Contribution of localized calcium deposits to dissection after angioplasty. An observational study using intravascular ultrasound

Intravascular ultrasound findings after excimer laser coronary angioplasty

Intravascular ultrasound (IVUS) was used to study 104 lesions in 98 patients after excimer laser coronary angioplasty (ELCA). Lesion site external elastic membrane (EEM) and lumen cross-sectional areas (CSA) were measured; plaque+media (P+M = EEM - lumen) CSA and percentage of cross-sectional narrowing (CSN = P+M CSA/EEM CSA) were calculated; and the results were compared to a reference site. The lumen CSA (2.6 +/- 1.0 mm2) averaged 24% larger than the cross-sectional area of the largest laser catheter used, and 64 lesions (62%) fit the definition of arterial expansion (lesion EEM CSA > reference site EEM CSA). The residual percentage of cross-sectional narrowing averaged 83.8 +/- 8.8%. Dissections were present in 44% of lesions, and were more common in lesions with superficial calcium (59%) than in lesions with only deep calcium (31%) or no calcium (20%, P = 0.0102). Dissections of superficial calcified plaque had an unusual "shattered" or "fragmented" appearance. These findings suggest that excimer laser angioplasty causes forced vessel expansion with dissection, but limited atheroablation.

Impact of plaque morphology and composition on the mechanisms of lumen enlargement using intracoronary ultrasound and quantitative angiography after balloon angioplasty

Limited information is provided by angiography on plaque morphology and composition before balloon angioplasty. Identification of plaques associated with reduced lumen gain or a high complication rate may provide the rationale for using alternative revascularization devices. We studied 60 patients with quantitative angiography and intracoronary ultrasound (ICUS) before and after balloon dilation. Angiography was used to measure transient wall stretch and elastic recoil. ICUS was used to investigate the mechanisms of lumen enlargement among different plaque compositions and in the presence of a disease-free wall (minimal thickness < or = 0.6 mm). Compared with ultrasound, angiography underestimated the presence of vessel calcification (13% vs 78%), lumen eccentricity (35% vs 62%), and wall dissection (32% vs 57%). ICUS measurements showed that balloon angioplasty increased lumen area from 1.82 +/- 0.51 to 4.81 +/- 1.43 mm2. Lumen enlargement was the result of the combined effect of an increase in the total cross-sectional area of the vessel (wall stretching, 43%) and of a reduction in the area occupied by the plaque (plaque compression or redistribution, 57%). Vessels with a disease-free wall had smaller lumen gain than other types of vessels (2.13 +/- 1.26 vs 3.59 +/- mm2, respectively, p < 0.01). Wall stretching was the most important mechanism of lumen enlargement in vessels with a disease-free wall (79% vs 37% in the other vessels). Angiography revealed a direct correlation between temporary stretch and elastic recoil that was responsible for 26% of the loss of the potential lumen gain. Thus, lumen enlargement after balloon angioplasty is the combined result of wall stretch and plaque compression or redistribution. ICUS indicates that vessels with a remnant arc of disease-free wall are dilated mainly by wall stretching compared with other types of vessels and are associated with a smaller lumen gain.

In vitro validation of intravascular ultrasound imaging after balloon angioplasty of coronary artery stenoses

Systematic studies of intravascular ultrasound imaging of in vitro balloon angioplasty on coronary arteries with a greater than 50% diameter stenosis on angiogram have not been performed. We used 23 plasma-perfused postmortem human coronary arteries with an angiographic diameter stenosis of > or = 50%. After balloon dilation the vessels were examined by 30-MHz intravascular ultrasound imaging (IVUS) and the presence of ruptures and dissections was noted. Ruptures were defined as disruptions of the vessel wall in a radial direction, and dissections were defined as disruptions in a circumferential direction. After pressure fixation they were studied by histology. On IVUS, 24 vessel wall disruptions were diagnosed in 14 arteries. On histology, 29 disruptions were diagnosed in 19 arteries. The sensitivity of IVUS for the detection of disruptions was 79%, the specificity was 75%. Total agreement was 79%. Accuracy was better for dissections (total agreement 96%) than for ruptures (total agreement 74%). Shadowing behind calcium and close contact of the catheter to the arterial wall were important sources of error in the IVUS analysis. We conclude that intravascular ultrasound imaging is accurate for the detection of disruptions after balloon angioplasty of angiographically significant coronary artery stenoses.

Role of molecular regulation in vascular calcification

Calcium deposits account for most of the dry weight of atherosclerotic lesions. Previously considered uncommon, vascular calcification is now known to be present in 80% of significant lesions and in at least 90% of patients with coronary artery disease. Previously considered a passive process, it is increasingly recognized as an active, regulated process. Previously considered benign, it is now becoming recognized as a major risk factor for cardiovascular events, and a major contributor to systolic hypertension, heart failure, plaque rupture and stenosis. To confirm the similarity of vascular calcification with embryonic osteogenesis, we demonstrated the expression of bone morphogenetic protein in calcified human lesions, and we developed an in vitro model of vascular calcification that provides a useful experimental system for elucidating the molecular regulation of this process, which we have shown to include alkaline phosphatase induction and expression of bone matrix proteins and differentiation factors. Understanding the regulatory mechanisms of vascular calcification will allow future therapeutic approaches to prevent and possibly reverse this disease and its clinical consequences.

Intravascular ultrasound predictors of outcome after peripheral balloon angioplasty

OBJECTIVE

This study investigates the potential role of intravascular ultrasound (IVUS) in the outcome in patients undergoing percutaneous transluminal angioplasty (PTA) of the superficial femoral artery.

