Bypassing the bypass guidelines for the coronary and peripheral arteries

Forget the coding guidelines (at least temporarily) – let’s focus on the procedures first.

The classic first step in coding is to read the guidelines, but in the case of many ICD-10-PCS guidelines, starting there may prove to be confusing and frustrating. I’ve always been a big fan of learning the “why” behind the “what,” and when it comes to coding and coding guidelines, I like to identify the method behind the madness. The madness I’d like to address in this article relates to ICD-10-PCS coding guidelines for arterial bypass procedures.

The ICD-10-PCS definition of the root operation Bypass is “altering the route of passage of the contents of a tubular body part.” In the case of the arterial system, the tubes are the arteries of the heart, as well as noncoronary circulation. The term “bypass” isn’t unique to the medical profession. We talk about bypasses in traffic or figurative bypasses at work when we develop “workarounds” to circumvent a problem. An arterial bypass is no different: there is a blockage we need to get around, and to do that, we must make a new pathway.

That ends the simplicity of the root operation Bypass. Because then we look at the ICD-10-PCS coding guidelines, which are a confusing mess. Does that sound a little harsh? Well, let’s just take a look at the first bypass guideline:

B3.6a: Bypass procedures are coded by identifying the body part bypassed “from” and the body part bypassed “to.” The fourth character body part specifies the body part bypassed from, and the qualifier specifies the body part bypassed to.

That second sentence is a mental tongue twister! But if we focus on the procedure first and then come back to the guideline later, I promise it will make more sense. So, let’s briefly talk about anatomy and blood flow.

The center of the circulatory system is the heart. Blood leaves the left side of the heart through the main artery, the aorta, which connects to other arteries. The arterial mission is simple: deliver oxygen-rich blood to the body’s organ and tissues. At the cellular level, oxygen is released to the tissues and carbon dioxide is absorbed and routed to the veins, which empty into the main vein, the vena cava, which returns blood to the right side of the heart. From there, blood is sent to the lungs, where another gas exchange occurs as carbon dioxide is released during expiration and oxygen is absorbed during inhalation. Blood is routed back to the left side of the heart and the process is repeated.

In my view, the key to coding bypass procedures is knowing how blood is flowing, because that is what determines the “to” and “from” body parts to which the guideline refers. 

Let’s take a noncoronary example. Bypasses from the femoral artery to the popliteal artery (fem-pop) are relatively common. Arterial blood flows away from the heart, so the first body part to receive fresh blood will be the femoral artery, and the popliteal will be the second. Therefore, when re-perfusing the leg below the area of blockage, blood is coming from the femoral artery (fourth-character body part value) to the popliteal artery (seventh-character qualifier value). 

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Official coding guidance continues to confound by switching it up for coronary artery bypass graft (CABG) procedures with the next guideline:

  • B3.6b: Coronary artery bypass procedures are coded differently than other bypass procedures as described in the previous guideline. Rather than identifying the body part bypassed from, the body part identifies the number of coronary arteries bypassed to, and the qualifier specifies the vessel bypassed from.

At first glance, it seems confusing, but again, it’s all about blood flow. The first lucky organ to receive fresh blood supply is the heart muscle itself. Blood flows from the aorta to the coronary arteries. In an aortocoronary bypass, coronary occlusions are treated with two main types of bypass: aortocoronary and internal mammary. In both cases, the body part being bypassed “to” is the coronary artery or arteries, but the body part bypassed “from” varies, depending on the where the graft is connected on the other end. 

If you’re wondering why the body part and qualifier values for coronary arteries are reversed from every other type of bypass, the evidence is in the tables. The coronary artery body parts are classified to the Heart and Great Vessels body system in ICD-10-PCS. The body parts listed as qualifiers for coronary bypass, on the other hand, can be found in one of three body systems: Heart and Great Vessels, Upper Arteries, and Lower Arteries. To keep all CABG procedures in the same 021 table, the body part becomes the coronary artery – the body part bypassed “to” and the qualifier the body part bypassed “from.”

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I mentioned two main types of CABG: aortocoronary and mammary graft. In an aortocoronary bypass, a connection is made from the aorta to the coronary artery using a free graft. That free graft can be made of arterial or venous tissue obtained from the patient (autologous), cadaver tissue (nonautologous), animal tissue (zooplastic), or synthetic material. The most common type of free graft comes from the saphenous vein from the patient’s leg. Pedicled grafts may also be used, where an artery is detached from its distal point and rerouted to the coronary arteries. This is most commonly achieved using the internal mammary arteries. It is not uncommon for a single operative session to include bypass of multiple coronary arteries using multiple devices. 

The final bypass guideline addresses code assignment when multiple coronary arteries are bypassed and have different devices and/or qualifiers:

  • B3.6c: If multiple coronary arteries are bypassed, a separate procedure is coded for each coronary artery that uses a different device and/or qualifier.

The type of graft, free versus pedicled, determines the sixth character for the device. Free grafts are coded using the first row in the 021 table, and the device is the source of that graft material (e.g., autologous venous tissue). Pedicled grafts are not classified as devices in ICD-10-PCS because they remain attached to their original blood supply. For this reason, pedicled grafts are coded using the second row of the 021 table, which only has one device option, No Device.

Example: Two-vessel CABG using autologous saphenous vein graft from the aorta to the distal right coronary artery and acute marginal branch and one-vessel pedicled left internal mammary artery (LIMA) bypass to the circumflex using an open approach.


  • 021109W, Bypass coronary artery, two arteries from aorta with autologous venous tissue, open
  • 02100Z9, Bypass coronary artery, one artery from left internal mammary with no device, open

Rationale: Two of the arteries were bypassed using a saphenous vein graft from the aorta. The other artery was bypassed using a pedicle LIMA graft. Since two of the arteries had a different device and qualifier than the other, two codes are necessary when we apply coding guideline B3.6c.

Coronary and peripheral arterial bypass procedures can be tricky and the guidelines can be baffling, but if you focus on the anatomy and always remember blood flow, you can master the bypass guidelines.

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