eligible patients were drawn from 2 truven marketscan databases : commercial claims & encounters and medicare supplemental & coordination of benefits .
large selfinsured employers , health plans , hospitals , and medicare contribute claims data to these databases .
the full population includes 26  million people annually in the commercial data and 4  million people annually in the medicare claims .
the medicare population includes people 65 and older with employersponsored comprehensive hmo coverage through medicare advantage or supplemental coverage through medigap plans .
marketscan data are widely used in health services research to characterize patterns of care.18 , 19 , 20 , 21 compared to the whole us population , the marketscan population is generally younger , more likely to be employed , and thus wealthier .
previous comparisons have shown that marketscan represents the under65 , noncapitated population well.22 this study was deemed not human subjects research by the health care policy compliance office , in accordance with the office of human research administration , harvard longwood medical area policy , and federal regulations [ 45 cfr 46.102(f ) ] .
we matched inpatient and outpatient claims using dates of service to form episodes of care that included any international classification of disease , 9th revision  clinical modification ( icd9cm ) procedure codes or current procedural terminology codes related to the 3 devices of interest .
though we focused primarily on crtp and crtd implants , we identified icd implants to provide context according to overall device utilization .
we limited the sample to adults ( 18  years old ) receiving new implants between 2008 and 2013 by excluding episodes with codes that indicated removals , revisions , and generator changes , and then classified each new implant as icd , crtd , or crtp ( figure  1 ) .
tables s1 and s2 list the specific codes used to select new implants and classify devices .
we required 6  months of continuous enrollment prior to implant in order to measure comorbidities and medications . cohort selection method .
cpt indicates current procedural terminology ; crtd , crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator ; icd9 , international classification of disease , 9th revision .
we measured characteristics of patients heart failure using claims in the 6  months prior to implant .
two of these ( arrhythmias and congestive heart failure ) use codes from the 2013 centers for medicare and medicaid services hierarchical condition categories.23 the other 3 ( atrial fibrillation / flutter , cardiac failure , and conduction disorders ) use small subsets of diagnosis codes , listed in table  s3 .
we also measured charlson index comorbidities in the 6  months prior to implant : cerebrovascular disease , coronary disease , dementia , diabetes mellitus , hiv / aids , kidney disease , liver disease , paralysis , peripheral vascular disease , pulmonary disease , rheumatoid arthritis , and stomach ulcers .
we used the deyo adaptation with several codes that reflect the romano adaptation ; specific icd9cm diagnosis codes are found in table  s3.24 , 25 , 26 we defined medication use as at least 90  days of medication supply in the 6  months prior to implant .
we measured drugs in the following categories : blockers , angiotensinconverting enzyme inhibitors , and angiotensin receptor blockers .
this 90day window prior to implant is consistent with the lower bound of a 3 to 6month course recommended in the 2010 comprehensive heart failure practice guideline27 and used in previous studies.28 specific drug names are found in table  s4 .
we defined optimal medical therapy as use of any blocker combined with any angiotensinconverting enzyme inhibitor or angiotensin receptor blocker .
some individuals in the database lack claims for prescription drugs ( either because they do not have prescription drug coverage or their employer / insurer does not contribute these claims to the data ) .
thus , we restrict our measures of medication use to people with any drug claim in the period ( 75% of all patients ) , a conservative definition of the subpopulation with both prescription drug coverage and available claims .
we summarized patient characteristics by device type using counts and percentages for binary variables , and median , 25th , and 75th percentiles for continuous variables .
we computed standardized mean differences in binary patient characteristics for all pairwise combinations of the 3 devices .
we computed unadjusted implant rates using the entire marketscan population . in our main analyses ,
we combine the commercial and medicare advantage populations . to highlight the differences in clinical characteristics and medications among patients receiving each device , we plot standardized mean differences ( with 95% cis ) in figure  2 .
these are considered substantial when they exceed 0.10 in absolute value.29 
  clinical differences between implant groups .
