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Biomedical subjects

J Holen

Publications and source records attributed to J Holen.

At least 19 recordsLinked to original sources
PubMed1996

Measurement of carotid bifurcation pressure gradients using the Bernoulli principle.

Current randomized prospective studies suggest that the degree of carotid stenosis is a critical element in deciding whether surgical or medical treatment is appropriate. Of potential interest is the actual pressure drop caused by the blockage, but no direct non-invasive means of quantifying the hemodynamic consequences of carotid artery stenoses currently exists. The present prospective study examined whether preoperative pulsed-Doppler duplex ultrasonographic velocity (v) measurements could be used to predict pressure gradients (delta P) caused by carotid artery stenoses, and whether such measurements could be used to predict angiographic percent diameter reduction. Preoperative Doppler velocity and intraoperative direct pressure measurements were obtained, and per cent diameter angiographic stenosis measured in 76 consecutive patients who underwent 77 elective carotid endarterectomies. Using the Bernoulli principle (delta P = 4v(2), pressure gradients across the stenoses were calculated. The predicted delta P, as well as absolute velocities and internal carotid artery/common carotid velocity ratios were compared with the actual delta P measured intraoperatively and with preoperative angiography and oculopneumoplethysmography (OPG) results. An end-diastolic velocity of > or = 1 m/s and an end-diastolic internal carotid artery/common carotid artery velocity ratio of > or = 10 predicted a 50% diameter angiographic stenosis with 100% specificity. Although statistical significance was reached, preoperative pressure gradients derived from the Bernoulli equation could not predict actual individual intraoperative pressure gradients with enough accuracy to allow decision making on an individual basis. Velocity measurements were as specific and more sensitive than OPG results. Delta P as predicted by the Bernoulli equation is not sufficiently accurate at the carotid bifurcation to be useful for clinical decision making on an individual basis. However, end-diastolic velocities alone as well as internal carotid artery/ common carotid artery velocity ratios are highly specific in the prediction of clinically significant carotid stenoses. An end-diastolic velocity of > or = 1 m/s accurately identifies a 50% or greater diameter stenosis, and thus may in some cases be sufficient for operation.

Blood Flow Velocity↗
PubMed1990

Doppler color flow in echocardiography: analytical and in-vitro investigations of the quantitative relationship between orifice flow and color jet dimensions.

The goal of this investigation was to explore the relationship between orifice flow rate and the dimensions of the resulting color jet. Equations were derived which describe flow rate as a function of the color jet dimensions, instrument characteristics, and a coefficient which represents the unknown velocity profile across the jet. Experiments in which fluid was injected at a variety of flow rates via an assortment of orifice sizes into a compliant, axisymmetric chamber were performed for comparison with the analytical results. During each injection, orifice flow rate and color jet dimensions were recorded. The experimental results were closely predicted (r = 0.97) by an equation which expresses flow rate as a function of the ratio of the color jet area and color jet length, and with a coefficient which approximates that of a parabolic velocity profile.

Blood Flow Velocity↗
PubMed1989

Enzyme immunoassay system for panel testing.

An immunoassay system based on enzyme immunoassay technology has been developed for quantitative panel testing. The system includes test card disposables, reagents, and an instrument. Patients' samples are processed semiautomatically in the instrument with minimum user intervention. The test card has multiple test areas at individual locations on a membrane solid phase so that simultaneous determinations from a single specimen are possible. Each panel also includes positive and negative reagent procedural controls. Factory-determined calibration curves for each analyte are provided in barcode form with each test kit. The reagents include a specimen dilution buffer, enzyme conjugate, and precipitogenic substrate. Up to 10 test cards at a time can be processed in random-access and continuous-access modes, with automated agitation of sample and reagents over the solid phase, temperature-controlled incubation, and membrane washing and reading, data reduction, and printout of results. The optical reader measures diffuse reflectance and features source intensity and wavelength compensation.

