human
***task***
the task is to summarize an input biomedical literature in six sentences

***input***
the input is a biomedical literature

***output***
the output is the summary of an input biomedical literature in six sentences

***documentation***

***examples***

input: with expanding indications for cardiovascular implantable electronic devices ( cieds ) [ bradycardia pacemakers ( pms ) , implantable cardioverter defibrillators ( icds ) , and cardiac resynchronization therapeutic devices with pacing only ( crt - p ) and defibrillator ( crt - d ) ] , the number of eligible recipients has increased significantly . pocket hematoma is an infrequent complication associated with the cied , with an incidence rate ranging from 2 % to 5 % , , accounting for 14 % 17 % of early reoperations . , pocket hematoma is associated with localized pain , longer hospital stays , the risk of reoperations and an increased possibility of infection . , the effect of antiplatelet and anticoagulation therapy on the formation of pocket hematoma has been widely researched . , , previous studies have shown that complication rates increase with complex devices , including icds and crts . furthermore , it has also been reported that chronic kidney disease is an independent risk factor for pocket hematoma formation . , research studies have also suggested that the patients ' left ventricular function did not affect the formation of pocket hematoma , unlike surgical experience . , previous studies have demonstrated that a lower body mass index ( bmi ) was associated with a higher incidence of post - cied procedural complications . however , the relationship between bmi and the development of pocket hematoma has not been comprehensively studied . the aim of this study is to evaluate the impact of bmi on the incidence of pocket hematoma . we conducted a retrospective analysis of patients receiving procedures with cieds using data from the department of cardiology at the chinese pla general hospital between 2008 and 2012 . this study retrospectively reviewed 990 consecutive procedures involving cieds at the department of cardiology , chinese pla general hospital , between 2008 and 2012 . of these , patients who were not followed for three months or died from causes unrelated to their operations within the first three months were excluded , resulting in 972 procedures available for analysis . the indications for operations were based on the prevalent international guidelines , with the surgical strategy remaining unchanged during the period of the study . puncture of the subclavian vein was used under local anesthesia in almost all of the patients except for two cases that received cephalic vein cut down instead . a course of prophylactic antibiotic treatment with either penicillin or a first generation cephalosporin was started 0.52 h prior to the implantation until the third day after the procedure . we stopped any unnecessary medication which may cause hematoma , such as aspirin , warfarin , plavix , etc . severe pocket hematoma was diagnosed as palpable swelling of the pocket causing pain and prolonged hospitalization ( i.e. , 1 day than the scheduled hospital discharge ) , whether or not accompanied by anticoagulation treatment cease , reoperation , evacuation , or blood transfusion . according to recommendations of appropriate body - mass index for asian populations and its implications for policy and intervention strategies , the cut - off point ( bmi = 23 kg / m ) was chosen as the public health action point for many asian populations . therefore , the patients were grouped into two categories according to their baseline bmi value : bmi 23 kg / m and 23 kg / m . renal insufficiency was defined as a glomerular filtration rate ( gfr ) 60 ml / min per 1.73 m. the gfr was calculated using a modification of the diet in renal disease study equation . all the patients had their wounds assessed daily by a cardiologist or an experienced cardiology trainee . patients were discharged and followed for three months after the procedure at the implant center . all pocket hematoma cases were treated with aggressive external compression and / or needle drainage . using this approach , the researchers retrospectively reviewed the patient files for selected clinical and procedural characteristics that might be related to severe hematoma . the clinical variables included age , gender , bmi , diabetes , hypertension , atrial fibrillation , past history of myocardial infarction , coronary artery disease , renal insufficiency , platelet count , international normalized ratio ( inr ) , heart failure , left ventricular ejection fraction ( lvef ) , and the use of antiplatelet ( aspirin or clopidogrel ) or anticoagulation therapy ( warfarin or low - molecular weight heparin ) . the procedural variables also included the type of implant device and the implanter 's level of experience ( cardiologist or trainee ) . statistical analysis was performed using spss version 10.0 ( chicago , il , usa ) . categorical variables were