Kleinman, Nathan L. PhD; Rohrbacker, Nicholas J. MS; White, Sarah A. MPH; March, Jamie L. MBA; Reynolds, Matthew R. MD, MSc
Arrhythmias are a heterogenous set of disorders of the cardiac electrical rhythm that cause the heart to beat slowly (bradyarrhythmias), rapidly (tachyarrhythmias), or in an uncoordinated fashion, leading to symptoms and, in some cases, morbidity and mortality. The broad category of tachyarrhythmias includes supraventricular tachycardia (SVT), ventricular tachycardia (VT), ventricular fibrillation or flutter, atrial fibrillation (AF), atrial flutter (AFL), and unspecified cardiac dysrhythmias.
Arrhythmias frequently prompt hospital admission1 and result in high health care costs for both direct treatment and associated disabilities. For example, AF, the most common arrhythmia, results in more than $6.6 billion in annual direct medical costs2 and is also a leading cause of ischemic stroke.3,4 Some arrhythmias have their peak incidence in working-age adults (eg, SVT).5 The onset of AF is distinctly age related6 and is likely to affect employed individuals with increasing frequency, given an aging workforce and trends toward delayed retirement.7–11 Arrhythmias, therefore, represent a substantial burden to employers who pay for a large portion of medical care through employee and dependent health plans and who bear the costs of absence and productivity loss.12,13
The main treatment options for most tachyarrhythmias are medications and catheter ablation; the latter involves the selective destruction of targeted areas within the heart that are critical to arrhythmia occurrence by using a catheter that delivers thermal energy. In general, because of its invasive nature, ablation tends to be reserved for patients in whom medical therapy proves ineffective or poorly tolerated.14–16 Nonetheless, accumulating evidence suggests that for many arrhythmias, catheter ablation is more effective than medical therapy and has low rates of serious complications.17–19 With success rates between 56% and 86% for AF15 and success rates exceeding 90% to 95% for some arrhythmias—most notably SVT and AFL18—ablation is therefore considered a reasonable first-line therapy in a number of circumstances.14,20
Several published observational series and cost-effectiveness models have predicted that catheter ablation for appropriate SVT and AF patients would result in reduced downstream medical expenditures compared to medical therapy alone, such that the up-front costs of ablation procedures would be fully or mostly recouped within a reasonable timeframe (4 to 10 years).21–23 However, these studies were based on limited empirical data, did not specifically examine costs from an employer perspective and did not explicitly consider working populations.
To further assess the impact of catheter ablation for arrhythmia from an employer perspective, we examined a large, employer-based database containing information on medical, pharmacy, sick leave, disability, and worker's compensation claims. For both employees and dependent spouses, we compared costs between patients who underwent catheter ablation for any arrhythmia, and AF specifically, and those who did not.
MATERIALS AND METHODS
The analytic database supporting this research was produced from the Human Capital Management Services Research Reference Database24–31 and contained deidentified, integrated information between January 1, 2001, and April 1, 2008, from various large employee workgroups representing all 50 states.
Cohort Selection and Outcome Measures
An arrhythmia diagnosis among employees and dependent spouses was identified by using medical claims with a primary, secondary, or tertiary International Classification of Diseases–9th Revision (ICD-9) codes of 426.7x, 427.0x, 427.1x, 427.2x, 427.31, 427.32, 427.41, 427.42, or 427.9x. The treatment-choice analyses included only those employees who had at least 1 year of health plan enrollment after the date of the earliest arrhythmia diagnosis found in the claims data. For dependent spouses, only those associated with an employee who had at least a year of medical eligibility after the dependent's first diagnosis date were included. In this treatment-choice study population, means or percentages and standard errors for age, tenure (years with current employer), annual salary, gender, marital status, race, exempt status (salaried vs hourly employees), and full-time status were calculated for employees, and similar statistics for age and gender were calculated for dependent spouses.
The treatment-choice analyses measured the unadjusted values for the percentage of the population with an ablation procedure, average number of arrhythmia-related medications per patient, and percentage of the population with claims for arrhythmia-related drugs.
