Masahito Moriuchi

Assessment of normal and atherosclerotic arterial wall thickness with an intravascular ultrasound imaging catheter

A prototype intravascular ultrasound imaging catheter with a 20 MHz transducer was used to obtain 59 cross-sectional images in 14 segments of human atherosclerotic arteries. Three distinct components of the arterial wall were visualized on the ultrasound images: a highly reflective intima, an echolucent media, and a moderately reflective adventitia. Images were obtained at 1 mm increments in vitro and were compared with histologic sections at the same levels. Measurements of the arterial layers showed a close correlation between ultrasound images and histologic sections for the thickness of the intimal plaque (r = 0.91), the media (r = 0.83), and the total wall thickness (r = 0.85). The ultrasound images overestimated the mean intimal and total wall thickness by 0.3 mm and 0.7 mm compared to measurements in histologic sections (p less than 0.001). Intravascular imaging with high-frequency ultrasound is an accurate method for measuring microanatomic arterial dimensions and the extent of atheromatous involvement of the arterial wall. This method could represent an important adjunct to traditional angiographic techniques for assessing the severity of atherosclerosis.

Antiischemic effects of nicorandil during coronary angioplasty in humans

SummaryThe present study was undertaken on 10 patients with angina undergoing percutaneous transluminal coronary angioplasty. The angioplasty procedure consisted of two successive 30-second balloon inflations at 5 minute intervals. After the first inflation, nicorandil (0.1 mg/kg) was given intravenously over a 2-minute period. The second inflation was then performed 3 minutes after the completion of drug administration. Myocardial ischemia was measured as the magnitude of ST-segment elevation on the intracoronary electrocardiogram (intracoronary ECG) recorded from the guidewire. Nicorandil significantly reduced the magnitude of ST-segment elevation. Nicorandil did not change the heart rate-blood pressure product, nor the oxygen saturation of the blood sampled from the great cardiac vein, nor the velocity of coronary blood flow in those patients with no evidence of collaterals. These results favor the conclusion that nicorandil prolongs the intrinsic ability of cardiac myocyte to withstand oxygen deprivation. This salutary effect is possibly due to a direct cellular mechanism because nicorandil did not modify the peripheral and coronary hemodynamic parameters that govern myocardial oxygen consumption.

Intravascular ultrasound imaging following balloon angioplasty

Despite its long history and reliability, contrast angiography has several inherent limitations. Because it is a two-dimensional projection image of the lumen contour, the wall thickness cannot be measured and the plaque itself is not visualized. This results in an underestimation of the amount of atherosclerotic disease by angiography. An assessment of atherosclerosis could be improved by an imaging modality: (1) that has an inherent larger magnification than angiography and (2) that directly visualizes the plaque. Intravascular ultrasound fulfils these criteria. This presentation will provide evidence that intravascular ultrasound may prove complimentary or even superior to angiography as an imaging modality.Intravascular ultrasound demonstrates excellent representations of lumen and plaque morphology ofin vitro specimens compared with histology. There is very close intraobserver and interobserver variability of measurements made from intravascular ultrasound images. Phantom studies of stenoses in a tube model demonstrate that angiography can misrepresent the severity of stenosis when the lumen contour is irregular and not a typical ellipse, whereas intravascular ultrasound reproduces the cross-sectional morphology more accurately since it images the artery from within.In vitro studies of the atherosclerotic plaque tissue characteristics compare closely with the echo representation of fibrosis, calcification, and lipid material. In addition,in vitro studies of balloon angioplasty demonstrate that intravascular ultrasound accurately represents the changes in the structure of artery segments following balloon dilatation.

