Established and emerging roles for ultrasound enhancing agents (contrast echocardiography)

The ability to opacify the left ventricle and delineate the endocardium after intravenous injection of microbubble ultrasound enhancing agents is of established value to quantify volumes and function in suboptimal unenhanced images, particularly in stress echocardiograms. However, applications other than quantitation of left ventricle structure and function exist for contrast enhanced left ventricular opacification. Contrast agents enable recording of Doppler velocity signals in patients with poor ultrasound transmission, providing estimates of aortic stenosis gradient and pulmonary artery pressures. Contrast echo is of value in detecting apical hypertrophic cardiomyopathy and accompanying apical aneurysms. Most importantly, ultrasound enhancing agents can identify apical and left atrial masses when they cannot be visualized in unenhanced images, and can distinguish thrombi from tumors by visualizing the vascularity inherent in tumors. Contrast agents distinguish trabecular from compacted myocardium in noncompaction syndrome, and hypertrabeculation with other abnormal conditions. A major potential application of ultrasound enhancing agents is myocardial opacification, which can assist in identifying nonviable myocardium. Also, the delayed reappearance of myocardial perfusion after microbubble destruction identifies impaired contrary flow and can diagnose coronary stenosis. Innovative applications of ultrasound contrast agents currently under investigation, include visualizing the vaso vasorum to identify plaques and assess their vulnerability, and theranostic agents to deliver drugs and biologists and to assist in sonothrombolysis. It is anticipated that the role of ultrasound contrast agents will continue to increase in the future.

Persistent Value of the Stethoscope in the Age of COVID-19

The stethoscope has long been at the center of patient care, as well as a symbol of the physician-patient relationship. While advancements in other diagnostic modalities have allowed for more efficient and accurate diagnosis, the stethoscope has evolved in parallel to address the needs of the modern era of medicine. These advancements include sound visualization, ambient noise reduction/cancellation, Bluetooth (Bluetooth SIG Inc, Kirkland, Wash) transmission, and computer algorithm diagnostic support. However, despite these advancements, the ever-changing climate of infection prevention, especially in the wake of the COVID-19 pandemic, has led many to question the stethoscope as a vector for infectious diseases. Stethoscopes have been reported to harbor bacteria with contamination levels comparable with a physician's hand. Although disinfection is recommended, stethoscope hygiene compliance remains low. In addition, disinfectants may not be completely effective in eliminating microorganisms. Despite these risks, the growing technological integration with the stethoscope continues to make it a highly valuable tool. Rather than casting our valuable tool and symbol of medicine aside, we must create and implement an effective method of stethoscope hygiene to keep patients safe.

Development of a Translatable Ultrasound Molecular Imaging Agent for Inflammation

This study details the development, characterization and non-clinical efficacy of an ultrasound molecular imaging agent intended for molecular imaging of P-selectin in humans. A targeting ligand based on a recently discovered human selectin ligand was manufactured as fusion protein, and activity for human and mouse P- and E-selectin was evaluated by functional immunoassay. The targeting ligand was covalently conjugated to a lipophilic anchor inserted into a phospholipid microbubble shell. Three lots of the targeted microbubble drug product, TS-07-009, were produced, and assays for size distribution, zeta potential and morphology were established. The suitability of TS-07-009 as a molecular imaging agent was evaluated in vitro in a flow-based adhesion assay and in vivo using a canine model of transient myocardial ischemia. Selectivity for P-selectin over E-selectin was observed in both the human and murine systems. Contrast agent adhesion increased with P-selectin concentration in a dynamic adhesion assay. Significant contrast enhancement was observed on ultrasound imaging with TS-07-009 in post-ischemic canine myocardium at 30 or 90 min of re-perfusion. Negligible enhancement was observed in resting (no prior ischemia) hearts or with a control microbubble 90 min after ischemia. The microbubble contrast agent described here exhibits physiochemical properties and in vivo behavior suitable for development as a clinical imaging agent.

Lipoprotein(a) in Patients Undergoing Transcatheter Aortic Valve Replacement

Lipoprotein(a) [Lp(a)] is a genetically determined risk factor for calcific aortic valve stenosis (CAVS) for which transcatheter aortic valve replacement (TAVR) is increasingly utilized as treatment. We evaluated the effect of a program to increase testing of and define the prevalence of elevated Lp(a) among patients undergoing TAVR. Educational efforts and incorporation of a “check-box” Lp(a) order to the preoperative TAVR order set were instituted. Retrospective chart review was performed in 229 patients requiring TAVR between May 2013 and September 2018. Of these patients, 57% had an Lp(a) level measured; testing rates increased from 0% in 2013 to 96% in 2018. Lipoprotein(a) testing occurred in 11% of patients before and in 80% of patients after the “check-box” order set ( P < .001). The prevalence of elevated Lp(a) (≥30 mg/dL) was 35%; these patients had a higher incidence of coronary artery disease requiring revascularization compared with patients with normal Lp(a) (65% vs 47%; P = .047). Patients with Lp(a) ≥30 mg/dL also had higher incidence of paravalvular leak compared with those with normal Lp(a) (13% vs 4%; P = .04). This study defines the prevalence of elevated Lp(a) in advanced stages of CAVS and provides a practice pathway to assess procedural complications and long-term outcomes of TAVR in patients with elevated Lp(a) levels.

