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PubMed2006

Update on coronary angioscopy: review of a 20-year experience and potential application for detection of vulnerable plaque.

Predicting the occurrence of future acute coronary syndromes remains an important challenge of contemporary cardiology. It is thought that detecting the individual vulnerable plaques in patients can be an important step to preventing myocardial infarction and sudden cardiac death. Coronary angioscopy can provide detailed information of the luminal surface of plaque, such as color, thrombus, or disruption, and is one of a few possibly useful imaging modalities for identifying vulnerable plaques. During its 20-year history, coronary angioscopy has been used as a diagnostic tool or to guide coronary angioplasty, and has contributed to our understanding of the pathophysiology of coronary artery disease. Yellow plaques seen during angioscopy seem to have many characteristics of high risk or vulnerable plaques, most consistent with the thin-cap fibroatheroma. Moreover, differences in yellow color have been reported to reflect differences in the structure or composition of plaques. Development of quantitative methods to assess plaque color and histopathologic correlations in conjunction with prospective natural history studies may lead to advances in vulnerable plaque detection by coronary angioscopy. Although current angioscopic devices are limited by the need to displace the column of blood in order to see the vessel wall, and by the lack of quantitative colorimetric methods, advances in technology may lead to new device versions that could be practical for expanded clinical use.

Angioscopy↗
PubMed2003

Intravascular modalities for detection of vulnerable plaque: current status.

Progress in the diagnosis, treatment, and prevention of atherosclerotic coronary artery disease is dependent on a greater understanding of the mechanisms of coronary plaque progression. Autopsy studies have characterized a subgroup of high-risk, or vulnerable, plaques that result in acute coronary syndromes or sudden cardiac death. These angiographically modest plaques share certain pathologic characteristics: a thin, fibrous cap, lipid-rich core, and macrophage activity. Diagnostic techniques for vulnerable-plaque detection, including serologic markers and noninvasive and invasive techniques, are needed. Recent advances in intravascular imaging have significantly improved the ability to detect high-risk, or vulnerable, plaque in vivo by using various features of plaque vulnerability as methods of identification. The characteristic anatomy of a thin, fibrous cap overlying a lipid pool has promoted high-resolution imaging, such as intravascular ultrasound, optical coherence tomography, and intracoronary magnetic resonance. The lipid-rich core is identifiable by angioscopically detected color changes on the plaque surface or by its unique absorption of energy, or "Raman shift," of its cholesterol core, driving coronary spectroscopy. Finally, temperature heterogeneity arising at foci of plaque inflammation has prompted the development of intracoronary thermography. In this review, we will discuss these techniques, their relative advantages and limitations, and their potential clinical application.

Angioscopy↗
PubMed1991

Dissolution of peripheral arterial thrombi by ultrasound.

BACKGROUND: We have previously shown that continuous-wave ultrasound can rapidly dissolve human thrombi in vitro, with 99% of all residual particles measuring less than 10 microns in diameter. To assess the effects of pulsed-wave ultrasound energy on whole blood clots, 1) in vitro studies were preformed to assess precisely the rates of clot disruption and to quantify particulate size, and 2) in vivo studies were performed to assess the efficacy and safety of catheter-delivered ultrasound for intra-arterial thrombus dissolution. METHODS AND RESULTS: In vitro, we studied 50 samples of human whole blood clots and using an 89-cm-long wire probe, applied pulse-wave energies from 8 to 23 W. The corresponding peak-to-peak tip displacement range was 63.5 - 102 microns. We studied arterial thrombosis in vivo in 21 canine superficial femoral arteries. To produce an acute thrombosis, 200 units of thrombin followed by 2 ml of 72-hour-old autologous clot were injected into a 5-7-cm segment of femoral artery and left to coagulate for 2 hours. Ultrasound energy was intermittently applied at a frequency of 20 kHz with a prototype ultrasound wire ensheathed in a catheter and directed to clots by fluoroscopy. In nine cases, angioscopic guidance was used to put the probe into direct contact with the intra-arterial thromboses. In vitro clot dissolution times were inversely related to the ultrasound power output (r = 0.95). All in vivo canine thromboses were disrupted in 4 minutes or less. All successful recanalizations were confirmed by angiography and in nine cases by angioscopy as well. Angioscopy demonstrated that probe activation caused rapid clot disruption. Histological studies of the vessels showed no evidence of thermal or cavitation injury, occlusive distal embolization, or perforation. CONCLUSIONS: Our findings in this experimental canine model suggest that ultrasound clot dissolution has the potential to be an effective and safe alternative to current treatment modalities for peripheral arterial thrombosis.

