Utility of Contrast Echocardiography in Acute Myocardial Infarction - SD

Introduction

I am Dr. Michael Main.
I am medical director
of the Echocardiography Laboratory at St.
Luke's MidAmerica Heart Institute in Kansas City.
And I'll be speaking today on the utility
of echocardiography,
specifically contrast echocardiography in the diagnosis
and management of acute myocardial infarction.
I'll be talking today, as I said, on the utility of
contrast echocardiography in acute myocardial infarction.

Relationship Between Left Ventricular Ejection Fraction and Mortality

This slide shows something that most
of you are probably aware of,
and that's the relationship
between left ventricular ejection fraction
and six month mortality following myocardial infarction.
This is data from the GC study published in circulation in
1993,
and as you can see when left ventricular systolic function
is relatively well preserved
with an ejection fraction greater than 40
or 50%, intermediate term mortality is rather modest.
However, as left ventricular ejection fraction drops into
the range of 30% mortality skyrockets.
Of course, this demonstrates the importance of
accurate and reproducible left ventricular ejection
fraction calculations in all patients
with myocardial infarctions.

Guidelines for LVEF Measurement

Shown here is a Class one indication
from the A-C-C-A-H-A guidelines for the management
of patients with ST segment elevation myocardial infarction
indicating that LVEF should be measured in all
ST elevation myocardial infarction patients.
The guidelines go on to say that
echocardiography is the preferred technique for assessment
of LV function in all patients,
not undergoing LV angiography, especially if the patient is,
hemodynamically unstable.

Appropriateness Criteria and Evaluation of Complications

The appropriateness criteria were recently published
for echocardiography,
and it's important to note that for the initial evaluation
of LV function following acute MI
and for reevaluation of LV function following MI
during the recuperative phase for both of these indications,
an appropriateness score of nine
and eight,
were assigned respectively indicating a very high level of,
of appropriateness for these indications.
Additionally, echocardiography is appropriate in the
evaluation of suspected complications
of myocardial infarction, including things such
as acute myocardi, acute mitral regurgitation,
ventricular septal defect, free wall rupture,
and right ventricular involvement.

Importance of Left Ventricular Volumes

As we know, left ventricular ejection fraction is
important, but there is more to it than that.
Left ventricular volumes are also critically important.
This data is from a seminal study published
by Harvey Wide in circulation in 1987 indicating
that left ventricular
and systolic volume is actually a better marker than
ejection fraction for the prediction of survival,
both in patients with relatively well preserved ejection
fraction, and in those with reduced LV systolic function.

Accuracy and Reproducibility of Echocardiography with Contrast

How well do we do with echocardiography?
In the absence of contrast, mom
and colleagues performed a study published in the Journal
of the American Cardiio Journal of the American College
of Cardiology entitled Accurate
and Reproducible Measurement, left Ventricular Volume
and ejection Fraction By Contrast,
echocardiography asking the question,
does contrast echo improve accuracy
and reproducibility of volume
and ejection fraction measurements in unselected patients
presenting to the cardiology department?
And in this study, 110 consecutive patients underwent both
cardiac MRI, which served as the gold standard technique
as well as echocardiography with tissue harmonic imaging
and a subsequent echocardiographic examination
with contrast.

What they found was quite interesting.
I'll draw your attention to the end diastolic volumes First,
looking at the reference standard cardiac MRI, in this case,
MRI defined a mean end diastolic volume
of 177 mls.
Non-contrast echocardiography significantly
underestimated these volumes.
The mean volume was 126.
However, with the addition of contrast, this disagreement
between echocardiography
and cardiac MRI was largely erased
with a mean diastolic volume with contrast echo of 152
MLS shown in another fashion.
Here is the mean difference
and limits of agreement between echocardiography
and MRI for both non-contrast echo on the left
and contrast echo on the right.
And as you can see, the mean difference
and the limits of agreement between the two tests,
have significantly narrowed.

