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

We investigated the criteria for the coupling of the left ventricle (LV) and the arterial system to maximize LV stroke work (SW) and the transformation of LV pressure-volume area (PVA) to SW. We studied eight conscious dogs that were instrumented to measure LV pressure and determine LV volume from three ultrasonically determined dimensions. The LV end-systolic pressure (PES)-volume (VES) relation was determined by caval occlusion. Its slope (EES) was compared with the arterial elastance (EA) and determined as PES per stroke volume. At rest, with intact reflexes, EES/EA was 0.96 +/- 0.20 EES/EA was varied over a wide range (0.18-2.59) by the infusion of graded doses of phenylephrine and nitroprusside before and during administration of dobutamine. Maximum LV SW, at constant inotropic state and end-diastolic volume (VED), occurred when EES/EA equaled 0.99 +/- 0.15. At constant VED and contractile state, SW was within 20% of its maximum value when EES/EA was between 0.56 and 2.29. The conversion of LV PVA to SW increased as EES/EA increased. The shape of the observed relations of the SW to EES/EA and SW/PVA to EES/EA was similar to that predicted by the theoretical consideration of LV PES-VES and arterial PES-stroke volume relations. We conclude that the LV and arterial system produce maximum SW at constant VED when EES and EA are equal; however, the relation of SW to EES/EA has a broad plateau. Only when EA greatly exceeds EES does the SW fall substantially. However, the conversion of PVA to SW increases as EES/EA increases. These observations support the utility of analyzing LV-arterial coupling in the pressure-volume plane.
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PMID:Left ventricular-arterial coupling in conscious dogs. 185 32

Renal blood flow dynamics were studied with color and pulsed Doppler ultrasound in 102 normal fetuses at 20 to 40 weeks of gestation, 11 growth retarded fetuses (group A), 15 fetuses with oligohydramnios (group B) and 10 growth retarded and oligohydramniotic fetuses (group C) at 32-40 weeks of gestation. The maximum systolic velocity (VMAX), early diastolic peak velocity (VEA), end diastolic velocity (VED) and resistance index (RIEA:VMAX-VEA/VMAX and RIED:VMAX-VED/VMAX) were measured in the renal artery. VMAX was also measured in the ascending aorta (AO) and pulmonary artery (PA). In the normal fetuses, blood flow velocity increased with gestational age, but VMAX and VEA remained constant after 28 weeks of gestation. The resistance index decreased with gestational age, but RIEA remained constant after 28 weeks of gestation. RIED in groups A and C increased significantly, and VMAX in groups B and C, and VED in group C decreased significantly compared with normal fetuses. VMAX in AO and PA decreased remarkably in the three abnormal groups. It was concluded that the kidneys were poorly perfused in the growth retarded fetuses with oligohydramnios, which may, in part, depend on the decreased stroke volume.
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PMID:[Evaluation of the renal artery in the fetuses with growth retardation and oligohydramnios by two dimensional Doppler ultrasonography]. 194 May 53

We assessed the effect of alcohol, before and after autonomic blockade, on left ventricular (LV) performance in conscious dogs. 10 animals were instrumented to determine LV volume from ultrasonic LV internal dimensions and measure LV pressure with a micromanometer. The animals were studied in the conscious state after full recovery from the operation. Blood alcohol was undetectable before and 67 +/- 14 mg/dl (mean +/- SD) at 20 min after alcohol administration. In response to alcohol, the LV systolic pressure was reduced slightly, the left ventricular end-diastolic pressure increased slightly. The maximum time derivative of LV pressure (dP/dtmax) and stroke volume were decreased. The end-systolic volume (VES), as well as effective arterial elastance, were significantly increased. There was no significant change in heart rate. Variably loaded pressure-volume loops were generated by acute caval occlusion before, immediately, and 20 min after the intravenous infusion of alcohol (0.2 g/kg). Three measures of LV performance were derived from these variably loaded pressure-volume loops: the end-systolic pressure-volume relation; the stroke work-end-diastolic volume relation; and maximum dP/dt-VED relation. The slopes of all three relations were significantly decreased in response to alcohol, and all three relations were shifted toward the right, indicating a depression of LV contractile performance. Similar, but greater depressions of LV performance with alcohol were observed following autonomic blockade. LV performance was restored by infusing dobutamine. We conclude that mildly intoxicating levels of alcohol (blood concentration less than 100 mg/dl) are capable of producing LV contractile depression in conscious animals, which is more marked after autonomic blockade. This suggests that patients with impaired LV function should avoid even small amounts of alcohol.
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PMID:Acute effects of mildly intoxicating levels of alcohol on left ventricular function in conscious dogs. 234 16

