The purpose of this study was to determine in an in vitro model the effect of pulsatile pressure on the decay of echocardiographic contrast agents. Use of contrast agents for quantitative assessment of perfusion requires understanding of the factors controlling their rates of disappearance. Prior studies have shown that constant pressure affects the rate of disappearance of these agents. It is not known whether pulsatile pressure influences the rate of decay of contrast agents. In an in vitro chamber, three contrast agents (Albunex, hand-agitated saline solution, and hand-agitated Angiovist) were exposed to pulses of pressure at three rates (30, 60, and 120 pulsations/min), keeping pressure characteristics (peak, nadir, and mean) within a narrow range. Five injections were performed for each agent at each rate. Two-dimensional echocardiographic images of the effects of contrast material were recorded from injection until total disappearance. Videointensity was measured and time-intensity curves were generated. These curves of intensity decay were fitted to an exponential decay function (I=Ae^−λt) and the velocity of decay (λ) was used for comparisons. For all agents, intensity of contrast decreased over time. Saline solution and Angiovist, but not Albunex, showed pulsatile decreases in intensity of contrast with each peak pressure and partial recovery of contrast intensity with each nadir pressure. At each pulse rate, Albunex demonstrated a faster velocity of decay than did saline solution (p<0.007) (mean λ: 0.254 vs 0.044 at 30 pulsations/min, 0.427 vs 0.059 at 60 pulsations/min, and 0.936 vs 0.072 at 120 pulsations/min) and Angiovist (p<0.01) (0.254 vs 0.040 at 30 pulsations/min, 0.427 vs 0.051 at 60 pulsations/min, and 0.936 vs 0.076, at 120 pulsations/min). For every agent, an increase in the rate of decay was observed as the pulse rate was increased (λ at 30 and 120 pulsations/min: 0.254 vs 0.936, p<0.05 [Albunex]; 0.044 vs 0.072, p<0.05 [saline solution]; and 0.040 vs 0.076, p<0.05 [Angiovist]). Regression analysis demonstrated that the total time exposed to peak pressure was the dominant effect on contrast decay. Pulsatile pressure in this in vitro model influences echocardiographic contrast decay in two ways: (1) a cyclic decrease in contrast intensity at pressure peak accompanied by partial recovery of intensity at nadir pressure for saline solution and Angiovist and (2) an acceleration of contrast decay as cycle rate and the duration of exposure to peak pressure are increased. Therefore heart rate and pressure must be taken into account when comparing effects of echocardiographic contrast agents.