Why might this be even in patients
who have good left ventricular
endocardial border definition?
This is a patient who certainly has fairly crisp endocardial
border definition, but over the anterolateral wall,
it's difficult to know exactly
where the endocardial border lies.
Is it here, here or perhaps even here?
We have difficulty determining
where the papillary muscle structure begins and ends
and exactly where the endocardial
border, should be traced.
With the addition of contrast in the same patient,
we now can see that this all is papillary muscle structure
and subvalvular structure
and the endocardial border is now crisply defined,
enabling us to accurately
and reproducibly trace the left ventricular border enabling
both volume and ejection fraction assessment.

Guidelines on Viability Assessment and No Reflow Phenomenon

The A-C-C-H-A guidelines for the management
of patients with ST elevation myocardial infarction go on
to state that either dobutamine echocardiography
or myocardial perfusion imaging is reasonable
in stable patients four or more days
after MI to assess myocardial viability.
And one thing that we're able to do with echocardiography,
specifically myocardial contrast echocardiography,
is assess no reflow what is no reflow?
It's extensive micro circulatory damage which can occur
despite patency of the infarct related artery.
It's associated with lack of functional recovery
and it's independent of epicardial flow rates.
In other words, a patient may have brisk flow
through the infarct related artery following primary
intervention, but still have extensive micro
circulatory damage.

Case Example: Recovery of Function

This is a case of a 75-year-old woman who presented
with an s st segment elevation.
Myocardial infarction underwent successful primary
angioplasty with a peak C-P-K-M-B of 82,
and this is her initial per parasternal long axis image
showing extensive a kinesis,
over the an septal region of the heart.
The question obviously arises is this due to stunning,
prolonged post ischemic LV dysfunction without necrosis
or is it due to cell death?
And this is a myocardial perfusion echocardio
echocardiogram using a low MI technique.
And as we can see, there is very dense homogeneous
myocardial perfusion throughout the zone
of Kinesis indicating that the capillary network is intact.
And as we see greater than one month later,
this patient has recovered LV systolic function.
We can compare this parasternal long axis image which
initially showed a kinesis of the antra septal region,
which is now contracting quite normally.

Case Example: No Reflow Phenomenon

A second case, an 85-year-old woman presented
with stuttering chest pain pattern over several days,
no prolonged episodes of discomfort.
She underwent successful primary angioplasty
and her peak CKMB was only 46 indicative.
It was thought of a small myocardial infarction.
And this is her baseline apical four chamber view.
And as we can see, there's a, an extensive zone
of a kinesis throughout the LAD distribution.
The RV is hyperdynamic.
She also has some left atrial dilatation consistent,
with her age.
This is the myocardial contrast echocardiogram in this
woman, an apical three chamber view.
And as we can see, the infra lateral wall is contracting
quite vigorously and is also well perfused the ant septum.
However, while we do see profusion at the base,
the remainder of the inter septum has a dense
defect consistent with the no reflow phenomenon.
And this is this patient's follow-up echocardiogram showing
no recovery of function late
after infarction as predicted
by the myocardial contrast echocardiogram.
Again, a large zone of a kinesis persistent,
months following the infarction.

Predictive Value of Myocardial Contrast Echocardiography

What we know is that we can use this
profusion score index.
We can calculate a profusion score index
to predict global recovery of LV systolic function
after anterior mi.
In fact, the profusion score index immediately following
infarction more closely mirrors
the wall motion score index,
late
after infarction than does initial assessment
of LV systolic function.
We also know that the number
of abnormally perfused myocardial segments predict the
likelihood of myocardial remodeling.
And this is from a study we performed showing
that when greater than five myocardial segments are
abnormally perfused after infarction, extensive remodeling.
In other words, dilatation
and distortion of left ventricular shape always occurs.
Myocardial contrast echo is also useful in predicting
recovery or predicting rather event-free survival in
these same patients.
And this figure, this Kaplan-Meier survival curve is from a
large study of patients with significant LV dysfunction post
mi, all of whom underwent myocardial contrast echo when
profusion pattern was normal event-free survival,
consisting of either death or incident.
Heart failure,
was very high,
95% event-free survival when the myocardial perfusion
pattern was abnormal.
However, there was a 20% event rate over about five
years of follow up.

