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INVESTIGATING STABLE IHD TREADMILL, DOBUTAMINE STRESS ECHO OR STRESS THALLIUM??Dr Robin PintoHoly Family Hospital, Glenmark Cardiac Centre
FACTORS DECIDING CHOICEAbility to exerciseBaseline ECG abnormalitiesPrior CABGS / PTCA / MIPortabilityCostRadiationPhysician PreferenceSensitivity And Specificity
PROBABILITY OF CAD
VERIFICATION BIASDescribes the impact of reporting sensitivity and specificity when calculated primarily using patients with positive stress test results
Sensitivity = TP / TP + FN
Specificity = TN / TN + FP
VERIFICATION BIAS
ROLE OF ETT AS A DIAGNOSTIC TESTTEST OF CHOICE IN THOSE WITH
WITH INTERMEDIATE TEST PROBABILITY NORMAL BASLINE ECG ABLE TO EXERCISENO PRIOR REVASCULARISATION
INCREASING SENSITIVITY OF ETTEXISTING: ST deviation and slopeST / HR slope > 2.4 V / bpmST / HR index > 1.6 V / bpm
NEW:ST / HR Hysteresis integrates difference in ST segment depression between exercise and 3 min of recovery . Chronotropic incompetence
DST - ADVANTAGESTotally non invasive, safe , repeatable
No radiation
Relatively short procedure time
Simple instrumentation, portable
Can identify other structural abnormalities
Disadvantages of DSTImages difficult to acquire because of marked cardiac excursion
RWMA may be transient
Highly operator dependent
Inability to image all segments in 15%
Detection of residual ischemia in infarct zone difficult
WHATS NEW IN DST
Use of LV opacification
MCI - microvascular perfusion, viability, improving sensitivity of DST
Use of Speckle tracking / Strain imaging
32 yr/ M, IGT, Non smoker, Atypical chest painIntermediate pretest probability
49 yr old marathon runner, CT Calcium Score = 1095.03
Microvascular re-perfusion Acute MI
No microvascular reflow
MPI Myocardial Perfusion ImagingCan evaluate Ventricular function
Most sensitive for diagnosis of CAD
Identifies region of ischemia
Can assess myocardial viability
DISADV OF MPI
Attenuation artifacts
In severe disease, balanced ischemia can lead to a false negative test
PROGNOSTIC INDICATORS FROM ETTDuration of exercise < 6 METSFailure to increase syst BP > 120 mm Hg, sustained decrease > 10 mm hg below restST depression > 2.0 mmsExercise induced ST elevationAngina at low workloadsSustained (> 30 secs) / symptomatic VT
NEWER PROGNOSTIC INDICATORS FROM ETTMORTALITYFunctional Capacity (METS, DTS)Heart Rate Recovery - < 12 bpm in first min Chronotropic Incompetence < 80% THR
SUDDEN CARDIAC DEATH (SCD)TWA (T-wave alternans) > 65 V is high riskFrequent PVCs in recovery > 7 / min
ADVERSE PROGNOSTIC MARKERS IN DST & MPI
Amt of myocardium - > 3 segments in DST, > 10% myocardium in jeopardy
More than one territory
LV dysfunction LV dilatation on DST, Fall in EF by > 5%, Global EF < 45% , Transient ischemic dilatation ratio > 1.2, Lung uptake, RV uptake / dilatation
CONCLUSIONPerforming these tests routinely in the general population is probably not indicated
ETT Test of choice for the majority of patients with a baseline normal ECG and the ability to walk on the treadmill
DST / MPI Those with a non diagnostic ETT and intermediate test probability.
CONCLUSIONDST Increasing use, especially useful in those with LBBB / bronchoconstriction
MPI especially to assess residual ischemia in infarct territory, assess viability, post CABGS, assess significance of non critical lesions
Prognostic information gleaned from each of these tests extremely important in making clinical decisions
LAD lesion
70 yr /F LAD/RCA CT calcified, Calcium score = 1175
60 yr old man police officerEx smokerHypercholesterolemiaHigh stress job in Anti-terrorist squadChest discomfort during morning exercise
(high pre-test probability)
ISCHEMIC CASCADE
Comparative Definition of Moderate-Severe IschemiaLeslee J. Shaw,J Am Coll Cardiol Img 2014;7:593604
Cardiac death / MI 4-6 % per year
ETT Dukes Treadmill score < -10
Stress Echo > = 3 /16 new akinetic segment
Nuclear stress > 10% Ischemic myocardium
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MYOCARDIAL VIABILITYWith Thallium Redistribution. If no redistribution at 4 hrs further injection and delayed imaging even at 24 hours
Using Technetium 99m Labeled agents - > 50% of maximal tracer activity in a dysfunctional segment
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