Techniques to Lower Radiation Dose in TAVR Feasible

In patients undergoing TAVR, simple methods can be used to cut radiation dose by more than 25% without adversely impacting outcomes or how the procedure is carried out in the cath lab, according a single-center study published online April 24, 2015, in Catheterization and Cardiovascular Interventions. 

Researchers led by Mark S. Spence, MD, of Royal Victoria Hospital (Belfast, Northern Ireland), looked at data on radiation usage in 72 consecutive patients (median age 83 years; 36.1% men) who underwent TAVR at their institution over an 11-month period. TAVR was performed using standard image acquisition settings in 36 patients and modified settings in the other 36 patients. The modifications consisted of reducing fluoroscopy settings from a 15 to 3.75-7.5 pulse-progressive fluoroscopy and reducing cine-acquisition settings from 15 to 3.75-7.5 frames per second.   

The majority of cases in each group (86%) were performed via femoral access. Successful vascular access was achieved in all patients, with 2 patients in the standard group requiring a valve-in-valve deployment because of aortic regurgitation.  

Same Procedure, Less Exposure

Overall, the mean STS mortality risk score was similar between the standard and modified groups (10.8 vs 11.6; P = .43), as was the logistic EuroSCORE (21.3 vs 24.6; P = .32). 

Median radiation dose was 27% lower in cases using the modified settings compared with the standard settings. No differences were observed between groups for screening time, procedure length, or amount of contrast used (table 1). Results were similar in the smaller groups of patients who underwent TAVR via the subclavian access route.  

In comparison, the mean radiation dose and screening time of 40 PCI procedures performed in the same cath lab during the same time period were 94 Gy·cm² and 10.6 minutes, respectively. 

At 30 days, there were no cases of procedural death or radiation burns in either TAVR group. Additionally, no major bleeding episodes or stroke occurred. Minor vascular complications, consisting of hematoma or pseudoaneurysm requiring manual compression, were seen in 2 patients treated with standard settings and 1 treated with modified settings.  

Simple, Flexible Approach

According to Dr. Spence and colleagues, limited published data exist with regard to radiation exposure to patients and the cath lab team during TAVR.

“Recently published data, consistent with our findings, suggests that the radiation exposure to [the] patient is within a range comparable to interventional coronary procedures,” they write. “Nevertheless, the radiation exposure to the interventional team and the patient during TAVI is considerable.”

The modified approach used in the study is now standard practice at their institution, the researchers explain, adding that they “change to [standard settings] if required, [such as] for positioning and deployment of the valve, to avoid any compromise in image quality while achieving the ALARA [as low as reasonably achievable] objective.” 

However, Dr. Spence and colleagues acknowledge that the study is limited by the small number of patients and the use of data from a single center. Additionally, they note that the calibration of the instruments over the study period may have had a minor impact on the radiation doses. 

Even so, “it adds to the currently limited data available on radiation exposure during TAVI,” they write. “Given that TAVI has now become the established procedure and the case volume continues to rise rapidly, simple measures to reduce radiation dose have never been more pertinent.” 

A Misguided Concern?

But in an email with TCTMD, Matthew J. Budoff, MD, of Harbor-UCLA Medical Center (Torrance, CA), said that while radiation exposure remains a significant concern for younger patients, it is much less so for those undergoing TAVR.  

“It has been well documented that medical radiation may lead to increased risk of cancer 20 years later, but that implies that the patient has a life expectancy of 20 years, which by definition, [cannot be the case] if they are getting TAVR,” he said.  

Dr. Budoff cited a 2007 study in the Journal of the American Medical Association showing that, as patients age, their risk of developing radiation-related future cancers decreases.  

“Thus, while a 27% reduction in radiation is always welcome, it is probably not the area or population that we would be most interested in,” he noted. 

Source: 
Sharma D, Ramsewak A, O’Conaire S, et al. Reducing radiation exposure during transcatheter aortic valve implantation (TAVI). Catheter Cardiovasc Interv. 2015;Epub ahead of print. 

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