Laser-facilitated thrombectomy: a new therapeutic option for treatment of thrombus-laden coronary lesions

Submillimeter Multifunctional Ferromagnetic Fiber Robots for Navigation, Sensing, and Modulation

Small-scale robots capable of remote active steering and navigation offer great potential for biomedical applications. However, the current design and manufacturing procedure impede their miniaturization and integration of various diagnostic and therapeutic functionalities. Herein, submillimeter fiber robots that can integrate navigation, sensing, and modulation functions are presented. These fiber robots are fabricated through a scalable thermal drawing process at a speed of 4 meters per minute, which enables the integration of ferromagnetic, electrical, optical, and microfluidic composite with an overall diameter of as small as 250 µm and a length of as long as 150 m. The fiber tip deflection angle can reach up to 54o under a uniform magnetic field of 45 mT. These fiber robots can navigate through complex and constrained environments, such as artificial vessels and brain phantoms. Moreover, Langendorff mouse hearts model, glioblastoma micro platforms, and in vivo mouse models are utilized to demonstrate the capabilities of sensing electrophysiology signals and performing a localized treatment. Additionally, it is demonstrated that the fiber robots can serve as endoscopes with embedded waveguides. These fiber robots provide a versatile platform for targeted multimodal detection and treatment at hard-to-reach locations in a minimally invasive and remotely controllable manner.

Relationship Between Attenuated Plaque Identified by Intravascular Ultrasound and Thrombus Formation After Excimer Laser Coronary Angioplasty

BACKGROUND

Excimer laser coronary angioplasty (ELCA) has been reported to be a safe and effective atherectomy device in percutaneous coronary intervention (PCI). However, thrombotic complications after ELCA have been occasionally observed. In this study, we evaluated the impact of attenuated plaque on thrombus formation and transient no-reflow after ELCA.

METHODS

This study enrolled 58 lesions in 56 patients who underwent PCI with ELCA. It was a retrospective observational study at a single center. All lesions were imaged by intravascular ultrasound (IVUS) before and immediately after ELCA. On the plaque with ultrasound attenuation, attenuation angle per millimeter and attenuation length were measured. ELCA-induced thrombus was detected by IVUS, and transient no-reflow after ELCA was recorded.

RESULTS

Thrombus was detected in 14 lesions (30 %), and transient no-reflow occurred in 3 lesions (5 %). Lesions with thrombus had a higher mean attenuation angle (median [interquartile range] 142° [112°-152°] vs. 64° [0°-115°]; p = 0.001), maximum attenuation angle (209° [174°-262°] vs. 86° [0°-173°]; p < 0.001), and longer attenuation length (12 mm [8 mm-17 mm] vs. 2 mm [0 mm-5 mm]; p < 0.001). Lesions with thrombus leading to transient no-reflow had a longer lipid length and a significantly higher troponin I level after PCI.

CONCLUSIONS

IVUS-identified attenuated plaque was strongly correlated with ELCA-induced thrombus. Furthermore, attenuation length may predict transient no-reflow.

Histological evaluation of vascular changes after excimer laser angioplasty for neointimal formation after bare-metal stent implantation in rabbit iliac arteries

BACKGROUND

Excimer laser is used to treat coronary artery disease, especially in case of lesions with thrombus and in-stent restenosis (ISR). However, there are no in vivo preclinical studies that have evaluated the pathological reactions of the vessel wall after excimer laser ablation.

METHODS

Bare-metal stents were placed in the external iliac arteries of six healthy rabbits. Twenty-eight days later, excimer laser ablation was performed with low-power (45 (fluency)/25 (rate)) in one side, and high-power (60/40) in the opposite side, followed by optical coherence tomography (OCT) evaluation. Rabbits were sacrificed 15 min after the procedure, and histological assessment was performed.

