Less is more when it comes to radiation exposure in young heart disease patients undergoing diagnostic tests and invasive procedures. Physicians in Cleveland Clinic Children’s Center for Pediatric and Congenital Heart Disease are having success in achieving reduced levels in their patients.
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“We know the risks of radiation exposure are dose-dependent and cumulative over time, which makes reduction of radiation exposure in pediatric patients imperative,” says pediatric electrophysiologist Peter Aziz, MD. That’s particularly the case for patients with congenital heart disease, who will undergo multiple procedures throughout their lives.
The past year saw the continuation or culmination of a flurry of efforts by Cleveland Clinic Children’s cardiologists to substantially curb their patients’ radiation exposure by shortening procedure times, adopting leading-edge equipment and deploying new techniques that promote low- or no-radiation testing.
The capstone of those efforts was the early 2014 opening of a second pediatric catheterization laboratory, equipped with the latest detector technology, the Artis Q.zen angiography system (Siemens Healthcare). The system, which employs a crystalline (vs. amorphous) silicon detector, reduces electronic noise, thereby allowing imaging at much lower radiation levels than previously possible.
“This technology appears to reduce radiation exposure by as much as 50 percent without sacrificing image quality,” says Lourdes Prieto, MD, Director of the Pediatric Catheterization Laboratory.
The system also is equipped with an advanced X-ray tube that uses flat emitter technology to provide small focal sizes and strong, short X-ray pulses for improved contrast and spatial resolution of small moving vessels.
The new cath lab joins Cleveland Clinic Children’s hybrid catheterization lab, which allows a cardiologist and a thoracic surgeon to work together on patients with complex congenital defects, reducing procedure time (and thus radiation exposure) as well as anesthesia and recovery time ‒ and sometimes avoiding the need for cardiopulmonary bypass.
Cleveland Clinic Children’s interventional cardiologists have worked closely with medical physicists to develop a series of algorithms based on patient weight and planned procedure to minimize radiation exposure in both cath labs. As a result, they achieved a 40 percent reduction in radiation exposure during transcatheter pulmonary valve implantation over the past year for patients of similar weight and procedure duration, Dr. Prieto notes.
The cardiologists also have been testing pediatric applications of a 3-D to 2-D registration technology that allows anatomic structures from a prior cardiac MRI or CT to be superimposed over fluoroscopy. This technology facilitates access to a desired structure ‒ e.g., a collateral vessel, pulmonary artery branch or pulmonary vein ‒ by providing a road map visible on fluoroscopy. The expected results are shorter procedure times with decreased radiation exposure and reduced use of contrast agents.
Rotational angiography capability in the cath lab improves the diagnostic quality of a procedure and allows the cardiologist to select the best angiographic angle for a given intervention more accurately. “From a 3-D data set, it is possible to register the location of a vessel on fluoroscopy, which decreases the time and radiation needed to access a desired structure,” explains Dr. Prieto.
Pediatric electrophysiologist Peter Aziz, MD, views intracardiac electrical tracings during an atrial arrhythmia episode using the 3-D electroanatomic navigation system.
A 3-D map of the atrium from the 3-D electroanatomic navigation system.
At the same time, a novel use of a 3-D electroanatomic navigation system has enabled Cleveland Clinic Children’s electrophysiologists to curb radiation exposure during catheter ablation. Major cardiac structures are mapped and used as reference points for tracking the location of the ablation with magnets. Though the navigation system itself is not new, the application of this technology to reduce radiation exposure in the electrophysiology lab is an exciting adaptation.
The system allows most right heart ablations to be performed without fluoroscopy. When an arrhythmia is generated on the left side of the heart, fluoroscopy is required to guide the transseptal puncture, but the remainder of the procedure can be performed without fluoroscopy.
The system’s utility was assessed in a recent analysis of pediatric patients who underwent limited fluoroscopic 3-D electroanatomic mapping for catheter ablation for supraventricular tachyarrhythmias at Cleveland Clinic Children’s. These patients’ mean procedure time did not differ significantly from that of age-matched controls who underwent the same procedure under fluoroscopic guidance, and procedural success was equivalent between the two groups. However, mean fluoroscopy time was markedly lower in the 3-D mapping group (5.1 minutes) compared with the control group (35.4 minutes). Sixty percent of patients in the 3-D mapping group required no fluoroscopy at all.
“The more quickly we adopt these techniques and technologies, the more quickly we can reduce and eliminate radiation exposure in our young patients,” says Dr. Aziz.”
Top photo: Lourdes Prieto, MD (center) and colleagues using the Artis Q.zen angiography system in the new pediatric catheterization lab.