Home About us Contact
|
Home About us Contact | ||
|
|
||
Activation Patterns (activation + pattern)
Kinds of Activation Patterns Selected AbstractsVariability in Postpacing Intervals Predicts Global Ventricular Activation Pattern during TachycardiaPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2010ILYAS K. COLOMBOWALA M.D. Introduction: Assessment of ventricular activation pattern is critical to the successful ablation of ventricular tachycardia (VT). We have previously shown that the global atrial activation pattern during tachycardia can be rapidly and accurately assessed by calculating the postpacing interval variability (PPIV); PPIV was minimal in circuitous tachycardias and highly variable in centrifugal tachycardias. In the present study, we use the PPIV to determine the ventricular global activation pattern during VT. Methods: Patients with mappable VT were included. We defined global ventricular activation as either centrifugal (arising from a focus with radial expansion) or circuitous (gross macro-reentrant circuit), based on the findings of electroanatomic mapping. PPIV was calculated as the difference in postpacing interval with right ventricular apical overdrive pacing during tachycardia at cycle lengths (CL) 10 ms and 30-ms shorter than tachycardia, regardless of the origin of the tachycardia. We studied 20 patients with 23 VTs (11 centrifugal, mean CL 390 ± 36.1 ms; 12 circuitous, mean CL 418 ± 75.7 ms). Results: The mean PPIV was 45 ± 16 ms for patients with centrifugal VT and 6.7 ± 4.1 ms for patients with circuitous VT. Rank sum analysis of PPIV showed a significant difference between the two groups (P < 0.05). Conclusions: Our data suggest that the global ventricular activation pattern during VT can be rapidly and accurately defined by assessing the PPIV. This technique allows for a rapid confirmation of the tachycardia activation and significantly facilitates mapping and ablation. (PACE 2010; 33:129,134) [source] Laplacian Electrograms and the Interpretation of Complex Ventricular Activation Patterns During Ventricular FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000PH.D., RUBEN CORONEL M.D. Laplacian Electrograms and Ventricular Fihrillation. Introduction. During ventricular fibrillation (VF) interpretation of a local electrogram and determination of the local activation moment are hampered by remote activity or intervening repolarization waves. Successful defibrillation depends on critical timing of the shock relative to local activation. We tested the applicabillity of Laplacian electrograms for detection of the moment of local activation during VF. Methods and Results. From isolated perfased porcine infact heart, 247 local unipolar electrograms were recorded simultaneously (13 × 19 matrix, interelectrode distance 0.3 mm) from the left ventricular wall during sinus rhythm, following pacing or during VF, Activation maps were constructed based on local unipolar electrograms, and Laplacian electrograms were calculated from local electrograms ane its eight neighbors. The Laplacian electrogram displayed a sharp R/S complex with local activation iodicted by the moment of zero crossing without interference from remote activity or repolarization waves. Its amplitude increased with decreasing interelectrode distance, Following epicardial stimulation, Laplacian amplitude was significantly larger than during complexes with different morphology. Collision of wavefronts was associated with entirely positive Laplacian waveforms; "focal" appearancce of acitivity was associated with an entirely negative waveform. Activation block in the activation maps was correlated with the appearance of substanined episodes of negativity or positivity in the Laplacian electrogram (depending on the location of the recording site relative to the line of block). Conclusion. Laplacian electrograms allow detection of the moment of local activation without interference from remote activity or repolarization, especially during complex arrhythmias. The technique applied toe automatic sensing devices, such its the internal defibrillator, may optimize defibrtilation success. (J Cardiovasc Electrophysiol, Vol. 11, pp. 1119-1128, October 2000) [source] Identical Atrial Activation Patterns During Spontaneous Initiations of Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2000David S. Rosenbaum M.D. Section Editor [source] Mapping of Atrial Activation Patterns After Inducing Contiguous Radiofrequency Lesions: An Experimental StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2001FRANCISCO J. CHORRO CHORRO, F.J., et al.: Mapping of Atrial Activation Patterns After Inducing Contiguous Radiofrequency Lesions: An Experimental Study. High resolution mapping techniques are used to analyze the changes in atrial activation patterns produced by contiguous RF induced lesions. In 12 Langendorff-perfused rabbit hearts, left atrial activation maps were obtained before and after RF induction of epicardial lesions following a triple-phase sequential protocol: (phase 1) three