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### 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
- One major criterion, and two minor criteria

MajorMinor

Carditis Fever

Erythema marginatum PR prolongation

Chorea ESR elevation

Subcutaneous nodules Hx of Rheumatic fever

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

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

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

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

Flow Across the Stenotic Valve

- Note the “A” in patient who is in sinus

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

Determinants of Transmitral Pressure Gradient

Increased Flow, OR

Decreased orifice size

Incr. Gradient.

Elevated LA pressure

HR=72

HR=100

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

Different ways of Measuring Mitral Valve Area

- Echocardiographic:
- PISA
- 2-D
- Pressure half-time
- Cath:
- Gorlin’s Equation
- Pressure half time

The Gorlin Equation

- Torricelli’s Law:

- Cc =Coefficient of
- Orifice contraction

- The Second Equation:

- Cv=Coefficient of
- Velocity

The Numerator of the Equation

- Flow Across any Valve:
- For Mitral (and Tricuspid) valve:

The Gorlin Equation

- Substituting for “Flow” and “h” in the first Eq.:

Gorlin’s Formula for Mitral Area

- The Gorlin Formula for Mitral Valve area:

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

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 DFPAssuming 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 RateInstrumentation

- The trickiest part is to set up the instrument correctly:

- The reading must be adjusted to
- 0.0000

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

How many tracings to Planimeter

- If patient is in sinus => 5 tracings
- If patient is in A-Fib.=> 10 tracings

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

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

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.

Pulmonary Hypertension

- This pulmonary hypertension has two components:
- Reactive pulmonary arterial vasoconstriction,
- Potentially Fixed resistance, secondary to morphologic changes in the pulmonary vasculature

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 DFPAssuming 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 RateFrom 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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