RICHARD BROWNE, MD SANGER CLINIC CARDIOLOGY

RICHARD BROWNE, MDSANGER CLINIC CARDIOLOGY

STRESS TESTING FOR CORONARY ARTERY DISEASE WHAT IS BEST CHOICE FOR YOUR PATIENT

STRESS

Any stimulus, as fear or pain, that disturbs or interferes with the normal physiological equilibrium of an organism

-The Random House College Dictionary-

Common Types of Stress Tests

Routine Treadmill (ECG only) Exercise Echocardiography Exercise Nuclear Stress Dobutamine Echocardiography Dobutamine Nuclear Stress Adenosine Nuclear Stress Persantine Nuclear Stress

Three States of the Sodium Channel and the Normal Sodium Current (INa)

Ca++

outin

out

in

Na+/Ca++

Exchanger

Ca++

Ca++

Ca++

Ca++

Na+

Na+

Na+

Na+Na+

Na+

Na+

RestingClosed

Na+

Activated Inactivated

Na+

Na+

Na+ Ca++

Ca++

0

Late

Peak

SodiumCurrent

[Na]140 mM ~ 10mM

Ischemia Induced Effects on Late INa andIntracellular Calcium

Ca++

Na+/Ca++

Exchanger

Ca++

Na+

Na+Na+

Na+

Na+

Na+Na+Na+

Na+

Na+

Ca++Ca++Ca++

Ca++

Ca++Ca++ Ca++

Ca++

Ca++

Ca++ Ca++

Excess Calcium:• Electrical instability• Contractile

dysfunction• ECG changes

0

Late

Peak

out

in

outin

Na+

Na+

Na+

Na+ Ca++

Ca++

ImpairedInactivation

Ca++

SodiumCurrent

Cellular Mechanism of Ischemia

Consequence(s) of Mechanical DysfunctionMechanical Dysfunction

• Abnormal Contraction and RelaxationAbnormal Contraction and Relaxation

• Diastolic TensionDiastolic Tension

O2 Consumption(to maintain tonic contraction)

ATP Hydrolysis

Diastolic Wall Tension (Stiffness)Diastolic Wall Tension (Stiffness)

OO22 Demand Demand OO22 Supply Supply

Extravascular Compression

Blood Flow to Microcirculation( O2 delivery to Myocytes)

Modified from: Belardinelli et al. Eur Heart 8 (Suppl. A):A10-A13, 2006

How good is exercise ECG testing?

Gianrossi R, Detrano R, Mulvihill D, et al. Exercise-induced ST depression in the diagnosis of coronary artery disease. Circulation 1989; 80:87-98.

Meta-analysis of 147 consecutive studies involving 24,074 patients

62

6466

68

70

72

7476

78

SENSITIVITY SPECIFICITY

Sensitivity Comparison of Different Testing Modalities

0102030405060708090

100

1 vessel 2 vessel 3 vessel All CAD

Stress ECGStress ECHONuclear

SPECIFICITY OF DIFFERENT STRESS TESTING MODALITIES

0102030405060708090

Stress NuclearStress ECGStress ECHO

“The Best Things in Life are Free” Janet Jackson & Luther Vandross, 1994.

GOOD NEWS: Imaging modalities improve the diagnostic accuracy of stress ECG testing.

BAD NEWS: Cost is substantial. Professional Fee Technical Fee Total Cost

Exercise Stress Test

$250 $172 $522

Stress Echo

$429 $258 $687

Myocardial Perfusion

$539 $1395 $1934

Questions to Ask When Picking a Test

Can the patient exercise on the treadmill or is pharmacological stress testing needed?

Can the patient have a routine stress ECG treadmill test or is adjunctive imaging (Nuclear or ECHO) needed?

If imaging needed, which one should be used? If pharmacological stress needed instead of

exercise, which agent to use?

Information obtained from Exercise Stress but not available with Pharmacological Test

Exercise Duration/Tolerance Reproducibility of Symptoms with Activity Heart rate response to exercise Blood Pressure response Detection of Stress Induced Arrhythmias Assess control of angina with medical therapy Prognosis

DUKE TREADMILL SCORE Duration of exercise on treadmill (in minutes)

Amount of ST segment depression (in millimeters)

Treadmill Angina index: 0 = No Angina 1 = Non-limiting Angina 2 = Limiting Angina

DUKE TREADMILL SCORE

Duration of exercise on treadmill (in minutes) minus 5x (millimeters of maximal ST segment depression) minus 4X (treadmill anginal index)



Example: Patient walked on treadmill for 11 minutes without chest pain. ECG showed one mm of ST segment deviation.



Example: Patient walked on treadmill for 11 minutes without chest pain. ECG showed one mm of ST segment deviation.

