Physics-Informed Modeling and Control of Multi-Actuator Soft Catheter Robots

Catheter-based endovascular interventional procedures have become increasingly popular in recent years as they are less invasive and patients spend less time in the hospital with less recovery time and less pain. These advantages have led to a significant growth in the number of procedures that are performed annually. However, it is still challenging to position a catheter in a target vessel branch within the highly complicated and delicate vascular structure. In fact, vessel tortuosity and angulation, which cause difficulties in catheterization and reaching the target site, have been reported as the main causes of failure in endovascular procedures. Maneuverability of a catheter for intravascular navigation is a key to reaching the target area; ability of a catheter to move within the target vessel during trajectory tracking thus affects to a great extent the length and success of the procedure. To address this issue, this paper models soft catheter robots with multiple actuators and provides a time-dependent model for characterizing the dynamics of multi-actuator soft catheter robots. Built on this model, an efficient and scalable optimization-based framework is developed for guiding the catheter to pass through arteries and reach the target where an aneurysm is located. The proposed framework models the deflection of the multi-actuator soft catheter robot and develops a control strategy for movement of catheter along a desired trajectory. This provides a simulation-based framework for selection of catheters prior to endovascular catheterization procedures, assuring that given a fixed design, the catheter is able to reach the target location. The results demonstrate the benefits that can be achieved by design and control of catheters with multiple number of actuators for navigation into small vessels.

Roadmap Guided Direct Percutaneous Vertebral Artery Puncture for Mechanical Thrombectomy of Acute Basilar Artery Occlusion: A Technical Case Report and Review of the Literature

Access techniques for mechanical thrombectomy normally include percutaneous puncture of the common femoral or, more recently, the radial artery. Although target vessel catheterization may frequently not be devoid of difficulties via both routes, the vast majority of mechanical thrombectomy (MT) cases can be successfully managed. However, in a significant minority of cases, a stable target vessel access cannot be reached resulting in futile recanalization procedures and detrimental outcomes for the patients. As such, in analogy to direct carotid puncture for anterior circulation MT, direct vertebral artery (VA) puncture (DVP) is a direct cervical approach, which can constitute the only feasible access to the posterior circulation in highly selected cases. So far, due to the rarity of DVP, only anecdotal evidence from isolated case reports is available and this approach raises concerns with regard to safety issues, feasibility, and technical realization. We present a case in which bail-out access to the posterior circulation was successfully obtained through a roadmap-guided lateral direct puncture of the V2 segment of the cervical VA and give an overview of technical nuances of published DVP approaches for posterior circulation MT.

Percutaneous catheter-based repeat revascularization in patients with previous PCI or CABG: a comprehensive review of the evidence

Repeat revascularization after percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) is one of the most common long-term complications which warrants continuous clinical follow up. Re-interventions negatively impact long-term survival in patients with coronary artery disease. The repeat revascularization after PCI can be either a target lesion revascularization (stent thrombosis/in-stent restenosis) or a revascularization of native coronary artery after PCI (target vessel revascularization/non-target vessel revascularization). The EVENT registry reports that repeat revascularization rates in patients undergoing PCI is 12% in the first year of follow up. Repeat revascularization with additional stent deployment increases the rate of stent thrombosis and restenosis, thereby leading to recurrent ischemic events. Repeat revascularization after CABG can be either in the early postoperative period or later due to native disease progression or late graft stenosis. The need for re-intervention after surgical or percutaneous revascularization is inevitable and is dependent on modifiable and non-modifiable risk factors.

Effect of Coronary Disease Characteristics on Prognostic Relevance of Residual Ischemia After Stent Implantation

Objectives: We investigated the influence of coronary disease characteristics on prognostic implications of residual ischemia after coronary stent implantation.Methods: This study included 1,476 patients with drug-eluting stent implantation and available pre- and post-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) measurements. Residual ischemia was defined as post-PCI FFR ≤ 0.80. Coronary disease characteristics with significant interaction hazard ratios (HRs) for clinical outcomes with residual ischemia were defined as interaction characteristics with residual ischemia (ICwRI). The primary outcome was target vessel failure (TVF)—a composite of cardiac death, target vessel myocardial infarction, and target vessel revascularization—at 2 years.Results: The mean pre- and post-PCI FFR were 0.68 ± 0.11 and 0.87 ± 0.07, respectively. During the median follow-up duration of 2.0 years, the cumulative incidence of TVF was 6.1%. The 203 vessels (13.8%) with residual ischemia had higher risks of TVF compared to that for post-PCI FFR >0.80 (P < 0.001). ICwRI with a significant interaction HR with residual ischemia included pre-PCI SYNTAX score >17 and pre-PCI FFR ≤ 0.62. Each ICwRI had a direct prognostic effect not mediated by residual ischemia. The association between an increased TVF risk and residual ischemia was significant in patients with 0 or 1 ICwRI [hazard ratio (HR) 3.25, 95% confidence interval (CI) 1.90–5.57, P < 0.001] but not in those with 2 ICwRI (HR 0.47, 95% CI 0.14–1.64, P = 0.24). Among patients with post-PCI FFR >0.80, those with 2 ICwRI showed similar TVF risks to those with residual ischemia (HR 1.55, 95% CI 0.79–3.02, P = 0.20).Conclusions: Coronary disease characteristics including pre-PCI SYNTAX score and pre-PCI FFR affected the prognostic implications of residual ischemia. The prognostic relevance of residual ischemia was attenuated in patients with multiple interacting characteristics.

