In this issue, Rich et al present findings that strengthen the evidence for a causal role of air pollution in triggering arrhythmias among patients with implanted cardioverter defibrillators.¹ The use of objective health and exposure data in conjunction with the chosen case-crossover approach underscores the power of “quasi experimental” epidemiological research in this field. Based on only 139 ventricular arrhythmias (VA) recorded on implantable cardioverter defibrillators among 56 patients, the investigators found statistically significant associations between markers of acute exposure to air pollution and arrhythmias. Associations with the 24 hour mean concentrations prior to the event were stronger than with both shorter (6 and 12 hour) and longer (48 hour) time windows.

The mechanisms linking ambient pollution with arrhythmias remain to be elucidated. However, the plausibility and evidence for effects of pollutants on autonomic function are steadily increasing.² In a series of experiments, exposure of dogs to concentrated ambient particles led to cardiac and respiratory changes mediated via both the sympathetic nervous system and the vagus nerve.³ A recent controlled experiment in humans …