RESULTS

Morphometry analysis of OCT showed similar stent and lumen size between low-power and high-power group. Histological evaluation suggested endothelial cell loss, fibrin deposition, and tissue loss. The low-power group showed significantly less pathological changes compared with the high-power group: angle of endothelial cell loss, 32.4° vs. 191.7° (interquartile range, 8.8°-131.7° vs. 125.7°-279.5°; p < 0.01); fibrin deposition, 1.1° vs. 59.6° (0.0°-70.4° vs. 31.4°-178.4°; p = 0.03); and tissue loss 0.0° vs. 18.2° (0.0°-8.7° vs. 0.0°-42.7°; p = 0.03).

CONCLUSIONS

The pathological changes in neointima were more prominent after high-power excimer laser ablation than after low-power excimer laser. To improve safety in clinical practice, understanding the pathological changes of tissues after excimer laser in lesions with ISR is essential.

Contemporary percutaneous management of coronary calcification: current status and future directions

Severe coronary artery calcification is one of the greatest challenges in attaining success in percutaneous coronary intervention, limiting acute and long-term results. In many cases, plaque preparation is a critical prerequisite for delivery of devices across calcific stenoses and also to achieve adequate luminal dimensions. Recent advances in intracoronary imaging and adjunctive technologies now allow the operator to select the most appropriate strategy in each individual case. In this review, we will revisit the distinct advantages of a complete assessment of coronary artery calcification with imaging and application of appropriate and contemporary plaque modification technologies in achieving durable results in this complex lesion subset.

Multifunctional ferromagnetic fiber robots for navigation, sensing, and treatment in minimally invasive surgery

Small-scale robots capable of remote active steering and navigation offer great potential for biomedical applications. However, the current design and manufacturing procedure impede their miniaturization and integration of various diagnostic and therapeutic functionalities. Here, we present a robotic fiber platform for integrating navigation, sensing, and therapeutic functions at a submillimeter scale. These fiber robots consist of ferromagnetic, electrical, optical, and microfluidic components, fabricated with a thermal drawing process. Under magnetic actuation, they can navigate through complex and constrained environments, such as artificial vessels and brain phantoms. Moreover, we utilize Langendorff mouse hearts model, glioblastoma microplatforms, and in vivo mouse models to demonstrate the capabilities of sensing electrophysiology signals and performing localized treatment. Additionally, we demonstrate that the fiber robots can serve as endoscopes with embedded waveguides. These fiber robots provide a versatile platform for targeted multimodal detection and treatment at hard-to-reach locations in a minimally invasive and remotely controllable manner.

Excimer laser technology in percutaneous coronary interventions: Cardiovascular laser society's position paper

Excimer Laser Coronary Atherectomy (ELCA) is a well-established therapy that emerged for the treatment of peripheral vascular atherosclerosis in the late 1980s, at a time when catheters and materials were rudimentary and associated with the most serious complications. Refinements in catheter technology and the introduction of improved laser techniques have led to their effective use for the treatment of a wide spectrum of complex coronary lesions, such as thrombotic lesions, severe calcific lesions, non-crossable or non-expandable lesions, chronic occlusions, and stent under-expansion. The gradual introduction of high-energy strategies combined with the contrast infusion technique has enabled us to treat an increasing number of complex cases with a low rate of periprocedural complications. Currently, the use of the ELCA has also been demonstrated to be effective in acute coronary syndrome (ACS), especially in the context of large thrombotic lesions.

Contemporary technologies to modify calcified plaque in coronary artery disease

With aging society, one of the more challenging obstacles in percutaneous coronary interventions are calcified coronary lesions. Calcified lesions may impede stent delivery, limit balloon and stent expansion, cause uneven drug distribution, and hinder wire advancement. Even in the setting of acceptable procedural success, vessel calcification is independently associated with increased target lesion revascularization rates at follow-up and lower survival rates. In order to effectively manage such lesions, dedicated technologies have been developed. Atherectomy aims at excising tissue and debulking plaques, as well as compressing and reshaping the atheroma, generally referred to as lesion preparation that enables further balloon and/or stent expansion in contemporary clinical practice. In the current review, we will discuss the available methods for atherectomy, including rotational, orbital, and excimer laser coronary atherectomy, as well as intravascular lithotripsy. In addition, we will review the role of imaging in calcified lesions.

