Journal ClubJournal Club

William M. Herndon,Jr MD FACC FASEWilliam M. Herndon,Jr MD FACC FASE

January 27, 2005 January 27, 2005

Historical perspectives:Historical perspectives:

Reversible Tl-201 defects pre CABG in Reversible Tl-201 defects pre CABG in CHF patients CHF patients without angina without angina led to led to improved LVEF post CABGimproved LVEF post CABG

BUT: 45% of “fixed” Tl-201 defects pre BUT: 45% of “fixed” Tl-201 defects pre CABG showed improvement post CABG CABG showed improvement post CABG with increased LVEF from 15% to 27%with increased LVEF from 15% to 27%

Atkins. Am. J. Cardiol. 1980;46:695Atkins. Am. J. Cardiol. 1980;46:695

Historical PerspectivesHistorical Perspectives

Tl-201 Stress-Rest -Reinjection protocols Tl-201 Stress-Rest -Reinjection protocols ““rest only” protocolsrest only” protocols Nitrate administration protocolsNitrate administration protocols

All demonstrated ability to detect viability All demonstrated ability to detect viability (with similar shortcomings) (with similar shortcomings)

Imaging AgentsImaging Agents

Tl-201: Exhibits “redistribution”Tl-201: Exhibits “redistribution” Tc-99m:Tc-99m:

Sestamibi (Cardiolite)Sestamibi (Cardiolite)

Tetrofosmin (Myoview)Tetrofosmin (Myoview)

F-18 FDGF-18 FDG

Matsunari. J Nuc Med 36:1961,1995

Viability AssessmentViability Assessment

Dobutamine echo has higher Dobutamine echo has higher positive predictive positive predictive valuevalue for for functionalfunctional recovery recovery

BUT: Resting wall thickening BUT: Resting wall thickening ceasesceases by echo with by echo with subendocardial infarct of >20% LV thicknesssubendocardial infarct of >20% LV thickness

Perfusion imaging evaluates activity in entire LV Perfusion imaging evaluates activity in entire LV thickness and reflects a continuum of values, some thickness and reflects a continuum of values, some below threshold for below threshold for functionalfunctional recovery recovery

Revascularization below the level of functional Revascularization below the level of functional recovery likely to show benefit from prognostic recovery likely to show benefit from prognostic standpoint. standpoint. Di Carli J Nuc Cardiol 2002;9:229Di Carli J Nuc Cardiol 2002;9:229

Comparison of Techniques:Comparison of Techniques:

Meta-analysis showed higher sensitivity for perfusion imaging,higher specificity for Dobutamine echo, and slightly higheroverall accuracy for PET in predicting improvement in regional dysfunction after revascularization.

Bax. JACC 1997;30:1451

Measures of viabilityMeasures of viability

Recovery of regional functionRecovery of regional function Recovery of global functionRecovery of global function Reverse remodelingReverse remodeling Reduction of MR, TR, pulmonary hypertensionReduction of MR, TR, pulmonary hypertension Restitution of perfusionRestitution of perfusion Recovery of cardiac reserveRecovery of cardiac reserve Reduction of symptomsReduction of symptoms Improved survivalImproved survival

Viability Assessment:Viability Assessment:RemodelingRemodeling

What is most important: detection of What is most important: detection of

hibernating endocardium, hibernating hibernating endocardium, hibernating

epicardium, or scar?epicardium, or scar?

Is recovery of function the “gold standard”?Is recovery of function the “gold standard”? EpicardialEpicardial viability may prevent LV viability may prevent LV

remodeling and arrhythmogenesis...remodeling and arrhythmogenesis...

Senior. Journal Nuc Cardiol 9;2002:454

Senior. Jour Nuc Cardiol 9;2002:454

Mortality Reduction:Mortality Reduction:

Meta-analysis of outcomes showed no differences in techniques re: mortality reduction or unfavorable cardiac events afterrevascularization.

Allman. JACC 2002;39:1151

Transmural Hibernation Transmural ScarTransmural Hibernation Transmural Scar

Tracer uptake is a continuous marker of how much viability is present in a dysfunctional area.

Thresholds of uptake are markers of a sufficient mass of myocardium to support regional function after restoration of flow

QUANTITATION:

With “Intermediate” values on With “Intermediate” values on quantitationquantitation

(such as after NQMI)(such as after NQMI)Consider Stress-Rest Imaging:

Reversible defects are more powerful predictors of functional recovery than rest-only defects

Emerging ModalitiesEmerging Modalities

MRI: -Will likely become the “gold standard” for MRI: -Will likely become the “gold standard” for viability where availableviability where available

-Assesses myocardial fibrosis -Assesses myocardial fibrosis - Unparalleled tissue characterization- Unparalleled tissue characterization

Metabolic Imaging: ? ACEMetabolic Imaging: ? ACE

Caveats:Caveats:

Severe LV dysfunction (less than 25% Severe LV dysfunction (less than 25% LVEF)LVEF)

Concomitant valvular heart disease or PHTConcomitant valvular heart disease or PHT Local expertise and experience may dictate Local expertise and experience may dictate

best diagnostic approachbest diagnostic approach