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Biomedical subjects

E Hoffmann

Publications and source records attributed to E Hoffmann.

At least 127 records · Page 7Linked to original sources
PubMed1995

Failures of epicardial and transvenous leads for implantable cardioverter defibrillators.

Lead failures constitute a major risk for patients with an implantable cardioverter defibrillator (ICD). However, data about the incidence and patterns of ICD-lead failures in a larger population are lacking. We analyzed the short-term and midterm performance of 27 epicardial and 103 nonthoracotomy ICD-lead systems during a follow-up period of 36 +/- 21 months and 22 +/- 10 months, respectively (p < 0.05). The failure rate was 5 (19%) of 27 in the epicardial and 6 (6%) of 103 in the nonthoracotomy group (p < 0.05). The most common symptom was erroneous detection of ventricular fibrillation from artifact sensing in five patients. Two patients had to be resuscitated because of failure to defibrillate. Loss of pacing and loss of sensing were seen in two patients. Only two asymptomatic lead fractures could be diagnosed on routine radiograph. In conclusion, there was a considerable rate of lead failures, especially in epicardial systems. Long-term studies addressing the longevity of ICD leads, mechanisms of their failures, and improved diagnostic facilities are important to further increase the safety of this therapeutic approach.

Defibrillators, Implantable↗
PubMed1995

Defibrillator implantation in a patient with a persistent left superior vena cava.

The implantation of a transvenous cardioverter defibrillator (PCD 7217B) was performed in a patient with a persistent left superior vena cava. The defibrillation electrodes were positioned in the right ventricle and the superior vena cava via the right subclavian vein. A subcutaneous patch had to be implanted at the left lateral chest wall to achieve sufficient defibrillation thresholds. Three weeks later the system had to be removed because of a generator pocket infection. During the second implantation we placed one electrode in the persistent left superior vena cava perpendicular to the electrode in the right ventricle. Using this configuration transvenous defibrillation was possible without an additional subcutaneous patch.

Adult↗
PubMed1995

The left subclavian vein as an alternative site for implantation of the second defibrillation lead.

The optimal placement for the second defibrillation lead in a two-lead system has never been addressed. We retrospectively reviewed the data of 33 patients with an average age of 59.2 years (range 41-78 years), predominantly male (n = 29), who underwent implantation of a cardioverter defibrillator (ICD) for treatment of ventricular tachycardia (n = 19) or ventricular fibrillation (n = 14). In all patients an attempt was made to implant an endovenous ICD device (leads only, no subcutaneous patch). In group I (n = 18) the defibrillation anode, a separate unipolar lead, was placed in the common position, the superior vena cava. In group II (n = 15) the lead was placed in the left subclavian vein. At least two consecutive shocks reverting ventricular fibrillation at energies < or = 24 J were required for implantation of the ICD device. All shocks were monophasic. The success rate of endovenous defibrillation was significantly higher in group II than in group I (67% vs 28%, P < 0.05). Thus, it could be demonstrated that the position of the defibrillation anode can influence the defibrillation efficacy in transvenous ICD systems. Prospective randomized trials are needed to investigate the optimal position for the second defibrillation electrode, which may gain increasing importance as soon as dual chamber ICDs become available.

Adult↗
PubMed1995

Electrofusion of plant cell protoplasts under microgravity--a D-2 spacelab experiment.

Plant cell protoplasts, derived from sexually incompatible plant species, have proved to be a good system for somatic hybridization by electrofusion. Under microgravity, an increase in fusion yield can be expected, especially if the parental cells differ markedly in size or specific density. On the D-2 spacelab mission flown in 1993, electrofusion experiments were performed with three different objects, i.e. tobacco as model system, Helianthus as an important crop, and Digitalis as a plant of pharmacological interest. The resulting fusion products were cultivated (along with parental cells) for 10 days under microgravity, and subsequently regenerated on ground for biochemical analysis. Results are presented on the observation of the fusion process during flight, heterofusion yields, ultrastructural investigation of fusion products immediately after fusion, and characterization of the resulting hybrids. The results are interpreted on the background of earlier microgravity-experiments on sounding rockets or parabolic flights.

Cardenolides↗
PubMed1995

[Determination of the degree of stenosis of the internal carotid artery in the surgical specimen after eversion TEA: comparison with angiography and c-w-Doppler ultrasound].