separate lesions positioned vertically in the central zone of the left atrial wall; (phase 2) the addition of two lesions located between the central lesion and the upper and lower lesions; and (phase 3) the placement of four additional lesions between those induced in the previous phases. In six additional experiments a pathological analysis of the individual RF lesions was performed. In phase 1 (lesion diameter = 2.8 ± 0.2 mm, gap between lesions = 3 ± 0.8 mm), the activation process bordered the lesions line in two (2.0-ms cycles) and four experiments (1.0-ms cycles). In phase 2, activation bordered the lesions line in eight (2.0-ms cycles, P < 0.01 vs control) and nine experiments (1.0-ms cycles, P < 0.001), and in phase 3 this occurred in all experiments except one (both cycles, P < 0.001 vs control). In the experiments with conduction block, the increment of the interval between activation times proximal and distal to the lesions showed a significant correlation to the length of the lesions (r = 0.68, P < 0.05, 100-ms cycle). In two (17%) experiments, sustained regular tachycardias were induced with reentrant activation patterns around the lesions line. In conclusion, in this acute model, atrial RF lesions with intact tissue gaps of 3 mm between them interrupt conduction occasionally, and conduction block may be frequency dependent. Lesion overlap is required to achieve complete conduction block lines. Tachycardias with reentrant activation patterns around a lesions line may be induced. [source] Modulation of rabbit sinoatrial node activation sequence by acetylcholine and isoproterenol investigated with optical mapping techniqueACTA PHYSIOLOGICA, Issue 4 2009D. V. Abramochkin Abstract Aims:, Changes in the rabbit sinoatrial node (SAN) activation sequence with the cholinergic and adrenergic factors were studied. The correlation between the sinus rhythm rate and the leading pacemaker site shift was determined. The hypothesis concerning the cholinergic suppression of nodal cell excitability as one of the mechanisms associated with pacemaker shift was tested. Methods:, A high-resolution optical mapping technique was used to register beat-to-beat changes in the SAN activation pattern under the influence of the cholinergic and adrenergic factors. Results:, Acetylcholine (10 ,m) and strong intramural parasympathetic nerve stimulation caused a pacemaker shift as well as rhythmic slowing and the formation of an inexcitable region in the central part of SAN. In this region the generation of action potentials was suppressed. The slowing of the sinus rhythm (which exceeded 12.8 ± 3.1% of the rhythm control rate) always accompanied the pacemaker shift. Isoproterenol (10, 100 nm, 1 ,m) and sympathetic postganglionic nerve stimulation also evoked a pacemaker shift but without formation of an inexcitable zone. The acceleration of the sinus rhythm, which exceeded 10.5 ± 1.3% of the control rate of the rhythm, always accompanied the shift. Conclusions:, Both cholinergic and adrenergic factors cause pacemaker shifts in the rabbit SAN. While modest changes in the sinus rhythm do not coincide with the pacemaker shift, greater changes always accompany the shift and may be caused by it, according to one hypothesis. The formation of an inexcitable zone at the place where the leading pacemaker is situated is one of the mechanisms associated with pacemaker shift. [source] Unpredictable feeding schedules unmask a system for daily resetting of behavioural and metabolic food entrainmentEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2007Carolina Escobar Abstract Restricted feeding schedules (RFS) are a potent Zeitgeber that uncouples daily metabolic and clock gene oscillations in peripheral tissues from the suprachiasmatic nucleus (SCN), which remains entrained to the light,dark cycle. Under RFS, animals develop food anticipatory activity (FAA), characterized by arousal and increased locomotion. Food availability in nature is not precise, which suggests that animals need to adjust their food-associated activity on a daily basis. This study explored the capacity of rats to adjust to variable and unpredictable feeding schedules. Rats were exposed either to RFS with fixed daily meal (RF) or to a variable meal time (VAR) during the light phase. RF and VAR rats exhibited daily metabolic oscillations driven by the last meal event; however, VAR rats were not able to show a robust adjustment in the anticipating corticosterone peak. VAR rats were unable to exhibit FAA but exhibited a daily activation pattern in phase with the previous meal. In both groups the dorsomedial nucleus of the hypothalamus and arcuate nucleus, involved in energy balance, exhibited increased c-Fos expression 24 h after the last meal, while only RF rats exhibited low c-Fos expression in the SCN. Data show that metabolic and behavioural food-entrained rhythms can be reset on a daily basis; the two conditions elicit a similar hypothalamic response, while only the SCN is inhibited in rats exhibiting anticipatory activity. The