MATERIALS

Angiographic and the qualitative and quantitative IVUS data obtained at the narrowest site derived from 39 patients before and after PTA were analysed.

RESULTS

Angiographically the diameter of the remaining stenosis seen after PTA was classified as < 50% in 31 patients (success); in eight patients a failure was encountered. Evaluating at 6 months the functional and anatomic results of the PTA in 31 patients, the intervention was a success in 14 patients (Group I) and a failure in 17 patients (Group II). The remaining eight patients defined as angiographic failure following PTA comprised Group III. Neither qualitative nor quantitative IVUS data obtained before PTA could predict outcome. Conversely, after PTA, the extent of dissection was significantly more severe in Groups II and III than in Group I. Similarly, significant differences were found between Groups I and II for mean free lumen area (13.2 vs. 9.7 mm2, respectively) and mean free lumen diameter (4.1 vs. 3.5 mm, respectively). Quantitative data obtained in Group II were similar to those in Group III.

CONCLUSION

This preliminary study demonstrates that following PTA the extent of dissection, free lumen area and diameter seen with IVUS are predictive factors of patency. Future studies with more patients are mandatory to further highlight the sensitivity of these observations.

Intravascular ultrasound approach to the diagnosis of coronary artery aneurysms

Coronary artery aneurysms are usually diagnosed by contrast coronary angiography, which portrays the silhouette of the lumen but cannot distinguish true and false aneurysms. To differentiate true and false aneurysms and to study the morphologic changes of the vessel wall, intravascular ultrasound (IVUS) was performed in patients with angiographic signs of coronary artery aneurysms. We used a 4.8F or 3.5F, 20 MHz IVUS catheter for ultrasound examination. Fourteen patients (12 men and two women ranging in age from 43 to 73 years) with angiographic signs of coronary aneurysm were enrolled. IVUS imaging was optimally obtained in all patients. The vessel area, lumen area, and plaque area of the aneurysm segment and of the proximal and distal segments were determined. IVUS showed that both the proximal and distal reference segments were severely affected by atherosclerotic lesions in all the patients and by calcium deposits in six patients. The percent stenoses were 63.0% +/- 13.7% and 60.9% +/- 17.8% in the proximal and distal reference segments, respectively. In nine patients the walls of the aneurysms showed signs of atherosclerosis. Three angiographically indicated aneurysms were found to be plaque ruptures. Although the lumen and the vessel areas of the aneurysm segments were larger than those of the proximal and distal segments (p < 0.01 and (p < 0.001), no significant differences in plaque area and plaque composition were found between the aneurysm segment and adjacent vessel segments (p > 0.05). In conclusion, IVUS allows detailed characterization of coronary aneurysms. Atherosclerosis seems to play an important role in the formation of acquired coronary aneurysms.

Comparison of intravascular ultrasonic findings after coronary balloon angioplasty evaluated in vitro with histology

This study investigated whether vascular damage and quantitative changes observed with intravascular ultrasound at the most stenotic site are representative of the ultimate outcome after coronary balloon angioplasty. Atherosclerotic coronary arteries (n = 40) were studied in vitro with intravascular ultrasound. From each vascular specimen, 10 corresponding intravascular ultrasound cross sections obtained before and after balloon angioplasty were selected for comparison with their histologic counterpart. Morphologic and quantitative data obtained from all cross sections were compared with data derived from the most stenotic site. The incidence of vascular damage (i.e., dissection, plaque rupture, and media rupture) at the most stenotic site was lower than that seen for each vascular specimen. The sensitivity of intravascular ultrasound in detecting these morphologic features for each vascular specimen was high for dissection and media rupture (79% and 76%, respectively), and low for plaque rupture (37%). After balloon angioplasty, quantitative changes seen at the most stenotic site were greater than those in all cross sections: free lumen area +58% versus +29%, media-bound area +17% versus +12%, and plaque area reduction -9% versus -6%, respectively. The increase in free lumen area was caused predominantly by media-bound area increase (81%) and to a lesser extent by plaque area decrease (19%). This study revealed that a higher incidence of vascular damage is found when the whole segment is analyzed rather than 1 single cross section at the most stenotic site. Quantitative effects of coronary balloon angioplasty seen with intravascular ultrasound were greater at the most stenotic site than at all cross sections.

Extensive intramural hematoma as the cause of failed coronary angioplasty: diagnosis by intravascular ultrasound and treatment by stent implantation

Dissections after coronary angioplasty are the major cause of ischemic events following percutaneous transluminal coronary angioplasty (PTCA) and may require additional measures such as intravascular stent deployment to relieve or prevent acute vessel closure. We describe a rare type of dissection after PTCA which caused a severe obstruction of the vessel segment proximal to the dilatation site without a visible dissection flap. Intravascular ultrasound was used to elucidate the morphology of the proximal vessel obstruction, which revealed an intramural hematoma extending into the proximal vessel segment as underlying mechanism. A Palmaz-Schatz stent was placed at the entry site of this hematoma, which led to the relief of the proximal vessel obstruction. After 3 months of anticoagulation therapy the repeat coronary angiography showed no significant restenosis. This demonstrates the unique insight into the underlying morphology of failed PTCA by intravascular ultrasound, which can help to manage even rare and unusual complications.

