Michael Pinsky RV function under pressure

Right Ventricular Function
Under Pressure
Michael R. Pinsky, MD, Dr hc
Department of Critical Care Medicine
University of Pittsburgh

Background: Right Ventricle Failure
• Occurs in many disease states
– LV systolic dysfunction and CHF
• Pulmonary disease (cor pulmonale)
– Coronary artery disease (RV infarct) • Pulmonary hypertension
– Valvular heart disease (MS, TR, PS)
• Liver disease
– Congenital heart disease
• Worse Prognosis
It is very common
– HF due to systolic dysfunction (de Groote P, et. al. JACC 1998;32:948-54., Ghio S, et. al..
JACC 2001;37:183-8.) 8.)
– Ventricular Assist Device implantation ti (Rose EA, et. Al. NEJM 2001;345:1435-1443.)
1435 1443.)
– Acute myocardial infarction (Sakata, et. al.. Am J Cardiol 2000;85:939-44., Mehta, et. al. JACC
2001;37:37-43.)
– CABG (Eagle It
KA, has et al.. JACC bad 1999;34(4):1262-347.)
outcomes
347.)
– valve surgery (Bonow RO, et. al. JACC 1998;32:1486-588.)
– primary PH (D'Alonzo GE, et. al. Ann Intern Med 1991;115:343–349.) 349.)
– pulmonary arterial embolectomy (Gilbert TB, et. al.. World Journal of Surgery 1998;22:1029-
1033.)
– relative contraindication for liver transplant (Kuo et al. Transplantation 1999;67:1087-1093.) 1093.)

ECG-Gated Gated Multislice Computed
Tomographic Angiography (MSCTA)
to Assess Right Ventricular Function
Simon et al. University of Pittsburgh

Rapid CT 3-D reconstruction of RV Cavity by MSCTA
Main pulmonary artery
Pulmonary valve
Superior vena cava
RV outflow tract
Tricuspid valve
Right atrium & appendage
Inferior vena cava
Simon et al. University of Pittsburgh

RV Systolic Function and Aortic Pressure
RV pressure 20
Brooks et al. J Clin Invest 50:2176-83, 1971

RV Systolic Function and Aortic Pressure
RV pressure 40
Brooks et al. J Clin Invest 50:2176-83, 1971

RV Systolic Function and Aortic Pressure
Brooks et al. J Clin Invest 50:2176-83, 1971

Effects of Right Coronary Blood Flow on Cardiac
Output during Supra-critical PA Pressures
Start of coronary perfusion pump
Brooks et al. J Clin Invest 50:2176-83, 1971

Effects of Pulmonary Hypertension on
Right Coronary Blood Flow
Brooks et al. J Clin Invest 50:2176-83, 1971

LV Pressure-Volume Loop
LV
Pressure
(mm Hg)
End-systole
Ejection (stroke volume)
Isometric
Relaxation
Aortic Valve
Opening
Isometric
Contraction
Mitral
Valve
Opening
Diastolic filling
LV Volume
(mL)
End-diastole
diastole

On the Nature of LV Contraction
Sequential P/V Loops during IVC Occlusion
LV
Pressure
IVC
Occlusion
LV Volume

Right Ventricular Pressure-
Volume Loops
• Conductance Catheter measuring RV blood
pool impedance (Leycom,NL)
• High fidelity pressure tipped catheter in RV
(Millar)
• Rapid changes in RV volumes or pressures
• Animal model in which measurement
artifacts are minimized (rabbit, piglet)
• Solda et al. J Appl Physiol 73:1770-5, 1992
• Pinsky et al. J Crit Care 11: 65-76, 1996

Bi-Ventricular End-Systolic
Pressure Volume Relationships
(generated by IVC occlusion)
Left Ventricle
Right Ventricle
E es
Occlusion
Ees
Occlusion
Diastolic compliance
Diastolic compliance

Assessment of Right Ventricular
Function
RV Pressure Assumption:
RV end-systolic pressure-
volume relation (ESPVR)
correlates with RV
contractility

Left Ventricular Function
(generated by IVC occlusion)
E es
O l i
m Hg)
ure (mm
V pressu
LV
Ejection
Occlusion
Diastolic compliance
LV volume (ml)

