Experimental angioplasty: lessons from the laboratory

Pathological Safety Assessment in Preclinical Neurothrombectomy Studies

The design, production, and preclinical testing of neurothrombectomy devices is in a burgeoning phase as the demand escalates for safe and reliable treatment options following neurovascular stroke. Currently, there is a paucity of published data describing the development of iatrogenic vascular lesions occurring secondary to neurothrombectomy procedures. In an effort to test new devices, demonstrate device safety, satisfy regulatory requirements, and develop an understanding of the potential for associated vascular pathology, investigators are establishing appropriate methodology in suitable animal models. Significant challenges exist in identifying a single animal species that can be consistently utilized in all phases of device development. These aforementioned challenges are underscored by the intricacies of neurovascular pathology, thrombovascular interactions, and vascular responses to injury.

Renovascular Hypertension

Hypertension constitutes a major health problem and the challenge is to identify patients having ‘surgically’ curable renal vascular disease among the majority with so-called essential hypertension. The best of unsatisfactory diagnostic tests are renography and plasma renin activity both before and during angiotensin II blockade. The necessity of better screening tests has increased because of the recent advances in surgical techniques and especially percutaneous transluminal renal angioplasty. The latter has definitely become the method of choice for correction of suspected hemodynamically significant artery stenoses whenever technically feasible. With improved angioplasty techniques the risk of treating renal artery stenosis without hemodynamic and clinical importance (so-called cosmetic repair) has increased. Unfortunately randomized trials including surgery versus angioplasty are not available. It should be kept in mind that only after correction of the stenosis is achieved and the blood pressure has become normal, can the diagnosis of renovascular hypertension be made with certainty.

A thromboembolic model for the efficacy and safety evaluation of combined mechanical and pharmacologic revascularization strategies

BACKGROUND AND PURPOSE

Recanalization strategies mediated by intra-arterial fibrinolytic therapy in combination with mechanical clot disruption may be a more effective treatment approach than either therapy used alone. There are few preclinical animal models to evaluate these strategies. Here we report on a model to simultaneously evaluate both of these treatment approaches.

METHODS

Allogeneic clot was injected through the 6 F guide catheter after creating >50% luminal stenosis of the common carotid arteries of New Zealand White rabbits. The stenosis was released after 1 h, allowing sufficient time for clot-vessel wall interaction. Occlusion was confirmed and each vessel was assigned to receive either balloon angioplasty alone, intra-arterial tissue plasminogen activator (tPA, Alteplase, Genentech, San Francisco, California, USA), tPA delivery through prototype balloon infusion wire (NIT Therapeutics, Pittsburgh, Pennsylvania, USA), partial stent deployment or partial stent deployment with locally delivered tPA. The negative control received no treatment.

RESULTS

In vivo revascularization Thrombolysis in Cerebral Infarction (TICI) score revealed that the balloon infusion wire achieved a stable and higher revascularization score of TICI 2B, with a lower dose of tPA in comparison with other treatment strategies. All treatment strategies resulted in endothelial denudation and exposure of the internal elastic lamina.

CONCLUSIONS

The proposed animal model permits reliable and consistent thromboembolic occlusion of the target vasculature and allows for an assessment of both pharmacologic and mechanical revascularization strategies for acute ischemic stroke.

Quantification of elastic recoil after balloon angioplasty in the iliac arteries

PURPOSE

Elastic recoil of the arterial wall has been shown to be responsible for a significant loss of luminal area after balloon angioplasty in the coronary arteries, but it has not been well studied in the peripheral arteries. Because elastic recoil depends on the presence of elastin in the arterial wall, and the amount of elastin varies by artery and proximity to the aorta, the importance of this response to angioplasty may be different in peripheral arteries. The purpose of this study is to document the degree of elastic recoil in the iliac arteries, and analyze variables that might influence the results.

MATERIALS AND METHODS

A series of 19 patients with 25 iliac artery stenoses underwent balloon angioplasty followed by placement of a Palmaz stent with the same-sized angioplasty balloon. The minimum luminal diameter of the lesion was measured before treatment, immediately after balloon angioplasty, and again after stent placement. The arterial diameter after stent placement was defined as the diameter of the inflated balloon. The degree of recoil was correlated with nine variables: patient age and sex, lesion location and length, lesion severity (as percent stenosis), the balloon:artery ratio, and three factors related to lesion morphology--complex versus simple, eccentric versus concentric, and calcified versus noncalcified.