Excimer Laser Atherectomy in Percutaneous Coronary Intervention: A Contemporary Review

Excimer laser coronary atherectomy (ELCA) during percutaneous coronary intervention (PCI) has been in use for more than twenty years. While early experiences were not favorable over balloon angioplasty alone, with improvement in operator technique, patient selection and technology, ELCA has established its own niche in contemporary PCI as a safe and effective atherectomy strategy. With growing experience in complex coronary interventions worldwide, ELCA has become one of the essential atherectomy tools offering unique advantages over other atherectomy devices. In the modern era, ELCA is commonly used for patients with in-stent restenosis, stent under expansion, balloon uncrossable lesions and chronic total occlusions. Technical success rates are reported to be >80% in most situations while procedural complication rates such as vessel dissection and perforation among others are reported to average 9% over the past 25 years with improvement over time. In this review, we provide a comprehensive systematic review of the ELCA system, its practical use, indications, and procedural techniques in the contemporary PCI era.

Excimer laser in contrast for the treatment of acute MI caused by thrombosis of underexpanded stent

The use of excimer laser with contrast for treating an underexpanded stent in the setting of subacute stent thrombosis and hemodynamic instability is described. The patients presented with acute coronary syndromes and cardiogenic shock resulting from stent thrombosis of underexpanded stents. The stents were recalcitrant to aggressive balloon dilation and in the setting of an acute myocardial infarction; rotational atherectomy is a relative contraindication. The use of concurrent contrast during laser atherectomy resulted in plaque modification and subsequent stent expansion.

Coronary Intervention with the Excimer Laser: Review of the Technology and Outcome Data

Excimer laser coronary atherectomy (ELCA) is a long-established adjunctive therapy that can be applied during percutaneous coronary intervention (PCI). Technical aspects have evolved and there is an established safety and efficacy record across a number of clinical indications in contemporary interventional practice where complex lesions are routinely encountered. The role of ELCA during PCI for thrombus, non-crossable or non-expandable lesions, chronic occlusions and stent under-expansion are discussed in this review. The key advantage of ELCA over alternative atherectomy interventions is delivery on a standard 0.014-inch guidewire. Additionally, the technique can be mastered by any operator after a short period of training. The major limitation is presence of heavy calcification although when rotational atherectomy (RA) is required but cannot be applied due to inability to deliver the dedicated RotaWire^TM (Boston Scientific), ELCA can create an upstream channel to permit RotaWire passage and complete the case with RA - the RASER technique.

Immediate and midterm follow-up results of excimer laser application in complex percutaneous coronary interventions: Report from a single center experience

OBJECTIVE

To assess the efficacy and safety of laser-assisted percutaneous coronary interventions (PCI) in an unselected population.

METHODS

One hundred consecutive patients, who underwent a laser assisted PCI between January 2008 and March 2012, were included in the present study. Fifty-one patients underwent laser ablation for thrombus vaporization (Group 1), 36 patients for neointima/plaque debulking (Group 2) and 13 patients for lesion compliance modification in calcified lesions (Group 3).

RESULTS

The rate of in-hospital serious events was 2%. The cumulative laser success was 82%, and it was significantly higher for Group 1 and Group 2 in comparison with Group 3 (p = 0.001). Furthermore, the need for repeat revascularization was significantly higher in the Group 3 compared with the others two groups (46% vs. 8% for Group 1 and 11% for Group 2, p = 0.03). The MACE rate was 14%. There was a trend toward a higher MACE rate in the Group 3 compared with others two groups (p = 0.05).

