Intermittent Harmonic Imaging Research Articles

Simultaneous Assessment of Wall Motion and Myocardial Perfusion Using a Rapid Acquisition Intermittent Harmonic Imaging Pulsing Interval of 5-15 Hertz Following Acute Myocardial Infarction and During Stress Echocardiography

Simultaneous Assessment of Wall Motion and Myocardial Perfusion Using a Rapid Acquisition Intermittent Harmonic Imaging Pulsing Interval of 5-15 Hertz Following Acute Myocardial Infarction and During Stress Echocardiography

Myocardial Perfusion Characteristics and Hemodynamic Profile of MRX-115, a Venous Echocardiographic Contrast Agent, During Acute Myocardial Infarction

We sought to determine whether MRX-115, a new venous echocardiographic contrast agent, could accurately assess risk area during coronary occlusion and infarct size after reperfusion by using novel imaging modalities meant to selectively enhance contrast signals. In 12 open-chest dogs, venous injections of 0.5 ml of MRX-115 were performed during baseline and coronary occlusion and after reperfusion in the presence of exogenous hyperemia. Ultrasound was transmitted at 2 MHz and received at both 2 MHz (fundamental) and 4 MHz (harmonic) frequencies during continuous and intermittent (end-systolic only) imaging. The risk area during coronary occlusion was compared with technetium autoradiography, and the infarct size after reperfusion was compared with postmortem tissue staining. MRX-115 produced no alterations in hemodynamic or pulmonary gas exchange at any stage. During continuous (both fundamental and harmonic) and intermittent fundamental imaging, measurements of perfusion defects were precluded in many dogs by either poor signal enhancement or posterior wall attenuation. By comparison, these measurements were possible during intermittent harmonic imaging in all dogs except one, which had a very small infarction during reflow. Correlation analysis between perfusion defect size on intermittent harmonic imaging and either autoradiographic risk area or postmortem infarct size gave r values of 0.83 and 0.92, respectively. We conclude that MRX-115 is hemodynamically well tolerated and, when imaging is performed after venous injection, can accurately assess regions of hypoperfusion when combined with intermittent harmonic imaging. These results are promising for the use of this approach in patients with acute myocardial infarction. (J Am Soc Echocardiogr 1998;11:36–46)

Simultaneous assessment of wall motion and myocardial perfusion using a rapid acquisition intermittent harmonic imaging pulsing interval of 5–15 hertz following acute myocardial infarction and during stress echocardiography

Simultaneous assessment of wall motion and myocardial perfusion using a rapid acquisition intermittent harmonic imaging pulsing interval of 5–15 hertz following acute myocardial infarction and during stress echocardiography

Effect of Significant Two-Vessel Versus One-Vessel Coronary Artery Stenosis on Myocardial Contrast Defects Observed With Intermittent Harmonic Imaging After Intravenous Contrast Injection During Dobutamine Stress Echocardiography

Objectives. We sought to determine the effect of multivessel as opposed to single-vessel coronary artery stenosis on myocardial contrast defects observed with intermittent harmonic imaging and intravenous perfluorocarbon-exposed sonicated dextrose albumin contrast injection.Background. Intermittent harmonic imaging has permitted the detection of myocardial perfusion abnormalities with an intravenous ultrasound contrast agent. The effect of multivessel disease on inducibility of these perfusion abnormalities is unknown.Methods. In 10 dogs, intravenous injections of contrast agent were given at rest and during dobutamine stress echocardiography when a single coronary artery stenosis was present (≥50% diameter by quantitative angiography) and again when a second stenosis (range 44% to 92% diameter) was present in the vessel supplying the adjacent perfusion bed. The peak myocardial contrast was visually and quantitatively assessed in the mid and lateral regions of the perfusion bed of the first stenosis (original stenosis zone) in the presence of one- and two-vessel stenosis.Results. Peak myocardial contrast defects in both the mid and lateral segments of the original stenosis zone during dobutamine stress echocardiography was significantly lower when two-vessel stenosis was present (p = 0.015), especially in the lateral segment. The spatial extent of the perfusion defect in the original stenosis zone risk area increased significantly when two-vessel stenosis was present, and correlated closely with actual risk area (r = 0.99). Previous total occlusion followed by reperfusion of the vessel supplying the original stenosis zone significantly increased the amount of collateral activity between perfusion beds.Conclusions. Collateral flow limits the spatial extent of inducible ischemia within the risk area of single-vessel stenosis. Restoring blood flow to one perfusion bed reduces the extent of a perfusion abnormality that can be induced in an adjacent stenosed bed.

