Diagnostic and Therapeutic Applications of Ultrasound Contrast Agents

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Citation
US Cardiology 2006;2005:2(1):93-93

Although ultrasound contrast agents (microbubbles) in the US have been primarily approved for improving left ventricular opacification, there are emerging applications that could significantly increase their utilization. With newer microbubble detection methods, ultrasound contrast agents are being utilized to detect myocardial perfusion (see Figure 1). Until now, this has been almost exclusively done with radionuclide tracers in patients, but large clinical studies have recently demonstrated the safety and clinical potential for myocardial perfusion imaging with ultrasound contrast agents.1-3 The resolution of myocardial contrast echocardiography (<2mm) is significantly better than radionuclide imaging (8-12mm). This permits myocardial contrast echocardiography to detect subendocardial perfusion defects that may otherwise go undetected by radionuclide imaging (see Figure 2). Perfusion imaging with echocardiography is also less costly, and can be performed at the patientÔÇÖs bedside. Myocardial perfusion imaging with intravenous ultrasound contrast agents in the emergency department has been shown to assist in ruling out acute coronary syndromes.2 A second, recently published, study demonstrated that myocardial perfusion imaging with ultrasound contrast agents during dobutamine stress echocardiography is significantly better than wall motion analysis in predicting patient outcome.3 A summary of the potential diagnostic applications of intravenous ultrasound contrast agents is shown in Table 1.

Microbubbles may also have therapeutic potential. Preclinical trials have demonstrated that ultrasound-mediated microbubble destruction can be used to target delivery of genes to the myocardium.4 Phase 1 clinical trials are under way exploring whether antisense oligonucleotides, which inhibit the c-myc protooncogene, can be selectively delivered to stented coronary artery segments with intravenous microbubbles. Microbubbles may also be used in combination with ultrasound to non-invasively dissolve intravascular thrombi without the need of a lytic agent.5 This may be especially useful in the treatment of acute stroke, and preclinical trials have demonstrated that transcranial ultrasound and intravenous targeted microbubbles can successfully recanalize intracranial thrombi.6 Ôûá

References
  1. Tsustui J et al., Safety of Dobutamine Stress Real-Time Myocardial Contrast Echocardiography, JACC (2005);45: pp. 1,235-1,242.
    Crossref | PubMed
  2. Leng Tong K et al.,Myocardial Contrast Echocardiography Versus Thrombolysis in Myocardial Infarction Score in Patients Presenting to the Emergency Department With Chest Pain and a Nondiagnostic Electrocardiogram, JACC (2005);46: pp. 920-927.
    Crossref
  3. Tsutsui J et al.,Prognostic Value of Dobutamine Stress Myocardial Contrast Perfusion Echocardiography, Circulation (2005);112: pp. 1,444-1,450.
    Crossref | PubMed
  4. Korpanty G et al.,Targeting of VEGF-mediated angiogenesis to rat myocardium using ultrasonic destruction of microbubbles, Gene Therapy (2005); pp. 1-8.
  5. Xie F et al., Effectiveness of Lipid Microbubbles and Ultrasound in Declotting Thrombosis, US Med. Biol. (2005);31: pp. 979-985.
    Crossref | PubMed
  6. Culp W et al., Intracranial Clot Lysis With Intravenous Microbubbles and Transcranial Ultrasound in Swine, Stroke (2004);35: pp. 2,407-2,411.
    Crossref | PubMed