Transluminal atherectomy for occlusive peripheral vascular disease

Effect of lesion characteristics on outcome of directional coronary atherectomy

Directional coronary atherectomy, a new transluminal procedure for treatment of obstructive lesions in coronary arteries by excision and removal of tissue, was performed on 447 lesions in 382 procedures. Successful outcome, defined as a reduction of stenosis by greater than or equal to 20% with a less than 50% residual stenosis, was achieved in 89.5% of lesions and mean stenosis was reduced from 75.9 +/- 13.3% to 14.5 +/- 22.1% (p less than 0.001). Complications included vessel occlusion during the procedure, 2.4%; vessel occlusion after the procedure, 1.3%; new lesion, 0.5%; nonobstructive guiding catheter-induced dissection, 0.3%; perforation, 0.8%; distal embolization, 2.1%; Q wave myocardial infarction, 0.8% and non-Q wave myocardial infarction, 4.2%. Twelve patients (3.1%) required coronary artery bypass surgery for these complications. The atherectomy success rate was greater than 80% and the combined atherectomy and angioplasty success rate was greater than 90% for complex morphologic features such as eccentric lesions, lengthy lesions, lesions with abnormal contour, angulated lesions, ostial lesions and lesions with branch involvement. In the presence of calcific deposition, atherectomy success rate was 52% for primary lesions and 83% for restenosed lesions. Among angiographically complex lesions, calcium was the predictor for failed atherectomy (p less than 0.0001). In summary, directional coronary atherectomy is safe and effective for treatment of obstructive lesions in coronary arteries in selected cases. In particular, it achieves a high success rate in lesions with complex morphologic characteristics, such as eccentricity, abnormal contour and ostial involvement.

Long-term follow-up of the first 56 patients treated with intracoronary self-expanding stents (the Lausanne experience)

Fifty-six patients treated with the self-expanding intracoronary stent for acute occlusion during percutaneous transluminal coronary angioplasty (PTCA) or restenosis were followed for 24 to 43 months (mean 34). Successful deployment and positioning were achieved in 55 of 56 patients. Occlusion of the stent was documented in 8 patients, the earliest occurring 30 minutes and the latest 8 months after implantation. Three of the occluded stents were recanalized by PTCA. Coronary artery bypass grafts (CABG) were required in 4 patients: 1 for symptomatic restenosis, 1 for left main stenosis adjacent to the stent and 2 for acute ischemia during the in-hospital stay (less than 7 days). Myocardial infarction occurred in the territory of the stented vessel in 8 patients. Seven patients died between 1 day and 19 months after implantation. Local bleeding complications occurred in 10 patients, with 5 requiring blood transfusion. Restenosis within the stent was angiographically documented in 5 patients (9%). A new lesion in the treated vessel was found in 10 patients, followed by implantation of a second stent in 5 and a third stent in 1 patient. Medical treatment was instituted in the remaining 4 patients. Forty-nine patients (88%) are alive. Twenty-nine patients (51%) remained asymptomatic, and 44 (78%) are in a better functional class than before the implantation. Eleven of 15 (79%) major complications (acute occlusions or deaths) occurred in patients who received a stent in the left anterior descending coronary artery. In conclusion, implantation of the self-expanding intracoronary stent appears to be a new therapeutic option for treating acute occlusion or restenosis after PTCA.(ABSTRACT TRUNCATED AT 250 WORDS)

A paradigm for restenosis based on cell biology: clues for the development of new preventive therapies

Angioplasty causes substantial injury to the coronary artery intima and media that is unrecognizable by angiography. On the basis of a substantial body of research in oncology and wound healing, it is hypothesized that restenosis is a manifestation of the general wound healing response expressed specifically in vascular tissue. The temporal response to injury occurs in three characteristic phases: inflammation, granulation and extracellular matrix remodeling. The specific expression of these phases in the coronary artery leads to intimal hyperplasia at 1 to 4 months. The major milestones in the temporal sequence of restenosis are platelet aggregation, inflammatory cell infiltration, release of growth factors, medial smooth muscle cell modulation and proliferation, proteoglycan deposition and extracellular matrix remodeling. Each step has potential inhibitors that could be used for preventive therapy. Resolution of restenosis, however, probably requires both creation of the largest possible residual lumen and substantial inhibition of intimal hyperplasia.

Acute angiographic and clinical outcome of high speed percutaneous rotational atherectomy (Rotablator)

Percutaneous rotational atherectomy (Rotablator), a high speed (greater than 100,000 RPM) rotational burr, was used successfully in 38 of 43 patients (88%) (mean age: 65 +/- 7 years) with 82 lesions (71 stenoses and 11 occlusions). The clinical indications were claudication (84%), nonhealing ulcer (7%), and renovascular hypertension (7%). Rotablation was successful in 78 of 82 lesions (95%): 68 of 71 (96%) stenoses (12 of 12 iliac, 11 of 11 femoral, 7 of 8 popliteal, 36 of 37 tibial, and 2 of 3 renal arteries; 60% of lesions were diffuse, i.e., greater than or equal to 4 cm in length), and 10 of 11 (91%) occlusions (5 of 6 femoral, 1 of 1 popliteal, 3 of 3 tibioperoneal, 1 of 1 brachial artery). The Rotablator significantly (p less than 0.001) reduced the arterial obstruction (stenoses: 85 +/- 11% to 12 +/- 12%); occlusions: 100% to 25 +/- 10%). The effective final burr size for arteries varied at 3.5-4.5 mm for renal, 3.0-3.5 mm for femoral, and 2.0-3.0 mm for brachial and tibial. Complications included gross hemoglobinuria without sequelae in 27 patients (63%), groin hematoma in 10 (23%), arterial spasm in 10 (23%), and arterial bypass in 2 (5%). The Rotablator was successfully used, without concomitant conventional balloon angioplasty, to open arterial lesions with excellent angiographic results in both diffuse and segmental peripheral vascular disease. There was gratifying patient clinical improvement.

