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Biomedical subjects

G Fröhlig

Publications and source records attributed to G Fröhlig.

16 recordsLinked to original sources
PubMed1992

Reliability of an automatic sensing algorithm.

Automatic adaptation of the atrial sensitivity was evaluated in 18 patients with dual chamber pacemakers (Intermedics, Inc., Relay) in the unipolar mode. After atrial sensitivity was stabilized in the upright position, patients underwent a 1.0 W/kg body weight exercise for 5 minutes. A 24-hour Holter ECG was recorded, and the maximum and minimum atrial sensitivity values reached were stored in the memory of the pulse generator. In a second series of 12 patients, Holter ECGs were recorded twice, starting with the same sensitivity but with automatic adaptation alternately switched "on" or "off." Results of the exercise test: mean atrial sensitivity declined from 2.30 +/- 0.77 mV to 2.03 +/- 0.68 mV. There was no change in five patients, a slight increase in two patients, and lowering of the atrial sensitivity was observed in 11 patients, the difference ranging from 0.2 to 1.0 mV. A total of two P waves in two patients were missed by the atrial amplifier. The minimum and maximum sensitivity reached during Holter monitoring averaged 2.31 +/- 0.67 mV versus 1.72 +/- 0.71 mV (difference 0-1.7 mV). Normal pacemaker function was found in six patients, including one patient without any intrinsic atrial activity. Malsensing of less than five P waves occurred in four patients. More than 50 sensing defects resulted from ectopic atrial beats (four patients). We observed atrial oversensing in three cases; one patient showed atrial over- and undersensing. The comparison between fixed and variable sensitivity did not reveal any superiority of automatic adaptation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Threshold and polarization properties of modern active fixation atrial leads.

The purpose of the study was to compare the stimulation characteristics of two modern active fixation leads (Ela 583F, vitreous carbon tip [ELA] and Intermedics 82-0008-1601, iridium oxide tip [IROX]) with a standard lead (Osypka KY 67 VC, carbon-covered elgiloy tip [OSY]). In three groups of ten patients each, minimum charge threshold delta Qmin and polarization properties were determined via charge telemetry of the pacemaker (Intermedics Cosmos II and Relay) 0, 2, 5, 10, 28, 90, and 180 days after implant (dai). The polarization parameters global capacitance Cg, global resistance Rg, polarization voltage U(p), and a time constant t* (t* = Cg.Rg) were obtained by nonlinear regression. U(p) was always significantly (sig) lower in ELA and IROX (0.04-0.10 V) compared to OSY (0.54-0.76 V). Rg was sig lower in ELA (330-437 omega) compared to OSY and IROX (414-588 omega) from 0 to 28 dai. From 2 to 10 dai, Cg was sig higher in ELA and IROX (3.8-4.2 microF) compared to OSY (3.3-3.4 microF). In the three groups, delta Qmin reached a comparable maximum (1-1.2 microC) at 5 dai. Therefore, vitreous carbon and iridium oxide atrial fixation leads exhibit low chronic polarization effects compared to a standard elgiloy lead, but do not show a sig reduction in charge threshold.

Aged↗
PubMed1991

[Cardiac metastasis as cause of therapy-resistant heart failure].

Ultrasonography revealed a renal tumour (4 x 4 cm) in a 67-year-old man with right-sided lumbar pain and macrohematuria. In addition he had marked nocturnal dyspnoea with dry cough. He had lost about 10 kg in weight. On admission he had atrial fibrillation with an irregular ventricular rate (140 beats/min) and engorgement of the neck veins. Two-dimensional echocardiography, undertaken because of signs of increasing heart failure and a fall of systolic blood pressure to below 100 mm Hg, demonstrated a space-occupying lesion in the right ventricle, 4 x 2 x 1 cm, indicating an intracardiac thrombus or solid tumour. The heart failure continued to worsen, despite treatment with cardiac glycosides, verapamil and diuretics. Hence an exploratory thoracotomy was performed. This revealed an intracardiac tumour which had markedly displaced the right ventricular inflow tract and infiltrated the entire myocardium, but not the tricuspid valve. As much of the tumour as possible was resected, but the patient died postoperatively of heart failure. The intracardiac tumour proved to be a metastasis from the papillary carcinoma of the kidney. This had infiltrated the renal capsule and pelvis and invaded the branches of the right renal vein.

