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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The accuracy of measurements of flow velocity determined by using cine MR phase velocity mapping--velocity-encoded cine (VEC) MR--was assessed by comparing VEC MR data with independent measurements in a flow phantom and in human subjects. Constant flow velocities generated in a phantom (range, 20-408 cm/sec) were determined correctly by VEC MR (r = .997, standard error of the estimate [SEE] = 7.9 cm/sec). Peak systolic velocities in the main pulmonary artery determined by VEC MR correlated well with the measurements obtained by using continuous-wave Doppler echocardiography (r = .91). Stroke volumes measured at the aorta by VEC MR and continuous-wave Doppler imaging also correlated well with each other (r = .80). VEC MR measurements of aortic and pulmonary flow provided left and right ventricular stroke volumes that correlated well with left ventricular stroke volumes determined by short-axis cine MR images (r = .98, SEE = 3.7 ml, and r = .95, SEE = 4.8 ml, respectively). Intra- and interobserver variabilities were small for both left and right ventricular stroke volumes as measured with VEC MR. These results indicate that VEC MR accurately and reproducibly measures aortic and pulmonary flow velocities and volumes in the physiologic range of humans, and can be used to measure right and left ventricular stroke volumes under normal flow conditions.
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PMID:Right and left ventricular stroke volume measurements with velocity-encoded cine MR imaging: in vitro and in vivo validation. 204 44

Subcostal pulsed wave Doppler echocardiography of the right ventricular outflow tract was used to assess pulmonary arterial flow at basal conditions and during interventions in 20 patients with chronic obstructive pulmonary disease. The changes in the pulmonary flow induced by interventions ranged from -1.5 l/min to +4.18 l/min (73% to 183% of the basal value). When considered alone, heart rate changes induced by the interventions could explain 53% of the changes in pulmonary flow measured with thermodilution. When Doppler-assessed right ventricular stroke volume changes were also considered the coefficient of determination (R) increased to 77% (r = 0.88, p less than 0.001, SEE = 12%). Doppler echocardiography was less precise in predicting absolute basal values of pulmonary artery flow (r = 0.70, p less than 0.001, SEE = 1.00 l/min), probably indicating inaccurate assessment of the diameter of the right ventricular outflow tract.
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PMID:Simultaneous Doppler and thermodilution assessment of pulmonary artery flow during acute interventions in patients with chronic obstructive pulmonary disease. 211 34

To compare left ventricular filling variables as derived by transmitral pulsed Doppler echocardiography (tpDE) and hemodynamic variables as assessed at right heart catheterization (RHC), 104 ICU patients (64 male, 40 female) aged 26 to 73 yr (mean 54.6 +/- 10.3) without valvular heart disease were examined. Simultaneously with RHC, transmitral flow velocity profiles were obtained by tpDE, and the ratio of the velocity-time integrals of late diastolic active (A wave) and early diastolic passive inflow into the left ventricle (E wave) was calculated (A/E ratio). Invasively determined pulmonary capillary wedge pressure (WP) ranged from 3 to 36 mm Hg (median 13.35, 5%/95% 6/31 mm Hg). Linear regression analysis showed a highly significant correlation between the A/E ratio and WP (r = .98, p less than .001, standard error of the estimate [SEE] = 0.10). The A/E ratio also correlated with other hemodynamic variables such as cardiac output (r = -.68, p less than .001, SEE = 0.33), cardiac index (r = -.74, p less than .001, SEE = 0.31), and stroke volume index (r = -.68, p less than .001, SEE = 0.34). The interobserver agreement (derived by intraclass correlation analysis between two examiners) on the A/E ratio was high (r = .95, p less than .001, n = 26). We conclude that WP can be accurately determined noninvasively by tpDE. For the assessment of systolic ventricular function, tpDE is of limited diagnostic value.
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PMID:Noninvasive determination of pulmonary artery wedge pressure: comparative analysis of pulsed Doppler echocardiography and right heart catheterization. 220 47

