Stress Testing :Stress Testing :Which Test to Choose?Which Test to Choose?

Gary J. Balady, MD

Professor of Medicine

Boston University School of Medicine

Stress Testing at Stress Testing at Boston Medical CenterBoston Medical Center

• Exercise ECG ( treadmill test)• Exercise – Echo• Exercise – Nuclear• Cardiopulmonary ( Metabolic ) • Dobutamine –Echo• Pharmacologic (regadenoson) nuclear

– SPECT– PET

• SCM Order Set: stress test selector

supply demand

supply demand

coronary arteries• atherosclerosis• coronary vasospasm• hypoxemia• anemia• hypotension• coronary anomalies• coronary vasculitis

factors• HR x BP• contractility• wall stress

Supply

• Degree of obstruction• Length of lesion• Dynamic properties of lesion

•Dynamic properties of distal vascular bed

• thickness of myocardium

Collateral flow

Supply

supply demand

factors• HR x BP• contractility

HistoryHistory

• Chest discomfort– Types of angina

• Quality of discomfort/location

• Provocative factors

• Relief

• Age/Gender/Risk Factors

• Classes of Angina

Physical ExaminationPhysical Examination

• hypertension• weight/body habitus• vascular bruits• heart size• skin• eye grounds

Resting ElectrocardiogramResting Electrocardiogram

Exercise Testing ProtocolsExercise Testing Protocols

Treadmill• Force = body weight• Distance/time=

Treadmill speed

• Estimated VO2 (ml/kg/min)– ACSM regression

equations– METs

Work = force x distanceWorkrate = work/time

VO2 is directly related to workrate

Stationary Cycle• Force = resistance

against the flywheel • Distance/time=

Cycling speed

• Estimated VO2 (ml/min)– ACSM regression

equations– Need body weight to

calculate METs

Time

ME

Ts

ME

Ts

Ramp

Stepped

10 min

Bruce Protocol for Treadmill TestingBruce Protocol for Treadmill Testing

Boston Medical Center Ramp ProtocolsBoston Medical Center Ramp Protocols

Duke Activity Status IndexDuke Activity Status Index

Diagnostic level of stress: 85% maximum predicted HRDiagnostic level of stress: 85% maximum predicted HR where MPHR = (220-age)where MPHR = (220-age)

Normal ResponseNormal Response

IschemicIschemicResponseResponse

Sensitivity/Specificity/Predictive ValueSensitivity/Specificity/Predictive Valuehigh prevalence populationhigh prevalence population

CAD No CAD PredictiveValue

PositiveTest

NegativeTest

Total N 9090 1010

exercise ecg test: 70% sensitive/ 70% exercise ecg test: 70% sensitive/ 70% specificspecific

6363

2727

33

77

9595

2121

Sensitivity/Specificity/Predictive ValueSensitivity/Specificity/Predictive Valuelow prevalence populationlow prevalence population

CAD No CAD PredictiveValue

PositiveTest

NegativeTest

Total N 1010 9090

exercise ecg test: 70% sensitive/ 70% exercise ecg test: 70% sensitive/ 70% specificspecific

77

33

2727

6363

2121

9595

x

x

x

x*

Duke Prognostic Scoring SystemDuke Prognostic Scoring System

Heart Rate RecoveryHeart Rate Recovery

Heart Rate Recovery:Heart Rate Recovery:Risk of mortality at 6 yearsRisk of mortality at 6 years

Cole, et al. NEJM 1999: 341:1351

Cleveland Clinic ETT ScoreCleveland Clinic ETT Score

Lauer, et al. Ann Int Med 147:821-828; 2007

Circulation 2010: 121: 2109

Hypertension During Exercise:Hypertension During Exercise:BPs > 180 at 7 METsBPs > 180 at 7 METs

Oxygen Uptake - Workrate relationshipOxygen Uptake - Workrate relationship

VO

2

Workrate

No handrail Handrail

??

