Abstract
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.