variable feeding strategy uncovered a rapid (24-h basis) resetting mechanism for metabolism and general behaviour. [source] Cortical mechanisms of smooth pursuit eye movements with target blanking.EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2004An fMRI study Abstract Smooth pursuit eye movements are evoked by retinal image motion of visible moving objects and can also be driven by the internal representation of a target due to extraretinal mechanisms (e.g. efference copy). To delineate the corresponding neuronal correlates, functional magnetic resonance imaging at 1.5 T was applied during smooth pursuit at 10 °/s with continuous target presentation and target blanking for 1 s to 16 right-handed healthy males. Eye movements were assessed during scanning sessions by infra-red reflection oculography. Smooth pursuit performance was optimal when the target was visible but decreased to a residual velocity of about 30% of the velocity observed during continuous target presentation. Random effects analysis of the imaging data yielded an activation pattern for smooth pursuit in the absence of a visual target (in contrast to continuous target presentation) which included a number of cortical areas in which extraretinal information is available such as the frontal eye field, the superior parietal lobe, the anterior and the posterior intraparietal sulcus and the premotor cortex, and also the supplementary and the presupplementary eye field, the supramarginal gyrus, the dorsolateral prefrontal cortex, cerebellar areas and the basal ganglia. We suggest that cortical mechanisms such as prediction, visuo-spatial attention and transformation, multimodal visuomotor control and working memory are of special importance for maintaining smooth pursuit eye movements in the absence of a visible target. [source] Antero-posterior activity changes in the superficial masseter muscle after exposure to experimental painEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2002Jens C. Türp The aim of this randomized, controlled, double-blind study was to examine how the activation pattern of the masseter muscle changes during natural function when experimental pain is induced in a discrete anterior area of the muscle. In 20 subjects, three bipolar surface electrodes and three intramuscular fine-wire electrodes (antero-posterior mapping) were simultaneously attached above and in the right masseter muscle to record the electromyographic (EMG) activity during unilateral chewing before and after infusion of a 0.9% isotonic and 5% hypertonic saline bolus in the anterior area of the muscle. The activity of the contralateral masseter muscle was registered by surface electrodes. In addition, the development of pain intensity was quantitatively measured with a numerical rating scale (NRS). While both saline concentrations caused pain, the hypertonic solution evoked stronger pain. The experiments also provided evidence of a significant although differential activity reduction of the ipsilateral masseter muscle in the antero-posterior direction. The activity reduction decreased with increasing distance from the location of the infusion. The results support the idea that the strategy of differential activation protects the injured muscle while simultaneously maintaining optimal function. [source] Cortical and subcortical correlates of functional electrical stimulation of wrist extensor and flexor muscles revealed by fMRIHUMAN BRAIN MAPPING, Issue 3 2009Armin Blickenstorfer Abstract The main scope of this study was to test the feasibility and reliability of FES in a MR-environment. Functional Electrical Stimulation (FES) is used in the rehabilitation therapy of patients after stroke or spinal cord injury to improve their motor abilities. Its principle lies in applying repeated electrical stimulation to the relevant nerves or muscles for eliciting either isometric or concentric contractions of the treated muscles. In this study we report cerebral activation patterns in healthy subjects undergoing fMRI during FES stimulation. We stimulated the wrist extensor and flexor muscles in an alternating pattern while BOLD-fMRI was recorded. We used both block and event-related designs to demonstrate their feasibility for recording FES activation in the same cortical and subcortical areas. Six out of fifteen subjects repeated the experiment three times within the same session to control intraindividual variance. In both block and event-related design, the analysis revealed an activation pattern comprising the contralateral primary motor cortex, primary somatosensory cortex and premotor cortex; the ipsilateral cerebellum; bilateral secondary somatosensory cortex, the supplementary motor area and anterior cingulate cortex. Within the same subjects we observed a consistent replication of the activation pattern shown in overlapping regions centered on the peak of activation. Similar time course within these regions were demonstrated in the event-related design. Thus, both techniques demonstrate reliable activation of the sensorimotor network and eventually can be used for assessing plastic changes associated with FES rehabilitation treatment. