Assessment of Transmural Distribution of Myocardial Perfusion With Contrast Echocardiography

Abstract

Background-We hypothesized that by using our newly defined method of destroying microbubbles and measuring their rate of tissue replenishment, we could assess the transmural distribution of myocardial perfusion. Methods and Results-We studied 12 dogs before and after creation of left anterior descending coronary artery stenoses both at rest and during hyperemia (nϭ62 stages). Microbubbles were administered as a constant infusion, and myocardial contrast echocardiography (MCE) was performed with the use of different pulsing intervals. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: yϭA(1Ϫe ␤t ), where A reflects microvascular cross-sectional area (or myocardial blood volume), and ␤ reflects mean myocardial microbubble velocity. The product A ⅐ ␤ represents myocardial blood flow (MBF). Average values for these parameters were derived from the endocardial and epicardial regions of interest placed over the left anterior descending coronary artery bed. Radiolabeled microsphere-derived MBF was also measured from the same regions. There was poor correlation between radiolabeled microsphere-derived MBF and A-endocardial/epicardial ratios (EER) (rϭ0.46). The correlation with ␤-EER was better (rϭ0.69, PϽ0.01). The best correlation with radiolabeled microsphere-derived MBF-EER was noted with A ⅐ ␤-EER (rϭ0.88, PϽ0.01). Conclusions-The transmural distribution of myocardial perfusion can be accurately assessed with MCE with the use of our newly described method of tissue replenishment of microbubbles after their ultrasound-induced destruction. In the model studied, an uncoupling of the transmural distribution of MBF and myocardial blood volume was observed during reversal of the MBF-EER. (Circulation. 1998;98:1912-1920.)

Combined Assessment of Myocardial Perfusion and Regional Left Ventricular Function by Analysis of Contrast-Enhanced Power Modulation Images

“…Perfusion was quantified with mean pixel intensity and contrast replenishment rate. Although the former parameter has been used previously, the latter had required repeated image acquisitions at variable pulsing intervals, 12,23 which made both data acquisition and analysis complicated and time-consuming. In contrast, the use of PMI with high-energy ultrasound pulses allowed this index to be measured from a single image acquisition.…”

“…9 Despite creative approaches and promising results, quantification or even imaging of myocardial perfusion has required extensive offline analysis, 10 remaining a goal of future research, 4,6,11,12 and the assessment of LV function with contrast remains subjective. No established technique for automated endocardial border detection and quantification of either global or regional LV function is applicable to contrast-enhanced images.…”

A Spatio-temporal Analysis of Contrast Ultrasound Image Sequences for Assessment of Tissue Perfusion

“…In future work the method will be tested on patients with proven coronary stenosis to show that the method detects regions where an infarct might have occurred. Comparison with manual semi-quantitative ROI techniques as used in [9] will also be done.…”

Quantitative Myocardial Contrast Echocardiography in Coronary Artery Disease

“…The velocity of blood in the coronary vessels is related to the size of the vessels and the level of the capillary (mean length 0.5 mm and mean diameter 7 m); the mean red cell velocity at rest is about 1mm s -1 [19]. For quantitative analysis, microbubbles were continuously infused, and MCE was performed using different pulsing intervals [13,22,23]. The contrast intensity (CI) versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function ( Figure 3); CI(t) = A(1-exp -t ), where A represents the intensity of full myocardial replenishment and reflects myocardial blood volume, and represents the rate constant of intensity change and reflects mean myocardial bubble velocity.…”

“…In the experimental model of coronary stenosis, color-coded images of each parameter can be successfully displayed and we can spatially characterize myocardial perfusion dynamics in the myocardium [22]. The transmural distributions of myocardial blood flow and myocardial blood volume are not coupled in the presence of coronary stenosis either at rest or either hyperemia.…”