Quantitation of myocardial perfusion by contrast echocardiography: Analysis of contrast gray level appearance variables and intracyclic variability

AbstractHand-agitated diatrizoate meglumine/diatrizoate sodium (MD-76) was injected above the aortic valve in seven dogs during two-dimensional echocardiographic imaging to determine the ability of contrast appearance variables (i.e., peak background-subtracted gray level intensity, time to peak contrast appearance and maximal slope of the contrast appearance curve) to predict myocardial blood flow. Regional perfusion was altered by a critical coronary stenosis (around the left anterior descending coronary artery) or by administering intracoronary adenosine (into the left circumflex coronary artery), or both. Changes in regional blood flow between control and interventions were compared with the changes in the contrast appearance variables. In addition, the ability of intracyclic variability of gray level intensity to predict myocardial perfusion was assessed.In the determination of absolute myocardial perfusion, background-subtracted peak gray level intensity and the maximal slope of the appearance curve demonstrated a fair correlation (r = 0.67 and 0.51, respectively, p < 0.0001). However, time to peak contrast appearance did not correlate (r = 0.14, p = 0.31). Intracyclic variability of gray level intensity at control (before contrast injection) and after contrast injection also did not correlate with perfusion (r = 0.18 and 0.06, respectively). In the evaluation of relative changes in myocardial blood flow, the percent change in the maximal slope of the appearance curve correlated with the percent change in blood flow (r = 0.77, p < 0.0001). Seven of the eight regions with >3.5-fold increase in blood flow were identified by an increase in maximal slope of >50%.It is concluded that the percent change in the maximal slope of the contrast appearance curve correlates linearly with the percent change in blood flow and may permit the identification of regions with normal coronary flow reserve (i.e., >3.5-fold increase in coronary blood flow)