Correlation between changes in stroke volume and the paced intracardiac electrogram.

AIM: The aim of this study was to examine the relation between cardiac haemodynamics and parameters extracted from the intracardiac electrogram obtained during pacing, i.e. ventricular evoked response. METHODS AND RESULTS: In the course of routinely scheduled right heart catheterization, intracardiac electrograms and cardiac haemodynamics were monitored simultaneously in ten heart transplant patients (two females, aged 48 +/- 12 (18-59) years), using pacemaker telemetry and Swan-Ganz thermodilution techniques. Different haemodynamic states were induced by pacemaker programming (pacing rate changes) and table tilting (postural changes). Forty different haemodynamic states were assessed, with an average of three (2.4) haemodynamic variations in each patient. Linear regression analysis between relative stroke volume changes and relative changes in the R wave slew rate as extracted from the evoked responses revealed a strong, inverse, and highly significant correlation (r= - 0.93, P<0.0001) between those parameters. Similar results were obtained for pacing rate and postural variations alone, respectively. CONCLUSIONS: The strong correlation between changes in stroke volume and R slew rate indicates that paced intracardiac electrograms reflect changes in the size and geometry of the heart. Telemetrically recorded intracardiac electrograms may thus be used non-invasively to assess key aspects of cardiac haemodynamics.

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

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.

Non-invasive cardiac allograft monitoring: the graz experience.

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.

Mild chronic anemia following heart transplantation: a syndrome with prognostic relevance?

The clinical relevance of mild chronic anemia in patients after heart transplantation (HTX) has not yet been demonstrated. Forty-five outpatients who had undergone HTX 2-99 months prior to investigation and who had not received blood transfusions or erythropoietin (EPO) before data acquisition were observed over a period of 37 months. Anemia was found in 36 of the 45 patients and was normocytic, normochromic, and slightly anisocytotic (coefficient of variation = 16 +/- 2, normal 11.5-14.5). Anemic patients showed elevated EPO levels, whereas in nonanemic patients EPO levels were normal. Survival after HTX differed significantly in anemic and nonanemic patients (P < 0.02), with 100% survival in the nonanemic and 85% in the anemic group. Chronic anemia in patients after HTX shows a typical pattern. Even when mild, anemia in patients after HTX seems to be of prognostic value and thus might be an indicator of chronic disorders.

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.

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.

[Cardiac pacemaker as bridge to cardiac telemonitoring]. / Der Herzschrittmacher als Brücke zum kardialen 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.