Background. Ischemia produces a sequence of events beginning with a decline in coronary flow reserve, myocardial perfusion abnormalities, and wall motion abnormalities. We hypothesized that low-dose dobutamine stress, combined with myocardial contrast echocardiography (MCE) and transthoracic Doppler echocardiography (TTDE), could detect myocardial ischemia preceding wall motion abnormalities according to this ischemic cascade. Methods. Ninety-six patients suspected of having stable angina pectoris underwent TTDE, MCE, and semi-quantitative dobutamine stress echocardiography (Semi-DSE). Wall motion was assessed using a scoring system. The contrast agent, Levovist, was injected intravenously to assess the coronary flow velocity (CFV) ratio in the left anterior descending coronary artery (LAD) and myocardial perfusion abnormalities in the LAD territory. The CFV ratio was calculated as the CFV during low-dose dobutamine stress divided by the baseline CFV. Time-intensity data for MCE were fitted for y = A (1-e-βt) from which the rate of the intensity rise (β) was calculated and the β ratio was derived at baseline and during stress. Results. Semi-DSE and low-dose dobutamine stress combined with TTDE and MCE were obtained successfully in 85 patients. The sensitivity and specificity of Semi-DSE for detecting ≥75% LAD stenosis were 79% and 93%, respectively. In the LAD territory, Semi-DSE showed 6 false negative and 4 false positive findings. However, failures of the CFV ratio and β ratio to increase >1.81 and >1.23 times that at baseline, respectively, indicated the presence of critical LAD stenosis, especially in 3 out of 6 false negative cases. Conclusions. Low-dose dobutamine stress combined with TTDE and MCE is a useful method for detecting critical LAD stenosis during Semi-DSE. This method overcomes the limitations of Semi-DSE.
Background. Myocardial perfusion can be measured by assessing the replenishment of bubbles destroyed by transient high power ultrasound waves (burst) during real-time myocardial contrast echocardiography (MCE). However, the burst procedure may destroy microbubbles in ventricular cavities as well as in the myocardium, which can interfere with the accurate measurement of myocardial perfusion. The goal of the present study was to determine the effect of burst exposure to the ventricular cavities on the replenishment curve parameters during real-time MCE. Methods. The myocardial opacification of the left ventricular (LV) short-axis view was observed using SIEMENS Sequoia-512 (mechanical index = 0.1) during infusion of Optison in 11 open-chest dogs. A 1-second or 6-second ultrasound burst was applied to the right ventricle (RV-burst), lateral wall (Myo-burst), or in the usual fashion (General-burst). The LV cavity was insonified by the General-burst but not by the RV-burst or Myo-burst. The time course of myocardial opacification of the lateral wall after burst was fitted to an exponential function: y=a(1-e-βt)+c. Results. Although the opacification inside the RV cavity recovered soon after RV-burst regardless of burst duration (1-second burst, 0.88±0.42 sec; 6-second burst, 0.82±0.37 sec), the recovery time of opacification inside the LV cavity was significantly prolonged after the 6-second RV-burst (1-second burst, 0.49±0.39 sec; 6-second burst, 4.30±1.14 sec). Further, in the General-burst, the β-value was significantly lower with the 6-second burst than with the 1-second burst (1-second burst, 0.29±0.10 vs. 6-second burst, 0.11±0.05). However, with the Myo-burst, the β-value was similar when comparing the two burst durations (1-second burst, 0.38±0.13 vs. 6-second burst, 0.35±0.09) Conclusions. In real-time MCE, the replenishment curve was significantly influenced by the burst procedure area, possibly due to bubble destruction in the ventricular cavities. However, this effect was minimized by the use of a short burst duration.
Postsystolic thickening is a highly sensitive marker of myocardial ischemia. We examined an open-chest dog with acute coronary occlusion to clarify whether the newly developed velocity vector imaging (VVI) could detect the extent of postsystolic thickening without angle-dependency. During coronary occlusion, the inward motion of the endocardium caused by postsystolic thickening could be clearly demonstrated in the ischemic region using VVI.
Described is a rare case of a saphenous vein bypass graft aneurysm late after surgery. Doppler echocardiography was useful in assessing the inflow and outflow patterns of the aneurysm and its complications.