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Electrophysiologic Changes (electrophysiologic + change)

Distribution by Scientific Domains
Medical Sciences75%

Selected Abstracts

Effect of Gender on Atrial Electrophysiologic Changes Induced by Rapid Atrial Pacing and Elevation of Atrial Pressure

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2001
HUNG-FAT TSE M.D.
Atrial Electrical Remodeling.Introduction: The incidence of atrial fibrillation is greater in men than in women, but the reasons for this gender difference are unclear. The purpose of this study was to evaluate the effects of gender on the atrial electrophysiologic effects of rapid atrial pacing and an increase in atrial pressure. Methods and Results: Right atrial pressure and effective refractory period (ERP) were measured during sinus rhythm and during atrial and simultaneous AV pacing at a cycle length of 300 msec in 10 premenopausal women, 11 postmenopausal women, and 24 men. The postmenopausal women were significantly older than the premenopausal women (61 ± 8 years vs 34 ± 10 years; P < 0.01). During sinus rhythm, mean atrial ERP in premenopausal women was shorter (211 ± 19 msec) than in postmenopausal women and age-matched men (242 ± 18 msec and 246 ± 34 msec, respectively; P < 0.05). Atrial ERPs in all patients shortened significantly during atrial and simultaneous AV pacing. However, the degree of shortening during atrial pacing (43 ± 8 msec vs 70 ± 20 msec and 74 ± 21 msec; P < 0.05) and during simultaneous AV pacing (48 ± 16 msec vs 91 ± 27 msec and 84 ± 26 msec; P < 0.05) was significantly less in premenopausal women than in postmenopausal women or age-matched men. Conclusion: The results of this study demonstrate a significant gender difference in atrial electrophysiologic changes in response to rapid atrial pacing and an increase in atrial pressure. The effect of menopause on the observed changes suggests that the gender differences may be mediated by the effects of estrogen on atrial electrophysiologic properties. [source]

Spinal somatosensory evoked potential evaluation of acute nerve-root injury associated with pedicle-screw placement procedures: An experimental study

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2003
I-Ming Jou
Pedicle screws for spinal fixation risk neural damage because of the proximity between screw and nerve root. We assessed whether spinal somatosensory evoked potential (SSEP) could selectively detect pedicle-screw-related acute isolated nerve injury. Because pedicle screws are too large for a rat's spine, we inserted a K-wire close to the pedicle in 32 rats, intending not to injure the nerve root in eight (controls), and to injure the L4 or L5 root in 24. We used sciatic-nerve-elicited SSEP pre- and postinsertion. Radiologic, histologic, and postmortem observations confirmed the level and degree of root injury. Sciatic (SFI), tibial (TFI), and peroneal function indices (PFI) were calculated and correlated with changes in potential. Although not specific for injuries to different roots, amplitude reduction immediately postinsertion was significant in the experimental groups. Animals with the offending wire left in place for one hour showed a further non-significant deterioration of amplitude. Electrophysiologic changes correlated with SFI and histologic findings in all groups. SSEP monitoring provided reliable, useful diagnostic and intraoperative information about the functional integrity of single nerve-root injury. These findings are clinically relevant to acute nerve-root injury and pedicle-screw insertion. If a nerve-root irritant remains in place, a considerable neurologic deficit will occur. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source]

Effect of Gender on Atrial Electrophysiologic Changes Induced by Rapid Atrial Pacing and Elevation of Atrial Pressure

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2001
HUNG-FAT TSE M.D.
Atrial Electrical Remodeling.Introduction: The incidence of atrial fibrillation is greater in men than in women, but the reasons for this gender difference are unclear. The purpose of this study was to evaluate the effects of gender on the atrial electrophysiologic effects of rapid atrial pacing and an increase in atrial pressure. Methods and Results: Right atrial pressure and effective refractory period (ERP) were measured during sinus rhythm and during atrial and simultaneous AV pacing at a cycle length of 300 msec in 10 premenopausal women, 11 postmenopausal women, and 24 men. The postmenopausal women were significantly older than the premenopausal women (61 ± 8 years vs 34 ± 10 years; P < 0.01). During sinus rhythm, mean atrial ERP in premenopausal women was shorter (211 ± 19 msec) than in postmenopausal women and age-matched men (242 ± 18 msec and 246 ± 34 msec, respectively; P < 0.05). Atrial ERPs in all patients shortened significantly during atrial and simultaneous AV pacing. However, the degree of shortening during atrial pacing (43 ± 8 msec vs 70 ± 20 msec and 74 ± 21 msec; P < 0.05) and during simultaneous AV pacing (48 ± 16 msec vs 91 ± 27 msec and 84 ± 26 msec; P < 0.05) was significantly less in premenopausal women than in postmenopausal women or age-matched men. Conclusion: The results of this study demonstrate a significant gender difference in atrial electrophysiologic changes in response to rapid atrial pacing and an increase in atrial pressure. The effect of menopause on the observed changes suggests that the gender differences may be mediated by the effects of estrogen on atrial electrophysiologic properties. [source]

Differences in the morphology and duration between premature P waves and the preceding sinus complexes in patients with a history of paroxysmal atrial fibrillation

CLINICAL CARDIOLOGY, Issue 7 2003
Polychronis E. Dilaveris M.D.
Abstract Background: Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. Experimental and human mapping studies have demonstrated that perpetuation of AF is due to the presence of multiple reentrant wavelets with various sizes in the right and left atria. Hypothesis: Atrial fibrillation may be induced by atrial ectopic beats originating in the pulmonary veins, and premature P-wave (PPW) patterns may help to identify the source of firing. Methods: To evaluate the morphology and duration of PPWs, 12-lead digital electrocardiogram (ECG) strips containing clearly definable PPWs not merging with the preceding T waves were obtained in 25 patients with AF history (9 men, mean age 59.5 ± 2.2 years) and 25 subjects without any previous AF history (11 men, mean age 53.6 ± 2.5 years). The polarity of PPWs was evaluated in all 12 ECG leads. Previously described indices, such as P maximum, P dispersion (= P maximum ,P minimum), P mean, and P standard deviation were also calculated. Results: Premature P-wave patterns were characterized by more positive P waves in lead V1. All P-wave analysis indices were significantly higher in patients with AF than in controls when calculated in the sinus beat, whereas they did not differ between the two groups when calculated in the PPW. P-wave indices did not differ between the PPW and the sinus P wave in either patients with AF or controls, except for P mean, which was significantly higher in the sinus (110.1 ± 1.7 ms) than in the PPW (100 ± 2 ms) only in patients with AF (p = 0.001). Conclusion: The evaluation of PPW patterns is only feasible in a small percentage of short-lasting digital 12-lead ECG recordings containing ectopic atrial beats. Premature P wave patterns are characterized by more positive P waves in lead V1, which indicates a left atrial origin in the ectopic foci. The observed differences in P-wave analysis indices between patients with AF and controls and between sinus beats and PPWs may be attributed to the presence of electrophysiologic changes in the atrial substrate. [source]