Cardiology Prior Authorization and Medical Necessity Documentation That Holds Up on Review

Written by: Shivam Pujara, Founder of Luxen

This article will help practice administrators and billing staff identify the prior authorization and medical necessity documentation most often missing from cardiology imaging and diagnostic testing claims and apply a practical checklist to keep those claims compliant with CMS and payer requirements.

Cardiology practices bill a high volume of high-cost diagnostic services that payers watch closely.

Echocardiograms, stress tests, nuclear and CT imaging, and cardiac device monitoring are costly, often repeated, and easy to order out of habit. That combination makes them a steady target for prior authorization rules, medical necessity edits, and post-payment review.

The problem is rarely that the test was not needed. It is that the record does not show why it was needed, or the authorization on file does not match what was performed. In our own claim audit at Luxen, of 61,400 claims reviewed from January 2025 to June 2026, missing or invalid prior authorization caused 17% of denials. The figures in this article come from our audits and billing reviews and reflect our experience, not national benchmarks.

Why Cardiology Services Draw Extra Scrutiny

Four service groups carry most of the risk:

• Advanced imaging, including nuclear myocardial perfusion, cardiac CT, cardiac MRI, and PET
• Echocardiography, including transthoracic, transesophageal and stress echo
• Stress testing, alone or with imaging
• Cardiac monitoring, including ambulatory ECG, event monitors, and implanted device interrogation

Each is tied to specific clinical indications, and many carry frequency limits.

What CMS and Payers Require

For Original Medicare, coverage starts with National Coverage Determinations (NCDs) and the Local Coverage Determinations (LCDs) published by each Medicare Administrative Contractor. Both are searchable in the Medicare Coverage Database. These documents list covered indications, the ICD-10-CM codes that support them and any frequency limits.

Three requirements come up in nearly every review:

1. A valid order. Under 42 CFR 410.32(a), diagnostic tests must be ordered by the physician treating the beneficiary, who uses the result to manage the patient’s specific medical problem. Tests not ordered by the treating physician are not considered reasonable and necessary.
2. Diagnosis linkage. Each claim line must point to a diagnosis that supports that service, coded to the highest specificity documented.
3. Prior authorization where the plan requires it. Original Medicare does not generally require prior authorization for office-based cardiac imaging, but Medicare Advantage plans and many commercial and Medicaid plans do. Under the CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F), beginning in 2026, Medicare Advantage organizations and Medicaid and CHIP payers must decide standard requests within seven calendar days and expedited requests within 72 hours, and must give a specific reason for any denial.

Documentation Gaps That Lead to Denials and Audit Risk

In our experience reviewing cardiology claims, the same gaps repeat:

• No authorization on file. Prior authorization was missing on 13% of advanced cardiac imaging claims in our audit.
• Authorization does not match the service. On 7% of advanced imaging claims, the authorization did not match the imaging actually performed, for example when a planned study changes on the day of service.
• Frequency limits missed. 9% of device interrogation and remote monitoring claims were denied for frequency.
• Component errors. Professional and technical component errors appeared on 7% of in-office diagnostic claims, such as a hospital-performed echo billed globally instead of with modifier 26.
• Thin medical necessity. Notes that list a symptom but not the clinical question, prior results, or why a repeat study is needed now.

Building a Compliant Pre-Service Workflow

Most of these denials can be prevented before the visit:

1. Verify eligibility and plan type at scheduling, so staff know whether authorization applies.
2. Request authorization for the exact CPT codes planned, including add-on codes, and record the authorization number, approved codes, units, and valid dates.
3. Re-check the authorization the day before service and update it if the test changes.
4. Check medical necessity against the applicable NCD or LCD, confirming the diagnosis code and frequency limits.
5. Use the ABN correctly for Original Medicare patients. When a service may be denied as not reasonable and necessary, such as a study beyond a frequency limit, give the Advance Beneficiary Notice of Noncoverage (Form CMS-R-131) before the service, not routinely to every patient. Report modifier GA when a valid ABN is on file and GZ when a denial is expected and no ABN was given.
6. Track remote monitoring periods by patient so periods do not overlap.

A Practical Checklist for Administrators and Billing Staff

Before a cardiology diagnostic claim goes out, confirm:

• A signed order from the treating physician, with the reason for the test
• A note clearly documenting symptoms, prior results and why the study is needed now
• A diagnosis code on each claim line that matches a covered indication
• An authorization number that matches the codes, units, and date of service
• The correct place of service and component modifier (26, TC or global)
• Frequency limits checked against the last billed study or monitoring period
• A signed ABN on file if the service may not be covered, with the matching modifier

Conclusion

Cardiology denials tied to authorization and medical necessity are mostly documentation problems, not clinical ones. Confirming the order, diagnosis link, authorization, and frequency before the service prevents most of them. Tracking why claims are denied matters too. In our billing reviews, 19% of denied claims were never reworked or appealed, which turns a fixable error into lost revenue.

Additional Resources

CMS: CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F) Fact Sheet

CMS: Advance Beneficiary Notice of Noncoverage (ABN)

Luxen: When Do You Split an Echo Into Professional (26) and Technical (TC) Components?

Luxen: How Do You Bill Remote Cardiac Monitoring Codes 93296 and 93297 for the Same Patient?

Luxen: Common Reasons for Medical Claim Denials and How to Appeal Them

Copyright © 2026 American Institute of Healthcare Compliance All Rights Reserved