Angiographic follow-up and clinical outcome of 126 patients after percutaneous directional atherectomy (Simpson AtheroCath) for occlusive peripheral vascular disease

Angiographic and clinical follow-up data were obtained in 115/126 patients who underwent directional atherectomy for peripheral vascular disease; of the 126, ten were excluded for appropriate reasons and one was lost to follow-up. Thus, 115/116 successful atherectomy patients (99%) had follow-up of 182/213 lesions (86%): 74 patients (64%) with angiography (mean time 5.4 mon), and 41 patients (36%) clinically. One hundred twenty-eight of 183 lesions (70%) had angiographic follow-up; the lesion recurrence as a stenosis or as an occlusion was 53%. Lesion distribution did not differ between angiography and clinical follow-up groups: nearly 85% were within the superficial femoral or popliteal arteries. Despite data stratification, angiographic follow-up indicated that patients after successful directional atherectomy, at a mean follow-up time of 5 mos, have more than a 50% lesion recurrence rate. Although directional atherectomy (Simpson AtheroCath) utilizing present techniques has excellent primary success and acceptable complication rates, angiographic follow-up statistics are bothersome.

Temperature along the surface of modified fiber tips for Nd:YAG laser angioplasty

For laser angioplasty probes, the thermal properties of the probes will primarily determine their mechanism of action. We examined the absorption, temperature increase, and probe degradation of transparent contact probes (hemispherical contact probe and ball-shaped fibers) and metal laser probes coupled to a continuous-wave Nd-YAG laser. Temperature was recorded by means of thermocouples and the measurements were corrected for direct light absorption by the thermocouple. During 15 W, 1 s exposure, the peak temperature rise of the hemispherical contact probe in contact with tissue dropped from approximately 1,000 degrees C at the front end to below 45 degrees C (95% drop) at the lateral side. In contrast, during continuous exposure the peak temperature rise of metal laser probes in contact with tissue dropped from 560 degrees C at the front end to near 400 degrees C (30% drop) at the 5.5 mm proximal rear end. During exposure in blood or tissue, the transparent contact probes became contaminated. Their absorption increased from 5 to 33% and the probe deteriorated. Repeated use of metal laser probes in blood resulted in a higher temperature at the rear than at the front end due to backburing of the fiber. Owing to the large temperature drop along the surface of transparent contact probes, the area of thermal destruction is limited to the tissue in front of the probe, whereas along the entire surface of metal laser probes the tissue will be affected. The large difference between these temperature distributions should be respected during clinical application of the transparent contact probe and the metal laser probe.

Design and evaluation of a fiberoptic fluorescence guided laser recanalization system

Current angioplasty techniques for recanalization of totally occluded arteries are limited by the inability to cross the occlusion and by the risk of perforation. A fiberoptic fluorescence guided laser recanalization system was developed and evaluated in vitro for recanalization of 17 human femoral or tibial totally occluded arterial segments (length 1.9-6.8 cm, diameter 2.5-6.0 mm). A 400 or 600 micron silica fiber was coupled to a helium-cadmium laser (lambda = 325 nm) for fluorescence excitation and to a holmium: YAG laser (lambda = 2.1 micron) for tissue ablation. Fluorescence was recorded during recanalization after every other holmium laser pulse. During recanalization, each arterial segment was bent 30-90 degrees with respect to the fiber to simulate arterial tortuosity. Ablation continued with fiber advancement as long as the fluorescence confirmed that the target tissue was atherosclerotic. Arterial spectra were classified as normal or atherosclerotic by an on-line computerized fluorescence classification algorithm (sensitivity 93%, specificity 95%). Normal fluorescence necessitated redirection of the fiber greater than 30 times per segment to continue recanalization. Fifteen of 17 totally occluded arteries had multiple recanalization channels created following total energy delivery of 40-1,016 Joules per segment with no angiographic or histologic evidence of laser perforation. Two heavily calcified arterial occlusions were not recanalized due to inhibition of holmium: YAG laser ablation by the recording of normal fluorescence spectra. Therefore, this fluorescence guided laser recanalization system appears safe and effective for recanalization of totally occluded arteries and merits in vivo evaluation. However, the lower sensitivity of fluorescence detection of heavily calcified plaques may limit the efficacy (but not safety) of fluorescence guided recanalization of heavily calcified occlusions.