points ( intervals ) are standardized mean differences ( 95% ci ) for each characteristic .
positive numbers indicate higher prevalence in the device listed first in each panel , measured using the 6  months of claims prior to implant .
ace indicates angiotensinconverting enzyme ; arb , angiotensin receptor blockers ; av , atrioventricular ; crtd , crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator .
to evaluate changes over time and geography in the relative proportions of each device type among new crt implants , we modeled device receipt using year , age quintiles , sex , and all 2 and 3way interactions among them ( ie , a saturated model ) . for the 3way comparison of each device type among all implants , we fit a multinomial model ; for crtp receipt versus crtd , we used a logistic model .
these models produce fitted probabilities of receiving each device type adjusted for age , sex , and year .
we fit a version of the logistic model that also included state fixed effects ; for that model , we excluded 4 states ( north dakota , puerto rico , south dakota , and vermont ) with no crtp implants .
we present results as fitted device percentages ( out of all new implants ) in selected patient subgroups , rather than regression coefficients , for ease of interpretation .
eligible patients were drawn from 2 truven marketscan databases : commercial claims & encounters and medicare supplemental & coordination of benefits .
large selfinsured employers , health plans , hospitals , and medicare contribute claims data to these databases .
the full population includes 26  million people annually in the commercial data and 4  million people annually in the medicare claims .
the medicare population includes people 65 and older with employersponsored comprehensive hmo coverage through medicare advantage or supplemental coverage through medigap plans .
marketscan data are widely used in health services research to characterize patterns of care.18 , 19 , 20 , 21 compared to the whole us population , the marketscan population is generally younger , more likely to be employed , and thus wealthier .
previous comparisons have shown that marketscan represents the under65 , noncapitated population well.22 this study was deemed not human subjects research by the health care policy compliance office , in accordance with the office of human research administration , harvard longwood medical area policy , and federal regulations [ 45 cfr 46.102(f ) ] .
we matched inpatient and outpatient claims using dates of service to form episodes of care that included any international classification of disease , 9th revision  clinical modification ( icd9cm ) procedure codes or current procedural terminology codes related to the 3 devices of interest .
though we focused primarily on crtp and crtd implants , we identified icd implants to provide context according to overall device utilization .
we limited the sample to adults ( 18  years old ) receiving new implants between 2008 and 2013 by excluding episodes with codes that indicated removals , revisions , and generator changes , and then classified each new implant as icd , crtd , or crtp ( figure  1 ) .
tables s1 and s2 list the specific codes used to select new implants and classify devices .
we required 6  months of continuous enrollment prior to implant in order to measure comorbidities and medications .
cpt indicates current procedural terminology ; crtd , crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator ; icd9 , international classification of disease , 9th revision .
we measured characteristics of patients heart failure using claims in the 6  months prior to implant .
two of these ( arrhythmias and congestive heart failure ) use codes from the 2013 centers for medicare and medicaid services hierarchical condition categories.23 the other 3 ( atrial fibrillation / flutter , cardiac failure , and conduction disorders ) use small subsets of diagnosis codes , listed in table  s3 .
we also measured charlson index comorbidities in the 6  months prior to implant : cerebrovascular disease , coronary disease , dementia , diabetes mellitus , hiv / aids , kidney disease , liver disease , paralysis , peripheral vascular disease , pulmonary disease , rheumatoid arthritis , and stomach ulcers .
we used the deyo adaptation with several codes that reflect the romano adaptation ; specific icd9cm diagnosis codes are found in table  s3.24 , 25 , 26 we defined medication use as at least 90  days of medication supply in the 6  months prior to implant .
we measured drugs in the following categories : blockers , angiotensinconverting enzyme inhibitors , and angiotensin receptor blockers .
this 90day window prior to implant is consistent with the lower bound of a 3 to 6month course recommended in the 2010 comprehensive heart failure practice guideline27 and used in previous studies.28 specific drug names are found in table  s4 .