CONCLUSIONS

Laser ablation is an effective and safe tool for complex PCI. Patients underwent laser for thrombus vaporization or for neointima/plaque debulking had better immediate success and better outcome at follow-up than patients underwent laser for lesion compliance modification.

Treatment of subacute and chronic thrombotic occlusions of lower extremity peripheral arteries with the excimer laser: a feasibility study

BACKGROUND

Thrombus is highly prevalent in patients with recent symptoms (< 6 months) of claudication or limb ischemia due to an occluded culprit lower extremity vessels. Treatment of these thrombotic occlusions is challenging. In this feasibility study, the excimer laser (Spectranetics, Colorado Springs, CO) has been tested for its safety and ability to ablate thrombus in patients with recent arterial occlusions.

METHODS

Angiographic operator assessment and volumetric core lab quantitation of the thrombus were performed at baseline and after excimer laser but prior to definitive treatment of the vessel to evaluate thrombus resolution. Consecutive patients were prospectively enrolled at a single site. Procedural success was defined as achieving a residual stenosis of <30% after final treatment with no intraprocedural complications requiring additional treatment.

RESULTS

20 consecutive patients were enrolled in this study (8 males, mean age 69.5±11.1 years). Based on patients symptom onset, 12 patients were subacute (> 24 h, < 30 days), and 8 chronic (between 1 to 6 months). 15/20 (75%) had restenotic occlusions. Due to the long, occlusive nature of these lesions, only 8 patients had complete intravascular ultrasound images at each time point which allowed volumetric analysis by the core lab. There was no statistical difference in plaque/thrombus volume between baseline (pretreatment) and excimer laser (P=.68). There was however a significant reduction in residual angiographic stenosis post laser alone (100% vs. 66.75%±23.9%, P=.001). Procedural success was 100%. There were no deaths or amputations. Bail out stenting was performed in 10/20 (50%) patients. Embolic filters were used in 15/20 (75%) of patients. Macrodebris>2 mm were seen in 85.7% of filters. There was no in-hospital or 30-day reocclusion of the treated vessel but one patient had a vascular access complication (small AV fistula) conservatively managed. No other serious adverse events were noted.

CONCLUSION

Using the excimer laser appears safe in this small feasibility study of subacute and chronic thrombotic occlusions. Angiographically, there was a significant reduction in percent stenosis with the laser alone. The limited IVUS data did not show a reduction in plaque/thrombus volume but the number of interpretable ultrasounds was small. Further data are needed to address the effectiveness of the laser in treating these thrombotic occlusions and its advantages over balloon angioplasty.

Excimer laser coronary angioplasty with manual thrombus aspiration for a case of very late stent thrombosis of sirolimus-eluting stent

Very late stent thrombosis occurring after drug-eluting stent implantation is a rare complication. However, it is often associated with poor outcome. Manual thrombectomy has been shown to lower the rate of distal embolization in the case of ST-elevation myocardial infarction of native coronary arteries. However, the presence of abundant thrombus material may lead to manual thrombus aspiration failure. Here, we describe the case of a patient with acute myocardial infarction due to stent thrombosis of a sirolimus-eluting stent occurring 50 months after stent deployment showing abundant thrombus material, which led to manual thrombus aspiration failure and was then successfully treated by excimer laser coronary angioplasty. In these cases, excimer laser coronary angioplasty may be useful due to its ability to dissolve thrombus.

Excimer laser in myocardial infarction: a comparison between STEMI patients with established Q-wave versus patients with non-STEMI (non-Q)

