PubMed Health⌕ Search

Biomedical subjects

H Sigel

Publications and source records attributed to H Sigel.

At least 55 records · Page 3Linked to original sources
PubMed1986

[Comparison of left ventricular end-diastolic volume determined by radionuclide ventriculography, by contrast-media ventriculography and by a geometry-independent method].

Ejection fraction and end-diastolic volume (EDV) are valuable parameters of left ventricular function. They can be measured by radionuclide ventriculography. This study examines EDV in comparison to two other methods. A comparison was made between EDV derived from radionuclide ventriculography (RNV), standard contrast ventriculography and a 'hybrid' method, which calculates EDV from ejection fraction, heart rate and thermodilution cardiac output. Two groups of patients were examined: 54 patients with various cardiac diseases by contrast and radionuclide ventriculography (RNV); and 18 patients with typical angina were examined by RNV at rest and during exercise three times: Control without medication, 20 minutes after 10 mg metoprolol i.v. and again 10 minutes after the second exercise and 10 mg isosorbide dinitrate sublingually. In comparison to contrast ventriculography RNV overestimated EDV by 27%, and in comparison to the hybrid method by 11% with satisfactory linearity. The extent of error increases with decrease of ventricular volume. The assumption that the two short axes of the left ventricle are equally long causes one quarter of total error. Errors caused by the algorithm delineating the borders of the left ventricle cannot be measured. For clinical purposes radionuclide ventricular EDV seems to yield satisfactory results.

Cineangiography↗
PubMed1986

[Use of quantitative methods in cineangiocardiography: a comparison of 9 methods of motion analysis for the detection of regional function in patients with coronary heart disease].

In order to evaluate the usefulness of various quantitative methods for the assessment of regional left ventricular function, a total of 9 methods (3 hemiaxial models, 1 area model and 5 radial-axes models) were applied to the radiopaque ventriculograms of 16 patients with anterior wall infarction and 13 patients with posterior wall infarction. A series of 17 patients without clinical or angiographic evidence of heart disease were used as control group. While the hemiaxial methods were consistently found to be useful and reproducible, the area method did not provide significant additional information. The diagnostic accuracy was highest with the use of 2 radial-axes methods. The sensitivity and specificity data were 90% to 100% and 70% to 100%, respectively. The remaining 3 radial-axes methods were found to be of limited value since regional wall motion abnormalities were projected to the contralateral wall. Because of this methodological shortcoming these techniques may falsely indicate asynergy in areas with normal contraction patterns. This was reflected by high sensitivity but low specificity values. A feature of the latter 3 methods was the use of the gravity center of the end-systolic frame as the reference point. The position of this reference point is decisively influenced by the extent and localization of asynergy. These findings suggest that methods using the gravity center of the end-systolic frame should not be employed in the evaluation of regional left ventricular function. In general, some quantitative methods for assessing regional left ventricular function require a considerable expense for technical apparatus which is not always justified by the extent to which additional information is gained.

Angiocardiography↗
PubMed1985

An estimation of the equivalent solution dielectric constant in the active-site cavity of metalloenzymes. Dependence of carboxylate-metal-ion complex stabilities on the polarity of mixed aqueous/organic solvents.

The stability constants of the 1:1 complexes between Cu2+ and Zn2+ with formate, acetate and several phenylalkanecarboxylates, i.e. C6H5-(CH2)n-COO- with n = 0 to 5, are summarized for water, 50% aqueous ethanol and 50% aqueous dioxane (I = 0.1 M; 25 degrees C): Complex stability depends upon carboxylate group basicity. The influence of varying amounts of ethanol or dioxane (up to 90%) on the stability of the Cu2+ and Zn2+ (M2+) complexes with formate and acetate (CA) was measured by potentiometric pH titrations. The values for pKHH(CA) and log KMM(CA) increase, as expected, with increasing amounts of the organic solvents, i.e. with decreasing solvent polarity. The changes in the equilibrium constants are also evaluated with regard to the mole fractions of the organic solvents and the corresponding dielectric constants. These results may be used to estimate for low dielectric cavities in proteins the equivalent solution dielectric constant on the basis of enhanced carboxylate basicity or metal ion binding capability (method 1). Furthermore, the measured stability constants are used for comparisons of the coordination tendency of carboxylate ligands towards zinc(II)-metalloenzymes (method 2); in this way the equivalent solution dielectric constants in the active-site cavities of bovine carbonic anhydrase and carboxypeptidase A are estimated: the values are of the order of 35 and 70, respectively. This method seems to be generally applicable to metalloproteins.

