Radiofrequency thermal balloon coronary angioplasty: a new device for successful percutaneous transluminal coronary angioplasty

A New Conformal Penetrating Heating Strategy for Atherosclerotic Plaque

(1) Background: A combination of radiofrequency (RF) volumetric heating and convection cooling has been proposed to realize plaque ablation while protecting the endothelial layer. However, the depth of the plaque and the thickness of the endothelial layer vary in different atherosclerotic lesions. Current techniques cannot be used to achieve penetrating heating for atherosclerosis with two targets (the specified protection depth and the ablation depth). (2) Methods: A tissue-mimicking phantom heating experiment simulating atherosclerotic plaque ablation was conducted to investigate the effects of the control parameters, the target temperature (T_target), the cooling water temperature (T_f), and the cooling water velocity (V_f). To further quantitatively analyze and evaluate the ablation depth and the protection depth of the control parameters, a three-dimensional model was established. In addition, a conformal penetrating heating strategy was proposed based on the numerical results. (3) Results: It was found that T_target and T_f were factors that regulated the ablation results, and the temperatures of the plaques varied linearly with T_target or T_f. The simulation results showed that the ablation depth increased with the T_target while the protection depth decreased correspondently. This relationship reversed with the T_f. When the two parameters T_target and T_fwere controlled together, the ablation depth was 0.47 mm-1.43 mm and the protection depth was 0 mm-0.26 mm within 2 min of heating. (4) Conclusions: With the proposed control algorithm, the requirements of both the ablation depth and the endothelium protection depth can be met for most plaques through the simultaneous control of T_target and T_f.

Respiration and Heat Shock Protein After Short-Term Heating/Stretch-Fixing on Smooth Muscle Cells

PURPOSE

A treatment device without a stent is needed for peripheral stenotic artery treatment. We have proposed short-term heating balloon angioplasty, photo-thermo dynamic balloon angioplasty (PTDBA). Though smooth muscle cells (SMCs) after PTDBA are fixed in a stretched formation in a porcine model, influences of this stimulus on SMCs have not been investigated. SMC migration after vascular dilatation would be related to chronic restenosis. The aim of this study was to examine respiratory activity and recovery ability of SMCs after short-term heating/stretch-fixing in vitro for chronic phase treatment effect discussion.

METHODS

SMCs on a stretch chamber were heated for 15 s with stretching and fixed in a stretched formation. SMC migration is correlated with the cell respiratory activity. The amount of ATP production was measured using a WST-8 assay for respiratory activity evaluation. The intracellular expression of heat shock protein 70 was measured by an ELISA for recovery ability evaluation.

RESULTS

In the case of 60 °C heating, SMC respiratory activity after short-term heating/stretch-fixing decreased drastically in all stretching rates. In the case of 50 °C heating, SMC respiratory activity decreased and then increased. Alternatively, the recovery ability at 60 °C was greater than that at 50 °C.

CONCLUSIONS

SMCs heated at 60 °C with stretching would have high recovery ability and low respiratory activity related to SMC migration. These results may be important evidence in determining the treatment condition in PTDBA.

Mechanisms of Intravascular Linear Ablation Induced Restenosis in Rabbit Abdominal Aorta

Objectives

Percutaneous coronary intervention (PCI) is the mainstay treatment for coronary artery disease but complications such as in-stent restenosis and thrombosis remain problematic. Radiofrequency balloon angioplasty (RBA) can improve lumen dimension, fusing intimal tears, and artery dissection but is associated with higher restenosis rate.

Methods

After establishing an atherosclerosis model based on endothelial abrasion and high cholesterol diet, forty-five rabbits were randomly divided into three groups: RBA (n=20), percutaneous transluminal angioplasty (PTA) (n=20), and control groups (n=5). The RBA and PTA groups were subdivided according to harvested time posttreatment, respectively (1 hour, 7 days, 14 days, and 28 days). Aorta segments were then isolated for hematoxylin and eosin staining, Masson trichrome staining, immunohistochemistry, and Western blot for TLR-4, NF-κB, MCP-1, and VCAM-1expression.

Results

At 28 days, intimal area was significantly lower in the RBA group compared to the PTA and control groups, whilst luminal and medial area were comparable in the RBA and PTA group but higher and lower than the control group, respectively. Expression of TLR-4, NF-κB, MCP-1, and VCAM-1 showed no significant difference between RBA and PTA groups.

