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Retinal vein occlusion and thrombophilia
326
RESONANCE
Roberto
EXPLAINS FLOW OSCILLATIONS IN THE TERMINAL AORTA
Bumttini*“,
Silvia
Natalucci’
and Kenneth
B. CampbclP
(*)Dept. of Electortics and Automatica, University ofAnc”na 60131 Ancona. Italy. (“) Dept. of Veterhtary and Comparative Anatomy l%rmacology and physiology, Washington State University, Pullman, WA 99164-6520. Previous studies of arterial wave transmission. including our own using an asymmetric T-tube arterial model [Am J. Physiol. 264 (Heart Cira. Physiol 33): H1977-H1987, 19931. have identified an efFecti%! Wave reflection site in the terminal aorta lxtween the origin of the renal arteries and the sonic bifurcation. In a later study [Ann Biomed Eng. 22: 381-391, 19941 we found that a lumped model (inertawe-viscoelastic windkessel. IVW), accounting for both inertial and viscoelastic properties of circulation, was a suitable representation of the terminal aortic circulation, In this model a” inertaxe, L, is connected in series with a vtioelastic windkessel, that consists of a peripheral resistance, &. connected in parallel with a Voigt cell (a resistor, &, in series with a capacitor. C) to account for viscoelasticity. Interactions between inertance and compliance may lead to resonance. so that it becomes important to evaluate the related osciIlatory phenomena and their impact on pressure and flow dynamics. To tbii aim, we applied “UC IVW model to pressure and flow measurements taken from the terminal aona of three anaesthetised open-chest dogs, under basal, vasodilated and vasoconstricted conditions. Our model described prominent flow oscillations, from midsystole to diastole, and allowed us to interpret these oscillations in terms of resonance that occurs at a frequency, f, where reactance of ioertance of blood motion matches the reactance of arterial compliance. We found that viscoelaslicity modulates resonance since a) with increasing pressure from 40 to 140 mmHg, our estimates of f, increased from 2.4 to IO Hz and showed a correlation with values of static elastic moduli reporred bj Del-gci ii. Phykd. 156: 445.457, 19611. and bi viwx~s lurxa. F& of arterial wall motion limited the amplitude of resonance peak. Resonance is a physiologically important phenomenon in need of evaluation and interpretation of flow’s oscillatory pbenomcna as they impact a) wave propagation along the descending thoracic aorta, and b) the shearing force imposed on the aortic wall and its endothelial Lining, that can affect the functional and structural integrity of the endothelial cells.
RETINAL
VEIN
OCCLUSION
AND
THROMEOPHILIA
A.Sagripanti,M.P.Bartolomei*,L.Evangelisti, A.Carpi**, R.Giordani, M.Nardi*. Internal Medicine Dept., Ophthalmology ctive Age Dept.**, University Hospital,
V.Poggi: Unit*, Pisa,
ReproduItaly.
Occlusion of the central vein or peripheral branches of the retinal venous system is a common cause of impaired vision in adult patients. The pathogenesis ofretinalvein occlusion still remains a matter of debate: generalized blood coagulation alterations are likely tobe involved. We have measured plasma indicators of thrombophilia (re cognized to predispose to venous thrombosis of the lower limbs),including antithrombin III, protein C, protein S, activated protein C resistance, lipoprotein (a), folate, IgGti IgManticardiolipin antibodies, in a series of 33 patients (15 males and 18 females,aged 32 to78 years) co; secutively referred to theOphthalmology UnitofourHospita.1 with an established diagnosis of retinal vein occlusion. The following abnormalities have been found (no= number of patients): protein C deficiency ((70 U/dl) n'l; protein S deficiency (C70 U/dl) nO1: activated protein C resistance (ratio t2) n"5; high lipoprotein (a) (>30mg/dl) no 2; low folic acid ((2 rig/ml) n"3. Antithrombin III plasma levels ranged from 85 to 127 U/d1 (mean 103,7 Wdl): no individual exhibited positive anticardiolipin ant-es. Out of the 33 patients 19 exhibited total cholesterol serum levels >220 mg/dl, and 13 presented plasma fibrinogen concentrations >350 mg/dl. To summarize, 12 of 33 unselected patients affected with retinal vein occlu sion (36%) displayed plasma abnormalities, either inherited or acquired, predisposing to venous thrombosis; these alteration may have been implicated in the pathogenesis of the acute event.