Coronary atherectomy. An alternative to balloon angioplasty

To date, physicians at our hospital have performed coronary atherectomy on 15 patients. Of these patients, four needed open heart surgery. One patient needed surgery because a vessel was dissected during the procedure, and the three other patients had unsuccessful procedures. One patient died due to a cerebrovascular bleed related to the anticoagulation therapy required for the procedure. Of the remaining patients, three had no reocclusion and four had reocclusion at their six-month follow-up examinations. The remaining patients have not had a six-month follow-up examination. The restenosis rate at our institution is 25%. It is hoped that catheter-mediated atherectomy will be an effective, predictable transluminal treatment of single or multiple focal stenosis. Because of the small patient sampling and short duration follow-up, no trends have been established. A six-month follow-up with angiography will establish patency and restenosis rates.

Coronary directional atherectomy: rescue for failed balloon angioplasty and treatment of complicated lesions

Balloon angioplasty of the coronaries is still limited by the problems of acute complication and restenosis. Percutaneous directional atherectomy was conceived as a method to remove obstructive material from within the vessel. After encouraging results were obtained in peripheral vessels, coronary atherectomy has been selectively performed in 25 patients with lesions either not well suited for PTCA [n = 11], or as a bail-out after resistant [n = 2] or failed PTCA [n = 12]. Twenty-one LAD lesions [4 ostial, 13 proximal, 2 mid, and 2 bifurcation] and four right coronary artery [RCA] lesions with a mean length of 9 +/- 6 mm (19 eccentric, and 6 concentric) could be effectively reduced from 90% +/- 12% to 18% +/- 22%. Seventy-five percent of rescue cases could be spared emergency bypass operation. At 6 months, angiographic restenosis has been documented in 3 out of 11 patients studied to date (27%). Histologically, rescue procedures resulted in the removal of obstructing plaque material and only minimal thrombus. The occurrence of two perforations during rescue procedures, although clinically insignificant, emphasizes the need for judicious excision. In summary, directional atherectomy appears to be useful to treat lesions not well suited for PTCA, and important as a bail-out method after failed PTCA.

In vitro growth characteristics of human atherosclerotic plaque cells: comparison of cells from primary stenosing and restenosing lesions of peripheral and coronary arteries

Cell size distribution and growth rates were studied in vitro in human plaque cells from advanced primary stenosing and fresh restenosing lesions of peripheral and coronary arteries. Cells were isolated either by the explant technique or by enzymatic disaggregation and were identified as smooth muscle cells by their typical growth pattern and their positive reaction with antibodies against smooth muscle alpha-actin. Endothelial cells were found in plaque specimens from coronary arteries but were only present in primary cultures. Smooth muscle cells from primary stenosing tissue (ps-SMC) exhibited a significantly lower growth rate in culture (0.15 +/- 0.04 population doublings per day; means +/- SD) compared with cells from restenosing lesions (re-SMC; 0.60 +/- 0.13 population doublings per day; means +/- SD). ps-SMC usually became senescent in their second passage, i.e., after 5-7 cumultive population doublings. re-SMC retained their high proliferative activity even after five passages (15 cumulative population doublings). Cell populations of both origins consisted of two distinct subpopulations which could be discriminated by cell size measurements: relatively small, predominant cells (cell diameter: 18.0 +/- 4 microns; means +/- SD) and large fibroblast-like cells (cell diameter: 26.0 +/- 3 microns; means +/- SD). The proportion of large cells was higher in cell populations derived from primary stenosing tissue. These results suggest that stenosing plaque tissue from human peripheral and coronary arteries consists of two smooth muscle cell subpopulations. The low proliferative activity of total smooth muscle cell populations of advanced primary stenosing lesions contrasts with the high mitotic activity of smooth muscle cells obtained from secondary stenosing intimal proliferates.

Ex-vivo results using a new pullback atherectomy catheter (PAC)

In order to evaluate the feasibility of performing definitive atheromatous plaque removal using a novel retrograde cutting (Pullback) atherectomy catheter, pullback atherectomy was performed in 13 severely diseased cadaveric superficial femoral arteries. All experiments were performed using cadaver tissue either mounted in a perfusion/mounting chamber (n = 10) or left in situ (n = 3). In general, a single cut was made with each of three sequentially larger atherectomy catheters (2.5 mm, 3.0 mm, and then 3.5 mm devices). The results were evaluated by angiography and by light microscopy. Nine of the 13 experiments were performed in totally occluded vessels. The mean pre-atherectomy stenosis (all specimens) was 95 +/- 3%, with a final mean postatherectomy stenosis of 21 +/- 5%. There was one vessel performation. We conclude from these preclinical studies that retrograde atherectomy with the Pullback Atherectomy Catheter is a feasible means of performing definitive atherectomy. Despite the promising potential of retrograde atherectomy, little can be said with certainty about the clinical utility of such a device at this early stage.

Directional peripheral atherectomy: histopathologic aspects of a new interventional technique

Among the new transluminal vascular interventions currently being explored, directional atherectomy is unique in that it improves vessel patency by resecting intact portions of atherosclerotic plaque. Experimental atherectomy studies show that strips of plaque are cut away, leaving behind confluent defects within the stenotic lesions. Histologic examination of tissues excised during clinical peripheral atherectomy documents the heterogeneous morphology of peripheral atherosclerosis and shows that intimal hyperplasia is the most common cause of restenosis after therapeutic vascular interventions.