represented by frequencies , which were compared by test or fisher 's exact test as appropriate . univariate and multivariate logistic regressions were done with stepwise procedures to construct a final best fit logistic regression model to determine the predictors in the development of the pocket hematoma . this method specifies the significance level at p 0.25 for entering and exiting an explanatory variable in the stepwise model . potential predictors with p 0.05 on univariate analysis were included in the multiple regression model using a stepwise approach , and predictors with p 0.05 in the multivariable model were retained . log - rank analysis was used to determine the influence of pocket hematoma on hospital stay . this study retrospectively reviewed 990 consecutive procedures involving cieds at the department of cardiology , chinese pla general hospital , between 2008 and 2012 . of these , patients who were not followed for three months or died from causes unrelated to their operations within the first three months were excluded , resulting in 972 procedures available for analysis . the indications for operations were based on the prevalent international guidelines , with the surgical strategy remaining unchanged during the period of the study . puncture of the subclavian vein was used under local anesthesia in almost all of the patients except for two cases that received cephalic vein cut down instead . a course of prophylactic antibiotic treatment with either penicillin or a first generation cephalosporin was started 0.52 h prior to the implantation until the third day after the procedure . we stopped any unnecessary medication which may cause hematoma , such as aspirin , warfarin , plavix , etc . severe pocket hematoma was diagnosed as palpable swelling of the pocket causing pain and prolonged hospitalization ( i.e. , 1 day than the scheduled hospital discharge ) , whether or not accompanied by anticoagulation treatment cease , reoperation , evacuation , or blood transfusion . according to recommendations of appropriate body - mass index for asian populations and its implications for policy and intervention strategies , the cut - off point ( bmi = 23 kg / m ) was chosen as the public health action point for many asian populations . therefore , the patients were grouped into two categories according to their baseline bmi value : bmi 23 kg / m and 23 kg / m . renal insufficiency was defined as a glomerular filtration rate ( gfr ) 60 ml / min per 1.73 m. the gfr was calculated using a modification of the diet in renal disease study equation . all the patients had their wounds assessed daily by a cardiologist or an experienced cardiology trainee . patients were discharged and followed for three months after the procedure at the implant center . all pocket hematoma cases were treated with aggressive external compression and / or needle drainage . using this approach , the researchers retrospectively reviewed the patient files for selected clinical and procedural characteristics that might be related to severe hematoma . the clinical variables included age , gender , bmi , diabetes , hypertension , atrial fibrillation , past history of myocardial infarction , coronary artery disease , renal insufficiency , platelet count , international normalized ratio ( inr ) , heart failure , left ventricular ejection fraction ( lvef ) , and the use of antiplatelet ( aspirin or clopidogrel ) or anticoagulation therapy ( warfarin or low - molecular weight heparin ) . the procedural variables also included the type of implant device and the implanter 's level of experience ( cardiologist or trainee ) . statistical analysis was performed using spss version 10.0 ( chicago , il , usa ) . categorical variables were represented by frequencies , which were compared by test or fisher 's exact test as appropriate . univariate and multivariate logistic regressions were done with stepwise procedures to construct a final best fit logistic regression model to determine the predictors in the development of the pocket hematoma . this method specifies the significance level at p 0.25 for entering and exiting an explanatory variable in the stepwise model . potential predictors with p 0.05 on univariate analysis were included in the multiple regression model using a stepwise approach , and predictors with p 0.05 in the multivariable model were retained . log - rank analysis was used to determine the influence of pocket hematoma on hospital stay . a total of 972 cieds procedures ( 69.713.3 years , male 68 % ) were enrolled in the study . eight hundred and fifty four ( 87.9 % ) underwent new implantations , with the remaining 12.0 % undergoing replacement . one hundred and twenty eight ( 13.2 % ) were on aspirin , fifteen ( 1.5 % ) were on clopidogrel and ten ( 1.0 % ) were on both . only three of the patients were on bridging subcutaneous enoxaparin and ten were on therapeutic warfarin therapy . the mean glomerular filtration rate ( gfr ) of the study population was 82.323.2 ml / min per 1.73 m. of all the