The Prevalence of Lipoprotein(a) Measurement and Degree of Elevation Among 2710 Patients With Calcific Aortic Valve Stenosis in an Academic Echocardiography Laboratory Setting

Lipoprotein(a; Lp[a]) and its associated oxidized phospholipids are causal, genetic risk factors for calcific aortic valve stenosis (CAVS). We determined the prevalence of Lp(a) measurement among 2710 patients with CAVS and 1369 control patients (∼50% of study group) without CAVS with an echocardiogram between January 2010 and February 2016 in an academic echocardiography laboratory. Lipoprotein(a) measurements were performed at a referral laboratory using an isoform-independent assay. The prevalence of any Lp(a) measurement was 4.6% (124 of the 2710) in patients with CAVS and 3.1% (42 of the 1369) in the control group ( P = .021). In patients with CAVS, mean (standard deviation) Lp(a) levels were 38 (54) mg/dL and median (interquartile range) Lp(a) levels were 14 (6-48) mg/dL. Of the 124 patients with CAVS having Lp(a) measurements, 83 (66.9%) had Lp(a) <30 mg/dL and 41 (33.1%) had Lp(a) ≥30 mg/dL. This study reflects low physician testing of Lp(a) levels in CAVS. Given the role of Lp(a) as a causal risk factor for CAVS, and the ongoing development of therapies to normalize Lp(a) levels, our results suggest that Lp(a) measurements in CAVS should be more widely obtained in clinical practice.

Health literacy and the perception of risk in a breast cancer family history clinic

BACKGROUND

Informed consent is an essential component of medical practice, and especially so in procedural based specialties which entail varying degrees of risk. Breast cancer is one of the most common cancers in women, and as such is the focus of extensive research and significant media attention. Despite this, considerable misperception exists regarding the risk of developing breast cancer.

AIMS

This study aims to examine the accuracy of risk perception of women attending a breast cancer family history clinic, and to explore the relationship between risk perception accuracy and health literacy.

METHODS

A cross-sectional study of women attending a breast cancer family history clinic (n = 86) was carried out, consisting of a patient survey and a validated health literacy assessment. Patients' perception of personal and population breast cancer risk was compared to actual risk as calculated by a validated risk assessment tool.

RESULTS

Significant discordance between real and perceived risks was observed. The majority (83.7%) of women overestimated their personal lifetime risk of developing breast cancer, as well as that of other women of the same age (89.5%). Health literacy was considered potentially inadequate in 37.2% of patients; there was a correlation between low health literacy and increased risk perception inaccuracy across both personal ten-year (r_s = 0.224, p = 0.039) and general ten-year population estimations. (r_s = 0.267, p = 0.013).

CONCLUSION

Inaccuracy in risk perception is highly prevalent in women attending a breast cancer family history clinic. Health literacy inadequacy is significantly associated with this inaccuracy.

Abstract 235: Prevalence of Lipoprotein(a) Measurements and Extent of Lipoprotein(a) Elevations in 2,266 Patients with Aortic Stenosis: Results from an Academic Echocardiography Laboratory Practice Setting

Background: The LPA gene causes elevated lipoprotein(a) (Lp(a)) levels and causally mediates calcific aortic valve stenosis (AS). Elevated Lp(a) and its associated oxidized phospholipids (OxPL-apoB) predict the progression of pre-existing AS and need for aortic valve replacement and are targets of therapy.

Methods: We determined the prevalence and the extent of Lp(a) elevation in patients with AS diagnosed by echocardiography performed at the University of California San Diego between 2010-2015. Severity of AS was classified as critical, severe, moderate, mild, or trace. Lp(a) levels were organized as Lp(a) <30 mg/dL, 30-50 mg/dL, 50-100 mg/dL and >100 mg/dL.

Results: 2,266 patients with AS were found, with 130 critical, 333 severe, 477 moderate, 1318 mild, and 8 cases of trace AS. Mean age was 75.0 and range 18-106 years. 51% of patients were male. Prevalence of any Lp(a) measurement was 159/2,266 patients (7.02%). The number (%) of patients with an Lp(a) level was: 1) critical (n=4, 3.1%), 2) severe (n=28, 8.4%), 3) moderate (n=56, 11.7%), 4) mild (n=71, 5.4%), and 5) trace (n=0). The extent of Lp(a) elevation within each AS category is in Table 1: 55/159 (34%), 35/159 (22%) and 19/159 (12%) of patients had Lp(a) >30 mg/dL, >50 mg/dL and >100 mg/dL, respectively.

Conclusion: Lp(a) was measured in only 7.0% of patients with AS in an academic setting. Given the ongoing development of therapies to lower Lp(a) in patients with AS, educational efforts are needed to raise awareness of Lp(a) as a causal risk factor for AS.

Validation and Assessment of a Technology Familiarity Score in Patients Attending a Symptomatic Breast Clinic

INTRODUCTION

New media technologies (computers, mobile phones and the internet) have the potential to transform the healthcare information needs of patients with breast disease (Ferlay et al. in Eur J Cancer 49:1374-1403, 2013). However, patients' current level of use and their willingness to accept new media for education and communication remain unknown.

