Experimental investigation of the abrasive crown dynamics in orbital atherectomy

Electroplating a miniature diamond wheel for grinding of the calcified plaque inside arteries

A miniature grinding wheel (0.85 mm diameter) was fabricated by nickel (Ni)-diamond electroplating on a thin (0.65 mm outer diameter) flexible hollow stainless steel drive shaft to remove the calcified plaque in coronary and peripheral arteries by atherectomy procedure. To coat electrically nonconductive diamond grits, the drive shaft was submerged in a pile of diamond grit during Ni electroplating. The electroplating current density and temperature were investigated for better surface finishing and Faraday efficiency. The electroplating time to obtain the designed coating thickness was modeled based on Faraday's law of electrolysis and the geometry of drive shaft, wheel, and diamond grit. To validate the miniature wheel performance in atherectomy, grinding experiments were conducted on an atherectomy cardiovascular simulator with a calcified plaque surrogate. The wheel motion, material removal rate, and wheel surface wear were studied via high-speed camera imaging and laser confocal microscopy. The grinding wheel with 80,000 rpm rotational speed had an orbital speed of 14,300 rpm around the 1.5 mm diameter plaque surrogate lumen. After grinding for 120 s, the plaque surrogate inner diameter was enlarged to 3.03 mm, and no wear or loss of diamond abrasive was observed on the grinding wheel. This study demonstrated that the proposed electroplating process for fabricating miniature grinding wheels could effectively remove the calcified plaque surrogate. This research could lead to a more effective and safer atherectomy device with sub-mm miniature diamond wheels to treat lesions deep in coronary and peripheral arteries.

Active matter therapeutics

Nanotherapies based on micelles, liposomes, polymersomes, nanocapsules, magnetic nanoparticles, and noble metal nanoparticles have been at the forefront of drug delivery in the past few decades. Some of these nanopharmaceuticals have been commercially applied to treat a wide range of diseases, from dry eye syndrome to cancer. However, the majority involve particles that are passive, meaning that they do not change shape, and they lack motility; the static features can limit their therapeutic efficacy. In this review, we take a critical look at an emerging field that seeks to utilize active matter for therapeutics. In this context, active matter can be broadly referred to as micro or nanosized constructs that energetically react with their environment or external fields and translate, rotate, vibrate or change shape. Essentially, the recent literature suggests that such particles could significantly augment present-day drug delivery, by enhancing transport and increasing permeability across anatomical barriers by transporting drugs within solid tumor microenvironments or disrupting cardiovascular plaque. We discuss examples of such particles and link the transport and permeability properties of active matter to potential therapeutic applications in the context of two major diseases, namely cancer and heart disease. We also discuss potential challenges, opportunities, and translational hurdles.

Orbital atherectomy for calcified femoropopliteal lesions: a current review

The orbital atherectomy system is a novel form of atherectomy that uses orbital sanding and pulsatile forces, an effective method of treatment for peripheral atherosclerotic lesions with varying levels of occlusion. Although the devices only has a general indication from the FDA to treat atherosclerotic lesions, they are effective in treating all kinds of lesions, and can therefore mitigate effects of all severities of peripheral artery disease. This approach to endovascular therapy involves the use of differential sanding to preferentially ablate fibrous, fibrofatty and calcified lesions, while deflecting healthy intima away from the crown. The eccentrically mounted crown design allows the device to employ rhythmic pulsating forces that penetrate the medial layer, and cause cracking in the lesions in order to facilitate easier balloon inflation and intravascular drug elution. The combination of vessel modification and lumen enlargement through sanding can effectively restore blood flow to the extremities, and can eliminate risk of critical limb ischemia, as well as subsequent amputation. Extensive lab testing and clinical trials have confirmed the high success rates and low major adverse events associated with this form of treatment. The device is economically viable as well, since its cost is offset by the lower frequency of adjunctive therapy sessions when compared to other devices. Considering the results outlined in this manuscript, the Diamondback 360° is an effective form of atherectomy therapy for peripheral artery disease. In-depth understanding of the operation preparation, procedure, and best imaging techniques can help to optimize outcomes.

Plaque modification of severely calcified coronary lesions via orbital atherectomy: Single-center observations from a complex Veterans Affairs cohort

BACKGROUND

Orbital atherectomy (OA) is a known alternative to other atherectomy devices. However, some complex patient demographics (eg, left ventricular ejection fraction <25%) were excluded from the first-in-human trial (ORBIT I) and the pivotal FDA device approval trial (ORBIT II) which evaluated the safety and efficacy of OA in severely calcified de novo coronary lesions. This single-operator cohort study aimed to examine the impact of OA on a real-world complex Veterans Affairs patient subset.

METHODS

Retrospective analysis was completed on 40 consecutive patients with severely calcified coronary lesions who underwent OA prior to drug-eluting stent placement at the Atlanta Veterans Affairs Medical Center from January 2015 to June 2017.

