Angioplasty of lower limb arterial stenoses under ultrasound guidance: single-center experience.

PURPOSE: To examine the feasibility and utility of ultrasound-guided angioplasty for treating lower limb stenoses. METHODS: Duplex ultrasonography was employed to guide 55 balloon dilation procedures (27 iliac, 26 superficial femoral, 1 profunda, and 1 vein graft) with the help of a special ultrasound catheter (EchoMark). Ultrasound was used to determine balloon size, monitor guidewire passage, direct the dilation, and judge procedural success. Angiography was performed prior to the procedure to confirm preprocedural ultrasound findings and afterward to compare with duplex visual and hemodynamic parameters of success (peak systolic velocity ratio < 2.0). RESULTS: The balloon size determined from duplex measurements correlated in all cases with sizes selected based on the angiographic image. Guidewire visualization was possible in 95% of the cases. Angioplasty using ultrasound alone was feasible in 84%; inability to obtain a satisfactory image owing to vessel tortuosity, calcification, and bowel gas accounted for the failures. Against the duplex success criterion, initial completion angiograms had an accuracy of 76%, sensitivity of 76%, and specificity of 100%. The additional time for ultrasound guidance averaged 42 +/- 12 minutes for all cases. CONCLUSIONS: Our results show that ultrasound guidance is feasible in routine clinical practice. In this series of well-selected cases of arterial stenoses, angioplasty was performed safely using ultrasound guidance alone in over 80% of the cases. Fluoroscopic monitoring is needed when ultrasound visualization is suboptimal.

Duplex controlled angioplasty.

Duplex examination was carried out to assess lesions in peripheral arteries amenable to angioplasty. With the help of a special catheter, angioplasty of these lesions was performed under Duplex control. Sixteen patients presenting with claudication were examined by Duplex and 38 lesions were identified (31 stenoses, seven occlusions) and all the findings except one (vessel E1) were confirmed by subsequent angiography. Sixteen lesions were considered amenable to angioplasty and 13 lesions (in 10 patients) were selected for Duplex controlled angioplasty. A new catheter system which has a piezo-electric transducer at the centre of the balloon and integrated to a Duplex scanner via a catheter system interface, was used for the procedure. This allows the exact position of the balloon to be represented on the screen. Thirteen lesions (seven superficial femoral artery (SFA), three external iliac, two common iliac and one graft) were subjected to angioplasty under Duplex control. In one patient, the SFA was punctured directly under ultrasound control as the profunda was diseased. The guide wire was visualised in all cases and in the majority of cases, balloon size for the angioplasty was chosen by measurement of the arterial diameter by Duplex, which was also used for haemodynamic evaluation before, during and after the procedure. Eleven lesions (85%) underwent angioplasty entirely under Duplex control and additional X-ray control was needed in only two cases. In conclusion, Duplex allows the monitoring of both anatomical and haemodynamic parameters during angioplasty. It also reduces the risk of ionising radiation. Our initial experience has been encouraging as angioplasty was performed in the majority of lesions purely under Duplex control.

Transcutaneous ultrasonography can be used to guide and monitor balloon angioplasty.

PURPOSE: Percutaneous balloon angioplasty is an accepted technique for the treatment of short segmental stenoses of the iliac and superficial femoral arteries. Some surgeons have not embraced this technique because of lack of training, unfamiliarity with radiologic equipment, or poor-quality fluoroscopy equipment in the operating room. A new technique, ultrasound-directed balloon angioplasty, enables the vascular surgeon to guide the catheter and evaluate the progress of the procedure without the use of radiographic imaging. METHODS: The new catheter is integrated externally into a standard duplex scanner. A spherical brass bead positioned on the catheter shaft in the middle of the balloon is covered with a piezoelectric material. This omnidirectional receiver is connected through a wire to a catheter interface system, which allows the exact position of the balloon to be represented on the screen of a duplex unit. The catheter is advanced under visual control with use of the scanner. RESULTS: The system has been used to perform balloon angioplasty on 21 lesions (16 superficial femoral, 3 iliac, 2 popliteal arteries) in 17 patients. Procedures in 16 patients were performed percutaneously; in an additional patient bilateral angioplasties were performed during operation. The balloon was successfully positioned in each case with use of ultrasonography alone; each procedure was confirmed by use of angiography. Angioplasty was accomplished in 16 (76%) of 21 with the ultrasound-guided catheter alone. Supplemental use of a high-pressure balloon or atherectomy device was necessary in five patients. CONCLUSIONS: This technique records physiologic and anatomic data in real time so that the progress of the angioplasty can be monitored. In three patients the inadequacy of the initial angioplasty was recognized by a persistent velocity increase but not by angiography. As a result corrective measures were taken. This new procedure allows vascular surgeons to use equipment with which they are familiar, reduces the risk of ionizing radiation and contrast nephropathy, and permits the monitoring of the angioplasty with hemodynamic parameters.

