Hospitalizations for arrhythmia include atrial, ventricular, and asystolic events, although atrial fibrillation has been the most common primary discharge diagnosis, at least among prevalent dialysis patients in 2011. The rate of hospitalization with arrhythmia as the primary discharge diagnosis was constant during the study era among both incident and prevalent dialysis patients. In contrast, admissions with arrhythmia as either the primary or leading secondary discharge diagnosis exhibited a substantial decline before the advent of MS-DRGs. This can be attributed almost exclusively to less intensive coding of atrial fibrillation (ICD-9-CM diagnosis code 427.31). In fact, the diagnosis of atrial fibrillation not only evaporated in the leading secondary discharge diagnosis slot, but declined meaningfully in all of the first four secondary slots. This begs the question of whether more than incidence of the most severe cases of arrhythmia can be reliably estimated from Medicare claims; this is certainly a topic that merits further analysis in subsequent reports. Also among incident patients, it is noteworthy that the admission rate for arrhythmia as the principal diagnosis during the first three months of dialysis actually increased between the annual cohorts in 2003 and 2010.
There is substantial regional variation in the rate of hospitalization for arrhythmia, particularly during the first year of dialysis among incident patients. Seasonality of arrhythmia admissions is not apparent.
Several issues related to arrhythmia merit further exploration, such as the timing of events across days of the dialysis week, the risk of hyperkalemia during the long interdialytic interval, and the risk of post-dialysis hypokalemia and other iatrogenic electrolyte changes. Foley et al reported an increased risk of hospitalization and death on the first day of the dialysis week (NEJM). Unknown is whether these events occur predominantly before or after dialysis. Either could be the case, and each pose different challenges. If the apparent risk manifests before dialysis, hyperkalemia is the likely issue; this could be investigated by determining if the condition appears as a leading secondary diagnosis. If, however, the apparent risk manifests after dialysis, metabolic changes during treatment need to be considered.
There are also concerns about the use of low potassium dialysis baths (K ≤ 2.0) for patients with pre-potassium levels less than 5.0 mEq/L, and about the relatively low magnesium level (0.75–1.0 mEq/L), which has not changed for more than 30 years. A recent study in Japan found that lower pre-dialysis serum magnesium is associated with a higher risk of death, suggesting that more analyses are needed to determine an effective and safe level. The level of calcium in the dialysate should also be examined, particularly among patients using calcium-containing phosphate binders. Baths in which the calcium level is less than 2.5 mg/dL may cause prolonged QT intervals, potentially increasing the risk of arrhythmia and sudden cardiac death.