Ablation procedures were identified in the medical claims data by using Current Procedural Terminology (CPT) codes 93651 (intracardiac catheter ablation of arrhythmogenic focus, for treatment of SVT) or 93652 (intracardiac catheter ablation of arrhythmogenic focus, for treatment of VT). CPT code 93650 (intracardiac catheter ablation of atrioventricular node function) was excluded from subsequent portions of the analysis, as this procedure obligates permanent pacemaker insertion and is not intended to be curative.18 In addition to ablation, drug treatment options included warfarin and medications from the Vaughan Williams classification.32,33
The next set of analyses measured the economic impact of ablation on various outcomes in those employees and dependent spouses with arrhythmia and those with AF. Unlike the treatment-choice analysis described previously, subjects in the impact of ablation analyses were not required to have a full year of health plan enrollment after their first diagnosis. In the impact of ablation analyses, for patients treated with an ablation procedure, the index ablation date was calculated as the date of the first ablation procedure found in the data for that patient. For patients without ablation, the index date was defined to be the average index date from the patients who received ablation. To describe the subjects in the impact of ablation analyses, means or percentages and standard errors for age, tenure, annual salary, gender, marital status, race, exempt status, and full-time status were calculated for employees and similar statistics for age and gender were calculated for dependent spouses. These descriptive statistics were then compared between patients with ablation and patients without ablation.
Monthly medical and absence costs and other outcomes were calculated for each patient for up to 11 months before the index date and up to 36 months after the index date, depending on the length of the patient's benefit plan enrollment.
In the ablation economic analyses, for employees and spouses with arrhythmia, the impact of ablation on the following outcomes was modeled: adjusted average monthly costs for arrhythmia-related medical costs, non–arrhythmia-related medical costs, total medical costs, and prescription drug costs. In all applicable medical cost categories, the ablation procedure itself and any costs after the index date, including any recurrent ablation procedures, were captured in the postindex cost calculations. Wage replacement costs for sick leave and short-term disability (STD) were also modeled for eligible employees. Similar metrics were modeled for employees and dependent spouses specifically with AF (primary, secondary, or tertiary ICD-9 code of 427.31). Arrhythmia-related medical costs were defined as those from claims with ICD-9 codes from the “Circulatory” major diagnostic category and the specific categories “Thyroid disorders,” “Acute posthemorrhagic anemia,” “Coagulation and hemorrhagic disorders,” “Cardiac and circulatory congenital anomalies,” and “Syncope,” as defined by the Agency for Healthcare Research and Quality (AHRQ).34
Average monthly inpatient days, emergency department visits, and the number of distinct arrhythmia-related medications taken were also modeled. The number of medications was based on a count of unique brand or generic drug names from the medications included in the Vaughan Williams classification and warfarin.
Descriptive statistical comparisons between patients with and without ablation were made by using t tests for continuous variables and chi-square tests for binary variables. Generalized linear models with γ distribution and log link compared monthly pre- and postindex outcomes between patients with and without ablation. The γ distribution better accounts for the nonnormal distributions of these outcomes. For some outcomes (medical, drug, and sick leave costs of overall arrhythmia patients), an additional logistic model was also used to calculate the adjusted probability of nonzero costs.35 Since these models generally use a nonlinear link function, the results will not be additive as they may be when an identity link is used, such as in ordinary least squares linear regression. This is evident in this study when adjusted arrhythmia-related medical costs and adjusted non–arrhythmia-related medical costs do not sum to the adjusted total medical costs presented.
All regression models controlled for differences between patients with and without ablation in type of arrhythmia, age, gender, preperiod Charlson Comorbidity Index,36 all major AHRQ diagnostic categories except “Circulatory,” and all circulatory system-specific AHRQ categories not containing ICD-9 codes used to define arrhythmia. Also included as independent variables were dichotomous indicator variables for each month in the time frame (from 11 months before an individual's index ablation date to 36 months after the index ablation date) and interaction terms between the ablation variable and the month variables. For employees, the following variables were available and also included: marital status, race, exempt status, full-time/part-time status, salary, and region (defined by the first digit of the employee's zip code).
