Atheroablation with the Kensey catheter: a pathologic study

Observing the carotid debris aspirated during carotid stenting: technical note

OBJECTIVES

Elective carotid stent implantation using a distal protection is increasing. In this article we describe an observation method for carotid plaque debris collection during carotid stenting.

METHODS

Endovascular stenting for the right internal carotid artery (ICA) stenosis was performed under distal balloon protection. During balloon protection, 30 ml of blood containing debris was aspirated followed by vigorous saline irrigation flushing any residual debris out into the ipsilateral external carotid circulation. Post-operatively, the aspirated blood was filtered and the debris remained on the membrane. The membrane was stained with hematoxylin-eosin (HE) solution and then mounted onto a glass slide for visualization.

RESULTS

Microscopic observation of the slide revealed several debris such as atheromatous plaques and intimal strips. HE staining facilitates the characterization of the debris composition. In addition to the histological evaluation, this technique revealed the particle size as well as the quantity of debris. The resulting HE slide is also suitable for permanent storage. In addition to the qualitative and quantitative qualities, this simple technique requires neither specific instrumentation nor equipment.

DISCUSSION

Carotid plaque debris aspirated during carotid artery stenting under distal protection can be filtered and visualized on a permanent glass slide. This simple method allows us to better understand quantity, particle size, and composition of debris.

Stent placement versus percutaneous transluminal angioplasty of human carotid arteries in cadavers in situ: distal embolization and findings at intravascular US, MR imaging and histopathologic analysis

PURPOSE

To compare endovascular stent placement with percutaneous transluminal angioplasty (PTA) of carotid arteries with respect to distal embolization and findings at intravascular ultrasonography (US), magnetic resonance (MR) imaging, and histopathologic analysis.

MATERIALS AND METHODS

PTA was performed in situ in one carotid artery, and stent placement was performed in the other, in ten cadavers (age range, 57-82 years; mean age, 68 years) with severe atherosclerosis by using fluoroscopic and intravascular US guidance. The carotid artery was connected to a pressurized tubing system in which a pulsatile pump circulated water. The effluent water was collected during the interventions, and after filtration and staining, the embolic material was analyzed histologically. After the interventions, the arteries were excised and 1.5-T spin-echo MR imaging was performed.

RESULTS

No difference in severity of distal embolization during stent placement versus during PTA was found. The embolic particles were composed mainly of intimal strips and cellular constituents of the atherosclerotic plaques. MR imaging accurately depicted postinterventional changes, and the findings correlated closely with those of intravascular US and histopathologic analysis.

CONCLUSION

Although stent placement and PTA were associated with equal distal embolization, the smooth surface and fully patent arterial lumen depicted at intravascular US and MR imaging postinterventionally may indicate that stent placement is preferable to PTA.

Injury potential to venous valves from the Amplatz thrombectomy device

PURPOSE

To evaluate the acute effects of the Amplatz thrombectomy device (ATD) on peripheral venous valves in a canine model.

MATERIALS AND METHODS

ATD thrombectomy was performed in 17 veins, and control experiments with use of an 8-F sheath-dilator were performed in four veins. Prethrombectomy ascending venography was performed, followed by device passage across the vein segment. Post-thrombectomy ascending venography was then performed, followed by heparinization and euthanasia. The treated veins were carefully explanted and stored in formaldehyde for histopathologic examination. Severity of valve injury was graded on a scale of 0 to 4.

RESULTS

In ATD-treated veins: 10 veins sustained no injury [grade 0] (diameter, 6.7 mm +/- 1.7; antegrade/retrograde approach, 5/5), five veins sustained mild injury [grade 1-2] (diameter, 5.2 mm +/- 0.8; antegrade/retrograde, 3/2), while the remaining two veins sustained moderate-to-severe injury [grade 3-4] (diameter, 5 and 6 mm; antegrade/retrograde, 1/1). In sheath-dilator treated veins: no injury [grade 0] in any of the four treated veins (mean diameter, 5.5 mm +/- 0.6; all retrograde). In ATD-treated veins, valve injury (of any grade) was significantly more frequent in veins 6 mm or less in diameter than in veins at least 7 mm in diameter (seven of 12 vs zero of five; P < .03). There was no significant association between thrombectomy approach and injury grade.

CONCLUSION

Veins 7 mm or greater in diameter were associated with no significant valve injury during ATD thrombectomy. However, long-term and short-term effects on valvular function will need to be assessed.

Rheolytic thrombectomy with use of the AngioJet-F105 catheter: preclinical evaluation of safety

PURPOSE

A preclinical evaluation of the safety of the AngioJet-F105 rheolytic thrombectomy catheter.

