VIDEO: The expanding role of cardiac CT in electrophysiology

CT has been used for planning and procedural guidance in pulmonary vein isolation (PVI) for about 20 years. It shows the anatomy to the electrophysiologist. The EPs also can load the imaging into their EP mapping system to use as an anatomic shell to overlay electromapping points to see where electrical conduction issues are occurring in the heart muscle. 

"It also shows them the location of the esophagus and the phrenic nerve so they can avoid these during the procedures," Litt explained. 

EP ablation burns and kills cardiac tissue to stop errant electrical signals, but it also can cause damage to healthy, underlying tissues below an ablation site. He said for this reason EPs often want to know what the tissue thickness is in the areas around critical structures like the esophagus or phrenic nerve so the energy does not penetrate so deep. 

Knowing tissue thickness in the atrium of the heart can help tailor ablation procedures to specific patients to improve outcomes. 

"I think this is a really exciting application of imaging where the electrophysiologist will use quantitative information that we will given them by doing advanced image analysis to really help optimize the ablations for a particular patient," Litt explained. 

That advanced CT image analysis is also now being used to aid ventricular ablation procedures to identify myocardial scars. Litt said MRI is the gold-standard for scar imaging, but CT also can offer additional information. 

"We are using advanced CT image analysis to identify wall thickness and wall hypo-attenuation from perfusion abnormalities or fatty metaplasia to help the electrophysiologist identify the potential electrical circuits that are leading ventricular tachycardia," Litt said. "This is a new application of CT that I think will become very important."

While EP electro mapping systems have become much more advanced in the past few years, moving from a couple hundred data points to thousands of data points, there are still some things these apps cannot show EPs. Litt said this includes epicardial scar or intramural scar. 

"That is really where imaging has a role to play," Litt said. "CT is going to be very good at showing transmural and epicardial scar, but not so good for showing small amounts of sub-endocardial scar. If we know a patient has a sub-endocardial infarct, that is probably a patient you want to do an MRI on rather than a CT."