For each outcome studied, the regression models produced adjusted monthly average values for the ablation and nonablation cohorts from 11 months before the index ablation date to 36 months after the index ablation date. For each individual month, t tests compared the adjusted values between cohorts. Subsequently, a postindex relative-difference time series was created each month for each outcome by subtracting the nonablation cohort outcome from the ablation cohort outcome. In addition, the average difference from the preindex period between the ablation and nonablation cohorts was then subtracted from each monthly difference. Therefore, the relative monthly postindex outcomes differences were defined as
Relative difference = (monthly postindex outcome for ablation cohort − monthly postindex outcome for nonablation cohort) − (monthly preindex outcome for ablation cohort − monthly preindex outcome for nonablation cohort)
or, in other words, the actual postindex outcomes difference minus the preindex outcomes difference. The purpose of this relative difference calculation is to account for any differences in average preindex outcomes between the ablation and nonablation groups that may not have been fully accounted for by the regression modeling. Autocovariance-adjusted 95% and 90% confidence intervals were then built for the mean of the monthly relative differences to test the relative difference between the ablation cohort's outcomes and the nonablation cohort's outcomes. Finally, for medical, drug, STD, and sick leave cost outcomes, the analysis then divided the postindex average relative monthly difference between the ablation and nonablation cohort costs into the ablation-period costs (medical, drug, STD, or sick leave costs incurred from 30 days before the ablation procedure through 30 days after the ablation procedure) to calculate the number of months after ablation required to recover the cost of ablation.
All models and statistics were generated by using version 9.1 of the SAS System for Windows (Copyright SAS Institute, Inc, Cary, NC).
Treatment Choices Among Employees and Dependent Spouses With Arrhythmia or Atrial Fibrillation
Table 1 provides descriptive statistics for patients with a year of health plan enrollment after the first arrhythmia diagnosis. Note that some patients received a diagnosis code from more than one arrhythmia type; therefore, the N from the “Any Arrhythmia” column is not the sum of the N's from the other columns. Employees with any arrhythmia were 39% women and, on average, were 45 years of age, had 10.5 years of tenure with their current employer, and had an annual salary of $61,587. Fewer employees with AF were women (27%) and, on average, were older (49 years), had longer tenure (11.8 years), and had higher salaries ($64,456). Dependent spouses with arrhythmia were 62% women and, on average, were 47 years of age, while spouses with AF were only 41% women but averaged 52 years of age.
Table 2 shows the percentage of these employees and dependent spouses who received each of the different treatment types during the year after the first arrhythmia diagnosis. The highest rate of ablation was found in patients with AFL, with 15.82% of those patients receiving ablation. Overall, the rate for ablation was 2.58%. Again, the group of patients with AFL had the highest average number of arrhythmia-related medications (1.68). Overall, the average number of different medications was 0.78. This could be explained in most part by the heavy influence that the unspecified dysrhythmia group had on the overall average. This group was the largest subpopulation of arrhythmia patients and had the lowest average number of medications (0.57). The “unspecified” codes were generally used for patients who lacked a precise arrhythmia diagnosis, thus the observation of lower drug utilization in this group was not surprising. Some patients with infrequent or mild episodes of arrhythmia could also be safely and effectively managed with drug treatment at the onset of symptoms (eg, with a “pill in the pocket” approach) rather than with daily medications.
β-Blockers were the most prominent drug used, ranging from 25.94% for unspecified dysrhythmias to 54.35% for VT, ventricular fibrillation or flutter, or VFL. Warfarin usage was highest in patients with AF and AFL. The percentage of patients taking calcium antagonists was generally between 8% and 20% for all groups.
Impact of Ablation in Employees and Dependent Spouses With Arrhythmia or Atrial Fibrillation
In the analyses of the impact of ablation on outcomes, a total of 7148 employees with arrhythmia (166 with an ablation and 6982 without ablation) had at least 1 month of health plan enrollment at the index date. Sixty-five percent of the employees without ablation were enrolled 11 months before the index date, increasing to the full 100% at the index date and then decreasing to 15% still enrolled 36 months after the index date. Of the 166 employees who had an ablation, 62% were enrolled 11 months before the ablation and 11% were still enrolled 36 months after the ablation. Similarly, there were 4143 dependent spouses with arrhythmia (114 of these had an ablation), 2171 employees with AF (66 with an ablation), and 891 dependent spouses with AF (27 with an ablation) enrolled in a health plan at the index date. The attrition rates for employees with AF were very similar to those of the employees with any arrhythmia. The attrition among dependent spouses was somewhat less. Among those with ablation, 67% to 70% of dependents were enrolled 11 months before the ablation and 11% to 19% were enrolled 36 months after the ablation. Among dependents without an ablation, 94% to 95% were enrolled 11 months before the index date and 26% to 29% were still enrolled 36 months after the index date.
