Combined intravascular ultrasound/angioplasty balloon catheter: initial use during PTCA

New developments in intravascular ultrasound

Intravascular ultrasound (IVUS) is a dynamic imaging modality that provides real-time in vivo visualization of atherosclerosis and other vascular pathology. The tomographic image presentation of IVUS permits detailed assessment of plaque morphology and its corresponding responses to interventional therapy. IVUS studies have confirmed vascular remodeling in vivo, have proposed a high-pressure stent implantation strategy and have shown two key mechanisms of restenosis after angioplasty: plaque proliferation and vessel shrinkage (negative remodeling). IVUS also provides accurate quantitative information regarding lumen size, vessel size and plaque burden. These observations, essential to achieving improved outcomes, have drastically changed the understanding of atherosclerotic artery disease and interventional procedures. IVUS has matured into an essential complement to daily peripheral and coronary interventional practice and is routinely incorporated as part of the interventional arsenal in the catheterization laboratory. A variety of new imaging techniques are currently being designed and tested. These include combined therapeutic devices, further miniaturization, 3-D applications and tissue characterization. These techniques may evolve to provide increased favorable clinical outcomes and more accurate information of vessel geometry and plaque composition.

Role of coronary artery lumen enlargement in improving coronary blood flow after balloon angioplasty and stenting: a combined intravascular ultrasound Doppler flow and imaging study

OBJECTIVES

This study sought to examine the mechanism of increasing coronary flow reserve after balloon angioplasty and stenting.

BACKGROUND

Coronary vasodilatory reserve (CVR) does not improve after percutaneous transluminal coronary angioplasty in > or = 50% of patients, postulated to be due to impaired microvascular circulation or inadequate lumen expansion despite adequate angiographic results.

METHODS

To demonstrate the role of coronary lumen expansion, serial coronary flow velocity (0.014-in. Doppler guide wire) was measured in 42 patients before and after balloon angioplasty and again after stent placement. A subset (n = 17) also underwent intravascular ultrasound (IVUS) imaging of the target sites after angioplasty and stenting. CVR (velocity) was computed as the ratio of adenosine-induced maximal hyperemic to basal average peak velocity.

RESULTS

The percent diameter stenosis decreased from (mean +/- SD) 84 +/- 13% to 37 +/- 18% after angioplasty and to 8 +/- 8% after stenting (both p < 0.05). CVR was minimally changed from 1.70 +/- 0.79 at baseline to 1.89 +/- 0.56 (p = NS) after angioplasty but increased to 2.49 +/- 0.68 after stent placement (p < 0.01 vs. before and after angioplasty). IVUS lumen cross-sectional area was significantly larger after stenting than after angioplasty (8.39 +/- 2.09 vs. 5.10 +/- 2.03 mm2, p < 0.05). Anatomic variables were related to increasing coronary flow velocity reserve (CVR vs. IVUS lumen area: r = 0.47, p < 0.005; CVR vs. quantitative coronary angiographic percent area stenosis: r = 0.58, p < 0.0001).

CONCLUSIONS

In most cases, increases in CVR were associated with increases in coronary lumen cross-sectional area. These data suggest that impaired CVR after angioplasty is often related to the degree of residual narrowing, which at times may not be appreciated by angiography. A physiologically complemented approach to balloon angioplasty may improve procedural outcome.

Single device approach to ultrasound-guided percutaneous transluminal coronary angioplasty and stenting: initial experience with a combined intracoronary ultrasound/variable diameter balloon

We evaluated the use of both intracoronary ultrasound (ICUS) information and unique balloon characteristics provided by a combined ICUS/variable diameter balloon catheter during coronary interventions to achieve the maximal residual lumen using the least number of devices. In 47 patients, 64 coronary lesions were treated with either sequential percutaneous transluminal coronary angioplasty (PTCA) (n = 40) or stenting (primary [n = 17], secondary [n = 7]). The result after PTCA was judged satisfactory if the lumen cross sectional area (by ICUS) in the lesion exceeded 65% of the mean reference area. Stent implantation was judged according to revised MUSIC trial criteria. PTCA or stenting was successful in all 64 lesions using 47 combination devices and 10 conventional balloons (mean number of balloons per lesion: 0.90). PTCA group: diameter stenosis decreased from 78 +/- 11 to 23 +/- 13% following inflation at 10.3 +/- 3.0 atm. ICUS lumen area was 4.6 +/- 1.9 mm2 (proximal reference: 7.4 +/- 3.3 mm2, distal reference: 5.7 +/- 1.8 mm2) resulting in a residual area stenosis of 28 +/- 15%. Stent group: diameter stenosis was reduced from 77 +/- 14 to 10 +/- 10% after stenting. ICUS defined minimal lumen area in the stent was 8.2 +/- 2.2 mm2 (proximal reference: 8.7 +/- 2.6 mm2, distal reference: 8.0 +/- 2.2 mm2) resulting in a residual area stenosis of 7.2 +/- 14.6%. No patient death, myocardial infarction, or emergency surgery occurred and only one target lesion required re-PTCA during hospitalization. In conclusion, use of a combined ICUS/variable diameter balloon catheter allows a single device strategy for ICUS-guided PTCA and stenting in the majority (84%) of unselected lesions.

