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Biomedical subjects

H C Dittrich

Publications and source records attributed to H C Dittrich.

At least 19 recordsLinked to original sources
PubMed2000

Cardiac imaging using Optison.

Optison (human albumin microspheres; Mallinckrodt Inc., San Diego, CA) is an injectable suspension contrast agent indicated for use in left-ventricular chamber opacification and endocardial-border delineation. Substantial proportions of patients undergoing echocardiography have inadequate endocardial delineation and, therefore, wall motion (including stress echocardiography) without contrast. The extent of use of Optison for its current indications is likely to vary, and its use will depend upon the patient population and image quality obtained from noncontrast examinations. Early reports exist of its use in as many as 60% of patients undergoing studies in a given echocardiography laboratory. The rate of acceptance for endocardial delineation in stress echocardiography appears to be particularly high, because of the higher proportion of technically challenging studies whether with fundamental or second harmonic imaging. The ability to aid in differentiation of potential artifacts from pathology in the cavity has also been reported. Clinical studies have been conducted or are currently underway to evaluate Optison in the assessment of acute and chronic ischemic coronary artery disease. Studies in patients with unexplained acute chest pain and during exercise and pharmacologic stress have evaluated the ability of Optison to detect perfusion abnormalities as well as wall-motion abnormalities. The rapid evolution of ultrasound imaging modalities such as harmonic Doppler and broad-bond imaging will further enhance Optison's ability to characterize ischemic heart disease patients.

Albumins↗
PubMed1999

Left atrial diameter in nonvalvular atrial fibrillation: An echocardiographic study. Stroke Prevention in Atrial Fibrillation Investigators.

BACKGROUND: The left atrium (LA) is usually enlarged in patients with nonvalvular atrial fibrillation (AF), but factors associated with LA diameter are incompletely defined. METHODS AND RESULTS: This transthoracic echocardiographic cohort study includes 3465 participants with nonvalvular AF in 3 multicenter clinical trials. LA diameter determined by M-mode echocardiography was correlated with clinical and echocardiographic features by cross-sectional multivariate regression analyses. The mean LA diameter was 47 +/- 8 mm, on average 6 mm larger in those with AF at the time of echocardiography than in those with sinus rhythm (48 vs 42 mm, P <. 001). Patient age and body weight were independently predictive of LA diameter (P <.0001), but sex, body surface area, and body mass index were not. The estimated independent contribution of atrial rhythm to LA diameter was approximately 2.5 mm. Prolonged duration of AF, left ventricular dilatation and increased muscle mass, mitral regurgitation, annular calcification, and hypertension were additional independent predictors of LA diameter. CONCLUSIONS: Multiple factors appear to contribute to LA enlargement in patients with nonvalvular AF, including the presence and persistence of the dysrhythmia.

Age Factors↗
PubMed1999

In vitro, animal, and human characterization of OPTISON infusions for myocardial contrast echocardiography.

UNLABELLED: Traditionally, performing myocardial contrast echocardiography with OPTISON required maximal bolus dosing. However, sustained and consistent opacification of the myocardium would be preferable for perfusion imaging. METHODS: Images of 5 anesthetized dogs and 6 human volunteers were obtained with a second harmonic ultrasound system during bolus administration of OPTISON and 2 infusion techniques. One infusion technique used diluted OPTISON, and the other used the buoyant properties of OPTISON microspheres by placing the contrast agent between an infusion source and the intravenous site in a vertically oriented extension line (ELT). Myocardial intensities and in vitro microsphere characteristics were analyzed to assess the consistency of microsphere delivery over time. RESULTS: In addition to providing higher myocardial opacification intensity than diluted infusions, ELT infusions provided consistent microsphere concentration, phantom enhancement, and near-peak bolus-level myocardial opacification for 7 to 15 minutes. The myocardial intensity at 3 and 5 minutes in human subjects during ELT infusions (30 mL/h; 2.5 mL) was lower (220 arbitrary units [au] and 165 au, respectively) but not significantly different (P =.3 and.1, respectively) than the peak myocardial intensity (265 au) after bolus administration. CONCLUSION: This new ELT infusion method provides an acceptable alternative to bolus administration of OPTISON for prolonged myocardial opacification.

Adult↗
PubMed1999

Differing susceptibility of echocardiographic contrast agents to adverse effects of biologic factors: multicenter, videodensitometric comparison of octafluoropropane-filled microspheres with air-filled microspheres for left ventricular opacification.