Table 3 provides a comparison of descriptive statistics between employees and dependent spouses who had and who did not have ablation. Most differences between ablation and nonablation patients were not significant. Nevertheless, AF employees with ablation had higher annual salaries ($75,588) than AF employees without ablation ($62,484). Also, among employees with any arrhythmia, those with ablation were more often white (62.0%) than those without ablation (46.9%) and those with ablation were less likely to be missing racial information. Finally, among dependent spouses with AF, the average age of those with ablation (44.45 years) was significantly less than that of those without ablation (50.81 years).
Ablation-period total costs (costs incurred from 30 days before the ablation procedure through 30 days after the ablation procedure) were $15,035 and $22,661 per patient for employees with any arrhythmia and for employees with AF, respectively (includes medical, drug, sick leave, and STD costs). Ablation-period total costs were $15,279 and $27,308 per patient for dependent spouses with any arrhythmia and for dependent spouses with AF, respectively (includes only medical and drug costs).
Figure 1 shows the adjusted total monthly medical, drug, sick leave, and STD costs per employee for employees with any arrhythmia who had and who did not have ablation. The figure highlights the spike in costs, representing the cost of the ablation procedure, but the figure also shows that the ablation cohort's costs were generally lower after the ablation than the nonablation cohort's costs. Visually similar results were found for employees with AF, dependent spouses with any arrhythmia, and dependent spouses with AF.
As is illustrated in the “total cost” rows of Table 4, each ablation cohort was relatively less costly after ablation than the corresponding cohort without ablation, and ablation-period costs for each subpopulation were estimated to be recovered within 38 to 50 months of the ablation procedure. Also, relative postindex arrhythmia-related medical costs were significantly or nearly significantly lower (relative to the preindex period) for patients with ablation than for patients without ablation in all four subpopulations. To illustrate, for employees with AF, Fig. 2 shows that relative postindex arrhythmia-related medical costs were $249 per month lower among those with ablation than among those without ablation (the pre- to postmonthly cost increase was $249 less for employees with ablation than for those without ablation). Extending this $249 savings for 80 months just covers $19,700 in average arrhythmia-related medical costs surrounding the ablation procedure for this group of employees (hence, the 80-month cost recovery period as shown in the corresponding row of Table 4).
Table 4 also shows that total medical costs were significantly lower in the ablation cohort for employees and dependent spouses with an arrhythmia and for spouses with AF. Prescription drug costs were significantly lower in the ablation cohort for employees and spouses with an arrhythmia, and STD and sick leave costs were significantly lower in the ablation cohort for both employees with an arrhythmia and employees with AF.
Table 5 shows that the average relative number of monthly emergency department visits after ablation was significantly lower for employees with an arrhythmia receiving ablation than for those not receiving ablation. Inpatient days and the number of medications were not significantly different between the two cohorts. For employees with AF, emergency department visits were significantly less frequent in the ablation cohort but the number of medications postindex was significantly higher. The number of inpatient days showed no significant difference between the two cohorts. Furthermore, for employees with ablation, more than half of the preindex inpatient and emergency department claims were from the AHRQ's “Circulatory” major diagnostic category and less than half of the postindex inpatient and emergency department claims were due to “Circulatory” diagnoses. In the nonablation cohort, less than half of the inpatient and emergency department claims were due to “Circulatory” diagnoses in both the pre- and postindex periods. For dependent spouses with an arrhythmia, the number of medications was significantly lower for the cohort with ablation. For spouses with AF, all three utilization metrics were significantly lower in the cohort with ablation.
Arrhythmia patients, including the AF subgroup, who underwent an ablation procedure generally experienced relative reductions in their benefit utilization sufficient enough to recover the expenses incurred from the ablation procedure itself. Total costs were recovered for employees and dependent spouses with an arrhythmia receiving ablation by 44 and 38 months after the ablation procedure, respectively. Relative recovery for individual benefits happened as early as the second month (eg, employee STD costs).
