Destruction of Microbubbles in the Ventricular Cavities Affects the Quantitative Assessment of Myocardial Perfusion During Real-time Myocardial Contrast Echocardiography

Abstract

Background. Myocardial perfusion can be measured by assessing the replenishment of bubbles destroyed by transient high power ultrasound waves (burst) during real-time myocardial contrast echocardiography (MCE). However, the burst procedure may destroy microbubbles in ventricular cavities as well as in the myocardium, which can interfere with the accurate measurement of myocardial perfusion. The goal of the present study was to determine the effect of burst exposure to the ventricular cavities on the replenishment curve parameters during real-time MCE.Methods. The myocardial opacification of the left ventricular (LV) short-axis view was observed using SIEMENS Sequoia-512 (mechanical index = 0.1) during infusion of Optison in 11 open-chest dogs. A 1-second or 6-second ultrasound burst was applied to the right ventricle (RV-burst), lateral wall (Myo-burst), or in the usual fashion (General-burst). The LV cavity was insonified by the General-burst but not by the RV-burst or Myo-burst. The time course of myocardial opacification of the lateral wall after burst was fitted to an exponential function: y=a(1-e-βt)+c.Results. Although the opacification inside the RV cavity recovered soon after RV-burst regardless of burst duration (1-second burst, 0.88±0.42 sec; 6-second burst, 0.82±0.37 sec), the recovery time of opacification inside the LV cavity was significantly prolonged after the 6-second RV-burst (1-second burst, 0.49±0.39 sec; 6-second burst, 4.30±1.14 sec). Further, in the General-burst, the β-value was significantly lower with the 6-second burst than with the 1-second burst (1-second burst, 0.29±0.10 vs. 6-second burst, 0.11±0.05). However, with the Myo-burst, the β-value was similar when comparing the two burst durations (1-second burst, 0.38±0.13 vs. 6-second burst, 0.35±0.09)Conclusions. In real-time MCE, the replenishment curve was significantly influenced by the burst procedure area, possibly due to bubble destruction in the ventricular cavities. However, this effect was minimized by the use of a short burst duration.