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HAEMODYNAMICS

HAEMODYNAMICS. Vascular resistance Shunt Calculation Stenotic valve area. VASCULAR RESISTANCE. Q = volume flow. Pi – Po = inflow – outflow pressure. r = radius of tube. L = length of tube. η = viscosity of the fluid. Vascular Resistance Poiseuille’s Law.  (P i – P o ) r 4. Pi.

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HAEMODYNAMICS

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  1. HAEMODYNAMICS Vascular resistance Shunt Calculation Stenotic valve area

  2. VASCULAR RESISTANCE

  3. Q = volume flow Pi – Po = inflow – outflow pressure r = radius of tube L = length of tube η = viscosity of the fluid Vascular ResistancePoiseuille’s Law  (Pi – Po) r 4 Pi Q = r Pi Po 8 η L L  P 8 η L In vascular system, key factor is radius of vessel Resistance = =  r 4 Q

  4. Vascular ResistanceDefinitions Normal reference values Woods Units x 80 = Metric Units Systemic vascular resistance Ao - RA 10 – 20 770 – 1500 SVR = Qs Pulmonary vascular resistance PA - LA 0.25 – 1.5 20 – 120 PVR = Qp

  5. Vascimpedence –pulsatile pressure /pulsatile flow Research use Analogue is Vasc resistance

  6. Clinical use PVR/SVR ratio <.25 – normal .25 - .5 mild pulmvasc disease .5 - .75 moderate >.75 severe Better indicator than PVR alone

  7. SHUNT DETECTION & QUANTIFICATION

  8. Shunt Detection & MeasurementIndications • Arterial desaturation (<95%) • Alveolar hypoventilation (Physiologic Shunt) corrects with deep inspiration and/or O2 • Sedation from medication • COPD / Pulmonary parenchymal disease • Pulmonary congestion • Anatomic shunt (RtLf) does not correct with O2 • Unexpectedly high PA saturation (>80%) due to LfRt shunt

  9. Shunt Detection & MeasurementMethods • Shunt Detection • Indocyanine green method • Oximetric method • Shunt Measurement • Left-to-Right Shunt • Right-to-Left Shunt • Bidirectional Shunt

  10. Shunt Detection & MeasurementIndocyanine Green Method Indocyanine green (1 cc) injected as a bolus into right side of circulation (pulmonary artery) Concentration measured from peripheral artery Appearance and washout of dye produces initial 1stpass curve followedby recirculation innormal adults

  11. Shunt Detection & MeasurementLeft-to-Right Shunt

  12. Shunt Detection & MeasurementRight-to-Left Shunt

  13. Shunt Detection & MeasurementIndocyanine Green Method

  14. Shunt Detection & MeasurementMethods • Shunt Detection • Indocyanine green method • Oximetric method • Shunt Measurement • Left-to-Right Shunt • Right-to-Left Shunt • Bidirectional Shunt

  15. Shunt Detection & MeasurementOximetric Methods • Obtain O2 saturations insequential chambers,identifying both step-upand drop-off in O2 sat • Insensitive for smallshunts (< 1.3:1)

  16. Shunt Detection & MeasurementOximetry Run • IVC, L4-5 level • IVC, above diaphragm • SVC, innominate x x • SVC, at RA x • RA, high • RA, mid x x • RA, low x x • RV, mid x • RV, apex • RV, outflow tract x x x • PA, main x x • PA, right or left x • Left ventricle x • Aorta, distal to ductus

  17. Shunt Detection & MeasurementOximetric Methods 3 (SVC) + IVC Mixed venous saturation = 4 • RA receives blood from several sources • SVC: Saturation most closely approximates true systemic venous saturation • IVC: Highly saturated because kidneys receive 25% of CO and extract minimal oxygen • Coronary sinus: Markedly desaturated because of heart’s maximal O2 extraction • FlammEquation: Mixed venous saturation used to normalize for differences in blood saturations that enter RA

  18. Shunt Detection & MeasurementMethods • Shunt Detection • Indocyanine green method • Oximetric method • Shunt Measurement • Left-to-Right Shunt • Right-to-Left Shunt • Bidirectional Shunt

  19. Shunt Detection & MeasurementDetection of Left-to-Right Shunt Mean  O2 Vol % Mean  O2% Sat Minimal QpQsdetected Level of shunt Differentialdiagnosis ASD, PAPVC, VSD with TR,Ruptured sinus of Valsalva,Coronary fistula to RA Atrial (SVC/IVC  RA)  7  1.3 1.5 – 1.9 Ventricular (RA  RV) VSD, PDA with PR,Coronary fistula to RV  5  1.0 1.3 – 1.5 Great vessel (RV  PA) Aorto-pulmonary window, Aberrant coronary origin, PDA  5  1.0 1.3 ANY LEVEL (SVC  PA)  7  1.3 1.3 All of the above