Clinical utility of negative contrast intravascular ultrasound to evaluate plaque morphology before and after coronary interventions

Although intravascular ultrasound (IVUS) is used for evaluation of plaque volume and lumen size as well as detection of vessel wall structures after catheter-based interventions, differentiation between the lumen and plaque structures can be difficult. This study attempted to evaluate the efficacy of negative contrast IVUS imaging for assessment of vessel wall morphology after coronary interventions. IVUS studies were performed in 67 lesions in 66 patients before and after coronary interventions. After the baseline ultrasound imaging run, warm 5% glucose solution was injected manually through the guiding catheter into the coronary artery to washout blood from the lumen to avoid speckled reflections from red blood cells (negative contrast). Quantitative measurements were obtained and plaque morphology was assessed for the presence and extent of medial dissections and intimal flaps. There was no difference in each quantitative parameter between baseline images and negative contrast images. The vessel wall boundary was clearly delineated from the lumen, which was defined as effective negative contrast in 51 of 67 lesions (76%). The baseline images revealed plaque dissection in 9 lesions (18%) and an intimal flap in 13 lesions (25%). In addition, 4 dissections (8%) and 16 intimal flaps (31%) were visualized during the infusion of negative contrast. Additional treatment was performed in 4 lesions (8%) based on the images with negative contrast. Negative contrast IVUS was more sensitive in demonstrating a plaque fracture than were baseline images. This method is useful for enhancing the diagnostic capability of IVUS imaging and may influence the decision-making process during interventional procedures.

Plaque Rupture as a Cause of Apparent Coronary Aneurysm Formation Following Directional Coronary Atherectomy

Late coronary aneurysm formation was observed following treatment by directional coronary atherectomy. Intravascular ultrasound disclosed that the mechanism involved was plaque rupture. The cause of coronary aneurysm may be multifactorial after coronary interventions. Intravascular ultrasound imaging is useful for understanding the pathologic mechanism of coronary aneurysm production.

Sudden Appearance of Coronary Thrombus Observed by Angiography—A Case Report:

A sudden coronary thrombus formation was documented by chance during cardiac catheterization in a patient with postinfarction angina. The thrombus was successfully treated with intravenous urokinase and heparin infusions, and there after, coronary angioplasty was performed without any complication.

Comparative evaluation of atherosclerotic lesions Intravascular ultrasound imaging and pathomorphology

In vitro studies were performed on arterial segments, collected during routine autopsies of 26 male and 8 female adult individuals (mean age, 58 years). A total of 107 segments from the coronary (22 segments), common iliac (34 segments), common carotid (28 segments), renal (20 segments), and other muscular arteries (3 segments) were collected. Ultrasound imaging was performed on unfixed arterial specimens immersed in physiological saline. One cross-sectional image from each specimen was obtained, and the position was marked for subsequent histopathological evaluation. Following ultrasound studies, the specimens were routinely fixed and sections were prepared for microscopic examination. In vivo study consisted of ultrasound images, recorded during the preand postoperative coronary atherectomy of two patients having unstable angina. The atherectomized samples obtained, were routinely fixed and microscopically evaluated. For ultrasound examination, the intravascular imaging device from CVIS, with a 30-MHz transducer mounted at the tip of a 4.3F imaging catheter, was employed.

Contrast echocardiography in a patient with right atrial myxoma

Contrast echocardiography employing intracoronary injection of Albunex was performed in a patient with right atrial myxoma. An echolucent area within the tumor mass was observed on 2-dimensional echocardiography and Albunex injection caused an appreciable opacification of this echolucent area suggesting the presence of a vascular-like structure. This finding was subsequently confirmed by coronary arteriography and from a pathologic specimen.

Anti-ischemic Effects of the ATP-sensitive Potassium Channel Opener During Coronary Angioplasty

Since Gross and co-workers1 found that glibenclamide completely blocked the infarct size-reducing effect afforded by ischemic preconditioning in canine hearts, it has been widely known that the ATP-sensitive potassium (KATP) channel activation plays an important role in myocardial protection against ischemia-reperfusion injury in several species, and a number of laboratories have demonstrated that KATP channel openers such as nicorandil,2 bimakalim,3 and aprikalim1 mimic the cardioprotective effect of ischemic preconditioning.