Chemistry, Clinical↗
PubMed1987

Doppler ultrasound in aortic stenosis: in vitro studies of pressure gradient determination.

Torricelli's equation expresses a simple relationship between fluid velocity and pressure gradient in orifice flow and is currently used in conjunction with noninvasive Doppler ultrasound to determine gradients in mitral stenosis, and aortic stenosis, as well as other cardiovascular orifices. In theory, however, the Torricelli equation overestimates the gradient in aortic stenosis and the Borda equation should be more applicable. A brief tutorial derivation of the Borda and Torricelli equations is presented. The applicability of Torricelli's equation in aortic stenosis was studied experimentally with a rigid wall, pulsatile flow analogue. Doppler ultrasound and manometric data were collected simultaneously. Percent stenosis, peak flow rate and fluid viscosity were varied. The results demonstrated that the Torricelli equation consistently overestimated the pressure gradient. At 61% area stenosis, the overestimation exceeded 100%. In vivo studies are required to determine the relevance of the observations to clinical situations.

Aortic Valve Stenosis↗
PubMed1987

Carotid bifurcation disease: prediction of ulceration with B-mode US.

The presence of carotid ulceration was assessed by two readers for 55 B-mode ultrasound (US) studies. Intact surgical specimens were available for comparison. Ulceration was considered present if the following criteria were obtained: a continuous contour showing focal depression, a well-defined break in the surface 1 mm or more across, a well-defined back wall at the base of the depression, and an anechoic area within the plaque which extended to the surface and was 1 mm or more deep. Using these criteria, the two readers agreed on the diagnosis for 47 studies. When the surgical specimen was used as a reference standard, the accuracy of B-mode US was 60%, its sensitivity was 39%, and its specificity was 72%. Since the impact of scan quality was ruled out by using only scans on which the two readers agreed, the poor results must be attributed to the lack of definitive US criteria. A second review of the scans, with the readers looking only for a heterogeneous echo pattern, revealed that appearance had no higher correlation with ulceration at surgery than any of the original criteria had.

Carotid Arteries↗
PubMed1986

Left coronary arterial blood flow: noninvasive detection by Doppler US.

Continuous wave (CW) and pulsed Doppler ultrasound studies with spectral analysis were used to detect the left coronary arterial blood flow in patients who were undergoing routine echocardiography. The pulmonary artery is a stable ultrasonic landmark from which detection of the blood flow can be effected. The left coronary artery can be distinguished by its blood flow toward the cardiac apex and by specific, functional flow features. Flow patterns vary among the left main, circumflex, and anterior descending arteries; patterns also vary with respiration cycles. In the present study, coronary arterial blood flow was detected in 58 of 70 patients (83%). Findings were validated by selectively injecting an agitated saline contrast medium into the left coronary artery and, in another study, by comparing human Doppler phasic flow waveforms with electromagnetic flowmeter recordings obtained in dogs.

Animals↗
PubMed1984

Is routine angiography necessary prior to carotid endarterectomy?

The records of 111 consecutive patients undergoing evaluation for possible carotid endarterectomy at the University of Rochester were reviewed. All patients had noninvasive evaluation (oculoplethysmography-Gee and direct, continuous-wave Doppler ultrasonography) as well as selective carotid angiography. Patients were grouped by clinical presentation to ascertain the relative importance of angiography in determining the need for surgery. Arteriography added nothing to clinical and noninvasive evaluation in over two thirds of patients with hemispheric cerebral symptoms or asymptomatic carotid bruits. In contrast, we found that almost all patients with nonhemispheric symptoms required angiography for adequate evaluation prior to surgery. The implication of these findings on preoperative evaluation of patients with carotid surgery is discussed.

Angiography↗
PubMed1981

Determination of pressure gradient in the Hancock mitral valve from noninvasive ultrasound Doppler data.

