Download post CABG Myocardial Infarction : Latest Diagnostic and

Susana G. Garcia MD




Review the current definition, risk factors,
clinical impact and incidence of PMI
Describe the different clinical presentation of
PMI and how this dictate the goal and
approach to diagnosis and treatment of PMI
Describe the use and limitation of different
diagnostic tools in the evaluation of
perioperative ischemia and infarction
Present current data on novel diagnostic tools
and therapies used in PMI


Present algorithmic approach to post CABG
patients with signs of ongoing ischemia
Discuss the recent guideline on:
Resuscitation of cardiac arrest after cardiac surgery
 Mechanical Circulatory Support
 Mgt of Early Graft Failure

“ an increase in biomarker values to > 5x the URL
during the first 72 h ff CABG, when associated
with:
 the appearance of new pathological Q-waves or new
LBBB
or
 angiographically documented new graft or native
coronary artery occlusion
or
 imaging evidence of new loss of viable myocardium”








Age >70 years (ESC)
Female gender
Renal Failure
Diabetes
Peripheral artery
disease
Emergency CABG
Repeat CABG
Preop MI







Preop Ischemia
Cardiomegaly
Diastolic dysfunction
Prior MI
Use of nsaid
No bb , no statin, no
asa
Severe
LVdysfsn(EF<35%) or
cardiogenic shock





Long CPB time
CABG combined with other surgery
Intraop ischemia
Surgical technique
Inadequate protection

High Hct (Spiess
B. D. et al.; J Thorac Cardiovasc Surg
1998;116:460-46)




Rapid arrhythmias
Hypertension
Hypotension
Tachycardia from




Volume depletion
Blood loss
Inotropes. Pressores
Pain


PMI is associated with
adverse outcome
Available data
suggests a direct
correlation between :


the amount of
myonecrosis
the likelihood of
reduced survival


Because of the wide variability in the
definitions used, the incidence of reported MI
is highly variable
Incidence= of 2–40%


is not straightforward
In the early period the
critical issue is :

to determine whether
there is acute severe
ischemia/infarction due
to
 Early Graft Failure
 Acute Native Coronary
Thrombosis

that warrants urgent
intervention.
Subclinical Enzyme
Leak
Persistent Signs of
Ischemia -Hemodynamically
Sable
Persistent Signs of
Ischemia-Hemodynamically
Unstable
Cardiogenic Shock
/Cardiac Arrest


Some degree of
myocardial injury
virtually always occurs
after CABG
At one end of the
spectrum, the myocardial
injury is manifested as a
small troponin release
with no clinical sequelae

Troponin release may be
from:
 Myocardial trauma
 Imperfect myocardial
protection
Subclinical Enzyme
Leak
Persistent Signs of
Ischemia -Hemodynamically
Sable


Persistent Signs of
Ischemia-Hemodynamically
Unstable
Cardiogenic Shock
/Cardiac Arrest

At the other end of the
spectrum, is severe
myocardial ischemia or
infarction that is
associated with
hypotension, LCOS and
ventricular arrhythmias
This latter situation
demands urgent
investigation because it
may represent an acute
obstruction of a coronary
graft or native coronary
vessel
Timely intervention may
be life saving


To search for signs
of
ischemia/infarction
which may be due
to
 Early Graft Failure
 Acute Native
Coronary
Thrombosis
that warrants urgent
intervention.

Angina (not reliable):


Pain from myocardial ischemia is very difficult to
distinguish from wound pain
Most are sedated and ventilated during the early
post op period
 Cannot report symptoms

Hemodynamic Instability:
Has many causes
 But one important to consider is ischemia


Hemodynamic Instability

Acute ischemia of severity sufficient to cause
hypotension or low cardiac output state :
 implies a large region of threatened myocardium
 warrants urgent intervention and treatment

Swan Ganz Catheter Measurements suggestive
of LCOS
 Increased in PA pressure
 Increased PCWP
 Low CO

New significant Q waves





ST segment depression



≥ 0.04 second duration in any two
leads except III and aVR
may be indicative of full-thickness
MI
but they take 24 to 48 hours to
develop
therefore not useful in the
assessment of suspected ischemia
≥ 1 mm, measured 0.06 sec after the
J point
if it occurs, develops concurrently
with myocardial ischemia.
ST segment elevation, with the
subsequent new Q waves after
CABG surgery

may provide a useful marker of
acute ischemia.