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] Covariations among fMRI, skin conductance, and behavioral data during processing of concealed informationHUMAN BRAIN MAPPING, Issue 12 2007Matthias Gamer Abstract Imaging techniques have been used to elucidate the neural correlates that underlie deception. The scientifically best understood paradigm for the detection of deception, however, the guilty knowledge test (GKT), was rarely used in imaging studies. By transferring a GKT-paradigm to a functional magnetic resonance imaging (fMRI) study, while additionally quantifying reaction times and skin conductance responses (SCRs), this study aimed at identifying the neural correlates of the behavioral and electrodermal response pattern typically found in GKT examinations. Prior to MR scanning, subjects viewed two specific items (probes) and were instructed to hide their knowledge of these. Two other specific items were designated as targets and required a different behavioral response during the experiment and eight items served as irrelevant stimuli. Reaction times and SCR amplitudes differed significantly between all three item types. The neuroimaging data revealed that right inferior frontal and mid-cingulate regions were more active for probe and target trials compared to irrelevants. Moreover, the differential activation in the right inferior frontal region was modulated by stimulus conflicts. These results were interpreted as an increased top-down influence on the stimulus-response-mapping for concealed and task-relevant items. Additionally, the influence of working memory and retrieval processes on this activation pattern is discussed. Using parametric analyses, reaction times and SCR amplitudes were found to be linearly related to activity in the cerebellum, the right inferior frontal cortex, and the supplementary motor area. This result provides a first link between behavioral measures, sympathetic arousal, and neural activation patterns during a GKT examination. Hum Brain Mapp 2007. © 2007 Wiley-Liss, Inc. [source] Toward brain correlates of natural behavior: fMRI during violent video gamesHUMAN BRAIN MAPPING, Issue 12 2006Klaus Mathiak Abstract Modern video games represent highly advanced virtual reality simulations and often contain virtual violence. In a significant amount of young males, playing video games is a quotidian activity, making it an almost natural behavior. Recordings of brain activation with functional magnetic resonance imaging (fMRI) during gameplay may reflect neuronal correlates of real-life behavior. We recorded 13 experienced gamers (18,26 years; average 14 hrs/week playing) while playing a violent first-person shooter game (a violent computer game played in self-perspective) by means of distortion and dephasing reduced fMRI (3 T; single-shot triple-echo echo-planar imaging [EPI]). Content analysis of the video and sound with 100 ms time resolution achieved relevant behavioral variables. These variables explained significant signal variance across large distributed networks. Occurrence of violent scenes revealed significant neuronal correlates in an event-related design. Activation of dorsal and deactivation of rostral anterior cingulate and amygdala characterized the mid-frontal pattern related to virtual violence. Statistics and effect sizes can be considered large at these areas. Optimized imaging strategies allowed for single-subject and for single-trial analysis with good image quality at basal brain structures. We propose that virtual environments can be used to study neuronal processes involved in semi-naturalistic behavior as determined by content analysis. Importantly, the activation pattern reflects brain-environment interactions rather than stimulus responses as observed in classical experimental designs. We relate our findings to the general discussion on social effects of playing first-person shooter games. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source] Direction-dependent visual cortex activation during horizontal optokinetic stimulation (fMRI study)HUMAN BRAIN MAPPING, Issue 4 2006Sandra Bense Abstract Looking at a moving pattern induces optokinetic nystagmus (OKN) and activates an assembly of cortical areas in the visual cortex, including lateral occipitotemporal (motion-sensitive area MT/V5) and adjacent occipitoparietal areas as well as ocular motor areas such as the prefrontal cortex, frontal, supplementary, and parietal eye fields. The aim of this functional MRI (fMRI) study was to investigate (1) whether stimulus direction-dependent effects can be found, especially in the cortical eye fields, and (2) whether there is a hemispheric dominance of ocular motor areas. In a group of 15 healthy subjects, OKN in rightward and leftward directions was visually elicited and statistically compared with the control condition (stationary target) and with each other. Direction-dependent