MITRAL STENOSIS Nick Tehrani, MD Epidemiology of MS Hx of Rheumatic fever is elicited in only 50% of...
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Transcript of MITRAL STENOSIS Nick Tehrani, MD Epidemiology of MS Hx of Rheumatic fever is elicited in only 50% of...
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 feverTwo major Jones criteria, OROne major criterion, and two minor criteria
Major MinorCarditis FeverErythema marginatum PR prolongationChorea ESR elevationSubcutaneous 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 leafletsFusion of the commisuresFusion or shortening of the chordae
Definitions of severity of Mitral Stenosis
Valve Area:<1.0 cm2 Severe1.0-1.5 cm2 Moderate>1.5-2.5 cm2 Mild
Mean gradient: >10 mmHg Severe5-10 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 pressureSecondary RV pressure overloadReduced LV ejection performance
Due to diminished preloadTachycardic 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:
gh2Cv V
Cc x V
Flow Area
Cc =Coefficient ofOrifice contraction
Cv=Coefficient of
Velocity
The Second Equation:
The Gorlin Equation
Substituting for V, in Torricelli’s Eq.
h x 980 x 2 x Cc x Cv
Flow Area
h 44.3 x C
Flow Area
Simplification of the above:
C 44.3?
The Numerator of the Equation
Flow Across any Valve:
For Mitral (and Tricuspid) valve:
(HR) DFP)or (SEP
CO Flow
HR x DFP
CO Flow
h 44.3 x C
Flow Area
The Gorlin Equation
Substituting for “Flow” and “h” in the first Eq.:
h C x 44.3
Flow Area
HR x DFP
CO Flow
Ph
Gorlin’s Formula for Mitral Area
The Gorlin Formula for Mitral Valve area:
P C x 44.3
HR x DFP
CO
Area Valve
Gorlin’s Formula for Mitral Area
CO Cardiac outputDFP Diastolic Filling PeriodHR Heart Rate44.3 Derived ConstantC Correction factor for valve type
C=1.0 for all valves except MitralC=0.85 for Mitral valve
P Mean pressure gradient
How Do you use this Eqn.?
Step 1: Figure out the Numerator First:
Dimensional analysis:
HR x DFP
CO Flow
)(beats/min x (sec/beat)
cc/min cc/sec
P C x 44.3
HR x DFP
CO
Area Valve
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
mm/Secin speedPaper
1beat / mmin DFP
P C x 44.3
HR x DFP
CO
Area Valve
Figure out the Heart Rate
Assuming Patient is in SinusMeasure the RR interval in mmConvert to Beats/min by…
In 100 speed just divide 6,000 by the RR in mm
Beats/minin HR
mm/beat RR
mm/Secin SpeedPaper Sec/min 60
P C x 44.3
HR x DFP
CO
Area Valve
Let’s Figure out the Denominator
P C x 44.3
HR x DFP
CO
Area Valve
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
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
Putting things in Perspective
P C x 44.3
HR x DFP
CO
Area Valve
CC/Sec
mm Hg
cm2
CC/sec.cm2.(mm Hg)P0.5
Potential Pitfalls
Wedge vs. LA PressureStiff End-hole catheter: CournandVerify true wedge by checking O2 SatMean Wedge should be less than Mean PA
Cardiac OutputTrue Fick vs. Thermodilution vs. Green dye
Concurrent MR with MS:Gradient across the valve reflects forward and regurgitant flowCO 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
How Do you use this Eqn.?
Step 1: Figure out the Numerator First:
Dimensional analysis:
HR x DFP
CO Flow
)(beats/min x (sec/beat)
cc/min cc/sec
P C x 44.3
HR x DFP
CO
Area Valve
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
mm/Secin speedPaper
1beat / mmin DFP
P C x 44.3
HR x DFP
CO
Area Valve
Figure out the Heart Rate
Assuming Patient is in SinusMeasure the RR interval in mmConvert to Beats/min by…
In 100 speed just divide 60,000 by the RR in mm
Beats/minin HR
mm/beat RR
mm/Secin SpeedPaper Sec/min 60
P C x 44.3
HR x DFP
CO
Area Valve
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