In the case of employees and dependent spouses with AF, relative recovery of total expenditures for ablation therapy was seen after 50 and 38 months, respectively. Also for employees with AF, relative expenditures for prescription drug, sick leave, and STD were recovered within 1.5 years after ablation.
The sick leave and STD relative cost results in the current study are notable, because they indicate the possibility of significant productivity gains by employees who receive ablation therapy. Prior research indicates that productivity loss (not just absence payments) because of illness may be greater than the direct medical and drug costs of the illness.12–13 Therefore, improving both the health and the productivity of employees with arrhythmia or AF is important for both patients and employers.
Inpatient days, emergency department visits, and the number of arrhythmia-related medications were generally lower postindex in the cohorts of patients who had ablation. These decreases in utilization helped to explain why patients generally experienced relative cost reductions after ablation.
Overall, all relative monthly postindex differences (fifth column of numbers in Tables 4 and 5) were either significantly in favor of ablation or nonsignificant, except the relative difference in number of medications postablation in the AF group. In general, the relative postindex total cost differences between the ablation and the nonablation cohorts were between $321 and $704 per month in favor of the ablation cohort, a significant portion of the patients’ monthly costs.
Our finding that ablation is associated with cost savings further supports the value of ablation for treating arrhythmias in addition to previously published studies on the safety and efficacy of ablation. A meta-analysis18 reported that ablation therapy was highly effective, with single- and multiple-procedure successes in 93.2% and 94.6% of SVT cases, respectively, and single and multiple-procedure successes in 91.7% and 97.0% of AFL cases, respectively. Adverse event rates and all-cause mortality rates were only 2.9% and 0.1%, respectively, in patients with SVT and were only 0.5% and 0.6%, respectively, in patients with AFL. Two randomized comparisons showed better safety and efficacy results in AFL patients receiving ablation than in patients receiving antiarrhythmic drug (AAD) therapy, including better long-term success rates, reduced likelihood of rehospitalization, and improved sense of well-being and daily-life functioning.37,38
A prospective randomized study by Wilber et al19 demonstrated that in AF patients previously unresponsive to initial drug therapy, ablation resulted in a significantly higher success rate versus continued attempts at rhythm control with alternative AAD therapy (70% vs 19%, respectively, remained free of symptomatic recurrent atrial arrhythmias). Furthermore, the ablation patients exhibited a substantial reduction in symptoms and a clinically meaningful improvement in quality of life versus those managed with continued AAD therapy. Thirty-day major treatment-related complications in the ablation group occurred in 4.9% of the ablation group versus 8.8% of the AAD group.
In addition, Calkins et al17 found ablation to be more successful than AAD therapy in patients with AF. Their meta-analysis showed that AAD therapy had a success rate of 52%, while ablation had a single-procedure success rate of 57% and multiple-procedure success rates between 71% and 77%. Major complications occurred in 5% of AF patients receiving ablation, whereas adverse events (though less severe) occurred in 30% of AF patients receiving only AAD therapy.
The current study is also consistent with previously published cost-effectiveness models comparing ablation to drug therapy in patients with SVT and AF. In comparison with drug therapy, radiofrequency ablation reduced expected lifetime medical expenditures in patients with SVT by $27,900 and substantially improved quality of life when used to treat highly symptomatic patients.39 For AF, a Canadian study predicted that ongoing costs of drug therapy would exceed the costs of ablation therapy after 3.2 to 8.4 years,22 while a US study with more conservative assumptions projected cost neutrality after approximately 10 years.23
In the current study, total relative costs were recovered within 38 to 50 months after ablation. This time frame is meaningful because, even though the employees came from a variety of job types and industries, the average tenure of employees with arrhythmia was 10.5 years and the average tenure of employees with AF was 11.8 years. This suggests that employees with these conditions do not move frequently from one employer to another on average (note that the attrition in the study cohorts was due more to subjects having index dates less than 3 years before the end of the study than to subjects leaving employment). Thus, it is likely that total benefit costs associated with ablation may be recovered during the employee's time with his or her employer. Also, since the cost recovery calculation cannot account for indirect costs such as increased productivity and lower replacement costs for missed work, the time to recovery may be less than what is calculated in this analysis.
