Urokinase Dissolution of a Right Atrial Thrombus

To the Editor.—May and coworkers1reported a case of successful streptokinase therapy of a right atrial thrombus associated with a temporary pacemaker placement. We report a case of successful urokinase (Abbokinase) therapy of a right atrial thrombus associated with a permanent pacemaker placement. Our patient had been included in a comparative trial of tissue plasminogen activator (Activase) and urokinase (Abbokinase) in the treatment of pulmonary embolism. During this patient's evaluation, a large, mobile right atrial thrombus was detected by Doppler echocardiogram. In accordance with the pulmonary embolism protocol, this patient received a 2000 U/lb bolus and a maintenance infusion of 2000 U/lb of urokinase over a 30-hour period, followed by systemic heparinization. Following the urokinase infusion, a repeated Doppler echocardiogram revealed complete lysis of the right atrial thrombus.2 According to May and coworkers, their discovery of the right atrial thrombus was fortuitous. In a sense, our discovery was