Biomedical subjects
Publications and source records attributed to T J Fogarty.
The shear force gauge is a device that will allow surgeons to develop a sense for the amount of shear force exerted on the arterial endothelium during balloon embolectomy. As a teaching device, hopefully it will decrease the number of shear force related complications connected to the use of the balloon embolectomy catheter.
Arterial embolism is usually caused by cardiac disease, and atherosclerotic coronary vascular disease is the primary precursor. Other cardiac states, as well as several uncommon causes, are part of the etiologic spectrum. The earliest signs are pain, paresthesias, pallor, and pulselessness. Severe ischemia is indicated by paralysis, a late feature. Arterial embolism and acute thrombosis can be difficult to distinguish, and deep venous thrombosis may also be suspected in the differential diagnosis. To restore arterial flow, anticoagulation treatment with heparin (Lipo-Hepin, Liquaemin) is given and surgical embolectomy is performed. Heparin infusion is continued until the patient is ambulatory, and then warfarin sodium (Coumadin, Panwarfin) is given over the long term. Fibrinolysis has also been used to treat acute arterial occlusion. Complications of embolism must be carefully guarded against, and additional procedures are sometimes necessary.
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Percutaneous arterial embolectomy was performed following percutaneous transluminal angioplasty in three patients using Fogarty balloon embolectomy catheters. This technique is effective for the treatment of arterial embolism resulting from angioplasty in selected situations.
Our experience with 739 patients with lower extremity thromboembolism since the advent of the balloon catheter has led us to several important observations: As the etiology has shifted from rheumatic to atherosclerotic, we treat a more complex group of patients, one fourth of whom have severe, preexisting peripheral occlusive disease. Early diagnosis and treatment is essential to decrease the mortality and morbidity, which has ranged about 25% +/- 10%. Anticoagulation must be continued in the postoperative period, accepting wound hematomas as a fair "trade-off" to prevent recurrent embolus and distal thrombosis in areas inaccessible to the catheter. Postoperative use of heparin "buys time" to further assess marginal results of embolectomy allowing arteriography and careful planning of secondary operations to assure not only a viable but a functional limb. There is little mention in the literature to emphasize this approach, which we think is essential for long-term salvage. Early in the series, patients were treated with heparin or embolectomy alone. There were 161 secondary operations in 135 patients following embolectomy consisting of repeated thromboembolectomy, popliteal exploration, sympathectomy, bypass graft(s), angioplasty, and endarterectomy. Additionally, 44 patients had a direct attack correcting the cardiac source of their embolism. Our overall mortality (12%) and limb salvage (95%) shows marked improvement compared with earlier reports. Therefore, we recommend combined embolectomy and heparin as the primary choice of therapy.
The inability to successfully position angioplasty catheters and the occurrence of complications during angioplasty procedures can, in part, be related to the shear forces generated during catheter introduction. Shear forces are the axial contact forces that the catheter system exerts on the inner arterial surfaces during advancement. The shear forces exerted by three different catheter designs (coaxial dilator, coaxial balloon, and linear extrusion) were measured in normal and atherosclerotic arteries; in modeled stenoses of variable severity, length, and compliance; and in modeled vessel angulations. The results with modeled vessels show that the linear extrusion catheter reduces the level of shear forces, particularly in narrow, long, noncompliant stenoses and in tortuous vessels. The stenotic artery results also show that the linear extrusion catheter minimizes these forces in tight lesions. The relative differences in forces are explained by the mechanism of action for each catheter. The reported occurrences of technical difficulties, complications, and long-term patency rates are then interpreted on the basis of the relative differences in measured shear forces. The results of this study combined with preliminary clinical data indicate that linear extrusion should facilitate placement and reduce associated complications.
A new vascular clamp called the occluder pad is described. It has significant utility when used in a variety of anatomic sites in either normal or diseased vessels. It possesses suitable tractive and occlusive forces while minimizing the mechanical forces applied to the vessel walls.
New transluminal angioplasty catheters based upon the linear extrusion of the dilating element have been developed to facilitate placement of the dilating balloon within the arterial narrowing. In a multicenter study, the use of linear extrusion catheters has been shown to be safe and effective in adjunctive intraoperative peripheral dilatations. Physical measurements of the frictional forces exerted on the inner arterial surfaces during advancement of 3 angioplasty catheter designs show that the linear extrusion catheter consistently minimizes these forces. The use of a secondary guiding sheath in conjunction with a linear extrusion catheter provides additional directional capability. A secondary guiding sheath with a side port has recently been developed that allows access to difficult-to-cannulate vessels. The favorable results of the clinical studies and research data justify an ongoing evaluation of these concepts in percutaneous dilatation procedures and in intraoperative coronary procedures.
A new transluminal angioplasty catheter based on linear extrusion of the dilating element has been specifically designed and developed for the cardiac surgeon. This catheter facilitates placement of the dilating balloon within the arterial narrowing without the routine use of fluoroscopy in the operating room. Physical measurements of the frictional forces exerted on the inner arterial surfaces by three different angioplasty catheter designs during advancement show that the linear extrusion catheter consistently minimizes these forces. The linear extrusion catheters have now been used in over 64 coronary adjunctive intraoperative dilatations. The results of these clinical studies and our research data indicate that the linear extrusion balloon catheter is a safe and effective adjunct to primary coronary artery bypass procedures.
