Quantification of myocardial perfusion with contrast echocardiography during venous injection of contrast

Quantification of changes in myocardial blood flow (MBF) and myocardial blood volume (MBV) with myocardial contrast echocardiography (MCE) depends critically upon identifying the linear portion of the relationship between microbubble concentration and measured videointensity. MBV and MBF are closely coupled during infusion of inotropes and with normal coronary arteries any increase in epicardial flow results in an increase in MBF. Increasing amounts of a contrast agent MRX-115 (12.5-300μl) was injected intravenously (IV) at baseline and during IV infusion of increasing amounts of adrenaline in 6 dogs with a flow probe around the left anterior descending (LAD) coronary artery. Intermittent harmonic MCE was performed gated to end-systole and peak video intensity measured over the LAD bed. Microbubble dose was plotted against peak background subtracted videointensity at baseline and during hyperaemia. From the linear ranges of these plotts a dose of 0.1 ml of contrast was selected for injection and kept constant for the remainder of the experiment. An excellent correlation was found between the peak myocardial background-subtracted video intensities in the LAD bed and the LAD flow rate (r=0.9, n=23 P<0.001) following identical injections of contrast. It is concluded that quantification of myocardial blood flow with MCE depends on a linear relation between microbubble concentration and videointensity. Due to differences in post processing, each echocardiographic system will need calibration to identify this linear range.