Medical Device Daily Washington Editor
SAN FRANCISCO — Makers of imaging equipment might not be flocking to conventions populated largely by cardiologists, but several sessions at this year's Transcatheter Cardiovascular Therapeutics gave physicians a chance to sound off on the subject of imaging technologies. One such session offered up CT angiography as a bone of contention, but the consensus seemed to be that reports of the modality's demise are "greatly exaggerated."
An interesting view on the risks of repeated exposure to X-radiation also emerged from the discussion, a view that holds that those risks are greatly exaggerated as well, and pale in comparison to the hazards of an untreated infarct.
Arguing the skeptic's view as to whether CT angiography is headed for extinction when examining patients who seem at risk for an infarct was John McB. Hodgson, MD, chairman of cardiology for the Geisinger Health System (Danville, Pennsylvania) who opened by asking, "are we screening to find early disease?"
Hodgson took the position that cardiologists should be screening to head off infarcts and said that running a patient in and out of a multi-slice CT machine is not a bad deal at all for the patient compared to the alternative. "Exposing your groin, drugging you and sticking you in the leg" with a catheter to conduct a coronary angiography session is not such a great experience, he asserted, and is unnecessary given that contrast-aided CT will do the job.
"The classic risk factors fail to identify who has stenosis," Hodgson reminded attendees, arguing that "screening asymptomatic patients makes sense" where diabetic patients are concerned. Without explicitly saying so, he made the case that most patients will never go along with the idea of a catheter-based angiography solely for the purpose of screening. Hodgson also said that screening allows a physician to triage patients and limits interventional procedures to those who exhibit a definite need for interventional treatment rather than allow a catheter into the body on a speculative basis.
"There are a host of studies," Hodgson said, that demonstrate that 64-slice CT offers "fantastic negative predictive value" for infarction, "but you might [also] find atherosclerosis, which can be treated."
As to whether CT can pick up a range of morphologies of interest, Hodgson said, "we can see intimate details" of relevant structures, citing contrast studies done with electron beam tomography, a variant of CT, conducted by Ostrom, et al, and appearing last year in the Journal of the American College of Cardiology.
Making the case that CT angiography is or will soon be over the hill was Bernhard Meier, MD, of the Swiss Cardiovascular Center (Bern, Switzerland), who argued, "all we need is coronary angiography."
Meier's position was that invasive angiography can "give you the hemodynamic significance of stenosis" and accurately depict pressure gradient and flow reserve. "Most important of all, it includes therapy" if the physician so chooses. "It's a one-stop shop," he said.
"We can do more with invasive cardiology" than with external modes, Meier said, stressing the point that "no other imaging modality will give you this dynamic" imaging in reference to images displayed on the screen in the room.
Meier said the procedure "is not a dangerous thing to do" given that the deaths per thousand have fallen drastically over the years to three. Another advantage of intra-arterial imaging is its accuracy. No matter how insignificant the feature, "CT will always see it and make a lot of fuss about nothing," Meier said, adding that while snapshot protocols have lowered the X-ray dose associated with CT, it "will theoretically induce one leukemia per 600 cases," assuming the use of multislice equipment.
With CT, "you cannot repeat procedures, resolution is poor, and artifacts continue to bother us," Meier asserted, adding, "calcification is a problem" for X-ray technology.
Hodgson reinforced the high negative predictive value of CT angiography, stating, "the chance you're missing anything important there is very low," but he took exception to the comments about the dangers of exposure to X-radiation.
"I have a hard time with the radiation stuff" because "if you happen to roll out of bed and come into the ER, you get a head-to-toe CT with no thought at all," Hodgson remarked. Addressing the frequency at which infarcts kill Americans, he said, "we can get diagnostic screening CTs" and eliminate numerous cases of "the number one cause of death in the country" with one imaging session, he said.
Medical Device Daily asked the panel's members whether any of them had an informal standard for how many exposures a patient might have before they would decide to forgo a CT angiography session for fear of sparking a cancerous episode. Daniel Berman, MD, of the Cedars Sinai Heart Institute (Los Angeles), said: "Radiation is important, but I think we're overemphasizing these low-dose exposures."
Berman said most of the data that are suggestive of outcomes such as leukemia come from unusual situations and are inappropriately extrapolated to more garden-variety circumstances, such as routine medical imaging. "We don't have data suggesting" this is problematic, he said.
Mark McCarty, 703-966-3694;