Coronary lesions at increased risk

An acute ischemic complication will develop in approximately 7% of patients undergoing coronary angioplasty. In more than half of these patients, thrombus, dissection, or both can be identified angiographically as the underlying cause of abrupt closure; in the remaining cases, an indeterminate morphology is observed. Predictors of dissection-mediated closure include degenerated vein graft, de novo stenosis, proximal tortuosity, high lesion grade, eccentricity, longer lesion length, and angulation. Thrombus-medicated closure is most apt to occur in degenerated vein grafts, lesions related to a recent myocardial infarction, and lesions that contain thrombus before angioplasty. However, the ability of these parameters to predict risk in an individual patient is rather weak. Angioscopy has revealed that the presence of yellow plaque confers a heightened risk of major complications. Lesions that contain areas of calcium adjacent to areas to soft plaque have been identified by intravascular ultrasound as a powerful predictor a major dissection. These sensitive new imaging techniques may eventually permit the targeting of more specific therapies to the underlying cause of closure.

High speed rotational atherectomy: outcome in calcified and noncalcified coronary artery lesions

OBJECTIVES

This study sought to determine the success and complication rates of high speed rotational coronary atherectomy in calcified and noncalcified lesions.

BACKGROUND

Percutaneous transluminal coronary angioplasty and directional coronary atherectomy of calcified lesions are associated with reduced procedural success and increased complications. Rotational atherectomy using the Rotablator catheter abrades noncompliant plaque and may improve outcome in calcified lesions.

METHODS

Data from the completed Multicenter Rotablator Registry of 2,161 rotational atherectomy procedures in single lesions were analyzed to determine the relative efficacy of rotational atherectomy for 1,078 calcified and 1,083 noncalcified lesions. The power of the study was 0.86 to detect a significant difference in outcome, if the true success rates in the noncalcified and calcified lesions were 96% and 93%, respectively.

RESULTS

Patients with calcified lesions were older (mean [+/- SD] age 66.2 +/- 10.3 vs. 60.5 +/- 11.0 years, p = 0.0001) than those with noncalcified lesions. Calcified lesions were more frequently new (75% vs. 64%, p = 0.0001), angulated (27% vs. 22%, p = 0.02), eccentric (75% vs. 64%, p = 0.0001) and long (32% vs. 27%, > 10 mm in length, p = 0.01). They were also more often complex (57% vs. 46%, p = 0.001) and located in the left anterior descending coronary artery (51% vs. 44%, p = 0.001). Adjunctive coronary angioplasty was used in 82.9% of calcified and 66.9% of noncalcified lesions. Procedural success, defined as < 50% residual stenosis without major complications, was achieved in 94.3% of calcified and 95.2% of noncalcified lesions (p = 0.32). Major complication rates were 4.1% in calcified and 3.1% in noncalcified lesions (p = 0.24). Non-Q wave myocardial infarction was documented in 10.0% of calcified and 7.7% of noncalcified lesions (p = 0.054). Mean postprocedural residual stenosis was 21.6 +/- 13.9% in calcified and 23.3 +/- 15% in noncalcified lesions (p = 0.39).

CONCLUSIONS

In this review of data from a large multicenter registry, the success rate of rotational atherectomy was not reduced by calcification despite the more frequent complex nature of the calcified lesions. The Rotablator catheter is likely to be the device of choice for percutaneous intervention in calcified lesions, but definitive conclusions await the results of randomized trials.

Value and limitations of intravascular ultrasound imaging in characterizing coronary atherosclerotic plaque

Intravascular ultrasound uses a high-frequency, miniaturized, ultrasound transducer positioned on the tip of a coronary catheter to provide detailed cross-sectional images of the coronary vessel wall. Unlike angiography, which details only luminal encroachment, this imaging technique has the unique potential to provide an image of the atherosclerotic plaque, characterize its composition, and assess stenosis severity. Lipid-filled "soft" plaque, dense fibrous "hard" plaque, calcification, and thrombosis have all been identified on intravascular ultrasound images. Individual lesion types have been associated with specific clinical ischemic syndromes and with different responses to catheter-based intervention. By means of analyzing tissue composition, intravascular ultrasound may permit identification of high-risk lesions that may eventually rupture and cause unstable coronary ischemic syndromes. This article reviews the current approaches to plaque characterization by two-dimensional intravascular ultrasound imaging and addresses clinical implications, technical limitations, and future promise of the technique.

Influence of plaque morphology on the mechanism of luminal enlargement after directional coronary atherectomy and balloon angioplasty

OBJECTIVE

To relate the mechanism of luminal gain after directional atherectomy and balloon angioplasty to the morphological characteristics of the coronary lesions, assessed by intravascular ultrasound imaging.

DESIGN

Intravascular ultrasound imaging was performed before and after the revascularisation procedure to assess the contribution of wall stretching and plaque reduction in luminal gain.

SUBJECTS

32 patients undergoing balloon angioplasty and 29 undergoing directional coronary atherectomy.

MAIN RESULTS

The main luminal area in vessels treated by balloon angioplasty increased from 1.51 (SD 0.30) to 3.91 (1.09) mm2 (P < 0.0001) with a concomitant increase in total vessel area from 11.44 (2.73) to 13.07 (2.83) mm2 (P < 0.0001). Therefore stretching of the vessel wall accounted for 68% of the luminal gain while plaque reduction accounted for the remaining 32%. This mechanism ranged from 45% in non-calcific plaques to 81% in echogenic plaques. The main luminal area in vessels treated by directional atherectomy increased from 1.49 (0.32) to 4.68 (1.73) mm2 (P < 0.0001), with a concomitant increase of total vessel area from 13.61 (4.67) to 15.2 (4.04) mm2 (P = 0.006). Thus stretching of the vessel wall accounted for 49% of the luminal area gain and plaque reduction for the remaining 51%. The presence of calcium influenced the relative contribution of these two mechanisms to the final luminal gain after directional atherectomy, since in calcific plaques stretching of the vessel wall accounted for only 9% of the luminal gain as compared to 56% in non-calcific plaques. After balloon angioplasty there was greater evidence of coronary dissections (32% v 3% after directional atherectomy, P < 0.01) and plaque fissure (60% v 0%, P < 0.01). Plaque fissure was more frequently seen in echolucent and concentric lesions, whereas dissections prevailed in echogenic and eccentric lesions.

