Cardiology 08

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ABSTRACT

Exercise test remains an important testing method because of itshigh yield of diagnostic, prognostic and functional information. Theelectrocardiographic (ECG) component remains critical not onlyfor diagnosis and prognosis but also for arrhythmia assessment,safety, heart rate measurement . Exercise test score combining

clinical and exercise have significantly improved the diagnostic andprognostic power of the test. The addition of echocardiographyor myocardial perfusion imaging does not negate the importanceof the ECG or clinical and hemodynamic response to exercise.Convincing evidence that treadmill scores enhance the diagnosticand prognostic power of the exercise test certainly has costefficacy implication.

INTRODUCTION

Several types of noninvasive stress tests are available for thediagnosis of coronary artery disease (CAD). Many patients areunable to undergo maximal exercise stress testing because ofphysical impairments or de-conditioning. In these patients,pharmacologic agents replace exercise.These tests combine eitherexercise or pharmacologic stress with an imaging method suchas nuclear perfusion or echocardiography. The pharmacologicalagent can be an inotrope such as dobutamine or a vasodilatorsuch as adenosine or dipyridamole. There is inconsistency inthe diagnostic characteristics of these stress tests1,2. Althoughreviews of pharmacologic stress testing have been conducted3,but they have not examined nuclear perfusion studies nor havethey incorporated current methodological recommendations formeta-analyses of diagnostic testing4-7. Exercise test remains animportant testing method because of its high yield of diagnostic,prognostic and functional information. The electrocardiographic(ECG) component remains critical not only for diagnosis and

prognosis but also for arrhythmia assessment, safety, heart ratemeasurement. Exercise test score combining clinical and exercisehave significantly improved the diagnostic and prognostic power ofthe test. The addition of echocardiography or myocardial perfusionimaging does not negate the importance of the ECG or clinicaland hemodynamic response to exercise. Convincing evidence thattreadmill scores enhance the diagnostic and prognostic power ofthe exercise test certainly has cost efficacy implication.

OPTIMAL UTILISATION OF STRESS TESTING VIS-À-VISOTHER IMAGING MODALITIES

Rajeev Gupta, Bhopal

EXERCISE STRESS TEST

Exercise is the preferred stress modality in patients who are ableto achieve at least 85% of age-adjusted maximal predicted heart

rate (MPHR) and five metabolic equivalents.Exercise stress testing is a powerful risk stratification tool and isuseful in assessing the efficacy of anti-ischemic drug therapy and/or coronary revascularization. The treadmill is the most widelyused stress modality. The most commonly employed treadmillstress protocols are the Bruce and modified Bruce. Upright bicycleexercise is preferable if dynamic first-pass imaging is plannedduring exercise.

INDICATIONS

Indications for an exercise stress test are:

• Detection of coronary artery disease (CAD) in patients

with an intermediate pretest probability of CAD based onage, gender, and symptoms, or in patients with high-risk fac-tors for CAD (i.e. diabetes mellitus, peripheral or cerebro-vascular disease).

• Risk stratication of post-myocardial infarction patients:

- Before discharge: submaximal test (often dened as

70% of the age-adjusted MPHR at 4-6 days. If test re-sults are negative, then later after discharge: symptom-limited at 3-6 weeks.

- Soon after discharge: symptom-limited at 14-21 days.

• Risk stratication of patients with chronic stable CAD into

a low-risk category that can be managed medically or ahigh-risk category that should be considered for coronaryrevascularization.

• Risk stratication of low-risk acute coronary syndrome pa-tients (without active ischemia and/or heart failure) 6-12hours after presentation or intermediaterisk acute coro-nary syndrome patients 1 to 3 days after presentation.



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• Risk stratication before noncardiac surgery in patients

with known CAD, diabetes mellitus, peripheral or cerebro-vascular disease.

• To evaluate the efcacy of therapeutic interventions (anti-

ischemic drug therapy or coronary revascularization) and intracking subsequent risk based on serial changes in myocar-

dial perfusion in patients with known CAD.CONTRAINDICATIONS

Contraindications are considered absolute or relative. Absolutecontraindications include:

• High-risk unstable angina. However, patients with chest painsyndromes at presentation, who are otherwise stable andpain free, can undergo exercise stress testing.

• Decompensated or inadequately controlled congestiveheart failure

• Uncontrolled hypertension (blood pressure > 200/110 mmHg)

• Uncontrolled cardiac arrhythmias (causing symptomsor he-modynamic compromise)

• Severe symptomatic aortic stenosis

• Acute pulmonary embolism

• Acute myocarditis or pericarditis

• Acute aortic dissection

• Severe pulmonary hypertension

• Acute myocardial infarction (less than 4 days)

• Acutely ill for any reason

Relative contraindications for exercise stress testing include:

• Known left main coronary artery stenosis

• Moderate aortic stenosis

• Hypertrophic obstructive cardiomyopathy or other formsof outow tract obstruction

• Signicant tachyarrhythmias or bradyarrhythmias

• High-degree atrioventricular block

• Electrolyte abnormalities

• Mental or physical impairment leading to inability to exer-

cise adequately

LIMITATIONS

Exercise stress testing has a lower diagnostic value in patientswho cannot achieve an adequate heart rate and blood pressureresponse.

