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Biomedical subjects

H Schieffer

Publications and source records attributed to H Schieffer.

At least 37 records · Page 2Linked to original sources
PubMed1988

Atrial signal variations and pacemaker malsensing during exercise: a study in the time and frequency domain.

To give some explanation for atrial malsensing in dual chamber pacing that occurs only during exercise, atrial electrograms from 33 patients were telemetrically recorded and analyzed in both the time and frequency domains. During exercise, an overall decrease from 6.4 +/- 1.9 to 5.6 +/- 1.9 mV (-11%) in the atrial signal amplitude was noted. Despite considerable variability among patients, marked changes occurred in 15 patients whose signals diminished by 11 to 49%. Slew rates showed a similar decrease from 1.35 +/- 0.45 to 1.18 +/- 0.45 V/s (-10.8%), with individual changes of as much as -51%. Signal attenuation in the time domain correlated well with frequency data, exhibiting a highly significant reduction of signal energy between 25 and 105 Hz. However, spectral distribution changed from rest to exercise, with a relative increase of signal energy in the range between 5 and 25 Hz and a decrease at higher frequencies. Individual changes differed widely when low (15 to 65 Hz) and high (65 to 115 Hz) frequencies were compared, but in a group of 11 patients signal attenuation in the high frequency band was more pronounced (-45%) than in the low frequency band (-23%). The clinical impact of the change in frequency distribution during ergometry was visualized by computer simulation of two different (low and high bandpass) filters. Although in individual patients, both characteristics may be favorable with respect to atrial sensing, it was observed in 11 patients that high pass filtering attenuates signal amplitudes by 10 to 24% in excess of the variation without filtering.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

[Isovolemic hemodilution in patients with coronary heart disease].

In the age of cellsavers patients suffering from coronary heart disease are diluted to a hematocrit of 20% or even less during a surgical intervention in the coronaries and they leave the operating room with a hematocrit of 30%. On the other hand, a hemodilution to a level of 30% in patients with coronary heart disease represents a contraindication due to the limited coronary reserve. On the occasion of the collection of autologue blood, before vascular surgery or for therapeutical hemodilution, the hematocrit was reduced from 45 to 35% by means of an isovolemic hemodilution with 500 ml of Haes 200/0.5 10% in 50 patients. In the load-ECG the pressure X frequency-product and the dyspnoe decreased significantly. The microcirculation in the nailfold and the systemical blood fluidity increased significantly. As in 22% of the patients a deterioration was stated, we propose to dilute all the patients who have to undergo a coronary vessel operation without exclusion criteria once isovolemically and to stress them before and afterwards. The patients having a clinical defict should be diluted intraoperatively only to 30% and postoperatively not under 35%.

Angina Pectoris↗
PubMed1988

[Dose-related effect of nicainoprol (CAS 924) on basic electrophysiologic parameters in patients with and without diseases of the heart conduction system].

The dose-dependent effects of nicainoprol (1 and 2 mg/kg/h), a new antiarrhythmic drug, on invasive electrophysiological parameters were evaluated in 28 patients during diagnostic electrophysiologic studies. The most pronounced effects by nicainoprol were observed on the specialized AV conduction system. The intranodal (1 mg/kg/h: A-H interval: 92 +/- 19 ms to 107 +/- 25 ms, p less than 0.002, n = 13; 2 mg/kg/h: 92 +/- 18 ms to 114 +/- 27 ms, p less than 0.001, n = 16) and, in particular, the infranodal conduction time (1 mg/kg/h: H-V interval: 45 +/- 5 ms to 52 +/- 9 ms, p less than 0.001, n = 15; 2 mg/kg/h: 45 +/- 6 ms to 58 +/- 10 ms, p less than 0.0001, n = 18) were delayed in a dose-dependent fashion. With the higher dose, there was a highly significant prolongation of the AV nodal Wenckebach cycle length (380 +/- 69 ms to 440 +/- 79 ms, p less than 0.0001, n = 13) as well as of the effective (368 +/- 112 ms to 428 +/- 108 ms, p less than 0.001, n = 12) and functional refractory periods (470 +/- 102 ms to 521 +/- 135 ms, p less than 0.001, n = 15). The intraatrial conduction time was slightly prolonged for both doses, the intraventricular conduction time increased significantly with the higher dose (89 +/- 12 ms to 102 +/- 19 ms, p less than 0.001, n = 19). In contrast, there were only small changes of right atrial and right ventricular refractorion.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1986

Withdrawal of long-term amrinone therapy in patients with congestive heart failure: a placebo controlled trial.