Binding Sites↗
PubMed1985

[Fatal poisoning by the retard form of verapamil. Therapeutic considerations].

A 60-year-old woman swallowed 2.4 g verapamil in a retard form (Isoptin retard). Depsite intensive efforts she died 44 hours later in a coma due to circulatory collapse. In contrast to other reported cases of poisoning, the verapamil concentration in plasma continued to rise. This atypical course with continuing absorption of verapamil was due to small-intestinal deposits of the drug, found at autopsy.

Coma↗
PubMed1985

Effects of molsidomine on regional contraction and global function of the left ventricle.

Fifteen consecutive patients (mean age 54 years) with proven coronary heart disease were studied with radionuclide ventriculography. After resting and exercise control studies, repeat studies were performed after administration of 4 mg of molsidomine sublingually and again after administration of 10 mg of metoprolol intravenously. Rest to exercise ejection fraction (EF) decreased significantly. This was significantly attenuated by molsidomine and by metoprolol. In a subset of nine patients with exercise ischemia, EF showed significant (p less than 0.05) improvement after molsidomine administration (46.7 +/- 13.7% to 57.1 +/- 16.7%), which was diminished to 54.4 +/- 10.5% after metoprolol administration. In the subgroup without exercise ischemia, molsidomine increased the EF to a lesser extent (47.3 +/- 12.7% to 52.6 +/- 13.4%, p less than 0.05). After administration of metoprolol the EF decreased below the control level (44.4 +/- 10.6%). Regional Fourier amplitudes accentuated the differences between the two groups. We conclude that molsidomine and metoprolol improve left ventricular function in patients with coronary heart disease and ischemia during exercise. In patients with reduced left ventricular function without signs of ischemia, molsidomine improves function as well and should be used additionally, if beta blockers are indicated for other reasons.

Adult↗
PubMed1984

On the metal-ion coordinating properties of the 5'-monophosphates of 1, N6-ethenoadenosine (epsilon-AMP), adenosine and uridine. Comparison of the macrochelate formation in the complexes of epsilon-AMP, AMP, ADP and ATP.

The concentration dependence of the chemical shifts of the protons H-2, H-8, H-10, H-11, and H-1' of 1,N6-ethenoadenosine 5'-monophosphate (epsilon-AMP2-) has been measured. The results are consistent with the isodesmic model of indefinite noncooperative stacking; the association constant, K = 2.5 +/- 0.3 M-1, is within experimental error identical to the value determined earlier for AMP2-,K = 2.1 +/- 0.4 M-1. The conditions for the potentiometric pH titrations, used to determine the acidity constants of H2(epsilon-AMP), H2(AMP), and H(UMP)- and the stability constants of the metal ion (M2+) complexes of the corresponding nucleoside 5'-monophosphates (NMP), were chosen so that the ligands were present in the monomeric form. The stabilities of Mg(epsilon-AMP) and Mg(AMP) are similar; however, the stabilities of the Mn2+, Cu2+ and Zn2+ complexes of epsilon-AMP2- are much larger (in the case of Cu2+ by a factor of 700) than those of AMP2-. This is due to the much larger metal ion affinity of the epsilon-adenosine moiety compared to that of the parent adenosine residue. As the uridine moiety does not participate in complex formation, the stability constants of M(UMP) have been used to evaluate the extent of macrochelation (i.e. the simultaneous coordination of M2+ to the base moiety and the phosphate group) in the epsilon-AMP and AMP complexes: the concentration of the macrochelated isomer is considerably larger for M(epsilon-AMP) than for M(AMP). A comparison with previous results for the complexes with ADP3- and ATP4- indicates the order, M(AMP)cl less than M(ADP)-cl greater than M(ATP)2-cl for the tendency to form macrochelates (cl). Due to the relatively high affinity of the epsilon-adenosine moiety towards Mn2+, Cu2+ and Zn2+, the phosphate-monoprotonated complexes M(H . epsilon-AMP)+ also become important; the corresponding complexes play only a minor role in the M2+/AMP systems. Intramolecular aromatic-ring stacking occurs in the ternary Cu(2,2'-bipyridyl)(NMP) complexes: about 80% of Cu(Bpy)(AMP) and Cu(Bpy)(epsilon-AMP) exist as the stacked isomer in aqueous solution; for the former system it has been shown in a previous X-ray study that the intramolecular ligand-ligand interaction occurs also in the solid state [Aoki, K. (1978) J. Am. Chem. Soc. 100, 7106]. Overall, the results emphasize that great care should be exercised in drawing conclusions based on studies of metal-ion-containing enzymic systems in which the natural adenine nucleotide cofactors have been replaced by the corresponding 1,N6-etheno derivatives.