Diffuse upsloping ST elevation



New LBBB or AV block



Pericarditis
do not mply ischemia.
may indicate acute ischemia,
but they too are common following cardiac surgery.
Recurrent Ventricular Tachycardia

strongly suggestive of severe acute ischemia.


Despite the limitations of ECG analysis,
the finding of ST segment depression or
elevation that is limited to a specific coronary
territory


+ hemodynamic instability / ventricular
arrhythmias
is strongly suggestive of acute ischemia.



All patients with suspected myocardial
ischemia after CABG surgery should undergo
urgent echocardiograms
—preferably a transesophageal
echocardiogram examination looking SWMAs
SWMAs


are more sensitive and specific for myocardial
ischemia than ECG changes
but they can be difficult to interpret in postoperative
patients.
Troponin I



a value > 20 μg/l is associated with prolonged
hospital stay
indicative of early graft failure
Salamonsen RF,. Clin Chem 2005; 51:40-46.

Troponin T

a value > 1.58 μg/l at 18 to 24 hours after surgery is
predictive of adverse outcome, including death.
Januzzi JL. J Am Coll Cardiol 2002; 39:1518-1523.



A limitation of making judgments based on
troponins is that peak levels occur at about 24
hours after an ischemic event
Troponin T peaks a little later than troponin I
Thus, these markers are not ideal for the
evaluation of acute ischemia soon after surgery.

CKMB
is less sensitive and specific than the troponins
 takes nearly 24 hours to reach peak levels.


Myoglobin levels
peak within 6 to 12 hours of ischemic injury
 but are poorly predictive of outcome.

Costa MA(ARTS trial). Circulation 2001; 104:2689-2693.

cTnI elevation after CABG discriminates patients:
with graft-related PMI
 non-graft-related PMI
 without PMI



however, not earlier than 12 h after surgery.
This detection window is far too long to enable
timely rescue strategies

Reported to detect
ischemia within the first
30 minutes:
Heart type fatty acid
binding
protein(hFABP)
 Ischemia Modified
Albumin


May enable early
intervention aimed at
restoring myocardial
flow


If ischemia is
suspected on the
basis of
hemodynamic
instability or
ECG changes
urgent
transesophageal
Hypotensive: /
Signs of Ongoing
Ischemia by ECG
Initiate Mgt for
Arrhythmia,
Ischemia. LCOS
Tamponade
/Hemodynamic
Deterioration +/- Ischemia
TEE
No Tamponade:
+Acute Ischemia
Intensify Tx of Spasm +
Optimize Filling Pressure;
Inotropic Support; IABP
Re-exploration :
Revision of Graft
/ Evacuation of Clot or
Hematoma; Ligation of
Bleeders
No response
Urgent
Coronary
Angiography
PCI vs Surgical
depending on
anatomy
2010 ESC Guideline in Myocardial Revasc


If ischemia is
suspected on the
basis of
hemodynamic
instability or
ECG changes
urgent
transesophageal
Hypotensive: /
Signs of Ongoing
Ischemia by ECG
Initiate Mgt for
Arrhythmia,
Ischemia. LCOS
Tamponade
/Hemodynamic
Deterioration +/- Ischemia
TEE
No Tamponade:
+Acute Ischemia
Intensify Tx of Spasm +
Optimize Filling Pressure;
Inotropic Support; IABP
Re-exploration :
Revision of Graft
/ Evacuation of Clot or
Hematoma; Ligation of
Bleeders
No response
Urgent
Coronary
Angiography
PCI vs Surgical
depending on
anatomy

Class I Recommendations

to reduce the risk of perioperative myocardial
ischemia and infarction, management targeted at
optimizing the determinants of coronary arterial
perfusion
 heart rate
 diastolic or mean arterial pressure, and
 right ventricular or LV end-diastolic pressure

is recommended (Level of Evidence: B)
2011 ACC AHA CABG Guideline
Intraoperative TEE
PA Cath
ECG
Intraoperative Graft Assessment

TEE : useful for evaluation
of








LVEDA/LVEDV
EF and CO
LVEDP
Valve Function
PHTN
Shunts
Complications
Ischemia ( New RWMA)
 guide surgical therapy
 lead to
 revison of failed conduit
 placement of additional
grafts not originally planned

Potentially superiority
over Swan PCWP or
PADP in assessment of
LVEDP in the early post
op period
Fontes ML, Bellows W, Ngo L, et al.
Assessment of ventricular function in
critically ill patients: limitations of PAC
J Cardiothorac Vasc Anesth. 1999;13:521–7.


