Coronary stenting with angioscopic guidance

Imaging of intracoronary thrombus

The identification of intracoronary thrombus and atherothrombosis is central to the diagnosis of acute myocardial infarction, with the differentiation between type 1 and type 2 myocardial infarction being crucial for immediate patient management. Invasive coronary angiography has remained the principal imaging modality used in the investigation of patients with myocardial infarction. More recently developed invasive intravascular imaging approaches, such as angioscopy, intravascular ultrasound and optical coherence tomography, can be used as adjunctive imaging modalities to provide more direct visualisation of coronary atheroma and the causes of myocardial infarction as well as to improve the sensitivity of thrombus detection. However, these invasive approaches have practical and logistic constraints that limit their widespread and routine application. Non-invasive angiographic techniques, such as CT and MRI, have become more widely available and have improved the non-invasive visualisation of coronary artery disease. Although they also have a limited ability to reliably identify intracoronary thrombus, this can be overcome by combining their anatomical and structural characterisation of coronary anatomy with positron emission tomography. Specific radiotracers which bind with high specificity and sensitivity to components of thrombus, such as activated platelets, fibrin and factor XIIIa, hold promise for the non-invasive detection of intracoronary thrombus. The development of these novel non-invasive approaches has the potential to inform clinical decision making and patient management as well as to provide a non-invasive technique to assess the efficacy of novel antithrombotic therapies or interventional strategies. However, these have yet to be realised in routine clinical practice.

Usefulness of intracoronary angioscopy for elucidating the cause of subacute thrombosis after stenting

Stent thrombosis is rare with anti-platelet therapy, which consists of aspirin and ticlopidine as a post-stenting administration. A 77-year-old man had repeated stent thrombosis, which was not predicted by coronary angiography, despite using contemporary periprocedural anti-platelet therapy. Only intravascular fiberscopy was able to detect the cause of the stent thrombosis.

Angioscopy

Angioscopy provides a magnified, real-time, 360-degree view of the endoluminal surface of blood vessels, yielding unique information that is often complementary to conventional angiography. This unique perspective can significantly enhance one's perception and appreciation of endovascular disease. Although angioscopy is primarily used as a research tool, its ability to characterize accurately the morphology and color of atherosclerotic lesions may lead to improved treatment and better clinical outcomes.

Chromatic distortion during angioscopy: assessment and correction by quantitative colorimetric angioscopic analysis

Angioscopy represents a diagnostic tool with the unique ability of assessing the true color of intravascular structures. Current angioscopic interpretation is entirely subjective, however, and the visual interpretation of color has been shown to be marginal at best. The quantitative colorimetric angioscopic analysis system permits the full characterization of angioscopic color using two parameters (C1 and C2), derived from a custom color coordinate system, that are independent of illuminating light intensity. Measurement variability was found to be low (coefficient of variation = 0.06-0.64%), and relatively stable colorimetric values were obtained even at the extremes of illumination power. Variability between different angioscopic catheters was good (maximum difference for C1, 0.022; for C2, 0.015). Catheter flexion did not significantly distort color transmission. Although the fiber optic illumination bundle was found to impart a slight yellow tint to objects in view (deltaC1 = 0.020, deltaC2 = 0.024, P < 0.0001) and the imaging bundle in isolation imparted a slight red tint (deltaC1 = 0.043, deltaC2 = -0.027, P < 0.0001), both of these artifacts could be corrected by proper white balancing. Finally, evaluation of regional chromatic characteristics revealed a radially symmetric and progressive blue shift in measured color when moving from the periphery to the center of an angioscopic image. An algorithm was developed that could automatically correct 93.0-94.3% of this error and provide accurate colorimetric measurements independent of spatial location within the angioscopic field. In summary, quantitative colorimetric angioscopic analysis provides objective and highly reproducible measurements of angioscopic color. This technique can correct for important chromatic distortions present in modern angioscopic systems. It can also help overcome current limitations in angioscopy research and clinical use imposed by the reliance on visual perception of color.