Peripheral atherectomy: experimental results with a new device

The size of present rotational atherectomy devices is limited in part by a tendency to produce vessel torsion. The authors designed and investigated a large-bore rotational atherectomy device for peripheral atherectomy in a single pass without significant torsion. A plaque was retrieved from 36 of 40 cadaveric iliac arteries. The mean plaque size was 8.4 x 3.9 mm, and the average number retrieved per artery was two. Thirty of 34 severely calcified arteries were treated successfully. Effluent study revealed no distal embolization; however, six perforations and four dissections occurred. Preliminary results suggest that a cutting surface with a relatively large diameter can be designed to be effective without producing vessel torsion. Changes in future designs will include added flexibility and expandable cutting surfaces to enhance safety and minimize entry diameter.

Current techniques for infrainguinal arterial reconstruction

Infrainguinal reconstruction for peripheral vascular occlusive disease comprises an increasingly complex array of interventions which provide unparalleled options for the salvage of threatened limbs. Conventional autogenous saphenous vein bypass remains the most durable revascularization with anticipated graft patency rates approaching 80 percent after five years and excellent long term limb salvage. These excellent results are equally applicable to vein grafts carried to infrapopliteal and even inframalleolar levels, possibly reflecting increased utilization of the in situ method. Although 20 per cent of grafts fail within five years, secondary intervention results in sustained limb salvage in the majority of patients. In the absence of autogenous vein, however, prosthetic material performs poorly such that new interventions consisting of percutaneous transluminal angioplasty, rotary atherectomy devices and laser systems are under aggressive development. Although initial results with these devices are encouraging, long term patency rates remain poor largely due to restenosis. Further progress seems to depend primarily on an increased understanding of the natural healing response of the injured artery.

Plaque morphology and pathologic changes in arteries from patients dying after coronary balloon angioplasty

Morphologic correlates of pathologic success or failure were studied at autopsy in 28 patients with 40 coronary arteries that had been subjected to balloon angioplasty. The presence of the following histologic features was evaluated: plaque concentricity or eccentricity, calcification, fibrous or fibropultaceous plaque, medial disruption, luminal thrombus and inflammation. Angioplasty was considered successful (residual cross-sectional luminal area greater than 25%) on pathologic examination in 14 arteries and unsuccessful in 26 arteries. Eccentric plaques were more likely to be successfully dilated than were concentric lesions (p less than 0.05). Six (50%) of 12 fibropultaceous plaques were successfully dilated compared with only 8 (29%) of 28 fibrous plaques. Moderate to severe calcification did not preclude morphologic success. Medial stretching or dissection, or both, was more often associated with a successful result. Thus, plaque morphology may be an important determinant of pathologic outcome after coronary angioplasty.

Percutaneous transcatheter myectomy of subvalvar pulmonary stenosis in tetralogy of Fallot: a new palliative technique with an atherectomy catheter

A male infant with tetralogy of Fallot was given a modified left Blalock-Taussig shunt at 11 days of age because of duct dependence. Twenty months later, because of increasing cyanosis and polycythaemia, he was given palliative treatment with balloon dilatation of the right ventricular outflow tract. Seven months later a right ventricular angiogram showed further progression of the infundibular stenosis with poor anterograde opacification of the pulmonary arteries. He underwent percutaneous transcatheter myectomy of the infundibulum with an atherectomy catheter. One month later he was well and less cyanosed.

Differential effect of Photofrin II on growth of human smooth muscle cells from nonatherosclerotic arteries and atheromatous plaques in vitro

The effect of dihematoporphyrin-ester or -ether (DHE), a photosensitizing porphyrin with different amounts of aggregates, on the growth of cultured smooth muscle cells obtained from nonatherosclerotic arteries and from atheromatous plaques (primary stenosing and restenosing lesions) was examined without photoactivation of the drug. Clinically relevant DHE concentrations ranging from 0.1 to 25 micrograms/ml were used. In all proliferation studies with cells of second and third passage (approximately 10 cumulative population doublings in vitro), the growth rates decreased in a dose-dependent manner. Smooth muscle cells from atherosclerotic lesions were significantly more sensitive than smooth muscle cells from normal arteries. Cells derived from restenosing lesions retained their increased sensitivity even after eight passages in culture (approximately 20 cumulative population doublings). Cell size measurements showed that the decreased proliferative activity mainly occurred in smooth muscle cell subpopulations consisting of small cells. A cytotoxic effect of DHE was observed at concentrations above 5 micrograms/ml, causing cytoplasmic protrusions, vacuoles, and even complete cell lysis. At a DHE concentration of 5 micrograms/ml, the number of viable cells was 73% +/- 14% (means +/- SD) for smooth muscle cells from nonatherosclerotic arterial media and only 38% +/- 11% (means +/- SD) for smooth muscle cells from atherosclerotic plaques. In all experiments, no significant difference in response to DHE treatment was observed between cells from primary stenosing and restenosing lesions, suggesting a specific mechanism for plaque-derived cells causing an increased sensitivity in comparison to smooth muscle cells from nonatherosclerotic arteries. The pronounced sensitivity of plaque cells against DHE treatment suggests that this drug--even without photoactivation--is potentially valuable in vivo as a therapeutic approach to vascular stenoses.