Conclusions

RBA can depress the intimal hyperplasia and promote dilatation of the artery to greater extents than PTA at 28 days. However, this did not involve TLR-4 signaling pathway, which likely plays a negligible role in mediating restenosis. Reduction of intimal hyperplasia may be due to injury of ablation to the tunica media and inhibition of VSMC proliferation and migration.

A new endovascular radiofrequency device for dilatation of vascular stenosis in a rabbit model

PURPOSE

To investigate the use of a new endovascular radiofrequency (RF) device, the Habib™ VesCoag™ Catheter, to induce vascular remodeling and dilatation of arterial stenosis in a rabbit model.

MATERIALS AND METHODS

RF was used to induce arterial stenosis in 10 rabbits and this was confirmed by angiography and color Doppler ultrasound. Two groups of five animals were then subjected to (1) balloon dilatation of the stenosis (intervention group), (2) no intervention (control group). Two rabbits from each group were sacrificed following the procedures to investigate vessel histopathology. At six weeks, the remaining six rabbits underwent follow-up angiogram and color Doppler ultrasound to assess vessel patency. They were then sacrificed and the vessels prepared for histopathological analysis. Three-dimensional images with confocal microscopy of the arterial lumen were also acquired.

RESULTS

In the intervention group, stenosis was reversed and patency confirmed by angiography and color Doppler ultrasound six weeks later in all surviving rabbits. Histopathology revealed degenerative changes of elastic fibers, focal losses of elastica lamella, disorganization of myocytes and extensive hyalinization of the tunica adventitia. Focal elastin changes of the arterial elastic lamella were also shown by three-dimensional confocal microscopy images.

CONCLUSION

We have developed a novel endovascular RF catheter that can be safely and effectively used to induce vascular remodeling and dilatation of arterial stenosis in an experimental rabbit model.

Radiofrequency thermoneurolysis for the treatment of Morton's neuroma

Pedal neuroma is a common disorder. The authors undertook a review of 32 feet in 29 patients with a symptomatic neuroma treated between January 2007 and January 2010 to evaluate the effectiveness of radiofrequency thermoneurolysis therapy in alleviating symptoms. Overall relief of symptoms was rated as complete by 24 (83%) patients, with 5 patients experiencing minimal to no relief. Two patients were lost to follow-up after 1 month, 2 patients opted for no further intervention, and 1 patient went to open resection of the neuroma. Average follow-up was 13 months and total recovery time was 2 days. Complications included 1 foot with cellulitis treated by a course of oral antibiotics. The results of this retrospective study indicate radiofrequency thermoneurolysis therapy is a safe, effective, and minimally invasive alternative treatment for symptomatic neuromas of the foot.

Reduction of arterial graft smooth muscle mass by moderate heat therapy

Radial artery (RA) graft spasm is a major cause of early graft failure in coronary artery bypass grafting surgeries. We explored the feasibility of thermal reduction of smooth muscle mass to attenuate vasoconstriction. Rat and rabbit femoral arteries were treated thermally in situ (45°C to 65°C; 0 s to 120 s) and then excised at various time points for histological and physiological study (pressure-diameter relationships). Human radial arteries were treated in vitro and studied in similar fashion. Weeks after thermal treatment, no overt indication was noted of vasospasm, thrombosis, or scarring in the arterial wall; however, this intervention led to a thermal dose-dependent reduction of vasoconstriction (to phenylephrine or potassium chloride) and to a conspicuous loss of smooth muscle. Pressure-diameter relationships showed no aneurismal dilation of these demuscularized arteries up to 200 mmHg. Qualitatively identical results were obtained in human radial arteries. Thermal ablation of RAs may provide a simple, safe, and effective solution to postsurgical vasospasm.

A 12-year long-term retrospective analysis of the use of radiofrequency nerve ablation for the treatment of neurogenic heel pain

The authors discuss their rationale for the use of radiofrequency nerve ablation (RFNA) in the treatment of chronic neurogenic heel pain. Patients treated for plantar fasciitis who fail to improve after conservative and/ or surgical treatment should be reevaluated for a coexistent nerve entrapment. The results of a retrospective study of 82 patients who have undergone RFNA are presented. The patients were followed at 5, 10, and 12 years after the procedure. An evaluation of medical records was performed as a means of inclusion in this study. A standardized telephone interview was then done, and subjectively scored responses of the patients were recorded and analyzed. Of the patients, 89% reported no recurrence of pain after 5, 10, and 12 years postoperatively. The procedure is relatively easy to perform and involves inserting a 22-gauge cannula with an electrode into the areas of pain. This is done under general anesthesia. It takes approximately 15 to 20 minutes per heel to perform, depending on how many sites of tenderness have been identified. The patient is discharged with a minimal bandage and returns to shoe gear immediately following the procedure. The success rate with RFNA appears to be quite high with fewer associated risks and less post-operative morbidity.

