Transcript MITRAL STENOSIS - NT Cardiovascular

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
Major
Minor
Carditis
Erythema marginatum
Chorea
Subcutaneous nodules
Fever
PR prolongation
ESR elevation
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 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
Problems
are
Variability
Introduced by:
The three inter-related parameters are:
HR
Heart rate variability
CO
CO measurement and reproducibility
Trans-mitral gradient
 Mitral valve area
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
Area 
Flow
V x Cc 
Orifice contraction
The Second Equation:
Cv=Coefficient of
Velocity

V  Cv 2gh

The Gorlin Equation
Substituting for V, in Torricelli’s Eq.
Flow
Area 
Cv x Cc x 2 x 980 x h
C
Simplification of the above:
44.3
?
Flow
Area 
C x 44.3
h
The Numerator of the Equation
Area 
Flow
C x 44.3
Flow Across any Valve:
CO
Flow 
(SEP or DFP ) (HR)
For Mitral (and Tricuspid) valve:
CO
Flow 
DFP x HR
h
The Gorlin Equation
Substituting for “Flow” and “h” in the first Eq.:
Flow
Area 
44.3 x C h
CO
Flow 
DFP x HR
h  P
Gorlin’s Formula for Mitral Area
The Gorlin Formula for Mitral Valve area:
CO

 DFP x HR
Valve Area  
 44.3 x C  P








Gorlin’s Formula for Mitral Area
CO
DFP
HR
44.3
C
Cardiac output
Diastolic Filling Period
Heart Rate
Derived Constant
Correction factor for valve type
C=1.0 for all valves except Mitral
C=0.85 for Mitral valve
P
Mean pressure gradient
How Do you use this Eqn.?
Step 1: Figure out the Numerator First:
CO
Flow 
DFP x HR
Dimensional analysis:
cc/min
cc/sec 
(sec/beat )x (beat s/min)
CO




Valve Area   DFP x HR 
 44.3 x C  P 


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
1


DFP in mm / beat 

 Paper speed in mm/Sec 
100 speed= 100 mm/sec, makes life easy
50 speed= 50 mm/sec, tough life
CO


 DFP x HR 
Valve Area  

 44.3 x C  P 


Figure out the Heart Rate
Assuming Patient is in Sinus
Measure the RR interval
in mm
Convert to Beats/min
by…
60 Sec/min Paper Speed in mm/Sec 
 HR in Beats/min
RR mm/beat
In 100 speed just divide
6,000 by the RR in mm
CO


 DFP x HR 
Valve Area  

 44.3 x C  P 


Let’s Figure out the Denominator
CO

 DFP x HR
Valve Area  
 44.3 x C  P








No Mitral Stenosis
Diastolic Transmitral Pressure
Gradient due to Limited LV Filling
Left Atrial
Tracing
Need to Left Shift the PCWP Tracing
C
V
A
Planimeter
DFP
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
CC/Sec
cm2
CO

 DFP x HR
Valve Area  
 44.3 x C  P


CC/sec.cm2.(mm Hg)P0.5
mm Hg






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
How Do you use this Eqn.?
Step 1: Figure out the Numerator First:
CO
Flow 
DFP x HR
Dimensional analysis:
cc/min
cc/sec 
(sec/beat )x (beat s/min)
CO




Valve Area   DFP x HR 
 44.3 x C  P 


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
1


DFP in mm / beat 

 Paper speed in mm/Sec 
100 speed= 100 mm/sec, makes life easy
50 speed= 50 mm/sec, tough life
CO


 DFP x HR 
Valve Area  

 44.3 x C  P 


Figure out the Heart Rate
Assuming Patient is in Sinus
Measure the RR interval
in mm
Convert to Beats/min
by…
60 Sec/min Paper Speed in mm/Sec 
 HR in Beats/min
RR mm/beat
In 100 speed just divide
60,000 by the RR in mm
CO


 DFP x HR 
Valve Area  

 44.3 x C  P 


C
A
V
Planimeter
DFP
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