interventional cardiovascular procedures result in considerable radiation doses to patients due to prolonged fluoroscopy exposure times.1 ) however , it is believed that the radiological risk to patients is lower than that of radiofrequency catheter ablation ( rfca ) for the treatment of arrhythmias . the rfca procedure frequently requires more radiation exposure to patients than other interventional procedures in the cardiology field.2 ) one of the severe but easily overlooked acute complications of radiation exposure is radiation - induced dermatitis ( rid ) . early skin changes in rid include erythema , blister formation , epidermal desquamation , and acute ulceration . late or chronic skin changes consist of hypo- or hyperpigmentation , telangiectasia , cutaneous induration , recurrent erosions , severe ulceration , and scarring.3 ) these skin changes can resemble many other dermatologic conditions , which can delay the definitive diagnosis of rid.4 ) furthermore , as skin lesions can develop over a period of days to weeks,5)6)7)8 ) the diagnosis may be missed without the clinician 's awareness . because rfca is usually performed with fixed angle radiation over a period of hours , rid can occur on predictable skin areas . however , the degree of radiation exposure in fluoroscopy patients during rfca depends on the fluoroscopy machine and whether it is single plane or biplane . it is also influenced by patient age , sex , as well as individual patient susceptibilities . furthermore , because rid is rare , its incidence , clinical , and pathologic features are not known well . few reports have measured the radiation exposure to patients during rfca ( table 1).5)6)7)8)9)10)11 ) in the present study , we analyzed rid incidence and characteristics for patients who underwent rfca . a total of 1347 consecutive patients who underwent rfca procedures between 2000 to 2011 for any indication and were evaluated for dermatologic complications following rfca were screened . each of the 1347 patients routinely visited the arrhythmia clinic 1 month after rfca and reported complications to the physicians . rfca procedures were performed at a single center by three independent expert electrophysiologists using the same fluoroscopy machine ( integris bh 5000 bi - plane system ; philips medical systems , amsterdam , the netherlands ) . the routine baseline settings of the biplane fluoroscopy angle were(right anterior oblique ( rao ) of 30 degrees and left anterior oblique ( lao ) of 60 degrees . of the 1347 patients , a total of 894 patients had exact fluoroscopy time data available . patients who complained of skin problems at the 1-month follow - up were retrospectively reviewed . an expert dermatologist re - diagnosed skin lesions based on clinical data including medical photos or medical descriptions . lesions were classified into three groups : ( 1 ) most likely rid , ( 2 ) probable rid , and ( 3 ) possible rid . patients in the ' most likely ' rid or ' probable ' rid groups comprised the rid group . we used chi ( )-square tests to compare characteristics among patients , the fisher 's exact tests for categorical covariates , and the student 's t - tests for continuous covariates . for the risk factor ( univariate / multivariate ) analysis , we used binary logistic regression analysis . a receiver operator characteristic curve was used to determine the cutoff value of fluoroscopy time and body mass index ( bmi ) for rid . we selected the appropriate cutoff value which had high values for both sensitivity and specificity , using the youden 's index ( sensitivity+specificity 1 ) . chicago , il , usa ) . the category free net reclassification improvement ( nri ) and integrated discrimination improvement ( idi ) were calculated with r v.3.02 ( https://www.r-project.org/ ) ) which is available as free software under the terms of the free software foundation 's gnu general public license in source code form . a total of 1347 consecutive patients who underwent rfca procedures between 2000 to 2011 for any indication and were evaluated for dermatologic complications following rfca were screened . each of the 1347 patients routinely visited the arrhythmia clinic 1 month after rfca and reported complications to the physicians . rfca procedures were performed at a single center by three independent expert electrophysiologists using the same fluoroscopy machine ( integris bh 5000 bi - plane system ; philips medical systems , amsterdam , the netherlands ) . the routine baseline settings of the biplane fluoroscopy angle were(right anterior oblique ( rao ) of 30 degrees and left anterior oblique ( lao ) of 60 degrees . of the 1347 patients , a total of 894 