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CCS Prep

Rerouting of a Tubular Body: Coronary Artery Bypass Graft Coding

When people ask me about the CCS exam preparation, I say, "There is always a heart question on the exam." I suggest studying the anatomy of the heart, blood flow and the common heart procedural coding. Each candidate should have a grasp of the heart conduction system and devices as well, because this will be essential to coding cardiac pacemaker procedures.

In this article, we will discuss the coronary artery bypass graft procedure frequently referred to as CABG (pronounced cabbage), which is indicated for treatment of coronary artery disease (CAD) and some myocardial infarctions.

CABG is one of the most commonly performed major heart operations. The surgical intervention is done in response to plaque build-up in the coronary arteries of the heart. The CABG procedure is the final solution in treating coronary artery arteriosclerosis, after medical and other less invasive interventions have failed. A CABG is always an open procedure and requires extracorporeal circulation during the procedure (pump oxygenator/cardiopulmonary bypass). This article will only address the procedure on a native heart without previous procedural interventions.

The CABG Procedure

The CABG procedure is performed when the coronary arteries become obstructed with plaque (arteriosclerosis), which interferes with their function to oxygenate the heart muscle. The procedure is performed by placing/attaching a vein or artery around or over the diseased coronary artery to bypass the diseased area, and re-establish oxygen-filled blood flow to the heart muscle. The bypass graft is normally attached to the aorta and carried down to bypass the diseased coronary artery.

The bypass artery or vein graft then takes over the function of the clogged coronary artery and returns oxygen flow to the heart muscle. The function of the coronary arteries as they branch off from the aorta is to carry oxygen-rich blood to the heart. ICD-9-CM volume III tabular list includes the relationship between the aorta and coronary artery by titling the procedure code "(aorta) coronary bypass." The most frequently harvested veins and arteries harvested from other parts of the body for this procedure are: the saphenous vein graft (from the upper leg); left or right internal mammary artery (IMA), also called internal thoracic artery (ITA) (from the chest area); and on rare occasions the upper extremity (arm) vein (radial or ulnar) and the femoropopliteal vein. 

  • Internal Mammary Arteries: IMA or ITA, grafts are the most common bypass grafts used, as they have shown the best long-term results. Normally, these arteries can be kept intact at their origin, which is another advantage, because they have their own oxygen-rich blood supply. They are sewn to the coronary artery below the site of the blockage. If the surgeon removes the mammary artery from its origin, it is called a "free" mammary artery. Over the last decade, more than 90% of all patients received at least one internal artery graft.
  • Saphenous Veins:  The other regularly seen graft is the saphenous veins. These veins are removed from the leg and then sewn from your aorta to the coronary artery below the site of blockage. Minimally invasive saphenous vein removal may be performed and results in less scarring and a faster recovery.
  • Radial Artery: The radial artery is one of two arteries in the lower part of the arm; the ulnar is the other. Most people receive adequate blood flow to their hand from the ulnar artery alone and will not have any side effects if the radial artery is removed and used as a graft. This graft is less commonly used.

Coronary Arteries

The coronary arteries extend from the aorta to the heart walls supplying blood to walls surrounding the atria, ventricles and septum of the heart. The myocardium of the heart muscle requires oxygen and nutrients, just like any other tissue in the body. But the blood that passes through the heart's chambers is only passing through on its way to oxygenate the rest of the body. This blood does not give oxygen and nutrients to the myocardium. The myocardium receives its oxygen and nutrients from the coronary arteries. The coronary arteries lie on the outside of the heart and supply oxygenated blood to the heart tissue.

There are two main arteries - the right coronary artery and the left main coronary artery. Additionally, the left coronary artery branches into small arteries - the left anterior descending (LAD) artery and the left circumflex (LCX) artery.

Table 1: Operative Anatomy 

Diseased Vessels Needing Intervention



Bypass Grafts Harvested


Right coronary artery (RCA)



Greater saphenous vein

Leg/lower extremity

Left coronary artery (LCA)

  • Left anterior descending (LAD)
  • Left circumflex artery (LCX)



Left or right internal mammary artery

Thoracic - subclavian

Since the operative risk of mortality is high, a CABG is always an inpatient-only procedure.  We will review the inpatient coding guidelines for ICD-9-CM coding of CABG.

Inpatient Coding

Abstracting information from the operative report requires knowledge of the procedure and the vessels involved. The code assignment is based on the number of coronary arteries treated. The coder will also have to determine if this is a bypass procedure involving the aorta or a subclavian artery. The difference is the source of the graft procedure. ICD-9-CM volume codes are arranged to identify the source and type of bypass that was performed.

Table 2: ICD-9-CM Volume Codes

Bypass from aorta

Bypass from subclavian artery

36.11 (Aorto) coronary bypass of one coronary artery 

36.15 Single internal mammary-coronary artery

36.12 (Aorto) coronary bypass of two coronary arteries

36.16 Double internal mammary-coronary artery

36.13 (Aorto) coronary bypass of three coronary arteries


36.14 (Aorto) coronary bypass of four or more arteries


Codes:  36.11- 36.14 will be used for grafts harvested from the leg (e.g., saphenous vein)
Codes: 36.15 and 36.16 will be used for grafts harvested in thoracic area (R or L internal mammary artery)

Instructional notes under code 36.1- Bypass anastomosis for heart revascularization: 

  • Code also cardiopulmonary bypass [extracorporeal circulation] (heart-lung machined) 39.61
  • Tip: The determining factor for coding an aortocoronary artery bypass graft operation is the number of coronary arteries involved rather than the number of grafts.