A new Doppler pulmonary artery catheter was used to measure instantaneous and continuous cardiac output in both an in vitro model and in 44 patients undergoing cardiac catheterization. Cardiac output was calculated with use of the Doppler catheter-determined instantaneous space-average velocity and the ultrasonically determined instantaneous vessel area. Doppler flow and thermodilution were compared with electromagnetic flow in the in vitro model and with Fick cardiac output in patients. Doppler catheter-determined flow was highly predictive of electro-magnetic flow in the pulsatile flow model (r = 0.99, slope [m] = 1.01 and SEE = 0.05) and appeared comparable to thermodilution measurements (r = 1.00, m = 1.03 and SEE = 0.02). In patients undergoing cardiac catheterization, Doppler catheter-determined cardiac output appeared to modestly underestimate Fick cardiac output (r = 0.82, m = 0.80 and SEE = 0.09; mean error +/- SEM = -0.26 +/- 0.14 liters/min). However, predictive accuracy was comparable to simultaneously obtained thermodilution measurements (r = 0.85, m = 1.07 and SEE = 0.10; mean error +/- SEM = 0.61 +/- 0.16 liters/min). This new Doppler catheter system utilizes multiple ultrasound transducers to provide angle-independent measurements of vessel diameter and instantaneous velocity within the main pulmonary artery, resulting in a more accurate assessment of Doppler-derived cardiac output. In addition, useful information concerning hemodynamic variables such as peak flow, acceleration, deceleration, stroke work and pulmonary impedance may be derived.
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PMID:Instantaneous and continuous cardiac output in humans obtained with a Doppler pulmonary artery catheter. 222 92

Unilateral photochemical infarcts were produced in the hind limb sensorimotor neocortex of 243 rats by intravenous injection of the fluorescein derivative Rose Bengal and focal illumination of the intact skull surface. Facial contact stimuli governed the degree and recovery rate of contralateral tactile/proprioceptive forelimb placing reactions. Contralateral forelimb placing recovered, whereas hind limb placing was resistant to recovery. Infarcted rats displayed marked recovery of spontaneous limb usage (beam traversing). However, deficits in isolated tactile/proprioceptive hind limb placing reactions endured. Posttreatment with the class IV calcium antagonist flunarizine after neocortical infarction protected sensorimotor function in a dose-dependent manner. This protective effect may be due to the peculiar ionic channel blocking profile of flunarizine. Scopolamine hydrobromide reinstated contralateral placing errors in infarcted rats at a dosage that did not affect neurologically intact rats. The cognitive enhancer sabeluzole, a novel benzothiazol derivative, dose-dependently blocked the anticholinergic-induced deterioration of a sensorimotor deficit in rats.
Stroke 1990 Nov
PMID:Ionic channels, cholinergic mechanisms, and recovery of sensorimotor function after neocortical infarcts in rats. 223 75

In a pulsatile in vitro flow model with mounted concentric peripheral arterial stenoses, we compared the mean trans-stenotic pressure difference between pre- and poststenotic segment with the Doppler-estimated mean pressure gradient calculated according to the simplified Bernoulli equation applied over an entire stroke cycle. A close linear correlation was found between Doppler-estimated and invasively measured pressure drop values: Y = 1.13X + 0.47 (r = 0.98, SEE = 1.4 mmHg, n = 16). The Doppler-derived overestimation of the invasively measured mean pressure-drop by an average of 16% (absolute values 2.2 +/- 1.7 mmHg) suggests that in this in vitro model a small part of the kinetic energy of the stenotic jet is recovered distal to the poststenotic turbulences. The difference between both methods is so little that the Doppler-estimated mean pressure drop is acceptable in concentric peripheral model arterial stenoses.
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PMID:[Doppler ultrasound determination of pressure decrease in model peripheral arterial stenoses]. 223 14

Because aortic stenosis results in the loss of left ventricular stroke work (due to resistance to flow through the valve and turbulence in the aorta), the percentage of stroke work that is lost may reflect the severity of stenosis. This index can be calculated from pressure data alone. The relation between percent stroke work loss and anatomic aortic valve orifice area (measured by planimetry from videotape) was investigated in a pulsatile flow model. Thirteen valves were studied (nine human aortic valves obtained at necropsy and four bioprosthetic valves) at stroke volumes of 40 to 100 ml, giving 57 data points. Valve area ranged from 0.3 to 2.8 cm2 and mean systolic pressure gradient from 3 to 84 mm Hg. Percent stroke work loss, calculated as mean systolic pressure gradient divided by mean ventricular systolic pressure x 100%, ranged from 7 to 68%. It was closely related to anatomic orifice area with an inverse exponential relation and was not significantly related to flow (r = -0.15). An orifice formula was derived that predicted anatomic orifice area with a 95% confidence interval of +/- 0.5 cm2 (orifice area [cm2] = 4.82 [2.39 x log percent stroke work loss], r = -0.94, SEE = 0.029). These results support the clinical use of percent stroke work loss as an easily obtained index of the severity of aortic stenosis.
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PMID:Ventricular stroke work loss: validation of a method of quantifying the severity of aortic stenosis and derivation of an orifice formula. 225 47

