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Biomedical subjects

J Brachmann

Publications and source records attributed to J Brachmann.

At least 145 records · Page 8Linked to original sources
PubMed1980

[Current state of myeloscintography. A 10 year analysis of 1000 examinations].

The current relative importance of nyeloscintigraphy is determined on the basis of more than 1,000 examinations over a period of ten years. Owing to its high sensivity the method is suited to early diagnosis and diagnosis by elimination for growing and displacing spinal processes and affections of the cerebrospinal fluid passage. In the case of pathological disturbances, the lack of specificness in the findings, especially in the cervical region, indicates further systematic contrast medium examinations.

Humans↗
PubMed1979

Effect of hypoxia on the sinoatrial node, atrium, and atrioventricular node in the rabbit heart.

We used intracellular microelectrodes to study the effects of hypoxia on the isolated, superfused sinoatrial (SA) node, atrium, and atrioventricular (AV) node of the rabbit heart. Hypoxia decreased the rate of spontaneous impulse initiation in SA nodal fibers by decreasing the slope of diastolic depolarization. With gradually decreasing Po2, the sinus rate was reduced; concomitantly, the corrected sinus node recovery time after rapid atrial stimulation was much less affected demonstrating marked prolongation only under severe anoxic conditions. Hypoxia decreased the amplitude of action potentials of the SA node and of the AV node but not of the atrium. SA and AV nodal conduction were slowed by hypoxia; intraatrial conduction was not significantly affected. AV nodal conduction block occurred at lower atrial rates, and the effective refractory period of the AV node was prolonged. Inhomogeneity of SA and AV nodal impulse propagation often was observed in the presence of hypoxia. This was associated with concealed reentry within both nodal areas. The extracellular K+ concentration of the atrial tissue was measured with ion-sensitive microelectrodes. [K+]o remained unchanged even after prolonged periods of severe hypoxia. These results are consistent with the hypothesis that acute hypoxia predominantly inhibits slow response activity but has only little effect on the fast inward sodium current.

Action Potentials↗
PubMed1979

Effects of some components of ischemia on electrical activity and reentry in the canine ventricular conducting system.

We used intracellular microelectrodes to study the electrophysiological effects of combinations of components of ischemia and their relation to the occurrence of ventricular arrhythmias in the specialized conducting system of isolated canine right ventricles. The middle area of the free wall was exposed to various test solutions in the center compartment of a three-chambered bath; the base and apex of the preparation were superfused with normal Tyrode's solution in the outer control compartments. Hypoxia (Po2 40 mm Hg), lactic acidosis (pH 6.5), and orciprenaline (10(-6) M), either alone or combined, failed to affect the action potential amplitude or the conduction velocity of the subendocardial fibers, and no arrhythmias occurred. The action potential duration and the effective refractory period were markedly prolonged by lactic acidosis. Exposure of the test regions to 15 mM K+ plus orciprenaline resulted in marked decreases in action potential amplitude and conduction velocity. Abnormalities of impulse transmission through the depressed area included high degrees of rate-dependent block, one-way block, warming-up phenomenon, and the Wenckebach phenomenon. Such conditions regularly provoked the appearance of single, sustained, or concealed reentrant depolarizations. The combined effects of hypoxia, 15 mM K+, and orciprenaline resulted in further depression of the already depressed action potential in the depolarized fibers. Our results indicate that regional increases of extracellular K+ may be the predominant factor of the components of ischemia we studied which facilitates the initiation of reentrant arrhythmias.

Acidosis↗
PubMed1979

Nitrates and ectopic ventricular activity in mitral valve prolapse: clinical and experimental data.

Three patients with mitral valve prolapse, high grade ventricular arrhythmias and a strong family history of sudden death were studied utilizing continuous Ecg monitoring and intracardiac stimulation and recording techniques. Analysis of 6-hour ambulatory Ecgs revealed frequent premature ventricular beats (PVBs) including repetitive and multiform PVBs in each patient. The electrophysiological studies demonstrated normal parameters of intracardiac conduction and refractoriness providing no evidence for reentrant mechanisms. Acute drug testing with 0.4 mg sublingual nitroglycerin completely suppressed all ventricular arrhythmias. During maintenance therapy antiarrhythmic nitrate efficacy was only partly confirmed monitoring the effects of 4 x20 mg isosorbide dinitrate on 6-hour ambulatory Ecgs. The electrophysiological parameters of intracardiac conduction and refractoriness were not significantly altered by 0.4 mg sublingual nitroglycerin. Experimental data obtained from isolated rabbit atria and canine ventricles revealed no significant action of nitroglycerin in the parameters of cardiac automaticity and conduction including transmembrane electrical activity of normal and hypoxically damaged SA nodal, atrial and ventricular fibers. It is concluded that a) PVBs in patients with mitral prolapse appear related to ectopic automaticity; b)nitrates may suppress ventricular ectopy in these patients; c) antiarrhythmic nitrate efficacy is not related to direct membrane effects.

Animals↗
PubMed1977

[Comparison of myeloscintigraphy and myelography with positive contrast media (Dimer-X) in the diagnosis of intervertebral disk prolapse].