CONCLUSIONS

Intravascular ultrasound imaging may allow the assessment of acute changes in lumen and vessel wall after revascularisation procedures, and help in evaluating the potential effect of the structure and morphology of coronary lesions on the mechanism of luminal enlargement.

Acute coronary artery closure following intracoronary ultrasound examination

Two patients undergoing intracoronary ultrasound examination were complicated by acute coronary artery closure. One of the complications was thought to be caused by intimal dissection and thrombus formation and the other was thought to be caused by intimal dissection and subsequent embolization. The complications were successfully managed conservatively in both cases.

Coronary artery morphologic features after coronary rotational atherectomy: insights into mechanisms of lumen enlargement and embolization

The coronary arteries and myocardium from two patients who died after coronary rotational atherectomy were analyzed to gain insights into the mechanisms of lumen enlargement and to document embolization of calcified plaque. Rotational atherectomy resulted in sharp cuts in plaque, producing a relatively smooth luminal surface. When extensive nodular calcific atherosclerosis was present, the luminal surface was focally uneven with exposure of jagged calcified plaque to blood flow. Deep plaque fissures and medial dissections were also seen. These fissures may have been created by the rotoblator or by adjunctive balloon angioplasty. Multiple calcific atheroemboli were present after rotoblator use in plaques containing extensive nodular calcification; in moderately calcified plaque only one small atheroembolus was found. Thus embolization of calcified plaque can occur after rotational atherectomy and may correlate with the severity of plaque calcification. Rotational atherectomy produces a focally smooth, sharp-edged, luminal surface, a lumen enlargement mechanism different from balloon angioplasty.

Intracoronary ultrasound: current state of the art

Images

Three dimensional reconstruction of cross sectional intracoronary ultrasound: clinical or research tool?

Images

Patterns of calcification in coronary artery disease. A statistical analysis of intravascular ultrasound and coronary angiography in 1155 lesions

BACKGROUND

Target lesion calcium is a marker for significant coronary artery disease and a determinant of the success of transcatheter therapy.

METHODS AND RESULTS

Eleven hundred fifty-five native vessel target lesions in 1117 patients were studied by intravascular ultrasound (IVUS) and coronary angiography. The presence, magnitude, location, and distribution of IVUS calcium were analyzed and compared with the detection and classification (none/mild, moderate, and severe) by angiography. Angiography detected calcium in 440 of 1155 lesions (38%): 306 (26%) moderate calcium and 134 (12%) severe. IVUS detected lesion calcium in 841 of 1155 (73%, P < .0001 versus angiography). The mean arc of lesion calcium measured 115 +/- 110 degrees; the mean length measured 3.5 +/- 3.7 mm. Target lesion calcium was only superficial in 48%, only deep in 28%, and both superficial and deep in 24%. The mean arc of superficial calcium measured 85 +/- 108 degrees; the mean length measured 2.4 +/- 3.4 mm. Three hundred seventy-three of 1155 reference segments (32%) contained calcium (P < .0001 compared with lesion site). The mean arc of reference calcium measured 42 +/- 80 degrees; the mean length measured 1.7 +/- 3.6 mm. Only 44 (4%) had reference calcium in the absence of lesion calcium. Angiographic detection and classification of calcium depended on arcs, lengths, location, and distribution of lesion and reference segment calcium. By discriminant analysis, the classification function for predicting angiographic calcium included the arc of target lesion calcium, the arc of superficial calcium, the length of reference segment calcium, and the location of calcium within the lesion. This model correctly predicted the angiographic detection of calcification in 74.4% of lesions and the angiographic classification (none/moderate/severe) of calcium in 62.8% of lesions.

CONCLUSIONS

IVUS detected calcium in > 70% of lesions, significantly more often than standard angiography. Although angiography is moderately sensitive for the detection of extensive lesion calcium (sensitivity, 60% and 85% for three- and four-quadrant calcium, respectively), it is less sensitive for the presence of milder degrees.

An explanation for discrepancy between angiographic and intravascular ultrasound measurements after percutaneous transluminal coronary angioplasty

OBJECTIVES

This study attempted to determine why there is a discrepancy between angiographic and intravascular ultrasound measurements after coronary balloon angioplasty.

BACKGROUND

Previous studies have shown a poor correlation between angiographic and intravascular ultrasound measurements after percutaneous coronary balloon angioplasty.

METHODS

After successful balloon angioplasty, 91 lesions in 84 patients were studied by intravascular ultrasound. Plaque morphology on intravascular ultrasound was classified as demonstrating a superficial injury if there was either no fracture or only a small tear that did not extend to the media versus a deep injury defined as the presence of a plaque fracture that reached the media. Measurements of minimal lumen diameter were compared between angiography and intravascular ultrasound.

RESULTS

On ultrasound imaging, a superficial injury pattern was observed in 44 lesions, whereas a deep injury was seen in 47 lesions. There were no statistical differences at baseline in patient or lesion characteristics. In the superficial injury group there was a significant correlation between angiography and intravascular ultrasound for minimal lumen diameter (r = 0.67) and lumen cross-sectional area (r = 0.69). In the deep injury group there was a poor correlation for minimal lumen diameter (r = 0.05) and lumen cross-sectional area (r = 0.28). After balloon angioplasty, the angiographic appearance showed a normal contour in 34%, the presence of dissection in 38% or a hazy appearance in 23%. On ultrasound imaging after angioplasty, the superficial injury group comprised 65% of lesions with a normal angiographic appearance and 67% of lesions with a hazy appearance, whereas 77% of lesions with an angiographic diagnosis of dissection were in the deep injury group by ultrasound (p = 0.0005).

