Cardiac CT angiography is making its mark of diagnosis — as well as impacting the course of interventional procedures.
“Multidetector CCTA is one of the two or three most revolutionary things that I have personally seen…not just in diagnosis, but in treatment of cardiovascular disease,” says David E. Allie, MD, chief of cardiothoracic and endovascular surgery at the Cardiovascular Institute of the South (CIS) in Lafayette, La. As a classically trained cardiovascular surgeon with more than 35 years experience, Allie appreciates the remarkable benefits to patient care that 64-slice scanners afford.
A few years ago CIS acquired two Toshiba America Medical Systems Aquilion 16-slice scanners, which were replaced by three Aquilion 64-slice systems. They have just installed their fourth 64-slice machine and are looking to acquire a fifth soon. “It has now become the single most important diagnostic, follow up and treatment tool that we possess. I include CTA as a tool.”
CT enables them to know more about a patient’s blood vessels than ever before, and even more than traditional angiography, Allie details. “Now I know more about the blockage, the consistency, the type,” he says. “If there is calcium or not, is it plaque, or a thrombus? It allows me to know if I want to use a balloon, cryoplastic catheter or even bypass surgery. I can make all of those decisions 99 percent of the time before I put the patient into the hospital.”
Another advantage of 64-slice is the reduced volume of contrast agent required, which, in turn, decreases the incidence of contrast-induced nephropathy. By using intravenous administration of contrast for CT scans, he describes a decrease in the need for intra-arterial contrast that increases patient safety.
Many times CTA replaces traditional diagnostic angiography, Allie continues. This is particularly true in carotid artery studies where decisions are based on CTA results prior to the patient entering the cath lab. The same thing is true for thoracic and abdominal aneurysms. “CTA is better because it gives 3D pictures, so you don’t have to take multiple views with traditional contrast.”
When making decisions about where to insert a catheter, CTA provides information about “where to stick,” but more importantly, “where not to stick,” says Craig Walker, MD, founder and medical director, Cardiovascular Institute of the South (CIS) in Houma, La., that utilizes Aquilion 16- and 64-slice scanners for interventional planning. When lesions or calcifications are revealed, they avoid using that specific site.
Besides the obvious advantages of providing additional information for interventional procedures, Walker notes that often they visualize concomitant findings in soft tissue. He reports that they have found tumors at such early stages that cure is possible. “We have picked up a lot of lung tumors, abdominal aortic aneurysms, or renal artery stenosis.”
Further, 64-slice has revealed findings they would not see with conventional angiography such as using digital subtraction to inform stent placement.
Joao A.C. Lima, MD, director of cardiovascular imaging at Johns Hopkins School of Medicine in Baltimore is exploring the use of CCTAs in patients who are considered at intermediate or low risk of acute coronary syndrome (ACS). This includes asymptomatic individuals with a strong family history — sibling history has been found to be more important than parent history — who are imaged using one of their 64-slice Aquilion CT scanners.
Another cohort of patients who benefit from CT scanning are those who are scheduled for cardiac surgery. Lima describes a highly collegial relationship between radiologists and cardiac surgeons at Johns Hopkins, who have embraced this technology. “For example, for second bypass surgery, they generally ask us to image the graft sites to make sure they are not attached to the sternum, as well as provide a map of where the functional grafts are located before they go in.”
Lima also describes current use of CTA to guide atrial fibrillation ablations. A patient arrives in the morning and has a CTA resulting in images of the atrium that pinpoint the area where treatment is necessary. Those results are sent to the cardiac catheterization laboratory where they are used to guide ablation procedures. The CTA images are registered with the x-ray fluoroscopic data to guide the precise location of treatment area.
For sure, cardiac CTA is having a positive impact on navigating interventional