Comparison of dissection rates and angiographic results following directional coronary atherectomy and coronary angioplasty

Directional coronary atherectomy is a new percutaneous transluminal technique for treating occlusive coronary artery disease. In this study, angiographic results (i.e., residual stenosis and angiographic evidence of postprocedure dissection) after directional coronary atherectomy and balloon angioplasty were compared. The atherectomy group consisted of 91 lesions in 83 consecutive patients who underwent either left anterior descending artery or right coronary artery atherectomy. The angioplasty group consisted of 91 lesions in 84 patients that were matched with the atherectomy lesions with respect to vessel and whether the lesion was a restenosis lesion. The mean preprocedure diameter stenosis was 76% in both groups as measured quantitatively with electronic calipers. After the procedure, the mean residual diameter stenosis of the atherectomy lesions was 13 +/- 17%, whereas for the angioplasty lesions it was 31 +/- 18% (p less than 0.001). Success rates in both groups were similar (94.5 and 93.4%, respectively). The incidence of postprocedure dissection was 11% in the atherectomy group and 37% in the angioplasty group (p less than 0.0001). Directional coronary atherectomy results in significantly improved postprocedure angiographic appearances due to significantly less severe residual stenosis and lower incidence of dissection.

Coronary atherectomy. Clinical, angiographic, and histological findings and observations regarding potential mechanisms

Between August 5, 1988 and August 1, 1989, we attempted percutaneous directional coronary atherectomy of 76 lesions, including 42 primary lesions and 34 restenosis lesions that developed after one or more prior interventions. The procedure was successful in 67 lesions (88%), with a decrease in diameter stenosis from 80 +/- 11% to 5 +/- 15% after atherectomy (p less than 0.01). One or more complications occurred in six patients (9%), including non-Q wave myocardial infarction (three patients, 4.5%), femoral arterial injury requiring surgical repair (two patients, 3%), and proximal dissection leading to emergency bypass surgery (one patient, 1.5%). Despite these favorable acute results, the 6-month lesion restenosis rate was 30% by life-table analysis. Light microscopy of retrieved tissue revealed atherosclerotic plaque in 94%, media in 67%, and adventitia in 27%. Intimal proliferation was present in 97% of the restenosis lesions but was also evident in 33% of primary lesions. Tissue weight from 27 lesions averaged 18.5 mg (range, 5.8-45.1 mg), which is not adequate to explain the entire angiographic improvement. Thus, part of the improvement in lumen diameter appears to be due to mechanical dilatation rather than to tissue removal alone. Atherectomy can predictably treat selected coronary lesions with overall safety comparable to that of conventional balloon angioplasty, although the procedure as currently performed does not derive all of its benefit from tissue removal and does not appear to prevent restenosis.

Intravascular ultrasound as a guiding modality for mechanical atherectomy and laser ablation

One of the most compelling practical applications for intravascular ultrasound imaging is in enhancing the safety and efficacy of the second-generation catheter devices designed to ablate or remove plaque. Initial studies have shown that intravascular ultrasound is well suited to demonstrate the amount of atheroma present in a vessel, and the distribution within the vessel wall at any given point. Further clinical studies are required to determine whether more complete debulking of atheroma, guided by ultrasound imaging, has a favorable impact in reducing the rates of acute closure and restenosis following the procedure.

Transluminal atherectomy for occlusive peripheral vascular disease

The failure of balloon angioplasty to provide a durable result has led to the development of other methods of catheter-associated interventional therapy. In this study, 112 patients with superficial femoral artery stenosis or occlusion were treated with percutaneous atherectomy. Patients were considered to have a simple lesion if the occluded or stenotic arterial segment was less than 5 cm, and a complex lesion if the length of the occluded segment was greater than 5 cm. All atherectomies were performed in the superficial femoral and popliteal arteries; urokinase thrombolysis was used in conjunction with atherectomy in 16 patients. Atherectomy was considered successful if there was less than 20% residual stenosis determined by arteriography. Initial atherectomy results (30 day patency) were 100% successful in the group with a simple lesion and 93% successful in the group with a complex lesion. At a mean follow-up period of 12 months (range 5 to 24), there was a continued patency rate of 93% and 86%, respectively, in the simple and complex groups. In the patients who had restenosis, all pathologic specimens obtained during the second procedure demonstrated myointimal hyperplasia and organized thrombus. Eight major complications (7.1%) occurred, including one fatal myocardial infarction. The complication rate was 3.5% in the simple group and 8.3% in the complex group. With the exception of the myocardial infarction, all complications were associated with catheter entry site hematomas. Femoropopliteal atherectomy has a high rate of success and low morbidity and mortality for both simple and complex lesions and is a viable and competitive alternative therapy for patients with severe peripheral vascular disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Responses of cultured smooth muscle cells from human nonatherosclerotic arteries and primary stenosing lesions after photoradiation: implications for photodynamic therapy of vascular stenoses

Cultured smooth muscle cells from human nonatherosclerotic arteries and from primary stenosing lesions were labeled with dihematoporphyrinester and ether, a photosensitizing probe used mainly for the detection and photodynamic therapy of tumors. After labeling for 24 h, cells were irradiated with ultraviolet light (wavelength 365 nm, energy densities ranging from 30 to 1,200 mJ/cm2). Twenty-four hours after photoradiation, 80% of smooth muscle cells from nonatherosclerotic arteries and only 20% of smooth muscle cells from atherosclerotic plaques were viable and still adherent. Moreover, dynamic cell and cytoskeletal alterations in response to irradiation are described. The differential sensitivity of smooth muscle cells from nonatherosclerotic arteries and from atherosclerotic plaques provides evidence that a photodynamic treatment might be a valuable therapeutic approach to vascular stenosis.