CONCLUSIONS

These observations suggest that the discrepancies between angiographic and ultrasound measurements are due to differences in plaque morphology created by balloon dilation. Superficial injuries demonstrate similar results by angiography or ultrasound, whereas a deep injury to the plaque produces a difference in measurements between angiography and ultrasound. When angiography reveals a dissection, there is a high probability that intravascular ultrasound will demonstrate a plaque fracture extending to the media.

Lumen and plaque shape in atherosclerotic coronary arteries assessed by in vivo intracoronary ultrasound

Current knowledge of lumen and plaque shape of atherosclerotic coronary vessels is derived from in vitro examination of coronary vessels. The in vivo plaque and lumen shape was studied by intracoronary ultrasound (ICUS) imaging in 82 patients with coronary artery disease and the images were analyzed by computerized morphometry. In 386 of the 638 cross sections (61%) with atherosclerotic plaque, nondiseased wall (intima thickness < 200 microns) was present in the ICUS image; in 440 sections (69%), the plaque was located eccentrically in the vessel. Although the extent of nondiseased wall segment and eccentricity decreased with plaque burden, 42% of cross sections with plaque stenosis > 60% had residual nondiseased wall, and 40% of these cross sections showed eccentric plaque. A circular or near-circular lumen (ratio of long/short diameter < 1.1) was found in 252 cross sections (39%), an elliptical lumen in 370 (58%), and a "D"-shaped lumen in 16 cross sections (3%); slit- or star-like lumen shapes were not detected. The ratio of long/short diameter was lower in the 555 noncalcified (1.10 +/- 0.08) than in the 83 calcified cross sections (1.15 +/- 0.08; p < 0.001). Radiographic lumen area measurements were simulated in ellipse models based on the long and short lumen axes measured in the ICUS images. Assuming a single radiographic view, maximal over- or underestimation of up to 40% compared with the true vessel lumen is possible. Errors in lumen area measurements increased with plaque area stenosis, reflecting the more elliptical lumen shape in advanced coronary disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term histologic patency after percutaneous transluminal coronary angioplasty is predicted by the creation of a greater lumen area

OBJECTIVES

This study assessed the relation between histologic acute and long-term lumen size after coronary angioplasty.

BACKGROUND

Angiographic studies suggest that the creation of a larger acute lumen is associated with a reduced incidence of restenosis. Histologic evaluation of the influence of the acute lumen on late outcome has not been previously reported.

METHODS

Detailed histologic examination and planimetry were performed in 28 postmortem coronary arteries subjected to angioplasty at an average of 71 weeks antemortem. The lumen area on each histologic segment was defined as the final lumen area. The lumen area immediately after angioplasty, the acute lumen area, was defined by the sum of the neointimal area plus final lumen. A final lumen area > or = 25% of the arterial area was considered a long-term success; a final lumen area < 25% was considered a long-term failure.

RESULTS

Arterial size and neointimal area were similar in long-term successes and failures. In successes, the mean (+/- SD) acute lumen area was greater than in failures (4.1 +/- 1.9 vs. 2.7 +/- 1.4 mm2, respectively, p < 0.001). The acute lumen area as a percent of arterial area was 46 +/- 10% in successes versus 27 +/- 11% in failures (p < 0.0001). The corresponding estimated mean acute lumen diameter stenosis was 24 +/- 8% in successes versus 42 +/- 12% in failures (p < 0.0001). Plaque area was greater in failures (7.1 +/- 3.2 mm2) than in successes (4.8 +/- 2.4 mm2, p < 0.002).

CONCLUSIONS

Neointimal proliferation after angioplasty occurs in all dilated coronary arteries, and the amount of neointimal growth is independent of vessel size. The creation of a larger lumen and a larger lumen as a percent of vessel size were associated with an improved long-term histologic patency.

Intravascular ultrasound guidance for peripheral vascular interventions

Intravascular ultrasound (IVUS) imaging during peripheral endovascular interventions adds important information regarding the distribution of disease by providing controlled measurements of the cross-sectional area of the vessel lumen and wall prior to and following procedures. IVUS is useful in determining the mechanism and efficacy of balloon angioplasty, in guiding atherectomy devices, and in assuring appropriate placement of intravascular stents. The incorporation of an IVUS element into catheter-based interventional devices may improve the immediate and long-term results of endovascular interventions by decreasing complications from dissection and perforation of the arterial wall. Combined IVUS-stent prototype catheters are being developed to enable imaging and deployment simultaneously. Similar devices are being explored to enhance expedient, precise delivery of endoluminal grafts. Future studies of endovascular techniques should include IVUS, when possible, to accurately quantitative the initial efficacy of devices and to determine the nature and distribution of recurrent lesions.

