Adenosine triphosphate stress myocardial contrast echocardiography detects coronary artery stenosis with greater sensitivity than wall-motion abnormality measurements

Quantitative assessment of microcollateral recruitment during coronary occlusion using real-time intravenous myocardial contrast echocardiography

BACKGROUND

Residual collateral-derived myocardial blood flow (MBF) (A x beta) is important to protect against myocardial ischemia after acute coronary occlusion.

METHODS

Recruitment of microcollateral was assessed in 22 dogs with left circumflex coronary artery occlusion by analysis of MBF and regional wall thickening (WT) using real-time myocardial contrast echocardiography.

RESULTS

Video intensity and WT at the center of risk area were significantly lower than those at the border of risk area. The video intensity, A value, beta value, and MBF correlated well with WT after left circumflex coronary artery occlusion. The WT of the area with above 25% of normal MBF was preserved and was higher than that at below 25%. However, the deterioration of WT was not distinguished according to A value.

CONCLUSION

Real-time myocardial contrast echocardiography is a useful noninvasive method to evaluate collateral-derived MBF, which can be a reliable index of protection against myocardial ischemia.

Vascular lesions and s-thrombomodulin concentrations from auricular arteries of rabbits infused with microbubble contrast agent and exposed to pulsed ultrasound

Arterial injury resulting from the interaction of contrast agent (CA) with ultrasound (US) was studied in rabbit auricular arteries and assessed by histopathologic evaluation and s-thrombomodulin concentrations. Three sites on each artery were exposed (2.8 MHz, 5-min exposure duration, 10-Hz pulse repetition frequency, 1.4-mus pulse duration) using one of three in situ peak rarefactional pressures (0.85, 3.9 or 9.5 MPa). Saline, saline/CA, and saline/US infusion groups (n = 28) did not have histopathologic damage. The saline/CA/US infusion group (n = 10) at exposure conditions below the FDA mechanical index limit of 1.9 did not have histopathologic damage, whereas the saline/CA/US infusion group (n = 9) at exposure conditions above the FDA limit did have damage (5 of 9 arteries). Lesions were characteristic of acute coagulative necrosis. Mean s-thrombomodulin concentrations, a marker for endothelial cell injury, were highest in rabbits exposed to US at 0.85 and 3.9 MPa, suggesting that vascular injury may be physiological and not accompanied by irreversible cellular injury.

Detection of significant stenotic lesions in the left anterior descending coronary artery using adenosine triphosphate stress strain imaging: comparison with coronary flow velocity reserve measurement using transthoracic Doppler echocardiography

To evaluate the usefulness of adenosine triphosphate stress strain imaging for detecting significant coronary artery disease in the left anterior descending coronary artery (LAD), 34 patients underwent coronary flow velocity reserve measurement in the distal LAD and adenosine triphosphate stress strain imaging simultaneously. Time to peak strain (TPS) was measured in the apical septal segment. TPS ratio was obtained as the ratio between TPS at adenosine triphosphate stress and at baseline. TPS ratio in 11 patients with LAD lesions was significantly greater than that in 23 patients without LAD lesions (1.24 +/- 0.17 vs 0.92 +/- 0.12, respectively, P < .0001). With a cut-off value greater than or equal to 1.1 for the TPS ratio and less than 2.0 for the coronary flow velocity reserve, diagnostic accuracy for the presence of significant LAD lesions were 88% and 82%, respectively. In conclusion, strain imaging can differentiate ischemic and nonischemic myocardium accurately comparable with coronary flow velocity reserve measurement.

Corrected quantification method to determine myocardial blood flow using real-time myocardial contrast echocardiography

BACKGROUND

The quantitative assessment of myocardial blood flow using real-time myocardial contrast echocardiography is based on a replenishment of bubble density after bubble destruction by high-power ultrasound exposure (burst). However, all microbubbles in the myocardial vessels are not necessarily completely destroyed, which results in unreliable data of the replenishment curve analysis.

OBJECTIVE

The aim of this study was to propose a corrected equation for the replenishment curve analysis based on the hypothesis in which the initial intensity just after burst should be equivalent to the baseline intensity before contrast infusion, and to examine whether the regional difference of myocardial perfusion parameters could be minimized by the use of corrected equation of replenishment curve.

METHODS

Myocardial opacification of the left ventricular short-axis view was observed using low mechanical index during infusion of Definity in open-chest dogs. Bubble destruction was set in two ways, either high (0 dB) or low (-11 dB) power burst. The videointensity (VI) of baseline before contrast infusion (f-value) was assumed as an initial intensity after complete bubble destruction. Changes of the VI after burst were fitted to both exponential functions: y = a (1 - e(-beta t)) + c (conventional equation) and y = a (1 - e(-beta(t - d))) + f (corrected equation). The c-value was the measured VI just after burst. The d-value was the hypothetical time of onset of the replenishment curve if all bubbles were completely destroyed. The plateau VI was defined as the A-value, which was the sum of a- and c-values or a- and f-values, respectively. The maximal difference of beta-value among myocardial regions was calculated by either equation.

RESULTS

The A-value was almost identical in either equation regardless of the acoustic power of burst. The beta-value by the conventional equation was higher after the incomplete burst than that after complete burst (0.45 +/- 0.12 vs 0.54 +/- 0.16). By contrast, the beta-value calculated by the corrected equation was almost identical despite complete or incomplete bursts (0.46 +/- 0.13 vs 0.48 +/- 0.15). The maximal difference of beta-value was significantly reduced by the use of corrected equation (conventional 0.24 +/- 0.14 vs corrected 0.18 +/- 0.10).

CONCLUSIONS

Variation of beta-value because of the incomplete bubble destruction can be minimized by using the corrected equation: y = a (1 - e(-beta(t - d))) + f. Further, the corrected equation can improve the regional variation of beta-value.