STRESS ECHOCARDIOGRAPHY AND MYOCARDIAL VIABILITY

TAHEREH DAVARPASAND, MD

FELLOWSHIP OF ECHOCARTDIOGRAPHY

TEHRAN NIVERSITY OF MEDICAL SCIENCE

TEHRAN HEART CENTER

INTRODUCTION

• LVD remains one of the best prognostic determinants of survival in patients with CAD .

• Viability testing can help direct patients whom will benefit the most from

revascularization.

• SPCT, Dobutamine stress echo, CMR, and PET imagining with FDG are the most

common modalities for assessing myocardial viability.

• Stress echocardiography (SEC) was initially developed in 1979 for evaluation of patients

with known or suspected coronary

• Dobutamine stress echocardiography (DSE) is the most commonly used agent : higher

sensitivity and relatively controllable side effects

• DSE has higher specificity (mean 79% vs 59%) but lower sensitivity (mean 82% vs 86%)

in detection of viable myocardium compared to tl rest-redistribution imaging.

• A risk of serious complications being negligible in experienced centers.

• Patients with chronotropic incompetence may not have an adequate chronotropic response to DSE

and therefore the test may be non-interpretable.

• Patients with pacemakers may have inadequate rate response, and also these patients may exhibit

regional wall abnormalities owing to pacing effect, and therefore the test may be difficult to

analyze

• Most commonly encountered side effects with DSE are warm feeling, flush,

palpitations related to tachycardia, and in some cases, a mild headache.

• In rare instances, patients may have a residual sensitivity to bright light for an hour or so

following test.

Contraindications to DSE :

• ventricular arrhythmias, recent myocardial infarction (within 3 days), unstable angina,

significant left ventricular outflow obstruction, aortic dissection, and severe (resting

systolic blood pressure >180 mmhg or diastolic blood pressure >100 mmhg) or

symptomatic hypertension.

PATHOPHYSIOLOGY AND MECHANISM

• Viable myocardium

• Myocardial stunning: a reversible state of regional contractile dysfunction that occurs

after transient ischemia without ensuing necrosis.

• Myocardial hibernation: persistent left ventricular dysfunction that results from

chronically reduced blood flow or repetitive stunning without infarction and necrosis : a

protective mechanism

• Nonviable myocardium : if myocardial perfusion is not restored, irreversible myocardial

necrosis can occur.

• A resting akinesis which becomes dyskinesis during stress usually reflects a passive

mechanical consequence of increased intraventricular pressure during SEC

• In the viability response:

1) sustained improvement during stress, indicating a non-jeopardized myocardium

(stunned)

2) non-sustained improvement, indicating a jeopardized region (hibernating myocardium)

related to active viable segment that may improve after revascularization

• ASE guidelines recommend that viability assessment at a minimum includes

improvement in at least two echocardiographic left ventricular segments.

• The presence of myocardial viability early after a myocardial infarction is the single best predictor of

recurrent in-hospital ischemia and unstable angina after discharge. (20% VS 7%)

• Presence of viable myocardium is associated with better left ventricular function recovery and lower

long-term mortality.

• DSE is helpful in identifying patients most likely to have improved survival by undergoing percutaneous

revascularization or coronary artery bypass grafting.

• For patients with stable CAD, the biphasic response on DSE is useful in predicting ultimate post-

revascularization left ventricular recovery.

• The biphasic response is 60% sensitive and 88% specific in assessing recovery of contractile function 6

weeks after coronary angioplasty.

• LV wall thinning and increased echo backscatter are thought to be markers for scarring.

• An LV end-diastolic wall thickness (EDWT) of <6 mm was initially reported to practically

exclude relevant amount of viable myocardium.

• Shah et al, who showed that about one-fifth of segments with regional wall thinning caused

by ischemic heart disease without evidence of LGE demonstrate LV function improvement

after revascularization with reversal of wall thinning.

• In patients with LV end-systolic volume >130 ml, a marker for extensive LV remodeling,

cardiac events were 38% higher after 3 years after revascularization, despite metabolic

evidence of “viable” myocardium.

• Tissue Doppler imaging and speckle tracking echocardiography to assess myocardial

deformation have demonstrated promising roles in the evaluation of viable myocardium.

• Speckle tracking echocardiography is more sensitive in detecting viability in ischemic

cardiomyopathy because mechanical changes involving the sub-endocardium may be

more readily identified compared with qualitative visual assessment.

• Speckle tracking echocardiography with its ability to perform layer-specific analysis has

been shown to predict LV functional recovery and remodeling after acute MI.

GOALS OF VIABILITY STUDIES

• VIABILITY TESTING CAN PREDICT IMPROVEMENT OF HEART FAILURE

SYMPTOMS AND EXERCISE CAPACITY AFTER REVASCULARIZATION.

• STICH and PARR-2 represent the most significant efforts to date to address the roles of

SPECT and dobutamine echocardiography and of PET, respectively, in the management

of patients with CAD and LV dysfunction.

• However, neither study could model all the key factors involved that determine patient

survival.

• Their results reflect the complexities in decision-making for patients with severe CAD

and LV dysfunction being considered for surgical coronary revascularization.

• The 10-year results of the multicenter randomized STICH trial (surgical treatment for ischemic heart

failure) demonstrated improved long-term all-cause and cardiovascular mortality with surgical

revascularization of patients with ischemic cardiomyopathy (LVEF ≤35%) compared with patients

receiving guideline-directed medical therapy (GDMT). however, this late survival benefit was achieved

at the expense of higher short-term 30-day mortality after CABG, which highlights the importance of

appropriate patient selection for CABG.

• In the PARR-2 trial, patients randomized to PET viability imaging did not demonstrate improved survival

after CABG compared with standard care.

• In the meta-analysis of Orlandini et al, PET assessment of viable myocardium was not superior to

SPECT or dobutamine echocardiography in predicting survival after revascularization in patients with LV

dysfunction.

• Patients who met the ICD criteria of EF ≤35% at 3 months after myocardial infarction

had lower EF, MAPSE and PSV on baseline and stress echocardiograph before

discharge.

• Stress echocardiography did not add additional value in predicting non-recovery.

• For MAPSE, an average of the longitudinal excursions of the anterolateral and

inferoseptal walls (from the apical four-chamber view), and the inferior and anterior walls

(from the apical two-chamber view) was used.

• For PSV, an average was calculated using all six basal segments visualized in the three

apical views.

TAKE HOME MESSAGE

• The physiological complexity underpinning the potential therapeutic benefit of surgical

revascularization cannot be surmised from the results of a single test of myocardial viability,

particularly when those results are expressed in a dichotomous fashion (i.E., Patients having

or not having viability).

• Stich trial showed that the degree of left ventricular systolic dysfunction and remodeling and

the number of stenotic coronary arteries appear to be stronger determinants of the benefit of

revascularization than myocardial viability.

• The results of tests for detection of viable myocardium must be interpreted within the context

of the multiplicity of factors necessary to reach the best treatment decision for each patient.