Detection of intralesional calcium by intracoronary ultrasound depends on the histologic pattern

This study was designed to examine the accuracy of intravascular ultrasound in detecting different histologic types of calcium pattern in human coronary artery atherosclerotic lesions. Previous studies have shown that calcium deposits in atherosclerotic lesions may occur in various forms and that intravascular ultrasound is a sensitive technique to detect calcium in atherosclerotic lesions. However, there has been no distinction between varying image representations of calcium and different histologic patterns of intralesional calcific deposits. Calcific lesions have an important clinical impact on the outcome of intracoronary transcatheter therapy, and the varying types of calcium may also play a role in the guidance of intracoronary interventions. Fifty fresh coronary vessel segments were studied by intracoronary ultrasound imaging and the images compared with the corresponding histologic sections. With intracoronary ultrasound imaging, calcium was defined as bright echo with corresponding sharp edged shadowing in the distal field. Three different histologic types of calcification were defined, and the sensitivity and specificity of the detection by intravascular ultrasound were determined for each type. Dense calcified plaques (type 1) were found 18 cases, microcalcification (small flecks of calcium) with single calcium fleck size < or = 0.05 mm (type 2) in 12 cases, and combination of calcified plaque surrounded by small calcium flecks (type 3) in 3 cases. In 17 (34%) coronary vessel segments, histologic analyses detected no calcium. Intracoronary ultrasound correctly detected 16 (89%) of 18 cases of type 1 calcification, 2 (17%) of 12 type 2, and all 3 (100%) type 3. Sensitivity for detection of type 1 and 3 calcification was 90%, with specificity of 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative assessment of peripheral and coronary artery lesions before and after balloon angioplasty: a comparison of intravascular ultrasound and angiography

Intravascular ultrasound and conventional angiography were used to determine the degree of stenosis before and after angioplasty in 25 consecutive patients with peripheral arterial occlusive disease and 15 selected patients with coronary artery disease. Angiographic determinations of the luminal area and percent stenosis were made with the help of an automatic detection system, and the same parameters were evaluated planimetrically in the ultrasound studies. Following angioplasty of peripheral lesions, angiography demonstrated a significantly greater increase in mean luminal area (10.8 +/- 7.8 mm2 vs 5.8 +/- 4.0 mm2; P < 0.05) and a greater reduction in degree of stenosis (26% +/- 16% vs 14% +/- 11%; P < 0.05) than did the ultrasonic investigation. There was a significant but moderate correlation between values for the luminal area determined by angiography and ultrasound before angioplasty (r = 0.75; SEE = 4.8 mm2) and in normal proximal segments of coronary arteries (r = 0.79; SEE 4.1 mm2). Following angioplasty there was no significant correlation between angiographic findings and those determined by intravascular ultrasound in peripheral or coronary lesions. These results suggest that angiography and intravascular ultrasound are fundamentally different imaging and analysis techniques. Following angioplasty, conventional angiography rarely demonstrated dissection or intraluminal filling defects, while intravascular ultrasound detected plaque rupture and the presence of intraluminal atheroma in almost all cases. Quantitative determinations of luminal area and degree of stenosis rely on indirect measures with conventional angiography, while these parameters are determined directly by intravascular ultrasound.(ABSTRACT TRUNCATED AT 250 WORDS)

Transverse coronary dissection resulting in abrupt vessel closure following directional coronary atherectomy: clinical, angiographic, and intracoronary ultrasound findings

A 60-year-old man underwent directional coronary atherectomy (DCA) of the mid portion of a large, anatomically dominant left circumflex coronary artery, resulting in propagating transverse dissection and subsequent complete distal occlusion. Intravascular ultrasound imaging (IVUS) of the dissected segment demonstrated the entry point of the dissection, and systolic compression of the true vessel lumen, prior to angiographic deterioration of distal coronary flow.

TGF-beta 1 and 25-hydroxycholesterol stimulate osteoblast-like vascular cells to calcify

Previous studies in our laboratory demonstrated messenger RNA for bone morphogenetic protein-2a in human calcified plaque, suggesting that arterial calcification is a regulated process, similar to osteogenesis. To further test this hypothesis, we have isolated and cloned a subpopulation of cells from bovine aortic media that show osteoblastic potential. These novel cells are primarily distinguished from smooth muscle cells by expression of a surface marker preliminarily identified as a modified form of the ganglioside sialyl-lactosylceramide (GM3). Osteoblastic potential was indicated by high levels of alkaline phosphatase and collagen I, expression of osteopontin and osteonectin (SPARC), and production of bone-specific osteocalcin and hydroxyapatite. Cultures of these cells were stimulated to form increased numbers of calcium-mineral-producing nodules by the oxysterol 25-hydroxycholesterol as well as by transforming growth factor-beta 1, both known to be present in atherosclerotic lesions. The stimulation of calcifying vascular cells in the artery wall by these two factors suggests a possible mechanism for the colocalization of calcification with atherosclerosis in vivo.

Composition of coronary atherosclerotic plaque in the intima and media affects intravascular ultrasound measurements of intimal thickness

OBJECTIVES

The purpose of this study was to evaluate how intravascular ultrasound-determined thickness and reflectivity of the inner echogenic layer of coronary artery plaque is affected by changes in collagen, elastin, proteoglycan, calcium and lipid content in the intima and media.

BACKGROUND

Coronary artery plaque often results in disruption of the internal elastic lamina and in increased collagen in the media as well as increased intimal lipid, calcium and proteoglycan content. How these factors affect intravascular ultrasound-derived measurements of intimal thickness are unknown.

METHODS

Twenty-one coronary artery segments from 10 patients with varying degrees of coronary artery disease were obtained fresh and unfixed at autopsy. Intravascular ultrasound (30-MHz, 3.5F catheter) was performed at regions in the vessel where a three-layered region was evident. Quantitative measurements of inner echogenic and deeper echolucent layer thickness were determined as well as estimates of ultrasound reflectivity and compared with histologic measurements of intimal and medial thickness and collagen, proteoglycan, lipid and calcium content.