patients had exact fluoroscopy time data available . patients who complained of skin problems at the 1-month follow - up were retrospectively reviewed . an expert dermatologist re - diagnosed skin lesions based on clinical data including medical photos or medical descriptions . lesions were classified into three groups : ( 1 ) most likely rid , ( 2 ) probable rid , and ( 3 ) possible rid . patients in the ' most likely ' rid or ' probable ' rid groups comprised the rid group . patients without any skin complications comprised the normal group . we used chi ( )-square tests to compare characteristics among patients , the fisher 's exact tests for categorical covariates , and the student 's t - tests for continuous covariates . for the risk factor ( univariate / multivariate ) analysis , we used binary logistic regression analysis . a receiver operator characteristic curve was used to determine the cutoff value of fluoroscopy time and body mass index ( bmi ) for rid . we selected the appropriate cutoff value which had high values for both sensitivity and specificity , using the youden 's index ( sensitivity+specificity 1 ) . the category free net reclassification improvement ( nri ) and integrated discrimination improvement ( idi ) were calculated with r v.3.02 ( https://www.r-project.org/ ) ) which is available as free software under the terms of the free software foundation 's gnu general public license in source code form . of the 1347 patients who underwent rfca , 12 patients who complained of skin problems within 1 month ( 0.89% ) . nine patients had sufficient medical photos to review , and seven patients had skin biopsy data . of these , six patients were classified as ' most likely ' having rid , four patients having ' probable ' rid , while one patient had possible dermatitis and another had a lesion that could not be re - evaluated due to the lack of sufficient medical data needed for re - diagnosis . detailed medical data of patients with probable rid are also listed in table 2 ( patients 7 - 10 ) . of these , , the skin lesions did not improve without medical or surgical treatment and were vulnerable to minor trauma . because patients were exposed at a fixed angle , all patients in the rid group had lesions on the back of the right thorax and posteriolateral aspect of the right proximal arm . seven cases improved with medical treatment alone , but three cases required surgical intervention . in table 3 , we compare the 10 patients in the rid group with the 1335 normal group patients . the mean body weight and body mass indices ( bmis ) of the rid and normal groups were 29.3 and 23.9 , respectively ( p<0.001 ) . body surface area ( bsa ) was also significantly higher in the rid group ( p=0.006 ) . age , sex , or past medical history did not affect the incidence of rid . in univariate analyses , bmi ( p<0.001 ) , bsa ( p=0.001 ) , fluoroscopy time ( p<0.001 ) , and repeated rfca ( p=0.001 ) were significant risk factors for rid . age , sex , indication for rfca , or previous history did not correlate with rid . in multivariate analyses including bmi , bsa , fluoroscopy time , and repeated rfca , bmi ( p=0.016 ) , fluoroscopy time ( p=0.001 ) , and repeated rfca ( p=0.006 ) were significant risk factors for rid . 2 , the bmi cutoff was 26 kg / m ( area under curve [ auc ] 0.903 , p=0.001 ; sensitivity , 100% ; specificity , 74% ) and fluoroscopy time cutoff value was 115 min ( auc 0.953 , p<0.001 ; sensitivity , 100% ; specificity , 91% ) . the fluoroscopy time added on bmi did not show an additional prognostic power despite the greatest area under curve 0.980 ( p<0.001 ) , as measured by the category free nri ( p=0.39 ) and idi ( p=0.95 ) . among 894 patients with exact fluoroscopy times , the mean estimated radiation doses of patients with or without rid were 25.14.6 vs. 6.87.3 gy , respectively ( p<0.001 ) . assuming that the radiation dose as obtained from the medical records is 0.147 - 0.375 gy per minute , exposure time > 115 minute can be calculated as total exposure dose of 1743 gy . among 894 patients with exact fluoroscopic time information , we further analyzed 41 patients with a bmi > 26 kg / m and fluoroscopy times > 115 minutes . of the 35 patients without complications , 29 cases ( 82.9% ) underwent single - plane fluoroscopy because a 3-d mapping system was used . the remaining 6 patients without rid and 6 patients with rid were treated with biplane fluoroscopy . of the 1347 patients who underwent rfca , 12 patients who complained of skin problems within 1 month ( 0.89% ) . nine patients had sufficient medical photos to review , and seven patients had skin biopsy data . of these , six patients were classified