Patients sustaining acute myocardial infarction (AMI) often require urgent percutaneous revascularization within the first 24 h from onset of the infarction due to continuous ischemia and hemodynamic instability. Upon arrival to the cardiac catheterization, the electrocardiogram of AMI patients may exhibit acute ST-elevation (STEMI) with or without accompanying Q-wave or depression of the ST segment (non-STEMI or non-Q-wave infarction). Data comparing acute outcome of device application in patients presenting for urgent revascularization with established Q-wave myocardial infarction (QWMI) versus those with non-STEMI (NQMI) are sparse. Excimer laser is a revascularization modality applied for debulking of atherosclerotic plaque and vaporization of associated thrombus in the setting of AMI. One hundred fifty-one AMI patients with continuous chest pain and ischemia who enrolled into a multicenter study and underwent urgent revascularization were divided for the purpose of a retrospective analysis into two groups. One group presented with established electrocardiographic Q-wave, whereas the other had ST-depression (NQMI). In comparison with the NQMI group, the QWMI patients had a higher incidence of failed thrombolytic therapy (17% vs 3, p = 0.006), cardiogenic shock (20 vs 6%, p = 0.01), left anterior descending as a culprit infarct-related vessel (46 vs 14%, p < 0.0001), a higher incidence of TIMI 0 flow (48 vs 24%, p = 0.04), a heavier thrombus burden (grade 4 TIMI thrombus, 58 vs 23%; p = 0.0001), and higher CPK (1272 +/- 2180 vs 404 +/- 577, p = 0.001) and troponin levels (62 +/- 95 vs 14 +/- 48, p = 0.0003). Both groups underwent laser angioplasty and stenting for relief of continuous chest pain and ischemia within 24 h of infarction onset. Quantitative coronary arteriography in an independent core laboratory measured similar improvement in baseline minimal luminal diameter and percent diameter stenosis by application of laser energy in both groups. Among the QWMI patients, a significantly higher acute gain was recorded with the laser treatment in lesions containing a large/extensive thrombus burden as compared with lesions containing only a small clot burden (1.2 +/- 0.7 vs 0.8 +/- 0.5, p = 0.01). Such a phenomenon was not detected among the NQMI patients (1.0 +/- 0.5 vs 0.8 +/- 0.6, p=ns). Baseline TIMI flow grade (0.9 +/- 1.0 for QWMI vs 1.5 +/- 1.2 for NQMI, p = 0.0001) increased with laser emission to 2.8 +/- 0.5 and subsequently reached a final level of TIMI 3 in both groups. In comparison with the QWMI patients, there was a trend toward a reduced rate of major adverse coronary events among the NQMI patients (12% QWMI vs 4% NQMI, p = 0.09). Significant differences in baseline clinical characteristics, extent of myocardial damage, location of infarct related vessel, thrombus burden, and TIMI flow exist between QWMI and NQMI patients who require urgent intervention. However, application of excimer laser results in similar high procedural success and low complication rates in both groups. Maximal acute laser gain is achieved among QWMI patients whose lesions are laden with a heavy thrombus burden.

Initial thrombosuction with subsequent angioplasty in primary coronary intervention—comparison with conventional strategy

BACKGROUND

Large thrombus burden remains challenging in the setting of acute myocardial infarct. Initial thrombosuction (IT) followed by actual angioplasty may be advantageous over conventional strategy in primary percutaneous coronary intervention (PCI).

METHODS

With a case-control design, 22 consecutive patients receiving primary PCI with IT were designated as group 1. Another 22 well-matched patients undergoing primary PCI with conventional strategy in the same period were enrolled as group 2. Clinical and angiographic outcomes, procedural parameters and resource usage were compared.

RESULTS

Baseline characteristics were comparable, including the symptom onset-to-needle time (250+/-101 vs. 261+/-149 min, p = NS). Total procedure time (33+/-14 vs. 47+/-20 min, p = 0.011), fluoroscopy time (10+/-6 vs. 16+/-10 min, p = 0.014) and contrast medium consumption (140+/-40 vs. 170+/-50 ml, p = 0.024) were all significantly reduced with group 1. No-reflow occurred less frequently with group 1 (5% vs. 32%, p = 0.046) during intervention, and TIMI 3 flow was established more quickly (19+/-10 vs. 30+/-20 min, p = 0.024). Final TIMI 3 flow rates and stent rates were similar. The time to myocardial enzyme peak was shorter with group 1 (9.7+/-3.1 vs. 12.8+/-6.3 h, p = 0.048), but no difference was found in 3 months cumulative major cardiac adverse event rates.