Animals↗
PubMedDate not supplied

When does atherosclerosis become irreversible? Chronological change from an early to an advanced atherosclerotic lesion observed by angioscopy.

Quite a large number of studies on atherosclerosis have been published to date. However, no report on the development and irreversibility of lesions has been published so far. The authors conducted the following experiments to examine in vivo lesions under direct vision. Atherosclerotic lesions were created in 11 Japanese macaques, and progress of the lesions was observed under changing feeding conditions. The efficacy of cholesterol-lowering therapy was also evaluated and the mechanism by which eicosapentaenoic acid (EPA) suppresses atherosclerosis was examined. The results of this long-term study were as follows: (1) Early lesions of atherosclerosis (fatty streaks) developed in the aortic wall owing to cholesterol loading disappeared when the serum concentration of total cholesterol was reduced. (2) Atheromas first developed at the orifices of major branches of the aorta. And even though serum cholesterol was reduced, the lesions gradually spread to nearby areas. (3) After atheromas developed, advancement of the lesions slowed, as assessed by angioscopy, when EPA was administered while cholesterol loading was continued. Thus, early lesions of atherosclerosis are reversible and cholesterol-lowering therapy is an effective treatment; however, since advanced lesions seem to be irreversible, cholesterol-lowering therapy may not be effective for such lesions. The results of angioscopic examination showed that EPA slowed the progression of atheromatous lesions, and probably suppression of the proliferation of smooth muscle cells is the mechanism of such effect.

Angioscopy↗
PubMed1984

Hemodynamics and gas exchange during angioscopy in the dog.

We have previously developed a technique for the in vivo visualization of the pulmonary arteries in the experimental animal with a fiberoptic instrument (angioscope). To assess the potential hemodynamic and gas exchange effects of angioscopy, we studied five dogs before and after pulmonary embolization. Sequential observations were made of arterial blood gases, mean arterial pressure, pulmonary artery pressure, heart rate, cardiac output, and the electrocardiogram. The most common arrhythmias were ventricular premature contractions which were comparable to those seen with right heart catheterization. Statistically significant, but clinically minor, effects were found on cardiac output, mean arterial pressure, and heart rate in dogs when angioscopy was performed after pulmonary embolization. We conclude that fiberoptic angioscopy does not induce deleterious effects on hemodynamics or gas exchange in the experimental animal, prior to or after embolization.

Animals↗
PubMed1989

The role of lasers in the management of peripheral vascular disease.

Although it has been almost twenty-five years since the first studies of McGuff et al, who employed the laser for atheroablation, problems still require resolution. The various laser wavelengths from ultraviolet through visible to infrared have been employed for atheroablation. The laser's greatest appeal and the most spectacular results have been in reopening channels in totally occluded vessels. The laser's greatest problem has been damage of the arterial wall and even perforation. The purpose of this presentation is to clarify the present status of available lasers for the treatment of peripheral vascular disease of the lower extremities. To this end, the initial experience with angioscopically guided laser-assisted angioplasty with a new hybrid laser probe is reported.

Aged↗
PubMed1990

Experimental and clinical percutaneous angioscopy experience with dynamic angioplasty.

