Well, because we all want the diagram to be as helpful and accurate as possible.
Branch options presented with the Template Tabs on the right half of the CARAT window are limited to unbranched selections with standard sizing (1 to 3 myocardial segments supplied) and standard locations (basal, mid and apical locations for diagonal, ALM and ILM for marginal branches and medial and lateral locations for posterolateral branches). When more detail is needed to convey clinically important anatomic variation, ‘right clicking’ on a branch or segment in need of modification exposes a new menu of modification options. This tutorial highlights several opportunities available.
A comprehensive and useful angiographic report should not attempt to replicate every feature of a patient’s coronary anatomy as individual variability is too great and many features are of little clinical consequence. However, many details are of value and every attempt should be made to capture and characterize those of clinical and procedural relevance.
When a branch origin requires modification, the ‘Move Branch’ function can be selected after right-clicking on the branch requiring an adjustment. As an illustration, observe the proximal marginal in Figure 1 and notice the branch location with respect to the 80% LCx lesion.
If you wish to move the anterolateral marginal branch closer to the LM, place the mouse arrow on the branch between the first two nodes (Figure 2), click and hold the left mouse button, and drag the vessel to the desired new location (Figure 3).
(Notice that Reduced Flow Regions on the 17-segment circumferential polar plot and the APPROACH Jeopardy score in the upper right corner automatically changed to reflect the new side branch location with respect to the 80% lesion.)
It is important to keep the first node of the branch being moved within the boundaries of the parent vessel.
This function is intended only to alter a branch origin: it does not change the myocardial distribution assigned to the branch.
After the branch has been moved, it is possible (in the same menu selection) to grab on to and move other nodes along the length of the artery to make a more favorable appearance and to avoid overlapping other vessels or disease elements.
The top portion of the menu exposed by left-clicking on a branch or segment to be altered provides a list of alternate configuration choices (Figure 4). (Try selecting each one to learn the configuration options that are available.)
In this example, we have selected a configuration that branches proximally with symmetric arms (Figure 5), but multiple other options with varying branching configurations and pathways are also available to portray clinically important variations.
The standard basal, mid, and apical branch placements establish a fixed relationship between branches and myocardial regions. (This will be described in greater detail in the Myocardial Jeopardy Tutorial).
Occasionally, however, a pair of branches may actually originate from a single basal, mid, or apical location. This paired or Dual branching option is included in the Figure 4 drop-down menu presenting an opportunity to portray a pair of branches within a single region. (See Figure 6).
This action effectively creates a second proximal diagonal, and the software then assumes that the two new branches now share equally the myocardial region supplied by the originally unbranched proximal diagonal.
The last item on the configuration menu, Edit Vessel, opens a wide range of vessel segment editing possibilities (largely beyond the scope of this review). We advise that the edit option be used with caution, at least until the operator is comfortable with pre-formed options available.
When Edit Vessel is selected and a vessel for editing is right-clicked, a second drop-down menu is presented as in Figure 7. As shown, this menu allows you to reposition labels, move assigned bypass graft target locations and add explanatory text to the diagram. (Altering a default bypass graft target location is the most common use of the Edit Vessel menu.)
From this menu you can also select Edit Line with yet another drop-down menu shown in Figure 8 that presents the ability to move and delete nodes, extend the length of a line segment and make other changes to Drawing Properties of lines as shown in Figure 9. These edit functions are most useful in portraying clinically important morphology variations, such as a severe RCA Shepherds Hook, tortuosity in a diseased segment, or important angulation variations at a bifurcation lesion.
In CARAT, Vessels (for example a diagonal or a marginal branch) are composed of lines, each line designating the portion of a vessel that passes over a single LV myocardial segment (see green arrow in Figures 8 and 9 representing the portion of the branching basal ramus branch that passes over the mid anterolateral region 12).
The Line Properties submenu defines graphic features of lines and, most importantly, indicates the LV segment, and portion thereof, to which the line is assigned (key to the automated myocardial jeopardy calculation process).
• Moving a segment or branch will alter the origin but not the distribution region of the segment or branch.
• Use the ‘Edit Vessel’ function only when the desired change is clinically important and when the desired appearance cannot be achieved by a default configuration change.
• If you get too ‘off-track’ in your editing, it is best to reselect the starting branch template in question and try again.
• If you cannot access the menu you want, chances are you are still in a previous ‘Edit Mode’. Check the taskbar on the lower left corner of the screen to confirm. This corner ‘Edit Mode’ box must be empty before the branch configuration editing functions can be activated.
• When using the ‘Move Branch’ function, (or any other function requiring fine adjustments to vessels or other graphic items), we strongly suggest you use the ‘Zoom’ function activated by your mouse scroll wheel.
• The mouse arrow must be within the branch boundaries when starting and finishing a drawing function.