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J Zipfel

Publications and source records attributed to J Zipfel.

31 records · Page 2Linked to original sources
PubMedDate not supplied

Experimental validation of methods for the measurement of coronary sinus blood flow in man.

The measurement accuracy of clinically applicable methods for blood flow measurement in coronary sinus -- continuous local thermodilution (LTD), differential pressure (DP), ultrasonic Doppler (US) and the electromagnetic flow measurement method (EMF) -- was examined in 15 anaesthetized closed chest dogs with left ventricle weights between 150 and 200 g. The LTD, DP, US and the EMF were examined in each experiment in the two following arrangements. 1. In coronary sinus -- left jugular vein by-pass: This arrangement allowed four reference methods for measurement of coronary sinus blood flow (CBF). 2. In "clinical" position, without by-pass, which allowed two reference methods for CBF measurements. The results on the measurement accuracy of the LTD, DP and US are, depending on the measurement arrangement, contradictory. In the by-pass arrangement 1 there was observed a good agreement of the LTD, DP and US CBF values with the reference values. In the "clinical" position, without by-pass 2 the measurement accuracy of LTD was not sufficient for exact measurement of CBF and derived parameters. The examined velocity tip flow probes (US, DP) gave no correlation with the reference methods. US and DP are even for semiquantitative estimation of CBF unsuitable. The EMF tip flow probe was for the CBF measurement unsuitable, because of disturbance by the electrical activity of myocardium.

Animals↗
PubMedDate not supplied

Unfavorable effects of ventricular pacing on myocardial energetics.

The effects of ventricular pacing (90-330 beats/min) and atrial pacing (120-210 beats/min) on myocardial oxygen consumption (MVO2) and its hemodynamic determinants and on myocardial pumping efficiency were studied systematically on intact dogs. In six closed-chest experiments 158 steady states were analyzed. Myocardial blood flow was measured with a differential pressure sinus catheter, oxygen consumption (5-30 ml/min . 100g) was determined simultaneously by the Fick principle and the additive hemodynamic parameter Et. Ventricular and atrial pacing were compared with both methods at identical heart rates. Additionally, the coincidence between both methods of determining MVO2 was examined at sinus rhythm with sympathetic stimulation (norepinephrine, atropine) within each experiment. Ventricular pacing increased MVO2 overproportionally up to 50% in relation to the hemodynamic determinants. Consequently, myocardial pumping efficiency markedly decreased with increasing ventricular rate. The close relation between directly measured MVO2 and Et, found in previous studies, was maintained under sympathetic stimulation. Atrial pacing, as compared to ventricular pacing at identical rates, resulted in a decrease of MVO2 up to 25% although the expected mVO2 according to its hemodynamic determinants rather increased. The hemodynamic and metabolic mechanisms probably responsible for the energetic difference between ventricular and atrial pacing at equal heart rates are discussed.

Animals↗
PubMedDate not supplied

The effect of ion composition on cellular membrane potentials during selective coronary arteriography.

An animal experimental study on seven thoracotomized dogs was designed to investigate the effects of intracoronarily injected sodium meglumine diatrizoate on myocardial electrophysiology and to evaluate the contribution of the corresponding changes of electrolyte levels in coronary blood. For this purpose the effects of alterations in the Na+-, K+- and Ca++-concentrations in coronary blood were studied separately by intracoronarily injected model solutions. Membrane potentials were recorded from the left ventricular myocardium by a modified microelectrode technique which is applicable to the beating and blood perfused heart in situ. Following selective coronary arteriography there was a temporary hyperpolarization of resting potentials and a prolongation of action potentials which may be explained by a contrast-induced local deficiency of potassium and calcium ions and by a relative prevalence of sodium ions in coronary blood. In selective coronary arteriography the synchronicity of cardiac excitation is disturbed by the regional prolongation of action potentials, which may induce ventricular arrhythmias.

Action Potentials↗