The authors have used ultrathin angioscopes with high optical resolution to assess the effects of dynamic angioplasty in vitro and in vivo. Experimentally, angioscopy was used to study the effects of the 5F "Kensey" catheter in "normal" porcine coronary arteries (NPCA) and postmortem human coronary arteries (PMHCA). In NPCA, the catheter keeps a coaxial position. Intimal flaps (IFs) were seen in 21/23 NPCAs. They occurred with all cam rotation speeds and were usually single and small (less than 25% of lumen). Perforations in patent arteries were rare (1/23). However, when the catheter was forced against the wall by passing through a narrowing of 5F diameter (made by a band ligature), perforations were more common at higher cam speeds. The epicardium remained intact in two thirds of perforations. Angioscopy visualized perforations in only 10% of cases (1/10), the common sign being that of large and multiple intimal flaps, which were often obstructive (5/10). In PMHCAs, angioscopy was more sensitive than angiography in detecting atheromatous lesions. The authors were able to give a better assessment of the effect of dynamic angioplasty on treated lesions, including the demonstration of intimal flaps that were not visible on angiography. In vivo, they have performed percutaneous angioscopy before and after dynamic angioplasty using 8 French Kensey catheters. Angioscopy revealed features that were not shown angiographically.

Angioplasty, Balloon↗
PubMed1991

Human atherosclerotic coronary artery xenografts: a model for investigation of transluminal recanalization.

A model for testing transluminal recanalization techniques was developed. Fragments of human atherosclerotic coronary arteries were transplanted into carotid arteries of dogs and evaluated by angiographic, angioscopic, and histologic study within a three-month period. An inflammatory response was most intense within the first week. By two weeks no inflammation was noted. Total occlusion (n = 13) and stenosis (n = 11) of the carotid arteries were achieved without complications. The model is easy to produce within a short period and the arterial occlusion resembles human vascular disease. This model has been used to evaluate laser recanalization of vascular obstructions.

Animals↗
PubMed1998

Role of inflammation and metalloproteinases in plaque disruption and thrombosis.

Numerous pathological, clinical, angiographic and angioscopic studies have demonstrated that acute coronary syndromes (unstable angina, acute myocardial infarction and ischemic sudden death) are most frequently the consequence of plaque disruption (plaque rupture or superficial plaque erosion) and consequent coronary thrombosis. Several serial angiographic studies have demonstrated that nearly 60-70% of acute coronary syndromes evolve from mildly to moderately obstructive atherosclerotic plaques. Coronary plaque disruption appears to be a function of both the composition of the plaque (plaque vulnerability ) as well as extrinsic triggers that may precipitate plaque disruption in a vulnerable plaque. Vulnerability for plaque disruption appears to be largely determined by the size of the lipid-rich atheromatous core, the thickness of the fibrous cap covering the core, and the presence of ongoing inflammation within and underneath the cap. Inflammatory cells may play a critical role in plaque disruption through the elaboration of matrix degrading metalloproteinases or MMPs (collagenases, gelatinases, stromelysins and matrilysin) and by inhibition of function and survival of matrix-synthesizing smooth muscle cells. Inflammatory cells may also play a critical role in triggering thrombosis following plaque disruption through the tissue factor pathway. In addition, stresses resulting from hemodynamic and mechanical forces may precipitate plaque disruption, particularly at points where the fibrous cap is weakest, such as at its shoulders. The degree of thrombosis following plaque disruption is determined by the thrombogenicity of the disrupted plaque, disturbed local rheology and systemic thrombotic-thrombolytic milieu. Surges in sympathetic activity provoked by sudden vigorous exercise, emotional stress -- including anger, or cold weather, may also trigger plaque disruption. These observations have led to the concept of plaque stabilization as a new clinical strategy for the prevention of acute coronary syndromes. Plaque stabilization can be achieved through pharmacologic and lifestyle-modifying interventions that reduce vulnerability to plaque disruption by altering plaque composition and/or inflammatory activity within the plaque.

Arteritis↗
PubMed2000

Popliteal artery aneurysms: is endovascular reconstruction durable?