Adenosine Diphosphate↗
PubMed1984

[Radionuclide ventriculography in aortic and mitral valve insufficiency. Pre- and post-operative studies of valve replacement surgery].

Radionuclide ventriculography (RNV) is now a well-established procedure for the noninvasive evaluation of cardiac hemodynamics, including the detection and quantification of valvular regurgitation. 46 patients undergoing aortic or mitral valve replacement were examined by RNV pre- and postoperatively. The specificity of RNV in the diagnosis of aortic or mitral incompetence was high. All cases of moderate to severe aortic regurgitation were identified. This, however, was not true for mitral incompetence. A significant overlap between the left atrium and the left ventricle in the LAO view is held responsible for this decrease in sensitivity. The quantification of aortic regurgitation and the assessment of left ventricular function by RNV appears to hold promise in the preoperative workup. This diagnostic approach yields important additional information, which may be essential in the appropriate timing of surgical intervention. Aortic valve replacement for incompetence as well as for stenosis was accompanied by a significant improvement in global left ventricular ejection fraction. No postoperative change in ejection fraction was found in cases of mitral incompetence, while a slight increase was observed following operative therapy for mitral stenosis. The radioisotope findings were correlated to the results obtained by cardiac catheterization and noninvasive techniques such as echocardiography. The place of RNV in the pre- and postoperative management of valvular heart disease is delineated in this paper. It is of special value in the evaluation of aortic incompetence and may be an important diagnostic adjunct in the approach to the patient with mitral valve disease or aortic stenosis.

Adult↗
PubMed1983

Metal-ion-promoted dephosphorylation of the 5'-triphosphates of uridine and thymidine, and a comparison with the reactivity in the corresponding cytidine and adenosine nucleotide systems.

First-order rate constants (50 degrees C; I = 0.1 M, NaClO4) for the dephosphorylation of UTP and TTP (1 mM) in the pH range 2-10 are compared with those of ATP and CTP; they all show the same properties indicating that the nucleic base has no influence on the rate. In the presence of Cu2+ or Zn2+ (NTP:M2+ = 1:1) this changes drastically: ATP-M2+ much greater than UTP-M2+ approximately equal to TTP-M2+ approximately equal to CTP-M2+ greater than NTP, the Cu2+ systems being always more reactive than the Zn2+ systems, and these more than the Ni2+ systems. An interaction between the nucleic base and metal ion is important for the Cu2+-ATP and Zn2+-ATP systems, but not for the pyrimidine-nucleotide systems (these behave like methyltriphosphate). Accordingly, prevention of the Cu2+-purine interaction by the addition of one equivalent of 2,2'-bipyridyl, leading to Cu(Bpy) (NTP)2-, strongly reduces the activity and all four ternary Cu2+ systems now show the same dephosphorylation rate. Addition of a second equivalent of Cu2+ to the Cu2+-UTP 1:1 system enhances the dephosphorylation rate significantly and Job's method provides evidence that a 2:1 complex is the most reactive intermediate. The relation between the initial rate, vo = d[PO3-4]/dt, and the concentration of Cu2+-UTP in 1:1 and 2:1 systems was determined. The results suggest that the reactive complex with pyrimidine nucleotides is a monomeric, dinuclear species of the type M2(NTP) (OH)- (its formation is inhibited by ligands like tryptophanate), while with M2+-ATP the reactive complex is a dimer. The connection between the indicated dephosphorylations in vitro, i.e. trans-phosphorylations to H2O, and related reactions in vivo are discussed.

Adenosine Triphosphate↗
PubMed1983

Interobserver and intermethod variation in evaluation of regional wall motion of the left ventricle.

To determine the variation in the repeated evaluation of quantitative regional wall motion of the left ventricle (LV) from right anterior oblique (RAO) silhouettes, an intra- and inter-observer test was performed in 17 patients without wall motion abnormalities, using nine different methods of regional wall motion (RWM) analysis. The results were: 1. Around the cardiac apex and near the valve plane there are regions where the subjective contour delineation yields regional mean discrepancies up to 4-5 mm (2-3 mm, respectively, near the valves); while in the other regions the mean discrepancies are usually smaller than 1 mm. 2. Absolute regional contour discrepancies, calculated in mm, show only small differences in the various methods, applied for RWM analysis. 3. If these discrepancies instead are calculated as relative changes (in relative percent) of hemiaxial or segmental shortening or area diminution, the method applied is of great significance, since the length of the axes can vary considerably from method to method. 4. From all methods applied for RWM analysis, that of Mathes [10] (radial method) had the smallest average discrepancy. These results suggest, that the LV silhouette may be best defined in the anterior and inferior wall area, while in other regions subjective impressions of contour tracing may produce a considerable variation, which can be further enhanced by the method applied for RWM analysis. Methods that employ relatively large axes of as similar as possible length are therefore preferred.