METHODS

This was a single-centre clinic-based prospective cross-sectional study. A previously developed instrument was modified, validated and tested on patients attending a symptomatic breast clinic.

RESULTS

The instrument was evaluated on 200 symptomatic breast patients. The commonest outlets for education were staff (95 %), leaflets (69 %) and websites (59 %). Websites are more likely to be consulted by younger patients (<47 years), and patients who were working, students or homemakers (p < 0.05). Patients rated usefulness of information media in this order: (1) print, (2) phone, (3) website, (4) email, (5) text and (6) apps. Patients who were new to the clinic were more likely to find text messaging and emailing useful (n < 0.05). Younger patients (<47 years) are more likely to find text messages, apps, websites and email useful (p < 0.05). Urban patients are more likely to find websites and email useful (p < 0.05). Patients with higher education were more likely to favour apps, websites and email (p < 0.05). Smartphone owners were significantly more likely to rate text messaging, apps, websites and email as useful media (p < 0.05).

CONCLUSION

This study demonstrates that new media technology use among breast patients is expanding as expected along generational trends. As such its' further integration into healthcare systems can potentially ameliorate patient education and communication.

Platelet reactivity changes significantly throughout all trimesters of pregnancy compared with the nonpregnant state: a prospective study

OBJECTIVE

Platelets play an important role in the pathophysiology of uteroplacental disease and platelet reactivity may be an important marker of uteroplacental disease activity. However, platelet reactivity has not been evaluated comprehensively in normal pregnancy. We sought to evaluate platelet reactivity using a number of agonists at defined time points in pregnancy using a novel platelet assay and compare these with a nonpregnant cohort.

DESIGN

Prospective longitudinal study.

SETTING

Outpatient department of a large tertiary referral centre.

SAMPLE

Eighty participants with 30 nonpregnant women and 50 pregnant women assessed longitudinally.

METHODS

This was a prospective cohort study performed longitudinally throughout uncomplicated singleton pregnancies with participants recruited before 15 weeks of gestation. They were controlled for a number of factors known to affect platelet reactivity. Blood samples were obtained in each trimester. Thirty nonpregnant healthy female volunteers also had a platelet assay performed. A modification of standard light transmission aggregometry was used to assess platelet function, with light absorbance measured following the addition of five different agonists at submaximal concentrations. Dose-response curves were plotted for each agonist for the nonpregnant cohort and in each trimester for the pregnant cohort.

MAIN OUTCOME MEASURES

Dose-response curves and median effective concentration.

RESULTS

When compared with the nonpregnant controls a significant reduction was demonstrated in platelet reactivity to collagen during the first trimester of pregnancy (P < 0.0001). Platelet aggregation increased significantly from the first to third trimesters in response to collagen and arachidonic acid.

CONCLUSION

Platelet reactivity varies according to pregnancy state, gestational age and agonist. The finding that platelet reactivity is reduced in the first trimester of pregnancy may be useful for the interpretation of further studies examining the role of platelet reactivity in the first trimester of pregnancies that develop uteroplacental disease.

Cross-sectional study of endothelial function in HIV-infected patients in Brazil

Antiretroviral therapy (ART) in HIV-infected patients has been associated with an increased risk of cardiovascular disease. This study evaluates vascular endothelial dysfunction of the peripheral circulation in Brazilian HIV-infected subjects on ART or naive to ART compared to a control group matched for age and body mass index (BMI). We performed a cross-sectional comparative study to measure postischemic peak flow-mediated dilation (FMD) of the brachial artery and the response to glyceryl trinitrate (GTN) in HIV-infected patients and healthy controls in Salvador, Bahia, Brazil. Endothelial vasomotor function was evaluated by assessing brachial artery FMD. Forty-four HIV-infected individuals (33 ARV treated and 11 ART naive) were compared to 25 healthy controls matched for age and BMI. FMD % was significantly lower for the ART-experienced patients compared to the ART-naive patients and was also significantly different from controls (ART experienced 8.2 +/- 6.0% vs. 19.3 +/- 4.8% vs. 23.3 +/- 6.1%), respectively (p < 0.0001). The cholesterol, triglyceride, and ALT levels were significantly higher in the ART-experienced group compared to the ART-naive and control subjects (p < 0.028); however, linear regression analysis revealed a statistically significant association of endothelial dysfunction as a dependent variable only with ARV treatment in HIV-infected subjects (p = 0.03). The association of endothelial dysfunction with ARV therapy in HIV-infected patients was independent of protease inhibitor-containing regimens or dyslipidemia. This dysfunction may contribute to the risk for HIV-associated atherosclerosis.

Comparison of dobutamine stress echocardiography with and without real-time perfusion imaging for detection of coronary artery disease

In a pilot study of 27 patients, those who presented with chest pain underwent 2 dobutamine stress echocardiographic studies, 1 with high mechanical index harmonic imaging to analyze wall motion without contrast and 1 with real-time low mechanical index perfusion imaging with intravenous Optison to assess myocardial perfusion and wall motion. All patients then underwent quantitative coronary angiography. Two independent reviewers demonstrated an improvement in sensitivity when analyzing myocardial perfusion. In the 21 patients who had significant coronary stenoses, 14 had abnormal myocardial perfusion detected at peak stress and 7 had abnormal wall motion detected by standard dobutamine stress echocardiography. There was decreased specificity with perfusion imaging by 1 reviewer. The addition of real-time perfusion imaging after intravenous contrast during dobutamine stress echocardiography has the potential to improve detection of coronary artery disease.