Table 3: Case Study 1 & 2 Comparison

Case 1: CABG w/saphenous vein (2  coronaries)

Case 2: CABG w/left internal mammary (1  coronary)

68-year-old man is undergoing a two coronary artery bypass operation for occlusion of the LCX and RCA. The available left internal thoracic artery (LITA) was not long enough, and a saphenous vein graft (SVG) was selected instead.  Patient was on pump during procedure.

68-year-old man is undergoing a single coronary artery bypass operation for occlusion of the LAD. The available left internal artery (LITA) was used as the saphenous vein graft (SVG) was inferior in structure. Pt was on pump during procedure.

Case Study 1 ICD 9 CM Codes:

36.12  (Aorto) coronary bypass of two coronary arteries

+ 39.61 Cardiopulmonary bypass [extracorporeal circulation] (heart-lung machined)

Case Study 2 ICD 9CM Codes:

36.15 Single internal mammary-coronary artery

+ 39.61 Cardiopulmonary bypass [extracorporeal circulation] (heart-lung machined)

There is always a bill for the surgeon performing the CABG operation to represent his work.  This bill will contain the CPT codes representing the procedure. 

Professional (CPT) Coding of CABG

Coding CABG procedures with CPT is different than applying the ICD-9-CM inpatient volume III codes. CPT codes are coded based on the type of graft (venous, artery or combined artery and venous graft), where as the inpatient ICD-9-CM codes are coded based on sites of coronary arteries bypassed.

The Current Procedural Terminology codes have a surgical section for heart operations with instructions on coding. CABG procedures are represented by codes 33510- 33536.

  • 33510-33516 Venous Grafting Only for Coronary Artery Bypass
  • + 33517-335023 Combined Arterial-Venous Grafting for Coronary Bypass (add-on codes)
  • 33533-33536 Arterial Grafting for Coronary Artery Bypass 

Specific CABG CPT Guidelines

1. CPT codes 33510 - 33536 are applied based on the type of bypass graft: saphenous vein, left internal mammary artery (LIMA), upper extremity vein (add 35500 to bypass procedure), or femoropopliteal vein (report 35572 in addition to bypass procedure), and the number of coronary arteries bypassed.

2. Venous Grafts 33510-33516 are never reported with add on codes +33517 through +33523. They would not be reported with 33533-33536 during the same encounter either.

3. Venous Grafting 33510-33536 include the harvesting (procurement) of the saphenous vein for bypass. If the saphenous vein was not used, an additional code must be added for other veins used for the bypass procedure (i.e., add 35500 if upper extremity vein is harvested, or 35572 if a femoropopliteal vein is harvested).

4. Add-on codes Coronary Artery bypass-Sequential Combined Arterial-Venous Grafting codes 33517-33523 are never used alone. These codes, 33517-33523, represent the venous graft in the Combined Arterial-Venous CABG procedures. 

5. Arterial Grafting for Coronary Artery Bypass codes 33533-33536 are used to report Coronary Artery bypass procedures only or a combination of arterial-venous grafts.

Table 4: Case Study of Inpatient Codes & CPT Physician Codes

Coronary Artery Bypass Procedure, x 3  with combined  artery/venous


78-year-old man has diffuse coronary artery disease in his Left Anterior Descending (LAD), Left Circumflex Artery (LCX) and Right coronary Artery (RCA). He is prepared for a triple bypass of these three arteries using a portion of the saphenous vein and the left internal mammary artery.  A portion of the saphenous vein was harvested from the right femoral leg and attached to the aorta and carried down to bypass the two occlusions, one in the LAD and then one in the LCX (vein x 2).  We then detached the lower half of the left internal mammary artery from the subclavian artery and carried it over the occlusion of the RCA (artery x1).  Patient was on pump during entire procedure.



Inpatient Codes

36.12 (Aorto) coronary bypass of two coronary arteries

36.15 Single internal mammary-coronary artery bypass

+ 39.61 Cardiopulmonary bypass [extracorporeal circulation]

Profee Facility Coding CPT

33533 Coronary artery bypass, using arterial graft; single

+33518 Coronary artery bypass , using venous graft and arterial grafts;  2 venous grafts

Note: The order of the CPT codes  requires that the +33518 add-on code be sequenced second.


Lindsey Asmus, RHIT CCS CCS-P CCDS, is an approved AHMA ICD 10 CM/PCS trainer and the content editor manager for Precyse University ( She has more than nine years of experience coding and auditing in both inpatient and outpatient settings.  She taught as an adjunct instructor at an AHIMA-approved college in the Health Information Technology associate programs. She is currently a co-facilitator of the Florida CSA and Studying for the CCS, community of practice (COP) for AHIMA members.

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Rerouting of a Tubular Body: Coronary Artery Bypass Graft Coding

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