CARAT Tutorials: Coronary Artery Total Occlusions

Total coronary artery occlusions can be seen in a variety of acute and chronic clinical settings: this tutorial outlines the data fields in CARAT that can provide relevant angiographic, functional and procedural detail for patients with chronic total occlusions.

Lesion entry:

While in the Lesion edit mode (check the lower left corner of the page), the first step in drawing a total occlusion is to trace a lesion, proximal to distal, and the severity is set at a default value of ‘50%’. The second step, as with all lesions, is to ‘right click’ the lesion revealing the sub-menu shown in Figure 1 asking that the appropriate lesion grade be selected. For our purpose, we will select ‘100%’.

Figure 1: Selecting Lesion Severity.

The ‘100%’ selection will automatically open the Total Occlusion menu shown in Figure 2 allowing the operator to enter key descriptive information. The first designation is Duration of the total occlusion, if known. Chronic total occlusion is usually defined as angiographic or clinical evidence of occlusion > 3 months or ‘Unknown’.  When either of these choices is selected, the other data elements on the drop-down showing key features of the Total Occlusion are activated (turn from grey to black) as in Figure 3 allowing further data entry. The Duration field also allows one to specify if the totally occluded segment has been bypassed and, if so, is the surgical conduit compromised. (Prior Cardiac Surgery is included as a discrete item as a prior opening of the pericardium is believed to confer an element of safety in the event of procedure-related pericardial bleeding.)

Figure 2: Total Occlusion Duration.

Figure 3 shows the Total Occlusion characteristics that can be documented: type of collaterals, lesion length, features of the proximal and distal cap, adjacent side branches and, importantly, whether there is evidence of prior infarction or regional wall motion abnormality in the region supplied by the total occlusion.

Figure 3: Chronic Total Occlusion Detail.


Description of collaterals and TIMI flow are important to total occlusion assessment. When Collaterals is selected from the menu, tracing their pathway, from donor vessel to recipient, will record these important connections. When drawn, right-clicking on the collateral will activate a collateral drop-down menu which allows you to highlight important collaterals and enter collateral detail, as in Figure 4 below. The Origin and Termination of a collateral is recorded automatically with an opportunity to distinguish between epicardial and trans-septal pathways, single or multiple and whether the collateral is believed to be suitable for retrograde wiring if intervention is being considered. Two commonly used collateral classification systems (Rentrop and Werner) can be specified as well.

Figure 4: Collateral Properties.

Selecting TIMI Flow from the main menu and specifying the nature and location of each flow grade change should be undertaken at this point as well.

Intervention Detail:

If PCI is attempted, the menu specifying Interventional Detail can be accessed in one of two ways depending on whether or not a stent is deployed. With no stent deployment, Lesion edit mode is selected from the main menu, the total occlusion is right-clicked and Interventional Detail is selected and the requested information is entered. Where a balloon is inflated without a stent being subsequently used, a “B” designation is left on the lesion in question to indicate that a POBA was performed (no stent).

If a stent is deployed the device menu is selected differently: first the stent is right-clicked while the stent is still shaded in pink (active state) and Interventional Detail is then selected. The lesion or stent origin and termination points are automatically specified along with initial and final LDR.

At this point three separate tabs are available when either pathway. The first (Figure 5 below) asks for information on the access point(s) and sheath French size.

Figure 5: Interventional Detail: Access.

The third tab identifies specific procedural strategies, unique to CTO intervention, that were used (Figure 6).

Figure 6: Interventional Detail: Strategies.

Finally, the Device detail tab is selected allowing a comprehensive sequential display of all devices used, including deployment detail (Figure 7). The deploy date will default to the date of the current procedure; however if there is a need to document previously deployed stents, the deploy datefield is adjustable and is available for this purpose.

Figure 7: Intervention Detail: Devices.

At this point all devices used can be documented sequentially. Initially Add is selected and the Device Type is chosen from the drop-down list in Figure 8. In this example, the operator wished to document that a Pilot 200 wire was used. Then the Device Model field is selected providing a fairly comprehensive list of currently available wires (Figure 9). (In most PCI procedures there is little value in documenting wire usage. However wire choices can be documented for future reference when this information may be of future use.)

Figure 8: Intervention Detail: Device Type.

Figure 9: Procedural Detail: Device Model - Wires.

(Although sequential device use descriptions for more complex re-entry and retrograde strategies are possible, a simple antegrade procedure is used in this example.)

The Add button is now again activated and Balloon is selected revealing the range of balloons currently available (Figure 10). A SPRINTER Legend balloon was chosen and the fields that follow allowed documentation of the balloon diameter, length and maximum inflation pressure used.

Figure 10: Procedural Detail: Device Model - Balloon.

At this point Add can be activated yet again to reveal Stent options with the ability to specify size and inflation detail (Figure 11).

Figure 11: Procedural Detail: Device Model - Stent.

For illustration purposes, we will assume that a high-pressure balloon was used for post-stent dilatation using a Voyager NC balloon and, finally, the procedure was assessed finally using IVUS. The final tabulation of all devices used, their order and size/deployment detail is documented in the tables on the upper left portion of the page as shown in Figure 12. (If other equipment such as atherectomy, thrombectomy, OCT, FFR assessment or even IABP or support devices were used in the procedure, this activity could be included in this tabulation as well, and in proper sequence.)

Figure 12:  Final Device tabulation.

Key Points: