In vivo characterization of murine myocardial perfusion with myocardial contrast echocardiography - Validation and application in nitric oxide synthase 3-deficient mice

Background-The ability to noninvasively evaluate murine myocardial blood flow (MBF) in vivo would provide an important tool for cardiovascular research. Myocardial contrast echocardiography (MCE) has been used to measure MBF; however, it has not been validated in mice. This study assesses whether MCE can evaluate MBF at rest and after vasodilation and measure the maximal augmentation ( coronary reserve) of MBF in mice. Wild-type (WT) and nitric oxide synthase 3 (NOS3)-deficient (NOS3(-/-) ) mice were studied. Methods and Results-MCE was performed at baseline and after intravenous infusion of acetylcholine or adenosine. Definity contrast agent was infused, and parasternal views were acquired in real-time mode. Replenishment curves of myocardial contrast were obtained, and rates of signal rise (beta) and plateau intensity ( A) were calculated. MBF estimated by the product of A and beta ( A beta) was compared with that measured with fluorescent microspheres. MCE analysis was feasible in 98% ( 52/53) of mice. MBF measured by microspheres increased with adenosine and correlated closely with A beta. There was no difference in MCE-derived MBF between WT and NOS3 (-/-) mice at rest. Adenosine infusion increased MBF by 3.0 +/- 0.6-fold in NOS3 (-/-) mice and 2.5 +/- 0.3-fold in WT ( P = 0.58 between genotypes). Acetylcholine induced an increase of 2.4 +/- 0.2-fold in MBF in WT mice but did not increase MBF in NOS3 (-/-) mice ( P < 0.0005 versus WT). Conclusions-MBF, coronary reserve, and vasodilator responses can be evaluated accurately in the intact mouse by MCE. This method demonstrated a preserved coronary response to adenosine but an impaired acetylcholine-induced vasodilation in NOS3 (-/-) mice compared with WT mice.