procedures , 584 ( 60.1 % ) were performed by a cardiologist and 388 ( 40.0 % ) by a trainee . the hematoma rate in bradycardia pacemaker implantations was 5 of 452 ( 1.1 % ) in procedures performed by cardiologists and 7 of 388 ( 1.8 % ) of implantations carried out by trainees ( p 0.05 ) . the hematoma rate was 10 out of 132 ( 7.6 % ) in icd and crt device implantations and 5 out of 452 ( 1.1 % ) in bradycardia pm implantation when the devices were implanted by cardiologists ( p 0.01 ) . in total , 2.2 % ( n = 22 ) of the population developed severe pocket hematoma , which was diagnosed at the mean time of 5.58.5 days ( minimum one days and maximum 43 days ) and needed re - intervention . ninety one percent of hematoma cases ( n = 20 ) developed within the first week of the procedure . eight ( 36 % ) patients with pocket hematoma were on aspirin and three patients were on both aspirin and clopidogrel . log - rank analysis revealed that patients with hematoma showed significantly longer post - procedure hospital stays ( 4.04.2 days vs. 17.68.4 days , p 0.001 ) compared with patients without hematoma . baseline clinical characteristics , the types of devices used , and the relevant rates of hematoma are listed in table 1 . patients were grouped into two categories according to the baseline bmi value : bmi 23.0 kg / m ( n = 338 , 34.8 % ) and bmi 23.0 kg / m ( n = 634 , 65.2 % ) . compared with patients in the bmi 23.0 kg / m category , patients in the bmi 23.0 kg / m category showed a higher prevalence of hypertension , and significantly lower rate of hematoma development ( all p 0.001 ) . no differences in the two categories were present in the age , gender , number of patients afflicted with diabetes , atrial fibrillation , history of myocardial infarction , coronary artery disease , renal insufficiency , platelet count , inr , new york heart association ( nyha ) heart failure function class and device type . of all the patients , 16.1 % ( n = 156 ) were associated with renal insufficiency . of these patients ,10.2 % ( n = 16 ) showed severe hematoma . among patients undergoing dual antiplatelet therapy with aspirin and clopidogrel , 3 out of 15 ( 33.3 % ) of them developed severe hematoma . in total , 13 % ( n = 126 ) of all patients underwent an icd or crt procedure , with the remaining 87.0 % undergoing bradycardia pacemaker implantation ( single or dual - chamber pacemaker ) . almost 9 % ( n = 11 ) of patients underwent the icd or crt procedure and 1.3 % ( n = 11 ) of patients were treated with bradycardia pm developed severe pocket hematoma ( p 0.001 ) . pocket hematoma added 320 additional hospital treatment days , accounting for a mean extension in hospital stay of 14.5 day / patient . pocket hematoma was treated with aggressive external compression and / or needle drainage . using this approach , the univariate analysis showed that eight predictors were associated with higher incidence of severe pocket hematoma warranting re - intervention ( table 3 ) . after adjusting for confounders , the following factors ; bmi 23.0 kg / m , dual antiplatelet therapy , complex devices , and renal insufficiency , were found to be independent predictors of severe pocket hematoma in multivariate regression analysis ( table 4 , figure 1 ) . atrial fibrillation is defined as any previous episode of atrial fibrillation ; complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. bmi : body mass index ; cad : coronary artery disease ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; inr : international normalized ratio ; lvef : left ventricular ejection fraction ; mi : myocardial infarction . atrial fibrillation is defined as any previous episode of atrial fibrillation ; complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. bmi : body mass index ; cad : coronary artery disease ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; inr : international normalized ratio ; lvef : left ventricular ejection fraction . complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. ap : antiplatelet ; bmi : body mass index ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; inr : international normalized ratio ; lvef : left ventricular ejection fraction . in multivariate regression analysis , after adjusting for past histories of heart failure , renal insufficiency , dual ap therapy , device replacement and device complexity , lower bmi ( 23.0 kg / m ) was determined to be a risk factor for pocket hematoma formation ( or : 0.32 ; 95 % ci : 0.120.84 ; p = 0.02 ) . an increase of 1.0 kg / m in bmi levels was associated with lower incidence of hematoma formation ( or : 0.84 ; 95 % ci : 0.740.95 ; p = 0.006 ) . complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. ap : antiplatelet ; bmi : body mass index ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; mi : myocardial infarction . renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. bmi : body mass index ; mi : myocardial infarction ; , a significant increase in cieds implantations will result in a corresponding increase