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Biomedical subjects

G Hellige

Publications and source records attributed to G Hellige.

At least 127 records · Page 7Linked to original sources
PubMed1980

Comparison of myocardial oxygen consumption indices in man.

Hemodynamic indices of myocardial oxygen consumption (MVO2) were examined in 13 patients with coronary heart disease. The specific aim of this study was to investigate whether clinical results agree with experimental findings in animals. During hemodynamic and respiratory steady-state conditions at rest, the MVO2 (7.6-14.2 ml/min/100 g) was measured directly by myocardial blood flow (argon method) and arterio-coronary venous oxygen content difference. MVO2 was compared with five indirect indices of MVO2. A complex additive parameter consisting of five components of MVO2 had the highest correlation with MVO2 (r = 0.97), as was also demonstrated in a recent experimental study at maximum changes in hemodynamics and MVO2. More easily measurable predictors of MVO2 such as tension-time index (r = 0.923), product of mean systolic aortic pressure and square root of heart rate (r = 0.928), pressure rate product (r = 0.915), and triple product (r = 0.941) were less closely correlated with MVO2. The lower correlations of the readily obtainable indices of MVO2 are probably related to their failure to incorporate factors such as contractility and ventricular dimensions, which are known to exert an important influence on MVO2. The excellent correlation of the hemodynamic additive parameter with MVO2 supports the theoretical concept and the implications of the experimental study. The accurate prediction of MVO2 is based on adequate measurement of MVO2 for the velocity of tension development and maintenance of tension during systolic ejection period, both of which are integrated in the additive index.

Adult↗
PubMed1980

DPTI/STTI--an index of the myocardial oxygen supply/demand ratio?

The DPTI/STTI (diastolic pressure-time index/tension-time index) ratio is applied as an indicator of myocardial ischemia particularly in cardiovascular and anesthesiologic care units. The validity of the DPTI/STTI ratio was examined in intact dogs with large variations of oxygen supply and demand. The correlation of DPTI/STTI to the directly measured oxygen supply/demand ratio was poor even under maximal coronary vasodilation. Many data points were far below the critical DPTI/STTI values (reported previously) without occurrence of myocardial ischemia, failure, or edema. Therefore caution is necessary if the DPTI/STTI ratio is to applied to humans.

Animals↗
PubMed1980

[Reduction in cardiotoxicity of ionic contrast media used in coronary angiography by added calcium--Clinical study (author's transl)].

In 16 patients with CAD, hemodynamic and electrophysiologic side effects were examined following selective coronary artery injections with Urografin 76%, a commonly used ionic contrast medium. A Millar transducer tipped catheter was placed in the left ventricle for continuous pressure recording also during injections. The unmodified contrast medium decreases peak left ventricular pressure (-22 +/- 8%) and dp/dt max (-27 +/- 13%) markedly at injection. With added calcium (22.5 mEq/l) this cardiodepressive reaction becomes diminished to -15 +/- 7% and -13 +/- 8% respectively with high significance (p < 0.001). This positive effect is even more marked using higher volumes of contrast material for injection. In contrast to animal experiments, calcium did not completely compensate the negative inotropic reaction even in higher concentration (33.75 mEq/l). The marked sinus slowing (-29 +/- 14%)--observed in patients and not influenced by the calcium addition--has an additional effect in the sense of a "negative frequency-inotropism" and is responsible for the residual cardiodepressive reaction. An influence on electrophysiologic side reactions can also be observed with added calcium but only in injections with higher volumes of contrast medium. QT-elongation, T-wave changes are reduced significantly. We did not see any unfavorable reactions caused by added calcium. The cardiodepressive side effects on the contractile force by commonly used ionic contrast media can be reduced by adding calcium in the above-mentioned concentration. This may be helpful when studying high risk patients and using high injection volumes.

Adult↗
PubMed1979

Validity of myocardial oxygen consumption parameters.

The purpose of this study was to examine any reported indices for estimating myocardial oxygen consumption (MVO2) under uniform experimental conditions at maximal variation of hemodynamics and MVO2. One hundred sixty-two steady states were analyzed in 10 closed-chest dog experiments. Myocardial blood flow was directly measured by a different pressure catheter in the coronary sinus. The indirect values of MVO2 calculated from 24 indices were compared with directly measured MVO2. Throughout a wide range of hemodynamic states, the best correlate with MVO2 was found to be the additive parameter Et (r = 0.96). Any indices that do not incorporate potentially important changes of MVO2 related to both myocardial contractility and ventricular dimensions show unsatisfactory correlations with MVO2 at extreme changes of hemodynamics. Tension-time index (TTI) correlates poorly with MVO2 (r = 0.63). This result is due to the neglect of contractility. Pressure-heart rate product (P X HR) correlates with MVO2 with r = 0.86. Better results for TTI and P X HR, as reported in previous works, are reproducible by dividing our data into two groups of different inotropic states. At normal and moderate inotropic stimulation the correlation for TTI rises to r = 0.96, and for P X HR to r = 0.91. This augmentation is to be referred to the close relationship (r = 0.92) of peak ventricular pressure to maximum rate of pressure rise in this group. The additive parameter E1 is the best, both at moderate (r = 0.97) and at maximal inotropic stimulation (r = 0.87), and is to be preferred for indirect estimation of MVO2. Results are discussed with regard to the clinical application of MVO2 indices.

Animals↗
PubMed1978

[Validity of oxygen saturation and content determinations with various modern instruments (author's transl)].

A study has been undertaken to determine the accuracy of measuring oxygen saturation and oxygen content of blood with five different, commercially available systems. The indications for using them in medicine are discussed. In animal experiments simultaneous measurements were carried out with variations of oxygen saturation from 7% to 100%, of oxygen content from 0.1 vol% to 18 vol% and hemoglobin content from 5.5 g% to 18 g%. The Lex-O2-Con, the CO-Oximeter IL 182 and the Hemoximeter OSM2 are usable over the total range of variations, but the results of the AO-Oximeter are only correct in the range above 50% oxygen saturation. The information directly displayed by the In Vivo-Hämoreflektometer IVH3 are satisfactory, but its use obviously must be reserved for special situations which warrant the use of the catheter.

Animals↗
PubMed1976

Quadrupole mass filtering for registration of blood gas partial pressures.

With a newly developed quadrupole mass spectrometer several blood gas partial pressures are recorded simultaneously and continuously. In the mass filter the separation of the ions to be detected takes place in a hyperbolic electric field with variable direct and alternating voltages with a constant frequency of 2.4 MHz. For blood gas analysis a fully relaxed experimental animal was artifically ventilated and provided with arterial and venous catheters. Each catheter consisted flexible steel tubing (external diameter 0.6 mm) slotted near the end and covered with a silicone rubber membrane. The distance from the measuring tip to the mass spectrometer was 150 cm. Experiments with blood, in vivo equilibrated with gas mixtures, showed good reproducibility; the mean error of the helium partial pressure, for example, was less than 4%. During respiration using a gas mixture with 40% argon, the time constant t63% was found to be 55 s for the whole experimental arrangement including the experimental animal.

Animals↗