Live 3DTEE
Time to minimal
regional volumes
 normal subject
 synchronous
 in a heart failure patient
 dispersed
Translational Research Volume 159, Number 3





Doppler Tissue
Imaging
Real Time 3D TEE
Speckle Tracking
Cost effectiveness has
not been determined
Too complex for
routine use


Graft patency strongly influences early and late
outcomes after CABG.
Transit Time Flow Measurement
quantitative volume flow technique,
 cannot

 define the degree of graft stenosis
A randomized comparison of intraoperative
ICG angiography and transit-time flow measurement to
detect technical errors in coronary bypass grafts
Journal of Thoracic and Cardiovascular Surgery,Volume 132, Issue 3, September
2006, Pages 585-594
Nimesh D. Desai

LIMA
Anastomosis
LAD

Diagnostic accuracy for
detecting clinically
significant graft failure
ICG > Transit-time US flow
measurement.

LIMA
Anastomosis

High inter-rater reliability
for graft patency between
surgeons.
For graft stenosis >50%


Sn=100%
Sp=100%
LAD
Desai JACC Vol 46, Issue 8, 18 Oct 2005, pp 1521-25

has the capability of serving
both as:



a complete surgical OR
a cath laboratory.
It allows for
routine completion
angiogram following
CABG surgery
 identifies abnormal grafts,
providing the opportunity
to revise them with PCI
surgery before leaving the
OR.


Semin Thorac Cardiovasc
Surg 21:207-212
The Graft Imaging to Improve Patency
(GRIIP) clinical trial results
The Journal of Thoracic and Cardiovascular Surgery, Volume 139, Issue 2,
February 2010, Pages 294-301.e1
* Steve K. Singh, MD, MS


Is Routine
intraoperative graft
assessment safe?
Does it lead to a
marked reduction in
graft occlusion 1 year
after CABG?

Yes

No
Subclinical Enzyme
Leak
Persistent Signs of
Ischemia -Hemodynamically
Sable
✓✓Persistent Signs of
Ischemia-Hemodynamically
Unstable
Cardiogenic Shock
/Cardiac Arrest



Incidence 0.7-2.9%
Potentially reversible
If treated promptly has a high survival rate
 54-79%

Key to successful resuscitation
 Early resternotomy
 esp if + tamponade (external chest compression not
effective)
Cardiac Arrest
Activate
Surgical Team
for Emergency
Resternotomy
Resuscitation based on 2010 ACC
AHA or ESC CPR Guideline
following Cardiac Surgery
Initial
Stabilization
Hemodynamically
Unstable
TEE: + tamponade
Early
Resternotomy +
Resumption of
CPB
TEE : No Tamponade
+ new Ischemia
Coronary Angiography
PCI vs Resternotomy
depending on findings



External chest compression should be started
immediately in all patients who collapse
without a pulse
Correct reversible cause (K, volume, bleeding,
O2, acidosis, ischemia)
During CPR…


IABP changed to pressure trigger
If unable to attain SBP of at least 80mmHg with
effective compression: may indicate tamponade
 Do early resternotomy
3 quick defibrillation

3 failed shocks

Emergency Resternotomy

Further defibrillation as indicated should be
performed with internal paddles at 20 joules after
resternotomy

Amiodarone 300mg after 3rd failed defibrillation
attempt (but don’t delay resternotomy)
Correction of Ischemia, rather
than giving Amiodarone, is
more likely to achieve
myocardial stability”



An integral part
of resuscitation
after cardiac
surgery
Improved survival and
QOL are well
documented with rapid
sternotomy
Should be standard part
of resuscitaton within
10 days after cardiac
surgery