RESULTS

Orbital atherectomy plus drug-eluting stent placement was successful in all 40 cases. Chocolate focal force balloon angioplasty was the most commonly used post-atherectomy balloon (N = 34, 85%). Few complications were observed, including one case (2.5%) of perforation and one case (2.5%) of no-reflow. Neither acute stent thrombosis nor emergent coronary artery bypass grafting was observed. The intravascular ultrasound (IVUS)-determined median [IQR] pre-procedure minimum lumen area and post-procedure minimum stent area (MSA) were 2.8 [2.2, 3.0] mm2 and 8.7 [7.7, 10.0] mm2, respectively (P < 0.0001, Mann-Whitney test). Major adverse cardiovascular events, including all-cause mortality, at 30 days and at a median [IQR] follow-up of 197.5 [35.5, 461.3] days, was 5% and 10%, respectively. During that period, one target vessel revascularization (2.5%) was observed.

CONCLUSIONS

This study indicates that OA is a useful tool in performing high-risk percutaneous coronary intervention effectively in VA patients with severely calcified coronary lesions. OA plaque modification in combination with a high utilization rate of IVUS and Chocolate focal force angioplasty facilitates stent delivery and optimal stent expansion, resulting in a large MSA.

Computational Fluid Dynamics Modeling of the Burr Orbital Motion in Rotational Atherectomy with Particle Image Velocimetry Validation

Rotational atherectomy (RA) uses a high-speed rotating burr introduced via a catheter through the artery to remove hardened atherosclerotic plaque. Current clinical RA technique lacks consensus on burr size and rotational speed. The rotating burr orbits inside the artery due to the fluid force of the blood. Different from a common RA technique of upsizing burrs for larger luminal gain, a small burr can orbit to treat a large lumen. A 3D computational fluid dynamics (CFD) model was developed to simulate the burr motion and study the fluid flow and force in RA. A particle image velocimetry experiment was conducted to measure and validate the flow field including the radial and axial velocities and a pair of counter-rotating vortices near the burr equator in CFD. The hydraulic force on the burr and the contact force between the burr and the arterial wall were estimated by CFD. The contact force can be reduced by using smaller burr and lower rotational speed. Utilizing the small burr orbital motion has the potential to be an improved RA technique.

Orbital and rotational atherectomy during percutaneous coronary intervention for coronary artery calcification

Severe coronary artery calcification (CAC) increases the complexity of percutaneous coronary intervention (PCI) by inhibiting optimal stent expansion, leading to an increased risk of death, myocardial infarction, repeat revascularization, and stent thrombosis. Coronary atherectomy modifies and debulks calcified plaque to facilitate PCI. Although there is no clear consensus, and further studies are needed, the decision to perform atherectomy should be based upon the presence of fluoroscopic CAC or with the use of intravascular imaging. The management of CAC in the modern era relies on rotational and orbital atherectomy to prepare the lesion to facilitate stent delivery and optimal expansion. While the two technologies differ in equipment, technique, and mechanism of action, the available literature suggests similar efficacy and safety of the two systems, although head-to-head comparisons are limited. While rotational and orbital atherectomy have been shown to have excellent procedural success in terms of facilitating stent delivery, no system has been shown to reduce long-term major adverse cardiovascular events, although the definitive trial for orbital atherectomy has not been completed. Additional trials are needed to find the population who would derive the most benefit of atherectomy and to compare the two systems in a prospective manner.

Comparison of Rotational Atherectomy Versus Orbital Atherectomy for the Treatment of Heavily Calcified Coronary Plaques

We evaluated the outcomes of patients with severe coronary artery calcification (CAC) who underwent rotational atherectomy (RA) and orbital atherectomy (OA). Severe CAC increases the complexity of percutaneous coronary intervention (PCI) because of the difficulty in optimizing stent expansion, leading to worse clinical outcomes. Both devices are effective treatment strategies for severe CAC. No comparisons have been performed to evaluate the clinical outcomes after RA and OA. The outcomes of 67 patients with severe CAC who underwent RA from July 2012 to June 2015 and 60 patients who underwent OA from February 2014 to September 2016 were evaluated. The primary end point was the rate of 30-day major adverse cardiac and cerebrovascular events, comprising cardiac death, myocardial infarction, target vessel revascularization, and stroke. The primary end point was similar in the RA and OA groups (6% vs 6%, p >0.9), as were the individual end points of death (0% vs 2%, p = 0.8), myocardial infarction (6% vs 4%, p = 0.7), target vessel revascularization (0% vs 0%, p >0.9), and stroke (0% vs 0%, p >9). Procedural success was achieved in all patients. Angiographic complications were uncommon in both groups. No patient had stent thrombosis. In conclusion, both RA and OA are safe and effective for the treatment of severe CAC as they provided similar clinical outcomes at short-term follow-up.