Coronary Artery
Bypass Grafting in
Cardiac Failure
Dr. Johan van der Merwe
Registrar
University of Pretoria
Introduction

USA statistics


385 000 new cases per year
159 percent increase in
hospitalization rate since 1993
 Severe economic implication
(1997 report)



40-70% = Ischemic CMO

Terminal disease




Causes of cardiomyopathy
$5,501 was spent for every
hospital-discharge diagnosis
$1,742 per month was
required to care for each
patient after discharge
Annual total cost of $4.5
billion
1 year mortality 20%
5 year mortality 45-60%
10 year survival rare
45% of transplant recipients
Relevant coronary anatomy

Left system

Right system
Natural progression of
ischemic
cardiomyopathy
Initial infarct (immediate)

0-30 minutes = reversible



Mitochondrial swelling and
cristae distortion
Relaxation of myofibrils
After 60 minutes =
irreversible



Sarcolemma disrupts
Margination of chromatin
Mitochondrial degeneration
Expansion of infarct (hours to days)



4-12 hours: coagulative
necrosis and inflammatory
process
3-10 days: disintegration and
resorbtion of myofibrils and
fibrovascular response
Acute loss of myocardial cells
results in abnormal loading
conditions that involve not only
the border zone of the
infarction, but also remote
myocardium.
Scarring and Global remodelling
(7th week to months)


7th week: scarring complete
and remodelling continues for
months after the initial insult
Laplace’s law


Wall tension = Pressure x
radius / 2 x wall thickness
These abnormal loading
conditions induce
hypertrophy, then dilatation
and spherical shape change
of the ventricle
Typical patient presentation


CHF with multi-organ
dysfunction
Abnormal left ventricular
function







Abnormal septal function



Decreased contractility
Lvedd > 5.1 cm
LVesd > 4 cm
EF < 35%
LVPW < 0.9 cm
Aneurysm
IVSd < 0.9
Septal defect
Abnormal Right Ventricular
function
Goals and objectives for
revascularization in
ischemic cardiomyopathy
Revascularize anatomically graftable
vessels
 Reperfuse stunned or hibernating
myocardium that will recover
 Prevent progression of disease
 Balance high risk and mortality with a too
conservative approach passing over
patients who can benefit from surgery

Patient Selection
Criteria
Is the pathology operable?
Anatomical Indications


Veteran’s Affairs
Cooperative Study of
coronary bypass
surgery (VACS)
Coronary Artery
Surgery Study
(CASS)
Contractility assessment


Segmental analysis
3 descriptions of
myocardial movement

Hypokinesia


Akinesia


Functional segment, but
contractility decreased
Non-functional segment,
no contractility
Dyskinesia

Non-functional segment,
movement paradoxically
Hypokinetic or akinetic ischemic
myocardium

Stunned myocardium
 myocardial contractile dysfunction that follows a period of transient ischemia
(coronary occlusion), even after flow has been restored to an area that has no
irreversible damage
 represents a flow-contraction mismatch
 appear perfused on nuclear imaging exams, but will demonstrate wall motion
abnormalities
 may persist for a few days to 8 weeks after revascularization without further
intervention

Hibernating myocardium
 viable myocardium with depressed resting flow and reduced resting function
 Chronic decrease in blood supply (chronic ischemia)
 adaptive response to ischemia but with progressive cellular degeneration over
time

Scar Tissue
 Transmural
 Non-transmural
Chronic stable angina




Class 1
 Left mainstem > 50% stenosis
 Left main equivalent
 3 vessel disease with EF <50%
 2 vessel with proximal LAD with EF < 50% and objective ischemic changes
 1 or 2 vessel disease with large area of myocardium at risk
 Disabling angina despite optimal medical therapy when surgery can be
performed at low risk
Class 2a
 Proximal LAD without large area at risk
 1 or 2 vessel disease (not LAD) with moderate area at risk
Class 2b
 Borderline stenosis (50-60% other than LAD) with demonstrable ischemia
despite optimal medical therapy
Class 3
 Other than LAD with small area at risk
 Stenos 50-60% in other that left mainstem without ischemia
 Stenosis > 50%
SAME INDICATIONS FOR ASYMPTOMATIC CAD
Acute coronary syndrome

Non Q-wave

Acute < 12 hours


Sub-acute


Class 1 = Ongoing ischemia despite optimal medical therapy
Class 1 = Same as for chronic stable angina
Q-wave

Acute <12 hours



Class 1 = None
Class 2 = Ongoing ischemia, cardiogenic shock after failed thrombolysis / PCI
Sub-acute

Same as for chronic stable angina

Progressive failure with stenosis compromising viable myocardium outside
the initial infarct

Class 3
 CABG without attempts at maximal medical
therapy
Complications of PCI

Class 1




Class 2a



Foreign body in in crucial anatomical position
Hemodynamic compromise with coagulation impairment and
without previous sternotomy
Class 2b