Duke Score: +6 = 11 minus 5x (1) minus 4x (0)

PROGNOSIS: DUKE TREADMILL SCORE

0

5

10

15

20

25

Four Year Event Rate

+5 or Greater-10 to +4Less than -10






Patients Appropriate for Routine ECG Stress Test without Imaging

Patient can exercise for 6 or more minutes

Normal baseline ECG

No history of diabetes

No history of coronary revascularization

No history of myocardial infarction






Advantages of Stress Echocardiography Compared to Nuclear Stress Testing

Higher Specificity Visualization of cardiac valves Evaluate for presence of pericardial effusion Ability to measure RV Systolic Pressure More accurate assessment of LV ejection fraction Doppler interrogation to determine Diastolic Function Lower Cost Lack of Radiation Exposure

Factors decreasing sensitivity of exercise stress echocardiography

Ischemic myocardium can resume function in as little as 10 seconds after exercise so the “ischemic moment” can be missed if images are obtained too long after exercise completed

Small vessels may not create large enough of an ischemic zone to generate a wall motion abnormality that is detectable

Suboptimal visualization of endocardium

PRE-OPERATIVE RISK STRATIFICATION WITH DOBUTAMINE STRESS ECHO

05

1015202530354045

Operative Cardiac Event Rate

Ischemia at<60% MPHRIschemia at>60% MPHRNo Ischemia

*Mayo Clinic, 530 Patients

Advantages of Nuclear Stress Testing Compared to Stress Echocardiography

Higher Technical Success Higher sensitivity especially for single vessel

and branch vessel disease

Sensitivity Comparison of Different Testing Modalities

0102030405060708090

100

1 vessel 2 vessel 3 vessel All CAD

Stress ECGStress ECHONuclear



and branch vessel disease Better accuracy in evaluating ischemia in the

setting of baseline wall motion abnormalities

Myocardial Infarction with small zone of adjacent ischemia




setting of baseline wall motion abnormalities Better assessment of severity and size of

ischemic zone

Nuclear Imaging: Assessment of size and severity of Ischemia




setting of baseline wall motion abnormalities Better assessment of severity and size of

ischemic zone More published data on evaluating prognosis






DOBUTAMINE

Activates beta receptor resulting in increased heart rate and myocardial oxygen demand

Works by inducing myocardial ischemia May be arrhythmogenic (0.7% rate in 8500

consecutive studies performed at Mayo Clinic) Usually ineffective in patients on beta blockers High rate of side effects Does not interact with dipyridamole

Different Degrees of Coronary Blood Flow

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.04.5

mg/miin/g

Baseline Adeno Dipy Dobuta Exercise

Blood Flow

ADENOSINE NUCLEAR STRESS TESTING

111

RESTING STATE

NORMAL CORONARYBLOOD FLOW PRESENTIN ABSENCE OF ANYSTENOTIC LESIONS


111

555

RESTING STATE ADENOSINE STRESS


111

5/5

5/55/5



111

111


NORMAL ADENOSINE NUCLEAR SCAN

ADENOSINE NUCLEAR DETECTION OF CORONARY ARTERY DISEASE

111

RESTING STATE

LOCAL VASODILATORS ARE RELEASED IN ANATTEMPT TO MAINTAINCORONARY BLOOD FLOW


111

525



111

5/5

2/55/5



111

10.41




111

525


PATIENT EXAMPLE

62 year old male with history of tobacco abuse is admitted to the hospital with several episodes of chest pain. ECG shows non-specific STT abnormalities. Troponin value is 0.95 and creatinine is 3.2.

Telemetry shows occassional ventricular couplets. It is understood that cardiac catheterization carries high risk of permanent renal failure.

ADENOSINE and THREE VESSEL DISEASE

111

RESTING STATE

LOCAL VASODILATORS ARE RELEASED IN ANATTEMPT TO MAINTAINCORONARY BLOOD FLOW


111

222



111

2/2

2/22/2



111

111


FALSE NEGATIVE ADENOSINE NUCLEAR SCAN WITH THREE VESSEL DISEASE


FALSE NEGATIVE ADENOSINE NUCLEAR SCAN WITH THREE VESSEL DISEASE

111

111


Left Bundle Branch Block and Stress Testing


Abnormal septal motion is noted during stress echocardiography resulting in decreased accuracy in physician interpretation

Reversible defects of the septum are noted during exercise or dobutamine nuclear imaging resulting in increased false positives

Left Bundle Branch Induced Septal Defect During Exercise Nuclear Test


Bottom line: Stress testing that does not increase heartrate (adenosine nuclear) is best for patients with Left Bundle Branch Block

CONCLUSIONS

Situations Where Treadmill ECG Sufficient

Whenever possible, perform exercise stress testing rather than pharmacological

If a patient can walk on treadmill (Bruce Protocol) for 6 minutes, has a normal ECG, and does not have diabetes, has not had a myocardial infarction or previous PCI or CABG, stress ECG testing can be performed without additional imaging modality

Situations Where Nuclear Imaging Preferred Diabetics

Previous Myocardial Infarction

Reduced LV ejection fraction

Left Bundle Branch Block (with Adenosine)

Significant COPD

Hospitalized patient with positive enzymes

Situations Where Stress ECHO Preferred Younger patients with lower likelihood of symptomatic

coronary artery disease

Pericardial Disease suspected

Valvular heart disease needs to also be evaluated

Need to evaluate for pulmonary hypertension

Exertional dyspnea is the predominant complaint

Situations Where Stress ECHO and Nuclear Probably Equivalent

Coronary artery disease patients with preserved LV systolic function and without previous myocardial infarction or diabetes

Pre-operative Risk Assessment

Adenosine is Preferred over Dobutamine except in the following situations

Echocardiography is chosen imaging modality and patient cannot exercise

Patient taking dipyridamole

Patient who cannot exercise and are prone to pulmonary bronchospasm

Patient with more than first degree heart block

RICHARD BROWNE, MD SANGER CLINIC CARDIOLOGY

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