Magnetic navigation in percutaneous coronary intervention

Comparative Study of Application of Computed Tomography/Ultrasound and Computed Tomography Imaging Guidance Methods in the Microwave Ablation of Liver Cancer

PURPOSE

The aim of the study is to assess the clinical value of the combined computed tomography (CT)/ultrasound (US) guidance in microwave ablation (MWA) for hepatocellular carcinoma (HCC).

METHODS

From July 16, 2016, to June 20, 2021, medical records of 150 HCC patients treated with MWA were retrospectively analyzed. Ninety-two patients with 115 liver tumors underwent MWA under combined CT/US guidance, and 58 patients with 73 liver tumors received MWA under CT guidance alone. The clinical efficacy of combined CT/US-guided MWA was analyzed. We compared the complications, procedure time, and CT scan times between the 2 groups.

RESULTS

The total complete ablation rate and complete ablation rate of high-risk location tumors were significantly higher in the group treated with combined CT/US guidance ( P = 0.0471 and P = 0.0347, respectively), the imaging guidance modality (odds ratio, 0.303; 95% confidence interval [CI], 0.095-0.970; P = 0.044) was an independent factor for ablation efficacy. These 2 groups also had significant differences in the procedure time ( P = 0.0171), the incidence rate of pneumothorax ( P = 0.0209), abdominal pain ( P = 0.0196), nausea or vomiting ( P = 0.0026), and intraoperative CT scan times ( P < 0.001). The overall complication rates ( P = 0.4023) and recurrence rates ( P = 0.5063) between the 2 groups were not statistically significant. However, CT/US group has a better short-term progressive free survival (log-rank P = 0.103, Breslow P = 0.030). In multivariate analysis, guidance modality (hazard ratio, 0.586; 95% CI, 0.368-0.934; P = 0.025) and Barcelona Clinic Liver Cancer stage (hazard ratio, 2.933; 95% CI, 1.678-5.127; P < 0.001) were risk factor for progressive free survival.

CONCLUSIONS

Percutaneous MWA under the combined CT/US guidance for HCC can improve clinical benefits.

Comparison of magnetic wire navigation with the conventional wire technique for percutaneous coronary intervention of chronic total occlusions: a randomised, controlled study

Wire crossing of a chronic total coronary occlusion (CTO) is time consuming and limited by the amount of contrast agent and time of radiation exposure. Magnetic wire navigation (MWN) might accelerate wire crossing by maintaining a coaxial vessel orientation. This study compares MWN with the conventional approach for recanalization of CTOs. Forty symptomatic patients with CTO were randomised to MWN (n = 20) or conventional approach (n = 20) for antegrade crossing of the occlusion. In the intention-to-treat analysis, MWN showed a shorter crossing time (412 versus 1131 s; p = 0.001), and, consequently, lower usage of contrast agent (primary endpoint 42 versus 116 ml; p = 0.01), and lower radiation exposure (dose-area product: 29 versus 80 Gy*cm(2); p = 0.002) during wire crossing compared to the conventional approach. Accordingly, in the per-protocol analysis, the wire-crossing rate was, in trend, higher using the conventional approach (17 of 31) compared to MWN (9 of 28; p = 0.08). The use of MWN for revascularisation of CTOs is feasible and reduces crossing time, use of contrast agent, and radiation exposure. However, due to a broader selection of wires, the conventional approach enables wire crossing in cases failed by MWN and seems to be the more successful choice.

Percutaneous radiofrequency ablation of malignant liver tumors with ultrasound and CT fusion imaging guidance

BACKGROUND

To evaluate the feasibility, accuracy, and utility of sonography (US) and CT fusion imaging guidance for radiofrequency ablation (RFA) of malignant liver tumors not visualized on conventional US.

METHODS

Seventy-seven patients with hepatocellular carcinoma and 15 patients with metastatic liver cancer with a total of 136 lesions underwent RFA with US and CT fusion imaging guidance. The mean number of punctures, success rate of a single ablation session, local tumor progression rates, and long-term outcome were evaluated. Treatment efficacy was evaluated by dynamic CT and contrast-enhanced US 1 month after RFA.