in the number of reported complications associated with the procedure . the pocket hematoma is associated with local discomfort , prolonged hospital stays and an increased risk of re - intervention and related risk of infection . in our study , we observed that dual antiplatelet therapy , complex devices and renal insufficiency are independent predictors of pocket hematoma , which need re - intervention . the study demonstrated that patients with hematoma endured a longer hospital stay and a higher infection rate , compared to patients without hematoma . the above findings are in accordance with the results from previous studies. , a recent study demonstrated that device replacements are associated with a significant risk of complications . however , this study illustrated that device replacement did not increase hematoma rates compared with patients who received device implantation in the multivariate analysis . this is probably due to the small sample size or the comparatively reduced dosage of antiplatelet or anticoagulation therapy . previous studies have shown that a lower bmi was associated with a higher incidence of post - cied procedure complications . our study demonstrates that a bmi of 23.0 kg / m was associated with development of severe hematoma which needs re - intervention . an increase of 1.0 kg / m in bmi was associated with lower incidence of hematoma formation . the association between a comparatively lower bmi and hematoma formation might be attributed to the thin subcutaneous layer . similarly a hematoma may lead to more severe tension in patients with a lower bmi . a recent prospective study described obesity ( bmi 30 kg / m ) as a protective factor in the development of pocket hematoma . today , most pulse generators are implanted deep inside the adipose tissue and lying on the pectoralis fascia , which obviates dissection of deeper tissues with a shorter operation time . hypothetically , this is less likely with the submuscular approach in healthy vascularized patients . according to knepp 's study , almost 40 % of the cases involving generator - repositioning are due to hematoma . after repositioning , gold , et al . reported that the overall complication rate due to subcutaneous approach was comparable to the submuscular approach . however , patients in the subcutaneous group weighed on an average of 2.8 kg more than those in the submuscular group , and the mean bmi was much higher compared with our study . in patients with a lower bmi , cieds placement in the submuscular plane might be an alternative , to reducing the rate of bleeding . previous studies have suggested that hematoma is more common when done by an individual with a lesser level of implanting experience . however , this was not in accordance with the findings of this study , probably due to the comparatively reduced use of antiplatelet or / and anticoagulant therapy in our study sample . first , because of the small number of outcomes and the retrospective nature of the subgroup analysis , we can not exclude the possibility that the statistical significance is due to the occurrence of a type i error inflation . second , there were fewer patients undergoing antiplatelet or / and anticoagulation therapy in this study compared with other research studies involving pocket hematoma . however , we excluded the influence of oral antiplatelet and anticoagulation therapy when analyzing the effects of bmi . to the best of our knowledge , this study is the first to address the impact of bmi on the development of pocket hematoma . our study demonstrates that a bmi 23.0 kg / m was associated with a higher incidence of pocket hematoma , which needs re - intervention after a cied procedure . the data support that great care must be taken when patients received cieds implantation with a lower bmi .
output:

agent
backgroundpocket hematoma is one of the major complications associated with cardiovascular implantable electronic devices ( cieds ) implantation . the aim of this study is to evaluate the impact of body mass index ( bmi ) on the occurrence of pocket hematoma after cieds implantation.methodsthe study is a retrospective review of 972 patients receiving cieds implantation between 2008 and 2012 in a tertiary hospital.resultstwenty two patients ( 2.2 % ) developed severe pocket hematoma requiring re - intervention . the hematoma rate ( 4.6 % , n = 15 ) of patients with a bmi of < 23 kg / m2 was significantly higher compared with that of patients with a bmi of 23 kg / m2 ( 1.1 % , n = 7 , p < 0.001 ) . in multivariate regression analysis , a bmi < 23.0 kg / m2 may be associated with the development of severe pocket hematoma . an increase of 1.0 kg / m2 in bmi was associated with lower incidence of hematoma formation ( or : 0.84 ; 95 % ci : 0.74 - 0.95 ; p = 0.006 ) . conclusionbmi < 23 kg / m2 was associated with a higher incidence of pocket hematoma , requiring re - intervention . the data support that great care must be taken when patients were with a lower bmi received cieds implantation .