Percutaneous arterial recanalization

The current status of new techniques for percutaneous arterial recanalization, including laser, thermal and mechanical angioplasty techniques, is described. The reported results, potential advantages and possible future developments are discussed.

Percutaneous peripheral atherectomy: angiographic and clinical follow-up of 60 patients

The Simpson atherectomy catheter was used to treat 60 patients with a total of 94 lesions comprising 63 stenoses (mean length 1.1 +/- 0.5 cm) and 31 occlusions (4.2 +/- 2.9 cm) of the superficial femoral (n = 77), popliteal (n = 8), iliac (n = 8) and anterior tibial (n = 1) arteries. The immediate angiographic success rate was 90% for both occlusions and stenoses, and clinical success was obtained in 82% of patients. The stenoses were reduced from 83 +/- 13% to 17 +/- 18% acutely and to 31 +/- 26% at 6 months; the occlusions were reduced from 100% to 9 +/- 9% initially and to 60 +/- 34% at 6 months. Angiographic restenosis was found in 24% of lesions: 23% in concentric and 11% in eccentric lesions and 47% in total occlusions. At 1 year, 72% of patients had clinically patent arteries with maintained Doppler index and walking distance. Three of four patients undergoing repeat atherectomy had a second restenosis. In summary, the procedure was found to be safe and effective in the treatment of peripheral vascular disease. It appears to be particularly beneficial in the treatment of eccentric stenoses and is not limited by the presence of calcification.

Experimental ultrasonic angioplasty: disruption of atherosclerotic plaques and thrombi in vitro and arterial recanalization in vivo

To investigate the use of high energy ultrasound as an alternative energy for angioplasty, an experimental ultrasonic angioplasty device was developed. The device was studied in two bioassay systems: an in vitro system for the disruption of atherosclerotic plaques and thrombi and an in vivo system for the recanalization of occluded canine femoral arteries. In vitro, sonication efficiently reduced the size of the plaques. Atheromatous plaques (n = 11) disrupted at a rate of 21 +/- 8 s/cm2; complicated plaques (n = 14) disrupted at a rate of 132 +/- 45 s/cm2 (p less than 0.001). Histologic examination revealed that the disruption of the plaques took place without concurrent damage to the media or adventitia. Ninety percent of the disrupted plaque debris had a diameter of less than 20 microns and was composed primarily of cholesterol monohydrate crystals. Solid thrombus (n = 5) weight was reduced from 1.6 +/- 0.2 to 0.4 +/- 0.1 g (p less than 0.0001) after 20 s of sonication. In vivo, sonication resulted in recanalization in all seven arteries tested in seven dogs. The obstruction was reduced from 93 +/- 11% to 18 +/- 7% (p less than 0.001). On histologic examination, the arterial wall injury index was found to be 1.56 +/- 0.42 in the test arteries compared with 1.37 +/- 0.47 in the control arteries (p = NS). The disruption of atherosclerotic plaques and thrombi, together with the efficient recanalization of the occluded arteries, demonstrates the potential of ultrasound angioplasty as a catheter-based technique for angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary peripheral arterial stenoses and restenoses excised by transluminal atherectomy: a histopathologic study

Atherectomy is a new therapeutic intervention for the treatment of peripheral arterial disease, and permits the controlled excision and retrieval of portions of stenosing lesions. The gross and light microscopic features of 218 peripheral arterial stenoses resected from 100 patients by atherectomy were studied. One hundred seventy of these lesions were primary stenoses and 48 were restenoses subsequent to prior angioplasty or atherectomy. Microscopically, primary stenoses were composed of atherosclerotic plaque (150 lesions), fibrous intimal thickening (15 lesions) or thrombus alone (5 lesions). Atherosclerotic plaques had a variable morphology and, in one-third of cases, were accompanied by abundant surface thrombus that probably added to the severity of stenosis. Most patients with fibrous intimal thickening or thrombus alone had typical atherosclerotic plaque removed elsewhere from within the same artery. Intimal hyperplasia, with or without underlying residual plaque, was found at 36 sites of restenosis, the remaining 12 consisting of plaque only. Intimal hyperplasia had a distinctive histologic appearance and was due to smooth muscle cell proliferation within a loosely fibrous stroma. Superimposed thrombus may have contributed to arterial narrowing in 25% of hyperplastic and 8% of atherosclerotic restenoses (p = 0.41). Pathologic examination of tissues recovered by peripheral atherectomy is an important adjunct that may provide insight into the efficacy of vascular interventions and the phenomenon of postintervention restenosis.