MATERIALS AND METHODS

The AngioJet-F105 catheter uses multiple retrograde high-speed fluid jets impinging on a primary aspiration lumen to create a hydrodynamic recirculation vortex that traps and fragments adjacent thrombus, with simultaneous evacuation of the resulting debris through the aspiration lumen. The effect of the AngioJet on treated vessels was evaluated in 10 canines. Vascular integrity on histopathologic examination and endothelial coverage on scanning electron microscopic study were examined in 15 vessel segments treated with the AngioJet-F105 catheter, compared with four vessel segments subjected to the Fogarty balloon maneuver, and 10 untreated vessel segments. The size distribution of particulate debris, upstream and downstream, after thrombectomy was determined in a flow-circuit model simulating the superficial femoral artery. Aliquots from the downstream effluent were then injected into the renal arteries of two healthy canines.

RESULTS

The device caused only minimal focal endothelial denudation and no significant deep injury. No significant difference in endothelial coverage occurred in AngioJet-treated vessel segments compared to untreated control vessels (mean +/- standard deviation: 88.0% +/- 7.9% vs 89.7% +/- 11.6%, P = .77). Vessels treated with the Fogarty balloon pullback maneuver had significantly less residual endothelial coverage (58.0% +/- 8.0%, P < .03). Particulate microemboli in the effluent of the flow model accounted for 12% of the initial thrombus volume (0% > 100 microm, 99.83% < or = 10 microm). Histopathologic evaluation of the four renal beds injected with the resulting debris demonstrated no signs of necrosis. A moderate transient increase in plasma-free hemoglobin occurred, with a mild corresponding decrease in hematocrit.

CONCLUSIONS

The AngioJet-F105 catheter resulted in only mild and focal injury to the treated vessels. The vast majority of resulting particulate debris consist of microscopic particles, without significant ischemic effect.

Improved mechanical thrombolysis with the addition of recombinant tissue-type plasminogen activator: in vitro study with use of Cr-51-labeled clots

PURPOSE

To explore the potential effect of infusion of recombinant tissue-type plasminogen activator (rt-PA) during mechanical thrombolysis.

MATERIALS AND METHODS

Clots containing chromium-51-labeled platelets produced from blood from two donors were placed in a solution of rt-PA (1.25 micrograms/mL) or in saline solution and were pulverized with a mechanical thrombolysis catheter. The resultant slurry was passed through a filter with a pore size of 10 microns, and the radioactivity of the clot residue on the filter was measured. For each donor, the percentage of clot remaining was calculated from the residual radioactivity.

RESULTS

The mean percentages of clot remaining were 72.0% for clots in saline (n = 10) and 44.4% for clots in rt-PA (n = 10) in donor 1 and 58.9% (n = 14) and 36.4% (n = 14), respectively, for donor 2. In both cases, the mean percentage of clot remaining was significantly lower when mechanical thrombolysis was performed in the presence of rt-PA.

CONCLUSION

These results indicate the feasibility of combined pharmacologic and mechanical thrombolysis.

Recirculation-type Amplatz clot macerator: determination of particle size and distribution

PURPOSE

A high-speed mechanical clot macerator was tested in vitro, and the distributions and sizes of residual particles produced by this device were determined.

MATERIALS AND METHODS

Human thrombi aged for 4 days and 10 days were macerated using a recirculation-type Amplatz thrombectomy device with an 8-F, high-speed screw propeller. The device was activated for 15, 30, and 60 seconds. Two different methods of particle measurement were used to determine overall particle distribution and to determine the size and number of large particles.

RESULTS

The recirculation device liquefied 99.2% of 4-day-old and 98.8% of 10-day-old thrombi, producing particles ranging in size from 13 to 1,000 microns; all particles were smaller than 1,000 microns. Particle size and distribution results were identical for the 30-second and 60-second activation times.

CONCLUSION

The recirculation-type thrombectomy device appears to perform well as a method of macerating human thrombi. Clinical trials need to be conducted to test the device further and to determine if it can be used safely on venous as well as arterial occlusions.

Distribution and size of particles after dynamic angioplasty in cadaveric arteries with the Kensey catheter system: a comparison with clinical experience

The distribution and size of atheromatous debris after angioplasty with the Kensey catheter was determined after recanalization of 18 segments of human cadaveric superficial femoral arteries (SFA). The debris produced was studied cytologically and measured semiquantitatively. Nearly 80% of all particles ranged from 5 to 15 microns, approximately the size of red blood cells. More than 20% of all particles exceeded this size and 2% were larger than 100 microns. The use of the Kensey catheter dynamic angioplasty system in the lower extremities contains the risk of embolic complications because more than 20% of all particles are larger than human blood cells. Seven patients with occlusion and 3 with stenoses of the SFA were treated with the Kensey catheter system. Recanalization was successful in all and in 1 case, small emboli in the anterior tibial artery were observed. There was a 50% restenosis/reocclusion rate between 2 weeks and 10 months.