as ' most likely ' having rid , four patients having ' probable ' rid , while one patient had possible dermatitis and another had a lesion that could not be re - evaluated due to the lack of sufficient medical data needed for re - diagnosis . detailed medical data of patients with probable rid are also listed in table 2 ( patients 7 - 10 ) . of these , in 10 patients with rid , the skin lesions did not improve without medical or surgical treatment and were vulnerable to minor trauma . because patients were exposed at a fixed angle , all patients in the rid group had lesions on the back of the right thorax and posteriolateral aspect of the right proximal arm . seven cases improved with medical treatment alone , but three cases required surgical intervention . in table 3 , we compare the 10 patients in the rid group with the 1335 normal group patients . the mean body weight and body mass indices ( bmis ) of the rid and normal groups body surface area ( bsa ) was also significantly higher in the rid group ( p=0.006 ) . age , sex , or past medical history did not affect the incidence of rid . in univariate analyses , bmi ( p<0.001 ) , bsa ( p=0.001 ) , fluoroscopy time ( p<0.001 ) , and repeated rfca ( p=0.001 ) were significant risk factors for rid . age , sex , indication for rfca , or previous history did not correlate with rid . in multivariate analyses including bmi , bsa , fluoroscopy time , and repeated rfca , bmi ( p=0.016 ) , fluoroscopy time ( p=0.001 ) , and repeated rfca ( p=0.006 ) were significant risk factors for rid . the detailed data is described in table 4 . based on the results of the roa curve in fig . 2 , the bmi cutoff was 26 kg / m ( area under curve [ auc ] 0.903 , p=0.001 ; sensitivity , 100% ; specificity , 74% ) and fluoroscopy time cutoff value was 115 min ( auc 0.953 , p<0.001 ; sensitivity , 100% ; specificity , 91% ) . the fluoroscopy time added on bmi did not show an additional prognostic power despite the greatest area under curve 0.980 ( p<0.001 ) , as measured by the category free nri ( p=0.39 ) and idi ( p=0.95 ) . among 894 patients with exact fluoroscopy times , the mean estimated radiation doses of patients with or without rid were 25.14.6 vs. 6.87.3 gy , respectively ( p<0.001 ) . assuming that the radiation dose as obtained from the medical records is 0.147 - 0.375 gy per minute , exposure time > 115 minute can be calculated as total exposure dose of 1743 gy . among 894 patients with exact fluoroscopic time information , we further analyzed 41 patients with a bmi > 26 kg / m and fluoroscopy times > 115 minutes . of the 35 patients without complications , 29 cases ( 82.9% ) underwent single - plane fluoroscopy because a 3-d mapping system was used . the remaining 6 patients without rid and 6 patients with rid were treated with biplane fluoroscopy . this is the first study with large - scale data to report the rid incidence following rfca . the findings in this report highlight the importance of minimizing the radiation dose in individual patients to avoid catastrophic dermatologic complications . physicians should pay special attention to patients with high bmis ( over 26 kg / m ) and when fluoroscopy times are longer than approximately 2 hours . according to previous studies,12 ) acute , dose - dependent skin effects of beta - radiation are as follows : erythema from 6 gy ; moist desquamation from 18 gy , ulceration with slow healing at 24 gy , and ischemic dermal necrosis from 18 gy . in daily practice , the thresholds vary by radiation source and each individual , and determining the exact dose given to a patient is not an easy task . of 894 patients with exact fluoroscopy times , assuming that the radiation dose is 0.147 - 0.375 gy per minute , the cutoff exposure time > 115 minute from our result can be calculated as the total exposure dose of 1743 gy , which correlates with the previous known cutoff value of radiation - induced severe dermatitis . patients receiving rfca are typically exposed to fixed angle radiation for an extended period of time . although fluoroscopy - induced skin injuries are rare,13 ) physicians on occasion overlook this preventable but severe skin complication . in the present study , rid ranged in severity from erythema to tissue necrosis requiring skin graft surgery.14 ) radiation can penetrate the human body but is rapidly attenuated by the tissues . therefore , the maximum radiation dose accumulates in the skin at the point of entrance.15 ) in our patients , the sites of injury were the right arm and back , which is very distinct in rid following fixed angle rfca . as described , we routinely use fixed angle fluoroscopy with a rao of 30 degrees and lao of 60 