Jonathan R. Lindner

American College of Cardiology/European Society of Cardiology Clinical Expert Consensus Document on Hypertrophic Cardiomyopathy: a report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents and the European Society of Cardiology Committee for Practice Guidelines

A 29-year-old Dominican man with a history of intravenous heroin use and hepatitis C presented with a 5-day history of fever, dyspnoea, haemoptysis, pleuritic chest pain, abdominal pain, haematochezia and haematemesis. Initial physical examination was significant for scleral icterus, generalised abdominal tenderness to palpation, melaena and blood-tinged sputum. Blood cultures grew Fusobacterium species. CT scan of the chest revealed multiple bilateral cavitary features in lung fields. At the same time, a neck ultrasound performed demonstrated thrombophlebitis in the right internal jugular vein, confirming the diagnosis of ‘Lemierre’s syndrome’. Treatment was with antibiotics and supportive care for 6 weeks.

ACCF/ACG/AHA 2008 expert consensus document on reducing the gastrointestinal risks of antiplatelet therapy and NSAID use: A report of the American College of Cardiology Foundation Task Force on clinical expert consensus documents

ACCF TASK FORCE MEMBERS Robert A. Harrington, MD, FACC, Chair; Eric R. Bates, MD, FACC; Charles R. Bridges, MD, MPH, FACC; Mark J. Eisenberg, MD, MPH, FACC; Victor A. Ferrari, MD, FACC; Mark A. Hlatky, MD, FACC; Sanjay Kaul, MBBS, FACC; Jonathan R. Lindner, MD, FACC‡; David J. Moliterno, MD, FACC; Debabrata Mukherjee, MD, FACC; Richard S. Schofield, MD, FACC‡; Robert S. Rosenson, MD, FACC; James H. Stein, MD, FACC; Howard H. Weitz, MD, FACC; Deborah J. Wesley, RN, BSN

Microbubbles in medical imaging: current applications and future directions

Not all bubbles in the bloodstream are detrimental. During the past decade, contrast-enhanced ultrasound has evolved from a purely investigational tool to a routine diagnostic technique. This transformation has been facilitated by advances in the microbubble contrast agents and contrast-specific ultrasound imaging techniques. The ability to non-invasively image molecular events with targeted microbubbles is likely to be important for characterizing pathophysiology and for developing new therapeutic strategies in the treatment of cardiovascular and neoplastic diseases.

Imaging Tumor Angiogenesis With Contrast Ultrasound and Microbubbles Targeted to αvβ3

Background Angiogenesis is a critical determinant of tumor growth and metastasis. We hypothesized that contrastenhanced ultrasound (CEU) with microbubbles targeted to &agr;v‐integrins expressed on the neovascular endothelium could be used to image angiogenesis. Methods and Results Malignant gliomas were produced in 14 athymic rats by intracerebral implantation of U87MG human glioma cells. On day 14 or day 28 after implantation, CEU was performed with microbubbles targeted to &agr;v&bgr;33 by surface conjugation of echistatin. CEU perfusion imaging with nontargeted microbubbles was used to derive tumor microvascular blood volume and blood velocity. Vascular &agr;v‐integrin expression was assessed by immunohistochemistry, and microbubble adhesion was characterized by confocal microscopy. Mean tumor size increased markedly from 14 to 28 days (2±1 versus 35±14 mm2, P<0.001). Tumor blood volume increased by ≈35% from day 14 to day 28, whereas microvascular blood velocity decreased, especially at the central portions of the tumors. On confocal microscopy, &agr;v&bgr;3‐targeted but not control microbubbles were retained preferentially within the tumor microcirculation. CEU signal from &agr;v&bgr;3‐targeted microbubbles in tumors increased significantly from 14 to 28 days (1.7±0.4 versus 3.3±1.0 relative units, P<0.05). CEU signal from &agr;v&bgr;3‐targeted microbubbles was greatest at the periphery of tumors, where &agr;v‐integrin expression was most prominent, and correlated well with tumor microvascular blood volume (r=0.86). Conclusions CEU with microbubbles targeted to &agr;v&bgr;3 can noninvasively detect early tumor angiogenesis. This technique, when coupled with changes in blood volume and velocity, may provide insights into the biology of tumor angiogenesis and be used for diagnostic applications. (Circulation. 2003;108:336‐341.)

