PubMed Health⌕ Search

Biomedical subjects

R L Donnerstein

Publications and source records attributed to R L Donnerstein.

At least 37 records · Page 2Linked to original sources
PubMed1991

Acoustic analysis of the closing sounds of bileaflet prosthetic valves in a sheep model.

Previous investigations of mechanical valve sounds have shown that (1) frequency spectra of sounds produced by abnormal valves differ from those of properly functioning valves and (2) leaflets of normally functioning bileaflet valves do not close synchronously. This investigation studied effects of mechanical valve size, environment, and hemodynamic state on closing sounds. A single 25 mm bileaflet mitral mechanical valve was implanted in six sheep and a single 27 mm valve in four sheep. With digital signal processing, asynchronous leaflet closure and frequency spectra were assessed after alterations in animal position, respiratory phase, heart rate, afterload, contractility, and preload. Both asynchronous leaflet closure and frequency spectra varied among animals, and, except for a decrease in asynchrony with increasing contractility, were largely independent of valve size and hemodynamics. Baseline asynchrony ranged from 0.5 to 4.2 msec. Frequency spectra were characterized by the first three resonant peaks. Lowest resonant peaks ranged from 2.5 to 3.4 kHz, middle from 4.7 to 6.8 kHz, and highest from 7.2 to 9.6 kHz. These results indicate that accurate assessment of mechanical valve function with acoustic analysis requires baseline studies in all patients by means of a system with a frequency response of more than 10 kHz.

Animals↗
PubMed1990

Alignment of P waves for signal averaging.

Signal averaged atrial activity recorded from the body surface is finding increased use in assessing atrial arrhythmias. The process of signal averaging is critically dependent upon precise alignment of the waveform of interest. The alignment accuracy of wide (0.01-300 Hz) and narrow (10-300 Hz) bandpass filtered P waves recorded from the body surface were compared to atrial electrograms recorded from temporary pacing wires. The locations of the filtered P waves relative to the atrial electrogram were calculated beat-by-beat for 100 beats in 15 patients aged 1 month to 71 years. The standard deviation of the alignment error for the wide filtered surface P wave averaged 1.7 +/- 0.8 msec and for the narrow filtered P waves was 0.8 +/- 0.4 ms. These results demonstrate that high pass filtering will improve alignment accuracy, and therefore, improve frequency resolution for the analysis of signal averaged P waves.

Arrhythmias, Cardiac↗
PubMed1989

Continuous spectral analysis of heart murmurs for evaluating stenotic cardiac lesions.

Severity of stenotic heart lesions affects timing, quality and pitch of associated heart murmurs. This quantitative study investigated the relation between instantaneous sound frequencies contained in heart murmurs and magnitudes of Doppler jet velocities measured distal to associated obstructions. Heart murmurs were recorded from 18 patients, ages 1 day to 23 years, with 21 separate murmurs resulting from abnormal valves (18 studies) or left-to-right shunts (3 studies). Recorded murmurs were digitized and divided into 12.3-ms time segments for computer frequency analysis using the maximum entropy method. Murmur spectra were plotted in gray scale against time. All murmurs contained dominant frequencies that varied with time. Dominant murmur frequencies and associated Doppler jet velocities at equivalent points in time were measured at 50-ms intervals. For 88 points analyzed, instantaneous dominant frequencies ranged from 130 to 410 Hz (mean +/- standard deviation 282 +/- 70 Hz) and instantaneous jet velocities ranged from 110 to 460 cm/s (290 +/- 80 cm/s). For the 21 murmurs studied, peak murmur frequencies ranged from 200 to 410 Hz (308 +/- 70 Hz) and peak jet velocities ranged from 165 to 460 cm/s (320 +/- 78 cm/s). Instantaneous dominant frequency correlated to instantaneous jet velocity (r = 0.85) and peak dominant frequency correlated to peak jet velocity (r = 0.89). This in vivo study demonstrates that dominant frequencies contained in heart murmurs are related to instantaneous jet velocities distal to associated obstructions.

Adult↗
PubMed1988

Fetal cardiac Doppler flow studies in prenatal diagnosis of heart disease.