The laser driven short-term heating balloon catheter: Relation between the chronic neointimal hyperplasia formation and thermal damage to arterial smooth muscle cells

We proposed a novel laser-driven short-term heating angioplasty to realize restenosis-suppressive angioplasty for peripheral artery disease. In this study, we investigated the chronic intimal hyperplasia formation after the short-term heating dilatation in vivo, as well as the thermal damage calculation on arterial smooth muscle cells (SMCs). The prototype short-term heating balloon catheter with 5.0, 5.5, 6.0 mm φ in balloon diameter and 25 mm in balloon length were employed. The short-term heating dilatation was performed in porcine iliac arteries with dilatation conditions of 75°C (N=4) and 65°C (N=5) as peak balloon temperature, 18 ± 4s as heating duration, 3.5 atm as balloon dilatation pressure. Four weeks after the balloon dilatation, the balloon-dilated artery segments were extracted and were stained with HE and picrosirius red for histological observation. In the case of 75°C as the peak balloon temperature, neointimal hyperplasia formation was significantly reduced. In this case, the SMCs density in the artery media measured from the HE-stained specimen was 20% lower than that in the reference artery. According to the thermal damage calculation, it was estimated that the SMCs lethality in artery media after the short-term heating angioplasty was 20% in the case of 75°C as the peak balloon temperature. We demonstrated that the short-term heating dilatation reduced the number of SMCs in artery media. We think this SMCs reduction might contribute to the suppression of chronic neointimal hyperplasia.

Histological findings after angioplasty using conventional balloon, radiofrequency thermal balloon, and stent for experimental aortic coarctation

BACKGROUND

Use of balloon angioplasty or stent implantation has been reported to be effective in relieving coarctation of the aorta. However, restenosis frequently occurs after balloon angioplasty for native aortic coarctation in small infants, and sometimes develops after stent implantation because of vessel growth. The causes of restenosis remain uncertain. The purpose of this study was to assess the histologic differences in vascular responses to angioplasty using conventional balloon, radiofrequency thermal balloon (RFTB), or stent for experimental aortic coarctation.

METHODS

The authors surgically created an aortic coarctation model using 14 puppies. Angioplasty using conventional balloon, RFTB, or stent was performed 1 month after the initial operation. At the acute or chronic phase after angioplasty, the animals were killed and histologic studies were performed.

RESULTS

More vascular injuries were noted in the specimens from animals undergoing conventional angioplasty than in those with RFTB or stent. However, neointimal hyperplasia was seen more often after RFTB or stent because of the proliferation of smooth muscle cells from the tunica media, caused by secretion of growth factors. Apoptosis reached a peak 1-2 weeks after angioplasty, regardless of the type of intervention.

CONCLUSIONS

The authors conclude that angioplasty with RFTB or stent can provide relatively small injuries in the vessel wall for aortic coarctation, but care must be taken to prevent restenosis caused by intimal hyperplasia, because neointima hyperplasia is more frequent after RFTB or stent.

Usefulness of a new radiofrequency thermal balloon catheter for pulmonary vein isolation: a new device for treatment of atrial fibrillation

INTRODUCTION

A rapidly firing or triggered ectopic focus located within a pulmonary vein (PV) or close to the PV ostium could induce atrial fibrillation (AF). The aim of this study was to evaluate the efficacy and safety of a radiofrequency thermal balloon catheter for isolation of the PV from the left atrium (LA).