Guidelines on Complications and Role of Contrast

Finally, the combined society guidelines
for the management of patients with STEMI also indicate
that echocardiography ought to be used in patients
to evaluate suspected complications including
infarct expansion, ventricular septal rupture,
and intracardiac thrombus.
The guidelines go on to say
that echocardiographic contrast agents may improve diagnosis
in free wall rupture
and in identifying intracardiac thrombus.

Case Example: Thrombus Detection

And this is a patient, a 40-year-old woman
with a recent anterior wall myocardial infarction,
which she unfortunately suffered
during recovery in the hospital from a bilateral
mastectomy for breast cancer.
The question obviously arises is,
is there a thrombus at the cardiac apex?
Difficult to tell on the baseline image.
However, following an injection
of an ultrasound contrast agent, we're able to see quite,
quite clearly that there is no thrombus
at the ventricular apex.
And we're also able now to calculate left ventricular
volumes and ejection fraction.
And this information was subsequently used
to qualify this woman for an ICD.

Case Example: Post-Infarct Angina and Ventricular Septal Defect

This is a case an 85-year-old woman
who presented several days after MI with post infarct angina
and minimally elevated cardiac biomarkers.
As you can see by this left ventricular gram,
she had severe left ventricular dysfunction
and a squared off cardiac apex
with a large LV apical mural thrombus.
She also underwent a contrast echocardiogram,
which certainly confirmed presence of the thrombus,
but also demonstrated a transmural myocardial perfusion
defect at the apex.
And as we know, no reflow, lack
of myocardial perfusion in the zone of kinesis is predictive
of cardiac complications.
In this case. This woman subsequently developed a post MI
of ventricular septal defect several days later
through this zone of no reflow
or necrotic, myocardium.

Case Example: Left Ventricular Pseudoaneurysm

This is a patient, an elderly man
with known coronary artery disease
and presumed previous myocardial infarction
who we were asked to evaluate.
And as you can see, there's a zone of a kinesis at the apex
and there's also a clear space,
out here as well.
Difficult to know exactly what that is, especially
on these baseline images without contrast.
Following contrast infusion, we see two
and fro flow of contrast material into this cavity,
of course consistent with the diagnosis of contained rupture
of the myocardium or left ventricular pseudo aneurysm.

Statistics on Pseudoaneurysm and Benefits of Contrast

But what do we know about pseudo aneurysm?
There are about 500,000 ST elevations per year,
ST elevation myocardial infarctions per year in the us.
One to 6% of these go on to have an LV rupture.
This can result either in immediate death
or pseudo aneurysm formation, which is associated
with a high death risk.
And of course, the treatment is immediate surgery.
Echo without contrast is only 26% sensitive to detect
pseudo aneurysm.
However, infusion of contrast is diagnostic.
If we see appearance of microbubbles
outside the LV cavity within the pericardial space,
we can make this diagnosis without actually having
to visualize the discrete rent in the myocardium at
the site of rupture.
If we think about this, if only 1% of patients
with ST elevation infarction develop a pseudo aneurysm
that would be 5,000 patients per year in the United States,
and the use of contrast on a routine basis could potentially
save 3,750 lives per year.
While putting this in perspective, especially in light
of the safety considerations associated
with contrast agents over the past several years,
there were four deaths reported in association
with affinity over a six year period.
Of course, these deaths were temporarily associated
but not necessarily causally attributable
to the contrast agent.
None of those patients actually had an acute
myocardial infarction.
Therefore, a contrast contraindication
or failure to use
contrast in acute myocardial infarction could potentially
lead to the loss of several thousands of lives, tens
of thousands of lives, in fact,
over a several year period just from failure
to diagnose left ventricular pseudo aneurysm alone.
And of course, that's the potential mortality resulting from
failure to use contrast in just one disease state.