Three measures of left ventricular (LV) performance derived from pressure (P)-volume (V) loops have been proposed: the end-systolic P-V (PES-VES) relation, the stroke work-end-diastolic V (SW-VED) relation, and maximum dP/dt-VED (dP/dtmax-VED) relation. We evaluated the variability of repeated determinations, and inotropic and load sensitivity of these relations in conscious dogs. LVV was determined from three orthogonal LV diameters measured by sonomicrometry. Three to six sets of variably loaded P-V loops were generated by transient caval occlusions before and again after increasing inotropic state by infusing dobutamine (6 +/- 1 microgram/kg/min, mean +/- SD) and after increasing PES by 49 +/- 17 mm Hg with phenylephrine following autonomic blockade. The slope (MSW) of the SW-VED relation was the least variable at constant inotropic state (coefficient of variation, 4 +/- 3%) compared with the slope (EES) of the PES-VES relation (8 +/- 3%) or the slope (dE/dtmax) of the dP/dtmax-VED relation (11 +/- 6%, p less than 0.05). The extrapolated volume-axis intercept of the SW-VED relation was much less variable than the intercepts of the PES-VES or dP/dtmax-VED relations. MSW, EES, and dE/dtmax all increased (p less than 0.05) in response to dobutamine. The extrapolated volume-axis intercepts of the PES-VES and dP/dtmax-VED relations increased with dobutamine, whereas the volume intercept of the SW-VED relation was unchanged. MSW had the smallest increase in response to dobutamine (124 +/- 22% of control) compared to EES (178 +/- 67% of control) and dE/dtmax (211 +/- 68% of control, p less than 0.05). The position of the PES-VES relation, quantified as the VES at PES = 100 (V100), showed less variability (2 +/- 1%) than the slope of the PES-VES relation (8 +/- 3%, p less than 0.05). V100 decreased from 30.8 +/- 17.4 to 26.7 +/- 13.7 ml during dobutamine (p less than 0.05). After phenylephrine, EES, MSW, and dE/dtmax decreased by less than 10% (p = NS). The PES-VES relation shifted to the left with this increased afterload and V100 decreased by 3.2 +/- 1.5 ml (p less than 0.05), whereas the position of the SW-VED and dp/dtmax-VED relations were relatively unchanged.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Comparison of measures of left ventricular contractile performance derived from pressure-volume loops in conscious dogs. 280 73

We investigated the coupling of the left ventricle (LV) and the arterial system in eight conscious dogs, instrumented to measure LV pressure and determine LV volume from three ultrasonically determined dimensions. The LV end-systolic pressure (PES)-volume (VES) relation was determined by caval occlusion. Its slope (EES) was compared to the arterial elastance (EA), determined as PES/stroke volume. At rest, with intact reflexes, EES/EA was 0.9 +/- 0.20. EES/EA was varied over a wide range (0.18-2.59) by the infusion of graded doses of phenylephrine and nitroprusside and dobutamine. Maximum LV SW, at constant inotropic state and end-diastolic volume, occurred when EES/EA = 0.99 +/- 0.15. However, SW was within 20% of its maximum value when EES/EA was between 0.56 and 2.29. As EES/EA decreased below 0.59, SW fell precipitously. The shape of the observed relation of SW to EES/EA was similar to that predicted by the theoretical consideration of linear LV PES-VES and arterial PES-stroke volume relations. We conclude that the LV and arterial system produce maximum SW at constant VED when EES and EA are equal; however, the relation of SW to EES/EA has a broad plateau.
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PMID:Coupling of the left ventricular and arterial system. 802 18

