPOSE

The purpose of this study was to evaluate the early results of a newly developed endovascular technique for the treatment of superficial femoral artery occlusion.

METHODS

Fifty-five patients with total occlusion of the superficial femoral artery with patent popliteal artery were treated and evaluated over a 21-month period. The endovascular treatment was performed through a groin incision and consisted of a recanalization of the occluded femoral artery, balloon dilatation, and intraluminal placement of a 3-mm polytetrafluoroethylene graft, distal fixation with a stent, dilation of the graft, and proximal suture anastomosis in the common femoral artery.

RESULTS

At a 1-year follow-up the Kaplan-Meier method revealed a primary patency rate of 73.1% (95% confidence limits: 59.6 to 86.6) and a secondary patency rate of 86.3% (range 75.8% to 96.9%). The procedure morbidity rate was 3.6%; the mortality and amputation rate at 12 months was nil.

CONCLUSIONS

The early 1-year results of this endovascular study support the concept that femoropopliteal endobypass for atherosclerotic occlusive disease may be an acceptable alternative to classic direct femoropopliteal bypass operations. Further study is necessary.

The significance of increased 111indium platelet accumulation at post-angioplasty sites

We assessed prospectively the significance of 111indium labelled platelet accumulation following angioplasty procedures in 12 patients (9 femoral angioplasties (2 laser, 1 atherectomy) and 3 iliac stents). Autologous 111indium labelled platelets were re-injected immediately after angioplasty. Radioactivity was measured over treated and reference sites, by single probe and gamma camera, and expressed as a radioactivity ratio (RR). All patients had duplex ultrasound assessment and occlusions were confirmed by arteriography. RR was always raised after angioplasty. Three patients who had acute occlusions showed markedly raised average RRs (significant at 99% ANOVA). RR was not raised after laser assisted angioplasty, however, our numbers were small. 111Indium platelet radioactivity did not predict subsequent occlusion after angioplasty but effectively detected existing acute post-angioplasty occlusions.

Prevention of intimal hyperplasia by irradiation. An experimental study in rabbits

PURPOSE

This experimental study was designed to investigate the effect of irradiation in prevention of intimal hyperplasia.

MATERIAL AND METHODS

Twenty rabbits were divided into 4 groups, which were irradiated with 2, 5, 10 and 20 Gy, respectively. The intima of both femoral arteries was injured by air-drying, and irradiation was performed on the unilateral side. The contralateral+ femoral artery served as a control. Angiograms as well as histologic specimens were obtained 1 month later.

RESULTS

Marked intimal hyperplasia was observed in all control sites. There were no significant differences in thickness of intimal hyperplasia between irradiated and control sites in groups irradiated with 2 and 5 Gy. However, in the 10-Gy- and 20-Gy-irradiated groups, intimal hyperplasia of the irradiated site was significantly suppressed. Medial thinning and dilation of the lumen were observed in the 20-Gy-irradiated group.

CONCLUSION

Radiation may prevent intimal hyperplasia. Further investigation of the optimal dose, timing of irradiation, and long-term patency of irradiated vessels may be needed.

Do hydrophilic guidewires affect the technical success rates of percutaneous angioplasty?

To determine whether the use of hydrophilic guidewires has influenced the success of peripheral percutaneous transluminal angioplasty (PTA), the results of PTA performed before and after the introduction of such guidewires (end of 1989) were analyzed. Before hydrophilic guidewires became generally available, the technical success rates for iliac stenosis PTA were 96%, for femoral stenosis PTA 84%, and for femoral occlusion 78%. After the introduction of hydrophilic guidewires, technical success rates were 100% (NS), 97% (P = 0.018), and 97% (P = 0.011), respectively. A prospective study of 33 patients randomly selected for PTA of femoropopliteal occlusion using either conventional or hydrophilic guidewires was performed. In this group, the technical success rate was 14/15 in the hydrophilic group, and 18/18 in the conventional group (NS). Since the introduction of hydrophilic guidewires, the technical success rates of PTA have improved and are now approaching 100%.

Initial experience with the Cragg Endopro System 1 for intraluminal treatment of peripheral vascular disease

PURPOSE

To evaluate the safety and efficacy of a new covered stent, the Cragg Endopro System 1, for intraluminal treatment of peripheral vascular disease in the iliac and femoropopliteal arteries.