  20. Shunt Detection & MeasurementOximetric Methods Lungs RA (MV) LA (PV) RV LV PA Ao O2 content = 1.36 x Hgb x O2 saturation O2 consumption PBF = (PvO2 – PaO2) x 10 x Hb x 1.36 • Fick Principle: The total uptake or release of any substance by an organ is the product of blood flow to the organ and the arteriovenous concentration difference of the substance. • Pulmonary circulation (Qp) utilizes PA and PV saturations

  21. Shunt Detection & MeasurementOximetric Methods RA (MV) LA (PV) O2 content = 1.36 x Hgb x O2 saturation RV LV O2 consumption PA Ao SBF = (AoO2 – MVO2) x 10 x Hb x 1.36 Body • Systemic circulation (Qs) utilizes MV and Ao saturations

  22. Shunt Detection & MeasurementEffective Blood Flow PBF O2 consumption O2 consumption Effective Blood Flow = = (Pv – MV O2) x 10 (Pv – Pa O2) x 10 Effective Blood Flow: flow that would be present if no shunt were present

  23. Shunt Detection & MeasurementLeft-to-Right Shunt Left-Right Shunt = Pulmonary Blood Flow – Effective Blood Flow O2 consumption O2 consumption = – (PvO2 – MVO2) x 10 (PvO2 – Pa O2) x 10 (AoO2 – MVO2) Qp / Qs Ratio = PBF / SBF = (PvO2 – PaO2) Left to right shunt results in step-up in O2 between MV and PA Shunt is the difference between pulmonary flow measured and what it would be in the absence of shunt (EPBF)

  24. Shunt Detection & MeasurementLeft-to-Right Shunt ASD VSD Coronary Cameral Fistula Ruptured Sinus of Valsalva Partial Anomalous Pulmonary Venous Return Aorto Pulmonary Window PDA Aberrant Coronary Origin

  25. Shunt Detection & MeasurementMethods • Shunt Detection • Indocyanine green method • Oximetric method • Shunt Measurement • Left-to-Right Shunt • Right-to-Left Shunt • Bidirectional Shunt

  26. Shunt Detection & MeasurementEffective Blood Flow SBF O2 consumption O2 consumption = = Effective Flow (Pv – MV O2) x 10 (Ao – MV O2) x 10 Effective Blood Flow: flow that would be present if no shunt were present

  27. Shunt Detection & MeasurementRight-to-Left Shunt Right-Left Shunt = Systemic Blood Flow – Effective Blood Flow O2 consumption O2 consumption = – (PvO2 – MVO2) x 10 (AoO2 – MVO2) x 10 (AoO2 – MVO2) Qp / Qs Ratio = PBF / SBF = (PvO2 – PaO2) Right to left shunt results in step-down in O2 between PV and Ao Shunt is the difference between systemic flow measured and what it would be in the absence of shunt (EPBF)

  28. Shunt Detection & MeasurementRight-to-Left Shunt • Tetralogy of Fallot • Eisenmenger Syndrome • Pulmonary arteriovenous malformation • Total anomalous pulmonary venous return (mixed)

  29. Shunt Detection & MeasurementMethods • Shunt Detection • Indocyanine green method • Oximetric method • Shunt Measurement • Left-to-Right Shunt • Right-to-Left Shunt • Bidirectional Shunt

  30. Shunt Detection & MeasurementBidirectional Shunts • Right-to-Left Shunt • Qs - Qeff Left-to-Right Shunt Qp - Qeff

  31. Shunt Detection & MeasurementBidrectional Shunt Transposition of Great Arteries Tricuspid atresia Total anomalous pulmonary venous return Truncusarteriosus Common atrium (AV canal) Single ventricle

  32. Shunt Detection & MeasurementLimitations of Oximetric Method • Requires steady state with rapid collection of O2 samples • Insensitive to small shunts • Flow dependent • Normal variability of blood oxygen saturation in the right heart chambers is influenced by magnitude of SBF • High flow state may simulate a left-to-right shunt • When O2 content is utilized (as opposed to O2 sat), the step-up is dependent on hemoglobin.