***task***
the task is to summarize an input biomedical literature in six sentences

***input***
the input is a biomedical literature

***output***
the output is the summary of an input biomedical literature in six sentences

***documentation***

***examples***

input: with expanding indications for cardiovascular implantable electronic devices ( cieds ) [ bradycardia pacemakers ( pms ) , implantable cardioverter defibrillators ( icds ) , and cardiac resynchronization therapeutic devices with pacing only ( crt - p ) and defibrillator ( crt - d ) ] , the number of eligible recipients has increased significantly . pocket hematoma is an infrequent complication associated with the cied , with an incidence rate ranging from 2 % to 5 % , , accounting for 14 % 17 % of early reoperations . , pocket hematoma is associated with localized pain , longer hospital stays , the risk of reoperations and an increased possibility of infection . , the effect of antiplatelet and anticoagulation therapy on the formation of pocket hematoma has been widely researched . , , previous studies have shown that complication rates increase with complex devices , including icds and crts . furthermore , it has also been reported that chronic kidney disease is an independent risk factor for pocket hematoma formation . , research studies have also suggested that the patients ' left ventricular function did not affect the formation of pocket hematoma , unlike surgical experience . , previous studies have demonstrated that a lower body mass index ( bmi ) was associated with a higher incidence of post - cied procedural complications . however , the relationship between bmi and the development of pocket hematoma has not been comprehensively studied . the aim of this study is to evaluate the impact of bmi on the incidence of pocket hematoma . we conducted a retrospective analysis of patients receiving procedures with cieds using data from the department of cardiology at the chinese pla general hospital between 2008 and 2012 . this study retrospectively reviewed 990 consecutive procedures involving cieds at the department of cardiology , chinese pla general hospital , between 2008 and 2012 . of these , patients who were not followed for three months or died from causes unrelated to their operations within the first three months were excluded , resulting in 972 procedures available for analysis . the indications for operations were based on the prevalent international guidelines , with the surgical strategy remaining unchanged during the period of the study . puncture of the subclavian vein was used under local anesthesia in almost all of the patients except for two cases that received cephalic vein cut down instead . a course of prophylactic antibiotic treatment with either penicillin or a first generation cephalosporin was started 0.52 h prior to the implantation until the third day after the procedure . we stopped any unnecessary medication which may cause hematoma , such as aspirin , warfarin , plavix , etc . severe pocket hematoma was diagnosed as palpable swelling of the pocket causing pain and prolonged hospitalization ( i.e. , 1 day than the scheduled hospital discharge ) , whether or not accompanied by anticoagulation treatment cease , reoperation , evacuation , or blood transfusion . according to recommendations of appropriate body - mass index for asian populations and its implications for policy and intervention strategies , the cut - off point ( bmi = 23 kg / m ) was chosen as the public health action point for many asian populations . therefore , the patients were grouped into two categories according to their baseline bmi value : bmi 23 kg / m and 23 kg / m . renal insufficiency was defined as a glomerular filtration rate ( gfr ) 60 ml / min per 1.73 m. the gfr was calculated using a modification of the diet in renal disease study equation . all the patients had their wounds assessed daily by a cardiologist or an experienced cardiology trainee . patients were discharged and followed for three months after the procedure at the implant center . all pocket hematoma cases were treated with aggressive external compression and / or needle drainage . using this approach , the researchers retrospectively reviewed the patient files for selected clinical and procedural characteristics that might be related to severe hematoma . the clinical variables included age , gender , bmi , diabetes , hypertension , atrial fibrillation , past history of myocardial infarction , coronary artery disease , renal insufficiency , platelet count , international normalized ratio ( inr ) , heart failure , left ventricular ejection fraction ( lvef ) , and the use of antiplatelet ( aspirin or clopidogrel ) or anticoagulation therapy ( warfarin or low - molecular weight heparin ) . the