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Featured researches published by G. Schreier.


Pacing and Clinical Electrophysiology | 1998

Intramyocardial Electrogram Variability in the Monitoring of Graft Rejection After Heart Transplantation

Barbara Grasser; F. Iberer; G. Schreier; S. Schaffellner; P. Kastner; G. Prenner; Günther Hipmair; A. Wasler; Berthold Petutschnigg; H. Müller; H. Hutten; Max Schaldach; Karlheinz Tscheliessnigg

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.


Journal of Heart and Lung Transplantation | 1999

Non-invasive cardiac allograft monitoring: the Graz experience

Barbara Grasser; F. Iberer; G. Schreier; S. Schaffellner; Reinhold Kleinert; G. Prenner; P. Kastner; H. Hutten; Karlheinz Tscheliessnigg

Based on previous reports by our group, initial studies on non-invasive cardiac graft monitoring have been presented recently. In this study we define new parameters to monitor rejection and infection after heart transplantation (HTX) the ventricular evoked response (VER) T-slew rate parameter is defined as the maximum negative slope in the descending part of the repolarization phase of the VER. We calculated the VER duration parameter in milliseconds and defined it as the time between the pacemaker spike and the cross-over of the baseline, with the slope line used to calculate the VER T-slew rate. During the HTX procedure, we implant wide-band telemetric pacemakers and fractally coated, epimyocardial electrodes (Physios CTM 01 and ELC 54-UP, Biotronik; Berlin, Germany). During each follow-up and on biopsy days, intramyocardial electrogram sequences were obtained and sent via the Internet to the central data-processing unit in Graz. We scored the infection status of the patients before data acquisition. The VER parameters were automatically calculated and send back within a few minutes. We prospectivly compared 1,613 follow-ups from 42 patients with biopsy (International Society of Heart and Lung Transplantation grading) and infection classification. The VER duration parameter did not change during rejection; however, we found an increase during clinically apparent infection. The VER T-slew rate parameter was lower during rejection grade 2 or higher, as well as during clinically apparent infection. The negative predictive value to rule out rejection was 99%. Our results indicate that rejection and infection cause different, reproducible effects on the electrical activity of the transplanted heart. Non-invasive cardiac graft monitoring may reduce the need for surveillance biopsies and may offer a tool to optimize immunosuppressive therapy after HTX.


Transplant International | 1996

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

F. Iberer; Karlheinz Tscheliessnigg; Gabriele Halwachs; Peter Rehak; A. Wasler; Berthold Petutschnigg; G. Schreier; H. Müller; Thomas Allmayer; Martina Freigassner; G. Prenner; Günther Hipmair; Barbara Grasser

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.


Transplant International | 2000

Non-invasive graft monitoring after heart transplantation: rationale to reduce the number of endomyocardial biopsies.

Barbara Grasser; F. Iberer; S. Schaffellner; Daniela Kniepeiss; G. Schreier; P. Kastner; Karlheinz Tscheliessnigg

Abstract The endomyocardial biopsy is invasive, reduces quality of life and cannot be repeated daily. Initial studies on noninvasive cardiac graft monitoring have been presented recently. During the heart transplant procedure, we implanted wideband telemetric pacemakers and fractally coated, epimyocardial electrodes. On biopsy days and during each follow‐up, intramyocardial electrogram sequences were obtained. The maximum T‐slew rate from the ventricular evoked response (VER) was automatically calculated and compared to the biopsy results (n = 331, ISHLT grading). The VER T‐slew rate was significantly lower during rejection grade 2 or higher. The negative predictive value to exclude rejection was 98%. Using a single threshold diagnosis model, 74% of the biopsies could have been avoided. Noninvasive cardiac graft monitoring can reduce the need for surveillance biopsies and may offer a tool to optimize immunosuppressive therapy after heart transplantation


international conference of the ieee engineering in medicine and biology society | 1998