When comparing myeloscintigraphy with positive myelography (Dimer X) in the diagnosis of the lumbar prolapse of intervertebral disks, identical findings were obtained in 17 out of 24 cases. Of these, both methods showed pathological findings in 12 cases and normal conditions in 5 cases. Only in 5 pathological myeloscintigrams normal Dimer X myelograms were obtained and in 2 myeloscintigrams judged as normal the positive myelograms were pathologic. With a good correlation of the two methods in typical cases the Dimer X myelogram, however, offers the advantage of the possibility of examining in several planes under constant reference to the vertebral column. Owing to the good tolerance, myeloscintigraphy should be used in screening diagnoses and in cases where also thoracic parts have to be included in the examination.

Humans↗
PubMedDate not supplied

Significance of cardiac innervation on spontaneous ventricular arrhythmias elicited by left stellate ganglion stimulation in dogs 4 days after myocardial infarction: comparison of two experimental models.

The effects of cardiac sympathetic overactivity on spontaneous arrhythmias and transmural left ventricular effective refractory period (LVERP) were assessed by left stellate stimulation (LSS) in 16 anesthetized dogs. The experiments were performed 4 days after proximal occlusion of the left anterior descending (LAD) coronary artery produced by either ligation (9 dogs) or embolization with histoacryl (7 dogs). The innervation of left ventricular myocardium was studied by light and electron microscopies. Synaptophysin (SYN)- and neuropeptide Y (NPY)-immunoreactive nerve fibers and terminals were thereby detected. In dogs subjected to ligation, LSS elicited negligible arrhythmias in spite of a decrease in LVERP by 6.9 +/- 2.2% (mean +/- SD, p < 0.001). However, dogs with intravascular occlusion were more susceptible to LSS, as indicated by development of sustained ventricular rhythms. In these animals, the LVERP decreased with LSS by 14.6 +/- 3.4% (p < 0.001). The innervation of the anterior left ventricular wall distal to the place of occlusion revealed a higher reduction of SYN- and NPY-immunoreactive nerves in infarcted myocardium and a more heterogeneous distribution of nerves in undamaged regions after ligation, compared to intravascular occlusion. Ultrastructurally, nerve terminals containing small agranular and large dense-core vesicles were found innervating ischemically damaged myocardiocytes. Our findings indicate a higher preservation of nerves in infarcted and noninfarcted myocardium of animals subjected to embolic occlusion of the LAD. Because LSS apparently elicited more arrhythmias in these animals, we suggested a proarrhythmic effect of intact myocardial innervation after infarction.

Animals↗
PubMedDate not supplied

Intropic and electrophysiological action of humoral factors released in cardiogenic shock after acute myocardial infarction.

The inotropic and electrophysiological effects of plasma obtained from patients and experimental dogs during cardiogenic shock following acute myocardial infarction were studied. Changes in the isometric contraction and the intracellular action potential were determined in isolated papillary muscles of rabbits. Control plasma collected from normal subjects produced no significant changes in the contraction or the electrical parameters. Plasma from shock patients decreased peak force by 42% and the maximum rate of force development by 38% in comparison to control values; the time to peak of contraction, the relaxation time and the action potential parameters were not significantly altered. Corresponding results were obtained with plasma from dogs before and during experimental cardiogenic shock. Biochemical determinations failed to identify a single specific "myocardial depressant factor" in the plasma of patients and dogs with cardiogenic shock. The results suggest that (1) various humoral factors released during cardiogenic shock may depress the contractile function of cardiac muscle and (2) that the observed negative intropic effect is not due to electrical changes in the cell membrane.

Action Potentials↗
PubMedDate not supplied

Effects of acute vagally-mediated bradycardia on systemic hemodynamics and coronary blood flow before and after coronary stenosis.

The effects of short episodes (1 min) of vagally-mediated bradycardia were studied in 9 anesthetized dogs utilizing vagal stimulation and slow atrial pacing (120 and 80 beats/min) before and after graded coronary constriction of the left anterior descending (LAD) and the left circumflex (CCA). In the presence of 90% LAD stenosis, bradycardia tended to restore both the elevated total LAD coronary vascular resistance (CVR-LAD) and the reduced, total CVR-CCA towards control levels obtained at corresponding slow rates in the absence of coronary stenosis; as a result, LAD coronary flow (F-LAD) was relatively less reduced and the accessory rise of F-CCA disappeared. In the presence of combination of 90% LAD plus 70% CCA stenosis, the effects of bradycardia on total CVR-LAD and F-LAD were similar to those obtained with single 90% LAD stenosis, but the accessory flow through the CCA was abolished resulting in no significant difference of the rate-dependent alterations of total CVR-CCA and F-CCA as compared with those observed in the absence of coronary stenosis. In the presence of single or combined coronary stenosis, bradycardia restored the depressed aortic pressure and cardiac output towards control values obtained at comparable slow rates before coronary stenosis. The results support the concept that in the presence of 90% LAD stenosis vagally-mediated bradycardia 1) decreases the tension-time index (myocardial nutritional demand) shifting cardiac performance to less expensive "flow work" and 2) facilitates antegrade flow through the highly stenotic LAD thereby inhibiting accessory flow through the nonstenotic CCA.

Animals↗