971-55 Can Regional Myocardial Tissue Blood Flow be Measured in Terms of ml/min/g Using Contrast Echocardiography?

Abstract

Absolute quantification of regional myocardial tissue blood flow (RMBF) based on contrast echocardiography has not yet been achieved. The aim of this study was to validate of our recently proposed algorithm for the quantification of RMBF and examine its reproducibility. This approach evaluates RMBF as the intravascular volume fraction (ratio of the areas under myocardial time intensity curve and a curve obtained from a reference region of interest) divided by mean transit time (obtained using deconvolution of impulse response). Experiments were carried out using an isolated rabbit heart model (N = 8), wherein coronary blood flow was controlled by varying perfusion pressure. Factors confounding in-vivo experimentation, such as cardiac translation and limited image quality, were eliminated in this setup. Aortic root injections of FS069, a new stable contrast solution (MBI, 1:200 in saline, filtered using a 8 /μ-pore filter) and colored microspheres, used as the “gold” standard for reference, were performed at different levels of coronary flow. During contrast injections, end-diastolic images of the heart and an extracardiac reference chamber were acquired using a 7.5 MHz transducer and digitized on-line and processed using the above algorithm. Contrast echocardiographic measurements of RMBF highly correlated with microsphere flow (figure). Bland-Altman analysis revealed an insignificant bias of 0.07 ml/min/gr, with 95% limits of agreement at 0.69 ml/min/g. Using this algorithm, repeated evaluations of RMBF were highly reproducible (r = 0.92). In summary, the use of this new algorithm in conjunction with stable contrast agents, such as FS069, allows accurate and reproducible quantification of RMBF.