UNLABELLED: 22 carotid specimens following eversion-endarterectomy were compared with preoperative assessment of carotid stenosis obtained angiographically and by c-w-Doppler-sonography. The intact, unsplit specimens were perfused with a liquid plastic material (Palavit M). After hardening of the plastic material the specimens were removed. The local degree of carotid stenosis with respect to diameter reduction was assessed by direct measurement of the plastic specimens at the narrowest site compared with the diameter of the carotid eversion specimens at the place of the maximum stenosis. The distal degree of carotid stenosis was assessed by comparison of the diameter of the distal internal carotid artery obtained intraoperatively with the measurements of the plastic specimens (1 mm vascular wall thickness of distal internal carotid artery was taken into account). RESULTS: Both the local and the distal degree of carotid stenosis diameter (mean 84.7% +/- 8.4% and 82.1% +/- 9.1% respectively) were underestimated in the preoperative angiogram (79.8 +/- 9% by ECST-criteria and 69 +/- 10.3% by NASCET-criteria) in most of the cases. The difference of the diameter reduction was statistically significant (p < 0.05 and p < 0.01 respectively, Wilcoxon signed rank test). The c-w-Doppler assessments were 82.6 +/- 8.2% (n.s.). CONCLUSION: Our results suggest that the preoperative assessment of internal carotid stenosis obtained angiographically or by c-w-Doppler-sonography easily underestimate the true degree of carotid stenosis.

Adult↗
PubMed1995

[Aortic isthmic stenosis: clinical study and postoperative follow-up by MRI. Report of a case].

A case report. Nuclear Magnetic Resonance (NMR) is the most recent non-invasive diagnostic technique which can provide high quality anatomic and functional data. The absolute safety of the method make it suitable for follow-up of patients who have undergone aortic surgery. The authors report the case of a 12-year-old girl suffering from isthmic coarctation of the aorta for which both traditional methods (echocardiography and angiography) and NMR were used. Following bypass surgery with a dacron implant in the stenotic tract of the aorta, the patient was followed up using transthoracic echocardiogram and NMR. The latter method was found to be most efficacious in providing anatomic and functional information after surgery, enabling an optimal follow-up of these patients.

Angiography↗
PubMed1995

Comparison of song frequency and receptor tuning in two closely related bushcricket species.

The songs and the structure and physiology of the auditory organs in the closely related bushcricket species Tettigonia viridissima and Tettigonia cantans were investigated comparatively using bioacoustical, histological and neurophysiological methods. The morphology of the crista acustica, the main auditory receptor organ, is very similar in the two species in respect to both the distribution of scolopidia along the length axis of the crista and the dimensions of corresponding scolopidia and attachment structures. The only obvious difference is that T. viridissima has one more scolopidium in the crista acustica and that the overall length of the crista is by about 50 microns larger than in T. cantans. In contrast, differences were found in the physiology of individual auditory receptor cells. Comparison of the threshold characteristics of all the receptor cells of the crista acustica in both species reveals a differential sensitivity of groups of auditory receptor cells at dominant frequencies of the song. In each species, the sensitivity of auditory receptor cells is method to the energy spectrum of the song. These differences in the physiology can partly be explained by differences in transmission characteristics of the acoustic trachea.

Animals↗
PubMed1994

A single stem-loop structure within the HTLV-1 Rex response element is sufficient to mediate Rex activity in vivo.

The human T-cell leukemia virus (HTLV-1) Rex protein is required for the cytoplasmic expression of the incompletely spliced transcripts that encode the viral structural proteins. This effect is mediated by a highly structured cis-acting RNA element of 254 nucleotides termed the Rex response element, or RexRE. Here we demonstrate that one of the four known RexRE stem-loop structures as well as a 43-nt segment derived from this element is sufficient to mediate Rex function in vivo. Upon duplication, this stem-loop is shown to function as efficiently as the full-length RexRE. In vitro RNA binding analyses with wildtype and mutagenized RNA show that this stem-loop contains a high affinity binding site for Rex that coincides with a predicted bulge structure in the central part of this stem-loop. These results indicate that a small region of the RexRE containing a high affinity binding site is sufficient to mediate Rex function and suggest that sequences outside of this binding site have no unique role in mediating Rex regulation.