We compared the effects of three dihydropyridine calcium antagonists (felodipine, nifedipine and amlodipine) on left ventricular (LV) contractile performance and diastolic filling dynamics in eight conscious animals. After administering metoprolol and atropine, felodipine (25 nmol/kg i.v.) produced significant decreases in LV end-systolic pressure (PES) (109 +/- 15 vs. 88 +/- 12 mmHg, P < .05) and arterial elastance (Ea) (12.6 +/- 4.5 vs. 8.5 +/- 3.4 mmHg/ml, P < .05), whereas the heart rate was unchanged. Felodipine increased the slopes of the end-systolic P-V relation (7.4 +/- 0.9 vs. 9.9 +/- 1.0 mmHg/ml, P < .05), the dP/dtmax-end diastolic volume (VED) relation (68.1 +/- 11.2 vs. 94.9 +/- 14.3 mmHg/sec/ml, P < .05), and the stroke work (SW)-VED relation (72.1 +/- 3.1 vs. 82.8 +/- 5.2 mmHg, P < .05), and shifted all three relations to the left, indicating enhanced contractile performance. In contrast, at doses that produced equivalent reductions of PES, nifedipine (375 nmol/kg i.v.) and amlodipine (780 nmol/kg i.v.), significantly decreased the slopes of the end-systolic P-V relation, the dP/dtmax-VED relation and the SW-VED relation and shifted all three relations to the right, indicating depressed LV contractile performance. Felodipine decreased the time constant (T) of LV relaxation (32.2 +/- 5.2 to 28.8 +/- 5.2 msec, P < .05) and increased the maximum rate of early diastolic LV filling (dV/dtmax) (167 +/- 22 to 207 +/- 26 ml/sec, P < .05). Amlodipine had the opposite effect, slowing T (31.0 +/- 4.9 to 33.9 +/- 5.4 msec, P < .05) and decreasing dV/dtmax (173 +/- 39 to 154 +/- 30 ml/sec, P < .05), whereas nifedipine had no significant effects on T, PGmax or dV/dtmax. Thus, we conclude that in conscious dogs after autonomic blockade, at dosages that produced equivalent arterial vasodilation, felodipine augmented, whereas amlodipine depressed, LV contractile performance, LV relaxation and early LV filling. Nifedipine decreased LV contractile performance but had no significant effect on LV relaxation and early LV filling.
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PMID:Comparison of effects of dihydropyridine calcium antagonists on left ventricular systolic and diastolic performance. 813 36

We assessed the effect of arginine vasopressin (AVP) on left ventricular (LV) performance in eight conscious dogs. Five minutes after AVP infusion (6 microns.kg-1 x min-1 for 2 min) the plasma AVP was elevated from 3.9 +/- 0.9 to 14.7 +/- 4.6 pg/ml (P < 0.05). With all reflexes intact, AVP caused significant increases in LV end-systolic pressure (P) (112 +/- 8 vs. 122 +/- 7 mmHg, P < 0.05) end-systolic volume (V) (30 +/- 5.8 vs. 38 +/- 7.7 ml, P < 0.05), total systemic resistance (6.2 +/- 1.8 vs. 10.6 +/- 4.0 mmHg.dl-1 x min, P < 0.01) and arterial elastance (Ea) (6.8 +/- 3.0 vs. 8.6 +/- 3.9 mmHg/ml, P < 0.05), while the heart rate (110 +/- 6 vs. 82 +/- 10 beats/min, P < 0.05) and stroke volume (16.5 +/- 4.3 vs. 14.2 +/- 3.9 ml, P < 0.05) were decreased. There was no significant change in the coronary sinus blood flow (82 +/- 19 vs. 78 +/- 22 ml/min, P = not significant). AVP decreased the slopes of LV end-systolic P-V relation (10.7 +/- 1.1 vs. 8.1 +/- 1.9 mmHg/ml, P < 0.05), the maximal first derivative of LV pressure (dP/dtmax)-end-diastolic volume (VED) relation (135.2 +/- 18.7 vs. 63.1 +/- 7.7 mmHg.s-1 x ml-1, P < 0.05), and the stroke work-VED relation (81.1 +/- 4.1 vs. 66.7 +/- 2.8 mmHg, P < 0.05) and shifted the relations to the right, indicating a depression of LV performance. A similar increase in Ea produced by methoxamine did not depress LV performance.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of vasopressin on left ventricular performance. 843 Aug 61

