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MITRAL STENOSIS

MITRAL STENOSIS . Nick Tehrani, MD. Epidemiology of MS. Hx of Rheumatic fever is elicited in only 50% of path proven cases Other causes Severe MAC Congenital MS. Clinical Diagnosis of Rheumatic Fever. Diagnosis of acute rheumatic fever Two major Jones criteria, OR

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MITRAL STENOSIS

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  1. MITRAL STENOSIS Nick Tehrani, MD

  2. Epidemiology of MS • Hx of Rheumatic fever is elicited in only 50% of path proven cases • Other causes • Severe MAC • Congenital MS

  3. Clinical Diagnosis of Rheumatic Fever • Diagnosis of acute rheumatic fever • Two major Jones criteria, OR • One major criterion, and two minor criteria MajorMinor Carditis Fever Erythema marginatum PR prolongation Chorea ESR elevation Subcutaneous nodules Hx of Rheumatic fever

  4. Clinical Diagnosis of Acute Rheumatic Fever • Additionally, serologic evidence of recent streptococcal infection is needed: • Positive bacteriologic culture • Increase in ASO titers • Increase in anti-DNAse B titers

  5. Histopathology • The acute valvular pathology caused by Rheumatic fever is: Mitral Regurgitation • Over the next several decades stenosis accrues by: • Thickening of the leaflets • Fusion of the commisures • Fusion or shortening of the chordae

  6. Definitions of severity of Mitral Stenosis • Valve Area: • <1.0 cm2  Severe • 1.0-1.5 cm2  Moderate • >1.5-2.5 cm2  Mild • Mean gradient: • >10 mmHg  Severe • 5-10 mmHg  Moderate • <5 mmHg  Mild

  7. Flow Across a Normal Mitral Valve in Diastole

  8. Flow Across the Stenotic Valve • Persistent LA-LV gradient in diastole  sustained flow throughout diastole • The slope of the envelope is proportional to the severity of stenosis

  9. Flow Across the Stenotic Valve • Note the “A” in patient who is in sinus

  10. Diastolic Transmitral Pressure Gradient due to Limited LV Filling

  11. Pathophysiology • Limited flow into the LV has 3 major sequale: • Elevation of Lt. Atrial pressure • Secondary RV pressure overload • Reduced LV ejection performance • Due to diminished preload • Tachycardic response to compensate to decreased SV worsens the transmitral gradient

  12. Determinants of Transmitral Pressure Gradient Increased Flow, OR Decreased orifice size  Incr. Gradient.  Elevated LA pressure

  13. HR=72 HR=100

  14. Variability Problems are Introduced by: • The three inter-related parameters are: • HR • CO • Trans-mitral gradient  Mitral valve area Heart rate variability CO measurement and reproducibility

  15. Different ways of Measuring Mitral Valve Area • Echocardiographic: • PISA • 2-D • Pressure half-time • Cath: • Gorlin’s Equation • Pressure half time

  16. The Gorlin Equation • Torricelli’s Law: • Cc =Coefficient of • Orifice contraction • The Second Equation: • Cv=Coefficient of • Velocity

  17. The Gorlin Equation • Substituting for V, in Torricelli’s Eq. C 44.3 Simplification of the above: ?

  18. The Numerator of the Equation • Flow Across any Valve: • For Mitral (and Tricuspid) valve:

  19. The Gorlin Equation • Substituting for “Flow” and “h” in the first Eq.:

  20. Gorlin’s Formula for Mitral Area • The Gorlin Formula for Mitral Valve area:

  21. Gorlin’s Formula for Mitral Area • CO Cardiac output • DFP Diastolic Filling Period • HR Heart Rate • 44.3 Derived Constant • C Correction factor for valve type C=1.0 for all valves except Mitral C=0.85 for Mitral valve • P Mean pressure gradient

  22. Step 1: Figure out the Numerator First: Dimensional analysis: How Do you use this Eqn.?

  23. DFP in Sec/beat Measure the Distance in mm from MV opening to MV closing in one beat Convert distance to time 100 speed= 100 mm/sec, makes life easy 50 speed= 50 mm/sec, tough life Figure out the DFP

  24. Assuming Patient is in Sinus Measure the RR interval in mm Convert to Beats/min by… In 100 speed just divide 6,000 by the RR in mm Figure out the Heart Rate

  25. Let’s Figure out the Denominator

  26. No Mitral Stenosis

  27. Diastolic Transmitral Pressure Gradient due to Limited LV Filling Left Atrial Tracing

  28. Need to Left Shift the PCWP Tracing

  29. C A V Planimeter DFP Shifted Over

  30. Instrumentation • The trickiest part is to set up the instrument correctly: • The reading must be adjusted to • 0.0000

  31. From Planimetered Area to Mean Pressure Gradient • Area as provided by the instrument is in (in)x(in) • Must convert to (cm)x(cm) • Multiply by 6.45 cm2/In2 • To obtain mean Area under the curve • Divide the Area by the DFP in cm • To convert cm of pressure to mm of Hg • Multiply the above # in cm, by the “scale factor” • Get “Scale factor” from the tracing: mm Hg/cm

  32. How many tracings to Planimeter • If patient is in sinus => 5 tracings • If patient is in A-Fib.=> 10 tracings

  33. Putting things in Perspective CC/Sec cm2 CC/sec.cm2.(mm Hg)P0.5 mm Hg

  34. Potential Pitfalls • Wedge vs. LA Pressure • Stiff End-hole catheter: Cournand • Verify true wedge by checking O2 Sat • Mean Wedge should be less than Mean PA • Cardiac Output • True Fick vs. Thermodilution vs. Green dye • Concurrent MR with MS: • Gradient across the valve reflects forward and regurgitant flow • CO reflects the net forward flow only • Likely underestimation of the true valve area

  35. Mitral Stenosis and the LA • Even in sinus rhythm, the low velocity flow predisposes to formation of atrial thrombi. • Low flow pattern is seen as spontaneous contrast on echocardiography • 17% of patients undergoing surgery for MS have LA thrombus • In one third of cases thrombus restricted to the LAA

  36. Pulmonary Hypertension • Normal pressure drop across pulmonary bed: 10-15 mm Hg • Expected mean PA in Mitral Stenosis: Mean LA (elevated of course) + (10-15 mm Hg) • In MS, Mean PA pressure often exceed the expected.

  37. Pulmonary Hypertension • This pulmonary hypertension has two components: • Reactive pulmonary arterial vasoconstriction, • Potentially Fixed resistance, secondary to morphologic changes in the pulmonary vasculature

  38. Step 1: Figure out the Numerator First: Dimensional analysis: How Do you use this Eqn.?

  39. DFP in Sec/beat Measure the Distance in mm from MV opening to MV closing in one beat Convert distance to time 100 speed= 100 mm/sec, makes life easy 50 speed= 50 mm/sec, tough life Figure out the DFP

  40. Assuming Patient is in Sinus Measure the RR interval in mm Convert to Beats/min by… In 100 speed just divide 60,000 by the RR in mm Figure out the Heart Rate

  41. C A V Planimeter DFP

  42. From Planimetered Area to Mean Pressure Gradient • Area as provided by the instrument is in (in)x(in) • Must convert to (cm)x(cm) • Multiply by 6.45 cm2/In2 • To obtain mean Area under the curve • Divide the Area by the DFP in cm • To convert cm of pressure to mm of Hg • Multiply the above # in cm, by the “scale factor” • Get “Scale factor” from the tracing: mm Hg/cm

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