METHODS

Forty symptomatic patients with predominantly lengthy stenotic (24) or occlusive (13) lesions or aneurysms (3) in the iliac (19), femoral (19), or popliteal (2) arteries were treated percutaneously with balloon angioplasty followed by implantation of the self-expanding nitinol Cragg stent covered by a woven polyester fabric coated with low-molecular-weight heparin. The mean length of femoropopliteal lesions was 13.0 +/- 1.8 cm, as compared to 6.7 +/- 0.8 cm (p < 0.01) for iliac lesions. Mean percent stenosis was 89% +/- 2% with no significant difference between the arterial segments.

RESULTS

With a total of 52 covered stents implanted, technical success was achieved in 98% (39/40 patients). One tortuous femoral artery aneurysm was not satisfactorily excluded to prevent leakage. Clinical success was seen in all patients with demonstrable improvements in the claudication stage and the ankle-brachial index from a mean 0.54 to 0.92. Three local complications (one hematoma, two false aneurysms) required surgical repair. One distal embolism, one acute thrombosis, and three subacute thromboses were encountered and successfully treated by thrombolysis and/or surgery. One patient with two iliac stents developed contralateral common iliac artery occlusion from a stent partially obstructing the aorta; placement of a covered stent in the blocked artery re-established normal flow. Over an 8-month follow-up with arteriographic re-examination, all iliac stents remained patent. At the femoropopliteal level, two stents were occluded at 4 months; one was successfully dilated, but the other required surgical bypass grafting. A third patient developed a stenotic lesion proximal to the stent; dilation restored adequate inflow to the stent.

CONCLUSIONS

The Cragg Endopro System 1 appears to be effective as an "internal bypass" for iliac and femoropopliteal occlusive disease. More complications and restenosis were seen in femoropopliteal implantations; however, a change in postoperative medication may improve these results. Long-term results will determine if the Cragg Endopro System 1 can achieve a patency equal to conventional bypass grafting.

Percutaneous femoropopliteal graft placement

PURPOSE

Femoropopliteal bypass surgery is now recommended for the treatment of long-segment or diffuse superficial femoral artery disease. The authors describe a technique for percutaneous placement of a prosthetic femoropopliteal graft.

PATIENTS AND METHODS

The technique has been accomplished with conventional polytetrafluoroethylene graft material and a variety of implantation techniques in eight patients.

RESULTS

Technical success was achieved in all patients who underwent graft placement. Grafts up to 28 cm in length were placed, and graft patency was demonstrated up to 10 months after implantation. Six of the eight patients were asymptomatic during the follow-up period; one patient who had symptoms during this time underwent thrombolysis and redilation of the distal stent, and the symptoms resolved. In the other patient with symptoms, the procedure failed clinically because of poor runoff.

CONCLUSION

This study demonstrates the feasibility of percutaneous graft placement in the femoral artery, but durability must be established in relation to traditional bypass surgery before it can be recommended on a wider scale.

Peripheral angioplasty balloon technology

Changes in balloon and catheter technology have led to the development of smaller, more flexible, and less traumatic balloon dilatation systems. The physical principles that govern balloon angioplasty and the current status of balloon materials and catheter designs will be reviewed. A compilation of various angioplasty catheters is also summarized.

Use of laser energy to treat central pulmonary emboli: a preliminary report

We evaluated the ability and safety of a laser fiber placed percutaneously into a pig's lobar pulmonary artery to lyse pulmonary artery blood clots that were created in situ. We developed a model to create blood clots in situ that could be placed in any desired location with a radio-opaque marker at the clot position. An excimer laser delivered energy to a flexible 600 microns fiber in three experiments and a coaxial 1.6 mm multifiber catheter in the last experiment. Pre- and postprocedure angiograms obtained from each experiment demonstrated that partial laser dissolution of central pulmonary emboli in four pigs was accomplished successfully. To avoid perforation, it is imperative that the laser fiber remain coaxial during the entire lasing process. These results suggest that laser dissolution may become an adjunctive procedure for the treatment of central pulmonary emboli in those patients who cannot be treated medically.

