Do Inhaled Anticholinergics Increase or Decrease the Risk of Major Cardiovascular Events? A Synthesis of the Available Evidence

There has been recent uncertainty about whether the inhaled anticholinergic agents ipratropium bromide and tiotropium bromide increase or decrease cardiovascular risk in the treatment of patients with chronic obstructive pulmonary disease (COPD). This article synthesizes the available data in order to understand the controversy. COPD is a common cause of hospitalizations and is a rapidly increasing cause of mortality worldwide. Despite the heavy burden of COPD-related illness, the leading cause of hospitalization in COPD, patients is cardiovascular disease. This link between COPD and cardiovascular disease is in part due to the fact that both diseases share common risk factors, such as tobacco smoking and advanced age. It is also hypothesized that systemic inflammation in COPD increases the risk for cardiac events such as myocardial infarction. Inhaled anticholinergics reduce COPD-related hospitalizations and respiratory deaths compared with placebo, and tiotropium bromide is more effective than ipratropium bromide. In randomized trials, patients receiving tiotropium bromide have lower discontinuation rates than those receiving placebo and, therefore, contribute more person-years to the analyses. In a recent large 4-year tiotropium bromide trial, the proportion of patients who died was similar in the tiotropium bromide and placebo groups, whereas the death rate per person-years was lower with tiotropium bromide, indicating longer overall survival. There has been conflicting evidence concerning cardiovascular risk associated with inhaled anticholinergics. One meta-analysis found that the risk for major cardiovascular events was higher with anticholinergics compared with placebo or active comparator controls, whereas two subsequent meta-analyses that included new trial data found no difference in risk. In a recent pooled safety analysis, when incidence rates of events over time were evaluated, tiotropium bromide was associated with a lower rate of major cardiovascular events and cardiovascular deaths compared with placebo. This risk reduction was mainly because of a reduction in serious cardiac events such as myocardial infarction and congestive heart failure. In conclusion, inhaled anticholinergics, especially tiotropium bromide, reduce COPD-related hospitalizations and deaths, and may improve total survival over time. Many COPD patients have concomitant cardiovascular disease processes. Thus, trials may observe more cardiovascular events associated with anticholinergics than with placebo, but this differential is eliminated when evaluating the rate of events per person-years of exposure. New evidence indicates that tiotropium bromide may actually reduce the incidence of cardiovascular events and deaths over time. It is possible that the reduction in respiratory morbidity could improve functional status and reduce adverse cardiac outcomes over time. Further studies are needed to address this important issue.