we defined optimal medical therapy as use of any blocker combined with any angiotensinconverting enzyme inhibitor or angiotensin receptor blocker .
some individuals in the database lack claims for prescription drugs ( either because they do not have prescription drug coverage or their employer / insurer does not contribute these claims to the data ) .
thus , we restrict our measures of medication use to people with any drug claim in the period ( 75% of all patients ) , a conservative definition of the subpopulation with both prescription drug coverage and available claims .
we summarized patient characteristics by device type using counts and percentages for binary variables , and median , 25th , and 75th percentiles for continuous variables .
we computed standardized mean differences in binary patient characteristics for all pairwise combinations of the 3 devices .
we computed unadjusted implant rates using the entire marketscan population . in our main analyses ,
we combine the commercial and medicare advantage populations . to highlight the differences in clinical characteristics and medications among patients receiving each device , we plot standardized mean differences ( with 95% cis ) in figure  2 .
these are considered substantial when they exceed 0.10 in absolute value.29 
  clinical differences between implant groups .
points ( intervals ) are standardized mean differences ( 95% ci ) for each characteristic .
positive numbers indicate higher prevalence in the device listed first in each panel , measured using the 6  months of claims prior to implant .
ace indicates angiotensinconverting enzyme ; arb , angiotensin receptor blockers ; av , atrioventricular ; crtd , crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator . to evaluate changes over time and geography in the relative proportions of each device type among new crt implants , we modeled device receipt using year , age quintiles , sex , and all 2 and 3way interactions among them ( ie , a saturated model ) . for the 3way comparison of each device type among all implants ,
we fit a multinomial model ; for crtp receipt versus crtd , we used a logistic model .
these models produce fitted probabilities of receiving each device type adjusted for age , sex , and year .
we fit a version of the logistic model that also included state fixed effects ; for that model , we excluded 4 states ( north dakota , puerto rico , south dakota , and vermont ) with no crtp implants .
we present results as fitted device percentages ( out of all new implants ) in selected patient subgroups , rather than regression coefficients , for ease of interpretation .
we identified a cohort of 55  044 patients implanted with new crt or icd devices over 6  years ( figure  1 ) . the majority ( 68% )
were implanted with an icd , 27% with a crtd , and 5% with a crtp . among crt devices , crtd were the vast majority ( 85% ) . 

table shows the differences in demographics , heart failure characteristics , comorbidities , and medication use across the 3 device types .
implants of crtp devices were most likely to be implanted in the outpatient setting ( 55% ) , followed by crtd ( 53% ) , and icd ( 48% ) .
the crtp group had the highest proportion of women ( 40% ) , followed by crtd ( 30% ) , and icd ( 26% ) .
patients receiving crtp devices were older at implant ( median 76  years ) than those receiving crtds ( 67  years ) and icds ( 62  years ) .
baseline characteristics of patients with new implants ace indicates angiotensinconverting enzyme ; arb , angiotensin receptor blocker ; crtd , cardiac resynchronization therapy with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator ; optimal medical therapy , blocker and ace inhibitor or arb .
the most common cardiovascular diagnosis was congestive heart failure , found in the majority of patients ( crtp 55% , crtd 84% , icd 66% ) .
we also found high proportions with atrial fibrillation / flutter ( crtp 59% , crtd 29% , icd 23% ) .
cardiac conduction disorders were common only among patients with crtp ( 21% ) and crtd devices ( 27% ) , but not those with icd devices ( 8% ) .
the proportion of patients receiving both blockers and angiotensinconverting enzyme inhibitors or angiotensin receptor blockers prior to implant appeared low : only 31% of crtp , 46% of crtd , and 40% of icd patients .
these proportions did not change appreciably when limited to the population with a diagnosis of congestive heart failure .
the biggest distinctions between patients who received crtp ( compared to crtd ) were higher prevalence of atrial fibrillation / flutter and arrhythmias , and much lower prevalence of congestive heart failure and cardiac failure ( figure  2 ) .