Survival to discharge 3256%when CPB is
reinstituted in the ICU
Survival rates decline
rapidly when procedure
delayed for >24 hrs
Indications:
correct surgical bleeding
Repair graft occlusion
Rest myocardium
Cardiac Arrest
Activate
Surgical Team
for Emergency
Resternotomy
Resuscitation based on 2010 ACC
AHA or ESC CPR Guideline
following Cardiac Surgery
Initial
Stabilization
Hemodynamically
Unstable
TEE: + tamponade
+ Acute Ischemia
Early
Resternotomy +
Resumption of
CPB
Coronary Angiography
Graft Revision / Evacuation of
Effusion
Hemodynamic Stability
TEE : No
Tamponade/Hypovolemia
Unstable
PCI vs Resternotomy
depending on findings

Optimal treatment demands the ff to prevent
end organ failure and death:

Hemodynamic support (improve systemic
perfusion)
 Pharmacologic
 Mechanical


Invasive hemodynamic monitoring
Early Reperfusion
2010 ESC/EACTS Myocardial Revascularization Guideline
2009 ACC/AHA Guideline focused update on Heart Failure

ECMO



Used for cardiac arrest refractory to standard
resuscitation measures
9 case series have reported improved survival
after cardiac surgery
Recommendation: “In post cardiac surgery patients
who are refractory to standard resuscitation
procedure, mechanical circulatory support ( ECMO
and CPB) may be effective in improving outcome”
(Class IIb,LOE B)
2010 AHA Guideline for CPR and ECC


IABP in Perioperative Myocardial Dysfunction
2011 ACCF AHA CABG Guideline:


Class II a (LOE B)
In the absence of severe PAD, the insertion of IABP
is reasonable to reduce mortality in CABG patients
who are considered to be at high risk
 Undergoing reoperation
 LVEF<30%
 Left Main Disease
Cardiac
Arrest
Activate Surgical
Team for
Emergency
Resternotomy
Hemodynamically
Unstable
Resuscitation based on 2010
ACC AHA or ESC CPR
Guideline following Cardiac
Surgery
TEE: +
tamponade
+ Acute Ischemia
Early Resternotomy +
Resumption of CPB
Coronary Angiography
Graft Revision / Evacuation of
Effusion
Hemodynamic
Stability
Initial
Stabilization
TEE : No
Tamponade/Hypovolemi
a
Unstable
Consider
ECMO
PCI vs Resternotomy
depending on findings



Usually have uneventful postoperative course
but are at increased risk for adverse events and
should be kept in a highly monitored
environment (ICU) during their early
postoperative periods.
Prior to discharge to the ward, such patients
should be medically optimized with:
β blockers
 ACE inhibitors
 antiplatelet agents (aspirin ± clopidogrel),
 statins.


Prevention of Perioperative Myocardial Injury






BB should not be stopped to avoid acute ischemia
Avoid NSAIDS
Resumption of ASA 6 hours post op
Complete Revasc
Arterial Grafting to LAD
Graft flow measurement /evaluation (Class 1C)
 Graft flow <20mL/min and PI >5 mandate graft
revision

Volatile Anesthetics
 protective in the setting of myocardial ischemia and
reperfusion
2010 ESC/ EACTS Myocardial Revasc Guideline
✓✓Subclinical
Enzyme Leak
Persistent Signs of
Ischemia -Hemodynamically
Sable
✓✓Persistent Signs of
Ischemia-Hemodynamically
Unstable
✓✓Cardiogenic Shock
/Cardiac Arrest

Usually non-graft related

Poor Myocardial Protection
 Inadequate cardioplegic perfusion



Coronary Air
Incomplete revascularization
Global Ischemic Reperfusion Injury (IRI) induced by:






Aortic cross-clamping and de-clamping
SIRS from CPB
Distal microembolization
Surgical Manipulation of the Heart
Genetic susceptibility to acute IRI
Sometimes Graft Related



Suboptimal graft flow
Spasm
Failure
Goals:
1.
2.
Is there recent infarction?
If yes, Risk stratification to determine
need for early vs conservative mgt
•
•
•
•
Cardiac Enzymes
ECG
Non-invasive Imaging
Role of MRI


used to detect, characterize, and quantify PMI
during CABG surgery.
Helps in risk stratification in hemodynamically
stable patients

Electrocardiograms


changes are difficult to interpret following surgery
unless there is the appearance of a new Q-wave MI
Echocardiography

New RWMA
 which represent myocardial stunning rather PMI
 To predict graft failure :Sn=20% Sp=25%

Myocardial nuclear scanning


only detect obvious perfusion defects arising from
graft or native coronary artery occlusion
will not detect diffuse PMI



Can be used to detect new loss of viable
myocardium post-CABG surgery
can therefore be used to detect perioperative MI.
Delayed gadolinium contrast enhancement by
cardiac MRI (DE-CMR)

gold-standard imaging technique for visualizing
myocardial fibrosis or infarction.