Right Ventricular Function
IVC Occlusion
Hg)
RV
pressur
re (mm
E es
Diastolic filling
Diastolic compliance
RV volume (ml)

Right Ventricular Ejection
Although RV Ees can be measured,
does it reflect RV contractility tilit
or
the influence of LV ejection
Systolic ventricular
interdependence

Effect of isolated LV contraction on
RV Developed Pressure
63.5 LV vs. 36.5% RV contribution
to RV developed pressure
Damiano et al. Am J Physiol 261:1514-24, 24, 1991

Effect of isolated LV contraction
on RV Developed Pressure
• LV contraction creates 70% of the
developed RV systolic pressure
• Septal contraction not required for this
effect
•The right ventricle is squeezed by the
left ventricular contraction through the
free wall
– Damiano et al. Am J Physiol 261:1514-24, 24, 1991

Effect of Partial Aortic Occlusion
On LV and dRVP Pressure-Volume Vl Loops
End-systolic shift
Increased ejection force
Pinsky et al. J Crit Care 11: 65-76, 1996

Partial lA Aortic Occlusion
Left ventricle
Closed Pericardium
Right ventricle
E es
End-systolic shift
Shi & Pinsky 1994

RV elastance in vivo
Cannot Be Defined
• The RV ESPVR is directly
dt determined db by the force of fLV
contraction
• Changes in RV end-diastolic diastolic volume
and ejection pressure may variably
alter contractility

Ventricular Interdependence
• Traditional Concept: Changes in
Right Ventricular volume alters
Left Ventricular function
• Diastolic interaction Right to Left
–Increased RV end-diastolic diastolic volume
decreases LV diastolic compliance
– Decreased RV end-diastolic diastolic volume
increases LV diastolic compliance

Increases in RV volume decrease
mm Hg)
ssure (m
lar Pres
ntricul
Left Ve
20
LV diastolic compliance
12
RV volume:
0 ml
23 ml
2
35 ml
0
47 ml
10
0 10 20 30 40
Left Ventricular Volume (ml)
Taylor et al. Am J Physiol 213:706-10, 10, 1967

Effect of Partial Pulmonary Artery Occlusion
On LV and dRVP Pressure-Volume Vl Loops
70 mm Hg
End-diastolic diastolic shift
Decreased compliance
70 mm Hg
LVP
RVP
LVV
3.30 ml
RVV
Pinsky et al. J Crit Care 11: 65-76, 1996

Volume Expansion in Cor Pulmonale
Before Volume Expansion
After Volume Expansion
(500 mL plasma expander)
ΔPP 21% ΔPP 29%
RA
LA
RA
LA
RV
LV
RV
LV
CI: 1.3 L/min/m 2
CI: 1.4 L/min/m 2
from Jardin personal communication

Right Ventricular Afterload
Question: Does pulmonary artery pressure
vary with ih right ventricular outflow
Sometimes,
but at the Extremes of blood flow
(exercise) and in the setting of increased
pulmonary vascular resistance
(pulmonary vascular disease)

Question: Does RV Afterload
Change Independent of Pressure
• Afterload is wall stress and varies
with wall tension
– LaPlace’s Law:
Tension = Pressure x radius of
curvature
• Decreasing RV radius of curvature
should reduce RV afterload
r
P

Mild RV Loading Decreases RV Wall Stress
RV free wall radius decreases!

Representative Images
ECG-Gated Gated Multislice Computed Tomographic Angiography (MSCTA)
to Assess Right Ventricular Function
Normal:
RVFAC 0.72
RAP 4 mmHg, MPAP 17 mmHg,
CI 4.9 L/min
PH and RV Failure:
Dx: IPF; RVFAC 0.18
RAP 18 mmHg, MPAP 50 mmHg,
CI 1.8 L/min
Simon et al. Clin Tranlational Sci 2: 294-9, 9, 2009

Computed Tomography of RV
Normal
RV FAC = 72 %
RA pressure 4 mm Hg
mean PA 17 mm Hg
cardiac index 4.9 L/min
End-Diastole
End-Systole
PH/RV Failure
RV FAC = 18 %
RA pressure 10 mm Hg
mean PA 75 mm Hg
cardiac index 1.8 L/min
Simon et al. Clin Translat Sci 2:294-9, 9, 2009

