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MYOCARDIAL VIABILITY
&
REVASCULARIZATION
MYOCARDIAL VIABILITY
&
REVASCULARIZATION
By
AHMED M. MABROUK
Consultant Interventioal Cardiologist
KFMMC. Dhahran
January
2010
Myocardial Perfusion Reserve
Resting myocardial blood flow is normal until 85% stenosis
Max myocardial blood flow begins to decline from 45% stenosis
MBF
hyperemia
MPR
rest
0
20
40
60
80
100
% diameter narrowing
Gould KL et al., Am J Cardiol 1974; 34:48-55
Historical background :
• Described by Rahimatolla & others in
the last two decades of the last
century viability ,the capacity of
survival , is an active adaptive
process of the myocardium to
conditions of low energy supply ,
• The gold standard is improved
contractile performance after
revascularization.
Definitions
Viability :
Myocardium that demonstrates abnormal function
at rest and that improves with revascularization.
Preserved cell membrane integrity, preserved
glucose metabolism and inotropic reserve .
Hibernation :
Chronic condition of contractile dysfunction due to
longstanding low perfusion in which restoration of
myocardial blood flow results in recovery of
function.
Patients with evidence of viability
treated medically had an annual
mortality of 16% vs 3.2% in
revascularized patients .
Patients without viable myocardium
have similar ,or better outcomes with
medical therapy as compared with
revascularization.
Stunning :
Transient loss or reduction in myocardial contractility
resulting from transient reduction in blood flow ( in the
absence of irreversible damage ) , it may remain hours,
days, or months despite return of normal or near normal
blood flow.
Gold standard is recovery of function with time.
Ischemia , stunning , hibernation , scarring, and normal
myocardium may coexist in the same patient.
In patients with viable myocardium , revascularization :
has been shown to :
Improve functional class.
Reduce angina.
Decrease mortality.
ASSESSMENT
DOBUTAMINE
STRESS
ECHO.
Interpretation by regional
wall motion (WM) analysis
Interpretation
Rest
Stress
Normal WM and
contractility
Hyperdynamic
Normal
Normal WM
New WM abnormality or lack of hyperdynamic WM
Ischemia
WM abnormality
Worsening ( hypokinesis , akinesis )
dyskinesis )
Ischemia
WM abnormality
Unchanged
Infarct
Akinetic WM
Improved to hypokinetic or to normal WM, biphasic
response
Viable
myocardium
( akinesis ,
Recovery of contractility of akinetic
myocardium after revascularization is
better predicted by increased
contractility seen on dobutamine stress
echocardiography than by thallium and
PET.
HOWEVER :
Dobutamine is not as sensitive as
thallium uptake or PET for detecting
myocardial viability.
NUCLEAR IMAGING
Characterization of the defects :
Fixed :
- No uptake at rest & stress.
Scar or severely ischemic viable
myocardium.
- How to differentiate ?!
Reversible:
- Ischemic myocardium.
Partially reversible :- Mixture of scar and
ischemic myocardium.
Artifacts :
- Breast attenuation.
- Diaphragmatic attenuation.
- More commonly seen with
thallium.
Stunned Myocardium
LIMITED PERFUSION DEFECT&
MORE EXTENSIVE RWMA.
PET (Positron Emission
Tomography)
• Allows simultaneous evaluation of blood flow
imaging
(i.e. perfusion) and metabolic activity .(using FDG)
.
• It's now considered as the gold standard for
identifying viable myocardium .
• Patterns : • Normal
- normal flow - normal metabolism.
• Viable myocardium
- reduced flow - normal or increased
metabolism : (Mismatch).
• Scar
- reduced flow - reduced metabolism : (Match).
VIABILITY
by
MRI
GADOLINUM
ENHANCEMENT
sensitivity : 94 %
specificity : 84 %
DCE compares well with
fluorodeoxyglucose positron emission
tomography (FDG-PET), the "gold
standard" for myocardial viability
imaging.
DCE has a sensitivity of 94% and a
specificity of 84% when compared with
FDG-PET in patients with ischemic
cardiomyopathy and LV dysfunction.
DCE performs well as resting thallium201 myocardial perfusion imaging with
single photon emission computed
tomography (SPECT) for detecting
transmural infarctions (specificity 98%
and 97%, respectively) but is more
accurate in detecting regions of
subendocardial infarction , which are
missed by radionuclide techniques in
47% of myocardial segments and 13% of
patients.
Advantages of
MRI
Radionuclide techniques
expose patients to a
substantial amount of
ionizing radiation, and
PET is performed by
relatively few specialized
centers.
examples
Dark: viable
Bright: non-viable
Target: no re-flow
Viability study
Viability
Study
4293701
Results of cardiovascular MRI with delayed contrast enhancement in
myocardial infarction (MI)
ACUTE
MI
OLD MI
Marcu, C. B. et al. CMAJ 2006;175:911-917
AKINETIC
NON-
VIABLE
DYSKINETIC
VIABLE
NONTRANSMURAL
SUBENDOCARDIAL D.C.E.
