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Biomedical subjects

E Myhre

Publications and source records attributed to E Myhre.

At least 19 recordsLinked to original sources
PubMed1991

[Prolonged action nitrates in stable angina pectoris].

A randomized double blind comparison of transdermal nitroglycerin and isosorbide dinitrate tablets was conducted in 100 men with stable angina pectoris. Subjective and objective effects were virtually identical for both regimens (number of angina attacks/nitroglycerin consumption and exercise ECG test variables). The pattern of side effects was also similar for both drugs. A considerable dissociation was observed between subjective effects and effects measured by ergometer test in the individual patient. Lack of both subjective and objective effects--i.e. nitrate tolerance--was observed in approximately one fourth of the patients, and was not prevented by a twelve-hour dosing interval on isosorbide dinitrate nor a six hour transdermal nitroglycerin-free interval. Our data lends credence to the notion that the effects of long-acting nitrates in daily life and the effects measured during stress testing may involve different mechanisms.

Administration, Cutaneous↗
PubMed1989

Effects of verapamil on left ventricular relaxation and filling dynamics in coronary artery disease: a study by pulsed Doppler echocardiography.

The effect of verapamil on left ventricular diastolic function in coronary artery disease was assessed by Doppler echocardiography of transmitral flow velocities in 20 patients. At baseline, isovolumic relaxation time was prolonged compared with that in 18 age-matched normal subjects (95 +/- 13 msec versus 74 +/- 12 msec, p less than 0.001), but decreased to 80 +/- 14 msec (p less than 0.001) after treatment. The ratio between early and atrial-induced transmitral velocities (E/A-ratio) at baseline was lower in patients than in normal subjects (1.1 +/- 0.2 versus 1.4 +/- 0.3, p = 0.01), as was the filling fraction of the first third of diastole (43% +/- 5% versus 50% +/- 4%, p less than 0.001). Verapamil treatment increased the E/A-ratio to 1.3 +/- 0.4 (p less than 0.001) and filling fraction to 45% +/- 4% (p = 0.055) because of increased early filling. No change in systolic performance or heart rate was observed. Thus, coronary artery disease was associated with retarded relaxation and impairment of early filling. However, verapamil treatment enhanced relaxation and induced a filling shift toward early diastole, which indicated improved diastolic performance. The changes probably reflected reduced myocardial ischemia.

Adult↗
PubMed1988

Plasma atrial natriuretic peptide in cardiac transplant recipients. A prospective study.

Cardiac transplantation in 10 patients with congestive heart failure resulted in reduction of high plasma concentrations of atrial natriuretic peptide (ANP), preoperatively five-fold above normal, to a level two-fold above normal, which was maintained throughout a 12-week follow-up period. Cardiac function was normalized in all patients. Transient increases in plasma ANP, in four cardiac recipients 3-10-fold their basal levels, could neither be related to rejection episodes nor to cardiac dysfunction, but rather to signs of fluid and sodium retention. High plasma ANP levels in cardiac transplant recipients suggest that the capacity to secrete ANP is preserved in the transplanted heart.

Adolescent↗
PubMed1987

Reproducibility of cardiac stroke volume estimated by Doppler echocardiography.

Doppler echocardiography was used to measure cardiac stroke volume in 10 patients with coronary artery disease who were treated with cardioactive drugs. Stroke volume estimates were determined at the aortic orifice by multiplying area by systolic velocity integral measured both from the suprasternal and the apical approach. Recordings were done independently by 2 experienced observers on the same day and repeated once after 1 to 21 days. Analysis of variance showed that no systematic differences were introduced by the 2 observers and Doppler approaches or by measuring on different days. The coefficient of variation between any pair of measurements in each patient was 9%. This variability is probably a result of the method or spontaneous fluctuations of the stroke volume and not of the varying recording conditions. The ultrasonic method detects day-to-day changes of cardiac stroke volume larger than 20% with a probability greater than 0.95.

