Takafumi Hiro

Safety and results of dobutamine stress echocardiography in women versus men and in patients older and younger than 75 years of age.

The purpose of this retrospective study was to examine 732 consecutive patients who underwent dobutamine stress echocardiography (DSE) in order to compare the safety and result profiles of this test between women versus men and in patients > or = 75 and < 75 years of age. Our study included 416 women (57%) and 316 men (43%; mean age 62 +/- 12 years [range 16 to 93]). Patients were divided into 3 age groups: (1) group I (n = 179): < 55 years (mean 47 +/- 6), (2) group II (n = 447): 55 to 74 years (mean 64 +/- 5), and (3) group III (n = 106): > or = 75 years (mean 80 +/- 4). DSE was more likely to have negative results in women than in men (prevalence of positivity = 20% vs 31%, p = 0.001), but DSE had a similar safety profile in both genders. Women required lower doses of dobutamine and atropine to reach an end point. There was a similar incidence of test positivity in older and younger patients (23% in group I, 24% in group II, and 30% in group III, p = NS). DSE was generally a safe test in patients > or = 75 years, but there was a different safety profile in the elderly group compared with younger patients--specifically, more frequent asymptomatic hypotension (7% in group I, 13% in group II, and 25% in group III, p = 0.0002) and ventricular arrhythmias (26% in group I, 30% in group II, and 41% in group III, p = 0.04), but less frequent chest pain (32% in group I, 23% in group II, and 17% in group III, p = 0.009). Multivariate analysis suggested that the baseline usage of beta blockers was also a major determinant of the safety and ischemia profile during DSE. In conclusion, there were significant gender- and/or age-specific differences in the safety and test result profile of DSE. These differences should be considered when performing or interpreting DSE, particularly in women and in patients aged > or = 75 years.

Intravascular ultrasound appearance of normal and mildly diseased coronary arteries: correlation with histologic specimens.

Intravascular ultrasound imaging was performed in vitro on six histologically normal and 104 minimally diseased arteries in patients aged 13 to 83 years. This study tested the hypothesis that normal coronary arteries produce a three-layer image that corresponds to the histologic layers of intima, media, and adventitia. The results showed a very good correlation between area of the echolucent ultrasound layer with the media and the inner echogenic layer with intimal area. In addition, a three-layer appearance was consistently seen when the internal elastic membrane was present with or without intimal hyperplasia. If the internal elastic membrane was absent, a three-layer appearance was still seen if the collagen content of the media was low. However, a two-layer appearance was observed when there was absence of the internal elastic membrane as well as a high collagen content of the media.

Angle dependence of intravascular ultrasound imaging and its feasibility in tissue characterization of human atherosclerotic tissue.

BACKGROUND Intravascular ultrasound (IVUS) images vary in intensity because of the angle of the transducer relative to the plaque. The purpose of this study was to determine the angle dependence of ultrasound backscatter when the IVUS transducer is aligned coaxially in atherosclerotic arteries and to examine its feasibility in tissue characterization of human atherosclerotic tissue. METHODS AND RESULTS Thirty-nine noncalcified regions of interest (ROI, 0.4 to 0. 6 mm in diameter) within cross sections of formalin-fixed human iliac arterial plaque were imaged with a 3.9F, 25-MHz IVUS catheter in saline at room temperature. The catheter was moved coaxially from 8 to 16 positions and spanned 50 to 122 degrees relative to the ROI and the lumen center. Echo intensity for each ROI was defined as the videointensity relative to a standard reflector. The angle dependence of echo intensity was defined as the slope of the regression line between the angle of incidence and echo intensity. Each ROI was histologically classified into 4 groups: fibro-acellular (fibrous cap, n=7), fibro-cellular (n=9), fibro-fatty (n=13), or fatty tissue (n=10). The echo intensity of the majority (72%) of plaque components in IVUS images are significantly affected by the angle of incidence of the transducer. The angle dependence of fibro-acellular samples was significantly greater than that of the other 3 groups (4.69 +/- 3.29 x 10(-3) x echo intensity/degree vs 1.06 +/- 1.10 in fibro-cellular area, 2.09 +/- 1.75 in fibro-fatty area, and 2.16 +/- 1.92 in fatty area, P <. 05). CONCLUSIONS The angle dependence of ultrasound reflections from the fibrous cap of atherosclerotic plaque is another method of tissue characterization in addition to spatial distribution and echo intensity. This technique may be useful in determining the thickness of the fibrous cap, which may be an important predictor of plaque rupture.

Measurement of a cross-sectional area of normal and stenotic arteries with videodensitometric quantitative arteriography and intravascular ultrasound

RATIONALE AND OBJECTIVES A videodensitometric technique that allows measurement of absolute cross-sectional area of any complex lesion was compared with an intravascular ultrasound (US) technique. METHODS Stenotic devices (10-15 mm long) with cross sections of different shapes were placed in the distal aortas of five anesthetized pigs (weight, 40-50 kg). The stenotic devices were imaged by using an intravascular US probe after power injection of contrast material. RESULTS A comparison of actual areas and measured cross-sectional areas of the stenotic devices showed that videodensitometry and intravascular US produced better results than edge-detection techniques for both unsubtracted and temporal subtraction images. CONCLUSION These data suggest that the videodensitometric technique can be used to measure absolute cross-sectional areas of arteries with different shapes.