figure  3 displays the percentage of people who received new implants out of the entire marketscan population in each year .
medicare advantage enrollees , who are older than commercial enrollees , had higher proportions of all implant types . in 2013 , for every 100  000 medicare enrollees , there were 11 crtp recipients , 33.8 crtd recipients , and 58 icd recipients . in the commercial population , these numbers were 0.4 , 2.9 , and 10.6 , respectively . for the remaining results , we combined the commercial and medicare populations .
each line represents the number of patients receiving each new implant type divided by the total number of enrollees in each year .
crtd indicates crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator . among new implants ,
icds dominated but decreased slightly over the study period , from a high of 72% of all implants in 2008 to 66% in 2013 .
crts represented 32% of new implants overall , of which the fraction of crtp devices grew from 12% to 20% over the study period .
figure  s1 contains the results from a multinomial model for receipt of each device out of all new implants .
the results from the binomial model for crtp receipt ( out of new crt implants ) from a model with year , age ( in quintiles ) , sex , and all interactions are shown in figure  4 .
all 3 predictors are influential . for example , among people in the middleage quintile ( ages 6168 ) in 2010 , women were 2.2 times as likely as men to receive crtp ( 18% versus 8% of new crt implants ) . in that same year , men in the oldestage quintile ( 77 and older ) were 2.9 times more likely to receive crtp than the youngest ( age 1854 ) : 23% versus 8% of new implants .
the trend in increasing crtp implants over the study period was stronger at older ages and among women .
for example , crtp proportion among men ages 18 to 54 remained essentially constant at 8% between 2008 and 2013 . among men 77  years and older , the crtp percentage increased from 18% to 27% . among women ,
the crtp share in women 18 to 45  years also remained nearly constant at 10% , while the share in those 77 and older increased from 25% to 43% of new implants .
each line shows the modeled probability of receiving crtp ( conditional on receiving a crt device ) by year ( x axis ) , age ( quintile , each line is a different quintile ) , sex ( men in the top row , women in the bottom row ) from a saturated logistic regression model .
crtd indicates crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator . adding state to this model allowed us to examine patterns across states , adjusted for age , sex , and year .
the state fixed effects from a binomial model of crtp implants ( out of all new crt implants ) illustrate the geographic variation ( figure  5 ) . among states with at least an average of 100 new implants per year
, we identified particularly high crtp percentages in south carolina and wisconsin , and particularly low shares in new york and indiana .
these state differences are sufficient to change the fitted proportions substantially . for example , the fitted percentage of crtp ( out of all new crt implants ) among women age 62 to 68 in 2013 is 26% in south carolina versus 12% in new york .
each point shows the state fixed effect from a binomial model for cardiac resynchronization therapy pacemaker ( crtp ) devices out of all new crt implants with segments extending 2 se on either side of the estimate .
numbers in parentheses give the average total annual implants in each state ; we display only results for states with at least 20 crtp implants .
in addition , we examined how residuals from the binomial model with state effects changed over time .
figure  6 shows the difference between the modeled and observed patterns of crtp proportions ( out of all new crt implants ) for women age 62 to 68 in 2013 , limited to results for states with an average of at least 100 annual total implants .
kansas appears to be increasing relative to national trends , while minnesota and oregon are decreasing .
lines connect the difference between each state 's annual cardiac resynchronization therapy pacemaker ( crtp ) percentage ( out of all new crt implants ) and the fit from a multinomial model that includes age , sex , year , and state .
the states are arranged in order of the overall trend of the residuals from most negative ( top left ) to most positive ( bottom right ) .
we identified a cohort of 55  044 patients implanted with new crt or icd devices over 6  years ( figure  1 ) . the majority ( 68% )
were implanted with an icd , 27% with a crtd , and 5% with a crtp . among crt devices , crtd were the vast majority ( 85% ) . 