Visualization of risk-area myocardium as a high-intensity, hyperenhanced "hot spot" by myocardial contrast echocardiography following coronary reperfusion: quantitative analysis

OBJECTIVES

We examined whether delayed post-injection imaging of a new ultrasound contrast agent (BR-14) could produce prolonged opacification and hyperenhancement of myocardium subjected to coronary occlusion/reperfusion.

BACKGROUND

We hypothesized that ultrasound exposure destroyed BR-14 and eliminated visualization of sustained myocardial opacification from retained microbubbles.

METHODS

We studied eight open-chest dogs with 3 h of left anterior descending coronary artery (LAD) occlusion followed by 3 h of reperfusion. Myocardial contrast echocardiography (MCE) was performed before occlusion and 120 min after the onset of both occlusion and reperfusion. Ultrasound imaging was initiated 15 min after injection. Myocardial blood flow (MBF) was assessed by microspheres.

RESULTS

Pre-occlusion images revealed uniform opacification of left ventricular myocardium greater than that of the cavity, with a mean intensity of the LAD bed of 8.66 +/- 1.38 dB. During occlusion, MCE resulted in the appearance of a perfusion defect in the LAD risk area (intensity 2.08 +/- 1.10 dB). After 120 min of reperfusion, the LAD risk-area myocardium manifested dense opacification of a higher intensity ("hot spot") than baseline (13.7 vs. 8.7 dB), but with reduced MBF consistent with accumulation of a high concentration of microbubbles. Increased MCE intensity was associated with a greater myeloperoxidase score.

CONCLUSIONS

These data establish that contrast opacification by BR-14 may be selectively retained within the perfusion bed of a coronary artery subjected to occlusion/reperfusion. Such opacification exhibits defects with occlusion, manifests hyperenhanced intensity (hot spot) with reperfusion, is associated with the level of myeloperoxidase activity, and conforms to the area of myocardium subjected to altered flow.

Assessment of neonatal tetanus elimination in an African setting by lot quality assurance cluster sampling (LQA-CS)

Neonatal tetanus (NT) elimination, < 1 case per 1,000 live births (LB), was assessed at district level in Zimbabwe using a combined lot quality assurance-cluster sampling survey (LQA-CS). Three of the highest risk districts were selected. NT was considered eliminated if fewer than a specified number of NT deaths (proxy for NT cases) were found in the sample determined using operating characteristic curves and tables. TT2 + vaccine coverage was measured in mothers who gave birth 1-13 months before the survey and women aged 15-49 years. NT was considered as eliminated, TT2+ coverage was 78% (95% CI 71-82%) in women aged 15-49 and 83% (95% CI 76-89%) in mothers. The survey cost 30,000 US dollars excluding costs of consultants. NT incidence was below the elimination threshold (< 1/1,000 LB) in the surveyed districts and probably in all districts. LQA-CS is a practical, relatively cost effective field method which can be applied in an African setting to assess NT elimination status.

Effect of microbubble fragility on transit rate measurement by contrast echography

We sought to propose a simplified method to measure flow velocity based on ultrasonic microbubble destruction, and investigated the effect of microbubble shell fragility on such measurement. Acoustic density (AD) from the second harmonic short axis image of flow was obtained at variable velocities (2 to 73 mm/s) in an in vitro model during long (1000 ms) and short (33 ms) interval ultrasound (US) pulsing, allowing complete and partial microbubble replenishment between pulses, respectively. Microbubbles with shell elastic modulus of 0.4 MPa and 16 MPa were tested. By shortening pulsing interval, AD diminished gradually, rather than abruptly, to a plateau level for both microbubbles. The extent of AD decay was greater for the fragile than the strong microbubbles. A linear relationship existed between the magnitude of AD decay and flow velocity only in the higher and lower velocity range for the fragile and the strong microbubbles, respectively. Thus, difference in contrast intensities during long and short pulsing intervals, respectively, allowing complete and partial replenishment may provide for velocity measurement, in which choice of optimal microbubble fragility for the range of velocity to measure may increase the accuracy.

Epidemiology of tetanus in Italy in years 1971-2000

The incidence of reported tetanus in Italy decreased from 0.5/100,000 in the 1970s to 0.2/100,000 in the 1990 s. During this period of time, the case-fatality ratio decreased from 68% to 39%. Italy has the highest reported number of tetanus cases in European countries. Elderly women are the most affected: the proportion of women aged over 64 years among cases has increased from 60% in the 1970s to 76% in the 1990s. Vaccination campaigns need to be conducted to target this group, and the surveillance of tetanus has to be improved to identify additional groups of population at risk.