Ongoing ischemia with significant myocardium at risk
Hemodynamic compromise
Rupture with impending tamponade
Hemodynamic compromise with coagulation impairment and
with previous sternotomy
Class 3

Stable with unsuitable anatomy
Trauma



Class 2a
 Demonstrable proximal
injury with demonstrable
ischemia
Class 2b
 No evidence of ischemia
 Distal injury with ischemia
Class 3
 Distal injury with no
ischemia
Kawasaki



Class 2a
 Demonstrable ischemia +
stenosis + viable
myocardium + graftable
arteries
Class 2b
 Asymptomatic giant
coronary artery aneurysms
subtending a large area at
risk (>8mm)
Class 3
 Small (<8 mm)
asymptomatic aneurysms
without stenosis
Physiological Indication

Determining myocardial viability

Wijns, Vatner, CamiciI (NEJM, Volume 339 nr 3)



Post-operative improvement in LVEF (also symptoms) is related to
the preoperative identification of viable myocardial tissue
Viability involving 18% or more of the LV myocardium have been
shown to have the greatest improvement in functional status
In a meta-analysis


Patients with predominantly viable myocardium who underwent
revascularization had an 80% lower mortality rate and a cardiac event
rate than those treated medically
No difference in cardiac death rate was seen in patients with
predominantly non-viable myocardium who underwent revascularization
versus medical therapy (7.7% versus 6.2%, respectively).
TECHNIQUES TO PREDICT FUNCTIONAL RECOVERY
AFTER REVASCULARIZATION IN PATIENTS WITH LEFT
VENTRICULAR DYSFUNCTION DUE TO CHRONIC
CORONARY ARTERY DISEASE
.
TECHNIQUE
SENSITIVITY
SPECIFICITY PATIENTS
STUDIES
Technetium 99m
Sestamibi Imaging
83 (78–87)
69 (63–74)
207
10
Dobutamine
echocardiography
84 (82–86)
81 (79–84)
448
16
Thallium-201 stress–
redistribution imaging
86 (83–89)
81 (79–84)
209
7
18F fluorodeoxyglucose
PET imaging
88 (84–91)
81 (79–84)
327
12
Thallium-201 rest
Redistribution imaging
90 (87–93)
81 (79–84)
145
8
Thallium Cardiac Imaging

Clinical Applications
 Detection
of coronary artery disease
Angiographically defined coronary artery disease
does not necessarily correlate with necropsy data
 Thallium imaging provides physiologic information
regarding the impact a specific stenosis has on
tissue perfusion

 Evaluation
of the extent and severity of
coronary stenosis
Technetium Labelled Cardiac
Imaging
Economics of Non-invasive Diagnostics
(END) study
 Compared
difference in cost in 11372 patients
referred for either stress MPI (myocardial
perfusion imaging) or cardiac catheterization
as initial approach
 Conclusions
Rates of subsequent infarction similar
 MPI much cheaper, less subsequent surgical
interventions

 Revision
of protocols to be expected
MR Imaging for Hibernating
Myocardium

Main application is hyper-enhancement studies
(demonstrates scar tissue) to predict functional recovery
 Gadolinium is retained by scar tissue
 Segments demonstrating 51-75% scar tissue = only
10% will demonstrate functional recovery with
revascularization
 Segments < 25% of the wall thickness = more likely to
recover function following revascularization
 Sensitivity
55% in predicting improvement in
function in a myocardial segment after revascularization
Patient Selection
Criteria
Is the patient operable?
Full multi-disciplinary work-up
 Risk factor identification
 Medical optimization

Patient Selection
Criteria
Will the patient benefit?
The bad news…..

Known increase in morbidity and mortality
following CABG with LV-dysfunction
 CABG
patch trail
 Should we revascularize occluded coronary arteries
in cardiovascular shock trail (SHOCK)

EF < 20% compared to normal EF
4
x increase risk for cardiogenic shock post surgery
 50% higher mortality
The good news…..




Veteran’s Affairs Cooperative Study of coronary
bypass surgery (VACS)
Coronary Artery Surgery Study (CASS)
Studies of Left Ventricular Dysfunction (SOLVD)
Findings
 Clear
survival benefit for patients with impaired LVfunction undergoing surgery versus optimal medical
management
 Decrease risk of sudden death
The evidence summarized….
Year
Number of
Studies
Patient Numbers
EF (%)
Main authors
19651975
6
386
<25%
Vlietsra, Manley, Yatteau,
Oldham, Zubaite, Faulkner
19751980
7
384
<20%
Fox, Jones, Alderman, Mochtar,
Zubiate, Hochberg, Sanchez
19801990
13
1819
<20%
Kron, Blakeman, Wong,
Christaki, Hammermeister,
Louie, Milano, Shapira,
Anderson, Hausman, Kaul,
Mickleborough,
19901995
9
1507
<35%
Langeberg, Elefteraides,
Kawachi, Moshkovitz,
Baumgartner, Cimochowski,
DeCarlo, Luciani
Peri-operative mortality
60
50
40
30
20
10
0
19651970
19701975
19751980
19801985
19851990
19901995
1995present
3-5 year mortality
60
50
40
30
20
10
0
19651970
19701975
19751980
19801985
19851990
19901995
1995present
Improvement in EF after
revascularization