table shows the differences in demographics , heart failure characteristics , comorbidities , and medication use across the 3 device types .
implants of crtp devices were most likely to be implanted in the outpatient setting ( 55% ) , followed by crtd ( 53% ) , and icd ( 48% ) .
the crtp group had the highest proportion of women ( 40% ) , followed by crtd ( 30% ) , and icd ( 26% ) .
patients receiving crtp devices were older at implant ( median 76  years ) than those receiving crtds ( 67  years ) and icds ( 62  years ) .
baseline characteristics of patients with new implants ace indicates angiotensinconverting enzyme ; arb , angiotensin receptor blocker ; crtd , cardiac resynchronization therapy with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator ; optimal medical therapy , blocker and ace inhibitor or arb .
the most common cardiovascular diagnosis was congestive heart failure , found in the majority of patients ( crtp 55% , crtd 84% , icd 66% ) .
we also found high proportions with atrial fibrillation / flutter ( crtp 59% , crtd 29% , icd 23% ) .
cardiac conduction disorders were common only among patients with crtp ( 21% ) and crtd devices ( 27% ) , but not those with icd devices ( 8% ) .
the proportion of patients receiving both blockers and angiotensinconverting enzyme inhibitors or angiotensin receptor blockers prior to implant appeared low : only 31% of crtp , 46% of crtd , and 40% of icd patients .
these proportions did not change appreciably when limited to the population with a diagnosis of congestive heart failure .
the biggest distinctions between patients who received crtp ( compared to crtd ) were higher prevalence of atrial fibrillation / flutter and arrhythmias , and much lower prevalence of congestive heart failure and cardiac failure ( figure  2 ) .
figure  3 displays the percentage of people who received new implants out of the entire marketscan population in each year .
medicare advantage enrollees , who are older than commercial enrollees , had higher proportions of all implant types . in 2013 , for every 100  000 medicare enrollees , there were 11 crtp recipients , 33.8 crtd recipients , and 58 icd recipients . in the commercial population , these numbers were 0.4 , 2.9 , and 10.6 , respectively . for the remaining results , we combined the commercial and medicare populations .
each line represents the number of patients receiving each new implant type divided by the total number of enrollees in each year .
crtd indicates crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator . among new implants , icds dominated but decreased slightly over the study period , from a high of 72% of all implants in 2008 to 66% in 2013 .
crts represented 32% of new implants overall , of which the fraction of crtp devices grew from 12% to 20% over the study period .
figure  s1 contains the results from a multinomial model for receipt of each device out of all new implants .
the results from the binomial model for crtp receipt ( out of new crt implants ) from a model with year , age ( in quintiles ) , sex , and all interactions are shown in figure  4 .
all 3 predictors are influential . for example , among people in the middleage quintile ( ages 6168 ) in 2010 , women were 2.2 times as likely as men to receive crtp ( 18% versus 8% of new crt implants ) .
in that same year , men in the oldestage quintile ( 77 and older ) were 2.9 times more likely to receive crtp than the youngest ( age 1854 ) : 23% versus 8% of new implants .
the trend in increasing crtp implants over the study period was stronger at older ages and among women .
for example , crtp proportion among men ages 18 to 54 remained essentially constant at 8% between 2008 and 2013 . among men 77  years and older , the crtp percentage increased from 18% to 27% . among women ,
the crtp share in women 18 to 45  years also remained nearly constant at 10% , while the share in those 77 and older increased from 25% to 43% of new implants .
each line shows the modeled probability of receiving crtp ( conditional on receiving a crt device ) by year ( x axis ) , age ( quintile , each line is a different quintile ) , sex ( men in the top row , women in the bottom row ) from a saturated logistic regression model .
crtd indicates crt with icd backup ; crtp , cardiac resynchronization therapy pacemaker ; icd , implantable cardioverter defibrillator .
adding state to this model allowed us to examine patterns across states , adjusted for age , sex , and year .
