Biomedical subjects

Thomas Berger

Publications and source records attributed to Thomas Berger.

60 records · Page 4Linked to original sources

PubMed2002

Global P wave duration on the 65-lead ECG: single-site and dual-site pacing in the structurally normal human atrium.

INTRODUCTION: Pacing is believed to prevent atrial fibrillation by reducing atrial activation time. Exact correlation between P wave duration (PWD) on surface ECG and endocardial atrial activation time is still unexplored. METHODS AND RESULTS: In 15 patients without structural heart disease (9 women, age 45 +/- 14 years), single site [high right atrium (HRA), coronary sinus ostium (CSos), distal CS (CSd), high RA septum (Bachmann's bundle, BB)] and dual-site pacing (various combinations) was performed after ablation of supraventricular tachycardia. A 65-lead surface ECG was recorded simultaneously. Endocardial atrial activation time was measured off-line (stimulus - last bipolar recording), and the respective PWD was assessed using the root mean square and 65-channel summary plots. PWD during pacing from BB was significantly shorter (96 +/- 12 msec) than during HRA (121 +/- 15 msec), CSos (108 +/- 9 msec), and CSd pacing (126 +/- 14 msec; P < 0,01, respectively). PWD during dual-site pacing (HRA+BB, 91 +/- 14 msec; HRA+CSos, 96 +/- 7 msec; HRA+CSd, 90 +/- 7 msec; BB+CSd, 96 +/- 12 msec) was not significantly shorter than during pacing from BB. Correlation between endocardial atrial activation time and PWD was 0.83. CONCLUSION: PWD during single-site and dual-site atrial pacing represents endocardial atrial activation time and can be measured precisely using the 65-lead surface ECG. The fact that high septal pacing results in the shortest PWD may have implications for preventive pacing in patients with atrial fibrillation.

Adult↗

PubMed2002

Clinical ECG mapping and imaging of cardiac electrical excitation.

Combining electrocardiographic mapping and 3D+time anatomical data enables noninvasively the imaging of the electrical excitation sequence in the human heart. A bidomain-theory based surface heart model activation time imaging approach was employed to image single beat data of atrial and ventricular depolarisation. Activation time maps were reconstructed for three patients who underwent an electrophysiologic study. The sinus rhythm and a rhythm according to a pacing protocol were reconstructed for two patients. For the third patient the accessory pathway of the WPW syndrome was localized. For focal arrhythmias, this model-based imaging approach might allow the guidance and evaluation of antiarrhythmic interventions, for instance, in case of catheter ablation or drug therapy.

Adult↗

PubMed2002

Model-based imaging of cardiac electrical excitation in humans.

Activation time (AT) imaging from electrocardiographic (ECG) mapping data has been developing for several years. By coupling ECG mapping and three-dimensional (3-D) + time anatomical data, the electrical excitation sequence can be imaged completely noninvasively in the human heart. In this paper, a bidomain theory-based surface heart model AT imaging approach was applied to single-beat data of atrial and ventricular depolarization in two patients with structurally normal hearts. In both patients, the AT map was reconstructed from sinus and paced rhythm data. Pacing sites were the apex of the right ventricle and the coronary sinus (CS) ostium. For CS pacing, the reconstructed AT pattern on the endocardium of the right atrium was compared with the CARTO map in both patients. The localization errors of the origins of the initial endocardial breakthroughs were determined to be 6 and 12 mm. The sites of early activation and the areas with late activation were estimated with sufficient accuracy. The reconstructed sinus rhythm sequence was in good qualitative agreement with the pattern previously published for the isolated Langendorff-perfused human heart.

Adult↗

PubMed1992

Sodium and Calcium Currents in Glial Cells of the Mouse Corpus Callosum Slice.

We studied Na+ and Ca2+ currents in glial cells during the development of the corpus callosum in situ. Glioblasts and oligodendrocytes from frontal brain slices of postnatal day (P) 3 to P18 mice were identified based on morphological and ultrastructural features after characterization of the currents with the patch-clamp technique. Slices from P3 - P8 mice contained predominantly glioblasts with immature morphological features. These cells showed Na+ and Ca2+ currents, but the population with these currents decreased between P3 and P8. Na+ currents were blocked in Na+-free bathing solution and in the presence of tetrodotoxin, Ca2+ currents were only observed when a high concentration of extracellular Ba2+ was present. The cells from the corpus callosum of P10 - P18 mice predominantly had morphological features of oligodendrocytes. In these cells, which in some cases were shown to form myelin, neither Na+ nor Ca2+ currents were detected. To compare these in situ results with those from the electrophysiologically and immunocytochemically well-characterized cultured glial cells, we determined the expression pattern of stage-specific antigens in the corpus callosum in situ. The first O4 antigen-positive glial precursors were observed at P1, the earliest stage examined. The oligodendrocytic antigens O7 and O10 appeared at P6 and P14, respectively, and prominent labelling with the corresponding markers was seen at P12 and P18, respectively. Despite the existence of numerous mature, O10-positive oligodendrocytes at P18, which expressed Ca2+ channels in vitro, we failed to detect Ca2+ currents in situ at this stage.

Journal Article↗

PubMedDate not supplied

Is there a causal link between maltreatment and adolescent pregnancy? A literature review.

CONTEXT: Despite a sizable amount of research addressing the relationship between violence and women's reproductive health, it has not been shown whether there is sufficient evidence of a causal link between childhood maltreatment and subsequent adolescent pregnancy. METHODS: Three databases (Medline, PsychiNFO and SocioFile) were searched for studies published between 1980 and 2000 relating maltreatment and adolescent pregnancy. The review was limited to empirical studies; theoretical articles and those with no women who were aged 21 or younger during the research period or when they experienced maltreatment were excluded. RESULTS: Fifteen articles on the topic were found All were published after 1989; all but one were cross-sectional, were retrospective and relied on recall. All of the studies dealt with sexual maltreatment, either alone or in combination with other types of maltreatment; few covered emotional abuse or neglect. The studies lacked consistent definitions of the various types of maltreatment. Only one examined adolescent mothers' relationships with men, and none examined relationships with perpetrators. Few dealt with racial and ethnic differences related to violence. All lacked a specific theoretical approach. Ten of the studies supported a link between maltreatment and adolescent pregnancy, and five eitherdid not support a link or qualified the relationship. Substance abuse, poor mental health and promiscuity were among the mediating variables examined. CONCLUSIONS: Because recent studies have reached conflicting findings, had methodological weaknesses and lacked theoretical grounding, whether a causal link exists between maltreatment and adolescent pregnancy remains an unanswered question.

Adolescent↗

PubMedDate not supplied

Oxygen permeation and microbial ingress through a film-coated and uncoated elastomeric closure in A glass vial: a comparative study.

This is a comparative study of oxygen permeation and microbial ingress into a drug vial stopper that is an elastomeric pharmaceutical compound versus the same compound coated with a thin Teflon-type film coating. The objective of this study is to determine if the film coating causes any changes in the rate of oxygen permeation or microbial ingress into the vial from the environment. From the data obtained it is concluded that the film did not change either the oxygen or microbial ingress into the vial; therefore the stoppers are essentially equivalent with respect to these parameters.

Bacillus subtilis↗