RESULTS

Elastic recoil averaged 36% +/- 11% and ranged from 19% to 54% in this series of patients. The only variable that significantly influenced the degree of elastic recoil was the balloon:artery ratio (P =.039), which was directly related.

CONCLUSION

Elastic recoil is a significant limitation of balloon angioplasty in the iliac arteries. This study illustrates the importance of techniques that limit recoil, such as vascular stents, in angioplasty of the iliac arteries.

Delayed improvement in carotid artery diameter after carotid angioplasty

BACKGROUND AND PURPOSE

Carotid percutaneous transluminal angioplasty (PTA) is a new method of treating carotid artery stenosis. There has been concern about restenosis after carotid PTA. This study was performed to ascertain the change in percent stenosis 1 year after carotid PTA.

METHODS

Twelve patients with symptomatic carotid stenosis were treated by PTA, and the anatomic result was studied by digital subtraction angiography at 1 year, supplemented by duplex ultrasound examinations at 1 month and 6 months.

RESULTS

The mean severity of stenosis treated, measured by the common carotid method, was 82% (range, 69% to 98%). The immediate result of PTA was a reduction in the severity of stenosis in all patients to a mean of 51% (P<.005). Six of the 12 patients showed a further improvement in lumen diameter of > or = 14% at 1-year angiographic follow-up from a mean stenosis of 47% (range, 24% to 76%) immediately after PTA to 28% (range, 0% to 52%) at 1 year. This indicates an active process of remodeling in response to carotid PTA. PTA initially reduced the stenosis by > or = 20% in 9 of the 12 arteries, and 8 of these remodeled or remained largely unchanged compared with only 1 of the 3 with a suboptimal initial dilation. In 3 patients the lumen diameter improved by < 5%. Three other patients restenosed with an increase in stenosis after PTA of 9%, 16%, and 66% at 1 year, but all were asymptomatic. The duplex findings showed that remodeling occurred at variable times between PTA and 1 year.

CONCLUSIONS

Remodeling of the carotid artery after PTA has not been described before. Our results confirm that carotid angioplasty has an acceptable patency rate at 1 year. It has been suggested that endovascular treatment of carotid stenosis should include placement of a stent. Our results indicate that this may not be necessary unless the initial PTA result is a reduction in stenosis of < 20%.

Luminal changes in downsteam arteries after percutaneous interventions in iliac arteries: implications for balloon or stent size determination

PURPOSE

To evaluate changes in the diameter of downstream iliac arteries after percutaneous interventions, which may be important for stent or balloon size determination.

PATIENTS AND METHODS

Angiographic studies were reviewed respectively for 31 patients in whom a unilateral common iliac artery occlusion (n = 10) or a high-grade stenosis (> 75%; n = 21) was treated with stent implantation (26 patients) or balloon angioplasty (five patients).

RESULTS

Before intervention, the ipsilateral downstream arteries showed a luminal reduction in 26 of 31 patients (mean 24% +/- 11.0; range, 6%-64%) compared with the opposite artery. This side-to-side difference was statistically significant for the external iliac artery (P = .000007) and for the common iliac artery distal to the obstruction (P = .017). In 17 of 26 patients, the side-to-side difference of the downstream external iliac artery was fully reversible immediately after intervention. In five patients, a luminal widening was noted. No change was seen in only four patients.

CONCLUSION

Because downstream arteries often show a marked luminal widening after intervention, determination of balloon or stent size cannot be based solely on the diameter of downstream ("normal") ipsilateral artery before intervention.

Influence of angiographic morphology on the acute and longer-term outcome of percutaneous transluminal angioplasty in patients with aortic stenosis due to nonspecific aortitis

PURPOSE

We studied the relationship of initial angiographic morphology in patients with aortic stenosis due to nonspecific aortitis and its relationship to immediate and later outcome following percutaneous transluminal angioplasty (PTA).