The accuracy with which the pressure gradient in the Hancock mitral valve can be determined from noninvasive ultrasound Doppler data was explored in a study of eight adult patients. The mean manometric pressure gradient (delta PM) was determined by performing simultaneous left atrial and left ventricular catheterization. The mean diastolic pressure gradient was also determined from noninvasive ultrasound data (delta PU). Identical cardiac cycles were used to compare delta PM and delta PU. In the eight patients delta PM ranged from 3.0 to 9.0 mmHg and cardiac output from 3.7 to 5.5 l/min. The difference delta PM-delta PU was 0.3 +/- 0.9 mmHg (mean +/- SD). The results thus indicated that noninvasive ultrasound can determine the mean diastolic gradient in the Hancock mitral valve with an accuracy which approaches that attained with conventional manometric methods.

Blood Pressure↗
PubMed1979

Determination of pre- and postoperative flow obstruction in patients undergoing closed mitral commissurotomy from non-invasive ultrasound Doppler data and cardiac output.

A non-invasive ultrasound Doppler system and indwelling thermodilution catheter system were used to determine the pre- and postoperative mitral flow obstruction in eight adults undergoing closed mitral commissurotomy. The effective valve area (Ae) was used as a measure of the obstruction. In the eight patients Ae was 1.08 +/- 0.34(SD) cm. 2 preoperatively and increased to 1.71 +/- 0.43(SD) cm. 2 postoperatively. The technique used in the investigation appears useful for the evaluation of surgical procedures designed to reduce the mitral flow obstruction.

Adult↗
PubMed1979

Determination of pressure gradient in mitral stenosis with Doppler echocardiography.

The accuracy of a non-invasive ultrasound Doppler technique for the determination of the pressure gradient in mitral stenosis was evaluated in a study of 8 adult patients. Transseptal left atrial catheterisation and retrograde left ventricular catheterisation were performed. The same diastoles were used to compare the gradient constructed from the ultrasound data (delta PU) with that constructed from the manometric data (delta PM). In the 8 patients the difference betweent he mean diastolic values of delta PU and delta PM was - 0.54 +/- 1.0 (SD) mmHg. The corresponding figure for mid-diastole was 0.01 +/- 0.9 (SD) mmHg. The results indicate that the ultrasound technique is sufficiently accurate for diagnostic purposes.

Adult↗
PubMed1979

An ultrasound Doppler technique for the noninvasive determination of the pressure gradient in the Björk-Shiley mitral valve.

The accuracy in determining the pressure gradient in the Björk-Shiley mitral implant from noninvasive ultrasound Doppler data was explored in nine adult patients. Manometric and ultrasound data were collectd simultaneously, and identical diastolic periods were used to compare the manometric gradient (delta Pm) with the gradient obtained from ultrasound data (delta Pu). In the nine patients the mean diastolic value of delta Pm ranged from 2-12.5 mm Hg and the difference between the mean diastolic values of delta Pm and delta Pu was 0.3 +/- 1.0 mm Hg(SD). The results of the investigation indicated that the method is accurate and reliable in the nonivasive determination of the mean diastolic gradient in the Björk-Shiley mitral implant.

Blood Pressure↗
PubMed1979

Paravalvular fistula in mitral valve implant. Intimation of malfunction of implant and quantification of regurgitant flow from effective area measurements.

Non-invasive ultrasound Doppler registrations and cardiac output determinations with a thermodilution catheter were performed in the presence of and after closure of a paravalvular mitral fistula in a 52-year-old patient with a 27 mm Björk-Shiley mitral valve. The data collected allowed the calculation of the regurgitant flow through the fistula. This study suggests that the method used can be of diagnostic value when mitral valve implant malfunction is suspected.

Cardiac Output↗
PubMed1978

Obstructic characteristics of Björk-Shiley, Hancock, and Lillehei-Kaster prosthetic mitral valves in the immediate postoperative period.