New coaxial balloon dilators with standard urologic tip configurations have been designed for use in urethral strictures. Balloon dilatation provides several advantages over conventional dilatation of strictures including improved access and decreased mucosal trauma due to a low silhouette, adjustability of diameter and rigidity, decreased instrumentation, and facilitation of intermittent self-dilation by the patient. The instruments were evaluated in 51 strictures (41 patients) as both a dilator and a calibrator. All catheters were located across the stricture easily (although two required filiform attachments). All clinical goals were achieved, and no complications were identified. Two patients were started on a program of intermittent self-dilation after internal urethrotomy with good results. It is our initial clinical impression that slow, gradual dilation of strictures is superior to rapid, abrupt dilation. This can only be practically achieved with balloon dilators.
This report attempts to establish the place of real-time B-mode carotid imaging in the diagnosis of carotid artery disease through an analysis of the results of 3 years of experience in three major noninvasive vascular laboratories. Over 7000 patients were studied noninvasively with real-time B-mode carotid imaging and oculoplethysmography (OPG). Angiographic comparisons of 1723 vessels form the basis of this study. All tests were interpreted by physicians who had no knowledge of the angiograms. Images and x-ray films were classified by diameter of stenosis: grade I (0% to 39%), grade II (40% to 69%), grade III (70% to 99%), and grade IV (total occlusion). The effect of the imaging experience was determined by dividing the study into two periods. The results of image quality vs. accuracy and of combining the anatomic study (scan) and physiologic study (OPG) were also evaluated. The overall data show a specificity of 87% (985 of 1139), a sensitivity for grade II disease of 72% (193 of 267), a sensitivity for grade III of 66% (133 of 201), and a sensitivity for grade IV of 64% (74 of 116). With experience each center showed improvement of the imaging technique in diagnosing grade III (p greater than 0.1: not significant) and grade IV disease (p less than 0.0002: highly significant), although there was no improvement in the specificity and sensitivity of grade II disease. All scan errors were analyzed. Most errors were interpretation errors (27%: 90 of 338), scan/arteriogram mismatches (23%: 79 of 338), or poor-quality scans secondary to existing disease (22%: 75 of 338). There was a direct correlation of scan quality and accuracy, with a 97% specificity for grade I scans of good to excellent quality. When the scan and OPG agreed, there were uniform predictive values for all grades (88% to 93%). Sixteen of 79 scan/arteriogram mismatch vessels were operated on, and the scan proved more reliable in 86%. Real-time B-mode carotid imaging is a reliable technique for defining the normal carotid artery and is becoming increasingly sensitive in identifying existing disease. Despite its limitations, its strong points make it a valuable clinical tool.
We quantitatively determined the relative contribution of various factors leading to arterial lumen enlargement during transluminal angioplasty. Mechanical tests were conducted on both normal and atherosclerotic artery necropsy specimens. In our range of dilating pressures (0-3.4 atm or 0-50 lb/in2), content extrusion of fluid from the plaque accounted for 6-12% of the overall lumen area increase, while compaction of the plaque accounted for only 1-1.5%. The majority of the increase, 86.8-93%, was due to plaque and arterial wall disruption. The mechanism of disruption began with shearing of the plaque from the underlying artery at relatively low dilating pressures and continued with longitudinal tearing and stretching of the arterial wall at higher pressures. Diseased arteries dilated significantly more than nondiseased arteries at dilating pressures greater than or equal to 1.36 atm or 20 lb/in2 (P less than .05). In the range of stenoses that were tested (10-50%), the mean dilating pressure required to increase the lumen cross-sectional area by 50% was approximately 1.5 atm or 22 lb/in2.
We report a quantitative determination of the relative contribution of various factors leading to arterial lumen enlargement during transluminal angioplasty. Mechanical tests were conducted on both normal and atherosclerotic artery necropsy specimens. In the range of dilating pressures tested (0 to 3.4 atm or 0 to 50 lb/in2), content extrusion of fluid from the plaque accounted for 6% to 12% of the overall lumen area increase, while compaction of the plaque accounted for only 1% to 1.5%. Most of the increase (86.8% to 93%) was due to plaque and arterial wall disruption. The mechanism of disruption involved shearing of the plaque from the underlying artery at relatively low dilating pressures, followed by longitudinal tearing in the arterial wall at higher pressures. Diseased arteries were observed to dilate significantly more than nondiseased arteries at dilating pressures greater than or equal to 1.36 atm or 20 lb/in2 (P less than 0.05). In the range of stenoses tested (10% to 50% based on diameter reduction), the mean dilating pressure required to increase the lumen cross-sectional area by 50% was approximately 1.5 atm or 22 lb/in2. Based on these studies, we conclude that balloon dilatation results arise mainly from plaque and arterial wall disruption.
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The clinical experience with twelve patients who underwent subclavian-carotid transposition for the subclavian steal syndrome is related. The technical details of the procedure as well as the satisfactory clinical results are described, and the characteristics making it out procedure of choice are summarized.
Of a series of 874 consecutive candidates for coronary artery bypass screened for cerebrovascular disease, 49 (5.6%) were found to have significant extracarnial lesions. Combined surgical management of both carotid and coronary artery lesions was then undertaken, using a planned approach based on clinical and angiographic criteria. Cerebrovascular reconstruction was undertaken prior to establishment of cardiopulmonary bypass, utilizing staged procedures in good-risk and simultaneous reconstruction in poor-risk candidates. Our experience indicates that combined surgical treatment of the patient with unilateral carotid obstruction and coronary disease is attended by no greater risk than that attached to coronary revascularization alone. The coronary bypass candidate with bilateral carotid artery disease represents a more advanced clinicopathological state whose treatment is attended by greater risk of operative morbidity and mortality.
A fifty-six year old female is presented with significant stenosis of both the celiac and superior mesenteric arteries at their origin. A simplified method of revascularizing both vessels utilizing a single length of saphenous vein with two anastomoses is described. Also, the rationale for revascularizing all significantly involved vessels is discussed.