BACKGROUND: Echocardiographic contrast enhancement of the left ventricle has diagnostic value in the assessment of regional and global left ventricular (LV) function. The efficacy of both octafluoropropane-filled human albumin microbubbles (OCTA) and of air-filled human albumin microbubbles (AIR) for LV endocardial delineation and qualitative LV opacification has previously been reported. However, pulmonary disease, obesity, impaired LV function, and decreased echogenicity may diminish the efficacy of contrast agents for LV opacification. The purpose of this study was to compare the susceptibility of 2 contrast agents currently approved by the Food and Drug Administration to these biologic factors. METHODS: To compare quantitative LV opacification with OCTA (0.2, 0. 5, 3.0, 5.0 mL) versus AIR (0.08 mL/kg, 0.22 mL/kg), we performed videodensitometry in 199 patients (average age 59.2 +/- 13.3 years, 79% men) studied in 2 identical, prospective, multicenter, blinded trials, of whom 74 had impaired LV function, pulmonary disease, or both, 70 were obese (body mass index >30 kg/m(2)), and 45 were nonechogenic (>/=4 of 6 endocardial segments were not seen in the apical 4-chamber view). Changes in videodensity from noncontrast to contrast agent with the same gain settings were determined at end diastole and end systole (gray scale 0 to 255 U) for 2 regions of interest: left ventricle apex-to-mid-cavity and mid-cavity-to-base. The relative influence of clinically evident pulmonary disease, impaired LV function on echocardiography, and echogenicity on LV opacification produced by both contrast agents was determined by multivariate analysis. RESULTS: Significant videodensity increases ranging from 67% to 143% were observed with both agents. At the recommended initial doses (0.5 mL for OCTA, 0.22 mL/kg for AIR), OCTA produced greater opacification than AIR in both regions of interest and at both phases of the cardiac cycle. Poor LV function was associated with decreased LV opacification for AIR but not for OCTA. Diminished echogenicity was more strongly associated with impaired opacification for AIR than for OCTA. Obesity and clinically evident pulmonary disease were associated with diminished chamber opacification with both OCTA and AIR. CONCLUSIONS: In addition to the superiority of octafluoropropane-filled microspheres to air-filled microspheres for LV opacification, the efficacy of OCTA is relatively unaffected by impaired LV function and is less susceptible to the effects of poor echogenicity than AIR.

Albumins↗
PubMed1999

Physiologically based pharmacokinetic model for fluorocarbon elimination after the administration of an octafluoropropane-albumin microsphere sonographic contrast agent.

A physiologically based pharmacokinetic model was developed to evaluate the kinetics of one of the newest sonographic contrast agents available, FS069 or Optison. This material consists of octafluoropropane gas encapsulated in proteinaceous microspheres, injected intravenously for use as a myocardial contrast agent in humans. This model has six compartments: two lung compartments (alveolar and dead volume), and compartments for the heart, slowly perfused tissue, richly perfused tissue, and gastrointestinal tract. The model was developed to determine the distribution and excretion of the octafluoropropane in the body. Despite the high affinity of octafluoropropane for tissue, the model predicted that nearly 100% of the material would be exhaled from the lungs within 6 min. The model verified the results of a phase I clinical trial with 10 healthy subjects. Ventilation rate was found to play a critical role in the complete excretion of this contrast agent. The physiologically based pharmacokinetic model was a useful tool for evaluating the safety of FS069. This model can be used a basis for developing similar models for other types of contrast agents.

Adult↗
PubMed1998

Comparison of Quality of Well-Being scale and NYHA functional status classification in patients with atrial fibrillation. New York Heart Association.

BACKGROUND: There is an increased need to provide appropriate outcomes evaluations. Although designed as a clinical assessment tool, the New York Heart Association (NYHA) classification is often used as an outcome measure. In this study the performance of the NYHA classification is compared with that of the Quality of Well-being scale (QWB), a standard outcome instrument. METHODS: Subjects from a clinical trial were administered both the NYHA classification and the QWB. Scores for patients with NYHA classification I, II, and III were compared by use of an ordinal regression model. RESULTS: There were significant differences in mean QWB score by NYHA classification (p < 0.0001). However, each NYHA classification score was associated with a wide range of QWB scores, limiting the potential usefulness of the NYHA classification as an outcome measure. CONCLUSIONS: The NYHA classification is not a sensitive measure of health-related quality of life, and its use as an outcome measure, although providing some insights, may result in misleading findings. The NYHA classification should not be used as the sole outcome measure.

Activities of Daily Living↗
PubMed1998

Lack of bioeffects of ultrasound energy after intravenous administration of FS069 (Optison) in the anesthetized rabbit.

The current study was designed to provide a sensitive in vivo model to maximize the potential bioeffects (measured by hemolysis) of B-mode ultrasound energy in combination with FS069 (Optison). B-mode ultrasound energy was delivered to anesthetized male New Zealand white rabbits with a phased array 5 MHz transducer on a Hewlett-Packard Sonos 1500 ultrasonograph, with transmit level set to maximum (40 dB, approx 135 W/cm2). FS069 (Optison), latex particles in human albumin, or human albumin alone (vehicle) was infused via an ear vein at 0.6 mL/kg. No statistically significant changes were noted in serum free hemoglobin or lactate dehydrogenase either over time or between groups.

