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Dr. Dan Burkhoff joined InsideScientific for Part two of "Basic Hemodynamic Principles Viewed Through Pressure-Volume Relations". In this session, advanced PV Analysis concepts were discussed, along with best-practices during data acquisition and statistical analysis. An extended Q&A session includes detailed answers on subjects from seminar 1. Session 1: The goal of this webinar was to provide an overview of the fundamental principles of preload, afterload, contractility and lusitropy (diastolic properties), how these are quantified on the pressure-volume diagram, and how they are affected in heart failure. Measurement techniques were reviewed. Links were made to underlying properties of cardiac muscle and ventricular structure. After establishing basic concepts, it was demonstrated how pressure-volume analysis can lead to a quantitative understanding of how heart and vasculature interact to determine stroke volume, cardiac output and blood pressure. The implications for understanding therapeutic effects were also discussed. Key Concepts: - Preload, Afterload, Contractility and Lusitropy - Cardiac Muscle and Ventricular Structure - Understanding Heart-Vasculature Interactions - PV Loops in Heart Failure - Understanding Therapies and Their Effects on Cardiac Pump Performance
Citation preview
1
Advanced Concepts in
Pressure-Volume Analysis
Daniel Burkhoff MD PhD Adjunct Associate Professor
Columbia University
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If your research involves studying the effects of altered
genes, cells, extracellular matrix, drugs, etc, on
cardiovascular properties, there are several key
concepts, indexes and measurement techniques you
should be aware of:
PRELOAD
AFTERLOAD
CONTRACTILITY
LUSITROPY
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Resources
Harvi Interactive, simulation-based textbook for
the iPad
iPad 2, 3 and mini (iOS 6)
0 25 50 75 100 125 150 0
25
50
75
100
125
150
LV Volume (ml)
LV
Pre
ss
ure
(m
mH
g)
MV Closes
AoV Opens
AoV
Closes
MV
Opens
Iso
vo
lum
ic
Co
ntr
ac
tio
n
Iso
vo
lum
ic
Rela
xa
tion
Filling
Ejection
The Cardiac Cycle Pressures-Volumes Loop
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0 25 50 75 100 125 150 0
25
50
75
100
125
150
LV Volume (ml)
LV
Pre
ss
ure
(m
mH
g)
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Pressure-Volume Loops and Relationships
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EDPVR and ESPVR define the boundaries within
which the PV Loop sits, independent
of “preload” and “afterload”
0 25 50 75 100 125 150 0
25
50
75
100
125
150
LV Volume (ml)
LV
Pre
ssu
re (
mm
Hg
)
Vo
Ees
End-Systolic Pressure-Volume
Relationship
(ESPVR)
Pes = Ees(Ves-Vo)
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End-Systolic Pressure-Volume Relationship
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Contractility: The concept applied to the Left Ventricle
0 50 100 150 0
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50
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100
125
150
LV Volume (ml)
LV
Pre
ss
ure
(m
mH
g)
Ees Ees
10
Contractility
0 75 150 0
LV Volume (ml)
LV
Pre
ss
ure
(mm
Hg
)
10
20
30
End-Diastolic Pressure-Volume Relationship 11
Vo
P = β(eα(V-Vo)-1)
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Lusitropy: Passive Diastolic Properties
0 125 250 0
LV Volume (ml)
LV
Pre
ssu
re
(mm
Hg
)
10
20
30
Diastolic Capacitance
= volume at a given pressure
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Lusitropy: Passive Diastolic Properties
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ESPVR: Advanced Concepts
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ESPVR: Advanced Concepts
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ESPVR: Advanced Concepts
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Possible ESPVR Changes in Response to Intervention
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ESPVR:
Practical Recommendations
• Linear regression over the range of available data
• Report both Ees and Vo
• Use Analysis of Covariance (or multiple linear
regression analysis with dummy variables) to
compare ESPVRs measured under different
conditions • Do not use t-tests compare slopes or Vo values
• An alternative is to use volume and a specified
pressure (e.g., V120)
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EDPVR: Advanced Concepts
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EDPVR: Advanced Concepts
P=βVα
P= β(eα(V-Vo)-1)
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EDPVR: Advanced Concepts
EDPVR can be linearized by
logarithmic transformation:
P=βVα
Ln(P) = Ln(β) + αLn(V)
As for ESPVR:
• Report both values of α and β
• Use analysis of covariance to
assess for shifts of EDPVR
0
10
20
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50
0 50 100 150 200
y = 4x - 7
-5
-4
-3
-2
-1
0
1
2
0.5 1 1.5 2 2.5
Pressure-Volume
Ln(P) – Ln(V)
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EDPVR: Alternative Analsyis V30
Questions
Physiology & Hemodynamic Concepts
• What is the importance of Tau?
• What conformational changes occur in a PV loop plot, other than a rightward shift of the PV-loops, that confirm the subject has heart failure?
• What is Arterio-Ventricular Coupling?
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0 50 100 150 0
25
50
75
100
125
150
LV Volume (ml)
LV
Pre
ssu
re (
mm
Hg
)
EDV
SV
Pes MAP
25 Ventricular-Vascular Coupling on the PV Diagram
Physiology & Hemodynamic Concepts
• In HF do PV loops maintain their classical shape? In this case, are there changes to the way hemodynamics are calculated (ie. SV, SW, CO)?
• What is the effect of heart valve disorders on PV Loops (aortic stenosis and mitral valve incompetence)?
• Besides differences in pressure, how would RV PV loops differ from LV PV loops?
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ESPVR in CHF
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PV Loops in Valve Lesions
Normal AS MR
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RV vs LV PV Loops
Methodology & Best-Practices
• How can PV loops be used to assess the cardiac safety
of new drugs? Do you see this as a requirement?
• How many PV loops should be included for occlusion
data measurements?
• Are there special considerations for PV loop
measurements in isolated working heart models?
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Load-Independent Measurements
• Strain rates and related analyses have been suggested as a load-independent means of measuring myocardial function and can be looked at globally to assess ventricular function in-vivo with techniques like speckle tracking. Can you comment on this and your opinion regarding myocardial strain analysis as a practical, load-independent measure of cardiac function?
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Load-Independent Measurements
• Work by Glower et al indicated the end-systolic pressure volume relationship was relatively load and heart rate independent within a defined physiologic range. What afterload and heart rate ranges do you feel pressure-volume loop relationships are most appropriately utilized?
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