PRESUMABLY
VIABLE
Circulation 2003 108:116-117
Wall thinning
Dyskinesia
No systolic thickening
Profound
Microvascular
obstruction
Complete LAD obstruction
Myocard. Rupture
Microvasc. Obs.
Platelet & fibrin.
dobutamine
0 μg/kg/min
10 μg/kg/min
40 μg/kg/min
Bellenger N et al. Heart 2006;92:1206.
Segment No.
Relationship between 201Tl
uptake and delayed contrast
enhancement in MRI
160
140
120
100
80
60
40
20
0
DC Score
0
1
2
3
4
Normal
Mild
decreased
Moderate
decreased
Thallium Uptake
Severe
decreased
Absent
(A)
201Tl
SPECT
(B) Delayed enhanced MRI
rest
delay
rest
delay
Mismatch between SPECT and MRI
Mismatch between SPECT& MRI
Influence of transmural extent of delayed
contrast enhancement on recovery of
regional function in
97 dysfunctional segments at baseline
Systolic Wall Thickening Ratio (%)
Transmurality
Baseline
Follow-Up
Difference
P
0 － 25% (n=52)
9.7  14.8
28.0  12.9
17.9  15.6 < 0.0001
26 － 50% (n=32)
6.2  13.9
15.2  15.3
9.0  18.6
0.01
51 － 75% (n=9)
0.1  6.0
3.7  19.0
3.6  17.9
0.56
76 －100% (n=4)
-11.9  17.1%
-1.8  22.8
10.2  29.7 0.56
How much viable
myocardium predicts
recovery ?
• In a large study the average
was found 22% .
• Definite recovery is expected
when we get > 4 viable segments
CONCLUSION
Delayed enhanced MRI has a
better diagnostic power of
myocardial viability and
predictive value of functional
recovery than 201-Tl SPECT
REVASCULARIZATION
for
SCARRED MYOCARDIUM ?
CASE PRESENTATION
The enigma of
Open artey
hypothesis
 65 years old lady referred to our hospital
after thrombolysis for STEMI complicated
by
acute pulmonary edema.
 R.F. : DM , HTN , and DYSLIPIDEMIA
 On Ex. : She is sweating ,cyanosed , and in
in respiratory distress, with no chest pain.
V. S. : p : 115 bpm. RSR. B.p :161/89 mmHg.
R.R.:42/m. O2 sat.:76% on O2 4L/m. by
nasal mask.
 Cadiac auscultation : S1 ,S2 , S4 , and no
murmurs.
 Chest auscultation :bilateral widespread
rales, going with acute pulmonary oedema.
 ECG. : 5 mm. ST-seg. Elevation in V1-V6.
 Cardiac enzymes : normal.
 Echo. :Dilated mod. to severe LV
impairment, dyskinetic ant. ,anteroseptal,
and apical segments. Increased LV f.p. ,
and a large LV aneurysm , with no
thrombus.
Coronary angio. After stabilization.
Showed :
100% LAD with prox. Calcium.
50 % prox. Dominant CX.
Diffusely diseased small RCA.
Large LV aneurysm
 Decision :
 Schedule for viability.
 A nuclear study ( ? ) showed no viability
in LAD territory .
 Medical treatment :She improved , and
successfully discharged home on maximal
anti-failure medications.
 However, few weeks later she repeatedly
presented with several episodes of severe
SOB and after admission at the local
Hospital, was referred back to us again
with the diagnosis of recurrent A P O.
At presentation to ER
Again
She was in
Acute pulmonary edema.
 The case was discussed for
possible :
1-Revascularization with LV
aneurysmectomy ( SVR ).
2- Trial of PCI to CTO of LAD.
PCI to LAD was
attempted after
stabilization.
The patient was discharged home again
after the procedure, and was electively
admitted for control coronary and LV
angio. after one year during which she
remained asymptomatic on medical
treatment.
Repeat Echocardiography :
showed mildly improved LV function .
DOES SHE STILL NEED
ANEURYSMECTOMY ?
Yes if :
Failure of medical treatment with :
Persistent heart failure.
Life threatening arrhythmia.
Take Home Message
Ischemia , stunning , hibernation , scarring,
and normal myocardium may coexist in the
same patient.
In patients with viable myocardium ,
revascularization :
has been shown to :
Improve functional class.
Reduce angina.
Decrease mortality.
Viability assessment :
Not so accurate by Dobutamine Stress
Echo. ( LOW SENSITIVITY ),unless
we have a definite contractile reserve.
Demanding and costing by Nuclear
and MRI.
However rewarding in terms of
recovery after revascularization.