Serial lung function testing in patients treated with Amiodarone: A prospective study

purpose: Amiodarone has proven to be effective in many cases of cardiac arrhythmias, refractory ventricular tachycardia, and ventricular fibrillation. Pulmonary toxicity is a possible side effect of the drug, with a reported incidence of 2 to 15 percent per year. To determine the effect of amiodarone on lung function, we prospectively studied serial lung function tests in a cohort of 91 patients with refractory cardiac arrhythmias treated with this agent. patients and methods: Spirometry and carbon monoxide diffusing capacity (DL_CO) were measured at zero, three, six, 12, 18, and 24 months, with a mean follow-up of 351 days. results: For the whole population taking a mean dose of amiodarone of 367 mg daily (range: 136 to 512 mg), there was no accelerated rate of decline in spirometric induces or DL_CO. Analysis of lung function changes by multivariate analysis demonstrated that an accelerated decline in DL_CO values occurred in elderly patients (p <0.05) but not in patients with pre-existing lung disease or cigarette smokers. In four patients (4.5 percent), clinical evidence of amiodarone pulmonary toxicity developed that was associated with a fall in DL_CO of greater than 20 percent. All four patients recovered after the drug was stopped. Another 15 patients, without clinical evidence of pulmonary toxicity, had a sustained decline in DL_CO of greater than 20 percent. These 15 patients remained assymptomatic over the next 11 months without interruption of therapy. A greater than 20 percent fail in DL_CO was a sensitive test for clinically evident amiodarone pulmonary toxicity, but had a positive predictive value of only 21 percent. conclusion: An isolated fall in DL_CO in the absence of clinical evidence of toxicity, does not necessitate stopping amiodarone. An unchanged DL_CO value appears to be a reliable negative predictor of pulmonary toxicity.