In our study analyzing AF ablation admissions in the US from 2005–2013 using real-world data from the NIS, there has been an increasing annual trend of ablations performed on obese (6.1% in 2005 to 17.5% in 2013) and diabetic (10.5% in 2005 to 18.8% in 2013) patients. The overall complication rate, median LOS and inflation adjusted charges have gradually increased, by approximately 2-fold or more, in both obese and diabetic patients. After adjusting for demographics, clinical variables and hospital size and volume, obesity was associated with 39% increase in complication rates driven mainly by an increase in vascular/hemorrhagic and respiratory complications. Obesity was also independently associated with longer LOS and higher inflation adjusted charges. Diabetes, however, was only associated with increased respiratory complications and longer LOS. Whether aggressive risk factor modification, particularly weight loss, prior to AF ablation reduces ablation costs and complications requires further extensive evaluation in future studies.
Catheter ablation is becoming standard-of-care for many AF patients due to its association with improved outcomes and quality-of-life 25 compared to medical therapy. However, it does not come without risks. It is performed while patients are taking oral anticoagulation, and most are still lengthy procedures performed under general anesthesia 26. Advanced techniques such as ultrasound guidance for vascular access and trans-septal puncture have made the procedure safer in patient with comorbidities such as obesity 27,28. Nevertheless, these advanced tools are not widely used in low-volume community centers. NIS real-world data in our study shows that the number of ablations performed on patients with obesity, diabetes or both has increased over the years, compared to those without both comorbidities, and most were performed in low-volume centers. Clinical trials and studies from specialized centers have shown that obesity and diabetes were not significantly associated with increased complication rates 16,17 24. However, most of these studies involved experienced operators at high-volume centers. One NIS study from 2000–2010 showed an estimated procedural complication rate of 6.29% 23, compared to 2.9% reported in a meta-analysis 29. In another study using the national readmission database, 1 in 200 patients died within 30 days and mortality was independently linked to procedural complications 30. Although mortality rates in this study were probably inflated due to selection bias prompted by the CMS 2013 two-midnight rule, it provides insights on the detrimental impact of procedural complications on early mortality. For example, complications due to cardiac perforation or neurological complications were associated with a mortality odds ratio of 2.98 and 8.72 respectively. In our study, we included NIS data only until 2013 to minimize the selection bias resulting from implementation of the two-midnight rule. We showed increasing annual trends in overall complications in all groups across the 9-year study period and the magnitude of the increase was much larger in patients with either obesity, diabetes or both compared to those with neither comorbidity. Even if our data is subject to selection bias due to the nature of the NIS, the increasing annual rate of captured admissions for AF ablation in patients with these comorbidities supports our conclusion that they had a higher rate of complication requiring admission.
In our study, median LOS doubled for most years in patients with either obesity and/or diabetes but remained relatively steady at 1 day for patients without either comorbidity. The total inflation-adjusted charges associated with inpatient AF ablation gradually increased by 2-fold across all groups. The largest difference ($ 11,844) in charges was between obese non-diabetic patients and non-obese non-diabetic patients in 2013. This may be due to higher procedural and equipment charges, longer LOS, or higher charges to treat complications. The median total charges associated with inpatient AF ablations in our study are significantly higher than the costs reported in a study of Medicare supplemental databases and MarketScan® commercial claims from 2007–2011 (Median cost $25,100 with large facility variation in costs) 31 . These findings may be due to differences in the nature of total charges captured in the NIS, which includes the total amount billed to all payers and not necessarily the actual cost of service or payment received by the hospital. In general, these significant cost variations suggest opportunities for cost reduction through several strategies, one hypothetically being aggressive risk factor modification and weight loss before ablation.
We also demonstrate that in all captured AF ablations, obesity was independently associated with increased complication rates (driven primarily by vascular/hemorrhagic and respiratory complications), longer LOS and higher charges after adjusting for demographics, clinical variables, and hospital volume and size. Increased vascular/hemorrhagic complications in obese patients may be due to difficulty in attaining vascular or trans-septal access even with ultrasound guidance and inadequate hemostasis after catheter removal. Moreover, obese patients undergoing general anesthesia or conscious sedation during this relatively lengthy procedure may experience higher rates of respiratory complications related to worse respiratory mechanics 32. Obese patients have been shown to have significantly longer procedural duration than non-obese patients in a meta-analysis 18, possibly contributing to respiratory complications. The higher costs associated with obesity may be indicative of differences in anesthesia approaches (more general anesthesia rather than sedation) and not just hospital stay and complications. Diabetes, on the other hand, was only associated with worse respiratory complications and longer LOS. Further studies are needed to examine the reasons behind these associations. Other considerations for more studies are differences in operator factors in earlier years such as groin management, anesthesia and anticoagulation strategies that may have affected outcomes, so that further exploration is done to identify the optimal anesthesia and anticoagulation strategies for patients with these risk factors.
The literature extensively describes that poorly controlled obesity and diabetes lead to increased AF recurrence rates after catheter ablation 13–15. Risk factor modification like weight loss with or without bariatric surgery, glycemic control, blood pressure control, and sleep apnea treatment have been shown to increase arrhythmia-free survival rates 33. We hypothesize that risk factor modification through weight loss prior to AF ablation may also reduce procedural complication rates and charges, but further prospective evaluation is ultimately required. While novel ablation techniques such as pulsed field ablation promise shorter procedures,34 we must exercise caution when performing ablations in obese patients, and consistently utilize advanced techniques that guarantee best outcomes such as ultrasound guidance.
Limitations:
The NIS is a deidentified administrative database making it difficult to validate individual ICD-9-CM codes. This significantly affects the sensitivity and specificity when applying the diagnostic codes. Studies based on data mining are susceptible to errors related to coding. Obesity and diabetes were defined using ICD-9 codes, which may not be reliable particularly prior to electronic health records. In addition, outcomes related to the severity of obesity were not examined due to insufficient BMI coding in our sample (< 10%) and the potential for selection bias. The data from the NIS lacks the level of detail and patient phenotyping available from clinical trials and registries. As previously described, our study is subject to selection bias towards AF ablations requiring admission due to the two-midnight rule. However, censoring our analysis at 2013 was performed to minimize this bias. This limitation is also offset by the larger sample size from the NIS and the absence of reporting bias introduced by selective publication of results from specialized centers. We cannot exclude that confounding variables may have impacted our results. Data about procedural technique, anticoagulation used, medications, and type of AF (ie, paroxysmal or persistent) were unavailable in the NIS. Late complications like pulmonary vein stenosis and atrio-esophageal were unavailable for analysis since they do not typically arise during an index hospitalization.