Percutaneous transluminal atherectomy: preliminary results

Percutaneous transluminal atherectomy with the Simpson atherectomy catheter was performed in 10 patients with 14 severe atheromatous stenoses of the femoropopliteal arteries. Removal of plaque material with restoration of vessel patency was successful in all patients without complication. Further clinical follow-up will have to determine whether the recurrence rate of stenoses will be lower with this method than with conventional balloon angioplasty.

Growth characteristics and cytoskeletal organization of cultured smooth muscle cells from human primary stenosing and restenosing lesions

Growth characteristics of human plaque cells selectively extracted from advanced primary stenosing and fresh restenosing lesions by percutaneous transluminal atherectomy were studied in vitro. Cells were isolated either by explant technique or by enzymatic disaggregation, and they were identified as smooth muscle cells (SMC) by positive reaction with antibodies against alpha-smooth muscle actin. Endothelial cells were not found in the atherectomized tissue. The cells of primary stenosing tissue (ps-SMC) exhibited a significantly low growth rate (0.16 +/- 0.04 population doublings per day) in comparison to the cells of restenosing lesions (re-SMC, 0.64 +/- 0.15 population doublings per day). Furthermore, ps-SMC became senescent and remained quiescent after two passages, whereas re-SMC retained a high proliferative activity and became quiescent by passage 8 to 10. Both types of cells responded to increasing serum concentrations in a dose-dependent manner. Ps-SMC failed to respond to purified platelet-derived growth factor (PDGF) and a mitogen mixture isolated from bovine brain (ECGF), but their proliferative activity was increased by the addition of re-SMC-conditioned culture medium. Despite their high basic growth rate, the proliferative activity of re-SMC was significantly stimulated by PDGF and ECGF in a dose-dependent manner. PS-SMC and re-SMC populations consisted of two distinct subpopulations, which could be discriminated by cell size measurements and cell adhesion: 1) relatively small (cell diameter, 18.6 +/- 5 microns), low-adhesive, predominant cells, and 2) enlarged (cell diameter, 27.1 +/- 3 microns), high-adhesive, fibroblast-like cells with abundant microfilaments. Neither ps-SMC or re-SMC stained with antibodies against desmin, but did express vimentin. The organization patterns of vimentin and tubulin were unaltered in comparison to each other and to smooth muscle cells cultured from the media of nonatherosclerotic human arteries.

A randomized trial of corticosteroids for the prevention of restenosis in 102 patients undergoing repeat coronary angioplasty

To examine the effect of corticosteroid therapy on the development of restenosis following successful percutaneous transluminal coronary angioplasty (PTCA), we randomized 102 patients with restenosis following prior PTCA to receive high-dose steroids (n = 52) or no steroids (n = 50). The steroid regimen consisted of 125 mg methylprednisolone I.M. the night before and morning of the PTCA, and prednisone 60 mg p.o. Q.D. for 1 week. post-PTCA. Angiographic follow-up at 6 months was available in 27 steroid-treated patients (52%) and 27 controls (54%). The per lesion incidence of restenosis was similar in the two groups (36% vs. 40%, respectively, P = NS). Clinical follow-up was available in the remaining patients at a mean interval of 1.2 years. The clinical correlates of restenosis (incidence and severity of angina, positive treadmill exercise test, nonfatal infarction or death) were similar in the steroid treated and control groups (24% vs. 39%, respectively, P = .56). At late follow-up, 30 steroid-treated patients (58%) and 26 control patients (52%) had no clinical or angiographic evidence of restenosis (P = NS). In conclusion, a short course of high-dose corticosteroid therapy does not significantly reduce the frequency of restenosis following PTCA.

Cell constitution and characteristics of human atherosclerotic plaques selectively removed by percutaneous atherectomy

The Simpson atherectomy device used for the recanalization of severely stenosed peripheral arteries is able to collect plaque material which can be further characterized. This study reports histological, immunohistochemical and transmission electron microscopic findings on advanced human primary atherosclerotic plaques of peripheral arteries percutaneously removed by a Simpson atherectomy catheter. Material from stenosing plaques consisted of dense connective tissue with abundant amounts of concentrically arranged elastic fibers and lamellae. This meshwork contained numerous cells, often arranged in clusters and oriented with their longer axis parallel to the direction of blood flow. The vast majority of these cells could be easily identified as vimentin-positive and desmin-negative smooth muscle cells containing lipid deposits in the perinuclear region and numerous glycogen particles. Monocytes/macrophages were observed only very infrequently. Plaque tissue contained a range of smooth muscle cell phenotypes. Most of the cells were of an intermediate phenotype, i.e. sparsely filled with myofilament bundles at the cell periphery and a high amount of organelles such as mitochondria, rough endoplasmic reticulum and Golgi cisterns. An intact lining of pieces of intimal tissue with endothelial cells was not observed. Two-dimensional gel electrophoresis of plaque tissue showed the presence of alpha-, beta- and gamma-actin isoforms with a clear predominance of the beta-isoform.