RESULTS

RFA was technically feasible in all patients, and no major complications occurred. The mean ± SD time needed to synchronize US and CT images was 13.9 ± 11.9 minutes (range, 5-55 minutes). The success rate of a single ablation session was 83.8% (114/136), and tumor residue was present in 7.4% of lesions (10/136). The mean number of treatment sessions was 1.2 ± 0.5 sessions. During follow-up, local tumor progression was observed for 15 (11.9%) lesions. Distant tumor recurrence was found in 51 (55.4%) patients.

CONCLUSIONS

US and CT fusion-assisted RFA is a safe and efficacious treatment for patients with hepatocellular carcinoma and metastatic liver cancer.

Magnetic navigation facilitates percutaneous coronary intervention for complex lesions

BACKGROUND

We sought to determine the utility of a magnetic navigation system (MNS) in treating a variety of coronary artery lesions including those that could not be revascularized with standard percutaneous coronary intervention (PCI). MNS may add value in the treatment of tortuous arteries and bifurcation lesions; however its widespread adoption has lagged because of cost and a lack of clear advantage over conventional PCI. We performed a retrospective analysis to determine whether MNS improved procedural success for highly complex lesions.

METHODS AND RESULTS

One hundred and forty-eight patients underwent treatment with MNS at Mayo Clinic, Rochester. Clinical data, angiographic and procedural characteristics, lesion crossing success and outcomes were reviewed. Overall 133 patients underwent successful revascularization with 87% (143) of 164 lesions crossed using MNS alone. Another six lesions required a combination of MNS and conventional devices resulting in overall success of 91% (149/164). Eighteen complex lesions had previously failed PCI and 12 (67%) were successfully treated with MNS. Success after failed PCI was higher (88%) when a frequent user operated MNS, but occasional users also noted incremental success (30%). Twenty-five chronic total occlusions were included amongst these 164 lesions, with observed antegrade MNS lesion crossing rates of 78% for regular and 14% for occasional users.

CONCLUSIONS

MNS is a useful adjunct to performance of PCI. This specialized technology has a clear learning curve and can facilitate treatment of highly complex lesions.

Magnetic positioning system in coronary angiography and percutaneous intervention: a feasibility and safety study

OBJECTIVES

This study sought to evaluate the safety and feasibility of a magnetic medical positioning system (MPS) to determine the three-dimensional (3D) position and orientation of intracoronary wires and catheters and to guide angiography and percutaneous coronary intervention (PCI).

BACKGROUND

Coronary angiography relies on fluoroscopy for catheter navigation and often fails to accurately portray vessel tortuosity, overlap, and length because of complex anatomy and foreshortening of curved coronary segments.

METHODS

Forty adult participants underwent coronary angiography and/or PCI with MPS guidance. Two interventional cardiologists independently scored (1-5) the accuracy of MPS catheter tracking projected on live fluoroscopy, recorded cine loops, and 3D vessel reconstructions. Measurements from MPS reconstructions were compared to conventional two-dimensional (2D) quantitative coronary angiography (QCA) measurements. Device procedural success was defined as the ability of the MPS-enabled catheter to reach the target vessel, perform the intended operations, and be retrieved without major adverse cardiac events.

RESULTS

Diagnostic coronary angiography was performed in 19 (47.5%) and PCI in 21 patients (52.5%). MPS procedural success was achieved in 36 (90%) of the cases. MPS accuracy was highest with the MPS superimposed on live fluoroscopy (4.9 ± 0.2/5) and the 3D vessel reconstruction (4.7 ± 0.5/5). MPS length measurements were more accurate than conventional QCA.

CONCLUSIONS

This study demonstrates the feasibility and safety of magnetic catheter tracking with 3D positional data during diagnostic angiography and PCI. Catheter position was accurately projected on real-time fluoroscopy, recorded cine loops, and 3D reconstructions. An MPS may serve as a platform for device navigation and positioning during PCI.