METHODS

Correlation was performed in 10 successive patients by retrospective analysis. All had clinically inactive nonspecific aortitis and hemodynamically significant aortic stenosis resulting in hypertension or lower limb claudication. Five patients had discrete concentric stenosis; the other five had eccentric stenosis with diseased aortic segments adjacent to the stenosis.

RESULTS

The five patients with concentric stenosis (Group I) had primarily successful and uncomplicated PTA with sustained improvement. The five patients (Group II) with eccentric stenosis had initial success in three patients and two initial treatment failures with one patient showing late improvement. Four of these patients developed large intimal flaps. One of these had an aneurysm during follow-up. Follow-up angiograms in five patients showed remodelling with further angiographic and clinical improvement.

CONCLUSION

Eccentricity of the stenosis and diffuse aortic disease correlate unfavorably with immediate outcome of PTA but late improvement may still be seen.

Balloon angioplasty results in increased segmental coronary distensibility: a likely mechanism of percutaneous transluminal coronary angioplasty

OBJECTIVES

The purpose of this study was to evaluate the hypothesis that the increase in lumen area induced by percutaneous transluminal coronary angioplasty is secondary to a change in lesion (segmental) distensibility.

BACKGROUND

Despite the widespread use of coronary angioplasty, the precise mechanism (or mechanisms) of lumen area improvement remains poorly understood.

METHODS

Quantitative coronary angiography was used to measure the minimal (contrast agent filled) balloon diameters at 1 to 5 atm, inclusive, during the first and final balloon inflations in 24 lesions successfully treated with coronary angioplasty. To rule out possible confounding effects due to changes in balloon material distensibility during repeated inflations, five control balloons were studied ex vivo. In parallel, intravascular ultrasound imaging was utilized to compare the segmental distensibility (change in lumen area during the cardiac cycle) of eight disease-free and seven mildly diseased coronary segments and seven segments after successful balloon angioplasty.

RESULTS

Minimal balloon diameters increased significantly between the first and final inflations (46%, 33%, 26%, 14% and 10% at 1, 2, 3, 4 and 5 atm, respectively, all p < 0.0001), demonstrating an increase in arterial distensibility after successful coronary angioplasty. No significant changes in balloon diameters were observed during sequential initial inflations at 1 and 2 atm (n = 5). Minimal increases in balloon diameters were observed during repeated balloon inflations in the ex vivo studies (4.9 +/- 1% [mean +/- SEM]). A distensibility index, derived from the intravascular ultrasound data, was not different between the balloon-dilated and the normal segments but was significantly lower in mildly diseased sites (14.7 +/- 2.2 vs. 12.9 +/- 1.2 vs. 6.9 +/- 1.9, respectively, p < 0.05) despite a smaller plaque area (7.3 +/- 1 vs. 11.3 +/- 1 mm2, proximal/nondilated vs. dilated segments, respectively, p < 0.05).

CONCLUSIONS

Coronary distensibility is significantly impaired in atherosclerotically diseased coronary segments and increases significantly after balloon angioplasty. This increase in segmental coronary compliance after coronary angioplasty may create a larger lumen area by allowing the vessel to distend in response to normal intraarterial pressure.

Reduction of vasoreactivity and thrombogenicity with laser-thermal angioplasty: comparison with balloon angioplasty

The vasoreactivity and thrombogenicity of laser-thermal angioplasty were examined and compared with those of balloon angioplasty in an atherosclerotic rabbit iliac artery. Eight rabbits underwent laser-thermal angioplasty with a 1.7-mm hot-tip probe activated at 7 W with a probe temperature of 126 +/- 19 degrees C in one iliac artery. The other iliac artery was treated with balloon angioplasty using a 2.0-mm balloon. Angiographic luminal diameter increased from 0.19 +/- 0.15 to 1.54 +/- 0.35 mm by laser and from 0.29 +/- 0.22 to 1.84 +/- 0.20 mm by balloon (P less than 0.0001, respectively). However, it decreased to 1.34 +/- 0.42 for laser and 0.45 +/- 0.39 for balloon 60 minutes later (P less than 0.0001 vs immediately post). Both iliac arteries were visualized using angioscopy, which revealed thrombotic obstruction of 91% stenosis in the ballooned artery and 8% stenosis in the lased artery. Vasoreactivity of treated vessels was also investigated. Segments 3-mm long were obtained from either treated artery or control artery and examined for noradrenaline (10 -7 M) contraction. The segments were then mounted isometrically with 1 g tension in Krebs-bicarbonate buffer. Developed tension was 0.13 +/- 0.21 g for laser thermal and 2.33 +/- 0.4 g for its control (P less than 0.0001), and 0.15 +/- 0.16 g for balloon dilatation and 2.12 +/- 0.43 g for its control (P less than 0.0001). Neither acetylcholine at 10 -6 M or papaverine at 10 -4 M induced relaxation of treated segments. Histology showed slight thermal injury at thermally-treated sites without thrombus, and intimal and medial dissection with thrombus formation at balloon dilated site.