To verify favourable long-term effects, 14 patients with chronic congestive heart failure, NYHA class II-IV, who had been treated with oral amrinone for 8-15 months with apparent clinical benefit, had the drug withdrawn according to a 12 week placebo controlled double-blind crossover protocol. Evaluation was performed noninvasively by means of exercise stress test, echocardiogram, radionuclide angiography and systolic time intervals. None of these variables were significantly changed after discontinuation of amrinone, regardless of whether placebo was introduced during the first (group B, N = 7) or the second 6 week period (group A, N = 5), nor when the medication was finally openly withheld for another 6 weeks. In 2 further group A patients, premature termination of the trial was due to deterioration of symptoms on blinded amrinone. Hence, no sustained drug related effects could be proven by controlled withdrawal of long-term amrinone in this trial.

Adult↗
PubMed1985

[Atrial flutter and atrial fibrillation by DDD stimulation].

136 patients were followed after implantation a DDD pacemaker (PM) for a total of 1,919 patient-months (m = 14.1 months/patient). 22/136 patients had one or more episodes of atrial flutter or fibrillation (AF) postoperatively. In 121/136 patients (group A) AF had not been documented before, in 4 it was unknown at the time of implantation, but was verified retrospectively (group B). 11 patients (group C) had a positive history of previous AF. Post implantation 7.4% in group A and 81.8% in group C developed AF. In patients with sick sinus syndrome (SSS) the incidence was 10/37 (27%), in those with AV block (AV) 6/77 (7.8%) and in cases with both SSS and AV 6/22 (27.3%). The first AF episode occurred during the implantation itself (n = 2) or during the hospital course in 9/22 patients (A: 11%, B/C: 64% early attacks), and later on in 13 with a time delay of 1-24 months (m = 8.5, 8 patients) in group A and 2-15 months (m = 6.6, 4 patients) in groups B/C. 2 patients of group C had no AF episodes post implantation. In the individual patient the number of attacks ranged from 1 to 3 (10.4/100 patient-months) in group A and from 1 to 6 (20.1/100 patient-months) in groups B/C. During AF 16/22 patients had a ventricular rate of 110-185, m = 132 bpm. In 6 patients the tachycardia was mediated by the PM and in 10 by fast intrinsic AV conduction. 1 patient with SSS, 2 with SSS + AV (spontaneous ventricular rate less than 45 bpm) and 3 with AV needed ventricular backup-pacing during AF. In 7 patients a total of 15 attacks of atrial flutter could be terminated by atrial overdrive pacing, in 5 of these episodes by temporary high rate A00 stimulation via the implanted pacemaker lead system. Otherwise AF was converted to sinus rhythm by antiarrhythmic drugs. After termination AF often recurred, but only 3 patients developed chronic atrial fibrillation. In 2 patients a ventricular rate greater than 180 bpm during AF reverted the PM to asynchronous mode, a possible cause of ventricular fibrillation in one. No other complications due to the PM itself have been encountered. AF, therefore, common during DDD pacing, even in patients without any AF history before implant. Both the incidence and the recurrence of AF depend on the presence or absence of previous atrial arrhythmias.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1979

Hemodynamic effects of pentazocine in acute myocardial infarction.

In 12 patients with acute myocardial infarction the hemodynamic effects of a single intravenous injection of 30 mg of pentazocine were investigated. The administration of pentazocine resulted in no significant hemodynamic changes. In particular, there was no increase in peripheral vascular resistance and no evidence of decreased left ventricular function or respiratory depression. In the occasional patients who demonstrated an elevation of pulmonary arterial pressure, it was probably due to a direct effect of the drug on the pulmonary vasculature.

Aged↗
PubMed1978

[The effects of oxyfedrine on the hemodynamics of patients with acute myocardial infarction].