CONCLUSIONS

Primary PCI with IT achieves earlier reperfusion and is more efficient in terms of time and resource, comparing to conventional strategy.

Prevention of distal embolization and no-reflow in patients with acute myocardial infarction and total occlusion in the infarct-related vessel: A subgroup analysis of the cohort of acute revascularization in myocardial infarction with excimer laser?CARMEL multicenter study

To overcome the adverse complications of percutaneous coronary interventions in thrombus laden lesions (i.e., distal embolization, platelet activation, no-reflow phenomenon), mechanical removal of the thrombus or distal embolization protection devices are frequently required. Pulsed-wave ultraviolet excimer laser light at 308 nm can vaporize thrombus, suppress platelet aggregation, and, unlike other thrombectomy devices, ablate the underlying plaque. The following multicenter registry was instituted to evaluate the safety and efficacy of laser ablation in patients presenting with acute myocardial infarction (AMI) complicated by persistent thrombotic occlusions. Patients with AMI and complete thrombotic occlusion of the infarct-related vessel were included in eight participating centers. Patients with further compromising conditions (i.e., cardiogenic shock, thrombolysis failures) were also included. Primary endpoint was procedural respective laser success; secondary combined endpoints were TIMI flow and % stenosis by quantitative coronary analysis and visual assessment at 1-month follow-up. Eighty-four percent of all patients enrolled (n = 56) had a very large thrombus burden (TIMI thrombus scale > or = 3), and 49% were compromised by complex clinical presentation, i.e., cardiogenic shock (21%), degenerated saphenous vein grafts (26%), or thrombolysis failures (5%). Laser success was achieved in 89%, angiographic success in 93%, and the overall procedural success rate was 86%. The angiographic prelaser total occlusion was reduced angiographically to 58% +/- 25% after laser treatment and to 4% +/- 13% final residual stenosis after adjunctive balloon angioplasty and/or stent placement. TIMI flow increased significantly from grade 0 to 2.7 +/- 0.5 following laser ablation (P < 0.001) and 3.0 +/- 0.2 upon completion of the angioplasty procedure (P > 0.001 vs. baseline). Distal embolizations occurred in 4%, no-reflow was observed in 2%, and perforations in 0.6% of cases. Laser-associated major dissections occurred in 4% of cases, and total MACE was 13%. The safety and efficacy of excimer laser for thrombus dissolution in a cohort of high-risk patients presenting with AMI and total thrombotic occlusion in the infarct-related vessel are encouraging and should lead to further investigation.

Power thrombectomy in acute ischemic coronary syndromes

Intracoronary thrombi are commonly found in patients with acute coronary syndromes. A large thrombus burden or a platelet-rich thrombus frequently resists pharmacologic therapy ("thrombolytic ceiling"). In such cases restoration of adequate antegrade coronary flow necessitates application of a mechanical force. Power thrombectomy is a revascularization strategy incorporating a mechanical device for removal of occlusive coronary thrombi in conjunction with or following administration of either platelet glycoprotein IIb/IIIa receptor inhibitors or thrombolytic agents, or both. Mechanical devices for power thrombectomy include ultrasound sonication, rheolytic thrombectomy (Angiojet), laser, transluminal extraction catheter, aspiration catheter, and to a limited extent, balloon angioplasty. In acute coronary syndromes the strategy of power thrombectomy aims to achieve the clinical advantages of more nearly complete vessel patency, improved antegrade flow, and enhanced preservation of myocardial tissue.

Rapid thrombectomy for treatment of macroembolization during percutaneous coronary intervention in the setting of acute myocardial infarction

We report the use of the Export catheter as an urgent modality to aspirate thrombus that embolized down the left anterior descending artery during acute myocardial infarction.