233 Prognostic implications of the automated detection of lipid core burden index at optical coherence tomography: post hoc analysis of the CLIMA study

Aims Plaque vulnerability features are associated with major coronary events and poor outcomes. However, routinary and reproducible manual assessment of plaque vulnerability features at optical coherence tomography (OCT) is still challenging. We recently developed and validated an OCT-derived automated approach that can identify the intra-plaque lipid core burden index (LCBI). Our aim was to investigate the association between the automated detection of OCT-derived LCBI and clinical events. Methods and results We conducted a post hoc analysis of the CLIMA study, a large prospective observational, multicentre registry recruiting all consecutive patients undergoing assessment of the proximal left anterior descending artery (LAD) segment by OCT in the context of clinically indicated coronary angiography. The automated detection of maximum LCBI was carried out in 4 mm of intervention-naïve proximal LAD segment (maxLCBI4mm) by using the validated software. The mean and median value of LCBI in all study population (n = 1003) was 407.6 and 411.1, respectively. Patients with higher LCBI (≥400) were more frequently male (P = 0.016) and affected by insulin-dependent diabetes mellitus (0.046). Furthermore, they showed more frequently at OCT analysis the vulnerable plaque characteristics investigated in the CLIMA study (Table 1). At Cox regression analysis, a maxLCBI4mm ≥400 predicted at 1 year both a hard endpoint of cardiac death and target-vessel myocardial infarction [hazard ratio (HR): 2.56, 95% confidence interval (CI): 1.2–5.3, P 0.011], as well as a composite endpoint of cardiac death, any myocardial infarction and target vessel revascularization (HR: 1.87, 95% CI: 1.1–3.1, P = 0.011). Conclusions In our study, the automated detection of LCBI at OCT was feasible and related to poorer clinical outcome at 1-year follow-up.

Effect of Timing of Staged Percutaneous Coronary Intervention on Clinical Outcomes in Patients With Acute Coronary Syndromes

Background Complete revascularization reduces cardiovascular events in patients with acute coronary syndromes (ACSs) and multivessel disease. The optimal time point of non–target‐vessel percutaneous coronary intervention (PCI) remains a matter of debate. The aim of this study was to investigate the impact of early (<4 weeks) versus late (≥4 weeks) staged PCI of non–target‐vessels in patients with ACS scheduled for staged PCI after hospital discharge. Methods and Results All patients with ACS undergoing planned staged PCI from 2009 to 2017 at Bern University Hospital, Switzerland, were analyzed. Patients with cardiogenic shock, in‐hospital staged PCI, staged cardiac surgery, and multiple staged PCIs were excluded. The primary end point was all‐cause death, recurrent myocardial infarction and urgent premature non–target‐vessel PCI. Of 8657 patients with ACS, staged revascularization was planned in 1764 patients, of whom 1432 patients fulfilled the eligibility criteria. At 1 year, there were no significant differences in the crude or adjusted rates of the primary end point (7.8% early versus 10.8% late, hazard ratio [HR], 0.72 [95% CI, 0.47–1.10], P =0.129; adjusted HR, 0.80 [95% CI, 0.50–1.28], P =0.346) and its individual components (all‐cause death: 1.5% versus 2.9%, HR, 0.52 [95% CI, 0.20–1.33], P =0.170; adjusted HR, 0.62 [95% CI, 0.23–1.67], P =0.343; recurrent myocardial infarction: 4.2% versus 4.4%, HR, 0.97 [95% CI, 0.475–1.10], P =0.924; adjusted HR, 1.03 [95% CI, 0.53–2.01], P =0.935; non–target‐vessel PCI, 3.9% versus 5.7%, HR, 0.97 [95% CI, 0.53–1.80], P =0.928; adjusted HR, 1.19 [95% CI, 0.61–2.34], P =0.609). Conclusions In this single‐center cohort study of patients with ACS scheduled to undergo staged PCI after hospital discharge, early (<4 weeks) versus late (≥4 weeks) staged PCI was associated with a similar rate of major adverse cardiac events at 1 year follow‐up. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02241291.