METHODS AND RESULTS

Twenty patients with drug-resistant paroxysmal AF were treated by isolating the superior PVs using an RF thermal balloon catheter. Using a transseptal approach, the balloon, which had an inflated diameter 5 to 10 mm larger than that of the PV ostium, was wedged at the LA-PV junction. It was heated by a very-high-frequency current (13.56 MHZ) applied to the coil electrode inside the balloon for 2 to 3 minutes, and the procedure was repeated up to four times. The balloon center temperature was maintained at 60 degrees to 75 degrees C by regulating generator output. Successful PV isolation was achieved in 19 of the 20 left superior PVs and in all 20 of the right superior PVs and was associated with a decrease in amplitude of the ostial potentials. Total procedure time was 1.8 +/- 0.5 hours, which included 22 +/- 7 minutes of fluoroscopy time. After a follow-up period of 8.1 +/- 0.8 months, 17 patients were free from AF, with 10 not taking any antiarrhythmic drugs and 7 taking the same antiarrhythmic agent as before ablation. Electron beam computed tomography revealed no complications, such as PV stenosis at ablation sites.

CONCLUSION

The PV and its ostial region can be safely and quickly isolated from the LA by circumferential ablation around the PV ostia using a radiofrequency thermal balloon catheter for treatment of AF.

A new radiofrequency thermal balloon catheter for pulmonary vein isolation

OBJECTIVES

We sought to evaluate whether porcine pulmonary vein (PV) isolation (PVI) can be produced by ablation using our novel radiofrequency (RF) thermal balloon catheter (RBC).

BACKGROUND

It has been proposed that PVI can prevent focal atrial fibrillation (AF) originating in or close to the PV.

METHODS

The RBC is composed of a 12F main shaft, a 4F inner tube and a balloon. Inside the balloon, there is a unipolar coil electrode with a thermocouple sensor mounted along the tube, the former to deliver RF energy (13.56 MHz) and the latter to monitor the temperature. After the presence of a PV potential was confirmed, the RBC was safely inserted into the left atrium (LA) by the trans-septal approach. Once the balloon was inflated and optimally wedged at the junction between the PV and LA, RF energy was applied for 5 min. Radiofrequency catheter ablation (RFA) was repeated up to three times, until elimination of the PV potential or dissociation between the LA and PV was observed. Finally, each heart was examined histologically.

RESULTS

In 18 PVs that had PV potentials, PVI was performed, resulting in success in 15 (success rate 83%, 95% confidence interval [CI] 58.0% to 96.3%; failure rate 17%, 95% CI 3.7% to 42.0%). After successful PVI, the PV potentials completely disappeared and the histologic examination revealed circumferential, transmural necrosis around the PV trunks. No major complications, such as PV stenosis or macroscopic thrombosis, were observed.

CONCLUSIONS

The RBC was useful for PVI.

Analysis of heat generation during rotational atherectomy using different operational techniques

Rotational atherectomy can generate heat from the friction of the burr as it ablates atherosclerotic plaque. The objective of this study is to correlate Rotablator technique and heat generation using two experimental models. First, 2.0 mm burrs were advanced through a lesion model derived from bovine bone implanted with thermal probes. Intermittent ablation with minimal decelerations resulted in a smaller temperature increase than continuous ablation with maximal decelerations (2.6 +/- 1.3 vs. 13.9 +/- 1.0 degrees C, respectively, P < 0.01). The second model used porcine femoral arteries cradled in constricting polyethylene grafts with thermal probes in contact with the adventitia. As the burr advanced through the segment, RPM decreases of 5-7 k resulted in a temperature rise of 4.1 +/- 1.2 degrees C, whereas decelerations of 10-20 k resulted in a 11.3 +/- 6.2 degrees C temperature increase. We conclude that excessive drops in speed and aggressive advancement of the burr are related to significant increases in temperature and potential thermal injury.

Abrupt vessel closure: changing importance, management, and consequences

Percutaneous coronary interventions have been performed for 20 years. Despite the success and progress of these interventions, abrupt vessel closure has been a dramatic adverse event of coronary interventions. Closure has frequently led to the major complications of death, myocardial infarction, and emergency coronary artery bypass. Because of the fear of this adverse event and its subsequent complications, the applicability of coronary interventions is sometimes limited. The pathologic characteristics of abrupt vessel closure have been recognized as predominantly caused by dissection, with vessel recoil and thrombus formation playing important secondary roles. The recognition of the lesions at risk for abrupt vessel closure has led to a strategy of lesion-specific device therapy to reduce complications. Similarly the role of antiplatelet and antithrombotic therapies have reduced complications. The earliest methods of dealing with abrupt closure was emergency coronary artery bypass surgery with significant rates of morbidity and mortality. With the advent of second-generation devices and techniques, particularly stents, the management of abrupt vessel closure has been simplified and alternatives to emergency coronary bypass are more available. This article will review the history and current status of the prevention and management of abrupt vessel closure and demonstrate that anticipation and management of this complication have been facilitated with reduction of subsequent complications and increased applicability of coronary interventions.