Initial experience with a magnetic navigation system for invasive treatment in patients with non-ST-segment elevation acute coronary syndromes

BACKGROUND

Magnetic navigation system (MNS) assisted percutaneous coronary intervention (MPCI) has been demonstrated an advantage over conventional PCI (CPCI) in complex lesions and tortuous vessels. However, the benefits of MNS in clinical unstable and vulnerable lesions were little studied. The aim of this study is to evaluate the feasibility and benefits of MPCI versus CPCI in patients with non-ST-segment elevation acute coronary syndromes (NSTE-ACS).

METHODS

Thirty-seven consecutive patients with NSTE-ACS undergoing MPCI were compared with 37 matched CPCI patients selected from the same concurrent database. Time to cross lesion, fluoroscopy time, and contrast usage to cross lesion were used as primary end-points.

RESULTS

Of the 37 culprit lesions in MPCI, 36 were crossed successfully giving a success rate of 97.3%. The procedure and the fluoroscopy time to cross the lesion were similar between the magnetic and conventional PCI groups (82.0 ± 67.9 seconds vs. 85.8 ± 59.2 seconds, P = 0.692, and 62.6 ± 57.6 seconds vs. 65.4 ± 49.5 seconds, P = 0.738, respectively). In Type A/B1 lesions, there seemed no difference in contrast use (2.7 ± 0.7 mL vs. 3.3 ± 0.9 mL, P = 0.284). But as lesion complexity increased from type B2 to C, significantly less contrast was needed in type B2 (5.1 ± 2.6 mL vs. 7.9 ± 4.0 mL, P = 0.019) and type C (9.8 ± 5.7 mL vs. 14.7 ± 7.4 mL, P = 0.030). No major adverse cardiac events were observed in either the MPCI or CPCI group.

CONCLUSIONS

MNS assisted technique appears to be feasible and effective in NSTE-ACS patients with more complex lesions; however, it probably offers little benefit in simple lesions like ACC/AHA type A/B1. 

3D reconstruction from contrast coronary angiography in magnetic percutaneous coronary intervention

The magnetic navigation system allows precision wire-tip control that is guided by computer generated 3D models based on fluoroscopic images. These images can be post-processed and the information used to facilitate steering of wires in difficult anatomy. This report illustrates two of these reconstruction software packages in a challenging saphenous vein graft case.

Comparison of magnetically navigated and conventional wire percutaneous coronary intervention of a single discrete stenosis

OBJECTIVE

The objective of this study is to compare magnetic guidewire navigation in percutaneous coronary intervention (MPCI) to conventional percutaneous coronary intervention (CPCI) for the elective treatment of a single discrete stenosis.

BACKGROUND

Magnetic navigation actively steers an angioplasty wire-tip and may improve PCI procedures, but it is not known whether the intricacy and increased preparation necessary for using the system negatively influences the performance of simple procedures in terms of time and contrast use.

METHODS

The procedures of 44 patients (mean age 65 +/- 10 year) undergoing elective single vessel MPCI of a single discrete stenosis were matched for age, gender, and lesion location with 44 concurrent patients (mean age 65 +/- 10 year) undergoing CPCI. The major endpoint was procedural time.

RESULTS

Technical success was defined as an intraluminal wire position distal to the stenosis. Procedural outcome, contrast use, and costs were evaluated. Clinical demographics and angiographic characteristics of the two groups were similar, except for a higher incidence of previous MI and class III angina pectoris in the conventional group. The technical success rate was high and identical in both groups (97.7%). Procedural and fluoroscopy times were not significantly different for MPCI compared to CPCI (21.0 +/- 14.5 min vs. 24.7 +/- 14.0 min; 4.9 +/- 4.8 min vs. 7.3 +/- 10.3 min, P = NS). There was a significant reduction in median contrast use [60 ml/patient (41-100) vs. 100 ml/patient (64-130); P = 0.006].

CONCLUSION

Magnetic navigation does not increase procedural time, irradiation, equipment use, or cost compared to conventional PCI of a single discrete stenosis. It proved feasible, yielding high rates of procedural success with less contrast use.

