Air pollution episodes have been associated with increased cardiovascular hospital admissions and mortality in time-series studies. We tested the hypothesis that patients with implanted cardioverter defibrillators experience potentially life-threatening arrhythmias after such air pollution episodes. We compared defibrillator discharge interventions among 100 patients with such devices in eastern Massachusetts, according to variations in concentrations of particulate matter, black carbon, and gaseous air pollutants that were measured daily for the years 1995 through 1997. A 26-ppb increase in nitrogen dioxide was associated with increased defibrillator interventions 2 days later (odds ratio = 1.8; 95% confidence interval = 1.1–2.9). Patients with ten or more interventions experienced increased arrhythmias in association with nitrogen dioxide, carbon monoxide, black carbon, and fine particle mass. These results suggest that elevated levels air pollutants are associated with potentially life-threatening arrhythmia leading to therapeutic interventions by an implanted cardioverter defibrillator.
Particulate air pollution episodes have been associated with increased hospital admissions for cardiovascular disease 1–4 and increased cardiovascular mortality 5–11 in epidemiologic studies. Persons with underlying heart disease appear to be at increased risk for the adverse health effects of particulate air pollution. 1–11
Controlled exposure of animals and natural exposures of humans to particulate pollution have shown possible effects of air pollution on the heart. Instillation of 250 micrograms of combustion particles into the lungs of rats with pharmacologically induced pulmonary hypertension produced arrhythmia and doubled their mortality rate. 12 Dogs inhaling concentrated ambient particles showed changes in heart rate variability and electrocardiographic morphology consistent with increased sympathetic nervous system activity. 13,14 Heart rates of elderly subjects in Utah Valley increased in association with elevated concentrations of inhalable particulates (particulate matter less than 10 micrometers in aerodynamic diameter; PM10). 15 In a subset of these subjects, heart rate variability decreased with increasing PM10 concentrations. 15 Increased heart rate and decreased heart rate variability are indicators of altered autonomic control, specifically increased sympathetic stress. Raised sympathetic activity increases the risk of ventricular fibrillation, a severe form of arrhythmia that, without intervention, leads to sudden death. 16
We tested the hypothesis that patients with a history of serious arrhythmia requiring implanted cardioverter defibrillators (ICDs) would experience potentially life-threatening arrhythmia associated with air pollution episodes. Traditionally, ventricular arrhythmia is treated with drug therapies. 17 Implantable cardioverter defibrillators monitor electrocardiographic abnormalities and initiate therapeutic interventions. On detection of ventricular fibrillation or ventricular tachycardia, the ICD device will initiate pacing and/or shock therapy to restore a normal cardiac rhythm. Several recent clinical trials have suggested that ICD devices are more effective at preventing death from heart rhythm abnormalities than medications alone. 18,19 The ICD devices provide objective and accurate records of the occurrence and timing of arrhythmic events. We report the results of a pilot study to assess the feasibility of linking cardiac arrhythmias detected by ICD devices with air pollution exposures.