Infusion versus bolus contrast echocardiography: A multicenter, open-label, crossover trial

Background In current practice, contrast echocardiography is performed with single or multiple bolus injections, which often result in an uncontrolled period of attenuation followed by transient left ventricular opacification (LVO). Because a "slow bolus" appears to reduce attenuation and prolong LV O, we hypothesized that a controlled infusion of contrast might provide a m ore uniform contrast effect with less attenuation and longer contrast durat ion. Methods and Results We sought to test the hypothesis by using an infusion o f contrast (DEFINITY [perflutren], The DuPont Pharmaceuticals Co, Medical I maging, North Billerica, Mass) that is stable when diluted in saline in a r andomized, multicenter, controlled, crossover trial. Sixty-four patients wi th poor noncontrast images were recruited at 3 centers and randomly assigne d to 2 single "slow" bolus injections of contrast (10 mu L/kg each over a p eriod of 30 to 60 seconds) or an infusion (1.3 mL in 50 mL normal saline in itially at 4.0 mL/min) of contrast. Patients then returned within 24 to 72 hours for the alternative form of contrast delivery. Three independent expe rienced echocardiographers viewed 30 seconds of videotape for all optimal b aseline and optimal contrast images to score LVO and qualitatively assessed endocardial border evaluability. The duration of adequate LVO then was ind ependently assessed by review of the entire videotape. Three independent so nographers traced single-frame, digitally captured images to measure the le ngth of the contiguous endocardial border visualized. Both bolus and infusi on administration demonstrated improved LVO (>90% by all blinded readers, P < .01) and endocardial border visualized (mean increase of 1.8 to 4.7 cm a t both end-diastole and end-systole, all P < .05) as compared with baseline images. However, contrast infusion resulted in a longer duration of LVO (r ange of mean durations for each reader, 158 to 174 seconds longer, P < .05) and a shorter duration of attenuation (18 to 54 seconds, P < .05) compared with either bolus injection. There were no severe adverse events with cont rast infusion. Conclusions Contrast echocardiography delivered as an infusion optimizes th e contrast effect by decreasing the attenuation period, extending the LVO d uration, and providing a uniform contrast effect that may be useful in obta ining multiple echocardiographic views, stress echocardiography, myocardial perfusion imaging, and applications in which blood flow must be quantified .