Myocardial Viability

Assessment by Dobutamine

Stress Echocardiography

Dr.Arezou Zoroufian

Associate Professor of TUMS-THC

Viability Studies by Low Dose DSE

• Dobutamine echocardiography is an established method for

detecting viable myocardium in patients with CAD and LV

dysfunction with very good sensitivity and specificity for

predicting wall motion improvement after coronary

revascularization.

post-ischemic but viable

myocardium requires hours to

days before function is fully

restored

WMA

Acute Myocardial ischemia

This slow return of cardiac

function after resolution of

ischemia has been called

Stunning :“prolonged, post-

ischemic dysfunction of viable

tissue salvaged by reperfusion.

Hibernation if salvage is not

spontaneously.

Definition of Viability

• ASE GUIDLINE:

Improvement of wall motion abnormality at

lest one grade in 2 or more segments during

stress test

Case#1

• 66 years old man

• Hx of inferior and posterior wall MI

• Q wave in II-III-avf

• Three vessel disease in CAG , Cut RCA from proximal artery

• LVEF~30% by 3D study

• Moderate functional MR

Low Dose Dobutamine Stress

Echocardiography

• A standard dobutamine-atropine stress protocol was per-formed with

low-dose images at 5 and 10g/kg/min.

• Blood pressure and 12-lead electrocardiography were recorded at baseline

and at the end of every stage

Tardokinesia, delayed sometimes post systolic thickening

or inward motion

WMA Categorization

Response of Dysfunctional Myocardium to

Dobutamine

Biphasic response

Worsening of function

Sustained response

No change

Stunning or Hibernation ?

Spontaneouslyrecoverable (Stunned ) : dysfunction despite normalization of coronary perfusion , typically early after acute ischemic events, resolves spontaneously a short duration of coronary flow limitation , recovery may be delayed for days up to months

with revascularization ( Hibernating) , late after the event, chronic reduction of flow, resumption of normal function related to myocardial revascularization, recurrent ischemia and stunning makes hibernation

Both stunned & hibernating myocardium are responsive to dobutamine

Stunning and Hibernation frequently coexist and contribute to CHF

sub endocardial subepicardial rest Db response flow recovery

structure structure function low dose of function

Normal Normal HK +++ 100% ++

Hibernating Hibernating HK ++ 50% ++

<20%MI Normal HK ++ >80% ++

<20%MI Hibernating HK ++ =50% ++

>20%MI Normal AK + <80% +

>20%MI Hibernating AK +/- =30% +/-

50%MI N/Hibernating AK -/+ <50% +/-

MI MI AK No 0% No

Viable Myocardium

• Wall thickness >0.6cm had a sensitivity of 94% & specificity of 48%

for recovery of function

• In addition to prediction of regional functional recovery, DSE can predict

global function recovery , means good prognosis

• DSE is less sensitive for predicting of recovery of thinned walls (53%) by

conventional method

Tips & Tricks

Tethering effects , subjective visual assessment, relationship of prognosis to the number of viable segments, improvement of function in two adjacent segments is more reliable sign of significant viability

Partially viable segments with resting hypokinesisexhibit no change of function with low dose dobutamine have severely reduced perfusion reserve, severe multivesselCAD, poor collateral supply, and increased cardiac mortality

False-negativeexams may occur in hibernating regions that cannot respond to dobutamine

accuracy of interpretation of stress echocardiography is improved by visualization of more than a single cardiac cycle in each view particularly true in respiratory artifact, arrhythmia, and translational motion of the heart

Tissue Doppler imaging

• Need for a quantitative approach to study the regional changes in

deformation and their timing induced by ischemia performed Tissue

Doppler imaging , Strain and Strain rate imaging as a sensitive quantitative

methods for assessing myocardial function and have been shown to

overcome the limitations of current ultrasound methods in assessing the

complex changes in regional myocardial function

• 3D speckle tracking the last success in myocardial velocity assessment

Quantitative Methods for Assessment of

Viability

• Doppler assessment of tissue velocities and displacement

• An increase in displacement >5 mm and 5% increase in EF predict improvement of global function with revascularization

• A high mean Sm value in the basal segments is associated with lower mortality rate

Quantitative Methods for Assessment of

Viability

• Strain & Strain rate study are measures of tissue deformation (Tissue Doppler-based )

• A cut off value ~ 11.5% & Post systolic shortening is a marker of viable myocardium

• SR<0.53 is a cutoff value for nonviable myocardium

• Ability of contraction in adjacent segments influence the velocity in any given segment limits the site-specificity of velocity data

Quantitative Methods for Assessment of

Viability

• Speckle Tracking echocardiography avoids some of the issues relating to

angle dependency

For differentiating viable from

nonviable minimal (<12%) with

sensitivities ranging from 0.68 to 0.85

& specificities ranged from 0.83 to

0.96

Quantitative Methods for Assessment of

Viability

Quantitative Methods for Assessment of

Viability

• RT 3dimensional echocardiography . Although a good acoustic window is still required to obtain high-quality studies, this technique enables reformatting of the3-dimensional data set in any imaging plane , avoids geometric assumptions , allows off-axis images , has excellent correlation with CMR in LVEF assessment, permits simultaneous viewing of standard parasternal long, parasternal short and apical volumetric data, allowing a more detailed wall motion analysis .

Prognostic Value of DSE in Viability Studies

• High sensitivity (86-90%) & Specificity ( 81%)

• Using a cutoff >=4 of 16 segments with a biphasic response & Contractile

reserve shows viable ventricle ( predicts a 5% improvement in EF ) and

improved outcomes after revascularization

• Absence of viability is associated with no significant difference in outcomes,

irrespective of treatment strategy and there is a trend toward higher mortality

with revascularization.

Case#2

• 70 Yrs old man

• Prominent symptom is dyspnea (FC#II)

• Diabetic

• 3 VD in CAG

• HF in echocardiography + significant WMA in anterior & posterior

circulatios

Prognostic Value of DSE in Viability Studies

The presence of viability identifies patients in whom

revascularization is associated with a

significant survival advantage

Absence of viability is associated with no

significant outcome advantage, whether medical or surgical

therapy

Patients with dysfunctional but viable

myocardium who are treated medically are at

increased risk of cardiac events and

revascularization improves survival