CPX SystemCPX System

• Oxygen sensor

• Carbon dioxide sensor

• Volume measures/flow meters

• Breath by breath measures– BTPS

– Expired air

• Oxygen uptake

• Carbon Dioxide production

• Ventilation

Indications for CPXIndications for CPX• Accurate assessment of exercise capacity

– Clinical

– Research

• Diagnosis– Dyspnea on exertion

• Prognosis– Heart failure

– Congenital Heart Disease

• Disability assessment• Treatment

– Pacemaker settings

Exercise TestingExercise Testingadditional indicationsadditional indications

• Adequacy of therapy– medical– revascularization ( imaging tests)

• Activity counseling– MET Chart

• Exercise prescription• Rhythm assessment• Valvular Heart Disease

– Aortic stenosis– Mitral stenosis– Mitral regurgitation– Hypertrophic obstructive cardiomyopathy

Exercise PrescriptionExercise PrescriptionPatients with CHDPatients with CHD

• Intensity

– Exercise Test• calculate heart rate reserve (HRR)

– peak HR minus resting HR– moderate intensity:

» 50% HRR plus resting HR to» 70% HRR plus resting HR» keep peak peak HR 10 beats < HR at ischemia

– Risk Stratify using AHA criteria

Stress Imaging TestsStress Imaging Tests

•Abnormal resting ECG•ST segments•Left bundle branch block•LVH with strain

•Need for increaseddiagnostic accuracy

sensitivity 85-90% specificity 85-90%

•localize ischemia to specific coronary vascular territory

Contrast Echo

Stress Echocardiogram: Apical septal wall ischemiaStress Echocardiogram: Apical septal wall ischemia

Stress Nuclear TestingStress Nuclear Testingtomographic imaging planestomographic imaging planes

Short Axis•base to apex

Vertical Long Axis•septal to lateral

Horizontal Long Axis•anterior to inferior

normal nuclear perfusion scan

stress

stress

stress

rest

rest

rest

lateral ischemia on nuclear perfusion scan

stress

stress

stress

rest

rest

rest

Pharmacological Stress TestsPharmacological Stress Testsdobutamine echodobutamine echo

Dobutamine • beta agonist• increases myocardial oxygen demand• increases HR, BP, contractility

Pharmacological Stress TestsPharmacological Stress Testsnuclear perfusion scannuclear perfusion scan

Adenosine or Dipyridimole• direct coronary vasodilator• causes shifts in flow leading to relative reduction in flow distal to coronary stenosis• minimal change in HR, BP, and contractility

Myocardial Perfusion Imaging:Pharmacologic Positron Emission Tomography (PET) vs. Single Photon Emission Computed Tomography (SPECT)

PET• Energy: 511 KeV• Resolution: 1.5 cm• Protocol: 45 min• Stress EF• Myocardial flow

quantification• More expensive than

SPECT

SPECT• Energy: 80-140 KeV• Resolution: 2.0 cm• Protocol: 2-3 h ( or 2 d)• Post-Stress EF

Courtesy of Edward Miller, MD, PhD

For more informationFor more information

• www.americanheart.org–Scientific publications

•Statements and guidelines–Exercise standards -2013

Elective in Stress TestingElective in Stress Testing

• Second and third year residents

• 3 weeks – preferably continuous

• Fellow surrogate

• Certification in Exercise-ECG Testing – Supervision and interpretation

• Exposure to stress echo and stress nuclear

Body weight Exercise rate (kg · m · min-1 and watts)

kg Lb Kpms 300

Watts 50

450

75

600

100

750

125

900

150

1050

175

1200

200

50 110 5.1 6.9 8.6 10.3 12.0 13.7 15.4

60 132 4.3 5.7 7.1 8.6 10.0 11.4 12.9

70 154 3.7 4.9 6.1 7.3 8.6 9.8 11.0

80 176 3.2 4.3 5.4 6.4 7.5 8.6 9.6

90 198 2.9 3.8 4.8 5.7 6.7 7.6 8.6

100 220 2.6 3.4 4.3 5.1 6.0 6.9 7.7

Approximate METs during Stationary Cycle TestingApproximate METs during Stationary Cycle Testing

Myocardial ContractilityMyocardial Contractility

P ThR

Myocardial Wall StressMyocardial Wall Stress

Wall stress =P x R/ Th