Hemodynamic assessment by evaluation of intramyocardial electrograms

H. Hutten; P. Kastner; G. Schreier; M. Schaldach

The influence of hemodynamic variation on intramyocardial electrograms was investigated by combining clinical intramyocardial electrogram recordings with computerized modeling of the heart. Paced intramyocardial electrograms were recorded in heart transplant patients using telemetric pacemakers. Different hemodynamic filling states of the heart have been achieved by variation of the pacing rate. The results of the regression analysis between the pacing rate and parameters of the depolarization phase were used to set the parameters of the computer model that allows to simulate the origination of the ventricular evoked response and to consider influences of geometric variation. The experimental and theoretical results show a distinct and comparable impact of the hemodynamic state of the heart on the depolarization phase of paced intramyocardial electrograms.


international conference of the ieee engineering in medicine and biology society | 1999

Correlation between paced epimyocardial electrograms and stroke volume in heart transplants

P. Kastner; G. Schreier; S. Schaffellner; B. Grasser; F. Iberer; K.H. Tscheliessnigg; M. Schaldach; H. Hutten

In 10 heart transplant patients different hemodynamic states have been forced by randomized changes of pacing rate (PR) and postural variations (overall 40, 4/spl plusmn/1 per patient). Cardiac output assessed with thermodilution technique was compared to the ventricular evoked response (VER) recorded with telemetric pacemakers from epimyocardial leads. Linear regression analysis between the negative extremum during the depolarization phase of the VER (R/sub amp/) and the stroke volume (SV=CO/PR) resulted in the equation: R/sub amp/[%]=140-0.4*SV[%] with r=0.89 and p<0.00001. This result confirms previously reported results of a distinct relation between the negative extremum of paced epimyocardial ECGs and geometrical variations of the heart.


Transplant International | 1998

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

Barbara Grasser; F. Iberer; G. Schreier; A. Allmayer; S. Schaffellner; G. Prenner; A. Wasler; Berthold Petutschnigg; H. Müller; Karlheinz Tscheliessnigg

Abstract 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.


international conference of the ieee engineering in medicine and biology society | 1997

The influence of infectious disease on ventricular evoked responses from heart transplants

G. Schreier; P. Kastner; H. Hutten; M. Schaldach; B. Grasser; S. Schaffellner; G. Prenner; F. Iberer; K.H. Tscheliessnigg

Telemetric recording and subsequent analysis of intramyocardial electrograms offer a noninvasive method for patient monitoring after heart transplantation. Decreasing electrical activity indicates both episodes of rejection and infection. Analysis of the duration of the ventricular evoked response recorded during pacing reveals a significant increase of this parameter only during infection. In many cases, this additional information can be used to differentiate between the two pathological effects and to enhance the specificity of the method.


international conference of the ieee engineering in medicine and biology society | 1996

Intramyocardial electrograms from spontaneous and paced heart beats, telemetrically recorded from different right ventricular positions

G. Schreier; P. Kastner; H. Hutten; M. Schaldach; B. Grasser; G. Prenner; F. Iberer; K.H. Tscheliessnigg

Intramyocardial electrograms from the spontaneously beating and the paced heart were recorded in 8 heart transplants for rejection monitoring, using telemetric dual chamber pacemakers and two epimyocardial leads, located at two different right ventricular positions. Linear regression analysis of the rejection sensitive parameters showed that the correlation between the two electrodes was significantly higher for the paced than for the spontaneous heart beats.


international conference of the ieee engineering in medicine and biology society | 1998

Correlation between amplitude and RR interval of premature QRS complexes from intramyocardial electrograms

I. Hutten; G. Schreier; P. Kastner; M. Schaldach; B. Grasser; F. Iberer; K.H. Tscheliessnigg

Intramyocardial electrograms have been recorded noninvasively via telemetric pacemakers from spontaneously beating heart transplants. The amplitudes of premature QRS complexes have been compared to those of normal QRS complexes. Linear regression analysis revealed increased amplitudes, which are assumed to be due to the reduced filling pattern of the premature beats. Hence, intramyocardial electrograms contain haemodynamic information.

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F. Iberer

Medical University of Graz

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S. Schaffellner

Medical University of Graz

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