Multicenter evaluation of SonoVue for improved endocardial border delineation

OBJECTIVES

Two multicenter studies were conducted to evaluate the safety and efficacy of SonoVue as a contrast agent for enhanced left ventricular endocardial border delineation (LVEBD), and to compare the efficacy of SonoVue and Albunex in adult patients with a suboptimal, nonenhanced echocardiogram.

BACKGROUND

The use of contrast to enhance echocardiographic assessment of LVEBD is well-established. SonoVue is a new microbubble contrast agent that contains sulfur hexafluoride.

METHODS

Patients were randomized to receive four injections of SonoVue (0.5, 1, 2, and 4 ml), or two injections of Albunex and two injections of hand-agitated saline (0.08 and 0.22 ml/kg). Echocardiographic images were evaluated at the study centers and by four blinded, offsite reviewers for degree of left ventricle opacification (LVO), duration of contrast enhancement, and LVEBD.

RESULTS

LVO scores were significantly higher for all doses of SonoVue. Patients with complete LVO ranged from 34%-87% for SonoVue and from 0%-16% for Albunex. The mean duration of useful contrast effect ranged from 0.8-4.1 minutes for SonoVue and < 15 seconds for Albunex. Mean increases in LVEBD scores ranged from 3.8-18.2 for SonoVue and 0.1-4.3 for Albunex. SonoVue (cumulative 7.5 ml dose) was well-tolerated, with a safety profile similar to that observed in the control group.

CONCLUSIONS

SonoVue is superior to Albunex for improving visualization of endocardial borders in patients with suboptimal noncontrast echocardiograms. Optimal increases in LVEBD, LVO, and duration of useful contrast effect were observed at the 2.0 ml dose of SonoVue.

Reactogenicity and immunogenicity of adult versus paediatric diphtheria and tetanus booster dose at 6 years of age

We evaluated the reactogenicity and immunogenicity of a booster dose of diphtheria-tetanus vaccine administered at the age of school-entry, comparing a low-dose vaccine (dT) to the standard paediatric dose (DT). Participants were randomly assigned to receive one of the two vaccines; the study was evaluator-blinded. The frequency of side-reactions was similar when comparing the two groups, except when considering local redness and swelling, which were significantly more frequent among the DT group. The post-booster geometric mean titre of diphtheria antibodies in the DT group was twice as high as that in the dT group (14.1 IU/ml versus 7.7 IU/ml; P<0.001). The higher antibody response and the comparable reactogenicity indicate that DT should be used as booster at school-entry, particularly if additional booster doses during adolescence or adulthood are not administered.

Assessment of myocardial postreperfusion viability by intravenous myocardial contrast echocardiography: analysis of the intensity and texture of opacification

BACKGROUND

Although defects on intracoronary myocardial contrast echocardiography (MCE) indicate loss of viability after reperfusion, opacified segments may also exhibit persistent dyssynergy. Therefore, we related the intensity and texture of opacification produced by an intravenous contrast agent to histological findings to determine the characteristics of necrotic tissue by postreperfusion MCE.

METHODS AND RESULTS

MCE was performed by intravenous injection of 0.15 mL/kg QW7437 in 14 dogs who underwent 3-hour coronary occlusion followed by 3-hour reperfusion. At baseline and 3 hours after reperfusion, midventricular short-axis images were digitized and segmented. Infarction fraction (IF) for each segment was determined by triphenyltetrazolium chloride stain. Of 224 segments, 140 showed no or small infarction and served as a control group. Of 84 segments with significant infarction (IF>30%), 52 exhibited a defect on MCE, and 32 exhibited no defect. Echo texture was quantified by computing entropy based on the co-occurrence matrix analysis of gray-level pairs within each segment. Three hours after reperfusion, average and maximal entropies in the infarct segments without opacification defects were significantly higher than control levels. Histologically, the degree of intracapillary erythrocyte stasis was less in this group than in the infarcted segments with MCE defects with similar magnitude of tissue injuries.

CONCLUSIONS

Opacification defects by MCE may be present or absent in myocardium with histologically confirmed infarction. The texture of MCE from opacified but infarcted myocardium differed significantly from control segments and may assist in determination of segmental viability after reperfusion.

Characterization of contraction and perfusion in the lateral border zone between normal and ischemic myocardium following coronary occlusion by myocardial contrast echocardiography

We performed myocardial contrast echocardography with power Doppler imaging during left anterior descending occlusion in 10 dogs, and found that video intensity and dyssynergy in lateral border zones of ischemic myocardium were present, but the video intensity was significantly lower than adjacent nonischemic zones. The results of this study demonstrate that levels of perfusion and contraction, which are intermediate between normal and central ischemic zones, are observed in the border zone with coronary occlusion by myocardial contrast echocardography, and may have implications in identifying myocardium that will be spared necrosis and in measuring ultimate infarct size.

Assessment of coronary stenosis severity and transmural perfusion gradient by myocardial contrast echocardiography: comparison of gray-scale B-mode with power Doppler imaging

BACKGROUND

The present study (1) compared the ability of power Doppler imaging with that of gray-scale B-mode tissue imaging to opacify the myocardium and detect coronary stenosis by myocardial contrast echocardiography and (2) compared the response of video intensity (VI) to variable pulsing intervals for each modality.