procedural variables also included the type of implant device and the implanter 's level of experience ( cardiologist or trainee ) . statistical analysis was performed using spss version 10.0 ( chicago , il , usa ) . categorical variables were represented by frequencies , which were compared by test or fisher 's exact test as appropriate . univariate and multivariate logistic regressions were done with stepwise procedures to construct a final best fit logistic regression model to determine the predictors in the development of the pocket hematoma . this method specifies the significance level at p 0.25 for entering and exiting an explanatory variable in the stepwise model . potential predictors with p 0.05 on univariate analysis were included in the multiple regression model using a stepwise approach , and predictors with p 0.05 in the multivariable model were retained . log - rank analysis was used to determine the influence of pocket hematoma on hospital stay . this study retrospectively reviewed 990 consecutive procedures involving cieds at the department of cardiology , chinese pla general hospital , between 2008 and 2012 . of these , patients who were not followed for three months or died from causes unrelated to their operations within the first three months were excluded , resulting in 972 procedures available for analysis . the indications for operations were based on the prevalent international guidelines , with the surgical strategy remaining unchanged during the period of the study . puncture of the subclavian vein was used under local anesthesia in almost all of the patients except for two cases that received cephalic vein cut down instead . a course of prophylactic antibiotic treatment with either penicillin or a first generation cephalosporin was started 0.52 h prior to the implantation until the third day after the procedure . we stopped any unnecessary medication which may cause hematoma , such as aspirin , warfarin , plavix , etc . severe pocket hematoma was diagnosed as palpable swelling of the pocket causing pain and prolonged hospitalization ( i.e. , 1 day than the scheduled hospital discharge ) , whether or not accompanied by anticoagulation treatment cease , reoperation , evacuation , or blood transfusion . according to recommendations of appropriate body - mass index for asian populations and its implications for policy and intervention strategies , the cut - off point ( bmi = 23 kg / m ) was chosen as the public health action point for many asian populations . therefore , the patients were grouped into two categories according to their baseline bmi value : bmi 23 kg / m and 23 kg / m . renal insufficiency was defined as a glomerular filtration rate ( gfr ) 60 ml / min per 1.73 m. the gfr was calculated using a modification of the diet in renal disease study equation . all the patients had their wounds assessed daily by a cardiologist or an experienced cardiology trainee . patients were discharged and followed for three months after the procedure at the implant center . all pocket hematoma cases were treated with aggressive external compression and / or needle drainage . using this approach , the researchers retrospectively reviewed the patient files for selected clinical and procedural characteristics that might be related to severe hematoma . the clinical variables included age , gender , bmi , diabetes , hypertension , atrial fibrillation , past history of myocardial infarction , coronary artery disease , renal insufficiency , platelet count , international normalized ratio ( inr ) , heart failure , left ventricular ejection fraction ( lvef ) , and the use of antiplatelet ( aspirin or clopidogrel ) or anticoagulation therapy ( warfarin or low - molecular weight heparin ) . the procedural variables also included the type of implant device and the implanter 's level of experience ( cardiologist or trainee ) . statistical analysis was performed using spss version 10.0 ( chicago , il , usa ) . categorical variables were represented by frequencies , which were compared by test or fisher 's exact test as appropriate . univariate and multivariate logistic regressions were done with stepwise procedures to construct a final best fit logistic regression model to determine the predictors in the development of the pocket hematoma . this method specifies the significance level at p 0.25 for entering and exiting an explanatory variable in the stepwise model . potential predictors with p 0.05 on univariate analysis were included in the multiple regression model using a stepwise approach , and predictors with p 0.05 in the multivariable model were retained . log - rank analysis was used to determine the influence of pocket hematoma on hospital stay . a total of 972 cieds procedures ( 69.713.3 years , male 68 % ) were enrolled