Adult↗
PubMed1987

Quantification of mitral regurgitation by Doppler echocardiography.

The present study was undertaken to evaluate a new non-invasive approach to the quantification of mitral regurgitation. Doppler echocardiography and left ventriculography were performed in 20 patients without valvular heart disease (group A), and in 30 patients with pure mitral regurgitation (group B). Volumetric flows through the aortic and mitral valve orifices were determined by Doppler technique. The aortic flow (AF) was calculated as the product of the aortic orifice area by the systolic velocity integral. The mitral flow (MF) was computed as the product of the corrected mitral orifice area by the diastolic velocity integral. The mitral regurgitant fraction (RF) was calculated as: RF = 1 - AF/MF. In group A, there was a close agreement between aortic and mitral flows (r = 0.94, P less than 0.001), and there was no significant difference between the two measurements. In group B, the mitral flow was significantly higher than the aortic flow. The regurgitant fraction assessed by Doppler echocardiography correlated well with the grades of severity of regurgitation obtained at left ventriculography. We conclude that combined measurement of both aortic and mitral flows by Doppler echocardiography provides a new and promising approach to the noninvasive quantification of mitral regurgitation.

Adult↗
PubMed1986

Measurement of aortic regurgitation by Doppler echocardiography.

In an attempt to develop a new approach to the non-invasive measurement of aortic regurgitation, transmitral volumetric flow (MF) and left ventricular total stroke volume (SV) were measured by Doppler and cross sectional echocardiography in 23 patients without aortic valve disease (group A) and in 26 patients with aortic regurgitation (group B). The transmitral volumetric flow was obtained by multiplying the corrected mitral orifice area by the diastolic velocity integral, and the left ventricular total stroke volume was derived by subtracting the left ventricular end systolic volume from the end diastolic volume. The aortic regurgitant fraction (RF) was calculated as: RF = 1 - MF/SV. In group A there was a close agreement between the transmitral volumetric flow and the left ventricular total stroke volume, and the difference between the two measurements did not differ significantly from zero. In group B the left ventricular total stroke volume was significantly larger than the transmitral volumetric flow, and there was good agreement between the regurgitant fractions determined by Doppler echocardiography and radionuclide ventriculography. Discrepancies between the two techniques were found in patients with combined aortic and mitral regurgitation or a low angiographic left ventricular ejection fraction (less than 35%). The effective cardiac output measured by Doppler echocardiography accorded well with that measured by the Fick method. Doppler echocardiography provides a new and promising approach to the non-invasive measurement of aortic regurgitation.

Adolescent↗
PubMed1986

Analysis of methodology for quantifying mitral regurgitation by Doppler echocardiography.

It is generally agreed that Doppler echocardiography is highly sensitive and specific for the detection of mitral regurgitation. There is more confusion about its ability to quantitate the degree of mitral regurgitation. Studies of the intensity of the Doppler signals, as well as cross sectional Doppler studies apparently can provide a straightforward, but rough estimate of the degree of regurgitation in term of atrial extent of the disturbed flow. The methods are also sensitive to methodological errors as beam direction, movement of the heart, signal/noise relationship and the size of the left atrium. Another approach to the non-invasive measurement of mitral regurgitation includes the use of Doppler echocardiography for the determination of both aortic and mitral volumetric flow. In a study of patients with mitral regurgitation, we found a close correlation between the regurgitant fraction determined by Doppler echocardiography, and the regurgitant severity determined by left ventriculography. This technique can only be used in pure mitral regurgitation, while associated atrial fibrillation, mitral stenosis, and combined aortic and mitral regurgitation make correct measurements difficult.

Cardiac Output↗
PubMed1985

Hypertrophic cardiomyopathy characterised by beta-adrenoceptor density, relative amount of beta-adrenoceptor subtypes and adenylate cyclase activity.