METHODS AND RESULTS

Four grades of left anterior descending coronary artery (LAD) stenoses were created in 9 open-chest dogs. Stenoses reduced resting LAD flow by 25%, 50%, 75%, and 100% of baseline by flow probe. Myocardial contrast echocardiography was performed during varying ECG gated pulsing intervals (PIs) from 1:1 to 1:10. By gray-scale imaging, background-subtracted LAD bed VI was less than baseline VI at all PIs for the 100% reduced-flow state but not for any other flow state or interval. By power Doppler imaging, LAD bed VI was less than baseline VI at all intervals for 75% and 100% reduced-flow states but only 1:1 and 1:2 for 25% and 50% reduced-flow states, respectively. Correlation of VI and myocardial blood flow (determined by use of fluorescent microspheres) ratios from stenosed versus normal beds was stronger by power Doppler imaging. A transmural opacification gradient with stenosis was visualized and measured by power Doppler imaging, but it was insignificant by gray-scale imaging. The ratio of endocardial/epicardial flow determined by use of fluorescent microspheres was correlated with VI by power Doppler imaging at all PIs.

CONCLUSIONS

Power Doppler imaging has advantages compared with gray-scale imaging in opacifying the myocardium and in detecting coronary stenosis and altered transmural distribution of myocardial perfusion from peak VI. Because VI differences from baseline at long PI vary for mild versus severe (75% and 100%, respectively) reduced-flow states, power Doppler imaging may provide a method to quantify coronary stenoses.

Electrophysiological and antiarrhythmic effects of the atrial selective 5-HT(4) receptor antagonist RS-100302 in experimental atrial flutter and fibrillation

BACKGROUND

Stimulation of 5-HT(4) receptors increases atrial chronotropic and inotropic responses. Whether other electrophysiological effects are produced is unknown. In humans and swine, 5-HT(4) receptors are present only in atrium. Therefore, the effects of a novel 5-HT(4) receptor antagonist, RS-100302, and the partial agonist cisapride on atrial flutter and fibrillation induced in swine were studied to delineate the role of the 5-HT(4) receptor in modulating atrial electrophysiological properties and the antiarrhythmic potential of RS-100302.

METHODS AND RESULTS

In 17 anesthetized, open-chest, juvenile pigs, atrial flutter or fibrillation was induced by rapid right atrial pacing with or without a right atrial free wall crush injury, respectively. Atrial effective refractory period (ERP), conduction velocity, wavelength, and dispersion of refractoriness were determined during programmed stimulation via a 56-electrode mapping plaque sutured to the right atrial free wall. Ventricular electrophysiological parameters were also measured. All electrophysiological parameters were measured at baseline and after infusion of RS-100302 and cisapride. In the atrium, RS-100302 prolonged mean ERP (115+/-8 versus 146+/-7 ms, P<0.01) and wavelength (8.3+/-0.9 versus 9.9+/-0.8 cm, P<0.01), reduced dispersion of ERP (15+/-5 versus 8+/-1 ms, P<0.01), and minimally slowed conduction velocity (72+/-4 versus 67+/-5 cm/s, P<0.01). These effects were all partially reversed by cisapride. RS-100302 produced no ventricular electrophysiological effects. RS-100302 terminated atrial flutter in 6 of 8 animals and atrial fibrillation in 8 of 9 animals and prevented reinduction of sustained tachycardia in all animals.

CONCLUSIONS

The electrophysiological profile of RS-100302 suggests that it may have atrial antiarrhythmic potential without producing ventricular proarrhythmic effects.

Feasibility of right ventricular myocardial opacification by contrast echocardiography and comparison with left ventricular intensity

To demonstrate the feasibility and quantify the intensity of right ventricular (RV) myocardial opacification by myocardial contrast echocardiography (MCE), we analyzed MCE produced by intravenous injection of 0.15 ml/kg of QW7437 in 8 closed-chest dogs. MCE could produce visual opacification of the RV wall similar in time course to that of the left ventricular wall, and the data supported the potential role of MCE in evaluating RV hypertrophy, contraction, and perfusion abnormalities.

Flow dynamics of QW7437, a new dodecafluoropentane ultrasound contrast agent, in the microcirculation: microvascular mechanisms for persistent tissue echo enhancement

OBJECTIVES

The purpose of this study was to test the hypothesis that a subgroup of QW7437 microbubbles, dodecafluoropentane-based ultrasound contrast microspheres, resides for prolonged periods in the microvasculature.

BACKGROUND

QW7437 produces echo enhancement in myocardium which may persist relatively longer than opacification in the left ventricular cavity. The mechanism for this persistent enhancement remains unknown.

METHODS

The transit of fluorescently labeled erythrocytes was examined by fluorescence intravital microscopy in the microvessels in five rat mesenteries. Ten rats were used to observe the behavior of fluorescently labeled QW7437 microbubbles in the mesenteric microcirculation.

