Background: We hypothesized that the degree and spatial extent of blood flow mismatch in beds supplied by stenoses that are not flow-limiting at rest can be quantified with myocardial contrast echocardiography (MCE) using left atrial (LA) and right atrial (RA) injections of contrast during pharmacologically induced coronary hyperemia. Methods and Results: In 12 open-chest dogs, MCE was performed and myocardial blood flow (MBF) was measured by use of radiolabeled microspheres at baseline and during phenylephrine-induced coronary hyperemia. In the presence of this drug, stenoses were placed during different stages on the left anterior descending (LAD) and left circumflex (LCx) coronary arteries, and MCE and MBF assessments were performed. LA injections of 2 mL of 0.5 billion/mL microbubbles (mean diameter, 4.3 μm) were performed at each stage in all 12 dogs, and RA injections of 10 mL of 6 billion/mL microbubbles (mean diameter, 3.7 to 5.3 μm) were administered in 7 dogs. MCE images in which the contrast disparity between the LAD and LCs beds was maximal were digitally subtracted from precontrast images, and mean videointensities in these beds were measured after the dynamic range of gray-scale intensities was increased in the subtracted image and the image was color coded. The region showing hypoperfusion during LAD stenosis was planimetered and expressed as a percentage of the myocardial area in the short-axis. There was an excellent correlation between the LAD/LCx bed videointesity ratio and LAD/LCx bed MBF ration (y=0.5x+0.44, r=.91, P<.001) during 57 LA injections. There was also an excellent correlation between the hypoperfused bed size on NMCE during LA injection of contrast in the presence of LAD stenosis and the hypoperfused myocardium was determined by radiolabeled microspheres (y=0.8x+4.2, r=.90, P<.001, SEE-2.4, n=11). The anterior myocardium was opacified in 6 dogs receiving RA injections of contrast, and the hypoperfused area during LAD stenosis correlated closely with that determined by radiolabeled microspheres (y=0.86x + 3.4, r=.93, P<.01). Conclusions: Coronary stenoses, which are not flow limiting at rest, can be detected and the degree and spatial extent of blood flow mismatch during pharmacologically induced coronary hyperenemia can be quantified with MCE using LA and RA injections of contrast. Thus, it is possible that the severity of coronary stenoses and the quantum of myocardium in jeopardy could be quantified in the future with MCE using venous injection of contrast.
- blood flow
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)