American College of Cardiology/ European Society of Cardiology Clinical Expert Consensus Document on Hypertrophic Cardiomyopathy A Report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents and the European Society of Cardiology Committee for Practice Guidelines

This document has been developed as a Clinical Expert Consensus Document (CECD), combining the resources of the American College of Cardiology Foundation (ACCF) and the European Society of Cardiology (ESC). It is intended to provide a perspective on the current state of management of patients with hypertrophic cardiomyopathy. Clinical Expert Consensus Documents are intended to inform practitioners, payers, and other interested parties of the opinion of the ACCF and the ESC concerning evolving areas of clinical practice and/or technologies that are widely available or new to the practice community. Topics chosen for coverage by expert consensus documents are so designed because the evidence base, the experience with technology, and/or the clinical practice are not considered sufficiently well developed to be evaluated by the formal American College of Cardiology/American Heart Association (ACC/AHA) Practice Guidelines process. Often the topic is the subject of considerable ongoing investigation. Thus, the reader should view the CECD as the best attempt of the ACC and the ESC to inform and guide clinical practice in areas where rigorous evidence may not yet be available or the evidence to date is not widely accepted. When feasible, CECDs include indications or contraindications. Some topics covered by CECDs will be addressed subsequently by the ACC/AHA Practice Guidelines Committee. The Task Force on Clinical …

Noninvasive Assessment of Angiogenesis by Ultrasound and Microbubbles Targeted to αv-Integrins

Background—Noninvasive methods for characterizing neovessel formation during angiogenesis are currently lacking. We hypothesized that angiogenesis could be imaged with the use of contrast-enhanced ultrasound (CEU) with microbubbles targeted to &agr;v-integrins. Methods and Results—Microbubbles targeted to &agr;v-integrins were prepared by conjugating echistatin (MBE) or monoclonal antibody against murine &agr;v (MB&agr;) to their surface. Control microbubbles (MBc) were also prepared. The microvascular behavior of these microbubbles was assessed by intravital microscopy of the cremaster muscle in mice treated for 4 days with sustained-release FGF-2. Microvascular retention was much greater (P <0.01) for MBE (11±6 mm−3) and MB&agr; (10±7 mm−3) than that for MBc (1±1 mm−3). Retained MBE and MB&agr; attached directly to the microvascular endothelial surface. Microbubble retention in 4 control mice was minimal. Subcutaneous matrigel plugs enriched with FGF-2 were created in 12 mice and studied 10 days later. Neovessels within the matrigel stained positive for &agr;v-integrins. CEU demonstrated greater (P <0.01) acoustic intensity for MBE (16.0±5.9 U) and MB&agr; (17.0±5.5 U) compared with MBc (5.8±2.6 U). The signal from targeted microbubbles (MBE and MB&agr;) correlated well (r =0.90) with the matrigel blood volume determined by CEU perfusion imaging. Conclusions—CEU with microbubbles targeted for &agr;v-integrins may provide a noninvasive method for assessing therapeutic angiogenesis.

Molecular Imaging of Inflammation in Atherosclerosis With Targeted Ultrasound Detection of Vascular Cell Adhesion Molecule-1

Background— The ability to image vascular inflammatory responses may allow early diagnosis and treatment of atherosclerosis. We hypothesized that molecular imaging of vascular cell adhesion molecule-1 (VCAM-1) expression with contrast-enhanced ultrasound (CEU) could be used for this purpose. Methods and Results— Attachment of VCAM-1–targeted and control microbubbles to cultured endothelial cells was assessed in a flow chamber at variable shear stress (0.5 to 12.0 dynes/cm2). Microbubble attachment to aortic plaque was determined by en face microscopy of the thoracic aorta 10 minutes after intravenous injection in wild-type or apolipoprotein E–deficient mice on either chow or hypercholesterolemic diet. CEU molecular imaging of the thoracic aorta 10 minutes after intravenous microbubble injection was performed for the same animal groups. VCAM-1–targeted but not control microbubbles attached to cultured endothelial cells, although firm attachment at the highest shear rates (8 to 12 dynes/cm2) occurred only in pulsatile flow conditions. Aortic attachment of microbubbles and targeted CEU signal was very low in control wild-type mice on chow diet. Aortic attachment of microbubbles and CEU signal for VCAM-1–targeted microbubbles differed between treatment groups according to extent of VCAM-1–positive plaque formation (median CEU videointensity, 1.8 [95% CI, 1.2 to 1.7], 3.7 [95% CI, 2.9 to 7.3], 6.8 [95% CI, 3.9 to 7.6], and 11.2 [95% CI, 8.5 to 16.0] for wild-type mice on chow and hypercholesterolemic diet and for apolipoprotein E–deficient mice on chow and hypercholesterolemic diet, respectively; P<0.001). Conclusions— CEU molecular imaging of VCAM-1 is capable of rapidly quantifying vascular inflammatory changes that occur in different stages of atherosclerosis. This method may be potentially useful for early risk stratification according to inflammatory phenotype.