IN CONCLUSION

(1) neither a laser-thermal recanalized or a balloon dilated obstructed artery is vasoreactive to constrictive or relaxant agents; and (2) laser-thermal angioplasty results in less thrombogenicity than balloon angioplasty under moderate probe temperature.

Arterial responses to balloon coronary angioplasty: an intravascular ultrasound study

OBJECTIVES

The purpose of this study was to examine the coronary artery response to percutaneous transluminal coronary angioplasty by using intravascular ultrasound.

BACKGROUND

The immediate effects of coronary angioplasty on arterial wall geometry and surface appearance are understood poorly. Most of the available data are derived from small necropsy series, inferred from animal models or extrapolated from in vitro studies. High frequency intravascular ultrasound provides transmural images of coronary arteries in vivo.

METHODS

We used intravascular ultrasound to study 29 patients before or after, or both, successful coronary angioplasty.

RESULTS

The angiographic diameter narrowing was 72 +/- 13% before and improved to 19 +/- 11% after angioplasty. Calcium was visualized in 7 (24%) of the 29 angioplasty sites by fluoroscopy versus 15 (52%) of sites by intravascular ultrasound (p = 0.022). Arterial dissection after angioplasty was observed in 8 (27%) of cases by contrast angiography versus 24 (83%) by intravascular ultrasound (p less than 0.001). Intravascular ultrasound detected extensive dissection at the angioplasty site in 11 (73%) of the 15 calcified plaques and in only 3 (21%) of the 14 noncalcified plaques (p = 0.024). Arterial expansion (defined as the area within the external elastic membrane at the angioplasty site greater than that of the proximal reference segment) occurred in 29% of calcified plaques compared with 86% of noncalcified plaques (p = 0.007).

CONCLUSIONS

Intravascular ultrasound is more sensitive than angiography for identifying arterial calcium and dissection at the site of angioplasty. At the site of angioplasty, arterial dissection occurred more frequently in calcified plaques whereas arterial expansion occurred more frequently in noncalcified plaques. Successful angioplasty causes a continuum of arterial responses that vary importantly with plaque composition.

Plaque morphology and pathologic changes in arteries from patients dying after coronary balloon angioplasty

Morphologic correlates of pathologic success or failure were studied at autopsy in 28 patients with 40 coronary arteries that had been subjected to balloon angioplasty. The presence of the following histologic features was evaluated: plaque concentricity or eccentricity, calcification, fibrous or fibropultaceous plaque, medial disruption, luminal thrombus and inflammation. Angioplasty was considered successful (residual cross-sectional luminal area greater than 25%) on pathologic examination in 14 arteries and unsuccessful in 26 arteries. Eccentric plaques were more likely to be successfully dilated than were concentric lesions (p less than 0.05). Six (50%) of 12 fibropultaceous plaques were successfully dilated compared with only 8 (29%) of 28 fibrous plaques. Moderate to severe calcification did not preclude morphologic success. Medial stretching or dissection, or both, was more often associated with a successful result. Thus, plaque morphology may be an important determinant of pathologic outcome after coronary angioplasty.

Does percutaneous transluminal coronary angioplasty accelerate atherosclerotic lesions?