Effects of laser-generated tissue debris on aggregation of human platelets

This study examined the effects of laser-generated tissue debris from thrombus, atheroma, and normal aorta on platelet aggregation. Debris supernatant and suspension from lased thrombus induced dose-related aggregation, maximal at 48 +/- 12% and 65 +/- 2%, respectively. Debris suspension from normal aorta induced maximal aggregation of 35 +/- 12%, but the debris from atheromatous aorta surprisingly had no effect on platelet aggregation. The debris particle count was in the range of 10(10) to 10(12) per liter. Aspirin, 0.2 and 2.0 mmol/L, only weakly inhibited the debris-induced aggregation, and heparin up to 10 U/ml was ineffective. However, iloprost reduced aggregation to 40 +/- 11% of control at 0.3 ng/ml, and totally abolished it at 3 ng/ml. Soluble and particulate laser-generated debris from vascular tissue and thrombus may cause platelet aggregation in vitro. This may have implications for laser coronary angioplasty.

Engineering investigation of the Kensey dynamic angioplasty catheter

This article describes an in vitro experimental study which was designed to gain a better understanding of the mechanism by which the Kensey catheter mediates atherosclerotic tissue. The major goals of the study were to observe the generation of debris particles during revascularization and to elucidate the fluid dynamic effects associated with particle motions at and around the tip of the catheter. To investigate these phenomena, in vitro actual size and large scale model experiments were conducted. The results of these experiments provide a reference for the significance of the clinical performance of the Kensey catheter.

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.

In vivo ultrasound arterial recanalization of atherosclerotic total occlusions

The purpose of this study was to assess the potential of intraarterial ultrasound for in vivo recanalization of atherosclerotic total occlusions. Ultrasound energy at a frequency of 20 kHz was applied with a prototype solid wire probe to 12 surgically implanted occluded human atherosclerotic arterial xenografts, 9 of which were calcified, as well as to the intimal surface of 12 normal canine arteries. In both the normal canine arteries and the atherosclerotic occluded xenografts, there was no angiographic evidence of vasospasm, thrombosis or arterial dissection. Eleven of the 12 atherosclerotic complete arterial occlusions were resistant to passage of a conventional guide wire or probe without ultrasound energy. However, the occlusions were recanalized after administration of 15 s to 4 min (mean 1.5 +/- 1.3 min) of intermittent ultrasound energy. After ultrasound, 8 of the 12 vessels underwent balloon angioplasty. Angiographic residual stenosis after ultrasound alone was 62 +/- 24% and after combined ultrasound and balloon angioplasty, 29 +/- 13%. Although routine angiography did not reveal arterial emboli, high resolution cut films did demonstrate a few distal nonocclusive thrombi of a size similar to that reported with other recanalization methods. Histologic studies demonstrated changes similar to those after balloon angioplasty, with focal cracking of the fibrotic and calcified plaque. The findings demonstrate that ultrasound energy applied through a catheter delivery system can be used in vivo to open completely obstructed atherosclerotic vessels. These studies suggest that it might be clinically feasible to use the ultrasound probe to create a lumen, allowing subsequent balloon dilation.

Percutaneous ultrasonic angioplasty:initial clinical experience

Percutaneous catheter-delivered ultrasound energy for arterial recanalisation was applied in eight patients with peripheral vascular disease. Four patients had severe claudication with total occlusion and four high-grade stenosis in a superficial femoral or popliteal artery. A prototype ultrasound probe, with a frequency of 20 kHz and a power output of 20-35 W/cm2, was ensheathed in a 7F catheter and advanced to the occlusions under angiographic guidance. Three of four complete occlusions were recanalised in 120s or less, leaving a residual stenosis of mean (SD) diameter 54 (5)%. Ultrasound energy reduced the diameter of the isolated stenoses from 77 (14)% to 37 (21)%. All lesions were further treated with balloon angioplasty, resulting in a mean residual stenosis of 20 (9)%. There was no evidence of arterial emboli, dissection, spasm, or perforation. The major limitations of this ultrasound system are ease of steering and flexibility. Percutaneous catheter-delivered ultrasound energy appears promising for safe and effective use in atherosclerotic peripheral vessels to reduce arterial stenoses and recanalise complete arterial obstructions.