Post #23: Diagnostic testing for Coronary Artery Disease – Testing before  Non-Cardiac Surgery 

One common imaging request received by Radiology Benefits Management (RBM) companies is for pre-op testing before scheduled elective surgery. Many providers feel that their patients need testing because the stresses of surgery may trigger a cardiac event, and knowing the status of the coronary arteries before surgery may prevent a myocardial infarction.  

Cardiology guidelines have reviewed benefits and risks from pre-op testing, and have concluded that the need for such testing and the type of test performed depends upon two factors: 
•    the patient’s current medical status and
•    the type of surgery planned.  

This blog will address both issues to help providers determine if testing is needed, and what specific test would be supported by these guidelines.  By selecting the test most likely to be approved and by providing the clinical information to RBM nurses, it is likely that an approval will be forthcoming.  Remember that there are three stress tests commonly performed: traditional ETT, stress ECHO, and myocardial perfusion imaging (MPI) each with their strengths and weaknesses. 

The first issue to consider is the status of your patient.  Guidelines assume patients about to have elective surgery are stable and have no active cardiac symptoms. Certain co-morbidities, however, would support a pre-op stress test as long as stress testing has not been performed within the past year.  (Some RBM companies extend that time frame to 2 or even 3 years and require patients be unable to walk on a treadmill).  Check specific RBM guidelines). 

Status of Your Patient: Co-morbidities or Clinical Risk factors

•    If patients have a history of ischemic heart disease (defined as one of the following: a prior MI, use of nitroglycerin, past typical angina, Q waves on ECG, a previous CABG or PCI) the risk of intra-operative non-fatal MI or cardiac death are sufficient to warrant pre-op testing.  Next question deals with the type of surgery planned.   
•    If patients have a history of congestive heart failure (previous pulmonary edema, bilateral rales, third heart sound, elevated BNP, or x ray or ultrasound evidence of CHF) there is sufficient risk of intra-operative complications and  pre-op testing is warranted.  Next question deals with the type of surgery planned.   

•    If patients have a history of TIA, stroke, endarterectomy or high grade carotid stenosis, renal insufficiency (creatinine > 2) or diabetes pre-op testing is supported.  Proceed to second question: what is the surgery planned. 
Note that these are co-morbidities (or risk factors) and are specific to pre-operative testing and are not the same as the Framingham clinical risk factors.  Hyperlipidemia, hypertension, family history, obesity, and smoking are not considered co-morbidities for determination of pre-op testing. 

Occasionally a provider will request a cardiac stress test at the time of a surgical procedure for new signs or symptoms of cardiac disease that may be unrelated to the intended non-cardiac surgery.  If the patient would qualify for MPI or stress ECHO independent of the planned surgery, imaging stress testing can be approved, as long as this documentation is communicated to the RBM nurse. 

Some RBM companies’ guidelines stated pre-bariatric surgery or pre cardiac rehab are not indications for an imaging stress test, only an ETT. However, if patients have any of the co-morbidities listed above, MPI or stress ECHO may be approvable.  Some RBM’s guidelines consider new onset atrial fibrillation to be an indication for MPI. 

Which stress test to order? 
In rare cases, an exercise treadmill test (ETT) could be performed as a pre-op stress test and does not require prior authorization.  However, in practice, many patients whose co-morbidities would support some type of stress test, are not candidates for ETT.  For example, many patients requiring surgery cannot walk on a treadmill or their abnormal ECG renders the ETT un-interpretable (see post #22).  Prior to back, knee or hip surgery, walking on a treadmill may not be possible.  Similarly, many patients with CHF, diabetes with neuropathy, or prior strokes cannot perform an ETT.  Since stress ECHO also requires physical exercise, many pre-op patients are ineligible for this study as well, so myocardial perfusion imaging (MPI) would be the only alternative.  

Patients with a history of CAD are automatically considered high pre-test probability for CAD and thus would be a candidate for an imaging stress test (MPI or stress ECHO) as long as one had not been performed within the past year.  

Type of Surgical Procedure Planned

The second issue simply determines the risk of intra-operative cardiac events based on the type of surgery planned.  The table below places each procedure into one of 3 categories: High Risk, Intermediate Risk, and Low risk. 

Low risk procedures do not warrant imaging stress testing (unless the patient would be a candidate for imaging stress testing independent of the planned surgery).  

Patients planning high-risk surgical procedures may have an imaging stress test (MPI or stress ECHO) if one has not been performed within the past year (or if a stress test has previously been performed but new cardiac symptoms or ECG changes have appeared since the test).  

For intermediate surgical procedures, whether stress testing is supported or not depends upon clinical risk factors or co-morbidities described above.  If the patient has at least one co-morbidity and has not had a stress test within the past year, myocardial perfusion imaging can be approved.  

As with any prior authorization request, it is critical that the prior authorization liaison (PAL) in your office communicate with the RBM nurse if patients cannot walk on a treadmill or have had prior PCI or CABG or any other co-morbidities.  If prior authorization nurses are given all the relevant clinical information, approval will be forthcoming and denials and peer-to-peer calls can be avoided.  

Cardiac Risk Stratification based on Complexity of Surgery/procedure

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Lesson #23:  Pre-surgical screening for cardiac disease depends upon three factors: the clinical status of the patient, the risk of the procedure planned and communication of clinical information from the provider’s office to the RBM. 

The next post will review cardiac testing after patients have previously undergone angioplasty/stent, coronary artery bypass or other re-vascularization: the type and frequency of testing.