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Biomedical subjects

F Iberer

Publications and source records attributed to F Iberer.

At least 37 records · Page 2Linked to original sources
PubMed1998

Intramyocardial electrograms for non-invasive rejection monitoring: initial experience with an infection-specific parameter.

Non-invasive rejection monitoring based on the analysis of paced intramyocardial electrograms enables repeated or even daily graft surveillance. The rejection-sensitive parameter is calculated from the maximum slope of the descending part of the t wave. Biopsy-proven rejection grade 2 or higher (ISHLT classification) can safely be detected. Nevertheless, infection influences the rejection-sensitive parameter in the same manner as does rejection (99% negative predictive value for rejection grade 2 or higher, 17% positive predictive value). We defined the infection-specific parameter as the time on the O line between the pacemaker stimulus and the crossover with the maximum slope of the descending part of the t wave. Patients were classified prospectively according to infection status: patients without infection and those with clinically apparent infection. Patients with clinically apparent infections had a significantly longer infection-specific parameter. A simultaneous decrease of the rejection-sensitive parameter and an increase in the infection-specific parameter was observed during clinical infection: a decrease in the rejection-sensitive parameter and no changes in the infection-specific parameter were observed during rejection. This preliminary analysis revealed that discrimination of rejection and infection might be possible by the analysis of intramyocardial electrograms.

Diagnosis, Differential↗
PubMed1998

Intramyocardial electrogram variability in the monitoring of graft rejection after heart transplantation.

The ventricular evoked response is a well-standardized electrophysiological signal that can be used for noninvasive, long-term cardiac transplant monitoring. Rejection-sensitive and infection-specific parameters extracted from intramyocardial electrograms correlate with clinical results. The influences of pacing rate, transition from intrinsic to paced rhythm and positional changes on the diagnostic parameters were studied. Increasing the pacing rate shortened the ventricular evoked response and directly influenced the infection specific parameter. The rejection-sensitive parameter remained stable at pacing rates between 100 and 120 beats/min. Measurements made immediately after the patient assumed a supine position and after switching to paced rhythm showed a decrease in the rejection-sensitive parameter. A change in position from supine to upright did not influence the rejection-sensitive parameter, but higher values were measured after returning to the supine position. In conclusion, noninvasive recordings of the ventricular evoked response for monitoring of cardiac allograft should be done at the same time of day, at the same pacing rate, and with the patient resting for at least 5 minutes before measurements are made.

Adolescent↗
PubMed1997

Rapid, sensitive high-performance liquid chromatographic method for the determination of cyclosporin A and its metabolites M1, M17 and M21.

Cyclosporin A (CyA) and its metabolites seem to have nephro-, hepato- and neurotoxic side effects. Immunosuppressive therapy is a narrow path between the risk of rejection by underimmunosuppression and toxic organ damage by overdosage. Thus CyA dosage must be calculated to avoid the risks of organ rejection through underdosage and toxic organ damage through overdosage or accumulation of metabolites. In routine monitoring of CyA therapy, it can be important to measure not only the parent drug but also the metabolites. We describe a rapid and isocratic high-performance liquid chromatographic method for measurement of CyA and its metabolites M1, M17 and M21 in whole blood. CyA was detected by ultraviolet absorption at 212 nm with a CN analytical column maintained at 50 degrees C and recycling of hexane-isopropanol as mobile phase for improved long-term column stability and efficiency. The minimum detectable concentration of CyA and the three metabolites was 10 ng/ml blood. Our modified HPLC method for the determination of CyA and its metabolites is a simple (isocratic), rapid (the retention times were 7.1 min for CYD, internal standard, 8.9 min for CyA, 11.0 min for M21, 12.9 min for M17 and 16.3 min for M1) and economical method suitable for measuring the concentration of the major metabolite, M17, and for routine monitoring of CyA-treated patients.

Chromatography, High Pressure Liquid↗
PubMed1996

Evoked epimyocardial electrogram for rejection diagnosis after heart transplantation.

An endomyocardial electrogram (ECG) was reported to be a sensitive and practicable method for rejection monitoring after heart transplantation. Long-term follow up was limited, however, by variations of signals. The repolarization part of ECG signals vary with changes of heart rate. Both can be avoided by using pacemaker-induced signals. For stimulation and sensing of the ventricular-evoked response, a new type of electrode with fractal surface structure was used. Twenty patients undergoing heart transplantation were evaluated. Amplitudes of the depolarization and repolarization part of the ventricular-evoked response signals were analyzed and related to the degree of acute rejection according to histological findings from endomyocardial biopsy. Signals were transferred by Internet and analyzed automatically. In the case of focal moderate rejection (grade 2, International Society for Heart Transplantation grading) and higher degrees of rejection, a significant amplitude decrease was found. This sensitive non-invasive method for rejection monitoring with a high level of reliability provides the possibility of reducing the number of endomyocardial biopsies.

Adult↗
PubMed1996

Donor heart quality control. Analysis of echocardiographic (EC) findings and patient outcome.

