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Contrast echocardiography has been shown to be a sensitive method for detecting patent foramen ovale in embolic stroke, implying paradoxical embolization. However, not all twodimensional echocardiographic studies are of diagnostic quality, and direct evidence for paradoxical cerebral embolization remains lacking. We addressed these problems by simultaneously using transcranial Doppler ultrasound and contrast echocardiography to compare relative sensitivity and concordance in the detection of right-to-left vascular shunting. Forty-six patients with stroke, transient neurologic defect, or question of atrial septal defect underwent study at rest and during Valsalva strain. Two-dimensional echocardiography detected shunting in 26% at rest and 15% during Valsalva strain, whereas transcranial Doppler study returned rates of 41% and 41%, respectively. Concordance was 82% and 75%, respectively. Discordant studies almost always had evidence of paradoxical contrast embolization by transcranial T he etiology of stroke in more than a third of young adult patients may remain uncertain even after extensive clinical study. 1 Paradoxical embolization via patent atrial foramen ovale has become suspect as a cause of embolic strokes or transient ischemic attacks. "3 Contrast echocardiography with patients at rest and during provocative maneuvers has been shown to be a sensitive method for noninvasively detecting patent foramen ovale in these patients.1 -3 However, not all two-dimensional echocardiographic studies are of diagnostic quality. Moreover, the technique only reveals the substrate for paradoxical embolization; the arterial delivery of emboli originating in the venous system at critical target organs is not demonstrated.The objective of contrast echocardiography in the evaluation of interatrial shunting is the detection of microcavitation gas bubbles entering left heart chambers after intravenous injection. As an alternative to ultrasonic imaging, Doppler ultrasound has served as a sensitive detector of blood-borne gas bubbles in From the University of Oklahoma Health Sciences Center, Cardiology Section, Oklahoma City, Okla.Presented in part at the 61st Scientific Sessions of the American Heart Association.Address for correspondence: Steve M. Teague, MD, MetroHealth Medical Center, 3395 Scranton Road, Cleveland, OH 44109.Received August 14, 1990; accepted February 21, 1991. decompression sickness by demonstrating air bubbles in the pulmonary artery. 4 -7 Specially designed transcranial Doppler devices have been used to detect micro air emboli in the middle cerebral artery during surgery. -9The purpose of this study was to use transcranial Doppler ultrasound as a detector of gas bubbles in the middle cerebral artery simultaneously with two-dimensional apical echocardiography as a detector of bubbles in the left atrium and ventricle so as to compare relative sensitivity and demonstrate concordance in the detection of right-to-left vascular shunting. Subjects and MethodsWe studied 46 consecutive patients referred for contr...

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Epidemiologic studies have shown that airborne particulate matter (PM) with a mass median aerodynamic diameter < 10 µm (PM 10 ) is associated with an increase in respiratory-related disease. However, there is a growing consensus that particles < 2.5 µm (PM 2.5 ), including many in the ultrafine (< 0.1 µm) size range, may elicit greater adverse effects. PM is a complex mixture of organic and inorganic compounds; however, those components or properties responsible for biologic effects on the respiratory system have yet to be determined. During the fall and winter of 2000-2001, healthy adult Sprague-Dawley rats were exposed in six separate experiments to filtered air or combined fine (PM 2.5 ) and ultrafine portions of ambient PM in Fresno, California, enhanced approximately 20-fold above outdoor levels. The intent of these studies was to determine if concentrated fine/ultrafine fractions of PM are cytotoxic and/or proinflammatory in the lungs of healthy adult rats. Exposures were for 4 hr/day for 3 consecutive days. The mean mass concentration of particles ranged from 190 to 847 µg/m 3 . PM was enriched primarily with ammonium nitrate, organic and elemental carbon, and metals. Viability of cells recovered by bronchoalveolar lavage (BAL) from rats exposed to concentrated PM was significantly decreased during 4 of 6 weeks, compared with rats exposed to filtered air (p < 0.05). Total numbers of BAL cells were increased during 1 week, and neutrophil numbers were increased during 2 weeks. These observations strongly suggest exposure to enhanced concentrations of ambient fine/ultrafine particles in Fresno is associated with mild, but significant, cellular effects in the lungs of healthy adult rats.

Aortic regurgitation and mitral stenosis are hemodynamically similar, insofar as both result in passive ventricular filling across a narrow orifice driven by a declining pressure gradient. Because mitral stenosis is successfully characterized by Doppler ultrasound determination of the velocity half-time, or time constant, aortic regurgitation might be quantified in an analogous fashion. Eighty-six patients with diverse causes of aortic regurgitation underwent continuous wave Doppler examination before cardiac catheterization or urgent aortic valve replacement. The Doppler velocity half-time was defined as the time required for the diastolic aortic regurgitation velocity profile to decay by 29%, whereas catheterization pressure half-time was calculated as the time required for transvalvular pressure to decay by 50%. Doppler velocity and catheterization pressure half-times were linearly related (r = 0.91). Doppler velocity half-times were inversely related to regurgitant fraction (r = -0.88). Angiographic severity (1+ = mild to 4+ = severe) was also inversely related to pressure and velocity half-time; a Doppler half-time threshold of 400 ms separated mild (1+, 2+) from significant (3+, 4+) aortic regurgitation with high specificity (0.92) and predictive value (0.90). The Doppler velocity half-time was independent of pulse pressure, mean arterial pressure, ejection fraction and left ventricular end-diastolic pressure. Estimation of transvalvular aortic pressure half-time utilizing continuous wave Doppler ultrasound is a reliable and accurate method for the noninvasive evaluation of the severity of aortic regurgitation.

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Particulate matter (PM) has been associated with a variety of negative health outcomes in children involving the respiratory system and early development. However, the precise mechanisms to explain how exposure to airborne particles may cause adverse effects in children are unknown. To study their influence on early postnatal development, a simple, laminar diffusion flame was used to generate an aerosol of soot and iron particles in the size range of 10 to 50 nm. Exposure of 10-day-old rat pups to soot and iron particles was for 6 h/day for 3 days. The lungs were examined following a single injection of bromodeoxyuridine (BrdU) 2 h prior to necropsy. Neonatal rats exposed to these particles demonstrated no effect on the rate of cell proliferation within terminal bronchioles or the general lung parenchyma. In contrast, within those regions arising immediately beyond the terminal bronchioles (defined as the proximal alveolar region), the rate of cell proliferation was significantly reduced compared with filtered air controls. These findings strongly suggest exposure to airborne particles during early neonatal life has significant direct effects on lung growth by altering cell division within critical sites of the respiratory tract during periods of rapid postnatal development. Such effects may result in altered growth in the respiratory system that may be associated with lifelong consequences.