in the study . eight hundred and fifty four ( 87.9 % ) underwent new implantations , with the remaining 12.0 % undergoing replacement . one hundred and twenty eight ( 13.2 % ) were on aspirin , fifteen ( 1.5 % ) were on clopidogrel and ten ( 1.0 % ) were on both . only three of the patients were on bridging subcutaneous enoxaparin and ten were on therapeutic warfarin therapy . the mean glomerular filtration rate ( gfr ) of the study population was 82.323.2 ml / min per 1.73 m. of all the procedures , 584 ( 60.1 % ) were performed by a cardiologist and 388 ( 40.0 % ) by a trainee . the hematoma rate in bradycardia pacemaker implantations was 5 of 452 ( 1.1 % ) in procedures performed by cardiologists and 7 of 388 ( 1.8 % ) of implantations carried out by trainees ( p 0.05 ) . the hematoma rate was 10 out of 132 ( 7.6 % ) in icd and crt device implantations and 5 out of 452 ( 1.1 % ) in bradycardia pm implantation when the devices were implanted by cardiologists ( p 0.01 ) . in total , 2.2 % ( n = 22 ) of the population developed severe pocket hematoma , which was diagnosed at the mean time of 5.58.5 days ( minimum one days and maximum 43 days ) and needed re - intervention . ninety one percent of hematoma cases ( n = 20 ) developed within the first week of the procedure . eight ( 36 % ) patients with pocket hematoma were on aspirin and three patients were on both aspirin and clopidogrel . log - rank analysis revealed that patients with hematoma showed significantly longer post - procedure hospital stays ( 4.04.2 days vs. 17.68.4 days , p 0.001 ) compared with patients without hematoma . baseline clinical characteristics , the types of devices used , and the relevant rates of hematoma are listed in table 1 . patients were grouped into two categories according to the baseline bmi value : bmi 23.0 kg / m ( n = 338 , 34.8 % ) and bmi 23.0 kg / m ( n = 634 , 65.2 % ) . compared with patients in the bmi 23.0 kg / m category , patients in the bmi 23.0 kg / m category showed a higher prevalence of hypertension , and significantly lower rate of hematoma development ( all p 0.001 ) . no differences in the two categories were present in the age , gender , number of patients afflicted with diabetes , atrial fibrillation , history of myocardial infarction , coronary artery disease , renal insufficiency , platelet count , inr , new york heart association ( nyha ) heart failure function class and device type . of all the patients , 16.1 % ( n = 156 ) were associated with renal insufficiency . of these patients ,10.2 % ( n = 16 ) showed severe hematoma . among patients undergoing dual antiplatelet therapy with aspirin and clopidogrel , 3 out of 15 ( 33.3 % ) of them developed severe hematoma . in total , 13 % ( n = 126 ) of all patients underwent an icd or crt procedure , with the remaining 87.0 % undergoing bradycardia pacemaker implantation ( single or dual - chamber pacemaker ) . almost 9 % ( n = 11 ) of patients underwent the icd or crt procedure and 1.3 % ( n = 11 ) of patients were treated with bradycardia pm developed severe pocket hematoma ( p 0.001 ) . pocket hematoma added 320 additional hospital treatment days , accounting for a mean extension in hospital stay of 14.5 day / patient . pocket hematoma was treated with aggressive external compression and / or needle drainage . using this approach , the univariate analysis showed that eight predictors were associated with higher incidence of severe pocket hematoma warranting re - intervention ( table 3 ) . after adjusting for confounders , the following factors ; bmi 23.0 kg / m , dual antiplatelet therapy , complex devices , and renal insufficiency , were found to be independent predictors of severe pocket hematoma in multivariate regression analysis ( table 4 , figure 1 ) . atrial fibrillation is defined as any previous episode of atrial fibrillation ; complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. bmi : body mass index ; cad : coronary artery disease ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; inr : international normalized ratio ; lvef : left ventricular ejection fraction ; mi : myocardial infarction . atrial fibrillation is defined as any previous episode of atrial fibrillation ; complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. bmi : body mass index ; cad : coronary artery disease ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; inr : international normalized ratio ; lvef : left ventricular ejection fraction . complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. ap : antiplatelet ; bmi : body mass index ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; inr : international normalized ratio ; lvef : left ventricular ejection fraction . in multivariate regression analysis , after adjusting for past histories of heart failure , renal