Aged↗
PubMed1991

Loss of atrial signal detection with increasing sensitivity settings: a software problem and its practical solution.

A logic error in the software of Cosmos II results in apparent malsensing of atrial signals at high rather than low sensitivity settings. The paradoxical function was found in 54 out of 87 units tested (= 62%) if the atrial sensitivity was increased and in 54 out of 87 units tested (= 62%) if the atrial sensitivity was increased and the ventricular refractory period was lengthened beyond critical limits that could be defined individually. The problem inherent in both unipolar (66%) and bipolar systems (54%) is attributed to a summation of a physiological signal and internal noise, which has to be detected at the atrial level within a specific timing window to disable atrial sensing for the next pacing cycle. The malfunction virtually disappears if the ventricular refractory period does not exceed 210 msec. It is recommended, therefore, that Cosmos II pacemakers be left at their nominal ventricular refractory value (200 msec).

Adult↗
PubMed1990

Optimised function for determining time to peak creatine kinase and creatine kinase-MB as non-invasive reperfusion indicators after thrombolytic therapy in acute myocardial infarction.

STUDY OBJECTIVE: The aim of the study was to investigate the use of an optimised function to approximate and interpolate the time course of serum creatine kinase and creatine kinase-MB values after thrombolytic therapy in acute myocardial infarction. DESIGN: A three parameter interpolating function was developed which approximates the time course of serum enzyme levels. In the proposed function, time to peak creatine kinase and maximum of creatine kinase determined from raw data were used as starting parameters of the non-linear interpolation routine, thus providing ideal starting conditions for the iteration. The efficacy of the function was compared with that of three other functions cited in published reports (log-normal distribution function, modified gamma density function, three compartment function). SUBJECTS: Serum enzyme data from 20 patients with acute myocardial infarction were used in the comparisons. The patients have all been treated with anisoylated plasminogen streptokinase activator complex. RESULTS: In comparison with the other models, deviations of the experimental model function from the raw data were minimal. The fit remained stable for time intervals between blood samples of up to 6 h. CONCLUSIONS - Due to its numerical stability, the function outlined in this study is suitable for large clinical reperfusion trials. In the case of uncomplicated infarctions without thrombolytic therapy, the area under the creatine kinase activity curve could be directly calculated in terms of maximum activity and time to peak.

Anistreplase↗
PubMed1990

[Third replacement of the tricuspid valve in combined aortic-tricuspid defect].

The implantation of valvular prostheses in tricuspid position is problematic due to the slow blood flow in the low-pressure system with the risk of valvular thromboses. Today there are prostheses with supportable low transvalvular gradients; nevertheless, the risk of valvular thromboses is, in spite of anticoagulation, increased by using mechanical prostheses in tricuspid position. We report on a 51-year-old woman in whom a dysfunction of the Starr Edwards ball prosthesis 15 years after its implantation in the tricuspid position was diagnosed. The prosthesis, which was unable to function due to connective tissue proliferation, was replaced by a St. Jude Medical prosthetic valve, which also presented a disturbed function a few days after the implantation. Because of a suspected valve thrombosis the patient was treated with rt-PA-lysis which proved to be ineffective. Thus it was inevitable to implant a third tricuspid valve; this time a bioprosthesis was used.

Aortic Valve↗
PubMed1989

Multiple cutaneous myxomas coinciding with repeated cardiac myxomas. A syndrome.

We report on a 31-year-old woman who underwent surgery for two metachronous cardiac myxomas - 7 and 9 years after excision of several cutaneous myxomas. Our observation is a further case of a syndrome-like complex of cardiac and cutaneous myxoma(s), pigmentation anomalies and endocrine disorders described only recently. As modern investigative methods and the development of cardiovascular surgery have brought about an essential improvement in diagnostics and prognosis of cardiac myxomas, the knowledge of this syndrome-like complex is of great therapeutic importance. Therefore, in our opinion, echocardiographic investigations are strongly recommended even in asymptomatic patients, once several cutaneous myxomas are diagnosed histologically.

Adult↗
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

Atrial sensing performance of AV universal pacemakers during exercise.