differences were not found in the cortical eye fields, but an asymmetry of activation occurred in paramedian visual cortex areas, and there were stronger activations in the hemisphere contralateral to the slow OKN phase (pursuit). This can be explained by a shift of the mean eye position of gaze (beating field) in the direction of the fast nystagmus phases of approximately 2.6 degrees, causing asymmetrical visual cortex stimulation. The absence of a significant difference in the activation pattern of the cortical eye fields supports the view that the processing of eye movements in both horizontal directions is mediated in the same cortical ocular motor areas. Furthermore, no hemispheric dominance for OKN processing was found in right-handed volunteers. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Control of semantic interference in episodic memory retrieval is associated with an anterior cingulate-prefrontal activation patternHUMAN BRAIN MAPPING, Issue 2 2001Manfred Herrmann Prefrontal activation is a consistent finding in functional neuroimaging studies of episodic memory retrieval. In the present study we aimed at a further analysis of prefrontal neural systems involved in the executive control of context-specific properties in episodic memory retrieval using an event-related fMRI design. Nine subjects were asked to learn two 20-item word lists that consisted of concrete nouns assigned to four semantic categories. Ten items of both word lists referred to the same semantic category. Subjects were instructed to determine whether nouns displayed in random order corresponded to the first 20-item target list. The interference evoked by the retrieval of semantically related items of the second list resulted in significantly longer reaction times compared to the noninterference condition. Contrasting the interference against the noninterference retrieval condition demonstrated an activation pattern that comprised a right anterior cingulate and frontal opercular area and a left-lateralized dorsolateral prefrontal region. Trial averaged time series revealed that the PFC areas were selectively activated at the interference condition and did not respond to the familiarity of learned words. These findings suggest a functionally separable role of prefrontal cortical areas mediating processes associated with the executive control of interfering context information in episodic memory retrieval. Hum. Brain Mapping 13:94,103, 2001. © 2001 Wiley-Liss, Inc. [source] Successful Catheter Ablation and Documentation of the Activation and Propagation Pattern During a Left Atrial Focal Tachycardia in a Patient with Cor Triatriatum SinisterJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2010KOICHIRO EJIMA M.D. Atrial Tachycardia in Cor Triatriatum. We report a case of an atrial tachycardia (AT) originating from the left atrium (LA) associated with cor triatriatum sinister. Electroanatomical mapping of the 2 subdivided chambers of the LA during the AT revealed a centrifugal activation pattern from the posterior wall of the accessory chamber near the left superior pulmonary vein. The propagation map on the CARTO system revealed that the AT wave front spread centrifugally over the "accessory chamber," turned around the edge of the membrane subdividing the LA, and then spread over the "main chamber." A single radiofrequency application successfully abolished the AT. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1050-1054, September 2010) [source] Usefulness of Interatrial Conduction Time to Distinguish Between Focal Atrial Tachyarrhythmias Originating from the Superior Vena Cava and the Right Superior Pulmonary VeinJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2008KUAN-CHENG CHANG M.D. Objective: Differentiation of the tachycardia originating from the superior vena cava (SVC) or the right superior pulmonary vein (RSPV) is limited by the similar surface P-wave morphology and intraatrial activation pattern during tachycardia. We sought to find a simple method to distinguish between the two tachycardias by analyzing the interatrial conduction time. Methods: Sixteen consecutive patients consisting of 8 with SVC tachycardia and the other 8 with RSPV tachycardia were studied. The interatrial conduction time from the high right atrium (HRA) to the distal coronary sinus (DCS) and the intraatrial conduction time from the HRA to the atrial electrogram at the His bundle region (HIS) were measured during the sinus beat (SR) and during the tachycardia-triggering ectopic atrial premature beat (APB). The differences of interatrial (,[HRA-DCS]SR-APB) and intraatrial (,[HRA-HIS]SR-APB) conduction time between SR and APB were then obtained. Results: The mean ,[HRA-DCS]SR-APB was 1.0 ± 5.2 ms (95% confident interval [CI],3.3,5.3 ms) in SVC tachycardia and 38.5 ± 8.8 ms (95% CI 31.1,45.9 ms) in RSPV tachycardia. The mean ,[HRA-HIS]SR-APB was 1.5 ± 5.3 ms (95% CI ,2.9,5.9 ms) in SVC tachycardia and 19.9 ± 12.0 ms (95% CI 9.9,29.9 ms) in RSPV tachycardia. The difference of ,[HRA-DCS]SR-APB