Effect of antineoplastic agents on smooth muscle cell proliferation in vitro: implications for prevention of restenosis after transluminal angioplasty

The effect of several antineoplastic agents on vascular smooth muscle cell proliferation was studied in vitro. Both fluorouracil and cytarabine produced significant concentration-dependent inhibition of smooth muscle cell proliferation in cultured porcine pulmonary artery in vitro, while cyclophosphamide stimulated growth. For fluorouracil, inhibition was near maximal at a concentration of 13.0 microgram/mL and was seen with both coincubation and 2-hour preincubation of fluorouracil with quiescent cells. Fluorouracil is a promising agent for inhibition of intimal proliferation. Further work is warranted to determine its effect in vivo.

Laser-assisted balloon angioplasty in complete femoropopliteal occlusions: preliminary results

Laser-assisted balloon angioplasty (LA) using a Nd-YAG laser with a sapphire tip probe was performed in 40 selected patients with complete chronic femoropopliteal occlusions (SFA n = 30, PA n = 10), in whom the lesion was resistant to conventional guidewire/catheter traversal. Overall technical success rate was 77.5% (31/40). Technical failure occurred in nine cases due to calcifications (n = 2), imminent perforation (n = 5), or complete perforation (n = 4). In 1 case a Simpson atherectomy was done following LA. In addition, 3 cases of peripheral embolizations were managed successfully by selective fibrinolysis and thrombus aspiration. Follow-up studies up to 14 months demonstrated a clinical improvement in 87% (27/31). Early reocclusion rate was 4/31; after 2-14 months, reocclusion rate was 7/31. Our results demonstrate that LA may be recommended for chronic occlusions resistant to conventional guidewire or catheter traversal in spite of a relatively high rate of technical failure and complications, and recurrence.

Current and future trends in laser medicine

In this overview, a number of the major current, and possible future developments in laser medicine are explored. In therapeutic applications, particular emphasis is given to obtaining selectivity in tissue targets and interaction mechanisms in order to achieve specific biological effects. This includes spatial confinement of thermal damage by pulsed laser irradiation and targetting by exogenous photothermal or photochemical chromophores. The potential for diagnostic applications of lasers in medicine is illustrated primarily by various in vivo spectroscopic techniques. Both therapeutic and diagnostic applications will rely increasingly on the development of total systems in which lasers will form only one, albeit an essential, part. Numerous scientific and technical problems need to be solved in order to realize the full clinical potential of the many new concepts in laser medicine. The impetus for such progress will come from integrated, multidisciplinary collaborations between medical, scientific and industrial groups.

Angioplasty after laser perforation

Perforation is the most important complication of laser angioplasty and leads to a decrease in success because the procedure has to be discontinued. In 3 patients we continued despite perforation and were able to stop extravasation with percutaneous transluminal angioplasty (PTA) and to finish the procedure with a good final result. From our experience we conclude that laser perforation is not an absolute indication to stop the procedure if PTA in the recanalized lumen is possible.

Comparison of balloon angioplasty and laser thermal angioplasty in the treatment of femoropopliteal atherosclerotic disease: initial results of a prospective randomized trial. Work in progress

The authors recently initiated a prospective randomized trial in which results of standard balloon angioplasty were compared with those of laser thermal angioplasty in the treatment of patients with symptoms of femoropopliteal occlusive disease. The data regarding their initial technical success are reported herein. Twenty-five patients with moderate to severe claudication have thus far undergone 27 procedures. The type of lesions treated varied from short focal stenoses to occlusions up to 10 cm in length; 12 stenoses and 15 occlusions were treated. Fourteen procedures were randomized to laser therapy and 13 to standard balloon angioplasty. If the primary randomized treatment failed, the alternative procedure was then attempted. Of the 14 laser procedures, five were initial failures; three of these failures were subsequently treated successfully with the balloon technique. Three of 13 balloon procedures were failures; none were subsequently successful with use of the laser. While these data are limited, initial experience indicates that technical success is directly related to the ability to pass an angiographic wire through the lesion and the length and type of lesions. It does not appear to depend on whether the laser or the balloon is used.

Percutaneous management of emboli associated with hot tip laser-assisted angioplasty

We describe the percutaneous management of emboli that occurred in 3 patients during hot tip laser-assisted angioplasty procedures. One embolus was lysed with direct, local infusion of urokinase using an open-ended guidewire. Another embolus was removed using the transcatheter aspiration technique. The third embolus was partially lysed and then, using a steerable guidewire, displaced placed into a distal side branch. In all 3 cases of embolization, distal blood flow was reestablished using percutaneous techniques, obviating the need for surgical intervention.