RESULTS

There was no significant change in erythrocyte velocity in the arterioles and venules after the administration of QW7437 microbubbles (0.05 ml/kg) preactivated by negative hydrodynamic pressure. Of 552 microbubbles observed in four arterioles and five capillaries, 549 (99.5%) passed without stoppage (> or = 0.1 s stoppage); only one stopped transiently in arteriole and two in capillaries, each for <0.5 s. Sixty-five of 478 microbubbles (13.6%) observed in six postcapillary venules 11 to 30 microm in diameter and 24 of 408 microbubbles (5.9%) in four venules 31 to 50 microm in diameter stopped transiently (0.1 to 180 s) with an attachment to venular endothelium; the remaining microbubbles passed through the venules without stoppage.

CONCLUSIONS

Prolonged survival as microbubbles in the circulation and transient stoppage of a subgroup of microbubbles in the microvasculature, particularly in venules, are potential mechanisms for the persistent tissue echo enhancement by QW7437 microbubbles during contrast echocardiography.

Persistence of Atrial Fibrillation After Its Induction-Importance of the Duration and Dispersion of Atrial Refractoriness and Electrical Remodeling

BACKGROUND: The electrophysiologic mechanisms of the persistence of atrial fibrillation (AF) after its initiation are not well understood. Therefore, the electrophysiologic characteristics of the right atrium were evaluated in an acute, pacing-induced model of AF in the pig in order to identify parameters associated with persistence of AF. METHODS AND RESULTS: AF was induced by rapid atrial pacing in 30 anesthetized, open-chest, juvenile pigs. Sustained (S) AF was defined as that lasting >10 minutes, nonsustained (NS) AF <10 minutes but >30 seconds, and no (N) AF <30 seconds. Activation mapping and programmed stimulation (S1S1 = 200 ms) was performed at 56 electrodes on the right atrial free wall, to determine ERP (mean and minimum), dispersion of refractoriness (ERPdisp, ELEdisp), conduction velocity (CV), wavelength, AF cycle length (mean of 10 beats), and AF cycle length/time (electrical remodeling). SAF was induced in 10 pigs, NSAF in 9, and NAF in 11. AF cycle length was shorter in SAF and/vs NS vs NAF (P <.001). Mean ERP (107 +/- 9 and/vs 122 +/- 5 vs 142 +/- 9, p <.001) and wavelength (7 +/- 1 and/vs 9 +/- 1 vs 11 +/- 1, P <.001) were shorter in SAF and/vs NSAF vs NAF. Minimum ERP was shorter in SAF and NSAF vs NAF (P <.001). CV at cycle lengths of 200 and 150 msec was not different between groups. Dispersion of ERP was greater in SAF and/vs NSAF vs NAF (8 +/- 1 and/vs 11 +/- 1 vs 19 +/- 4, P <.001). CONCLUSIONS: Persistence of AF correlated with shorter ERP and wavelength, and greater dispersion of ERP and electrical remodeling. There was no correlation with CV.

Real-time three-dimensional echocardiography for determining right ventricular stroke volume in an animal model of chronic right ventricular volume overload

BACKGROUND

The lack of a suitable noninvasive method for assessing right ventricular (RV) volume and function has been a major deficiency of two-dimensional (2D) echocardiography. The aim of our animal study was to test a new real-time three-dimensional (3D) echo imaging system for evaluating RV stroke volumes.

METHODS AND RESULTS

Three to 6 months before hemodynamic and 3D ultrasonic study, the pulmonary valve was excised from 6 sheep (31 to 59 kg) to induce RV volume overload. At the subsequent session, a total of 14 different steady-state hemodynamic conditions were studied. Electromagnetic (EM) flow probes were used for obtaining aortic and pulmonic flows. A unique phased-array volumetric 3D imaging system developed at the Duke University Center for Emerging Cardiovascular Technology was used for ultrasonic imaging. Real-time volumetric images of the RV were digitally stored, and RV stroke volumes were determined by use of parallel slices of the 3D RV data set and subtraction of end-systolic cavity volumes from end-diastolic cavity volumes. Multiple regression analyses showed a good correlation and agreement between the EM-obtained RV stroke volumes (range, 16 to 42 mL/beat) and those obtained by the new real-time 3D method (r=0.80; mean difference, -2.7+/-6.4 mL/beat).

CONCLUSIONS

The real-time 3D system provided good estimation of strictly quantified reference RV stroke volumes, suggesting an important application of this new 3D method.

Relation of contrast echo intensity and flow velocity to the amplification of contrast opacification produced by intermittent ultrasound transmission

Intermittent ultrasound transmission during contrast echocardiography, so-called transient response imaging (TRI), amplifies contrast intensity. This effect of TRI is attributed to decreased microbubble destruction by reduced exposure time to ultrasound energy. The present study examined the hypothesis that the signal amplification produced by TRI is related to the baseline intensity present in the image and the velocity of flow. We performed second harmonic (2.5/5.0 MHz) imaging during both continuous (frame rate 55 Hz) and electrocardiogram-triggered TRI mode. Contrast images produced by perfluorohexane microbubbles (AF0150) in a steady flow model were obtained every minute throughout the decay phase at transit velocities of 8.1, 6.2, 3.4, 1.9, and 0.7 cm/sec. The decay of videointensity over time could be fitted to a sigmoid curve for both imaging modes with r > 0.99 for individual velocities. The intensity with TRI was greater than that with continuous imaging (CI) at any time and velocity. The mean increase in intensity between modes throughout decay was 8.2 +/- 3.7, 12.8 +/- 4.2, 25.7 +/- 5.8, 49.5 +/- 8.0, and 64.0 +/- 14.4 gray levels for the respective velocity levels studied (p < 0.0001). Although varying with baseline intensity at early and late phases, the TRI amplification plateaued during middecay, and within the intensity range of 16 to 143 gray levels for CI and 67 to 186 gray levels for TRI, it showed no overlap among the different velocity levels. Thus the ability of TRI to enhance contrast opacification is much greater at low flow velocities, which has implications regarding the mechanism of TRI effect and preferential visualization of intramyocardial coronary arteries by this agent. Although this effect was influenced by the baseline intensity, it was relatively constant for each velocity level within an optimal intensity range during middecay, providing the basis for flow velocity measurement by contrast echo.

