a physiological response to central hypovolemia?• hypovolemia or forced vasodilation •neurogenic...
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![Page 1: a Physiological Response to Central Hypovolemia?• Hypovolemia or Forced Vasodilation •Neurogenic OH •Autonomic vasoconstrictor failure due to inadequate release of . norepinephrine](https://reader031.vdocuments.mx/reader031/viewer/2022041704/5e43f22923fe8a252a63bcc9/html5/thumbnails/1.jpg)
Differential Diagnosis of OI with Excessive Upright
tachycardia ‐
a Physiological Response to Central
Hypovolemia?
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Normal Circulatory Response to Orthostasis
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Normal Segmental Changes in Normal Segmental Changes in Impedance and volume with TiltImpedance and volume with Tilt
0 200 400 600 800 1000
Time (sec)
10
12
14
16
Impe
danc
e (O
hms)
0 200 400 600 800 1000
Time (sec)
0.70
0.83
0.97
1.10
Frac
tiona
l Vol
ume
Cha
nge
0 200 400 600 800 1000
Time (sec)
14
15
16
Impe
danc
e (O
hms)
0 200 400 600 800 1000
Time (sec)
0.90
1.00
1.10
Frac
tiona
l Vol
ume
Cha
nge
0 200 400 600 800 1000
Time (sec)
20
22
24
26
Impe
danc
e (O
hms)
0 200 400 600 800 1000
Time (sec)
0.90
1.00
1.10
Frac
tiona
l Vol
ume
Cha
nge
0 200 400 600 800 1000
Time (sec)
100
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120
Impe
danc
e (O
hms)
0 200 400 600 800 1000
Time (sec)
0.90
1.00
1.10
Frac
tiona
l Vol
ume
Cha
nge
Thorax Splanchnic Pelvic Leg
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Orthostatic IntoleranceThe presence of one or more symptoms, e. g., lightheadedness, dizziness, nausea, breathlessness, and vision change, linked specifically to assuming or maintaining upright posture, and symptoms abate once supineEtiology is not a criterion.
Chronic Orthostatic IntoleranceOrthostatic Intolerance for at least 3 months with functional impairment
POTSChronic Orthostatic Intolerance with excessive postural tachycardia (at least 40 bpm change within 10 minutes on standardized passive tilt testing) without significant sustained hypotension in the absence of an alternative explanation.If a specific cause is found (e.g. Addison’s Disease) It is no longer called POTS. But the POTS Response is still present.
POTS is a Disease vs POTS is a Physiological Response
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Major Variants of Orthostatic Intolerance Comprise a Differential Dx of POTS
•Chronic Bedrest
•Initial Orthostatic Hypotension
•Orthostatic Hypotension
•Chronic Orthostatic Intolerance Postural Tachycardia Syndrome (POTS) Chronic OI
•Postural Vasovagal Syncope/I.S.T.
•Any Condition that Promotes Central Hypovolemia
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Gravitational Deconditioning
• Reduced blood volume• Cardiovascular remodeling• Different Regional blood volume redistribution• Reduction in the response to
norepinephrine/MSNA (and other pressors)
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Initial Orthostatic Hypotension
0 20 40
M AP ( mmHg)
0
100
200
Arte
rial
Pre
ssur
e (m
mHg
)
0 20 40
M AP ( mmHg)
50
100
150
Hear
t Ra
te (
bpm
)
AP
HR
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M AP ( mmHg)
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Pre
ssur
e (m
mHg
)
0 20 40
M AP ( mmHg)
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Hear
t Ra
te (
bpm
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AP
HR
Standing
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Orthostatic Hypotension (OH) is Easy to Understand
•Blood pressure falls sufficiently to impair brain blood flow
•Non-neurogenic OH• Hypovolemia or Forced Vasodilation
•Neurogenic OH •Autonomic vasoconstrictor failuredue to inadequate release of norepinephrine from sympathetic vasomotor neurons.
0 100 200 300 4000
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Art
eria
l Pre
ssur
e (m
mH
g)
0 100 200 300 400
Time (sec)
50
100
150
Hea
rt R
ate
(bpm
)
AP
HR
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Chronic Orthostatic Intolerance: Postural Tachycardia Syndrome (POTS)
Schondorf and Low. Idiopathic postural orthostatic tachycardia syndrome: an attenuated form of acute pandysautonomia? Neurology 1995;43:132-137
Day-to-Day Symptoms of OI++
Excessive Tachycardia(without Hypotension)Adults Δ>30 or HR>120bpm within 10minAdolescent – Δ>43
(IOH a confound)?+
Concurrent Symptoms of OIduring testing
Improved by Recumbence
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Time (sec)
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Hea
rt R
ate
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)
0 100 200 300 400 500 600
Time (sec)
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MA
P (m
mH
g)
HR
MAP
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What’s This?
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rt R
ate
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Time (seconds)
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Blo
od P
ress
ure
(bpm
)Tilt up
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IOH
HR
BP
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Postural Vasovagal Syncope in the YoungDefined by Clinical History
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Time (sec)
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ate
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Time (sec)
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P (m
mH
g)
Tilt Up Tilt Down
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MAPSlow ↓
BP
Rapid ↓
BP
1 2 3Transient loss of consciousness and postural tone due to global cerebral hypoperfusion and characterized by rapid onset, short duration, and spontaneous recovery.
Almost always the result of systemic hypotension
Very Common (~40%)
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