Cardiology denial rates are climbing in 2026 as MAC LCD policies tighten around imaging, structural-heart procedures, and modifier 26/TC splits. Here are the 10 denial codes our team sees most often — and exactly how to fix each.
Why cardiology denial rates spike in 2026
Three forces are colliding: (1) Novitas, NGS, and Noridian all revised cardiac imaging LCDs in late 2025, (2) commercial payers are auditing structural-heart (TAVR, MitraClip) charges more aggressively, and (3) the new G0427 cardiac PET code drove a wave of medical-necessity denials. Practices that had 92-95% clean claim rates last year are reporting 85-88% in early 2026.
#1: CO-50 (Medical necessity / LCD mismatch)
What it means: The diagnosis doesn’t support the procedure per the MAC’s Local Coverage Determination. Fix: Pull the MAC’s most current LCD for the CPT code, verify ICD-10 is on the covered list, and use the LCD’s exact diagnostic criteria in the documentation. For cardiac CT (75571-75574), Novitas requires explicit chest-pain or coronary-anomaly indications.
#2: CO-97 (Bundling — modifier 26/TC error)
What it means: You billed both professional (26) and technical (TC) components when the global was paid. Fix: If your practice owns the equipment and provides the interpretation, bill global (no modifier). If you only read the study (read for a hospital), bill 26. Don’t bill TC without ownership. Common error on echo (93306-93308) at hospital-based clinics.
#3: CO-16 (Missing or invalid documentation)
What it means: The claim is missing required attachments — typically the report, prior auth number, or referring provider NPI. Fix: Build a charge-entry checklist that confirms: signed report, prior auth on file, referring NPI populated, and Z-codes for screening attached. Re-submit with the missing element via 837P resubmission.
#4: CO-167 (Provider not on referring list)
What it means: The referring provider isn’t credentialed with the payer. Fix: Verify referring NPI on PECOS for Medicare and through each payer’s directory for commercial. For new referrers, request a credentialing update before the next claim cycle. Tag practice management to add a payer-by-payer referrer status column.
#5: CO-95 (Medically unlikely edit / MUE)
What it means: You billed more units than CMS allows on a single date of service. Fix: Check the CMS MUE table before billing — for example, 92928 PCI stent insertion has an MUE of 4. If you legitimately exceeded, use modifier 76 (repeat procedure) with documentation of why each instance was distinct.
#6: CO-204 (Service not covered)
What it means: The payer doesn’t cover the service for this benefit plan. Fix: Confirm pre-service via eligibility verification. For Watchman (33340) or LAAO procedures, get a written coverage determination in advance. If denied post-service, file appeal with peer-reviewed literature attached.
#7: CO-151 (Payment adjusted by review)
What it means: The payer reduced payment after reviewing documentation. Fix: Review the EOB rationale carefully — usually a downcoding (e.g., level 4 to level 3 E/M). For cardiology, the most common is unbundled-to-bundled on cath procedures. Appeal with 2021 MDM documentation or unbundling-justified clinical rationale.
#8: PR-49 (Routine examination)
What it means: The service was deemed preventive/screening when billed as diagnostic. Fix: If the patient had symptoms, the documentation must clearly state the symptom-based indication. For asymptomatic screening, bill with appropriate Z-codes and verify the screening interval was met.
#9: CO-A8 (Modifier UN / B + G error)
What it means: Combination of modifiers triggered a reject. Fix: When billing a primary procedure with same-session secondary (e.g., echo with stress), use modifier 51 (multiple procedure), not 76 (repeat). Don’t combine UN with bilateral 50. Reference the MAC’s modifier matrix.
#10: CO-22 (Coverage indicators)
What it means: COB issue — another payer should have been primary. Fix: Verify insurance coordination via the payer’s Eligibility Verification System (EVS). For Medicare patients with auto-related cardiac care, MSP applies — bill the auto carrier first. Update the patient’s COB record in your PM system.
AMS denial-management workflow
Our cardiology billing team works denials in a 3-step cycle: (1) identify the rejection reason code within 24 hours, (2) pull supporting clinical documentation from the EHR, (3) resubmit or appeal with corrected coding plus a denial-response template tailored to each MAC’s preferred appeal format. Average turnaround: 5-7 days for resubmission, 14-30 days for first-level appeal.
Need help getting your cardiology denial rate back under 5%? Our 90-day audit is free for new practices. Call (214) 571-6317 or book a 30-minute review. While you’re here, grab our free 2026 Cardiology CPT Cheat Sheet.