Left ventricular (LV) short- and long-axis contractile function and LV structural changes were serially measured in eight instrumented dogs during the development of congestive heart failure (CHF) induced by rapid right ventricular (RV) pacing. After 10 days of pacing, LV end-diastolic volume (VED) had not increased; however, the slope of LV end-systolic pressure-volume relation had decreased from 7.4 +/- 2.6 to 4.9 +/- 1.1 mmHg/ml (P < 0.05), and the slope of LV stroke work-VED relation had fallen from 78.4 +/- 9.1 to 64.2 +/- 7.2 mmHg (P < 0.05). The slopes of end-systolic pressure-dimension relation and the stroke work area-end-diastolic dimension relation in the short axes (i.e., anteroposterior and septal-lateral) had decreased by 30% (P < 0.05), whereas the slopes of the long-axis (i.e., apical-basal) relations were unchanged (not significant). After 20 days of pacing, VED had significantly increased by 14% due to selective dilation of the short axes by 7%, and LV global contractility had further declined with a 40% contractile depression in the short axes and a 25% contractile depression in the long axis. After 30 days, the long-axis dimension at end diastole was also significantly increased with a further increase in the short-axis dimensions. In contrast to the spherical dilation occurring during CHF, acute volume loading of normal animals produced symmetrical LV dilation. These observations suggest that heterogeneous contractile depression initiates the spherical end-diastolic chamber dilation in pacing-induced CHF.
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PMID:Left ventricular spherical dilation and regional contractile dysfunction in dogs with heart failure. 932 89

We prospectively compared the accuracies of conventional transcranial Doppler ultrasound (TCD) and transcranial color-coded duplex sonography (TCCS) in the diagnosis of narrowing of the basilar (BA) and vertebral arteries (VA). Fifty-six consecutive patients (mean age 55.8 years; 34 women) after subarachnoid hemorrhage (n=46), stroke or transient ischemic attack (n=5), and for other reasons (n=5) underwent on the same day TCD, TCCS and the intra-arterial digital subtraction angiography (DSA) - the reference standard. The accuracy of peak-systolic (VPS), mean (VM), and end-diastolic velocities (VED) in detection of any arterial narrowing was estimated using the receiver operator characteristic (ROC) curve methodology and the total area (Az) under the curve. Accuracy of TCCS in detection of VA narrowing based on VPS and VM measurements was significantly higher than accuracy of TCD (Az=0.65 for VPS and Az=0.62 for VM versus Az=0.51 and Az=0.50, respectively, p<0.05 for both). Accuracy of TCCS in detection of BA narrowing was also higher than accuracy of TCD based on VPS measurements (Az=0.69 versus Az=0.50, respectively), with a trend toward significant difference, p=0.085. The accuracy of TCCS is superior to accuracy of TCD in detection of narrowings of vertebral and basilar arteries, thus TCCS should be preferred in routine clinical practice.
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PMID:Vertebral and Basilar Arteries: Transcranial Color-Coded Duplex Ultrasonography versus Conventional TCD in Detection of Narrowings. 2402 84