Background Perflenapent injectable emulsion is a newer echocardiographic contrast agent that provides chamber opacification and improved endocardial border delineation. In >1000 patients tested, adverse effects have been minimal. However, previous studies have included few patients with congestive heart failure (CHF) or severe chronic obstructive pulmonary disease (COPD). Because of their reduced cardiopulmonary reserve, these patients might be at greater risk for adverse events. Methods and Results The safety of perflenapent emulsion was evaluated in ambulatory patients with New York Heart Association class III to IV congestive heart failure (CHF) or severe obstructive pulmonary disease (COPD). In 2 separate multicenter, phase II, randomized, double-blind, placebo-controlled, single-administration clinical trials, 146 patients in the CHF study and 134 patients in the COPD study received either perflenapent emulsion or saline placebo during an echocardiographic examination. Perflenapent emulsion was well tolerated in patients with CHF or COPD. The adverse event rates with perflenapent emulsion (15%) were similar to those with saline (11%; P =.43) in the combined groups, and similar findings were seen when analyzed by CHF or COPD groups separately. All adverse events were rated as mild, required no treatment, resolved spontaneously, and left no sequelae. Changes from baseline in vital signs, pulse oximetry, electrocardiography, and laboratory tests were similar between treatment groups. Conclusions These data support the safety of perflenapent emulsion for contrast echocardiography in stable ambulatory patients with CHF or COPD. (Am Heart J 2000;139:1077-80.)