  33. STENOTIC VALVE AREA

  34. Valve StenosesGorlin Formula Derivation Hydraulic Principle # 1 (Toricelli’s Law) Hydraulic Principle # 2 F = A • V • C V2 = Cv2 • 2 g h V = velocity of flow F = flow rate A = area of orifice Cv = coefficient of velocity V = velocity of flow g = acceleration gravity constant Cc = coefficient of orifice contraction h = pressure gradient in cm H2O Flow Flow A = = Cc Cv • 2 g h C * 44.3 h

  35. Valve StenosesTwo Catheter Technique

  36. Valve StenosesGorlin Formula Derivation Flow A = C• 44.3 h Flow has to be corrected for the time during which there is cardiac output across the valve. Aortic Pulmonic Tricuspid Mitral Systolic Flow (SEP) Diastolic Flow (DFP) Gorlin Formula: Constant: CO / (DFP or SEP) • HR A = Aortic, Tricuspid, Pulmonic: C = 1.0 Mitral: C = 0.85 C• 44.3 P

  37. Valve StenosesThe “Quick Valve Area” Formula Gorlin Formula: CO / (DFP or SEP) • HR A = C• 44.3 P Quick Valve Area Formula (Hakki Formula): Determine peak gradient across valve. CO A = Peak gradient

  38. Aortic Valve StenosisCalculating Valve Area Step 1: Planimeter area and calculate SEP Gradient Deflection Length of SEP SEP Area of gradient (mm) (mm) (mm2) #1 #2 #3 #4 #5 Average deflection = mm

  39. Aortic Valve StenosisCalculating Valve Area Step 2: Calculate mean gradient Mean gradient = Average deflection x Scale Factor (mm Hg) (mm deflection) (mm Hg / mm deflection) Step 3: Calculate average systolic period Average SEP (mm) Average SEP = Paper speed (mm / sec) (sec / beat) Step 4: Calculate valve area . Q (cm3 / min) / [Average SEP (sec / beat) x HR (beat / min)] Valve area = (cm2) 44.3 x mean gradient

  40. Aortic StenosisPitfalls in Gorlin Formula • Hydraulic principles • Low cardiac output • Do not Distinguish true anatomic stenosis from aortic psuedostenosis– low gradient • Nitroprusside or dobutamine to distinguish conditions • Mixed valvular disease • Pullback hemodynamics • Improper alignment

  41. Aortic StenosisPitfalls in Gorlin Formula • 75 consecutive patients with isolated AS • Compare Gorlin AVA and continuity equation (Doppler) AVA • Doppler AVA systematically larger than Gorlin AVA (0.10 ± 0.17 cm2, p<0.0001) • AVA difference was accentuated at low flow states (cardiac index < 2.5 L/min/m2)

  42. Aortic StenosisPitfalls in Gorlin Formula • Hydraulic principles • Low cardiacMixedvalvular disease • AS & AR: CO underestimates transvalvular flow  Gorlin underestimates AVA • AS & MR: CO overestimates forward stroke volume  Gorlin overestimates AVA • Pullback hemodynamics • Improper alignment

  43. Aortic StenosisPitfalls in Gorlin Formula • Hydraulic principles • Low caPullbackhemodynamics • - Large ( 7 Fr) cathetermay obstruct lumen andoverestimate severity • Pullback of catheter mayreduce severity • Augmentation in peripheral systolic pressure by > 5 mm Hg during pullback  AVA  0.5 cm2 • Improper alignment

  44. Aortic StenosisPitfalls in Gorlin Formula • Hydraulic principles • Low cardiac output • Pullback hemodynamics • Improper alignment Unaltered LV-FA LV-Aortic Aligned LV-FA Gradient 31 37 22 Area (cm2) 1.07 1.01 1.24

  45. Mitral StenosisCalculating Valve Area Step 1: Planimeter area and calculate DFP DFP Gradient Deflection DFP Area of gradient (mm) (mm) (mm2) #1 #2 #3 #4 #5 Average gradient = mm

  46. Mitral StenosisCalculating Valve Area Step 2: Calculate mean gradient Mean gradient = Average deflection x Scale Factor (mm Hg) (mm deflection) (mm Hg / mm deflection) Step 3: Calculate average Diastolic filling period Average DFP (mm) Average DFP = Paper speed (mm / sec) (sec / beat) Step 4: Calculate valve area . Q (cm3 / min) / [Average DFP (sec / beat) x HR (beat / min)] Valve area = (cm2) 37.7 x mean gradient

  47. Mitral StenosisPitfalls in Gorlin Formula • Pulmonary capillary wedge tracing • Alignment mismatch • LV & PCW traces do not match LV & LA traces because transmission of LA pressure back thru PV and capillary bed delayed 50-70 msec • Realign tracings • Shift PCW tracing leftward by 50-70 msec • V wave should peak immediately before LV downslope • Calibration errors • Cardiac output determination • Early diastasis

  48. Mitral StenosisPitfalls in Gorlin Formula • Pulmonary capillary wedge tracing • Alignment mismatch • Calibration errors • Errors in calibration and zero • Quick check: switch transducers between catheters and see if gradient identical • Cardiac output determination • Early diastasis

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