If combined with imaging, patients with completeleft bundle branch block (LBBB), permanent pacemakers, andventricular pre-excitation (Wolff-Parkinson-White syndrome)

should preferentially undergo a pharmacologic vasodilator stress(not a dobutamine stress test).

TESTING PROCEDURE

Patients should not eat 2 hours before the test. Patients scheduledfor later in the morning may have a light breakfast.

Exercise stress tests require:• Properly trained nurses, physician assistants, and medical

technicians to administer tests and an appropriately trainedsupervising physician.

• Records of the heart rate, a 12-lead ECG, and blood pres-sure at each stage of exercise. Records should also be takenwith the appearance of any clinical symptoms. All measure-ments are repeated during recovery, typically every 3 min-utes for at least 5 minutes after cessation of exercise.

• Continuous electrocardiographic monitoring during the

test and in the recovery period. Monitoring is continued forat least 5 minutes into the recovery period or until the rest-ing heart rate is less than 100 beats per minute or dynamicST segment changes have resolved.

INDICATIONS FOR EARLY TERMINATION OF

EXERCISE

All exercise tests should be symptom-limited. Achievement of85% of age-adjusted MPHR is not an indication for terminationof the test.

In patients who cannot exercise adequately (eg., achieve 85% ofage-adjusted MPHR prior to radiopharmaceutical administrationand for at least 1 minute following radiotracer administration;achieve 5 METS or 5 minutes total exercise time on a Bruceprotocol), the radiotracer should not be injected at peak exerciseand a pharmacologic stress test should be considered. Bloodpressure medications with antianginal properties will lower thediagnostic accuracy of a stress test. However, testing patients withCAD on their anti-ischemic regimens may be useful in monitoringtheir response to therapy. Indications for early termination ofexercise include:

• Moderate to severe angina pectoris

• Marked dyspnea or fatigue

• Ataxia, dizziness, or near-syncope

• Signs of poor perfusion (cyanosis and pallor)

• Patient’s request to terminate the test

• Excessive ST-segment depression (> 2mm)

• ST elevation (> 1mm) in leads without diagnostic Q waves(except for leads V1 or aVR)

• Sustained supraventricular or ventricular tachycardia

• Development of LBBB or intraventricular conduction delay



Optimal Utilisation of Stress Testing VIS-À-VIS Other Imaging Modalities

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that cannot be distinguished from ventricular tachycardia

• Drop in systolic blood pressure of greater than 10mm Hg

from baseline, despite an increase in workload, when ac-companied by other evidence of ischemia

• Hypertensive response (systolic blood pressure > 250mm

Hg and/or diastolic pressure > 115 mm Hg)

• Technical difculties in monitoring the ECG or systolic

blood pressure

SUMMARY

The exercise test compliments the medical history and thephysical examination, and it remains the most informativetool for assessment of provocable ischaemia. The addition ofechocardiography or myocardial perfusion imaging does notnegate the importance of the ECG or clinical and hemodynamicresponse to exercise. Convincing evidence that treadmill scoresenhance the diagnostic and prognostic power of the exercise testcertainly has cost efficacy implication.

REFERENCE

1. Fleishmann KE, Hunink MGM, Kunta KM, et al Exercise echocardiog-raphy or exercise SPECT imaging. A meta-analysis of diagnostic testperformance. JAMA 1998;280:913-20.

2. Kwek Y, Klim C, Grady D, et al Meta-analysis of exercise testing todetect coronary artery disease in women. Am J Cardial 1999;83:660-6

3. Picano E, Bedetti G, Vargo A, et al. The comparable diagnostic accura-

cies of dobutamine-stress and dipyridamole stress echocardiographies:a meta-analysis. Coron Artery Dis 2000;11:151-9

4. Gibbons RJ, Chatterjee K, Dubey J et al, ACC/AHA/ACP-ASIM guide-lines for the management of patients with chronic stable angina: areport of the American College of Cardiology/ American Heart As-sociation Task force on Practice Guidelines (Committee on the Man-agement of Patients with Chronic Stable Angina). J Am Coll Cardial1999;33:2097-197

5. Irwig I, Tosteson ANA, Gatsonis C et al. Guidelines for meta-analysisevaluating diagnostic tests. Ann Intern Med 1994;120:667-76

6. Moses LE, Shapira D. Combining independent studies of a diagnostictest into a summary ROC curve: data-analytic approaches and someadditional considerations. Stat Med 1993; 12:1293-316.

7. Huber PL The behaviour of maximum likelihood estimates under non-standard conditions. In: LeCam I, Neyman J editors. Proceedings of theFifth Berkeley Symposium Under Nanstandard Conditions. Berkeley

(CA): University of California Press; 1967. p. 221-3.

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Cardiology 08