between SVC and RSPV tachycardias was wider than that of ,[HRA-HIS]SR-APB (37.5 ± 9.3 ms vs. 18.4 ± 15.4 ms, P < 0.01). Conclusions: The wide difference of the interatrial conduction time ,[HRA-DCS]SR-APB between SVC and RSPV tachycardias is a useful parameter to distinguish the two tachycardias and may avoid unnecessary atrial transseptal puncture. [source] Mapping of Epicardial Activation in a Rabbit Model of Chronic Myocardial Infarction:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2007Endocardial, Epicardial Pacing, Response to Atrial Introduction: This study examines the consequences of a large transmural apical infarct on the epicardial electrical activity in isolated rabbit hearts. Methods and Results: Hearts were isolated 8 weeks after coronary artery ligation. Membrane voltage from the epicardial surface of the left ventricle (LV) including the infarct was monitored using the voltage sensitive dye RH237. Optical action potentials were detected from the epicardial surface of the infarct; the signal amplitude was ,20% of those in the noninfarcted zone (NZ). Epicardial activation mapping of the LV free wall showed that during right atrial (RA) pacing, the activation sequence was not significantly different between infarcted and sham-operated groups. However, direct stimulation of the epicardium in the NZ revealed an area of slow conduction velocity (CV ,5 cm/s,1, ,10% of normal values) at the margin of the infarct zone (IZ). Within the IZ, CV was ,50% of normal. A prominent endocardial rim of myocardium in the infarct was not the source of epicardial optical signals because chemical ablation of the endocardium did not affect the epicardial activation pattern. Concluson: Therefore, remnant groups of myocytes in the mid-wall and epicardium of the infarct scar support normal electrical activation during RA pacing. Areas of delayed conduction emerge only on epicardial stimulation. [source] Focal Atrial Tachycardia Originating from the Left Atrial Appendage: Electrocardiographic and Electrophysiologic Characterization and Long-Term Outcomes of Radiofrequency AblationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2007WANG YUN-LONG M.D. Introduction: This study sought to investigate electrophysiologic characteristics and radiofrequency ablation (RFA) in patients with focal atrial tachycardia (AT) arising from the left atrial appendage (LAA). Methods: This study included seven patients undergoing RFA with focal AT. Activation mapping was performed during tachycardia to identify an earlier activation in the left atria and the LAA. The atrial appendage angiography was performed to identify the origin in the LAA before and after RFA. Results: AT occurred spontaneously or was induced by isoproterenol infusion rather than programmed extrastimulation and burst atrial pacing in any patient. The tachycardia demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P wave was highly positive in inferior leads in all patients. Lead V1 showed upright or biphasic (±) component in all patients. Lead V2,V6 showed an isoelectric component in five patients or an upright component with low amplitude (<0.1 mV) in two patients. Earliest endocardial activity occurred at the distal coronary sinus (CS) ahead of P wave in all seven patients. Mean tachycardia cycle length was 381 ± 34 msec and the earliest endocardial activation at the successful RFA site occurred 42.3 ± 9.6 msec before the onset of P wave. RFA was acutely successful in all seven patients. Long-term success was achieved in seven of the seven over a mean follow-up of 24 ± 5 months. Conclusions: The LAA is an uncommon site of origin for focal AT (3%). There were consistent P-wave morphology and endocardial activation associated with this type of AT. The LAA focal ablation is safe and effective. Long-term success was achieved with focal ablation in all patients. [source] On the Atrial Response to Focal Discharges in ManJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2004HEMANTH RAMANNA M.D. Introduction: Triggers and vulnerability are key factors for the occurrence of atrial fibrillation (AF). The aim of this study was to assess spatial dispersion of atrial refractoriness and vulnerability in response to both focal discharges as well as programmed electrical stimulation in patients undergoing ablation of atrial arrhythmogenic foci. Methods and Results: Twenty-nine patients were studied, and 12 right atrial unipolar electrograms were recorded. Inducibility of AF was assessed by a pacing protocol that started with one extrastimulus, followed by more aggressive pacing until AF was obtained. Mean fibrillatory intervals were used to assess the local refractoriness of each recording site. Spatial dispersion of refractoriness was calculated as the coefficient of dispersion (CD value: standard deviation of the mean of all local mean fibrillatory intervals as a percentage of the overall mean fibrillatory interval). Based on our previous study, a CD value , 3.0 was defined as normal, whereas a CD value >3.0 was considered