RESULTS

In plaque > 300 microns thick and equivalent histologic levels of collagen, inner echogenic layer reflectivity was greater in regions with a greater amount of calcium and proteoglycan and lesser amounts of lipid. Inner echogenic layer thickness correlated well with intimal thickness but had the best correlation with intimal and medial thickness when medial collagen content was increased (r = 0.89). The median observed difference between intimal and inner echogenic thickness was 160 (p < 0.05 compared with zero), whereas the median observed difference between inner echogenic thickness and intimal plus medial thickness when medial collagen content was increased was 60 (not significantly different from zero).

CONCLUSIONS

The inner echogenic layer of human coronary artery plaque may represent both intima and media. The echolucent layer by ultrasound may represent only the basal section of the media that does not contain high collagen content.

Impact of preintervention intravascular ultrasound imaging on transcatheter treatment strategies in coronary artery disease

Preintervention intravascular ultrasound (IVUS) imaging was performed in 313 target lesions in 301 patients. Revascularization strategy intended before imaging was compared with the treatment actually performed; there was a change in therapy in 124 lesions (40%) in 121 patients (40%). This included: (1) assessment of lesion severity leading to revascularization when none had been planned (n = 20, 6%), (2) avoiding surgery or catheter-based revascularization that had originally been planned (n = 21, 7%), and (3) assessment of lesion composition leading to a change in revascularization strategy (n = 20, 6%) or for selecting the revascularization strategy (n = 63, 20%). Nine of these 121 patients were referred for coronary artery bypass graft surgery. IVUS minimal lumen diameter correlated well with angiography (r = 0.83); however, a disagreement was the reason for deciding to perform or not to perform revascularization in 41 lesions (13%). IVUS assessment of target lesion calcification, eccentricity and unusual morphology were the reasons for changing or selecting specific devices: (1) concentric and eccentric lesions with significant superficial calcium were treated with rotational atherectomy, excimer laser angioplasty or surgery; (2) eccentric lesions that did not contain significant superficial calcium were treated with directional atherectomy; (3) dissections and true aneurysms were treated with stent placement even if calcified; (4) thrombus-containing lesions in vein grafts were treated with thrombolytic therapy or extraction atherectomy, or both; and (5) fibrotic vein graft lesions were treated with balloon angioplasty or stent placement.

Preliminary results from attenuation-slope mapping of plaque using intravascular ultrasound

Excised femoral and iliac artery segments have been examined with 20 MHz intravascular ultrasound followed by histological assessment. During the ultrasound examinations, radio-frequency (RF) data were recorded digitally, and used for calculating local values of attenuation slope throughout the tissue, using a frequency-domain technique. The RF data were also reconstructed as conventional ultrasound images, and the attenuation-slope information presented as a threshold colour overlay. Areas identified as degenerative plaque in the histological assessments were usually found to correspond to areas of high attenuation slope, and were clearly identified from the pattern of colours on the combined image. Some examples are presented, illustrating the appearance of various pathologies imaged by this technique.

Molecular and cellular concepts in atherosclerosis

Atherosclerosis is a complex disease of uncertain cause. Its pathobiology is believed to represent an abnormal expression of the processes of vascular healing. Etiologic models derive from a 'response to injury' paradigm and can be divided into three separate disease stages: endothelial dysfunction, smooth muscle proliferation and architectural disruption. The initiating event of endothelial dysfunction is unknown, but is believed to be related to low-density lipoproteins and/or their oxidized derivatives. Endothelial injury is signalled to the smooth muscle cells of the media by three routes: direct cell-cell interaction, secretion of soluble growth factors and monocyte-derived cytokines. Monocytes are recruited by the endothelium and invade the subintimal space by a complex interaction of a variety of adhesion proteins and receptors on both cell types. Smooth muscle cell proliferation is initiated by a change in phenotype expression from 'contractile' to 'synthetic' resulting from the binding of fibronectin to specific integrin receptors. Three functionally distinct activities may represent separate subtypes of the 'synthetic phenotype': migration from the media to the intima, increased proliferation and inappropriate extracellular matrix synthesis. The loss of normal regulatory control and anchorage independence of proliferation suggest a relationship to oncogenic transformation. Both migration and proliferation result from the binding of platelet-derived growth factor-like factors to smooth muscle cell receptors, which initiates a cascade of intracellular molecular events leading either to cytoskeletal locomotory restructuring or cell cycle activation. Both pathways also appear to be coregulated by integrin receptors and both depend upon phosphorylation of cell membrane, cytosolic and nuclear regulatory proteins. Clinical expression of atherosclerosis may follow sudden loss of architectural integrity of the intimal plaque by three different mechanisms: plaque fissuring, intraluminal plaque rupture or intramural hemorrhage related to abnormal vessel wall stress and/or biochemistry.

Mechanisms and outcomes of angioplasty and atherectomy assessed by intravascular ultrasound imaging

Catheter-based intravascular ultrasound is a relatively new imaging tool to examine endovascular structure. One major goal for the development of intravascular ultrasound imaging has been to help clarify the mechanism of interventional therapies such as balloon angioplasty and directional atherectomy. Pathologic studies have suggested that plaque distribution and composition are key features that relate to initial and long-term success of coronary interventions. However, relatively little is known by angiography about the nature of plaque in the clinical setting. Intravascular ultrasound imaging provides a high resolution, "on-line" method of tracking the effects of catheter interventions such as balloon angioplasty and atherectomy. Because of its ability to visualize tissue beneath the luminal surface, ultrasound is generating new insights into the effect of plaque composition and distribution on the response to catheter therapies. With pre-procedure ultrasound imaging, it is increasingly possible to predict the result of a particular intervention, offering the potential for developing strategies of lesion-targeted therapy based on certain plaque characteristics. This article presents the early results of the GUIDE trial as a "works in progress" view of the role of intravascular ultrasound in helping interventionalists to understand--and to optimize--angioplasty and atherectomy.