Primary percutaneous coronary intervention by magnetic navigation compared with conventional wire technique

Aims Comparison of magnetic guidewire navigation in percutaneous coronary intervention (MPCI) vs. conventional percutaneous coronary intervention (CPCI) for the treatment of acute myocardial infarction. Methods and results We compared 65 sequential patients (mean age 61 ± 15 years) undergoing primary MPCI with those of 405 patients undergoing CPCI (mean age 61 ± 13 years). The major endpoint was contrast media use. Technical success and procedural outcomes were evaluated. Clinical demographics and angiographic characteristics of the two groups were similar, except for fewer patients with previous coronary artery bypass grafting (CABG) and hypertension in the CPCI group and fewer patients with diabetes in the MPCI group. The technical success rate was high in both the MPCI and CPCI groups (95.4 vs. 98%). There was significantly less contrast media usage in the MPCI compared with the CPCI group, median reduction of contrast media of 30 mL with an OR = 0.41 (0.21-0.81). Fluoroscopy times were significantly reduced for MPCI compared with CPCI, median reduction of 7.2 min with an OR = 0.42 (0.20-0.79). Conclusion This comparison indicates the feasibility and non-inferiority of magnetic navigation in performing primary PCI and suggests the possibility of reductions in contrast media use and fluoroscopy time compared with CPCI.

Stereotaxis Niobe magnetic navigation system for endocardial catheter ablation and gastrointestinal capsule endoscopy

The use of robotic instruments capable of assisting medical staff during interventional or diagnostic procedures is growing rapidly today. Recently, a robotic system (Niobe, Stereotaxis Inc., USA) has been developed for navigating magnetically enabled tools inside the human body by controlling a magnetic field. This paper reports the fundamentals of this technology and reviews its application in two specific medical fields, cardiology and gastroenterology, in which its uses are different and are at dissimilar stages of development. In the first case, the system is already approved and employed for clinical treatments, such as magnetic steering of endocardial catheters for atrial fibrillation ablation, which is specifically considered in this article. In the second case, initial investigations are being performed today to study the potential magnetic maneuverability of ingestible video capsules adopted for endoscopic explorations of the digestive tract. This paper reviews current achievements and highlights future challenges related to each of these applications.

Magnetically navigated percutaneous coronary intervention in distal and/or complex lesions may improve procedural outcome and material consumption

AIMS

Comparison of magnetic guidewire navigation in percutaneous coronary intervention (magnetic PCI) across distal and/or complex lesions versus conventional navigation (conventional PCI).

METHODS AND RESULTS

Forty-seven consecutive patients (age 61 +/- 10 yr) undergoing elective single vessel magnetic PCI for distal and/or complex lesions were matched by age and lesion location with 45 patients undergoing conventional PCI (age 63 +/- 10 yr). Technical success rate was defined as an intraluminal wire position distal to the stenosis. Procedural outcome and costs were evaluated. Baseline demographics and angiographic characteristics of the two groups were similar. The technical success rate did not differ between magnetic and conventional PCI (95.7 vs 97.8%; p = 1.00). Significantly shorter procedural and fluoroscopy time were observed for magnetic compared to conventional PCI (29.9 +/- 17.6 vs 41.1 +/- 21 min, p = 0.007; 7.5 +/- 7.3 vs 16.1 +/- 22.4 min, p = 0.02 respectively). Less contrast was used in the magnetic PCI group (58 ml/patient; P = 0.02). These advantages resulted in a mean estimated saving of 1400 euro per patient (P < 0.001). Advantages of procedural outcome were even more pronounced in the ACC/AHA lesion class C subgroup.

CONCLUSIONS

Magnetic compared to conventional PCI is an attractive novel technique that proved to be feasible and safe and might be faster in distal and especially complex lesions.

A randomized comparison of the magnetic navigation system versus conventional percutaneous coronary intervention

OBJECTIVE

A randomized comparison of the magnetic navigation system (MNS) to conventional guidewire techniques in percutaneous coronary interventions.

BACKGROUND

The MNS precisely directs a magnetized guidewire in vivo through two permanent external magnets.

METHODS

A total of 111 consecutive patients were enrolled. Crossing success, crossing-/fluoroscopy times, and contrast usage were directly compared. Lesions were classified according to the AHA/ACC criteria. Three tertiles of vessel/lesion complexity [low (<5), medium (6-10) and high (>10)] were defined using 3D reconstructions and angiographic information.