the state fixed effects from a binomial model of crtp implants ( out of all new crt implants ) illustrate the geographic variation ( figure  5 ) . among states with at least an average of 100 new implants per year
, we identified particularly high crtp percentages in south carolina and wisconsin , and particularly low shares in new york and indiana .
these state differences are sufficient to change the fitted proportions substantially . for example , the fitted percentage of crtp ( out of all new crt implants ) among women age 62 to 68 in 2013 is 26% in south carolina versus 12% in new york .
each point shows the state fixed effect from a binomial model for cardiac resynchronization therapy pacemaker ( crtp ) devices out of all new crt implants with segments extending 2 se on either side of the estimate .
numbers in parentheses give the average total annual implants in each state ; we display only results for states with at least 20 crtp implants .
in addition , we examined how residuals from the binomial model with state effects changed over time .
figure  6 shows the difference between the modeled and observed patterns of crtp proportions ( out of all new crt implants ) for women age 62 to 68 in 2013 , limited to results for states with an average of at least 100 annual total implants .
kansas appears to be increasing relative to national trends , while minnesota and oregon are decreasing .
lines connect the difference between each state 's annual cardiac resynchronization therapy pacemaker ( crtp ) percentage ( out of all new crt implants ) and the fit from a multinomial model that includes age , sex , year , and state .
the states are arranged in order of the overall trend of the residuals from most negative ( top left ) to most positive ( bottom right ) .
this study characterizes cardiac implantable electric device use in a large , nationwide sample of cardiac patients .
we found that crtp devices comprise a growing minority of new crt implants ( 1220% from 2008 to 2013 ) , with significant variation across states .
while the fraction of each implant type in the entire marketscan population does not reflect trends in the eligible populations , our study is among the largest samples of realworld inpatient and outpatient crt implants in the united states .
in addition , our finding of relatively low rates of appropriate neurohormonal blockade among device recipients raises questions about effective application of optimal medical therapy in these patients prior to device implantation .
the overwhelming preference for crtd devices among all crt recipients in our study contrasts sharply with the application of crt in other countries , particularly in europe .
a large multinational comparison of crtd and crtp implant rates reveal that among the 10 countries with the highest per capita rates of crt implantation , crtp devices range from 17% ( italy ) to 49% ( hungary ) of crt devices.30 in the swedish heart failure registry,31 63% of patients receiving crt were implanted with crtp.32 our data accord with a smaller , singlecenter study from the cleveland clinic , which demonstrated that among class iii / iv heart failure patients receiving crt , 95% received crtd versus crtp.33 even among patients aged > 80 , 86% received crtd.34 what drives these striking national differences in device selection is not clear .
american and european guidelines for crt are generally similar , including guidance indicating insufficient evidence that crtd is superior to crtp.35 
  some believe that older or frailer patients are better candidates for crtp rather than crtd or icd.36 our study finds that while crtp recipients were older , they were otherwise not more likely to have identified comorbidities compared to crtd recipients . in practice ,
patients receiving crtp devices have worse survival than those receiving icd or crtd.37 although older patients experience more inhospital mortality and complications of device implants,38 and may realize diminished survival benefit from icds,39 the existing evidence provides little guidance on how to select crtp versus crtd devices for individual patients.40 even the existing clinical trial data characterizes outcomes for patients younger than those found in registries and in our sample , with trial populations having a mean age of 69.4  years and only 6.4% of studied patients aged 85 or older.41 there are few data characterizing the differences between those who receive crt ( of either type ) and those who are apparently eligible but either decline or are never offered crt . identifying such patients may help elucidate the rationale for device selection , if in fact patient characteristics guide these decisions .
studies currently under way are evaluating how patients assess their options for devicebased therapy and whether decision support tools can streamline that process.42 
  several possible mechanisms may explain the increasing proportion of crtp devices among crt implants over the study period .