PURPOSE: To describe an endovascular method of performing femoropopliteal in situ saphenous vein (SV) bypass and popliteal artery aneurysm (PAA) embolization. METHODS: Twenty-two patients underwent PAA operations. Twelve patients had conventional SV bypasses with PAA proximal and distal ligation, whereas 10 underwent PAA embolization and an endovascular in situ SV bypass (EISB). The endovascular procedure was performed using an angioscopically guided side branch coil occlusion system. The PAAs were coil embolized under fluoroscopic surveillance. RESULTS: No deaths or wound complications occurred in the EISB group. The mean hospital length of stay (LOS) was 2.1 days. Seven EISB procedures were performed through 2 incisions, whereas 3 operations required an additional incision. One graft occluded at 3 months. All PAAs remained occluded by color-flow ultrasonography at follow-up ranging from 4 to 23 months (mean 13.6); cumulative primary patency was 89%. In the conventional bypass group, no deaths occurred, but 3 (25%) patients had wound complications. The mean LOS was 6.2 days, and 1 graft occluded, giving an 86% cumulative primary patency at 42 months. CONCLUSIONS: This minimally invasive technique obviates an extensive incision to harvest the SV and ligate the PAA proximally and distally. If long-term endovascular bypass graft patency and PAA occlusion rates prove to be similar to open operative results, the benefits of reduced wound complications, decreased hospital LOS, and increased health care savings support further investigation of this endovascular approach for the treatment of PAA.

Adult↗
PubMed2001

Arterial thrombus dissolution in vivo using a transducer-tipped, high-frequency ultrasound catheter and local low-dose urokinase delivery.

PURPOSE: To examine the hypothesis that a transducer-tipped high-frequency ultrasound drug-delivery catheter may augment the thrombolytic effects of locally delivered low-dose urokinase and result in improved recanalization rates and reduced residual thrombotic burden. METHODS: Thrombi were induced in situ bilaterally in 5- to 6-cm-long segments of the superficial femoral arteries in 9 dogs by intraluminal thermal damage and injection of thrombin. A transducer-tipped high-frequency local drug-delivery catheter was applied at 1.1 MHz and 0.6 W for 60 minutes to one superficial femoral artery segment, and an identical catheter with an inactivated ultrasound transducer was used to treat the contralateral control segment. Urokinase (5000 IU/kg) was delivered bilaterally into the thrombi during the treatment interval. RESULTS: Angiography documented TIMI grade 2 or 3 flow in 9 (100%) segments in the ultrasound-treated group versus 6 (67%) of the controls (no ultrasound) (p = 0.058). Angiographically detected distal embolization was found in 2 ultrasound-treated segments compared with 5 controls (p = 0.02). Protruding or occlusive thrombi were seen angioscopically in 8 (89%) control segments but in only 1 (11%) of the ultrasound-treated arteries (p < 0.001). By histopathology, 7 (78%) segments in the control group had occlusive thrombi, whereas only 3 nonocclusive thrombi were found in the ultrasound-treatment group (p < 0.001). CONCLUSIONS: Catheter-delivered high-frequency ultrasound and local low-dose urokinase infusion is efficacious for the treatment of acute thrombotic occlusions as evaluated by angiography, angioscopy, and histopathology.

Animals↗
PubMed2002

Virtual angioscopy using 3-dimensional rotational digital subtraction angiography for endovascular assessment.

PURPOSE: To investigate the feasibility of 3-dimensional rotational digital subtraction angiography (3D DSA) and the creation of virtual angioscopic images from its data before and after endovascular treatment. TECHNIQUE: Data sets from 3D DSA studies were used to create intraluminal images simulating angioscopy for 36 patients with arterial stenosis, aneurysm, or endoleak after stent-graft deployment. A biplanar DSA unit was used to acquire rotational angiography data, which was then processed with a surface-rendering technique to create maximum intensity projections, shaded surface displays, multiplanar reconstructions, and virtual angioscopy. 3D reconstructions were created in 2 minutes after angiography and provided realistic views adequate for vessel measurement, morphology assessment, and endoleak evaluation. CONCLUSIONS: 3D DSA and virtual angioscopy are novel techniques that have been successful in recreating images of blood vessels immediately after angiography. These techniques could be useful as additional imaging modalities to complement computed tomography or magnetic resonance imaging in the evaluation of vascular diseases after endovascular therapy.

Angiography, Digital Subtraction↗
PubMed2003

Extensive pulmonary arterial thrombi in situ in association with atrial septal defect.