Base Sequence↗
PubMed1994

Hemodynamic deterioration during ICD implant: predictors of high-risk patients.

Defibrillation threshold (DFT) testing during implantation of the cardioverter defibrillator is associated with hemodynamic deterioration and pump failure in many patients. We investigated the influence of DFT testing on cardiac function intraoperatively using a balloon-tipped catheter. In 13 consecutive patients with a nonthoracotomy approach, a mean of 3.4 +/- 1.4 episodes of ventricular fibrillation were induced with an overall ischemic time of 87 +/- 54 seconds. At the end of DFT testing, patients with a left ventricular ejection fraction (EF) of < 30% had significant impairment of cardiac index (1.6 +/- 0.5 L/min/m2 after testing vs 2.2 +/- 0.6 L/min/m2 before the procedure). One patient with severely comprised ventricular function needed prolonged positive inotropic support. The left ventricular function of patients with a preoperative EF > or = 30%, however, was not changed (2.2 +/- 0.5 L/min/m2 after testing and 2.2 +/- 0.5 L/min/m2 before testing). The two groups did not differ with respect to the number of testing episodes, ischemic time, or DFT. Thus patients with a low preoperative EF (< 30%) are threatened by a severe left ventricular deterioration during ICD implantation. Close hemodynamic monitoring with a balloon-tipped catheter is recommended in these patients.

Cardiac Pacing, Artificial↗
PubMed1994

One-incision approach for insertion of implantable cardioverter defibrillators.

The placement of a transvenous implantable cardioverter defibrillator (ICD) system through a single infraclavicular skin incision has been a surgical goal for years. The development of a new investigational model of ICD with substantially reduced dimensions (volume, 83 cm3; mass, 132 g) has made the one-incision approach a clinical reality. Between March and September 1993, 4 female and 19 male patients (mean age, 60 +/- 9.6 years; range, 46 to 73 years) underwent implantation of this device for the treatment of ventricular fibrillation (n = 14) or ventricular tachycardia (n = 9). One transvenous lead was placed in the right ventricular apex and another in the left subclavian vein. A subpectoral pocket was formed in the infraclavicular area from the same incision to house the ICD generator and, if necessary, the subcutaneous patch. The mean operation time (81.5 +/- 32.7 minutes; range, 54 to 195 minutes) was significantly shorter than that noted for a previous series made up of patients undergoing traditional transvenous ICD implantations. In 20 patients (87%), endovenous defibrillation without a subcutaneous patch successfully caused externally induced ventricular fibrillation to revert with a mean minimum energy output of 21.9 +/- 3.5 J (range, 12 to 24 J). Endovenous defibrillation was more successful when biphasic (n = 16/17 [94%]) shocks rather than monophasic shocks (n = 4/6 [67%]) were used. No mortality, morbidity, or surgical complications were observed. These results indicate that the one-incision approach and the small size of the ICD generator can substantially facilitate ICD implantation and result in a reduction in the surgical trauma, the operation time, and the amount of material implanted.

Aged↗
PubMed1994

Biological effects of shock waves: induction of arrhythmia in piglet hearts.

During lithotripsy by electrohydraulic or electromagnetic lithotripters, the application of extracorporeal shock waves has to be synchronized with the electrocardiogram to reduce the induction of arrhythmias. The relation between the refractory period of the cardiac cycle and arrhythmia induction by shock waves, and the underlying mechanism have so far not been examined. In this experiment, the cardiac response to shock waves administered at 20 kV by an electrohydraulic lithotripter was assessed in nine piglets. The focus was positioned 5, 10 and 15 cm caudal to the apex of the left ventricle, and in some piglets also at the apex. The interval following the R-wave was determined during which the heart was refractory to shock wave stimulation by either single discharges or shock-wave bursts, i.e., groups of discharges separated by 10 ms intervals. This mechanical refractory period was compared to its electrical counterpart, which was determined by transvenous intracardiac atrial stimulation. As a result, mechanical refractory periods following the R-wave were at 5 cm distance 60 ms for single discharges and 70 ms for bursts (medians; range 10-180 ms); both stimulation modes were highly correlated (r = 0.88). While a similar result was obtained with the focus positioned directly at the cardiac apex, at 10 cm distance from it, bursts elicited a cardiac response significantly more often (in nine vs. two piglets). At 15 cm distance, no response was obtained at all. Both mechanical and electrical atrial refractory periods were in a similar range.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1994

[Anterior ST segment depression in acute inferior myocardial infarct: significance of its reproducibility during early ergometric test].