The prenatal diagnosis of fetal cardiac disease has become increasingly accurate as the technology of ultrasound has improved. Although two-dimensional real-time ultrasound remains the primary method of diagnosis, Doppler blood flow velocity estimates can provide valuable pathophysiologic information to support the anatomic diagnosis. We present six cases in which Doppler studies contributed to the accuracy of the diagnosis of fetal heart disease, including tetralogy of Fallot, right and left ventricular hypoplasia, atrioventricular canal defect, double-outlet right ventricle, and pulmonic stenosis. Velocities in these cases are compared with those in normal fetuses. If Doppler flow velocities are not consistent with the observed morphologic changes, further observations are indicated. Inasmuch as most anatomical heart lesions result in altered flow patterns, Doppler investigations of intracardiac and extracardiac flow should be a routine component of the fetal echocardiogram when structural abnormalities are found.

Adolescent↗
PubMed1986

Doppler echocardiographic evaluation of left-to-right shunts in congenital heart disease.

Doppler echocardiography enables the possibility of determining pulmonary to systemic flow ratios in patients with left to right shunts. Volume flow is calculated as the product of mean velocity over time, as evaluated by pulsed Doppler, and the cross-sectional area through which the flow passes. Appropriate sites for measurement of velocity and cross-sectional area of flow are the ascending aorta, right ventricular outflow tract and pulmonary artery as well as the tricuspid and mitral valve orifices. Velocity is always recorded as parallel as possible to the direction of flow. Echocardiographic measurements of the area of flow are carried out at the level of the sample volume. In the presence of an atrial or ventricular septal defect, the flow in the ascending aorta normally serves as systemic flow; alternatively, mitral or tricuspid flow may be used to cross-check these values. The latter serves for calculation of systemic flow in patent ductus arteriosus. In atrial or ventricular septal defect, the pulmonary flow is normally derived in the region of the pulmonary artery; in patent ductus arteriosus, however, in the region of the ascending aorta. As an alternative, or for confirmative use, in atrial septal defect the tricuspid flow and in ventricular septal defect and patent ductus arteriosus the mitral flow, can be taken into consideration. Studies we performed in 31 patients with atrial septal defect showed a close correlation between Doppler echocardiographic measurements and data obtained by cardiac catheterization and radionuclide studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1985

Ultrasonic assessment of cardiac function in the intact human fetus.

Echocardiography may provide information concerning the structural development of the fetal human heart. The information available from such studies, when interpreted in light of existing knowledge of developmental cardiac physiology, may give insight concerning in utero cardiac pump function. The quantitation of cardiac structural growth in utero has been used to provide growth curves for the chambers of the fetal heart. Disparity in the ratio of right ventricular/left ventricular size (normally 1.0 to 1.2) may suggest acute ventricular failure and dilation. Electromechanical analysis using M-mode techniques may be used to analyze and monitor the treatment of fetal cardiac arrhythmias and provide systolic time interval analysis. Doppler waveform analysis provides information concerning directional flow and vascular impedance and Doppler flowmetry has promise for the measurement of fetal aortic and umbilical venous blood flows. Such studies have increased our understanding of fetal circulatory function and have practical implications for the establishment of fetal cardiac diagnosis and treatment programs.

Arrhythmias, Cardiac↗
PubMed1983

Fetal echocardiography. A tool for evaluation of in utero cardiac arrhythmias and monitoring of in utero therapy: analysis of 71 patients.

Fetal echocardiographic studies were performed in 71 patients referred for evaluation of cardiac rhythm disturbances at 24 to 40 weeks' gestation. After 2-dimensional echocardiographic study of cardiac structure was performed, M-mode echocardiograms were analyzed for measurement of cardiac rate, atrioventricular contraction sequence, atrioventricular valve motion, and duration of postectopic pauses. Arrhythmias were diagnosed in 59 patients. In 34 patients with isolated ectopic beats, the arrhythmia resolved during later pregnancy in 26 or within the first 5 days of life in 8. Six patients had mild sinus bradycardia and 8 had frequent sinus pauses; all 14 had resolution of the arrhythmia during pregnancy. Sustained arrhythmias occurred in 11 patients. Deaths occurred when there was associated fetal congestive heart failure (hydrops fetalis), structural heart disease, or both. M-mode echocardiography diagnosed supraventricular tachycardia in 3 fetuses. The echocardiogram was used thereafter for monitoring transplacental digoxin therapy.

Anti-Arrhythmia Agents↗