Ultrasound Guided Balloon Angioplasty: What is its Role?

A modified angioplasty catheter has been developed which can be guided-into position with duplex ultrasound. This reduces the risks of ionizing radiation and contrast agents and uses a modality familiar to the vascular surgeon. This catheter was tested successfully in a canine model for safety, accuracy and therapeutic efficacy. Following FDA approval, clinical trials in humans were initiated. This paper describes the preliminary results with use of this device in humans.

Comparison of titanium-mesh and porous disc electrodes for epicardial defibrillation.

The object of this study was to compare the effectiveness of chronically implanted porous electrodes with that of smooth mesh titanium electrodes of the same diameter but smaller effective surface area. The criteria used in evaluating the electrodes were (1) acute, subacute, and chronic resistance and (2) acute, subacute, and chronic defibrillation thresholds. Electrode pairs 2.5 cm in diameter were implanted in each of 17 dogs (ten mesh and seven porous). One electrode of each pair was sutured to the right ventricle and one to the left ventricle near the cardiac apex. Defibrillation threshold energy and total resistance were measured at the time of implantation and again 6 and 12 weeks after implantation. The mean initial resistance of the titanium electrodes was 131.7 omega; the mean defibrillation values for the porous electrode implant were 96.9 omega and 7.5 joules, respectively. Three to 6 weeks after implantation, the values for the titanium mesh electrode were 88.9 omega and 12.0 joules, while those for the porous electrode were 59.9 omega and 8.0 joules. In the chronic state, the figures for the titanium mesh electrode were 78.1 omega and 13.0 joules, while those for the porous electrode were 64.3 omega and 8.3 joules. We conclude that defibrillation can be achieved successfully with small epicardial electrodes. The findings suggest that a porous electrode, with its larger effective surface area, has lower electrode/tissue interface resistance in the acute and chronic phases, and, therefore, provides lower defibrillation threshold energy.

Ultrasound-guided balloon angioplasty is a new technique for vascular surgeons.

A new catheter has been developed that can be accurately and precisely positioned using duplex ultrasonography alone. A piezoelectric transducer that functions as a passive, omnidirectional receiver is attached to the mid-balloon region of an angioplasty catheter. Integration to a standard duplex imaging system allows visualization of this receiver in all planes, with the location of the receiver represented by a flashing bright arrow superimposed on the ultrasound B-mode image. This catheter was tested successfully in 10 dogs with bilateral femoral arteriovenous fistulas. With the use of duplex guidance, eight arterial and three venous stenoses were dilated and two stents were placed. Catheter placements and therapeutic outcomes predicted by ultrasound correlated with arteriographic findings. Ultrasound guidance has several advantages. It eliminates the risks associated with radiographic imaging. It also reduces patient costs and discomfort. Furthermore, procedures can be monitored continuously in real time with the collection of anatomic and physiologic data.

A balloon-expandable intravascular stent for obliterating experimental aortic dissection.

