Alison Lovkay

Why have a stress test?

There are several reasons why a stress test is performed. Often it is when a person is experiencing chest pain and it used to see if there are any changes on the EKG. For it to be a diagnostic test, the patient must reach at least 85% of the predicted max heart rate. Max heart rate is found by taking 220-age. If there are changes on the EKG, and they have reached that 85%, than it would be concluded as a positive stress test. At Miriam Cardiac Rehab, we aren’t doing stress tests for a diagnostic purpose. We want to know what they can do within their diagnosis. We find their functional capacity by taking the time x protocol. We use that value, in Mets, to get an idea on how capable they are with exercise. We also use their peak heart rate on the stress test to determine where their target heart rate should be in class. We look at their heart rate, blood pressure, RPE, ST changes, ectopy, arrhythmias, symptoms and any chest pain that they have during the test. If they had ectopy at rest, does it get worse with exertion? Does their heart rate increase dramatically even with medications? Do they have any limitations, such as arthritis or joint pain? Do they have to stop because of shortness of breath or because of bilateral calf pain? We use the stress test as a starting point for the patients and when they have their exit stress test, we hope that their results improve and their functional capacity is greater. 

 

How is target heart rate created from the stress test?

Determining a target heart rate depends on if the test is negative or positive. If the test is inconclusive, then it is a negative test. The patient will be working at 75-85% of their peak heart rate. A technique called Karvonen is also used, and that is taking 50-70% of max and subtracting their heart rate reserve. If the test was a submaximal test because of orthopedic problems, their peak HR will be their target HR.

 

If the test is positive, and they have ST changes 1 mm or greater, their target HR will be their ischemic threshold- 10 beats per minute. If they had a positive nuclear test, there are different directions it could go. If it showed fixed defects, indicating infarction has happened and the heart tissue is dead, they should not be ischemic. Their target heart rate will be the same as if it were a negative test. If it is reversible, meaning the tissue is viable but could potentially die if pushed too hard, the target heart rate will be much lower (usually around 65% of their max heart rate).

 

A positive echocardiogram will show whether or not a patient is akinetic, hypokinetic, dyskinetic and hyperkinetic. If the patient is akinetic at rest and during exercise, the test is negative and their target heart rate remains the same. If they are akinetic during exercise, it is a very serious problem and they cannot be part of the program. If they are hypokinetic during exercise, they will be working at 65% of their max heart rate. Dyskinesia is only a problem if the patient goes into A-fib. 

 

 

Contraindications:

1. High-risk unstable angina. However, patients with chest pain syndromes at presentation, who are otherwise stable and pain free, can undergo exercise stress testing.

2. Decompensated or inadequately controlled congestive heart failure

3. Uncontrolled hypertension (blood pressure >200/110 mm Hg)

4. Uncontrolled cardiac arrhythmias (causing symptoms or hemodynamic compromise)

5. Severe symptomatic aortic stenosis

6. Acute pulmonary embolism

7. Acute myocarditis or pericarditis

8. Acute aortic dissection

9. Severe pulmonary hypertension

10. Acute myocardial infarction (less than 4 days)

11. Acutely ill for any reason

 

Reasons for termination:

1. Moderate to severe angina pectoris

2. Marked dyspnea or fatigue

3. Ataxia, dizziness, or near-syncope

4. Signs of poor perfusion (cyanosis and pallor)

5. Patient’s request to terminate the test

6. Excessive ST-segment depression (> 2mm)

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

8. Sustained supraventricular or ventricular tachycardia

9. Development of LBBB or intraventricular conduction delay that cannot be distinguished from ventricular tachycardia

10. Drop in systolic blood pressure of greater than 10mm Hg from baseline, despite an increase in workload, when accompanied by other evidence of ischemia

11. Hypertensive response (systolic blood pressure > 250mm Hg and/or diastolic pressure > 115 mm Hg)

12. Technical difficulties in monitoring the ECG or systolic blood pressure