for example , changes in patient and provider preferences , population demographics , and evidence in favor of  ablate and pace  strategies may contribute . in our sample ,
32% of crtp recipients had av node ablation on the day of implant or in the 3  months after .
because providers and patients appear to favor crtp at older ages , demographic changes are relevant .
early signs of crt benefit in patients with atrial fibrillation began to appear in the literature43 , 44 before they were established by the blockhf trial in 2013.45 in addition , there is increasing recognition of pacingrelated cardiomyopathy , which generally responds well to upgrade to crtp.46 although our sample was restricted to de novo implants , increasing recognition of risk factors for likely future pacingrelated deterioration may create a pool of patients who become eligible for crtp implant but likely not crtd .
finally , federal audits of icd implants were launched in 2012 to investigate icd implants in patients excluded in the 40  days after acute myocardial infarction and 3  months following percutaneous coronary intervention .
the period of inquiry extended back to 2003 and  although icds were the subject of this initial inquiry , dualchamber pacemaker indications are also being actively scrutinized , and pci is likely to receive similar attention.47 increased scrutiny on these implants may have encouraged providers to adopt more conservative devicebased therapies .
we hypothesized that there would be geographic variation in crtp versus crtd utilization , as significant variability in practice patterns have been identified for other cardiac interventions .
previous studies have found wide variation in icd implant rates by patient , hospital , and region.48 , 49 , 50 , 51 otherwise eligible patients who are older , african american , and admitted to smaller hospitals are less likely to receive an icd , while larger , academic hospitals with the capability to perform other cardiac interventions are more likely to implant icd devices . in keeping with these results ,
our study found substantial variation in implant rates by geography , computed as the fraction of each device type out of the total share of devices .
the patterns of differences across states  adjusted for age , sex , and national time trends  were not changing appreciably over time in all but a handful of states .
thus , how crt decisions are made locally and what drives this regional variability requires further investigation .
optimal medical therapy reported in registry studies is much higher than what we find here.52 , 53 one study found 70% of patients without contraindications were prescribed a blocker and angiotensinconverting enzyme inhibitors / angiotensin receptor blockers following implantation with a crtd device . back calculating from the study
, we can see that in their cohort of 45  392 patients receiving a crtd implant , 96% to 99% of patients had no contraindication . these studies both used reported  discharge on  optimal medical therapy from the national cardiovascular data registry icd registry .
a more recent study examined guidelinerecommended medical therapy prior to primary prevention icd implant using part d claims linked to the national cardiovascular data registry icd registry.28 like that study , our claimsbased analysis reflects prescription fills rather than prescriptions , and therefore may reflect actual medication use .
the roth et  al study distinguished between any claim for guidelinedirected therapy ( 61% of patients ) and an  adequate supply 
( 28% of patients ) , which they defined as 80% coverage of the 90  days leading up to implant .
our definition of drug use requires 90  days supply in the 6  months prior to implant , which is somewhere between these 2 definitions .
further work to reconcile these apparent differences will be important for characterizing whether , in fact , these patients are receiving guidelinebased care prior to and concurrent with their device therapy .
our study has several potential limitations , arising in part from our methodological strengths , including the broadly representative population of commercially insured and medicare enrollees .
the icd registry does not include crtp devices , so we are uniquely positioned to study crtp , crtd , and icd devices .
however , in this data source , diagnosis and procedure codes may not accurately reflect a patient 's clinical characteristics . in particular , our inability to measure left ventricular ejection fraction and qrs morphology and duration are significant limitations of our claimsbased analysis .
registrybased studies contain much more comprehensive information about each patient and device implant , but lack followup information about outcomes and subsequent healthcare use .
we are also limited in our ability to adjust for additional patient characteristics , such as comorbidities , in models for geographic and temporal variation .
even in such a large database as this , the total number of patients implanted with crtp devices was quite small .
for example , in a mediumsized state like maryland ( 153 average annual total implants ) , there are only 1 or 2 crtp implants in each sexage group each year , sometimes none .