insufficiency , dual ap therapy , device replacement and device complexity , lower bmi ( 23.0 kg / m ) was determined to be a risk factor for pocket hematoma formation ( or : 0.32 ; 95 % ci : 0.120.84 ; p = 0.02 ) . an increase of 1.0 kg / m in bmi levels was associated with lower incidence of hematoma formation ( or : 0.84 ; 95 % ci : 0.740.95 ; p = 0.006 ) . complex device is referred to icd or crt - p or crt - d ; renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. ap : antiplatelet ; bmi : body mass index ; crt - d : cardiac resynchronization therapy devices with defibrillator ; crt - p : cardiac resynchronization therapy devices with pacing ; mi : myocardial infarction . renal insufficiency is defined as a glomerular filtration rate 60 ml / min per 1.73 m. bmi : body mass index ; mi : myocardial infarction ; , a significant increase in cieds implantations will result in a corresponding increase in the number of reported complications associated with the procedure . the pocket hematoma is associated with local discomfort , prolonged hospital stays and an increased risk of re - intervention and related risk of infection . in our study , we observed that dual antiplatelet therapy , complex devices and renal insufficiency are independent predictors of pocket hematoma , which need re - intervention . the study demonstrated that patients with hematoma endured a longer hospital stay and a higher infection rate , compared to patients without hematoma . the above findings are in accordance with the results from previous studies. , a recent study demonstrated that device replacements are associated with a significant risk of complications . however , this study illustrated that device replacement did not increase hematoma rates compared with patients who received device implantation in the multivariate analysis . this is probably due to the small sample size or the comparatively reduced dosage of antiplatelet or anticoagulation therapy . previous studies have shown that a lower bmi was associated with a higher incidence of post - cied procedure complications . our study demonstrates that a bmi of 23.0 kg / m was associated with development of severe hematoma which needs re - intervention . an increase of 1.0 kg / m in bmi was associated with lower incidence of hematoma formation . the association between a comparatively lower bmi and hematoma formation might be attributed to the thin subcutaneous layer . similarly a hematoma may lead to more severe tension in patients with a lower bmi . a recent prospective study described obesity ( bmi 30 kg / m ) as a protective factor in the development of pocket hematoma . today , most pulse generators are implanted deep inside the adipose tissue and lying on the pectoralis fascia , which obviates dissection of deeper tissues with a shorter operation time . hypothetically , this is less likely with the submuscular approach in healthy vascularized patients . according to knepp 's study , almost 40 % of the cases involving generator - repositioning are due to hematoma . after repositioning , gold , et al . reported that the overall complication rate due to subcutaneous approach was comparable to the submuscular approach . however , patients in the subcutaneous group weighed on an average of 2.8 kg more than those in the submuscular group , and the mean bmi was much higher compared with our study . in patients with a lower bmi , cieds placement in the submuscular plane might be an alternative , to reducing the rate of bleeding . previous studies have suggested that hematoma is more common when done by an individual with a lesser level of implanting experience . however , this was not in accordance with the findings of this study , probably due to the comparatively reduced use of antiplatelet or / and anticoagulant therapy in our study sample . first , because of the small number of outcomes and the retrospective nature of the subgroup analysis , we can not exclude the possibility that the statistical significance is due to the occurrence of a type i error inflation . second , there were fewer patients undergoing antiplatelet or / and anticoagulation therapy in this study compared with other research studies involving pocket hematoma . however , we excluded the influence of oral antiplatelet and anticoagulation therapy when analyzing the effects of bmi . to the best of our knowledge , this study is the first to address the impact of bmi on the development of pocket hematoma . our study demonstrates that a bmi 23.0 kg / m was associated with a higher incidence of pocket hematoma , which needs re - intervention after a cied procedure . the data support that great care must be taken when patients received cieds implantation with a lower bmi .
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