Friday, February 13, 2015

Cardiac Stress Testing

Older patients presenting to an outpatient clinic with non-acute chest pain frequently have an underlying cardiac etiology. Once the decision is made to evaluate for CAD, how should the workup proceed? Here is one approach.

1. Referral to a cardiologist can be made simultaneously with initiation of the outpatient workup. Many but not all patients will need to see a cardiologist regardless of test results. It can significantly decrease time to diagnosis if workup is initiated at the same time as the referral.

2. Perform an EKG and standard blood tests.

3. Order a stress test. Type of stress test is primarily influenced by EKG findings, the pre-test probability, and patient's ability to adequately exercise.

4. EXERCISE TREADMILL: treadmill only testing is generally indicated for low risk patients who are able to adequately exercise and have an interpretable ECG.

5. STRESS IMAGING: stress SPECT imaging is generally recommended in patients with any of the following:
  • ECG changes that can interfere with treadmill stress testing alone, including: LBBB, digoxin use, baseline ST-T abnormalities, ventricular paced rhythm, Wolff-Parkinson-White, greater than 1 mm ST depression at rest.
  • Patients unable to adequately exercise to 5 METS ( = 3 minutes on the Bruce Protocol).
  • Intermediate risk patients

6. CONTROVERSY: should intermediate risk patients initially undergo exercise treadmill testing? Many experts say yes. The primary question to ask is, "if the treadmill stress test is negative, am I comfortable ending the workup at that point?"

Here is an example algorithm:

Why is stress SPECT the most commonly performed stress imaging study? One reason is because it is highly quantitative, making the results highly consistent from one lab to another. Advances in computer software have greatly decreased the subjectivity of scan interpretation. Scan interpretation is very consistent across a wide range of clinical settings.

  1. Selecting the optimal cardiac stress test. UpToDate website. Accessed February 13, 2015. COMMENT: is an excellent source for current medical information for clinicians. Highly recommended.
  2.  Chung EK, Tighe D. Pocket Guide to Stress Testing. Wiley-Blackwell; 1997. COMMENT: this is an excellent guide to stress testing, focusing primarily on treadmill stress testing. Very thorough and a good reference.