Albumins↗
PubMed1995

Intravenous albunex during dobutamine stress echocardiography: enhanced localization of left ventricular endocardial borders.

Albunex is an intravenous contrast agent that opacifies the left ventricle (LV). This study evaluated the effect of Albunex on the enhancement of LV endocardial border localization during dobutamine stress echocardiography (DSE). Albunex was infused in 30 patients at baseline and with low- and high-dosage dobutamine. Apical two- and four-chamber views were divided into six segments each, and enhancement of LV border localization was compared with precontrast images graded as follows: 0 = none; 1 = faint; or 2 = optimal. The mean grade and percentage of segments with optimal localization of LV endocardial borders were determined. There was a significant increase in enhancement with low- and high-dosage dobutamine when compared with baseline. Of 179 segments with suboptimal enhancement at baseline, 137 (77%) became optimal during DSE with Albunex. We conclude that Albunex improves localization of LV endocardial borders and that this localization is enhanced during DSE.

Aged↗
PubMed1994

Transesophageal echocardiography of the aorta.

Transesophageal echocardiography (TEE) has become a widely used imaging technique for evaluating cardiac structure, function, and valvular anatomy. Transesophageal echocardiography has also provided a new perspective on the thoracic aorta, and there is growing evidence that the technique contributes valuable and sometimes unique information about aortic structure and pathology. Recently introduced multiplane transesophageal probes have improved visualization of the proximal and transverse aorta, but few comprehensive discussions of TEE's application in aortic disease exist. Therefore, we have reviewed the published literature and our institutional experience in transesophageal aortic ultrasonography. The available evidence strongly supports the use of TEE in aortic dissection and atherosclerosis and suggests potential utility in additional diseases of the aorta such as aneurysm, ulceration, trauma, and congenital or inherited malformation.

Aortic Dissection↗
PubMed1994

What's new in transesophageal echocardiography?

Transesophageal echocardiography continues to evolve as an important complimentary technique to transthoracic echocardiography for the diagnosis and management of various cardiovascular disorders. Improved transducer technology has expanded the indications to include assessment of ventricular function, especially in the intraoperative setting. Automatic border detection may further simplify the quantitative approach of transesophageal echocardiographic-guided assessment of ventricular function. Another area in which the technique continues to develop is valvular disease, especially for planimetry of the aortic valve area in aortic stenosis. The technique continues to be used in the evaluation of endocarditis, especially prosthetic valve involvement, and for the evaluation of the patient with a potential cardiac source of emboli. Clearly, transesophageal echocardiography plays an important role in evaluating lesions of the aorta, particularly dissection, where it may be the diagnostic test of choice. Undoubtedly, the technique will continue to evolve with changes driven by developments in technology.

Aortic Diseases↗
PubMed1994

Cardiac structure and function in chronic thromboembolic pulmonary hypertension.

The observations made on patients with chronic TE-PH conform with the work of others who have shown marked right-sided cardiac chamber enlargement and abnormal left-sided diastolic function in patients with other forms of PH and RV pressure overload. The unique results from our patient population are a consequence of the reversal of these structural and functional abnormalities early after surgical treatment of the PH. The reversal of these abnormalities, including normalization of RV function, is extremely important when considering forms of therapy such as isolated lung transplantation, where a failure of RV function to normalize would be catastrophic. Although echocardiography is currently limited by its data acquisition in two dimensions, the results concerning measurements of area and length, rather than volume, are convincing. It is anticipated that future application with techniques such as three-dimensional reconstruction of echocardiographic images will allow an even more thorough evaluation of the cardiac structural and functional changes in patients with thromboembolic pulmonary hypertension.

Chronic Disease↗
PubMed1993

Outcome after acute myocardial infarction in patients with prior coronary artery bypass surgery.