Adult↗
PubMed1983

Assessment of left ventricular function from the mitral valve echocardiogram following positive and negative inotropic interventions.

The echocardiographically visualized mitral valve motion pattern has been shown to be related to left ventricular diastolic parameters and systolic performance. In order to analyze the influence of a negative inotropic agent (penbutolol, Betapressin) and a positive inotropic drug (AR-L 115 BS, Vardax) on the movement of the anterior mitral valve leaflet (aMV), the following motion phases of the aMV were determined in 23 patients following completion of diagnostic cardiac catheterization: DE slope, EF slope, the final closing velocity of the aMV (AC/BC slope), CE amplitude, AC interval, and PQ-AC interval. These values were compared to several hemodynamic parameters. In 13 patients (group I) control values were obtained under physiological conditions as well as during right atrial pacing at constant pacing rate in order to exclude changes in heart rate. Measurements were repeated under spontaneous heart rate and during atrial pacing following the application of penbutolol. In the other 10 patients (group II) the echocardiographic and hemodynamic data were obtained before and after the intravenous application of AR-L 115 BS. In addition, left ventriculography was repeated in 8 patients after the pharmacologic intervention. The investigations revealed changes in the mitral valve motion pattern following negative and positive inotropic interventions. The most marked changes occurred in the AC/BC slope, which declined significantly after beta blockade with penbutolol (means 300.1 mm/s vs. means 208.4 mm/s; p less than 0.01). This effect proved to be unaffected by heart rate: there was also a reduction of the closure slope after application of penbutolol during atrial pacing (means 343.1 mm/s vs. means 268.6 mm/s; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1982

Radionuclide ventriculography: a noninvasive method for the detection and quantification of left-to-right shunts in atrial septal defect.

The present investigation was undertaken to assess a new scintigraphic method for the diagnosis of left-to-right shunts due to atrial septal defect based on the differing stroke volumes of left and right ventricles and to compare it with oxymetric data. Radionuclide ventriculography was carried out after injection of 20 mCi 99mtechnetium-labeled red blood cells. Time-activity curves were obtained from the left and right ventricular regions, and the ratio (A) of end-diastolic-end-systolic count rate differences for the left and right ventricles was calculated. The left-to-right shunt (in percent of the pulmonary flow rate) is then given as 100 X (1 - A/1.43; 1.43 being the previously determined mean value of A in 66 normal patients. In 16 patients with an atrial septal defect and/or partial anomalous pulmonary venous connection a correlation of r = 0.81 was found between those shunts determined by the scintigraphic method and those calculated by oxymetric data. The specificity of the method and the sensitivity in detecting left-to-right shunts exceeding 30% are high. The method is practical and already widely used for determination of ejection fraction end-diastolic volume and other factors. The combination of this technique with other methods for shunt diagnosis such as gamma-fit analysis may prove of special value.

Heart↗
PubMed1981

Evaluation of aortic and mitral valve regurgitation by radionuclide ventriculography: comparison with the method of Sandler and Dodge.

The present investigation was undertaken to introduce a quantitative scintigraphic method for evaluation of regurgitation and to compare it with the generally accepted quantitative method of Sandler and Dodge (Sandler et al., 1963). Radionuclide ventriculography was carried out after injection of 20 mCi 99mtechnetium-labeled red blood cells. Time-activity curves were obtained from the left and right ventricular regions. The ratio (A) of end-diastolic-end-systolic count-rate differences for the left and right ventricles was calculated. The ratio (A) was compared with a hemodynamic ratio (Ah) determined after the method of Sandler and Dodge (1963) with the stroke volume of the left ventricle measured angiographically, and the stroke volume of the right ventricle measured by thermodilution. In 33 patients with aortic and mitral valve regurgitation we found a correlation of r = 0.75 between (A) and Ah). Due to a broad range of normal values of (A) the sensitivity of the scintigraphic method is low. The specificity seems to be high, however, since in 64 patients with all types of heart diseases there were no false positive results. Comparing the described scintigraphic method with other modern or generally accepted methods, the principal advantages are noninvasiveness, good practicability, and the fact that important additional information about the functional state of the heart is gained. This is important in follow-up studies in patients with chronic valvular incompetence. It seems that this method will become a valuable supplement to heart catheterization in the diagnosis of valvular heart disease and may partially replace invasive methods for measuring the regurgitation fraction.

Adult↗