The flow obstruction in mitral valve implants was studied in the immediate postoperative period in 19 patients with Björk-Shiley, Hancock, or Lillehi-Kaster prosthetic mitral valves. The effective valve area (Ae) was used as a measure of the flow obstruction. The blood velocity in the implants was estimated with a non-invasive ultrasound Doppler system. The cardiac output was determined with an indwelling thermodilution catheter. The collected data allowed the determination of Ae. Multiple determinations of Ae, at various cardiac outputs and pulse rate were generally performed in each patient during the first 2--3 postoperative days. The investigation demonstrated that the method employed was useful for the study of mitral implant performance. The obtained values of Ae demonstrated that the flow obstruction in presthetic mitral valve implants is frequently considerable.

Aged↗
PubMed1977

Determination of effective orifice area in mitral stenosis from non-invasive ultrasound Doppler data and mitral flow rate.

Ten patients with mitral stenosis, but without mitral insufficiency, have been studied during cardiac catheterization. The mitral orifice blood velocities, the mitral pressure gradient, and the mitral flow rate were determined with ultrasound, manometry, and the direct Fick method, respectively. The effective orifice area was calculated from the ultrasound data and the mitral flow rate. The geometric orifice area was calculated from the pressure gradient and the mitral flow rate, using a revised Gorlin formula. A comparison of the two methods showed a correlation coefficient of 0.975. The investigation demonstrated that the ultrasound method represents an alternative to the conventional catheterization methods used for the quantification of mitral flow obstruction.

Blood Flow Velocity↗
PubMed1977

Evaluation of obstructive characteristics of mitral disc valve implants with ultrasound doppler techniques.

Ten adult patients with mitral disc valve implants have been examined on the catheterization table. Non-invasive ultrasound Doppler data, pulmonary artery wedge pressure and left ventricular pressure were recorded simultaneously. The cardiac output was determined with the direct Fick method. The effective valve area was taken as a measure of the flow obstruction in the disc valve implants. This area was calculated from the ultrasound data and the cardiac output as well as from the manometric data and the cardiac output. The resulting two sets of areas demonstrated a linear correlation coefficient of 0.86. The effective valve areas calculated from the ultrasound data were reasonable when compared with the results of in vitro studies of disc valve performance and demonstrated good agreement with the findings of other investigators.

Adult↗
PubMed1976

Determination of pressure gradient in mitral stenosis with a non-invasive ultrasound Doppler technique.

A 2 MHz continuous waveform non-invasive ultrasound doppler system has been used in the present investigation. With the aid of the audio signals of the frequency shifts, the ultrasound probe was positioned on the external chest so that the axis of the incident ultrasonic beam coincided with the direction of the maximum velocity vectors of the mitral jet. The frequency shifts due to the mitral jet were frequency analyzed and the time course of the maximum frequency shift was determined. The time course of the maximum mitral jet velocity was then determined from the doppler equation and the time course of the mitral pressure gradient from an orifice equation. The usefulness of the technique was evaluated by studying 25 patients with mitral stenosis and 10 without heart disease. The patients with mitral stenosis were studied during cardiac catheterization and the ultrasound data, the pulmonary artery wedge pressure, and the left ventricular pressure were recorded simultaneously. A table is presented where the gradient determined with the ultrasound technique, deltaPU, is compared with the gradient determined from the pressure tracing, deltaPM. Averaged over the 25 patients studied, deltaPU was 1.7 mmHg smaller than deltaPM at 0.08 sec diastolic time and 1.8 mmHg smaller at 0.25 sec diastolic time. The findings in the patients without heart disease differed distinctly from those in the patients with mitral stenosis. The investigation demonstrated that the non-invasive ultrasound technique can be used with confidence to gain an impression of the magnitude of the mitral pressure gradient. The findings also suggest that deltaPU represents the actual pressure gradient more accurately than deltaPM. Another investigation is proposed to assess the accuracy of the technique more completely.

Adult↗