Acute aortic dissection is a life-threatening condition. Aggressive hypotensive drug therapy is the initial treatment of choice, although emergent surgical intervention is often warranted. We evaluated the efficacy of a balloon-expandable intravascular stent for the internal obliteration of aortic dissection. It is a flexible, continuous, complex coil cut to the length needed at the time of insertion. It can be positioned in curved vessels, including the aortic arch. The stent was inserted in the thoracic and abdominal aorta of 12 dogs (group I). Six weeks after implantation the dogs underwent angiography and the stents were explanted for light and scanning electron microscopy. There were no instances of stent migration or change in configuration. The aortas did not rupture. All branch vessels remained patent. Light and scanning electron microscopy illustrated neointimal incorporation into the vascular wall except at orifices. Thoracic dissections were created surgically in an additional 24 mongrel dogs. Twelve dogs received stents immediately after creation of the dissection (group II). All 12 dissections were obliterated. Twelve dogs were allowed to recover after creation of the dissection to observe the natural history of that lesion (group III). Within 1 week, in group III, there were three deaths because of aortic rupture; eight dissections persisted, and one resealed spontaneously. Stents were placed in the eight persistent dissections. All eight dissections were obliterated. In both groups, after 6 weeks of stent placement, aortography was repeated, and stents were explanted for light and scanning electron microscopy. There were no instances of rupture. All branch vessels remained patent with no evidence of thrombosis. We conclude that because of its unique characteristics, the stent effectively obliterates the false lumen of experimental acute aortic dissections without occlusing side branches, damaging the aorta, or inducing thrombosis.

A polyester intravascular stent for maintaining luminal patency: a gross and microscopic study of the device's incorporation, early maturation, and thrombogenicity.

Over the past 3 years, we have developed a polyester mesh stent designed to preserve luminal patency in cases of dissecting aortic aneurysm and to maintain arterial patency after angioplasty. To study the stent's incorporation into the aortic wall and to test its thrombogenicity, we implanted the device in the abdominal aortas of ten dogs. The device was compressed and inserted into a 10-Fr sheath, which was introduced through the femoral artery into the aorta. Once liberated from the sheath and fully expanded within the aorta, the stent measured 10 cm in length and 8 mm in outer diameter. Each animal was followed up clinically until it was killed at intervals ranging from 1 week to 6 months after implantation. The aorta was excised, and tissue incorporation was evaluated grossly, as well as with light and scanning electron microscopy. In all cases, the arteries and side branches were found to be widely patent. At 3 weeks, the stent already had become firmly adherent to the vessel, owing to the ingrowth of fibrous tissue and endothelium through the mesh. The thrombus-free surface area, assessed planimetrically, was minimal during the early part of the study but rose to a plateau of 80% by the second month. Each specimen was subjected to indium-111 platelet scanning. The polyester mesh initially stimulated much platelet deposition, but this phenomenon decreased markedly over a 2-month period. In summary, our experience showed that an intraluminal polyester mesh stent could be inserted into the aorta via the retrograde arterial route and could effectively line the inner surface of the vessel. Within 2 months, healing was nearly complete and thrombogenicity was minimal.

An analysis of some sensitizing agents in the pathogenesis of stress-induced gastric erosive disease.

Prior surgical implantation of a venous catheter sensitized rats to cold-immobilization stress. Three of six catheterized females succumbed during the stress. The remaining rats fell into two groups in terms of their core temperature at the end of the stress period: Male uncatheterized rats had higher temperatures than rats in the other three groups. No relation was found between catheter patency and magnitude of hypothermia. Degree of gastric disease paralleled the core temperature findings in that the male uncatheterized rats had significantly fewer gastric erosions than the rats in the other three groups. Additionally, a robust effect of gender was found with uncatheterized females showing more hypothermia and more gastric disease than uncatheterized males. A subsequent experiment was conducted to evaluate whether anesthesia or wearing the protective spring was responsible in part for the sensitization seen. Here, the gender difference was less although females consistently averaged lower core temperatures after stress than did males. Despite similar core temperatures after stress, females that were prepared with the protective spring apparatus developed more gastric disease than female controls or similarly treated males. Thus, the additional sensitization exhibited by females in the first experiment may relate to the fact that both catheterization and the taping procedure were sensitizers while only catheterization was a sensitizer for males.