Little is known concerning the influence of remote prior coronary artery bypass grafting (CABG) on the outcome of patients with acute myocardial infarction (AMI). Therefore, this study evaluated 2,494 patients with AMI of whom 219 (8.8%) had a history of CABG a mean of 7.1 +/- 3.7 years before the index AMI. Compared with all other patients, those with a history of CABG had an increased prevalence of a history of prior AMI (153 [70%] vs 547 [24%]), congestive heart failure (48 [22%] vs 236 [10%]), and angina pectoris (165 [75%] vs 787 [35%]), all p < 0.001. There was no difference in age, but patients with prior CABG were more often men (192 [88%] vs 1,702 [75%], p < 0.001). During the hospitalization for AMI, patients with prior CABG had more recurrent ischemic pain (100 [46%] vs 732 [32%, p < 0.001]), and more frequently developed non-Q-wave AMI (72 [33%] vs 514 [23%], p < 0.01). In-hospital mortality did not differ among patients with or without prior CABG (15 [7%] vs 195 [9%]). At hospital discharge, more patients with prior CABG had complex ventricular ectopic activity on 24-hour ambulatory electrocardiographic monitoring (48 of 74 [65%] vs 327 of 797 [41%], p < 0.0001), and radionuclide ejection fraction < 0.45 (53 of 99 [54%] vs 430 of 1,024 [42%], p < 0.01). Among patients undergoing coronary angiography during the first 2 months, multivessel coronary artery disease was more prevalent among patients with prior CABG (78 of 107 [73%] vs 508 of 959 [53%], p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Radiofrequency modification of atrioventricular conduction by selective ablation of the low posterior septal right atrium in a patient with atrial fibrillation and a rapid ventricular response.

A case is presented of a 58-year-old woman with atrial fibrillation and uncontrolled ventricular responses up to 180 beats/min despite therapy with digoxin. Radiofrequency energy was applied to the low posteroseptal right atrium in an attempt to modify "slow fiber" conduction. This resulted in a decrease in ventricular rate from 125 to 50 beats/min. Follow-up Holter monitor demonstrated an average heart rate of 64 beats/min (range 43-112). On exercise tolerance test, the maximum heart rate was 126. Modification of the low posterosepta right atrium may prove to be an alternative to AV node or His bundle ablation and pacemaker implantation in patients with poorly controlled atrial fibrillation and rapid ventricular response. The mechanism by which this approach was effective may be ablation of slow conducting AV nodal fibers with a short refractory period.

Atrial Fibrillation↗
PubMed1992

Effects of sustained-release nicardipine on regression of left ventricular hypertrophy in systemic hypertension.

The effects of a sustained-release formulation of the calcium antagonist nicardipine on left ventricular (LV) mass, Doppler transmitral velocity profiles and plasma neurohumoral studies were analyzed in patients with mild to moderate systemic hypertension. A double-blind placebo control phase in 28 patients was carried out for 6 weeks with a subgroup of 13 subsequently entering an open-label long-term phase for 1 year. Nicardipine produced a significant decrease in systolic and diastolic pressure over the 6-week phase (158 +/- 15 to 142 +/- 9 mm Hg, and 100 +/- 5 to 89 +/- 9 mm Hg, respectively, both p less than 0.001). No significant differences in Doppler measures of mitral inflow or echocardiographic measures of LV function, wall thickness or mass were noted in the 6-week phase of the study. Although nicardipine increased both norepinephrine and renin values after the first dose, these levels had returned to baseline in most patients after 6 weeks. In addition, there was no evidence for stimulation of adrenomedullary activity because nicardipine had no effect on epinephrine or dopamine-B-hydroxylase levels at first dose or after 6 weeks. In the 13 patients treated for 1 year, systolic and diastolic pressure remained significantly decreased compared with pressure before therapy (135 +/- 9 vs 147 +/- 15 mm Hg, and 85 +/- 6 vs 97 +/- 9 mm Hg, both p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1992

The importance of tricuspid valve structure and function in the surgical treatment of rheumatic mitral and aortic disease.

A significant proportion of individuals with rheumatic disease have tricuspid valve involvement which may be clinically important and alter the medical or surgical approach to treatment. Therefore 50 patients with rheumatic left-sided valvular lesions who were referred for operative treatment were studied. Thirty patients had angiographically significant tricuspid regurgitation (group I) and 20 had a competent tricuspid valve (group II). Pre-operative cardiac assessment included Doppler echocardiography and contrast ventriculography. Patients with tricuspid regurgitation more commonly had mitral valve disease or combined mitral and aortic valve lesions, (P less than 0.001) and were more likely to have atrial fibrillation than those without tricuspid regurgitation (P less than 0.001). Pulmonary arterial systolic and mean right atrial pressures were higher in group I (both P less than 0.01). A close relationship was found between the angiographic and Doppler assessment of the degree of tricuspid regurgitation (P less than 0.01). Doppler-derived measurement of the right ventricular-right atrial systolic pressure difference correlated well with the systolic trans-tricuspid pressure difference measured at cardiac catheterization (y = 0.7x + 22, r = 0.67, P less than 0.001) and the pulmonary arterial systolic pressure (y = 0.8x + 27, r = 0.71, P less than 0.001). Rheumatic involvement of the tricuspid valve identified by pre-operative echocardiography was confirmed in five patients at surgery. Of the 13 patients with functional tricuspid regurgitation at operation, only two had been diagnosed as having organic disease by echocardiography. Furthermore, in all 18 cases where Doppler suggested grade 3 or 4+ tricuspid regurgitation, surgical repair or replacement of the valve was performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