RESULTS

The crossing success for magnetic and the conventional wires were 93.3 and 95.6%, respectively. Crossing and fluoroscopy times were longer with the magnetic wires (72.9 +/- 50.3 sec vs. 58.1 +/- 47.2 sec, P < 0.001 and 66.2 +/- 44.1 sec vs. 55.2 +/- 44.4 sec, P = 0.03, respectively). In vessels with low and medium complexity the magnetic wires had significantly longer times (P < 0.001) but for those with high scores (>10) a trend towards shorter times was observed. The MNS resulted in a small but significant reduction in contrast usage (2.3 +/- 3.5 ml vs. 4.5 +/- 4.4 ml, P < 0.001). Moreover by superimposing a virtual roadmap of the vessel on the live fluoroscopy image 48% of the lesions were crossed without requiring contrast agents with the MNS.

CONCLUSION

The MNS has comparable crossing success to conventional PCI. It is relatively slower but there is a trend to support a potential advantage in more complex vessels. By simultaneously employing a virtual roadmap there is a small but significant reduction in contrast usage.

Radiofrequency ablation of hepatocellular carcinoma: value of virtual CT sonography with magnetic navigation

OBJECTIVE

Virtual CT sonography with magnetic navigation yields cross-sectional images of CT volume data that correspond to the angle of the transducer in the magnetic field in real time. The purpose of this study was to evaluate the efficiency and feasibility of virtual CT sonography for radiofrequency ablation of hypervascular hepatocellular carcinoma poorly defined on B-mode sonography.

MATERIALS AND METHODS

One hundred one patients enrolled in the study were separated into two groups. Fifty-one patients with 65 hepatocellular carcinomas underwent prospective virtual CT sonography as guidance for radiofrequency ablation. Fifty patients with 63 hepatocellular carcinomas managed with B-mode sonographic guidance were retrospectively selected under the same conditions as the virtual CT sonography group to act as a historical control group.

RESULTS

In the virtual CT sonography group, technically successful ablation was achieved in a single session in 92% (47/51) of the patients and in two sessions in 8% (4/51). In the B-mode sonography group, technical success was achieved in a single session in 72% (36/50) of the patients, in two sessions in 24% (12/50), and in three sessions in 4% (2/50). Treatment analysis showed that the technical success rate after a single treatment session was significantly (p = 0.017) higher for the virtual CT sonography group. The number of treatment sessions was significantly (p = 0.021) lower for the virtual CT sonography group (mean, 1.1 +/- 0.1 vs 1.3 +/- 0.3 sessions).

CONCLUSION

Virtual CT sonographically assisted radiofrequency ablation is an efficient treatment of patients with hepatocellular carcinoma that is poorly defined on B-mode sonography.

Use of the Stereotaxis Niobe magnetic navigation system for percutaneous coronary intervention: results from 350 consecutive patients

INTRODUCTION

The Stereotaxis Niobe magnetic navigation system (MNS; Stereotaxis, St. Louis, MO) facilitates precise vector based navigation of magnetically-enabled guidewires for percutaneous coronary intervention (PCI) by using two permanent magnets located on opposite sides of the patient table to produce a controllable magnetic field. The objective of this study is to describe the results of a large patient series using this system, to compare the results with a historical control group, and to detail the MNS learning curve.

METHODS

We prospectively collected data on 439 lesions in 350 consecutive PCI patients using the MNS predominantly using the radial approach. All data were entered into a customized database to capture the key parameters and then compared with a previously collected stent registry from the same center.

RESULTS

In 410/439 lesions (93%) the wire crossed the lesion successfully using the MNS. Twenty-five of the 35 failures were chronic total occlusions. No wire perforations or dissections occurred in this population. Lesion crossing time was 81 +/- 168 sec (mean +/- SD), and fluoroscopy time was 64 +/- 123 sec. A clear learning curve was evident after the first 80 patients. Contrast use was reduced when compared with a historical control group. Procedural and fluoroscopy times were similar.

CONCLUSIONS

Use of the MNS may enable the successful performance of more complex procedures in the cardiac catheterization laboratory with an improvement in time efficiency.