Smaller intravenous perfluorocarbon-containing microbubbles produce greater myocardial contrast with intermittent harmonic imaging and better delineation of risk area during acute myocardial ischemia

The purpose of this article was to determine whether applying negative or positive pressure to perfluorocarbon-containing microbubbles before intravenous injection would improve the myocardial contrast when using newer imaging techniques such as harmonic and intermittent imaging. Perfluorocarbon-containing microbubbles were exposed to sustained negative or positive pressure before intravenous injection in 10 dogs. Microbubble size distribution and concentration were measured after each exposure. Peak myocardial videointensity with intermittent harmonic imaging with each sample was compared. Microbubbles exposed to –200 mm Hg pressure before intravenous injection produced both the highest concentration of microbubbles and greater numbers of microbubbles less than 4 μm. Peak myocardial videointensity did not correlate with microbubble concentration or size but did correlate with the absolute number of microbubbles <4 μm (mean r value 0.76, range 0.61 to 0.90). Risk area was best visualized with perfluorocarbon-containing microbubble samples containing the smallest microbubbles. We conclude that the myocardial contrast observed with perfluorocarbon-containing microbubbles can be enhanced by applying negative pressure before injection. The mechanism for this improved contrast appears to be related to creation of smaller microbubbles. (J Am Soc Echocardiogr 1997;10:792-7.)

Safety and efficacy of QW7437, a new fluorocarbon-based echocardiographic contrast agent

The aim of this study was to evaluate the safety and efficacy of QW7437, a new fluorocarbon-based transpulmonary myocardial echocardiographic contrast agent. QW7437 is an anionically charged 2% dodecafluoropentane emulsion molecule, similar to EchoGen, a contrast agent previously shown to be efficacious in providing myocardial opacification by means of venous injection. This new agent has theoretical potential to provide greater safety and efficacy as a result of (1) reduced adherence to the negatively charged vascular endothelium and (2) reduced microbubble coalescence. Myocardial contrast echocardiography was performed in 10 dogs to evaluate the safety and efficacy of this agent. QW7437 (0.05 ml/kg) was injected as an intravenous bolus during intermittent harmonic epicardial imaging. Hemodynamic variables including heart rate, blood pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output, and arterial blood gases were determined at baseline and serially after contrast administration. Left ventricular fractional area shortening and regional myocardial blood flow at rest and during hyperemia (adenosine 140 μg/kg/min) were measured before and after contrast echocardiography. QW7437 provided dense myocardial opacification which persisted for more than 2 minutes in all subjects. This prolonged contrast effect did not result in significant changes in any hemodynamic variables, left ventricular function, or myocardial blood flow. Future studies should address the potential of this agent for human use. (J Am Soc Echocardiogr 1997;10:798-804.)

Detection of coronary stenoses using venous injection of FS-069 with intermittent harmonic imaging: Christian Firschke MD, Jonathan R. Lindner MD, Kevin Wei, MD, N. Craig Goodman, BS, Sanjiv Kaul, MD. University of Virginia, Charlottesville, Virginia

Detection of coronary stenoses using venous injection of FS-069 with intermittent harmonic imaging: Christian Firschke MD, Jonathan R. Lindner MD, Kevin Wei, MD, N. Craig Goodman, BS, Sanjiv Kaul, MD. University of Virginia, Charlottesville, Virginia