The significance of anterior ST segment depression (V1-V4) at the time of acute inferior myocardial infarction and exercise-induced anterior ST segment depression were studied in 30 patients. All patients carried out: two-dimensional echocardiography in the acute phase of myocardial infarction (Echo 1) and at predischarge (Echo 2); symptom-limited exercise test; coronary arteriography. According to ST segment changes, patients were divided into Group A (n = 15) with exercise-induced anterior ST segment depression and Group B (n = 15) with no ST segment depression during exercise. Group A showed a lower work physical capacity than Group B (6.8 +/- 3 METS and 9 +/- 2 METS, respectively). The wall motion index in Group A was 0.26 +/- 0.14 in the Echo 1 and 0.22 +/- 0.18 in the Echo 2 showing an improvement in wall motion abnormality; in Group B the same index was 0.35 +/- 0.19 in the Echo 1 and 0.34 +/- 0.18 in the Echo 2. Group A patients had a higher prevalence of multivessel disease compared with Group B patients and the right coronary artery was always involved. In conclusion, in inferior myocardial infarction the anterior ST segment depression, both in the acute phase and during the predischarge exercise test, reflects more extensive coronary disease and jeopardized myocardium.

Adult↗
PubMed1994

[Inadequate therapeutic effects of implantable cardioverter/defibrillators: etiology, therapy and prevention].

With the increasing number of implantable cardioverter-defibrillator (ICD) implantations in patients with sustained ventricular tachyarrhythmias, there is a growing interest in typical complications associated with this therapy. We analyzed the reasons and the incidence of inadequate therapy deliveries in 100 patients with epicardial (n = 27) or transvenous (n = 73) ICDs during a follow-up period of 10 +/- 8 months. A total of 21 of 100 patients received inadequate therapies. The most common reason was sinus tachycardia in eleven patients. Additional unnecessary shocks were avoided by reprogramming and application of beta-blockers. Lead failures caused the erroneous detection and defibrillation of ventricular fibrillation without any preceding clinical symptoms in four patients with an epicardial and in one patient with a transvenous ICD. All patients underwent successful surgical revision of their system. Atrial fibrillation with rapid ventricular response triggered inadequate shocks in four patients. Following digoxin administration no patient had additional inadequate shocks. In one patient non-sustained tachycardias caused unnecessary defibrillations. These results demonstrate that inadequate defibrillations are a common complication in patients after ICD-placement. The performance of x-ray, stress testing, and Holter monitoring on a regular basis may facilitate early diagnosis of possible reasons for unnecessary therapy deliveries. The improvement of detection and memory functions in future ICD-generations appears to be mandatory as well.

Adolescent↗
PubMed1993

Left ventricular filling rate at rest and during exercise in patients with previous myocardial infarction.

The purpose of this investigation was to define, with radionuclide technique, the variation on left ventricular filling rate in patients with coronary artery disease, and to determine the effects of dynamic exercise on this variation. The study was carried out on 91 subjects, 46 patients with anterior and 30 with inferior previous transmural myocardial infarction; 15 healthy subjects were studied as control group. All the patients underwent coronary angiography and left ventriculography. From the left ventricular time activity curve we considered the diastolic parameters of the peak filling rate (PFR). We considered also the relative end-diastolic volume (rEDV) and the relative end-systolic volume (rESV). These parameters were determined at rest and at the fifth minute of a symptom limited dynamic exercise taken in the supine position, on an ergometric bicycle. In normal subjects rest mean PFR values is 3.08 +/- 0.51 edv/s, during exercise occurs a physiological increase and mean PFR values becomes 5.48 +/- 1 edv/s. The patients with previous myocardial infarction show a PFR significantly smaller than in normal subjects. Abnormal PFR indices during exercise are present in a large number of these patients and the higher anomalies of PFR during exercise were found among patients with anterior myocardial infarction. In these patients we found an increase of rESV during exercise. In conclusion myocardial infarction induces significant alterations of the PFR; physical exercise reveals PFR alterations not exhibited at rest and rESV increase during exercise could be responsible for the PFR alteration observed.

Adult↗