A 48-year-old woman with cyanosis was referred for investigation of atrial septal defect (ASD). Blood gas analysis on admission revealed moderate hypoxemia, and a pressure study during right heart catheterization revealed pulmonary hypertension (PH). Spiral computed tomography (CT) scan disclosed extensive thrombi in dilated large symmetrical pulmonary arteries with clear lung fields, and large strand-like thrombi on the inner surface of the pulmonary arterial wall along the vascular curvature were visualized by virtual CT angioscopic imaging. The thrombi were eventually considered to be not thromboemboli but thrombi in situ, because no segmental or larger defects were detected in the lung perfusion scan, although it showed cardiovascular imprints and an inhomogeneously decreased perfusion pattern. Pulmonary thrombi in situ are an uncommon manifestation in patients with ASD, and have not been described from the evidence of both CT and lung perfusion scans. The findings indicate that pulmonary thrombi in situ are not associated with occlusion of the large pulmonary arteries and the resultant development of PH. The patient was conservatively treated with medication, and the pulmonary thrombi did not show significant change with anticoagulant therapy. She died suddenly at the age of 51 years.

Angiography↗
PubMed2003

Patient dose values in a dedicated Greek cardiac centre.

The purpose of this study was to collect information on the practice and patient doses in a major Greek cardiac centre, investigate differences between senior cardiologists of various levels of experience and compare results with the literature, in order to optimize angiographic and interventional cardiology procedures. Radiation doses from 292 patients have been studied, 195 of which had undergone coronary angiography and 97 percutaneous transluminal coronary angioplasty. All procedures were undertaken on a Siemens Angioscop X-ray equipment. The system performed under automatic exposure control using pulsed fluoroscopy of 12.5 pulses s(-1) and cine frame rate of 25 frames s(-1). Dose-area product values, fluoroscopy times, total number of cine frames as well as operator's name were collected for each patient. Only senior cardiologists have participated in the study. Median values for dose-area product were 39.1 Gy cm(2) for coronary angiography and 58.3 Gy cm(2) for percutaneous transluminal coronary angioplasty. Median fluoroscopy time was 5.0 min and 9.7 min and median number of frames was 1588 and 1823 for coronary angiography and percutaneous transluminal coronary angioplasty, respectively. Comparison showed that patient dose-area product values were lower than other studies and fluoroscopy time values were comparable. However, the total number of frames used was much higher than other published results. Differences between cardiologists with increased experience have been found. Analysis of the patient dose values obtained initiated a program of radiation protection optimization. The need for continuous training in radiation protection for interventionalists has been verified.

Adult↗
PubMed1990

Unstable angina and thrombolysis.

Unstable angina occurs in a heterogeneous population of patients. In the subset of patients with recent rest angina, both angiographic and angioscopic studies have suggested that coronary artery thrombus is often present and serves as a predictor of subsequent adverse clinical events, including recurrent angina, myocardial infarction, the need for urgent coronary revascularization, and death. Studies of thrombolytic therapy in small populations of patients with unstable angina suggest it may lyse coronary thrombus, raise the ischemic threshold, and possibly have a favorable influence on clinical outcome. Large multicenter trials of patients with unstable angina and non-Q-wave infarction have been designed to answer several questions: Will rt-PA produce improvement in angiographically determined coronary arterial stenoses? Is rt-PA superior to conventional therapy? Is there a need for routine angiography, followed by revascularization, in suitable patients? Until these questions are answered, the role of thrombolytic therapy in patients with unstable angina remains speculative.

Angina Pectoris↗
PubMed1995

The role of routine angioscopy in vascular access surgery.

