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Hemodynamikk Hans Torp Fysiologi og Biomedisinsk Teknikk NTNU

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Hemodynamics Hemo from Haima = BloodHemo from Haima = Blood Dynamics from Dynamis ~ force which results in motionDynamics from Dynamis ~ force which results in motion Blood pressure -> Blood flowBlood pressure -> Blood flow Voltage current

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Normal blood pressure is not sufficient Voltage current

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Relation blood pressure / blood flow Blood pressure = Blood flow * periferal resistanceBlood pressure = Blood flow * periferal resistance periferal resistance increases by narrowing of capillariesperiferal resistance increases by narrowing of capillaries Blood flow to an organ may have substaial variation, with a constant blood pressureBlood flow to an organ may have substaial variation, with a constant blood pressure

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Blood flow – low periferal resistance Blood pressure Blood flow

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Blood flow – high periferal resistance Blood pressure Blood flow Spill film

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Hastighet [cm/s] versus volumstrøm [ml/s] V1 A1 Blodmengde som passerer areal A1: Q1 = V1 * A1 Hastighet V1 måles med Doppler, areal A1 måles på ultralydbilde Eksempel: V1= 30 cm/s, A1= 0.3 cm^2, Q1 = 9 ml/s = 54 ml/min

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Stenosis assessment V1V2 A1 A2 V1 * A1 = V2 * A2 % reduksjon A1 - A2 = V2 - V1 A1 V2 Example: 5x velocity corresponds to 80% stenose Degree of stenosis can be calculatet without angle correction

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Stenose + lekkasje i aortaklaff

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Pressure gradient in a stenosis V1V2 P1 P2 Bernouli’s equation: P1 - P2 = 4 V2 - 4 V1 22 V [m/s] P [mmHg] Hans Torp NTNU, Norway

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Fall i blodtrykk ved stenose V1V2 P1 P2 Bernouli’s ligning: P1 - P2 = 4 V2 - 4 V1 2 2 Significant stenosis (V2 >>V1) : P1 - P3 = 4 V2 Cinetic energy loss due to turbulence P3 2 Hans Torp NTNU, Norway

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Pressure gradient in a stenosis V1V2 P1 P2 Trykk - fall (gradient) : P1 - P3 = 4 V2 P3 2 Eksempel: 80% aorta-stenose V1= 1 m/s V2 = 5 m/s gir trykk-gradient 4*5*5 = 100 mmHg Hans Torp NTNU, Norway

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V1V2 P1 P2 Bernouli’s equation Pressure gradient: P1 - P3 = 4 V 2 2 P3 Example: 80% aortic-stenosis V1= 1 m/s V2 = 5 m/s ~ pressure gradient of 4*5*5 = 100 mmHg Left ventricular pressure of 220 mmHg is required to achieve 120 mmHg aothic pressure Hans Torp NTNU, Norway Pressure gradient in a stenosis

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