Sequential intravascular ultrasound characterization of the mechanisms of rotational atherectomy and adjunct balloon angioplasty

OBJECTIVES

The purpose of this study was to use sequential intravascular ultrasound imaging before intervention, after rotational atherectomy and after adjunct balloon angioplasty to characterize the mechanisms of lumen enlargement after each.

BACKGROUND

Rotational atherectomy uses a high speed, rotating, diamond-tipped elliptic burr to abrade atherosclerotic plaque to increase lumen size. In vitro studies have shown that high speed rotational atherectomy selectively abrades hard, especially calcified, plaque elements. However, rotational atherectomy procedures usually require adjunct balloon angioplasty.

METHODS

Forty-eight lesions in 46 patients were treated with rotational atherectomy followed by adjunct balloon angioplasty in 44. Quantitative coronary arteriographic and intravascular ultrasound measurements of the target lesion were made before intervention, after rotational atherectomy and after balloon angioplasty.

RESULTS

Before intervention, target lesion external elastic membrane area measured 17.3 +/- 5.9 mm2, lumen area measured 1.8 +/- 0.9 mm2 and plaque plus media area measured 15.7 +/- 4.1 mm2. After rotational atherectomy, lumen area increased, plaque plus media area decreased, arc of target lesion calcium decreased and 26% of the target lesions had dissection planes. After adjunct balloon angioplasty, external elastic membrane area increased, lumen area increased, plaque plus media area did not change and 77% of the target lesions had dissection planes. Arterial expansion was seen in 80% of lesions. The pattern of dissection plane location, which was predominantly within calcified plaque after rotational atherectomy, became predominantly adjacent to calcified plaque after adjunct balloon angioplasty (p = 0.008).

CONCLUSIONS

Sequential intravascular ultrasound imaging shows that high speed rotational atherectomy causes lumen enlargement by selective ablation of hard, especially calcific, atherosclerotic plaque with little tissue disruption and rare arterial expansion. Adjunct balloon angioplasty further increased lumen area by a combination of arterial dissection and arterial expansion, especially of compliant, noncalcified plaque elements.

Rotational coronary atherectomy after unsuccessful coronary balloon angioplasty

The clinical and angiographic outcome of patients undergoing rotational coronary atherectomy after unsuccessful balloon angioplasty was evaluated using quantitative angiographic methods to provide insight into this procedure's mechanism of benefit. During the study period, 41 patients (50 lesions) were referred for rotational atherectomy after standard balloon angioplasty was unsuccessful. After rotational atherectomy, percent diameter stenosis was reduced from 72 +/- 14% to 41 +/- 16% (p < 0.001); adjunct balloon angioplasty was performed in 44 lesions (88%), resulting in a 25 +/- 17% final diameter stenosis (p < 0.001). The acute gain in minimal lumen diameter was 1.20 +/- 0.59 mm. In lesions needing adjunct balloon dilatation, lesion stretch was 73 +/- 27%, and elastic recoil was 22 +/- 18%, with no variation by etiology of the initial balloon failure. Overall angiographic success (< 50% residual diameter stenosis) was obtained in 49 lesions (98%). Procedural success, defined as < 50% residual diameter stenosis and the absence of major in-hospital complications (death, Q-wave myocardial infarction or emergency bypass surgery), was obtained in 37 of 41 procedures (90%); complications developed in 3 patients (7%), including 2 who needed emergency bypass surgery after development of delayed abrupt closure. It is concluded that rotational coronary atherectomy may be used in selected patients when standard balloon angioplasty is unsuccessful. Its mechanism of benefit appears related, at least in part, to changes in plaque compliance resulting from partial atheroma ablation.

Preliminary experience with adjunct directional coronary atherectomy after high-speed rotational atherectomy in the treatment of calcific coronary artery disease

A high-speed rotational atherectomy was performed followed by adjunct directional atherectomy in 10 patients with symptomatic coronary artery disease and calcified target lesions and the results were evaluated using quantitative coronary arteriography and intravascular ultrasound. Target lesion calcium is common in obstructive coronary artery disease. High-speed rotational coronary atherectomy preferentially abrades noncompliant atherosclerotic plaque material, especially calcium, but often requires adjunct balloon angioplasty to achieve optimal lumen dimensions. Directional coronary atherectomy has limited efficacy in heavily calcified plaque; usually, it is a definitive primary procedure in large arteries with noncalcified target lesions. Neither of these devices alone is effective in treating calcified target lesions in large coronary arteries. Before intervention, after rotational and adjunct directional atherectomy, these measurements were obtained: quantitative coronary arteriographic measurements of minimal lumen diameter and percent diameter stenosis and intravascular ultrasound measurements of external elastic membrane, lumen, and plaque+media cross-sectional areas; percent cross-sectional narrowing; minimal lumen diameter; and target-lesion arc of calcium. With use of quantitative coronary arteriography, the preintervention minimal lumen diameter measured 0.7 +/- 0.4 mm, increased to 1.5 +/- 0.5 mm after rotational atherectomy (p = 0.0013) and to 2.5 +/- 0.3 mm after adjunct directional atherectomy (p < 0.001). The preintervention percent diameter stenosis measured 78 +/- 15%, decreased to 50 +/- 17% after rotational atherectomy (p = 0.0011), and to 17 +/- 11% (p < 0.001) after adjunct directional coronary atherectomy.(ABSTRACT TRUNCATED AT 250 WORDS)