RESONANCE
Roberto
EXPLAINS FLOW OSCILLATIONS IN THE TERMINAL AORTA
Bumttini*“,
Silvia
Natalucci’
and Kenneth
B. CampbclP
(*)Dept. of Electortics and Automatica, University ofAnc”na 60131 Ancona. Italy. (“) Dept. of Veterhtary and Comparative Anatomy l%rmacology and physiology, Washington State University, Pullman, WA 99164-6520. Previous studies of arterial wave transmission. including our own using an asymmetric T-tube arterial model [Am J. Physiol. 264 (Heart Cira. Physiol 33): H1977-H1987, 19931. have identified an efFecti%! Wave reflection site in the terminal aorta lxtween the origin of the renal arteries and the sonic bifurcation. In a later study [Ann Biomed Eng. 22: 381-391, 19941 we found that a lumped model (inertawe-viscoelastic windkessel. IVW), accounting for both inertial and viscoelastic properties of circulation, was a suitable representation of the terminal aortic circulation, In this model a” inertaxe, L, is connected in series with a vtioelastic windkessel, that consists of a peripheral resistance, &. connected in parallel with a Voigt cell (a resistor, &, in series with a capacitor. C) to account for viscoelasticity. Interactions between inertance and compliance may lead to resonance. so that it becomes important to evaluate the related osciIlatory phenomena and their impact on pressure and flow dynamics. To tbii aim, we applied “UC IVW model to pressure and flow measurements taken from the terminal aona of three anaesthetised open-chest dogs, under basal, vasodilated and vasoconstricted conditions. Our model described prominent flow oscillations, from midsystole to diastole, and allowed us to interpret these oscillations in terms of resonance that occurs at a frequency, f, where reactance of ioertance of blood motion matches the reactance of arterial compliance. We found that viscoelaslicity modulates resonance since a) with increasing pressure from 40 to 140 mmHg, our estimates of f, increased from 2.4 to IO Hz and showed a correlation with values of static elastic moduli reporred bj Del-gci ii. Phykd. 156: 445.457, 19611. and bi viwx~s lurxa. F& of arterial wall motion limited the amplitude of resonance peak. Resonance is a physiologically important phenomenon in need of evaluation and interpretation of flow’s oscillatory pbenomcna as they impact a) wave propagation along the descending thoracic aorta, and b) the shearing force imposed on the aortic wall and its endothelial Lining, that can affect the functional and structural integrity of the endothelial cells.
RETINAL
VEIN
OCCLUSION
AND
THROMEOPHILIA
A.Sagripanti,M.P.Bartolomei*,L.Evangelisti, A.Carpi**, R.Giordani, M.Nardi*. Internal Medicine Dept., Ophthalmology ctive Age Dept.**, University Hospital,
V.Poggi: Unit*, Pisa,
ReproduItaly.
Occlusion of the central vein or peripheral branches of the retinal venous system is a common cause of impaired vision in adult patients. The pathogenesis ofretinalvein occlusion still remains a matter of debate: generalized blood coagulation alterations are likely tobe involved. We have measured plasma indicators of thrombophilia (re cognized to predispose to venous thrombosis of the lower limbs),including antithrombin III, protein C, protein S, activated protein C resistance, lipoprotein (a), folate, IgGti IgManticardiolipin antibodies, in a series of 33 patients (15 males and 18 females,aged 32 to78 years) co; secutively referred to theOphthalmology UnitofourHospita.1 with an established diagnosis of retinal vein occlusion. The following abnormalities have been found (no= number of patients): protein C deficiency ((70 U/dl) n'l; protein S deficiency (C70 U/dl) nO1: activated protein C resistance (ratio t2) n"5; high lipoprotein (a) (>30mg/dl) no 2; low folic acid ((2 rig/ml) n"3. Antithrombin III plasma levels ranged from 85 to 127 U/d1 (mean 103,7 Wdl): no individual exhibited positive anticardiolipin ant-es. Out of the 33 patients 19 exhibited total cholesterol serum levels >220 mg/dl, and 13 presented plasma fibrinogen concentrations >350 mg/dl. To summarize, 12 of 33 unselected patients affected with retinal vein occlu sion (36%) displayed plasma abnormalities, either inherited or acquired, predisposing to venous thrombosis; these alteration may have been implicated in the pathogenesis of the acute event.