Recent reports have suggested that angioplasty may cause or accelerate coronary arterial stenoses secondary to traumatic injury. Ninety-four coronary angiograms performed in a 1 yr period were reviewed in patients who had successful coronary angioplasty 6 to 30 mo (mean 10.7) prior to restudy. Restenosis was found in 43 of 140 dilated lesions (31%) and in 41 of 94 patients (44%). Thirty-three (35%) patients had new or progressive lesions outside the angioplasty site. New or progressive lesions occurred with similar frequency in the arteries that did not have angioplasty (23/155 = 15%) as in the arteries that did (13/127 = 10%; chi-square n.s.). In the arteries which underwent angioplasty, new or progressive lesions occurred as commonly proximal to the PTCA site (7/14, 50%) as distal (6/13, 46%). New or progressive lesions occurred in 29% of patients with concomitant restenosis, and 40% of those without restenosis (chi-square n.s.). No clinical, angiographic, or procedural factors distinguished patients with new and progressive lesions in target vessels from those without these lesions in target vessels. Patients with progressive lesions anywhere in the coronary tree were more likely to have had a shorter duration of anginal symptoms before angioplasty and a family history of coronary disease when compared with patients without progressive atherosclerosis. In conclusion, new and progressive lesions outside the angioplasty site occur after the procedure but appear unrelated to the restenosis process or traumatic injury by angioplasty instrumentation.

Surgical treatment for isolated dissection of the renal artery

From 1974 to 1989, 18 patients underwent surgical treatment for isolated dissection of the renal artery causing high grade stenosis, including 2 patients with bilateral renal involvement. The causes of renal artery dissection were blunt trauma (1 patient), unsuccessful percutaneous transluminal angioplasty (5) and atherosclerosis (5) or intimal fibroplasia (7) of the renal artery. The most common presenting signs or symptoms of a dissection were hypertension (94%), an abdominal bruit (44%), headache (44%), minimal proteinuria (44%), microscopic hematuria (38%) and flank pain (38%). Renal artery dissection led to segmental or total renal infarction in 8 of 20 involved kidneys (40%). Seventeen patients underwent unilateral surgical revascularization with amelioration of hypertension and preservation of renal function. Three kidneys were lost due to irreversible ischemic damage from an occlusive dissection. Isolated renal artery dissection is an uncommon lesion that can cause hypertension and threaten renal function.

Feasibility of percutaneous transluminal angioplasty for carotid artery stenosis

Percutaneous transluminal balloon angioplasty was attempted in seven patients with internal carotid artery stenosis, including one patient who had two procedures. All had recurrent, carotid territory, neurological symptoms considered haemodynamic in origin. Six had occlusion of the contralateral internal carotid artery. Cerebral blood flow studies confirmed diminished cerebrovascular reserve in six patients studied. In five patients (six procedures) angioplasty of the stenosed internal carotid artery was carried out successfully. With two patients technical difficulty in crossing the stenosis prevented angioplasty and in one patient with bilateral stenosis the procedure was not attempted on the second side because of the severity of the stenosis. In two patients transient aphasia developed during cannulation of the carotid artery and in another a transient monoparesis developed during the procedure. Both these haemodynamic complications recovered within ten minutes. No other complications occurred. Our experience suggests that balloon angioplasty is technically feasible in the management of stenotic carotid disease associated with haemodynamic stroke. It is a technically simple procedure requiring only a brief admission to hospital. However, its general application to patients with thromboembolic carotid-territory stroke will depend on the risk/benefit ratio compared to carotid endarterectomy or to conventional medical treatment.

Influence of transluminal angioplasty on the prostanoid release from the arterial wall

Vasospasm and thrombosis complicate percutaneous transluminal angioplasty (PTA). To study if the release of the prostanoids PGI2 and TxA2 are affected by PTA, the following experiment was undertaken: In ten rabbits, the upper or lower half of the aorta was randomised either to transluminal angioplasty or control segment. After excision the segments were simultaneously but separately perfused ex vivo with Hank's balanced salt solution for five consecutive 15 min periods. Arachidonic acid was added to the perfusate for the last 15 min period. PGI2 and TxA2 were measured by radioimmunoassay in the perfusate as the stable degradation products 6-keto-PGF1 alpha and TxB2. After perfusion, the two aortic segments were prepared for scanning electron microscopy (SEM). Angioplasty decreased the basic release of PGI2 as well as the response to arachidonic acid. This is likely to be due to endothelial denudation as seen by SEM. The release of TxA2 from the vessel wall was very low and was not increased by dilatation. The influence of angioplasty on the prostanoid system may be of importance in the complications of vasospasm and thrombosis.