Delayed Onset of Inflammation in Protease-Activated Receptor-2-Deficient Mice

Endothelial surface expression of P-selectin and subsequent leukocyte rolling in venules can be induced by mast cell-derived histamine and binding of thrombin to protease-activated receptor-1 (PAR1). We hypothesized that activation of endothelial PAR2 by mast cell tryptase or other proteases also contributes to inflammatory responses. Leukocyte rolling flux and rolling velocity were assessed by intravital microscopy of the cremaster muscles of wild-type mice following perivenular micropipette injections of a control (LSIGRL) or PAR2-activating (SLIGRL) oligopeptide. Injection of SLIGRL increased mean rolling leukocyte flux fraction from 34 ± 11 to 71 ± 24% (p < 0.05) and decreased mean rolling velocity from 63 ± 29 to 32 ± 2 μm/s (p < 0.05). No significant changes occurred with control peptide injection. To further evaluate the role of PAR2 in inflammatory responses, PAR2-deficient mice were generated by gene targeting and homologous recombination. Perivenular injections of SLIGRL resulted in only a small increase in rolling leukocyte flux fraction (from 21 ± 8 to 30 ± 2%) and no change in rolling velocity. Leukocyte rolling after surgical trauma was assessed in 9 PAR2-deficient and 12 wild-type mice. Early (0–15 min) after surgical trauma, the mean leukocyte rolling flux fraction was lower (10 ± 3 vs 30 ± 6%, p < 0.05) and mean rolling velocity was higher (67 ± 46 vs 52 ± 36 μm/s, p < 0.01) in PAR2-deficient compared with control mice. The defect in leukocyte rolling in PAR2-deficient mice did not persist past 30 min following surgical trauma. These results indicate that activation of PAR2 produces microvascular inflammation by rapid induction of P-selectin-mediated leukocyte rolling. In the absence of PAR2, the onset of inflammation is delayed.

Interactions between microbubbles and ultrasound: In vitro and in vivo observations

OBJECTIVES We attempted to examine the interactions between ultrasound and microbubbles. BACKGROUND The interactions between microbubbles and ultrasound are poorly understood. We hypothesized that 1) ultrasound destroys microbubbles, and 2) this destruction can be minimized by limiting the exposure of microbubbles to ultrasound. METHODS We performed in vitro and in vivo experiments in which microbubbles were insonated at different frequencies, transmission powers and pulsing intervals. Video intensity decay was measured in vitro and confirmed by measurements of microbubble size and concentrations. Peak video intensity and mean microbubble myocardial transit rates were measured in vivo. RESULTS Imaging at lower frequencies and higher transmission powers resulted in more rapid video intensity decay (p = 0.01), and decreasing exposure of microbubbles to ultrasound minimized their destruction in vitro. Although these effects were also noted in vivo with venous injections of microbubbles, they were not seen with aortic root or direct coronary artery injections. CONCLUSIONS Ultrasound results in microbubble destruction that is more evident at lower frequencies and higher acoustic powers. Reducing the exposure of microbubbles to ultrasound minimizes their destruction. This effect is most marked in vivo with venous rather than aortic or direct coronary injections of microbubbles. These findings could lead to effective strategies for myocardial perfusion imaging with venous injections of microbubbles.

Noninvasive Ultrasound Imaging of Inflammation Using Microbubbles Targeted to Activated Leukocytes

BackgroundLipid microbubbles used for perfusion imaging with ultrasound are retained within inflamed tissue because of complement-mediated attachment to leukocytes within venules. We hypothesized that incorporation of phosphatidylserine (PS) into the microbubble shell may enhance these interactions by amplifying complement activation and thereby allow ultrasound imaging of inflammation. Methods and ResultsIn 6 mice, intravital microscopy of tissue necrosis factor-&agr;–treated cremaster muscle was performed to assess the microvascular behavior of fluorescein-labeled lipid microbubbles with and without PS in the shell. Ten minutes after intravenous injection, microbubble attachment to leukocytes within inflamed venules was greater for PS-containing than for standard lipid microbubbles (20±4 versus 10±3 per 20 optical fields, P <0.05). The ultrasound signal from retained microbubbles was assessed in the kidneys of 6 mice undergoing renal ischemia-reperfusion injury and in 6 control kidneys. The signal from retained microbubbles in control kidneys was low (<2.5 video intensity units) for both agents. After ischemia-reperfusion, the signal from retained microbubbles was 2-fold higher for PS-containing than for standard lipid microbubbles (18±6 versus 8±2 video intensity units, P <0.05). An excellent relation was found between the ultrasound signal from retained microbubbles and the degree of renal inflammation, assessed by tissue myeloperoxidase activity. ConclusionsWe conclude that noninvasive assessment of inflammation is possible by ultrasound imaging of microbubbles targeted to activated leukocytes by the presence of PS in the lipid shell.