SUMMARY Among 1800 referred hypertensive patients, 181 had recumbent diastolic blood pressures (DBP) below 90 mm Hg and standing DBP above 90 mm Hg. Orthostatic increments in DBP were greater in these orthostatic hypertensive patients than in 181 persistently hypertensive patients and 134 normotensive subjects. In 12 patients with orthostatic hypertension, the orthostatic fall in cardiac output (27.3 ± 2.9%, measured by a respiratory method) was double that in 8 normotensive subjects (13.3 ± 3.7%, p < 0.01). An inflated pressure suit over the pelvis and lower limbs prevented the excessive fall in cardiac output and significantly reduced (p < 0.02) the excessive rise in standing DBP in orthostatic hypertensive patients. Gravitational pooling of blood in the legs and reduction of blood in the head was measured by external gamma counting of autologous erythrocytes labeled with sodium pertechnetate Tc 99m through ports in fixed positions over the leg and the temple. Orthostatic intravascular pooling was significantly greater (p < 0.01) in orthostatic hypertensive subjects than in normotensive subjects, and the magnitudes of orthostatic pooling and orthostatic increases in DBP were closely correlated (r = +0.85). Plasma norepinephrine concentrations were similar in recumbency and after sustained handgrip exercise, but significantly greater (p < 0.01) after 5 to 60 mins of standing in orthostatic hypertensive subjects than in normotensive subjects. Our results indicate that orthostatic hypertension is common and that its mechanism in representative patients involves excessive orthostatic blood pooling, which results in decreased venous return, decreased cardiac output, increased sympathetic stimulation (presumably through low-pressure cardiopulmonary receptors), and excessive arteriolar, but not venular, constriction. (Hypertension
A portoazygous venous shunt was identified in the caudodorsal aspect of the thorax in a young basset hound. During thoracotomy, the anomalous vessel was encircled with sterile cellophane tape. The vein became occluded based on postoperative radiographic examination and improved clinical function five weeks after surgery.
Simultaneous intraventricular pressure gradients and ejection flow patterns were measured by a multisensor catheter in 6 patients with normal left ventricular function and no valve abnormalities, at rest and in exercise. Peak measured intraventricular pressure gradients were attained very early in ejection, amounted to 6.7 +/- 1.9 (SD) mm Hg at rest, and were intensified to 13.0 +/- 2.3 mm Hg during submaximal supine bicycle exercise. The augmentation of the gradients during exercise was associated with a pronounced accentuation of the flow acceleration and flow at the instant of peak gradient. A peak flow, the intraventricular gradients amounted to 5.4 +/- 1.7 mm Hg at rest and 10.0 +/- 1.8 mm Hg during submaximal exercise. The exercise-induced enhancement of the measured intraventricular pressure difference at the time of peak flow was underlain by an accentuation of the peak flow itself. A semiempirical fluid dynamic model for ejection was applied to the pressure gradient and simultaneous outflow rate and acceleration data to identify the contributions by local and convective acceleration effects to the instantaneous intraventricular gradient values. The peak intraventricular pressure gradient, which is attained very early in ejection, is mostly accounted for by local acceleration effects (85 +/- 5% of the total). Conversely, at peak flow only convective acceleration effects are responsible for the measured pressure gradient. Thus, when inertial effects are augmented, as in exercise and other hyperdynamic states, the intrinsic component of the total left ventricular systolic load can be substantial, even with no outflow tract or valve abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)
The continuity equation suggests that a ratio of velocities at two different cardiac valves is inversely proportional to the ratio of cross-sectional areas of the valves. To determine whether a ratio of mitral/aortic valve orifice velocities is useful in determining aortic valve area in patients with aortic stenosis, 10 control subjects and 22 patients with predominant aortic stenosis were examined by Doppler echocardiography. The ratio of (mean diastolic mitral velocity)/(mean systolic aortic velocity), (Vm)/(Va), and the ratio of (mitral diastolic velocity-time integral)/(aortic systolic velocity-time integral), (VTm)/(VTa), were determined from Doppler spectral recordings. Aortic No. 5, 964-969, 1986. IDENTIFICATION and quantification of aortic stenosis remains a significant problem in adults with systolic murmurs. Cardiac catheterization is frequently required to identify patients with significant aortic stenosis and to quantitate its severity by determining mean systolic pressure gradient and valve area. Doppler echocardiography has proved to be accurate in the identification of patients with aortic stenosis by detecting high velocity's or turbulence-7 in the aorta downstream from the stenotic valve during systole. Doppler determination of the peak systolic velocity allows calculation of the peak instantaneous pressure gradient by means of the simplified Bernoulli equation. 12, 8-l Mean systolic gradient can also be calculated from Doppler velocity recordings by determining the aver-
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