Regional wall stress vs.
Thickness
Infund dibular En nd-Systol lic Wall Stress (kP Pa)
40
30
20
10
0
PH-C
Normal
PH-D
Infundibular End-systolic Wall Thickness (mm)
Normal
PH-C
PH-D
0 2 4 6 8 10 12 14
Simon et al. Clin Translat Sci 2:294-9, 9, 2009

RVOT ES Wall Stress vs. Wall Thickness
40
PAH without RV
Decompensation
P

RV Adapts to Increased Pressure
Loads in Response to Increased
Wall Stress
• Hypertrophy is initially heterogeneous
– Outflow track hypertrophies first because
it contracts last and thus sees the highest
wall stress during systole
•RV remodeling occurs with pulmonary
hypertension before Pra

Modeling RV Wall Strain during
Pulmonary Hypertension
1. Tension in one
principal curvature
T = ⎛ P ⎞
⎛
⎜ ab ⎝ 2 ⎟ a 1+ b2
⎠ a + ⎞
⎜
b2
⎟
⎝
2 c 2
⎠
2A 2. Applied lidto each
T ab
,TT ac
,TT ba
,TT bc
,TT ca
,TT
cb
direction a, b and c
3. Average Orthogonal ⎛
T ab
+ T ac
⎞
T a
= ⎜
⎟ ⎡ ⎛ T
Tension
⎝ 2 ⎠
a
⎞
⎜ ⎟ x 2
⎝ a ⎠ a + ⎛ T ⎞
b
⎜ ⎟ y 2 ⎛
⎢
⎜
⎣
2 ⎝ b ⎠ ⎝
T
4. Average Tension
avg
=
x 2 tA
+ y 2 + z2 at Any Point a 4 b 4 c 4
5. Product of Principal
( T gv ) 2 = T ab
T ac
+ T T 2 ba bc
+ T T 2 ca cb
Tensions a b c
( ) x 2
6. Maximal Tension
at a Point T max
= T avg
+ ( T ac ) 2 − T gv
7. Maximal Stress
( ) y 2
( ) z2
b + T ⎞
c
2 c ⎠
c 2
⎟ z2
c 2
( ) 2 σ max
= T max
max
h
Regen. Ann Biomed Eng 24:400-17, 1996
⎤
⎥
⎦

Modeling RV Wall Strain during
Pulmonary Hypertension
Modified 4 Chamber view
Short Axis view

Modeling RV Wall Strain during
Pulmonary Hypertension
Str
ress (kPa)
Thickness (mm)

Does RV Ejection Efficiency
Vary with Changes in RV end-
diastolic volume
Sometimes:
with RV overdistention,
ischemia and
pulmonary hypertension

RV Adaptation to Pressure
4CH Longitudinal Strain:
Normal patient
0%
-39%

RV Adaptation to Mild PAH
4CH Longitudinal Strain:
Pra
Ppa
7 mm Hg
40/16 mm Hg
Mean Ppa 26 mm Hg
Ppao
7 mm Hg
CI 3.73 l/min/m 2
0%
-24%

Severe PAH with Decompensated RV
4CH Longitudinal Strain
Pra 13 mm Hg
Ppa 111/51 mm Hg
M Ppa 70 mm Hg
Ppao 10 mm Hg
CI
1.3 l/min/m 2
0%
-14%

Echocardiographic Speckle Tracking
Normal
Pulm Hypertension, RV Failure
Simon et al. Congestive Heart Failure 15:271-6, 2009

Clinical i l Implications
• Right ventricular diastolic function is wedded
to LV filling and cardiac fossal restraint
– Remodelong occurs before Pra increases
–End-diastolic diastolic volume and LV diastolic compliance
– RV preload may not vary as RV EDV varies
• Right ventricular systolic function is wedded
to LV ejection
– Etiology of Backward Circulatory Failure
– Implications for LV Assist Device Use
– Maintain arterial perfusion pressure > Ppa

Some Overly Simplistic Rules
to Follow
• Decreasing RVef if not associated with an
increase in stroke volume is bad
• For cardiac output to increase RV ESV must
also increase
• The primary treatment for RV failure is to
decrease pulmonary artery pressure
• The primary rescue of RV failure is by
increasing arterial pressure > Ppa so as to
sustain RV coronary perfusion