The time-to-cost recoveries for ablation are also consistent with those found for other procedures. Uncomplicated kidney transplants had a time-to-cost recovery of 20.4 months when compared to dialysis treatment.40 Cremieux et al41 found that the initial investment in bariatric surgery is recouped within 24 to 48 months. In patients with complete suprasacral spinal cord injuries and neurogenic bladder and bowel, an implanted neuroprosthesis for bladder and bowel control recovered costs after 60 months when compared with conventional therapies.42 Conversely, in contrast to ablation, a European study found that reflux esophagitis patients who received an open antireflux operation did not recover costs within 60 months in comparison with patients treated daily with medical management.43 Most of these studies included only medical and drug costs (insurer perspective), though the European study included sick leave costs in part of the study.
The current study extends prior research in several ways. This study appears to be the first to examine the impact of ablation therapy in a population of employees and their dependent spouses, allowing employers to better understand the economic impact of treatment options. Both populations are large in comparison to many prior studies. Furthermore, the generalized linear regression methods used to control for differences between the ablation and nonablation cohorts are better able to account for the nonnormal distributions of many of the outcome variables. Finally, our results may validate assumptions of prior cost-effectiveness models by empirically demonstrating reductions in multiple categories of health care resource utilization after ablation.
In all models, every attempt was made to control for differences between the cohorts, however, the retrospective design of the study does allow for deviations between the groups to have an effect on the results. It is possible that discrepancies in treatment modalities because of differences in providers, job type, etc can play a role in the outcome, and cannot be compensated for in the analysis.
Also, since claims data were used to identify the cohorts, procedure coding errors could have led to misclassification of patients in the ablation and nonablation cohorts.
Years of schooling are a very important predictor of almost all health variables, but this information was not available for a large percentage of the study population. It is hoped that the inclusion of the employee's salary in the regression models has served as an adequate surrogate for schooling in addition to serving as a partial surrogate for a patient's ability to obtain health care services.
Since ablation (a treatment used to reduce symptoms and improve quality of life) is currently a second-line treatment of most arrhythmias, the selection of patients best suited for the ablation procedure may be limited to those who are highly symptomatic and have not responded to traditional medical therapy. Such patients would therefore be expected to consume greater medical resources and experience greater symptoms and work limitations from their condition, at least before ablation, than those patients not treated with ablation. This may explain why some of the ablation cohorts in this study had higher preindex costs than the associated nonablation cohorts. Nevertheless, extensive adjustments were made to make the groups similar (particularly in terms of comorbid conditions and preindex costs) when making the relative outcomes comparisons. If ablation patients were more (or less) sick before ablation than nonablation patients, this difference would have been equalized through the controls in the regression modeling and through the relative outcome calculations shown in Tables 4 and 5.
The results from this study have been presented from the perspective of the employer. If viewed from other perspectives, it is possible that the time to cost recovery could be different. For example, it could take longer to recover ablation costs from a health insurer's perspective if work-absence costs were not included. Conversely, from a societal perspective, the time to cost recovery could be shorter than that presented here if productivity and quality-of-life costs were part of the total.
This study found that, in terms of benefit outcomes, ablation is an effective therapy alternative for arrhythmia, in general, and for AF, specifically. For many outcomes, and for total costs in particular, the initial ablation therapy costs are recovered in a reasonable period of time compared with other surgical procedures such as bariatric surgery and neuroprosthesis, a period of time that is short enough to be very relevant to employers sponsoring health plans.
Given the high cost of AF and other arrhythmias to employers,44 the low prevalence rates of ablation therapy, and the beneficial outcomes of ablation seen in this study and others, further study of the effects of increasing the utilization of ablation therapy in appropriate patients may be warranted. This is particularly true in the case of a costly arrhythmia such as AF, which is likely to be more prevalent in the employed population going forward, given an aging workforce and a trend toward delayed retirement. Although not all patients with AF or other arrhythmias would be candidates for ablation therapy, this study suggests that some additional cost and absence improvements may be possible. By considering the benefits of ablation therapy, employers may improve both the costs and the health of certain employees and dependents.
This research was funded by Biosense Webster, Inc.
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