In 16 patients with acute transmural myocardial infarction the effect of 8 mg of intravenous oxyfedrine followed by an infusion of 0.3 mg/kg body weight per hour on haemodynamics of the pulmonary and systemic circulation and dynamic cardiac indices was investigated. Cardiac rate, systemic arterial blood pressure, minute volume, cardiac output, and tension-time index remained unchanged on the whole. On the other hand oxyfedrine produced a persistant significant decrease of the mean and diastolic pulmonary artery pressure, pulmonary capillary pressure, and of the contraction and pressure-increase time. These effects were also demonstrable in patients previously treated with digitalis. No cardiac arrhythmias were observed. The positive inotropic effect of oxyfedrine is suggested as reason for these changes.

Aged↗
PubMed1978

[Effects of oxyfedrine on haemodynamics in patients with acute myocardial infarction (author's transl)].

In 16 patients with acute transmural myocardial infarction the effect of 8 mg of intravenous oxyfedrine followed by an infusion of 0.3 mg/kg body weight per hour on haemodynamics of the pulmonary and systemic circulation and dynamic cardiac indices was investigated. Cardiac rate, systemic arterial blood pressure, minute volume, cardiac output, and tension-time index remained unchanged on the whole. On the other hand oxyfedrine produced a persistant significant decrease of the mean and diastolic pulmonary artery pressure, pulmonary capillary pressure, and of the contraction and pressure-increase time. These effects were also demonstrable in patients previously treated with digitalis. No cardiac arrhythmias were observed. The positive inotropic effect of oxyfedrine is suggested as reason for these changes.

Aged↗
PubMed1978

[Coincidence of malformations of the cardiovascular system as well as of the kidneys and of the efferent urinary tract (author's transl)].

Excretion urograms were prepared subsequent to angiocardiograph in a total of 115 cardiac catheter examinations. 104 of these examinations were evaluated. In 17 cases (16.3%), malformation of the kidney or the ureter was found. In consideration of the fact that such fundings are often directly linked to therapeutic consequences (plastic operations), the additional preparation of an excretion urogram is indicated during cardiac catheter examinations.

Angiocardiography↗
PubMed1976

[Effect of cardiac catheter investigations and angiocardiography on enzyme activity in serum (author's transl)].

The serum activities of LDH, alpha-HBDH, CK, GOT and GPT wer investigated in 124 patients who had undergone cardiac catheterization with angiocardiography or coronary angiography. The determinations were made before and 2, 16 and 40 hours after the investigation. There was no significant influence on the enzyme activities. Lengthy intracardial catheter manipulation, trans-septal puncture and ventriculography may cause transient clinically unimportant increases in activity, especially of CK within normal limits. Distinctly pathological enzyme values were only measured in individual cases of intramyocardial contrast media depots after ventriculogram.

Adult↗
PubMed1976

[Influence of a pressure agent on blood concentrations of glucose, lactate, pyruvate and free fatty acids (author's transl)].

In 34 unselected patients blood concentrations of glucose, lactate, pyruvate and free fatty acids (FFA) were determined after i.v. injection of a pressure agent containing theophylline esterified with norephedrine and theophylline esterified with norepinephrine (Akrinor) with and without beta-adrenergic blockade. After Akrinor a significant increase of FFA concentration of 32% is observed, which can be abolished by beta-receptor blocking agents. Our findings indicate that the Akrinor-induced lipolysis is mainly due to a direct sympathomimetic effect on the beta-receptors of adipose tissue. there are only slight effects on carbohydrate metabolism (decrease of pyruvate concentration, increase of lactate/pyruvate ratio) which are not influenced by beta-receptor blockade. According to our results there are important metabolic differences between Akrinor and the classical catecholamines.

Blood Glucose↗
PubMed1975

[Effect of Akrinor on cardiovascular-dynamics before and after blockade of adrenergic beta-receptors by propranolol].

On healthy volunteers it is tested whether the cardiovascular and central stimulating effect of Akrinor and the depressive effect of propranolol influence each other mutually. Akrinor causes an increase in arterial pressure, in cardiac stroke volume and cardiac output in connection with a decrease in peripheral vascular resistance and in heart rate. These changes are abolished by propranolol whereas the central stimulating effect on the respiratory minute volume and the oxygen consumption is not influenced. After blocking of the beta-receptors, Akrinor exerts a diminished influence on the cardiovascular dynamics, a stimulation of the alpha-receptors cannot be evidenced. The findings are being discussed and compared with the effect of noradrenaline and adrenaline.

Drug Combinations↗