Initial clinical experience with a novel low-profile integrated ultrasound-angioplasty catheter

This report is the first clinical description of the use of a new low-profile integrated ultrasound-angioplasty catheter (the Oracle Micro, Endosonics Corp.), which has recently been approved by the FDA for routine use during percutaneous transluminal coronary angioplasty (PTCA). PTCA was performed in 44 patients at two clinical sites. With this device, PTCA was accomplished in 47 of 55 (85%) lesions ultimately successfully dilated with balloon angioplasty. No major procedural complications occurred. Adequate ultrasound images were obtained in 51 of 57 lesions (89%). Ultrasound imaging revealed significant morphologic information not apparent by angiography in 51% of imaged lesions and altered the dilatation strategy in 33% of cases. In 10 lesions in which greater inflation pressure or balloon upsizing was performed based solely on an inadequate post-PTCA ultrasound appearance, the minimal lumen diameter further increased from 2.3 +/- 0.3 mm to 2.7 +/- 0.5 mm (P < .001), with no dissections or complications. PTCA may be performed safely in the majority of patients currently undergoing balloon angioplasty with a new low-profile integrated ultrasound-angioplasty catheter. Ultrasound imaging during PTCA provides significant information complementary to angiography and may favorably affect the dilatation strategy of experienced operators.

Coronary artery plaque morphology in stable angina and subsets of unstable angina: an in vivo intracoronary ultrasound study

Little information is available regarding the in vivo composition of angina producing culprit atherosclerotic lesions in various anginal syndromes. In this study we used intracoronary ultrasound to determine the composition of culprit lesions in various subsets of anginal syndromes and correlated this composition with the patient's clinical presentation. One hundred and forty six patients referred for angioplasty or atherectomy were classified as having either chronic stable angina (angina which was clinically unchanged for > 2 months), crescendo angina (an accelerating pattern of frequent or prolonged anginal episodes), severe rest angina (abrupt onset of prolonged angina) or post-infarction angina (angina within 2 weeks of acute myocardial infarction). Intracoronary ultrasound imaging of the culprit lesion was performed before intervention. Lesions were classified as soft, mixed fibrous without calcium, mixed fibrous with calcium or calcified. Analysis of the ultrasound images revealed that the majority of culprit lesions were soft in severe rest (71%) and post-infarction angina (73%) whereas, the majority of culprit lesions were mixed fibrous or calcified in chronic stable (69%) and crescendo (53%) angina (X2 = 22.73, p = 0.007). In addition, the frequency of intralesional calcium in chronic stable or crescendo angina was significantly higher than that in severe rest or stable angina. We conclude that the composition of culprit lesions in various anginal subsets are different. The lesion morphology in crescendo angina frequently resembles that in chronic stable angina; while those in severe rest and post-infarction angina are frequently similar. These findings may have implications for medical or interventional treatment of patients with angina.

Correlation of intracoronary ultrasound plaque characteristics in atherosclerotic coronary artery disease patients with clinical variables

It was examined whether intracoronary ultrasound-defined plaque morphology of symptom-producing, severely stenosed, atherosclerotic coronary artery lesions is related to patient-related clinical variables. Data regarding anginal pattern (stable vs unstable), age, sex, history of smoking, diabetes, hypertension, hypercholesterolemia and lesion location were recorded in 146 hemodynamically stable patients referred for clinically indicated balloon angioplasty or directional atherectomy. Intracoronary ultrasound images of the lesions were obtained before and after the intervention. Lesions were classified as soft (homogeneous echoes less dense than adventitia) or hard (bright echoes with or without acoustic shadowing). Eighty-three lesions (57%) were classified as soft and 63 (43%) as hard. Univariate analysis showed anginal pattern, age, vessel location and history of smoking to be significantly related to plaque morphology. Multivariate analysis revealed only anginal pattern, age and vessel location to be independent predictors of plaque morphology. The frequency of echogenic hard plaque was significantly higher in patients aged > 60 years (56 vs 30%; p = 0.001), those with stable angina (69 vs 35%; p = 0.002), and lesions located in the distal arterial segments (68 vs 31%; p < 0.001) than in younger ones, those with unstable angina, and lesions in proximal segments, respectively. Based on previous studies, echogenic hard plaques are likely to be predominantly fibrous or calcific, or both, whereas low-echogenicity soft plaques are likely to be fibrocellular, lipid rich or thrombotic, or a combination. This difference in plaque morphology is probably due to differences in the predominant mechanism of plaque formation (i.e., slow growth vs rupture/thrombosis).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of angiographically successful directional coronary atherectomy: evaluation by intracoronary ultrasound and comparison with transluminal coronary angioplasty