Early clinical results of the use of radiofrequency lesioning in the treatment of plantar fasciitis

In this paper the authors discuss plantar fascial heel pain, including its etiology and treatment. The results of a retrospective study using radiofrequency lesioning on plantar fascial heel pain are presented and discussed. Thirty-nine patients were treated with radiofrequency lesioning, and 92% of the patients experienced complete resolution of symptoms following the procedure.

A randomized comparison of combined ticlopidine and aspirin therapy versus aspirin therapy alone after successful intravascular ultrasound-guided stent implantation

BACKGROUND

Previous studies have shown that it is feasible to withhold anticoagulation after a successful intracoronary stent procedure with a low incidence of stent thrombosis. The importance of specific antiplatelet agents when stenting is performed without anticoagulation is unknown.

METHODS AND RESULTS

After successful intravascular ultrasound-guided stenting, 226 patients were randomly assigned to receive either aspirin therapy alone (n = 103) or a combination of ticlopidine and short-term aspirin therapy (n = 123). Primary angiographic and clinical end points were stent thrombosis, death, myocardial infarction, the need for postprocedure coronary artery bypass surgery or repeated angioplasty, and significant medication side effects requiring termination of the medication within the first month of a successful procedure. At 1 month, the rate of stent thrombosis was 2.9% in the aspirin only group and 0.8% in the ticlopidine-aspirin group (P = .2). Cumulative major clinical events after successful stenting occurred in 3.9% of the patients in the aspirin group and in 0.8% in the ticlopidine-aspirin group (P = .1). There were no medication side effects in the aspirin group; in the combined ticlopidine-aspirin group, medication side effects occurred in 3 patients (P = .2).

CONCLUSIONS

At 1 month, there was no difference in the incidence of stent thrombosis or other clinical end points between the two poststent antiplatelet regimens. However, the relatively small size of the study and the low incidence of thrombosis events may have contributed to the failure to detect differences in angiographic and clinical end points between the two groups.

Initial clinical experiences with rescue unipolar radiofrequency thermal balloon angioplasty after abrupt or threatened vessel closure complicating elective conventional balloon coronary angioplasty

OBJECTIVES

The purpose of this study was to evaluate the effectiveness of radiofrequency thermal balloon angioplasty and rescue procedure after abrupt or threatened vessel closure complicating elective percutaneous transluminal coronary angioplasty.

BACKGROUND

Coronary angioplasty is an established therapy for ischemic heart disease. However, abrupt closure after successful angioplasty remains a serious problem.

METHOD

We utilized a unipolar radiofrequency balloon in which a radiofrequency potential of 13.56 MHz was transmitted between the coil within the balloon and a plate electrode attached to the patient's body. The temperature within the balloon could be monitored through a thermistor within the balloon. From October 1991 through December 1993, 31 patients who had abrupt or threatened vessel closure during 1,005 consecutive elective coronary angioplasty procedures were randomly assigned to radiofrequency balloon angioplasty or to other procedures as rescue

RESULTS

Fifteen patients were assigned to radiofrequency balloon angioplasty (5 with abrupt vessel closure and 10 with threatened closure). The average balloon temperature and inflation time were 62 +/- 9 degrees C and 129 +/- 62 s, respectively. Percent diameter stenosis decreased from 87 +/- 14% to 36 +/- 25% (p < 0.01). The procedure was successful in 14 patients. The rate of restenosis was 67%, but the success rate of repeat conventional coronary angioplasty for restenosed lesions was 86%.

CONCLUSIONS

Radiofrequency balloon angioplasty is effective in the treatment of abrupt or threatened vessel closure complicating elective coronary angioplasty even though the procedure is associated with a relatively high rate of restenosis.

Cardiovascular applications of laser technology

Laser technology has been evaluated for the treatment of coronary artery disease, ventricular and supraventricular arrythmias, hypertrophic cardiomyopathy, and congenital heart disease. Developments in laser angioplasty, laser thrombolysis, transmyocardial laser revascularization, photochemotherapy, laser treatment of arrhythmias and/or laser diagnostics are directed at improving upon conventional non-laser approaches, and providing new therapeutic and diagnostic options. This review will summarize the current status of the multiple applications of laser technology for cardiovascular diagnosis and therapy.