The total quantity of beta-adrenoceptors and the relative amount of beta 1 and beta 2 receptor subtypes were determined in heart biopsies of 10 patients with various heart diseases and 5 patients suffering from hypertrophic cardiomyopathy (HOCM). In membrane particle preparations from the same patients we also examined the activity of the adenylate cyclase (AC), and its response to isoprenaline, terbutaline, histamine and sodium fluoride (NaF). The high affinity ligand [125I] (1)-cyanopindolol (CYP) was used in the binding assays, and the highly beta 2-selective antagonist ICI 118 551 for the determination of beta-adrenoceptor subtypes. No differences were found in total beta-adrenoceptor density between patients with HOCM and "controls" (27.6 +/- 14.2 vs 26.5 +/- 10.7 fmol . mg-1 protein). The relative amounts of beta 1 and beta 2 receptor subtypes were similar, patients with HOCM had 82.1 +/- 4.9% of beta 1 and 14.4 +/- 3.9% of the beta 2 receptor subtype, compared with 76.3 +/- 11.5% of beta 1 and 20.7 +/- 11.0% of the beta 2 subtype in the "control" patients. Both absolute activity of AC (pmol . mg-1 protein . min) as well as the relative responses to the various stimulators were not significantly different between the two groups. Thus, this study does not support the hypothesis that HOCM is a disorder with altered beta-adrenoceptor number or adenylate cyclase response to adrenergic agonists. Furthermore, HOCM is not associated with altered response of the AC system to histamine or NaF.

Adenylyl Cyclases↗
PubMed1985

Determination of the mean pressure gradient in mitral stenosis by Doppler echocardiography.

Measurement of the mean pressure gradient provides an important estimation of the severity of mitral stenosis. However, determination of the mean pressure gradient from Doppler recordings has been unsatisfactory using previously described methods. In this study, a new method calculating the mean pressure gradient, the integral method is described. It was developed from mathematical analysis of Doppler velocity curves. Doppler echocardiography and cardiac catheterisation were performed in 23 patients with mitral stenosis to evaluate the accuracy of three current mathematical methods of determining the mean pressure gradient. The mean pressure gradients calculated by the three methods correlated highly with that measured by catheterisation (r = 0.93). However, the mean pressure gradients calculated by the previously described mean velocity square method and the arithmetical average method underestimated significantly that measured by cardiac catheterisation. In contrast, there was no significant difference between the mean pressure gradients calculated by the integral method and measured by cardiac catheterisation. These results confirm the usefulness of Doppler echocardiography for determining the mean pressure gradient in mitral stenosis and demonstrate that among current methods, the integral method provides the most accurate calculations of the mean pressure gradient.

Adult↗
PubMed1985

Noninvasive quantification of the aortic valve area in aortic stenosis by Doppler echocardiography.

To develop a noninvasive approach to the quantification of the stenotic aortic valve area, Doppler echocardiography and cardiac catheterisation were performed in 24 patients with pure aortic stenosis. The transmitral volumetric flow was measured by Doppler echocardiography and calculated as the product of the corrected mitral orifice area (CMA) and the diastolic velocity integral (DVI). The maximal aortic jet velocities were recorded by Doppler technique and integrated to obtain the systolic velocity integral (SVI). Assuming that the aortic and mitral volumetric flows are equal, the aortic valve area (AVA) was calculated as: AVA = CMA X DVI/SVI. Mean pressure gradient and cardiac output were measured during catheterisation and the aortic valve area was calculated by the Gorlin formula. Comparison between the aortic valve area determined by Doppler technique and catheterisation yielded a close correlation (r = 0.92, P less than 0.001), and there was no significant difference between the two measurements. Good correlations of the instantaneous pressure gradient and the stroke volume were also obtained between the two techniques (r = 0.91 and r = 0.90, respectively, P less than 0.001). These results demonstrate that our Doppler echocardiographic method provides a promising approach to the noninvasive quantification of the aortic valve area in aortic stenosis.

