Cardiology billing carries more risk of quiet underpayment than people expect, since a single visit often combines diagnostic testing, interventional procedures, and chronic disease management, each needing its own code and modifier. A bundling or modifier mistake on something like a stress test or catheterization can reduce reimbursement without ever triggering an obvious denial. Cardiology medical billing services need coders who track these combinations carefully, since a missed detail on a high-cost cardiac procedure has a much larger financial impact than the same oversight would have on a routine, lower-cost office visit.