Effect of platelet inhibitors on platelet and fibrin deposition following transluminal angioplasty of the atherosclerotic rabbit aorta

Experimental atherosclerosis was induced in a rabbit model by intimal damage of the infrarenal aorta followed by two months cholesterol feeding. The influence of four different antiplatelet drug regimens on acute platelet and fibrin deposition after transluminal angioplasty of the atherosclerotic abdominal aorta was then evaluated. The study group consisted of 32 New Zealand rabbits: 7 controls, 7 treated with prostacyclin (10 mg/kg/min i.v.), 5 treated with low-dose acetylsalicylic acid (2 mg/kg i.v.), 7 treated with acetyl-salicylic acid (5 mg/kg i.v.) and dipyridamole (2 mg/kg i.v.), and 6 treated with low molecular dextran (5 ml/kg). By 2 hours after angioplasty, there was a significant increase of the deposition of platelets (P less than 0.001) as well as fibrin (P less than 0.01) when comparing dilated to non-dilated segments in the control animals. There was no significant difference in the amount of platelets and fibrin deposition among the control and drug treated groups. Thus, in this animal model there appears to be no immediate benefit in using antiplatelet drugs during transluminal angioplasty. Although, this study did not address the potential long-term effects of antiplatelet drug therapy, future evaluation of the clinical benefits of these drugs in conjunction with transluminal angioplasty seems warranted.

Percutaneous atherectomy--early experience in Sheffield

Percutaneous transluminal angioplasty (PTA) of arterial stenoses is a well-established and relatively safe technique in the treatment of peripheral and coronary vascular disease. Recurrence, however, remains a problem. The 'atherectomy' catheter is a new device to provide lumen enlargement by the mechanical removal of atheroma. In Sheffield, 14 lesions in the femoral arteries have been treated by atherectomy, with a reduction in mean diameter stenosis from 88% to 15%. There were no complications. Follow-up ranges from 3 to 15 months, with a mean of 9 months. There has been only one recurrence. It can be used in calcified lesions and may prove to be most useful in the treatment of tough lesions. Further experience and follow-up is necessary, however, to determine whether it has any advantage over balloon dilatation.

Vessel, plaque, and lumen morphology after transluminal balloon angioplasty. Quantitative study in distended human arteries

We performed transluminal balloon angioplasty in 24 cadaver and nine amputated limb superficial femoral arteries under controlled experimental conditions. The cadaver arteries were excised, restored to in situ length, redistended, and maintained at 100 mm Hg intraluminal pressure at 37 degrees C throughout the angiographic and dilation procedure and during fixation. The amputated limb arteries were dilated and pressure perfusion-fixed after dilation. Quantitative analysis of cadaver vessels revealed that arteries with prominent atherosclerotic lesions had the same internal elastic lamina (IEL) circumference (15.6 +/- 1.0 mm) as those with little or no stenosis (16.8 +/- 0.5 mm) but lumen area (8.8 +/- 1.7 mm2) was markedly reduced compared to nonstenotic sites (20.0 +/- 1.9 mm2, p less than 0.01). Lesions occupied 49 +/- 6% of the area circumscribed by the IEL in cadaver arteries with prominent plaques. After dilatation, lumen areas at stenotic sites were enlarged 43% on histologic sections (12.6 +/- 1.8 mm2 vs 8.8 +/- 1.7 mm2, p less than 0.01) and 31% as determined by angiography (p less than 0.05) when compared to immediately adjacent nondilated regions. The increased lumen area was associated with splitting of the intima near the edges of the plaque, separation of the edges of the plaque from the media, and stretching of the media and adventitia, often with accompanying rupture of the media. There was no evidence of plaque compression, fragmentation, deformation, modeling, or herniation into the media. The detached wedge-shaped edges of the lesions formed flaps projecting into the lumen, resulting in a marked increase in lumen irregularity on cross-section.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphology of the coronary arteries after combined thrombolysis and percutaneous transluminal coronary angioplasty for acute myocardial infarction