40

35
30
25
Preoperative
20
Postoperative
15



10

5
es
De
Ca
rlo
Lu
ci
an
i
ra
id
pi
ra
fta
Sh
a
El
e
ila
no
0
M
5 studies
Average interval of 6
months
Increase in EF by 8 –
12%
60-70% of patients with
good result
P-value < 0.001 – 0.05
Improvement in regional
wall motion seen after 2
to 3 weeks
Timing of
revascularization

Daniel C. Lee (J Thorac Cardiovasc Surg 2003;125:11520)
 Performed a retrospective multicenter analysis
 32,099 patients who underwent coronary artery
bypass grafting as the sole procedure after
transmural myocardial infarction between 1991 and
1996
 179 surgeons at 33 hospitals in New York State.
 Overall hospital mortality for all patients was 3.3%.
 Hospital mortality decreased with increasing time
interval between revascularization and transmural
acute myocardial infarction
 Less than 6 hours = 14.2% mortality
 6-24 hours
= 13.8%
 24-72 hours
= 7.9%,
 4 – 7 days
= 3.8%,
 7 to 14 days
= 2.9%,
 After 15 days
= 2.7%
Conclusion
 In
the absence of absolute indications
for emergency surgical intervention,
such as structural complications and
ongoing ischemia
 3-day waiting period as a minimum
before surgical revascularization
should be considered
 Less than 3% mortality after 2 weeks
Additional challenges……..




REDO-CABG with CHF
CABG in concomitant ischemic mitral
regurgitation
CABG in concomitant post infarction VSD
CABG + Ventricular reconstruction
REDO-CABG with
CHF
Mortality rate 4.7 to 7.2%
 Careful planning essential

 Sternal
entry
 Aortic atherosclerosis
 Atherosclerotic vein grafts
 Diffuse native vessel disease
 Lack of conduits
 Myocardial protection
CABG in concomitant
ischemic mitral
regurgitation

Presence of MR increases operative
mortality for CABG alone by 3-12%

CABG + MR: > 10% operative
mortality
Overall recommendations

Severe MR (4+)



Moderate (3+)


CABG + Repair
Replace if intra-operative failure
CABG + Repair unless
 Additional operative morbidity / mortality would be
prohibitive
 OPCAB
Mild (2+)

Repair if
 Morbidity / mortality low
 Investigations show periods of more severe MR
 Confirmation during intra-operative TEE



CABG alone
 Balu, Christenson, Tolis
 Can decrease MR severity (especially mild with poor LVF)
 Weak impact on moderate MR leaving many patients with 2+ or
greater RMR
 Emory group
 Moderate RMR no effect on long term functional status or
survival
CABG + mitral surgery
 Prifti, Harris
 CABG + MV-repair improve late outcome (especially LVF)
Residual MR after CABG/Repair
 Oppell, Czer
 65% 3 year survival
 Suture annuloplasty: Failure to decrease MR-severity in 33% of
patients
 Ring/band annuloplasty: 2+ grade decrease in 97% of patients
CABG in concomitant
post infarction VSD



Alvarez, Dagget, Deville
 CABG may increase early and longterm survival
 Recommendation
 If stable enough => Catheterization + CABG
 If not => selective left heart catheterization and
proceed with septal repair
Value of pre-operative angiogram and revascularization
is controversial
 No additional benefit
 Time-consuming
 Dangerous
Possible role of CT-Angiography?
CABG + Ventricular
reconstruction

Cleveland
 85%
concomitant CABG and 43% concomitant MVR
in reconstruction procedures
 Survival at 30 days, 1,2 and 3 years was 98%, 92%,
90%, and 86%

Goal
 Incision
into anterior wall scar tissue (LAD
distribution) to exclude pathological segment and to
reduce LV-cavity size

Indications
 Dyskinetic
segment
 Electrophysiologically proven source of arryhtmia
 Thrombus
What about therapeutic
angiogenesis and laser
revascularization?
Stimulate
angiogenesis through
inflammation induction
Limited roll at present
Conclusion



CABG remains the definitive management for
ischemic cardiomyopathy in conjunction with
optimal medical management
Although these patients are at higher risk,
outcome have improved and is now acceptable
 Clear survival benefit
 Clear improvement in quality of live
Myocardial viability assessment forms the
cornerstone of surgical decision making and
new studies challenge current protocols which
require revision
Summary……
Minimum criteria for CABG in ischemic CMO
 Anatomically
graftable vessels and standard CABG
indications
 Viability involving 18% or more of the LV myocardium
irrespective of EF
 Operable patient
If not ======> Palliative and transplant
consideration
Thank you