To investigate the atrial sensing function of dual chamber pacemakers during exercise, we studied 57 patients aged 12 to 81 years (m = 65). They were paced for sinoatrial disorders (n = 15), second or third degree AV block (n = 37), or binodal disease (n = 11). The examination was performed 3-24 months (m = 11) after pacemaker implantation. Individual sensing thresholds were determined at rest in the supine position, and proper detection of atrial signals at the programmed sensitivity level was verified during a period of 5-9 minutes (m = 5.8). Without a change in the program of the unit, symptom-limited bicycle ergometry was performed at a maximum load of 25-200 Watts (m = 95) and 6-channel chest wall electrocardiograms were continuously recorded throughout the test, including recovery. During exercise, 25/57 patients (44%) exhibited poor atrial sensing of the pulse generator; after termination of exercise in 16 of the 25 patients, proper atrial sensing resumed within 1 to 7 minutes of recovery. In the remaining nine cases, ergometry was continued after lowering the sensitivity threshold to half the initial setting or, depending on the pacemaker model, by a value of 0.4 mV. This resulted in normal function of the pulse generator in all patients but one, who needed a sensitivity adjustment of another 0.4 mV. In a subgroup of 25 patients, telemetric atrial electrogram recordings were monitored during ergometry, 19 of which could be evaluated quantitatively. Besides random atrial signal variations, presumably due to ectopic beats or runs, a systematic decrease of the peak-to-peak amplitude by 0.1 to 1.6 mV (3-30%) was observed in 16/19 patients during exercise. Mean signal reduction amounted to 11.8% and was statistically significant at the 0.1% level. It is concluded from these findings that, besides testing of atrial sensing at rest, the follow-up of dual chamber pacemakers should include an exercise test.

Adolescent↗
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↗
PubMed1986

Noise reversion of a dual chamber pacemaker without noise.

Three patients are reported whose DDD pacemakers reverted to the asynchronous mode in the absence of skeletal muscle or electromagnetic (EMI) interference. In all three cases, the basic cardiac rhythm was atrial fibrillation with fast ventricular response due to intrinsic AV conduction. Noise reversion was triggered by the patients' own ventricular activity at cycle lengths shorter than the ventricular refractory period of the pulse generator. In one patient, asynchronous AV sequential pacing during atrial fibrillation was noted shortly after resuscitation from ventricular fibrillation; however, the initiation of the malignant ventricular arrhythmia by the pacemaker remains unproven. The mechanism of noise reversion by rapid cardiac activity and possible solutions to the problem by adequate pacemaker design are discussed.

Aged↗
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↗
PubMedDate not supplied

Electrophysiological effects of a new antiarrhythmic agent, nicainoprol, in humans.

The electrophysiological effects of nicainoprol, a new antiarrhythmic drug, were evaluated in a heterogeneous group of 23 patients aged 59 +/- 15 (mean +/- standard deviation) years. Nicainoprol was administered intravenously as a bolus of 1-2 mg/kg followed by continuous infusion at two dose levels. Electrophysiologic study was performed before and during the infusion at a steady-state drug level on each dose. The sinus node recovery time was unaltered in patients with normal sinus node function and was markedly prolonged in three of six patients with sinus node dysfunction. The intranodal conduction time (p less than 0.01) and the infranodal conduction time (p less than 0.001) increased, and the QRS duration (p less than 0.05) lengthened significantly even during 1 mg/kg/h. During 2 mg/kg/h, these times were further prolonged and, in addition, the intra-atrial conduction time (p less than 0.05), atrioventricular nodal effective and functional refractory periods (p less than 0.01), as well as the Wenckebach cycle length (p less than 0.001) also increased significantly. Similar depressant effects on the retrograde ventriculoatrial conduction system were also produced by nicainoprol. Retrograde His-atrioventricular nodal conduction was blocked in six of eight patients with this condition and was prolonged in the remaining two. Sustained supraventricular tachycardia was induced in seven patients, five of whom received nicainoprol during the tachycardia. The termination of supraventricular tachycardia was exclusively due to ventriculoatrial block in all five subjects, three with orthodromic circus movement tachycardia and two with atrioventricular nodal reentrant tachycardia of the slow-fast type. The reinducibility of supraventricular tachycardia could be prevented in five of seven patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