Autopsy findings are reported for 6 patients who died early (8, 9, 12, 13 and 14 days) or late (52 days) after combined thrombolysis and percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction. Morphologic changes in the coronary arteries at the site of revascularization included injury to the inner portion of the arterial wall (intimal splitting, subintimal dissection, medial tears and submedial dissection) and necrosis of medial smooth muscle cells. Residual mural thrombi and thrombotic reocclusion were noted within the arterial lumen. There was a beginning neointima formation in all patients who died early and a reobstructing neointima proliferation in the patient who died late after PTCA. The results of this study support the suggestion that both rupture and dissection of the inner arterial wall and necrosis of the tunica media resulting from irreversible dilatation of the grossly intact outer layers are the most important mechanisms of PTCA. Response to arterial wall injury after PTCA is a neointima formation leading to covering of mural thrombi and thrombogenic intimal, medial and adventitial substances and smoothing of the luminal surface. Large residual mural thrombi and excessive neointimal proliferation may cause restenosis within a few weeks.

Intimal dissection following percutaneous transluminal carotid angioplasty for fibromuscular dysplasia

Fibromuscular dysplasia (FMD) is an unusual form of segmental arteriopathy and may affect the internal carotid artery (ICA). We report a case of carotid FMD in which percutaneous transluminal angioplasty (PTA) was complicated by an intimal tear and required surgical exploration. PTA is a useful form of treatment, but there is a risk of intimal dissection. If this occurs, it may be necessary to excise the intimal flap surgically.

Effect of antiplatelet therapy on restenosis after experimental angioplasty

Restenosis is recognized as a common complication of PTCA and can limit the long-term benefit of this procedure. To study the effect of antiplatelet agents in preventing restenosis, 25 New Zealand rabbits had bilateral iliac stenoses created by balloon deendothelialization and a 2% cholesterol diet for 6 weeks. After angiographic delineation of the iliac atherosclerosis, successful angioplasty was performed in all rabbits, with an average increase in luminal diameter of 0.9 mm (81%). Seven rabbits received aspirin (32 mg/day) plus dipyridamole (25 mg/day) and 9 received sulfinpyrazone (100 mg/day); 9 were given no antiplatelet drugs and served as controls. After 4 weeks of drug therapy and a continued atherogenic diet, angiography was repeated and the rabbits were killed for histologic examination. The angiographic luminal diameter was similar for these groups both before and immediately after angioplasty. However, the luminal diameter 4 weeks later was significantly larger in both the aspirin plus dipyridamole and the sulfinpyrazone groups compared with the control rabbits (1.3 +/- 0.6 and 1.8 +/- 0.5 mm vs 0.7 +/- 0.6 mm, respectively, p less than 0.05). Histologic examination revealed intraluminal clot in 4 of 9 control rabbits and in none of the drug-treated rabbits. Also, less intimal thickening was evident. In conclusion, aspirin plus dipyridamole and sulfinpyrazone inhibited angiographic restenosis after transluminal angioplasty in this experimental model. These findings support the use of antiplatelet agents in clinical angioplasty and suggest that platelet aggregation at the angioplasty site may promote restenosis.

Potential mechanisms of angioplasty

There are at least five potential mechanisms for enlarging the arterial lumen using the technique of percutaneous transluminal angioplasty. Each of these mechanisms is reviewed along with evidence from clinical or experimental angioplasty supporting or refuting an actual role for that mechanism in mechanical dilation of diseased vessels. Although plaque compaction is not plausible, each of the other four responses--redistributive modeling of plaque, embolization of plaque components, plastic stretching of the arterial wall, and phagocytic removal of plaque during healing after angioplasty--has been confirmed in at least some circumstances. Since the lesions probably differ in their biomechanical properties, we conclude that it is unlikely that a single mechanism will explain all of the successful dilations.

Percutaneous transluminal angioplasty for lower limb ischaemia

Forty successful percutaneous transluminal angioplasties (PTA) were performed in the iliac and femoropopliteal segments of 33 patients with lower limb ischaemia. There was immediate symptomatic relief in 37 limbs (92 per cent) although 7 relapsed and 5 patients required reconstructive arterial surgery within a month of PTA. Objective testing showed that the longer term relapse rate (median follow-up 12 months) was low (10 per cent). Despite a significant incidence of early complications and relapse, PTA provided a good long term result in the majority of patients treated.

