SCAI: Where and how angio falls short in the cath lab
The causes of non-diagnostic angiograms, according to Abbott, are broken down into two categories:
- The fault of the operator because angiography can only be as good as the quality of the images taken; and
- Limitation of the technology of angiography because even experienced operators cannot always get a diagnosis from the angiogram alone.
The operator’s technique should depend on a variety of factors, including:
- Patient factors, size, movement and hardware (such as implantable devices).
- Appropriate catheter selection and manipulation: “Selective engagement is necessary for appropriate contrast filling,” said Abbott. “If you can’t fill a coronary due to severe aortic insufficiency or severe left ventricular hypertrophy, then you may need to employ a slightly different technique.”
- Injection technique: She said that complete opacification is required, for which she said an automatic system can sometimes work well.
- Imaging: Breath holds, collimators and frame rate/panning can be used to optimize imaging. “People shouldn’t rush through the imaging procedure,” she said.
- Equipment quality.
She noted the “eccentric nature of plaque,” which is difficult to overcome with angiography, but the goal is to account for all vascular territories, including anomalous coronaries and bypass grafts. Also, due to plaque’s histopathology, it is important to obtain multiple views because arteries can appear more or less occluded based on the angiographic angle—ranging from 20 or 30 percent to 90 percent.
Incomplete angiographies are not uncommon, as there are many challenges of anomalous coronaries, according to Abbott. Thus, she often recommends to her fellows to review the left ventricular gram to see where the coronaries are coming off before catheter selection to engage the coronary. Despite these efforts, she acknowledged that it is “very different to selectively engage anomalous coronaries, so try to recognize the signs and review the left ventricular gram.” In the most extreme cases, alternative imaging techniques, such as CT angiography or MR angiography, may need to be used to help define a portion of the coronaries.
In addition to the operator issues, the technological limitations of coronary angiography include its inability:
- To detect the presence and extent of plaque, requiring physiologic remodeling;
- To detect plaque content, such as calcium, vulnerable plaque and thrombus;
- To detect the functional significance of the disease, or the severity of intermediate lesions; and
- To assess stent deployment and PCI-related dissection.