In a retrospective analysis, 149 echocardiographic (EC) evaluations were compared with conventional clinical parameters for donor heart selection. Of these cases, 12% were found with severe impairment of ventricular wall motion or with morphological abnormalities. Nearly half of the echocardiographically diagnosed pathological findings in donor hearts were not detected by conventional standards for heart screening. Analysis of EC-screened donor heart outcome showed a primary graft nonfunction rate of 3.1%. We suggest EC as an additional screening instrument for further dynamic and morphological information about donor heart condition. Potential donors can be saved for transplantation and severe complications can be avoided by detecting occult cardiac dysfunction. Early detection of cardiac dysfunction may have an impact on donor therapy and can avoid unnecessary and expensive transportation of the surgical team to the harvest site.

Adolescent↗
PubMed1996

Definitions of cytomegalovirus disease after heart transplantation: antigenemia as a marker for antiviral therapy.

In this prospective study, cytomegalovirus (CMV) antigenemia was defined as the marker for initiation and episodes of antigenemia as the indicator for the duration of antiviral therapy (CMV hyperimmune globulin and ganciclovir). The CMV antigenemia assay and CMV-specific IgM and IgG antibody tests were used to monitor CMV infection in 22 heart transplant recipients who, between October 1992 and July 1994, were followed up for 6 months. A total of 178 out of 627 antigenemia assays tested positive. The highest number of positive cells was greater after primary infection than after either reactivation (43.3 vs 0.3; P < 0.01) or reinfection (43.3 vs 9.3; P = NS). Sixty episodes of antigenemia were observed. More episodes of antigenemia were seen after primary infection than after either reactivation (4.6 vs 0.2; P < 0.01) or reinfection (4.6 vs 2.2; P = NS). The detection of antigenemia indicated the initiation of antiviral therapy within 24 h after the blood sample was harvested. Therapy was stopped immediately after a subsequent negative result became available. Our experience indicates that antigenemia directed antiviral therapy prevents CMV disease after primary and secondary infection in heart transplant recipients.

Adolescent↗
PubMed1996

[Cardiac pacemaker as bridge to cardiac telemonitoring].

Modern pacemakers and electrodes are equipped with supplementary features that can be utilized for many problems related to cardiac diagnosis and therapy management. Especially the recording and computer-assisted analysis of intramyocardial electrograms (IEGM), particularly of ventricular evoked responses (VER), supplies important information. The IEGMs are transmitted with large bandwidth from the implanted pacemaker to an extracorporeal receiver and from there via Internet to a central data processing station, where a specially designed software for IEGM processing is available. An individual password secured account is installed for each user. After signal processing is completed, a comprehensive patient report including trend courses and relevant clinical data is provided and can be utilized by the user for further decisions. Using this basic structure, CHARM (Computerized Heart Acute Rejection Monitoring), a system for non-invasive rejection monitoring after heart transplantation, has been developed and successfully evaluated in a clinical environment.

Computer Systems↗
PubMed1996

Troponin T as a marker for posttransplantation adaptational problems of the donor heart.

BACKGROUND: Troponin T is used as a marker for myocardial cell damage (e.g., in aiding diagnosis and follow-up of myocardial infarction). Elevated troponin T levels are also observed after heart transplantation, although until now no explanation could be found for this phenomenon. METHODS AND RESULTS: Serum samples of 15 patients who underwent orthotopic heart transplantation were tested for troponin T with a one-step enzyme immunoassay. The highest concentrations of troponin T were seen between day 3 and 14 after transplantation (3.05 +/- 1.30 micrograms/L) and remained elevated up to 3 months. A correlation (r = 0.61, p < 0.02) was found between pretransplantation systolic pulmonary artery pressure and the cumulative troponin T release after transplantation. No association was found with rejection, and no correlation was found with ischemic time of the donor heart. CONDITIONS: These findings support the hypothesis that the acute exposure of the donor heart to the preexisting elevated right ventricular afterload in the recipient represents a strong mechanical stress for the transplanted heart. Measurement of troponin T may therefore be helpful in the posttransplantation monitoring and management of ventricular function after orthotopic heart transplantation.

Adaptation, Physiological↗
PubMed1996

Paced epimyocardial electrograms for noninvasive rejection monitoring after heart transplantation.

BACKGROUND: Diagnosis of acute heart rejection after transplantation with the help of epimyocardial electrograms has been reported as a sensitive and practicable method. Long-term follow-up has been limited, however, by variations o signal, which can be avoided by using pacemaker-induced signals. METHODS: For stimulation and detection of the ventricular evoked response, a new type of electrode with fractal surface structure was used. Seventeen patients undergoing heart transplantation were included in the study. Amplitudes of the depolarization and repolarization parts of ventricular evoked response signals were analyzed and related to the degree of acute rejection according to histologic findings from endomyocardial biopsy. RESULTS: In cases of focal moderate rejection (grade 2, International Society for Heart and Lung Transplantation grading) and higher degrees of rejection, significant amplitude decreases were found. CONCLUSION: This sensitive noninvasive method for rejection monitoring with a high level of reliability provides the possibility of reducing the number of endomyocardial biopsies.

Biopsy↗