Treatment of X-linked hereditary nephritis in Samoyed dogs with angiotensin converting enzyme (ACE) inhibitor

X-linked hereditary nephritis (HN) in Samoyed dogs is a model for human HN (Alport's syndrome). Angiotensin converting enzyme (ACE) inhibitors have been shown to slow the progression of renal disease in animal models and human patients. To determine the effect of ACE inhibitor treatment on X-linked HN in Samoyed dogs, a group of affected and a group of normal males were each randomly divided into two subgroups, which were either treated with an ACE inhibitor or left untreated. ACE inhibitor treatment caused significant increases (P < 0.05) in plasma renin activity in normal and affected dogs, confirming its effectiveness, but did not lower systemic blood pressure. Three of four affected treated dogs had improved weight gains and, overall, treated dogs survived 1.36 times longer than affected untreated dogs (P < 0.05). ACE inhibitor treatment of affected dogs significantly delayed (P < 0.05) the onset of an increase in serum creatinine concentration, tended to delay the decline of glomerular filtration rate and effective renal plasma flow (ERPF), significantly improved (P < 0.05) the ERPF at 110-154 days of age, and significantly slowed (P < 0.01) the rate of increase of proteinuria. Affected treated dogs showed a significant (P < 0.05) transient reduction in glomerular basement membrane splitting. Thus, ACE inhibitor treatment of Samoyed dogs with X-linked HN produced beneficial effects with respect to renal function, renal structure, and survival.

Development and validation of a noninvasive method to determine arterial pressure and vascular compliance

The ability not only to record automated systolic and diastolic pressure, but also to derive measurements of the rate of pressure change during the cardiac cycle, would have great potential clinical value. A new method has been developed to obtain pressure measurements at 20-ms intervals by oscillometric cuff signal pattern recognition. Derivation of noninvasive pressure measurements is based on a T tube aorta and straight tube brachial artery, and assumes that the systolic phase of the suprasystolic cuff signal and the diastolic phase of the subdiastolic cuff signal most closely approximate systolic and diastolic aortic pressures, respectively. Arterial pressures obtained by this method were compared with simultaneous invasive measurements from the thoracic aorta in 36 patients. Good agreement was observed between noninvasive and invasive methods for systolic (146 +/- 4 vs 145 +/- 5 mm Hg), diastolic (80 +/- 2 vs 77 +/- 2 mm Hg), and mean (100 +/- 3 vs 100 +/- 3 mm Hg) arterial pressures, and correlation coefficients were r = 0.94, 0.91, and 0.95, respectively. To assess the validity of measurements of the rate of pressure change, oscillometric cuff signals from a subgroup of 14 patients were analyzed in detail for the peak positive pressure derivative (dP/dt(Max)), peak negative pressure derivative (dP/dt(Min)), and time interval between peak positive and peak negative pressure derivatives [t(pp)]. Results (mean +/- SEM) were: [table in text]. The incorporation of measurements of the rate of pressure change into a physical model of the brachial artery was used to derive vascular compliance. A significant correlation was observed between vascular compliance derived from the oscillometric signal and determinations by either thermodilution or Fick methods and noninvasive pressures (n = 20, r = 0.83, p <0.001). Day-to-day variability for blood pressure and vascular compliance derived by the noninvasive method did not differ by >4%, representing a reproducible measure of vascular structure and function. We conclude that the measurement of absolute pressure and rate of pressure change show good correlation with catheter data and that vascular compliance can be reliably assessed by this new method. The technology should provide a valuable noninvasive tool for the assessment of both cardiac function and vascular properties.

Cat scratch disease: evidence for a bacterial etiology. A retrospective analysis using the Warthin-Starry stain

97 cases of acute necrotizing granulomatous lymphadenitis (so called "reticulozytärabszedierende Lymphadenitis") were examined retrospectively with the Warthin-Starry stain, in order to detect bacteria in patients with cat-scratch disease (CSD). 27 patients with CSD were found and among those, bacteria were demonstrated in 4. The organisms were pleomorphic rods of about 3 micron length and occurred in clumps within foci of fresh necrosis. We found the organisms in a much lower percentage than has been described in the literature. The reasons may be that many of our patients had antimicrobial treatment prior to the biopsy and that step-sectioning of the specimen may be necessary in order to detect fresh lesions. Our findings seem to confirm the observation that CSD may have a bacterial aetiology.