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 CarditisFever Erythema marginatumPR prolongation ChoreaESR elevation Subcutaneous nodulesHx 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 cm2  Moderate > cm2  Mild Mean gradient: >10 mmHg  Severe 5-10 mmHg  Moderate <5 mmHg  Mild

Flow Across a Normal Mitral Valve in Diastole

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

Diastolic Transmitral Pressure Gradient due to Limited LV Filling

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

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 Cv=Coefficient of Velocity The Second Equation:

The Gorlin Equation Substituting for V, in Torricelli’s Eq. Simplification of the above: C44.3 ?

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 COCardiac output DFPDiastolic Filling Period HRHeart Rate 44.3Derived Constant CCorrection factor for valve type C=1.0 for all valves except Mitral C=0.85 for Mitral valve PMean pressure gradient

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

Figure out the DFP 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 Heart Rate 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

Let’s Figure out the Denominator

No Mitral Stenosis

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

Need to Left Shift the PCWP Tracing

V A C DFP Planimeter Shifted Over

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

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

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

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: 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

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

Figure out the DFP 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 Heart Rate 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

V A C DFP Planimeter

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