PURPOSE: The purpose of this retrospective study is to describe our techniques, review our experience, and determine the feasibility, safety, and role of the routine use of angioscopy during primary and revision vascular access surgery. METHODS: Between February 1991 and October 1993, intraoperative angioscopy was routinely performed in 84 consecutive operations (51 patients) for vascular access surgery. We reviewed the videotaped recordings of the angioscopic studies together with the clinical data according to a predetermined protocol. RESULTS: There were 43 primary procedures (36 autogenous arteriovenous fistulas and 7 bridge graft fistulas) and 41 revision procedures for failed vascular access (7 autogenous arteriovenous fistulas and 34 graft bridge fistulas). In 20.9% of the primary vascular access procedures, abnormal endoluminal findings were noted. Based on these findings, only one additional intervention was performed. In revision vascular access surgery, abnormal endoluminal findings were noted in 92.7%, resulting in additional surgical interventions in 65.9% of the procedures. In the revised synthetic bridge graft fistulas, stenosis of the midgraft (n = 9) as a result of needle insertion for dialysis was more common than at venous anastomosis (n = 4). Detection and correction of endoluminal abnormalities resulted in a 30-day patency of 66.6% as opposed to 33.3% when none was detected (p < or = 0.012, Fisher's exact test). CONCLUSIONS: Routine angioscopy is technically feasible and can be performed safely in anuric patients during vascular access surgery. It provides additional and useful intraoperative information that may significantly alter the surgical procedure. Routine angioscopy may also provide new insights into the pathophysiology of vascular access failure.

Adult↗
PubMed1995

Long-term results with the Palmaz stent in the superficial femoral artery.

PURPOSE: Femoral stenting has demonstrated inconsistent and often disappointing long-term results. To compare out experience, we retrospectively analyzed a series of patients who had Palmaz balloon-expandable stents placed exclusively for superficial femoral artery (SFA) lesions. METHODS: From January 1990 to November 1993, 39 patients were evaluated for claudication (79%) or critical ischemia in 42 limbs. The culprit lesions were confined to the SFA: 24 (57%) occlusions and 18 (43%) stenoses, including 3 restenotic lesions. Stenting was elective in 12 (29%) cases: the 3 restenoses and 9 chronic, calcified occlusions. The remaining stents were applied for postangioplasty residual stenosis or angioscopic findings of thrombogenic luminal irregularities. A total of 55 prostheses were successfully implanted. All patients were maintained on ticlopidine and followed by routine duplex scanning. Follow-up angiography was performed in 28 (72%) patients between 4 and 45 months. RESULTS: In the postprocedural period, two acute thromboses (4.8%) occurred within 48 hours in patients who had long occlusions and poor runoff; no other major complications were encountered, for a clinical success rate of 95%. Follow-up evaluation ranged from 4 months to 4 years with a mean of 25 months. The restenosis rate was 19% (34% in occlusions; 10% in stenotic lesions, p = NS). At 24 months, cumulative primary patency was 77% and secondary patency 89%. CONCLUSIONS: Palmaz stents performed will in the SFA, demonstrating a low acute thrombosis rate and good long-term patency. The incidence of restenosis is likely to be greater in occlusions than in stenoses.

Aged↗
PubMedDate not supplied

Eccentric iliac artery stenosis: a canine model for angioplasty.

A canine model was developed to induce eccentric iliac artery stenosis. Lesions were induced by exposing the medial aspect of the right and left common iliac arteries in four animals to direct argon laser energy (LA). A 2.5-mm diameter side-firing laser probe was used to deliver 10 W of power in 5-s intervals. Twenty-five pulses were delivered over a 5-cm length of artery with an approximate spot size of 0.8 mm2. Selected arteries (n = 2, LA + Ca) were injected in the same laser injury site with calcium chloride (10% solution). Injections were accurately accomplished using an angioscopically guided guidewire/needle device. In all cases, the internal elastic lamina was broken with focal disruptions of the media. At 9 and 14 days, the LA (n = 3) and LA + Ca vessels (n = 1) had minimal stenoses (< 5% area reduction). These vessels contained edematous media with replacement of necrotic smooth muscle by fibrous tissue. At 23 days, the LA (n = 1) and LA + Ca (n = 1) vessels contained 22% and 33% luminal reductions, respectively, with moderate neointimal proliferation and no evidence of calcification. At 56 days the LA vessels (n = 2) contained 30 and 42% luminal area stenoses with marked neointimal hyperplasia. This preliminary data suggests that controlled arterial wall injury with LA irradiation can induce eccentric fibrointimal lesions in a canine model.

Angioplasty↗