Angioscopic evaluation of angiographically complex coronary lesions

Coronary angioscopy (CA) provides direct visualization of the endoluminal surface of coronary vessels. The usefulness of CA during coronary angioplasty of angiographically complex lesions remains to be established. This study was designed to determine the value of CA to elucidate the underlying substrate of angiographically complex lesions. Forty-seven consecutive patients with angiographically complex lesions were studied with CA before coronary intervention. Mean age of the group was 59 +/- 9 years; six patients were women. Forty (85%) patients had unstable angina. Complex angiographic lesions included coronary occlusions (n = 23) (14 with Thrombolysis in Myocardial Infarction coronary flow grade 0 and nine with flow grade 1), lesions with intraluminal filling defects suggestive of thrombus or ulceration (n = 8), and lesions that were highly eccentric (n = 16). Items analyzed with CA included red thrombus (lining or protruding) and plaque color (yellow, white, or mixed). In all patients, CA visualized the protruding material causing the angiographic appearance. At this site CA detected red thrombus in 34 (72%) patients (14 protruding, 20 lining) and atherosclerotic plaque in 45 (96%) patients. At the site of the angiographically complex lesion, plaque was classified as predominantly yellow in 24 patients, mixed in 12, and white in nine. The incidence of thrombus on CA was higher for occluded vessels (91%) or lesions with intraluminal filling defects or ulceration (87%) than in eccentric lesions (37%) (p < 0.05). However, plaque coloration was not significantly different among these three angiographic subgroups. Initial procedural success (without stent requirement) was lower in lesions showing protruding thrombus on CA (64% vs 91 %, p < 0.05). Thus most angiographically complex lesions contain thrombus. On CA red thrombus was more frequently identified on occluded vessels and lesions with filling defects or ulceration than in eccentric lesions. Yellow or mixed plaques are common in these patients, suggesting lipid-laden plaques as the underlying pathologic substrate of angiographically complex lesions.

Ultrasound cardioscopy: embarking on a new journey

OBJECTIVE

To present the results of investigation of a new application of invasive ultrasonography-ultrasound cardioscopy, a procedure in which a self-contained ultrasound device is capable not only of producing an under-blood field of view but also of delivering diagnostic and therapeutic tools.

DESIGN

Twenty adult mongrel dogs were studied with the ultrasound cardioscopy device during experimental catheter ablation procedures.

MATERIAL AND METHODS

A rigid prototype probe, 34 cm long and 8 mm in diameter with a 7-MHz side-viewing transducer at the tip and an 8-F diameter tool delivery port, was introduced through the right external jugular vein into the right heart chambers. Remote and device-directed ablation procedures were monitored. Subsequently, the canine hearts were excised and examined.

RESULTS

The self-contained cardioscopy device with a contained ablation catheter could both direct and visualize a specified ablation injury. Under-blood observation of the details of the ablation procedure was possible. Although a learning curve existed for appropriate manipulation of the device, inspection of the excised hearts showed that the size of the injury was accurately predicted with use of ultrasound cardioscopy.

CONCLUSION

Ultrasound cardioscopy is a promising means of performing precise under-blood diagnostic and therapeutic maneuvers.

Transcatheter therapy of thrombotic-occlusive lesions in saphenous vein grafts

Saphenous vein graft (SVG) disease, a form of accelerated atherosclerosis, remains a therapeutic conundrum. The use of stents after excluding the presence of thrombus has proved highly successful at short- and long-term follow-up. We report on 60 severely symptomatic patients with multiple subtotal and total thrombotic SVG occlusions who were treated with a combination of intragraft urokinase-verapamil infusion and insertion of multiple biliary stents. Stent deployment had a 100% success rate. No case of clinical subacute thrombosis was registered, and major in-hospital complications were uncommon (<1%). The clinical outcome was encouraging, with a 12-month event-free survival rate of 87% in the 57 evaluable patients. This method of therapy appears to be highly successful in the treatment of thrombus-containing occlusive SVG disease, in preventing the "no-reflow" phenomenon, and in lessening the incidence of periprocedural non-Q-wave myocardial infarction.