The determination of ventricular volumes in the fetal heart from two-dimensional echocardiography (2DE) may give a better estimate of fetal ventricular size than simple diameter measurements, but the accuracy of this method has not been established. In fetal lambs, we tested whether ventricular volume calculations from 2DE using a biplane Simpson's rule algorithm are accurate. Calculations of left and right ventricular end-diastolic volumes from 2DE were compared with cast volumes of these ventricles. Also, at different levels of left atrial pressure, left ventricular stroke volumes calculated from 2DE were compared with stroke volumes measured simultaneously by an electromagnetic flowmeter. There was a good correlation between volumes determined from 2DE (y axis) and from casts (x axis) for both the left (r = 0.92; y = 0.2 + 1.1x; SEE = 0.19 ml) and right ventricle (r = 0.90; y = 0.7 + 0.9x; SEE = 0.21 ml). Left ventricular stroke volumes calculated from 2DE correlated well with those measured by the electromagnetic flowmeter (r = 0.87; y = 0.2 + 0.9x; SEE = 0.27 ml). Thus, calculation of fetal ventricular volumes from 2DE images using a biplane Simpson's rule method is feasible and accurate.
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PMID:Two-dimensional echocardiographic determination of ventricular volumes in the fetal heart. Validation studies in fetal lambs. 229 36

The hemodynamic effects on cross-sectional area calculated with the continuity equation were assessed in canine experiments. In 13 open chest dogs, 46 supravalvular aortic stenoses were created by aortic root banding. The cross-sectional area of the stenosis was calculated by Doppler echocardiography with application of the continuity equation before and after the following hemodynamic interventions: protocol 1, atrial pacing at 90, 120, 150 and 180 beats/min after sinus node crush; protocol 2, preload reduction by mild and severe clamping of the inferior vena cava; and protocol 3, afterload augmentation by mild and severe clamping of the descending aorta. In each observation, a dimension of the stenosis was directly measured by two-dimensional echocardiography, and the cross-sectional area was determined as a reference standard. As a result of the hemodynamic interventions, significant changes were observed in stroke volume and pressure gradient (protocol 1), in cardiac output, stroke volume and pressure gradient (protocol 2) and in heart rate, cardiac output and pressure gradient (protocol 3). Despite these changes in hemodynamic variables, the Doppler-derived cross-sectional area showed no significant change for a given stenosis. In addition, areas calculated with the continuity equation (x) agreed well with those determined by two-dimensional echocardiography (y) (r = 0.96, p less than 0.001, y = 0.97x + 0.02, SEE = +/- 0.06 cm2). Thus, it is concluded that Doppler echocardiography with application of the continuity equation accurately predicts the stenotic cross-sectional area over a wide range of hemodynamic conditions in supravalvular aortic stenosis.
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PMID:Doppler echocardiographic quantitation of cross-sectional area under various hemodynamic conditions: an experimental validation in a canine model of supravalvular aortic stenosis. 234 48

The heart is the first functioning organ in the embryo and provides blood flow during cardiac morphogenesis from a muscle-wrapped tube a few cells thick to the four-chambered pump. We described the hemodynamics of the chick embryo from stage 12 (50 hours of a 21-day incubation) to stage 29 (6 days), during which the embryo weight increased 120-fold. We measured ventricular, embryo and extraembryonic vascular bed wet weights, dorsal aortic blood flow with a directional pulsed-Doppler velocity meter, and ventricular and vitelline arterial blood pressures with a servo-null micropressure system. The data are reported as mean +/- SEM. With rapid development and morphogenesis, dorsal aortic blood flow increased from 0.015 +/- 0.004 to 2.40 +/- 0.20 mm3/sec parallel to the geometric increase of wet embryo weight from 2.22 +/- 0.10 to 267.5 +/- 9.7 mg. Dorsal aortic blood flow normalized for embryo and extraembryonic weight remained relatively constant (Y = 2.13 + 0.02X, r = 0.23, SEE = 0.03). Stroke volume increased from 0.01 +/- 0.003 to 0.69 +/- 0.03 mm3, and heart rate doubled from 103 +/- 2 to 208 +/- 5 beats/min. Systolic, diastolic, and mean vitelline arterial pressure increased linearly from 0.32 +/- 0.01, 0.23 +/- 0.01, and 0.28 +/- 0.01 mm Hg at stage 12 to 2.00 +/- 0.06, 1.22 +/- 0.03, and 1.51 +/- 0.04 mm Hg, respectively, at stage 29. Ventricular peak systolic and end-diastolic pressure increased from 0.95 +/- 0.04 and 0.24 +/- 0.02 at stage 12 to 3.45 +/- 0.10 and 0.82 +/- 0.03 at stage 29, respectively. The hemodynamic waveforms were similar to those found in the four-chamber heart of the mature animal. These data are integral to understanding the interrelation of function and form during cardiac development.
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PMID:Hemodynamics of the stage 12 to stage 29 chick embryo. 258 95


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