Can also characterize, and quantify
PMI.


provide clues to the underlying aetiology of
myocardial injury.
three patterns of DE-MRI have been described:

(i) a transmural MI in a coronary artery territory:
 early graft or native coronary artery occlusion

(ii) a sub-endocardial MI:
 distal coronary embolization

(iii) diffuse patchy areas of myocardial necrosis:
 acute global IRI or other causes.
Pegg TJ, et al. A randomized trial of on-pump beating heart and conventional cardioplegic arrest in
CABG patients with impaired LV function using CMRI and biochemical markers. Circulation
2008;118:2130–2138.


“the presence of ne
PMI on CMR
following either
CABG or PCI
was associated with
a 3.1-fold increase
MACE
 Reduced event free
survival

Rahimi K et al Prognostic value of coronary revascularisation-related
myocardial injury: a cardiac MRI study. Heart 2009;95:1937–1943.



Preoperative MRI scan in short axis plane
 in a 76yo DM patient with dyspnoea.
 underwent CABG for 3VD
Postoperative MRI short axis (B)
 Showed new inferior and infero-septal hyperenhancement (white arrow).
He died of heart failure 12 months after
Rahimi K et al Prognostic value of coronary revascularisation-related
myocardial injury: a cardiac MRI study. Heart 2009;95:1937–1943.
“MR examination of patients with sternal wires
is generally considered to be safe.”
Circulation. 2007; 116: 2878-2891
From the Committee on Diagnostic and Interventional Cardiac
Catheterization, Council on Clinical Cardiology, and the Council
on Cardiovascular Radiology and Intervention:
Glenn N. Levine MD, FAHA;
P - post CABG PMI pts
I - Acadesine infusion
O - reduced


Severity of PMI from
IRI
mortality rate after 2
yrs of ff up
M - RCT
Post-Reperfusion MI Long-Term Survival Improvement
Using Adenosine Regulation With Acadesine
Dennis T. Mangano, etal ,J Am Coll Cardiol 2006;48:206 –14
Hemodynamically Stable: with ECG changes suggest
Ischemia or Infarct (new LBBB or Q wave)
Biomarker Rise >/= 5x the URL
(use rapid assay point of care test)
Biomarker Rise <5x the URL (use rapid
assay, point of care test)
TTE
Repeat after 8
hours
Equivocal
Cardiac MR or
Nuclear MPI
Confirms acute
global IRI
Consider
Acadesine
Infusion
confirms early graft or native
coronary artery occlusion
Confirmed Ongoing Ischemia: New wall motion
abnormality with large area of myocardium at risk+
worse LV fxn
Biomarker rise
<5x URL
Coronary
Angiography
Repeat in 4
hours
PCI vs Resternotomy for graft
revision depending on findings
Biomarker <5x
URL
Maximize Ischemic nd Post MI
Regimen:+Early Antiplatelet and
Statin Therapy
Factors to Consider






Hemodynamically unstable
Concomittant tamponade or bleeder
Unsuitable Vessels for PCI (High Syntax Score)
Number of Occluded Bypass Grafts
Available IMA for grafting totally occluded
vessels
Good Distal Targets
2011 ACCF AHA SCAI PCI Guideline

Hemodynamically stable
Limited areas of Ischemia
Patent graft to LAD

Suitable PCI targets


(low syntax score)
 Mechanism of graft closure can be fixed by PCI

 Kinking
 Thrombosis
 Anastomotic stenosis

Co-morbid conditions (High Euro or STS score)


Increased risk of distal embolization MI and
no reflow
PCI of de novo SVG stenosis