A novel intracranial exchange guidewire improves the navigation of various endovascular devices: An in vitro study of challenging situations

Objective Neuroendovascular procedures rely on successful navigation and stable access to the target vessel. The Stabilizer is a 300 cm long exchange wire with a 0.014 diameter and a soft, flexible stent at the distal end designed to assist with navigation and device delivery. This study aims to assess the efficacy of the Stabilizer for navigation in a variety of challenging environments. Methods The efficacy of the Stabilizer was evaluated using three challenging vascular models: a giant aneurysm model, a severe tortuosity model, and an M1 stenosis model. The Stabilizer was compared with a conventional wire during navigation in each model. Results In the giant aneurysm model, there was no significant difference of success during straightening of a looped wire and significantly higher success rates when advancing an intermediate catheter with the Stabilizer beyond the aneurysm neck compared to a conventional guidewire. The Stabilizer also significantly increased success rates when advancing an intermediate catheter through a model with severe tortuosity compared to a conventional guidewire, as well as exchange maneuver for intracranial stenting in a stenosis model compared to an exchange wire. Conclusions In our experimental model, the Stabilizer significantly improved navigation and device delivery in a variety of challenging settings compared to conventional wires.

Clinical outcomes in 2481 unselected real-world patients treated with a polymer-free sirolimus-eluting stent: 3 years results from the NANO multicenter Registry

Objectives To evaluate the 3-year clinical outcomes of a polymer-free sirolimus-eluting, Nano plus stent for the treatment of coronary artery disease in the NANO multicenter Registry. Background The long-term clinical data evaluating the safety and efficacy of the novel polymer-free sirolimus-eluting Nano plus stent (Lepu Medical, Beijing, China) is limited. Methods The NANO all-comers Registry trial was a prospective, multicenter clinical registry conducted in 26 centers in China between August 2016 and January 2017. A total of 2481 consecutive patients were exclusively treated with the Nano plus stent. The primary clinical endpoint, target lesion failure (TLF, defined as cardiac death, target vessel nonfatal myocardial infarction, and clinically driven target lesion revascularization [CD-TLR]), was analyzed at 3 years. Results At 3 years, 2295 patients (92.5%) were followed. The incidence of TLF was 6.8% (168/2481). The rate of cardiac death was 3.8% (94/2481), target vessel nonfatal myocardial infarction 0.7% (18/2481), and CD-TLR 2.9% (68/2481). The rate of definite/probable stent thrombosis was 0.5% (13/2481). The risk factors of diabetes mellitus, acute myocardial infarction, age, chronic renal failure, in-stent restenosis, chronic total occlusion, and left ventricular ejection fraction < 40% were the independent predictors of 3-year TLF. Conclusions At three years, the rate of TLF was relatively low in patients treated with the polymer-free Nano plus stent. The polymer-free Nano plus stent showed a favorable safety and efficacy profile in real-world patients. Clinical trial registration URL: https://www.clinicaltrials.gov/. Unique identifier: NCT02929030.

Depth-targeted intracortical microstroke by two-photon photothrombosis in rodent brain

Significance: Photothrombosis is a widely used model of ischemic stroke in rodent experiments. In the photothromboris model, the photosensitizer Rose Bengal is systemically introduced to the blood stream and activated by green light to induce aggregation of platelets that eventually cause vessel occlusion. Since the activation of Rose Bengal is a one-photon phenomenon and the molecules in the illuminated area (light path) are subject to excitation, targeting of thrombosis is unspecific especially in the depth dimension. We have developed a photothrombosis protocol that can target a single vessel in the cortical parenchyma by two-photon excitation. Aim: We aim to induce a thrombotic stroke in the cortical parenchyma by two-photon activation of Rose Bengal so that we confine photothrombosis within a vessel of a target depth. Approach: FITC-dextran is injected into the blood stream to visualize the cerebral blood flow in anesthetized adult mice with a cranial window. After a target vessel is chosen by two-photon imaging (950 nm), Rose Bengal is injected into the blood stream. The scanning wavelength is changed to 720 nm and photothrombosis was induced by scanning the target vessel. Results: Two-photon depth-targeted single vessel photothrombosis was achieved with a success rate of 84.9+/-1.7% within 80 s. Attempts without Rose Bengal (i.e., only with FITC) did not result in photothrombosis at the excitation wavelength of 720 nm. Conclusions: We described a protocol that achieves depth-targeted single vessel photothrombosis by two-photon excitation. Simultaneous imaging of blood flow in the targeted vessel using FITC dextran enabled the confirmation of vessel occlusion and prevention of excess irradiation that possibly induces unintended photodamage.