Off Script: Opacity, Transparency, and Magic Buttons in the Cath Lab

We are so focused on ‘seeing’ in procedures, we sometimes fail to fully understand the implications of delivering ionizing radiation on this scale.

SAN DIEGO, CA—Despite the progress of the last few decades in the cath lab, it has taken a surprising amount of time for interventional cardiologists to turn our full attention to our invisible friend: life-altering, tissue burning, DNA-modifying radiation. There are more and more indications for performing tests that involve ionizing radiation, yet we are so focused on ‘seeing’ in procedures, we sometimes fail to fully understand the vast implications of delivering ionizing radiation on this explosive scale. At the same time, we are typically slow to implement the rapidly improving technology designed to protect our patients, our colleagues, and ourselves.

This year marked the publication of the 2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Efficacy, created by the primary cardiology and radiology bodies involved in the populational distribution of ionizing radiation. The document was an update of interventional cardiology guidelines from SCAI, published in 2011 and 1992, and is a welcome addition to the improving, pragmatic set of documents codifying and disseminating best practice.

This document represents a milestone of progress, but we still have much to do. Presenting at a moderated Cath Lab of the Future: Radiation Reduction abstract session this morning, I had showed Michigan statewide data from the Blue Cross Blue Shield prospective multi-center registry of PCI. The data show a wide distribution of PCI patients exposed to greater than 5 Grays of radiation during PCI. This range varied from <1% to 12% by institution. That span is by no means an indictment of a specific center or provider since many factors may increase levels of radiation exposure including procedural complexity, obesity, and patient acuity. But the numbers demand we pay careful attention to the reasons for the variability and look for ways to improve.

For variables we can control, we have a moral imperative to reduce the dose administered as dictated by the ALARA (As Low As Reasonably Achievable) principle. My presentation today chronicled an interesting observation I made while visiting a friend at Mayo Rochester. Following a long PCI case, I noticed their significantly lower radiation levels compared to my own lab. On investigation, I found a single button you could press to lower your radiation dose. Given that I had the same lab equipment, it struck me that I might have the same button. To both my surprise and dismay, I did indeed have the same button, and had for some time, although not in an obvious spot, having been installed as an update at some point prior. I pushed the button in July of last year. When we analyzed my last 700 cases, half of which were performed post-button with nothing else changed, radiation levels had been reduced by a staggering 54%. This was a Magic Button.

Figuring out how it worked proved tricky, but we did eventually get an answer and realized there were many subtle and complicated reasons why I and many of my colleagues around the country were not aware of either the existence of the Magic Button on this specific line of equipment or its potential effect on our radiation exposure. This was even after I discovered a paper written about the Magic Button in JACC Interventions from 2014. The idea of the Magic Button does highlight the remarkable progress the companies making our equipment have made in returning control to us, the operators, to lower radiation dosing and to increase the quality of lower-dosed imaging. Even in the last 10 years, we have seen significant progress in logging how much radiation is administered per case (hint, fluoroscopy time is a very poor substitute and actually does not include cine time) and in our ability to “live monitor” our cath lab staff. We do however, still have much to do with tracking patient exposure at the institutional level.

Any reduction in radiation inevitably results in a decrease in quality. Fortunately for me, the Button did not (in my mind) diminish picture quality although some of my colleagues were less content with the new images, albeit without a blinded comparison. This afternoon, an old mentor of mine said that he feels complications occasionally occur as we start to barter for ever-shrinking radiation levels in return for hazy images. Apparently, the threshold of image quality has to be individualized to the operator, the clinical setting, and the stakes involved.

Ideally we’d each have our own, personalized Magic Button. For some, less is more, but for others, less may simply be less.


Kwan S Lee, MD is an Associate Professor of Medicine at the Sarver Heart Center, University of Arizona.  As interventional…

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