degrees . the radiation generator with lao of 60 degrees is usually very close to the right arm of a patient , which is a common site of rid , particularly for patients with a high bmi ( fig . therefore , we recommend adjusting the radiation projection angle ( e.g. , adjust lao angle from 60 degrees to 30 degrees ) to prevent rid in patients with high bmis and long procedure times ( fig . x - ray penetration through thicker body masses usually requires higher radiation doses . in obese patients with high bmis , radiation doses can be several times higher compared to patients with lower bmis . in general , current fluoroscopic equipment automatically adjusts the radiation dose to achieve a certain level of resolution on the image intensifier , and the operator may not be aware of how much radiation the patient is receiving during the procedure . this can result in rid , which is most often reported in obese patients.6)7)16 ) in the present study , we found that rid is highly predictable in obese patients with long procedure times . the roc curve showed that the auc of both bmi and fluoroscopy time were greater than 0.90 . although integration of these two factors did not improve the predictive power , the auc of the integration curve was the greatest . the reduced image quality in overweight patients may increase the technical difficulty of the procedure , potentially prolonging procedure times and , thus , requiring greater radiation input . accordingly , in planning rfca , operators should take into account the patient 's bmi and be prepared to adjust their approach accordingly . one limitation of this retrospective study is the lack of exact fluoroscopy times and/or radiation doses for 453 patients ( 33.7% ) . as there were only 10 rids among 1347 patients , weak statistical power is an additional limitation to this study . we can not determine that the cutoff value presented is an absolute number , as values can be alteredoin future studies . based on these findings , the authors proposg that with increasing bmi and fluoroscopy time , greater concern should be given to the increased likelihood of ra diation dermatitis . patients with a high bmi had a higher risk of developing rid with increased exposure times or repeated rfca using biplane fluoroscopy . preventive measures , such as adjusting the projection angle , reducing the radiation dose , positioning the radiation generator farther from patients ' skin , and careful observation of skin complications during follow - up , should be implemented in these patients . patients with a high bmi had a higher risk of developing rid with increased exposure times or repeated rfca using biplane fluoroscopy . preventive measures , such as adjusting the projection angle , reducing the radiation dose , positioning the radiation generator farther from patients ' skin , and careful observation of skin complications during follow - up , should be implemented in these patients .
background and objectivesradiofrequency catheter ablation ( rfca ) exposes patients to fixed angle radiation for extended periods of time . 
 we investigated the incidence and characteristics of radiation - induced dermatitis ( rid ) associated with rfca.subjects and methodswe screened 1347 consecutive patients from 2000 to 2011 who underwent rfca for any indication and reviewed patients with dermatologic issues at the 1-month follow - up . 
 skin lesions were classified into three groups : most likely rid , probable rid , and possible rid.resultsof the 1347 enrolled patients , 12 ( 0.89% ) experienced dermatologic issues within 1 month after rfca , including six patients ( 0.45% ) clinically classified as ' most likely rid ' and four patients ( 0.30% ) with ' probable rid ' . 
 ten patients , including most likely rid or probable rid patients , developed skin lesions on the right back and upper arm . 
 skin lesions did not improve without meticulous treatment , and three cases required surgical intervention . 
 we compared the rid group to the remaining 1335 patients ( normal group ) . 
 the mean body mass indices ( bmis ) of the rid and normal groups were 29.3 and 23.9 kg / m2 , respectively ( p<0.001 ) . 
 radiation exposure times were longer in the rid group ( 18031.0 vs. 4749.9 minutes , p<0.001 ) . 
 we further analyzed 44 patients ( 6 rid cases and 38 normal patients ) that had bmis > 26 kg / m2 and exposure times > 115 minutes based on receiver operator characteristic curve analyses . among the 35 patients without rid 
 , 29 patients ( 82.9% ) did not use biplane fluoroscopy.conclusionspatients with high bmis have a higher risk of developing severe rid with increasing fluoroscopy times using biplane fluoroscopy .