To assess the mechanisms of luminal improvement, 40 patients undergoing directional coronary atherectomy and a matched control group of 25 patients undergoing angioplasty were evaluated with intracoronary ultrasound imaging before and after intervention. Despite similar sized vessels, a similar angiographic severity of diameter stenosis (75 +/- 12% for the angioplasty group vs 69 +/- 15% for the atherectomy group, p = NS), and a similar plaque burden (percent plaque area) before intervention (84 +/- 5% in the angioplasty group vs 85 +/- 13% in the atherectomy group, p = NS), the residual plaque area after intervention was significantly smaller in the atherectomy group (54 +/- 14%) compared with the angioplasty group (65 +/- 13%, p = 0.002). Despite excellent angiographic results, significant residual plaque was noted after either successful intervention. Based on the absolute changes in lumen area, plaque area, and vessel area, improvement in the lumen area in the atherectomy group occurred as a result of plaque "compression" (48%), plaque removal (37%), and vessel expansion (15%). In the angioplasty group, plaque "compression" accounted for 94% of the improvement in lumen area, whereas vessel expansion contributed 6%. Thus "compression" of plaque remains the major mechanism of luminal improvement during atherectomy.

Intracoronary ultrasound imaging: correlation of plaque morphology with angiography, clinical syndrome and procedural results in patients undergoing coronary angioplasty

OBJECTIVES

This study was designed to establish the relation between ultrasound-derived atheroma morphology and the clinical, procedural and angiographic features of patients presenting for coronary angioplasty.

BACKGROUND

Intracoronary ultrasound imaging provides accurate dimensional information regarding arterial lumen and wall structures. Atheroma composition may also be assessed by ultrasound; however, only limited studies have been performed in patients.

METHODS

In 65 patients a diagnostic ultrasound imaging catheter or a combination imaging-angioplasty balloon catheter was used during coronary angioplasty to image both the lesion and the vessel segment just proximal to it (reference segment). Ultrasound images were analyzed for lumen, total vessel and plaque areas and were classified into five morphologic subtypes (soft, fibrous, calcific, mixed plaque and concentric subintimal thickening). These data were compared with angiographic morphologic features, procedural results and clinical angina pattern (stable vs. unstable).

RESULTS

Morphologic analysis of the ultrasound images obtained from the lesion correlated well with the clinical angina syndrome. Compared with patients with stable angina, patients with unstable angina had more soft lesions (74% vs. 41%), fewer calcified and mixed plaques (fibrotic, soft or calcific components in one or more combinations [25% vs. 59%]) and fewer intralesional calcium deposits (16% vs. 45%) (all p < 0.01). There was no correlation between ultrasound and angiographic lesion morphologic characteristics for either the reference segment or the lesion. Ultrasound demonstrated greater sensitivity than angiography for identifying unstable lesions (74% vs. 40%). Dimensional analysis demonstrated a large plaque burden in the reference segments (45 +/- 15% of total vessel area). Postangioplasty plaque burden was also high (62 +/- 9%). There was a significant, but only fair correlation between lumen area determined by angiography and ultrasound for both the reference segment (r = 0.70, p < 0.001) and the postangioplasty lesion (r = 0.63, p < 0.05).

CONCLUSIONS

Morphologic plaque classification by ultrasound is closely correlated to clinical angina but has little relation to established angiographic morphologic characteristics. Intracoronary ultrasound imaging during angioplasty identifies a large residual plaque burden in both the reference segment and the lesion. In the future, determination of plaque composition by intracoronary ultrasound may be important in selecting or modifying interventional therapeutic options.

Use of intracoronary ultrasonography in assessing pharmacotherapy for myocardial ischemia

Intracoronary ultrasonography can provide morphologic and physiologic information on coronary vasomotor responses to pharmacotherapy. Preliminary studies indicate a high correlation between dimensions determined by 2-dimensional echocardiography, angiography, and pathology. Similarly, the emerging data on intracoronary Doppler flow velocity responses beyond atherosclerotic obstructions before, during, and after coronary balloon occlusion will provide further insights into myocardial oxygen supply and its responses to pharmacotherapy during controlled myocardial ischemia.