High risk bec:
 Atheroma is friable embolization


GPI- less effective for SVG than native arteries
Combined data support use of distal embolic
protective device during SVG PCI (Class I-A)


Class II a ; LOE B
Hybrid coronary revascularization (defined as the
planned combination of LIMA-LAD artery grafting
and PCI of >/=1 non LAD coronary arteries) is
reasonable in patients with 1 or more of the ff:

Limitation to traditional CABG
 Heavily calcified prox aorta
 Poor target vessels for CABG (but amenable for PCI)
Lack of suitable graft conduits
 Unfavorable LAD artery for PCI

 excessive vessel tortuosity or CTO
2011 ACCF AHA SCAI PCI Guideline





Perioperative MI is associated with adverse short
and long term clinical outcome
PMI may present as asymptomatic enzyme leak to
cardiogenic shock
Goals of therapy depends on clinical presentation
Early detection and intervention of graft failure is
key to restore myocardial flow and prevent
consequences of PMI
Latest guideline recommends :
PCI > Redo CABG in the mgt of graft failure
 heart team approach in the determining the optimal
definitive mgt of graft failure

Post CABG with Signs
of Ongoing Ischemia
Hymodynamically
Unstable:
Cardiac
Arrest/Shock
VT/VF,New
Q/LBBB,
ST, LCOS
Hemodynamically
Stable:
With Signs
of Ongoing
Ischemia
Without
Signs of
Ongoing
Ischemia


Vary depending on initial presentation
the critical issue is :

to determine whether there is acute severe
ischemia/infarction due to
 Early Graft Failure
 Acute Native Coronary Thrombosis


that warrants urgent intervention.
Patients presenting with hemodynamic
instability or signs of ischemia are more likely
to have graft failure and warrant early
intervention to save viable myocardium and
reduce post op mortality risk
Post CABG with Signs
of Ongoing Ischemia
Hymodynamically
Unstable:
Cardiac
Arrest /Shock
VT/VF, ST,
LCOS
Hemodynamically
Stable:
With Signs
of Ongoing
Ischemia
Without
Signs of
Ongoing
Ischemia
Post CABG with Signs
of Ongoing Ischemia
Hymodynamically
Unstable:
Cardiac
Arrest/Shock
VT/VF, ST,
New Q wave/ LBBB
LCOS
Hemodynamically
Stable:
With Signs
of Ongoing
Ischemia
Without
Signs of
Ongoing
Ischemia

Urgent TEE to :
Confirm ongoing
ischemia
 Rule out Tamponade


Hypotensive: with Signs of
Ongoing Ischemia
Mgt of

ischemia
 Nitrates
 Optimize O2
 Transfusion


TEE
arrhythmia
LCOS

Optimiize filling pressures
 Inotropic support
 IABP
Tamponade /Hemodynamic
Deterioration
Re-exploration :
Revision fo Graft
/ Evacuation of Clot or Hematoma;
Ligation of Bleeders
No Tamponade: Large
area of myocardium at
Risk/ Some Response to
Conservative Mgt
Aggressive Tx of Spasm +
Urgent Coronary
Angiography
PCI vs Surgical vs Hybrid
depending on anatomy

CLASS I



Intraoperative TEE should be performed for
evaluation of acute, persistent and life-threatening
hemodynamic disturbances that have not responded
to treatment
LOE B
CLASS II


Intraoperative TEE is reasonable for monitoring of
hemodynamic status, ventricular fxn and RWMA
and valvular fxn in patients undergoing cabg
LOE B
What’s the role of Hybrid
Revascularization?



Defined as planned combination of LIMA-to –
LAD artery grafting and PCI of >/=1 non LAD
coronary arteries
Intended to combine the advantages of CABG
( durability of LIMA graft) and PCI
May be performed in a hybrid suite in one
operative setting or as a staged procedure


Class II a ; LOE B
Hybrid coronary revascularization (defined as the
planned combination of LIMA-LAD artery grafting
and PCI of >/=1 non LAD coronary arteries) is
reasonable in patients with 1 or more of the ff:

Limitation to traditional CABG
 Heavily calcified prox aorta
 Poor target vessels for CABG (but amenable for PCI)
Lack of suitable graft conduits
 Unfavorable LAD artery for PCI

 excessive vessel tortuosity or CTO