Post #21: Diagnostic testing for Coronary Artery Disease - Part 1

Primary care providers often see patients presenting with atypical or non-angina chest pain and need to rule out coronary artery disease (CAD).  Cardiology guidelines consider these patients to have a low or intermediate pre-test probability (PTP) for CAD.  Studies support guidelines which recommend initially evaluating these patients with a traditional exercise treadmill test (ETT) under the following clinical scenarios: 

If these patients are physically able to walk on a treadmill, and if the ECG is interpretable for an ETT, and if the test is performed and is electrically and clinically negative, the likelihood of having ischemic CAD is extremely low and no additional testing is needed. 

If the patient with low to intermediate pre-test probability of CAD completes the ETT and it is unexpectedly positive or is equivocal, an imaging cardiac test (such as Stress ECHO or MPI) is indicated as a confirmatory test.  

Patients who present with typical angina type chest pain are considered to have a high PTP of CAD and should not have an ETT.  Instead, a Stress ECHO or MPI is the initial study and will be approved, as long as the requesting physician’s office makes it clear to the prior authorization company that the PTP is high.   

How to tell if chest pain is typical, atypical or non-cardiac? 
Cardiology guidelines describe 4 types of chest pain:
1. Typical (definite) angina -3 criteria
•    Sub-sternal chest discomfort (heaviness, pressure, burning or tightness).
•    Pain brought on by exertion or emotional stress.
•    relieved by rest or nitroglycerin.

  • Pain radiating to left arm or jaw

2.  Atypical probable angina: Chest pain/discomfort that lacks 1 of the 3 criteria of typical angina. 
3. Non-angina chest pain: Chest pain/discomfort that meets none or one of the typical angina criteria. Pain may be pleuritic, sharp, tender, knife-like,     pulsating or choking.    
4. Angina variants or equivalents: a perception by patients to be otherwise unexplained dyspnea or fatigue.

Cardiac guidelines use a Table of Pre-test Probability (below) to determine the likelihood that a patient has CAD.  This grid makes use of the patient’s age, gender, and symptoms.  Approval for any stress testing with imaging (stress ECHO, Myocardial Perfusion Imaging (MPI) or stress MRI) requires all 3 factors be considered especially a detailed clinical description of the type of chest pain.  

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Using the Table of PTP, patients with a low or very low probability should have an initial evaluation with an exercise treadmill test (ETT), which does not require prior authorization by insurance companies.  Many patients with intermediate PTP should also have an initial ETT unless some of the criteria listed below are present. 

If the patient has a high PTP, a stress test with imaging can be approved.  The provider’s office needs only facilitate approval by providing the 3 factors from the Table of Pre-test Probability or telling the radiology benefits managers that the patient has a high-pretest probability of CAD. 

In addition to Pre-test Probability, are there other factors that would support NOT doing an ETT and instead performing an imaging stress test?

ETT cannot be performed if the patient cannot exercise on a treadmill: 
Patients are often unable to perform an exercise test for various reasons.  These may include emotional or physical.  Arthritis, post-fall injuries, CNS disease, advanced pulmonary disease, claudication, or morbid obesity may preclude exercising.  Requests for a pre-op cardiac stress test prior to spine surgery or hip replacement obviously would be approved because these patients cannot walk on a treadmill.  Provider liaisons requesting a stress imaging study must communicate to RBM companies when the patient cannot exercise.  

The standard for exercise is 4 METS and is determined by answering 4 prior authorization questions. Can the patient  
•    walk up a hill?
•    walk 4 blocks without stopping?
•    walk up a flight of steps without stopping?
•    Perform heavy housework? 
  
The next posting will conclude the discussion on diagnostic testing for CAD.