First direct in vivo comparison of two commercially available three-dimensional quantitative coronary angiography systems

AIM

The in vivo comparison of the accuracy of two 3-dimensional quantitative coronary angiography (QCA) systems.

METHODS

Precision-drilled plexiglass phantoms with five different luminal diameters (0.5-1.9 mm) were percutaneously inserted into the coronary arteries of four Yorkshire pigs. Twenty-one angiographic images of these stenotic phantoms were acquired for in vivo validation testing. Quantitative assessments of the minimum, maximum, and mean luminal diameters together with the minimum luminal area were determined using two 3D QCA systems, the CardiOp-B and CAAS 5.

RESULTS

The CardiOp-B system significantly underestimated the minimum luminal diameter MLD whilst both systems significantly overestimated the maximum luminal diameter at the minimal luminal area (MLA) over the phantom's true value. The CAAS 5 system had a greater degree of accuracy/mm (mean difference = 0.01 vs. 0.03) and precision/mm (SD = 0.09 vs. 0.23) than the CardiOp-B in assessing the minimal LD. An increased precision/mm (SD = 0.01 vs. 0.29) and accuracy/mm (mean difference = 0.03 vs. 0.11) in the mean LD was observed with the CAAS 5. In comparing the MLA/mm(2) the CAAS 5 was more precise/mm(2) (SD = 0.14 vs. 0.55) and accurate/mm(2) (mean difference = 0.12 vs. 0.02) to the true phantom MLA compared to the CardiOp-B system.

CONCLUSIONS

In a 21 phantom study, the CAAS 5 3D QCA system had a greater degree of accuracy and precision in both the luminal and area measurements than the CardiOp-B 3D QCA system.

A randomised controlled study comparing conventional and magnetic guidewires in a two-dimensional branching tortuous phantom simulating angulated coronary vessels

OBJECTIVES

To directly compare the magnetic navigation system (MNS) guidewires with conventional guidewires in branching tortuous phantoms with operators of varying MNS and percutaneous coronary intervention experience.

BACKGROUND

Vessel tortuosity, angulation, and side branches remain limiting factors in coronary interventions. The MNS addresses these limitations by precisely directing the tip of a magnetised guidewire in vivo aided by two permanent adjustable external magnets.

METHODS

Crossing and fluoroscopy times of six operators were evaluated in five tortuous Perspex(R) phantom vessels in three consecutive attempts. Standard guidewire (SG) usage was unrestricted. Two 2nd generation magnetic guidewires (MG) were used. Failure was noted if the cross was unsuccessful within 5 min.

RESULTS

The magnetic navigation was vastly superior to SG techniques with increasingly tortuous phantoms. It dramatically decreased both the crossing and fluoroscopy times with maximal reduction from 201.7 +/- 111 to 36.4 +/- 13 sec, P < 0.001 and 204.7 +/- 24 to 47.2 +/- 19 sec, P < 0.001, respectively. The MNS had a 98.8% procedural success rate compared to 68% with SG techniques. Moreover it considerably limited the amount of wire usage from 5.5 to 1.3. Operators with prior MG experience performed significantly better than those without, except in the simplest phantom where the difference was nonsignificant (33.8 +/- 13 sec vs. 41.7 +/- 17 sec, P = 0.2).

CONCLUSION

MNS significantly reduces both the crossing and fluoroscopy times in tortuous coronary phantom models achieving excellent success rates with dramatic reductions in guidewire usage. Operators with prior MNS experience had an advantage over the inexperienced.

Magnetic navigation system used successfully to cross a crushed stent in a bifurcation that failed with conventional wires

Bifurcation lesions can be technically demanding to manage, and even in the era of drug eluting stents, their procedural success is variable. The use of the crush technique followed by "kissing" balloon postdilatation has been shown to improve the overall outcome. However, crossing the crushed stent is essential to allow performance of a final dilatation with "kissing" balloons and is regarded as the main Achilles' heel of this technique. In this report, we describe the first reported, planned procedure to use a magnetic navigation system to steer a wire through the crushed stent to use "kissing" balloons that had previously failed with conventional wires.