following publication of the blockhf trial in 2013,45 it is reasonable to expect increasing use of crtp devices for patients with av block who do not have indications for icd therapy .
our study period precedes publication of this trial , but we have no left ventricular ejection fraction measurements or data beyond 2013 , so we can not directly address the question of changing practice in response to blockhf . although large randomized trials comparing crtp and crtd devices are unlikely , research to identify variation in patient responses to crt therapy can leverage geographic variation in practice to perform quasiexperimental analyses and identify subgroups of patients most likely to benefit from crtp devices .
furthermore , recent developments in behavioral economics provide examples of effective means to improve adherence with guidelinerecommended practice , such as a sufficient course of optimal medical therapy prior to device implant . for example
, a recent study found that inappropriate antibiotic prescribing could be reduced by regular emails to physicians describing their performance as 
top performing  or not.54 electronic health records could facilitate these interventions by enabling automatic report generation for physicians and patients . in sum , our large
, national study of cardiac implantable electric device use in a commercially insured population demonstrates that , among crt recipients , crtd is overwhelmingly selected , though a small increase in crtp use has been seen in recent years , especially among older patients and women . in future work , we will describe outcomes of device therapy that are measurable in claims , particularly subsequent hospitalbased healthcare use and the frequency with which each device type is upgraded , downgraded , or removed ( for example , icd downgrades to pacemakers).55 in ongoing work , we are studying trends in crtp use among the feeforservice medicare population .
the longitudinal dynamic treatment regimens for patients with implanted devices have not been previously studied .
we also plan to fit and validate a model of eligibility in a rich data source such as a registry and apply it to the claims data using observables and statistical methods for incorporating external data.56 this will clarify the treatment selection patterns within the larger population of potentially eligible recipients .
hatfield and normand received funding from us food and drug administration grant ( u01 fd00449301 ) .
kramer is supported by a career development award from the paul beeson scholars program ( k23ag045963 ) .
each line shows the modeled probability of receiving a particular device ( conditional on receiving any new implant ) by year ( x axis ) , age ( quintile , each line is a different quintile ) , sex ( men in the top row , women in the bottom row ) from a saturated multinomial regression model .
crtd indicates cardiac resynchronization therapy with icd backup ; crtp , cardiac resynchronization therapy pacemaker , icd , implantable cardioverter defibrillation .
 backgroundcardiac implantable electric devices are commonly used to treat heart failure . 
 little is known about temporal and geographic variation in use of cardiac resynchronization therapy ( crt ) devices in usual care settings.methods and resultswe identified new crt with pacemaker ( crtp ) or defibrillator generators ( crtd ) implanted between 2008 and 2013 in the united states from a commercial claims database . for each implant , we characterized prior medication use , comorbidities , and geography . among 17  780 patients with crt devices ( median age 69 , 31% women ) , 
 crtps were a small and increasing share of crt devices , growing from 12% to 20% in this study period . compared to crtd recipients , 
 crtp recipients were older ( median age 76 versus 67 ) , and more likely to be female ( 40% versus 30% ) . 
 preimplant use of blockers and angiotensinconverting enzyme inhibitors or angiotensin ii receptor blockers was low in both crtd ( 46% ) and crtp ( 31% ) patients . 
 the fraction of crtp devices among all new implants varied widely across states . compared to the increasing national trend , the share of crtp implants was relatively increasing in kansas and relatively decreasing in minnesota and oregon.conclusionsin this large , contemporary heart failure population , crtd use dwarfed crtp , though the latter nearly doubled over 6  years . 
 practice patterns vary substantially across states and over time . 
 medical therapy appears suboptimal in realworld practice . 
Methods
Data Source
Study Cohort
Variables
Statistical Analysis
Results
Patient Characteristics
Proportional Device Utilization
Temporal and Geographic Trends in Device Use
Discussion
Sources of Funding
Disclosures
Supporting information