Adult↗
PubMed1985

Doppler echocardiographic measurement of cardiac output using the mitral orifice method.

Cardiac output was determined in 20 patients with various cardiac conditions by measuring the cross sectional area of the mitral orifice by echocardiography and the transmitral flow by the Doppler technique. Cardiac output was calculated by multiplying the corrected mitral orifice area by the maximum diastolic velocity integral recorded by the pulsed mode. The results were compared with that obtained by the Fick method. The correlation for cardiac output by the two techniques was high in the whole group, particularly in patients without mitral regurgitation. There was also a good correlation for stroke volume determined by the two methods. Cardiac output was significantly overestimated by the continuous mode and in patients with mitral regurgitation. These results show that the mitral orifice method provides a new and reliable approach to the non-invasive measurement of cardiac output.

Adolescent↗
PubMed1985

Changes in left ventricular stroke volume measured by Doppler echocardiography.

Cardiac stroke volume was measured simultaneously by Doppler echocardiography and thermodilution in 20 patients with coronary artery disease. Stroke volume as determined by ultrasound was calculated from the area of the aortic orifice and the flow velocity just distal to the aortic cusps. The recordings were made twice at rest. Ten patients were given dobutamine (2.5 and 5.0 micrograms/kg/min) by infusion to induce rapid changes in stroke volume from the resting state. The individual Doppler data before, during, and after dobutamine infusion correlated closely with the thermodilution data (r = 0.92). These results suggest that Doppler echocardiography reliably detects changes in stroke volume.

Adult↗
PubMed1985

Measurement of mitral regurgitation by Doppler echocardiography.

In an attempt to develop a new approach to the non-invasive measurement of mitral regurgitation, Doppler echocardiography and left ventriculography were performed in 20 patients without valvar heart disease (group A) and in 30 patients with pure mitral regurgitation (group B). Volumetric flows through the aortic and the mitral orifices were determined by Doppler echocardiography. Aortic flow (AF) was calculated as the product of the aortic orifice area and the systolic velocity integral. The mitral flow (MF) was calculated as the product of the corrected mitral orifice area and the diastolic velocity integral. The mitral regurgitant fraction (RF) was calculated as RF = 1 - AF/MF. In group A aortic and mitral flow were very similar and the difference between the two did not differ significantly from zero. In group B the mitral flow was significantly larger than the aortic flow. There was a good correlation (r = 0.82) between the regurgitant fraction determined by Doppler echocardiography and the regurgitant grades determined by left ventriculography. The regurgitant fraction increased significantly with each grade of severity. These results show that Doppler echocardiography can be used to give a reliable measure of both aortic and mitral flow. This technique is a new and promising approach to the non-invasive measurement of mitral regurgitation.

Adult↗
PubMed1979

Interactions between human serum proteins and oral streptococci reveal occurrence of receptors for aggregated beta 2-microglobulin.

A total of 31 strains of oral streptococci representing Streptococcus mutans, Streptococcus sanguis, Streptococcus mitior, Streptococcus salivarius, and Streptococcus milleri were tested for possible binding of human immunoglobulins G, G1, G2, G3, G4, A1, A2, M1, and M2 and haptoglobin, hemoglobin, fibrinogen, and aggregated beta 2-microglobulin. Radiolabeled beta 2-microglobulin in aggregated form showed affinity for 20 of the 31 strains tested. Binding activity for the protein was found in strains belonging to all five species. The bacterial receptor was resistant to trypsin. Monomeric, unlabeled beta 2-microglobulin did not interfere with the binding of the aggregated form. Of the other proteins tested, only the immunoglobulin A1 protein showed positive binding, and that was only with a single strain of S. milleri. beta 2-Microglobulin is present on all nucleated cell membranes in vivo. The reaction between aggregated beta 2-microglobulin and oral streptococci is a new type of human-bacterium interaction which should be considered in studies of bacterial adherence.

Beta-Globulins↗