Effects of percutaneous transluminal angioplasty on renal plasma flow

Percutaneous transluminal angioplasty is being used with increasing frequency for the treatment of renal artery stenosis. Several noninvasive techniques that utilize radioactive tracers have been used for monitoring the effects of angioplasty and progression of disease. Forty-one patients were studied before and after renal angioplasty by using renograms and fractionated measurements of effect renal plasma flow. Although there were striking examples of improvement in effective renal plasma flow following angioplasty, this was not a consistent finding. There was a tendency for effective renal plasma flow to revert to the baseline level on follow-up studies. Cure of hypertension was more likely in patients without renal insufficiency and in patients with shorter periods of sustained hypertension. Fractionated effective renal plasma flow studies did not reliably differentiate patients who were cured from those who were improved nor were we able to delineate clearly those requiring repeat dilatation. Nevertheless, this technique is useful for noninvasively measuring fractionated renal function in the immediate postoperative or postdilatation recovery period and for detecting the difference between occlusion of the renal artery and transient renal insufficiency due to contrast material. Also, long-term measurement of fractionated function has value in following potential progression of the basic disease process.

Percutaneous transluminal carotid angioplasty in fibromuscular dysplasia. Case report

A patient with fibromuscular dysplasia (FMD) of the internal carotid artery was treated by balloon percutaneous transluminal angioplasty (PTA). This is the sixth reported case of FMD stenotic disease which was dilated by PTA. All previous cases including the current example were treated successfully with resolution of symptoms. This procedure is associated with a relatively low morbidity and is an alternative method of treatment to operative endarterectomy for this disorder.

Transluminal coronary angioplasty and early restenosis. Fibrocellular occlusion after wall laceration

Transluminal coronary angioplasty was performed in a 51 year old man with a localised narrowing of the proximal segment of the left anterior descending coronary artery. Initial inflations with a small size balloon catheter were unsuccessful. A second attempt, during the same procedure, using a larger calibre catheter relieved the obstruction but produced a dissection. Angina pectoris reappeared approximately three months later. Another attempt to relieve the obstruction by angioplasty, five months after the initial procedure, induced ST segment elevation before angioplasty, followed by ventricular fibrillation and death. The necropsy showed a split in the pre-existent sclerotic plaque and a dissecting aneurysm of the media. A proliferation of fibrocellular tissue filled the false channel and almost totally occluded the pre-existent arterial lumen. The observation suggests that wall laceration with exposure of smooth muscle cells to blood may have initiated the excessive fibrocellular tissue response. This event may be the underlying pathogenetic mechanism for the occurrence of early restenosis after transluminal coronary angioplasty.

Angiographic changes produced by percutaneous transluminal coronary angioplasty

Percutaneous transluminal coronary angioplasty (PTCA) is being used with increasing frequency in the treatment of patients with symptomatic coronary artery disease. Balloon inflation results in diverse angiographic findings, reflecting the great variety of anatomic and pathologic changes produced. The long-term effects of inflation on the underlying atherosclerotic lesion and the clinical outcome are unknown but may depend in part on the anatomic changes caused by the dilatation itself. To facilitate communication and evaluation of the results of PTCA, a classification of the angiographic findings and their potential mechanisms is presented. Recognition and analysis of these angiographic findings may be helpful in evaluating the long-term outcome of patients undergoing PTCA.

Percutaneous transluminal angioplasty: experience in balloon dilatation of peripheral coronary and renal arteries

Balloon catheter dilatation (percutaneous transluminal angioplasty) of peripheral, coronary and renal arteries is reported, comprising 80 arteries in 62 patients. The clinical success rate was 79% complete relief of symptoms, 9% partial relief. Recurrence was 7% in a follow-up period of one month to 20 months, mean 6 months. There was a 6% incidence of complications requiring surgery. This and other recent reports indicate that, provided the current high patency rate continues on long-term follow-up, percutaneous angioplasty has a major contribution to make in the management of arterial disease. Advantages include relatively low morbidity and cost, and short rehabilitation time. It can be repeated if necessary, and in the event of failure surgical treatment is seldom precluded. Close co-operation between disciplines is essential for optimum case selection and if complications arise.