Percutaneous atherectomy of occlusive peripheral vascular disease: stenoses and/or occlusions

Percutaneous atherectomy was performed using the Simpson Atherocath on 131 patients (87 male, 66%) with a mean age of 65 years. Clinical characteristics included evidence of significant coronary disease in 50%, hypertension in 46%, diabetes in 41%, and prior neurologic deficit in 32% of patients. The indication for atherectomy was claudication in 114 (87%) and rest pain, gangrene, or ulcer in 17 patients (13%). Atherectomy was successfully performed in 136/139 stenoses (98%) and in 56/56 occluded vessels with or without prior balloon angioplasty. No serious complications resulting in limb loss or emergency vascular surgery were encountered. Histopathology of retrieved specimens showed that 66% had atheromatous plaque, 45% had tunica media, and 30% had a form of thrombus. Material obtained from an occluded vessel was more likely to have thrombus and tunica media present than that from a stenosis (P less than 0.02 and P less than 0.05, respectively). Early angiographic follow-up (mean time, 17 weeks) showed a relatively low (17%) lesion recurrence rate. Percutaneous atherectomy can be successfully utilized in stenotic and occluded peripheral arteries with good success and no serious complications; stenoses appear to have a low recurrence rate.

Catheter atherectomy: functional results in peripheral arterial disease

In 10 patients with peripheral arterial disease (PAD) atherectomy was performed with the Simpson atherectomy catheter. PAD was diagnosed by clinical evaluation, oxzillography, Doppler ultrasound examination, treadmill walking, and angiography. Eight patients belonged to stage II and 2 to stage IV. Two stenoses were located in the iliac artery, and the others in the superficial femoral artery or popliteal artery or both. The treadmill walking distance before the intervention ranged from 24 to 67 m before and 105 to 115 m after the procedure (speed 2 mph; gradient 12.5%). After atherectomy, the walking distance improved by 35% to 126%. No patient in stage II perceived pain. In these patients treadmill exercise was terminated because of dyspnea. The ankle/arm ratio (Doppler ultrasound) ranged from 0.4 to 1.0 before atherectomy with a mean improvement of 0.15 afterward (stages II and IV). Control angiography within three to six months in 4 patients did not reveal any significant change at the site of the original stenosis.

Two-dimensional intravascular ultrasound: technical development and initial clinical experience

This article reviews the development and current status of catheter-based, intravascular ultrasound imaging. The first section provides an introduction to some of the general technical issues encountered in the design of the catheter imaging systems and compares the potential merits of the multiple-element versus the mechanical approach. The second section of the article reviews the data from early studies correlating the intravascular ultrasound images with histologic sections (in vitro) and angiography (in vivo). The article concludes with a discussion of potential clinical applications and future technical developments.

Laser ablation and the need for intra-arterial imaging

In 48 patients with severe claudication due to a total obstruction of the femoropopliteal artery, percutaneous recanalization was attempted with a 2.2 mm diameter rounded sapphire contact probe in conjunction with a continuous wave Nd:YAG laser. In eight patients the contact probe laser catheter took a subintimal course that could not be redressed. Laser recanalization needs high-resolution diagnostic information on the complex anatomy of the obstruction. Intra-arterial ultrasound imaging may provide the necessary information to evaluate, monitor or guide novel angioplasty techniques. The design of an ultrasound catheter which combines high-resolution diagnostic imaging with steerability, flexibility and controlled ablation is now the major engineering challenge in interventional cardiology.

Clinical applications of intravascular ultrasound imaging in atherectomy

This paper discusses the potential application of intravascular ultrasound imaging in the context of catheter-based atherectomy. The advantages and limitations of ultrasound in this application are discussed, and representative cases are presented.

"Crackers, breakers, stretchers, drillers, scrapers, shavers, burners, welders and melters"--the future treatment of atherosclerotic coronary artery disease? A clinical-morphologic assessment

Although various public health preventive efforts and prescribed pharmacologic treatment methods will have long-term benefits in the reduction of coronary artery atherosclerosis and subsequent cardiac events, the immediate and short-term future in the treatment of coronary artery disease will focus on several interventional devices designed to remodel or remove causes of acute and chronic coronary artery obstruction. Certain clinical-morphologic aspects of these interventional devices or techniques that result in remodeling of the coronary lumen shape (balloon angioplasty, thermal probes, intravascular stents) or removal of obstructing material (lasers, atherectomy devices) are reviewed. Two new areas in the pathology of atherosclerotic plaque (plaque fissures, eccentric plaque) and their clinical relevance in coronary heart disease are described.

Percutaneous atherectomy--early experience in Sheffield

Percutaneous transluminal angioplasty (PTA) of arterial stenoses is a well-established and relatively safe technique in the treatment of peripheral and coronary vascular disease. Recurrence, however, remains a problem. The 'atherectomy' catheter is a new device to provide lumen enlargement by the mechanical removal of atheroma. In Sheffield, 14 lesions in the femoral arteries have been treated by atherectomy, with a reduction in mean diameter stenosis from 88% to 15%. There were no complications. Follow-up ranges from 3 to 15 months, with a mean of 9 months. There has been only one recurrence. It can be used in calcified lesions and may prove to be most useful in the treatment of tough lesions. Further experience and follow-up is necessary, however, to determine whether it has any advantage over balloon dilatation.