enhanced spatial dispersion of refractoriness. Fifteen of 29 patients had normal dispersion of refractoriness (mean CD value 1.65 ± 0.43), and AF was inducible with burst pacing only. These patients had focal discharges causing rapid atrial tachycardia with a focal activation pattern. Activation mapping of focal activity was possible in 14 of 15 patients. Focal triggering of AF occurred in only 1 of 15 patients. Fourteen of 29 patients had enhanced dispersion (mean CD value 4.2 ± 0.72). AF was inducible with a single extrastimulus in 11 of 14 patients (P < 0.001). Focal triggering of AF occurred in all 14 patients. Conclusion: Spatial dispersion of atrial refractoriness determines whether focal atrial discharges trigger AF with disorganized activity or, alternatively, only rapid atrial tachycardia. (J Cardiovasc Electrophysiol, Vol. 15, pp. 1-8, June 2004) [source] Relationship Between Connexins and Atrial Activation During Human Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2004M.R.C.P., PRAPA KANAGARATNAM Ph.D. Introduction: Gap junctional connexin proteins (connexin40 [Cx40], connexin43 [Cx43]) are a determinant of myocardial conduction and are implicated in the development of atrial fibrillation (AF). We hypothesized that atrial activation pattern during AF is related to connexin expression and that this relationship is altered by AF-induced remodeling in the fibrillating atria of chronic AF. Methods and Results: Isochronal activation mapping was performed during cardiac surgery on the right atria of patients in chronic AF (n = 13) using an epicardial electrode array. The atrial activation pattern was categorized using a complexity score based on the number of propagating wavefronts of activation and by grouping atria into those capable of uniform planar activation (simple) and those that were not (complex). The activation pattern was correlated with the levels of Cx43 and Cx40 signal measured by immunoconfocal quantification of biopsies from the mapped region. We studied the impact of electrical remodeling by comparing these findings with the unremodeled atria of patients in sinus rhythm during pacing-induced sustained AF (n = 17). In chronic AF, atria with complex activation had lower Cx40 signal than atria showing simple activation (0.013 ± 0.006 ,m2/,m2 vs 0.027 ± 0.009 ,m2/,m2, P < 0.02), with the relative connexin signal (Cx40/Cx40+Cx43) correlating with complexity score (P = 0.01, r =,0.74). This relationship did not occur in the unremodeled atria, and increased heterogeneity of distribution of Cx40 labeling in chronic AF was the only evidence of connexin remodeling that we detected in the overall group. Conclusion: The pattern of atrial activation is related to immunoconfocal connexin signal only in the fully remodeled atria of chronic AF. This suggests that intercellular coupling and pattern of atrial activation are interrelated, but only in conjunction with the remodeling of atrial electrophysiology that occurs in chronic AF. (J Cardiovasc Electrophysiol, Vol. 15, pp. 206-213, February 2004) [source] Focal Origin of Atrial Tachycardia in Dogs with Rapid Ventricular Pacing-Induced Heart FailureJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2003GUILHERME FENELON M.D. Introduction: Dogs with rapid ventricular pacing-induced congestive heart failure (CHF) have inducible atrial tachycardia (AT), with a mechanism consistent with delayed afterdepolarization-mediated triggered activity. We assessed the hypothesis that AT has a focal origin. Methods and Results: Twenty-one CHF dogs undergoing 3 to 4 weeks of ventricular pacing at 235 beats/min were studied. Biatrial epicardial mapping of 20 sustained AT episodes (cycle length [CL], 175 ± 53 msec) in 5 dogs revealed an area of earliest activation in the right atrial (RA) free wall (13 episodes), RA appendage (4 episodes), or between the pulmonary veins (3 episodes). Total epicardial activation time during AT (73 ± 19 msec) was similar to that during sinus rhythm (72 ± 13 msec) and on average was <50% of the AT CL. Higher-density mapping of the RA free wall during 30 sustained AT episodes (163 ± 55 msec) in 9 dogs identified a site of earliest activation along the sulcus terminalis most frequently as a stable, focal activation pattern from a single site. Endocardial mapping of 49 sustained AT episodes (156 ± 27 msec) in 10 dogs revealed multiple sites of AT origin arising along the crista terminalis and pulmonary veins. Right and left ATs were terminated with discrete radiofrequency ablation, but other ATs remained inducible. A rapid, left AT generating an ECG pattern of atrial fibrillation was ablated inside the pulmonary vein. Conclusion: AT induced in this CHF model after 3 to 4 weeks of rapid ventricular pacing has an activation pattern consistent with a focal origin. Sites of earliest activation are distributed predominately along the crista terminalis and within or near the pulmonary veins. (J Cardiovasc Electrophysiol, Vol. 14, pp. ***-***, October 2003) [source] High-Resolution Mapping of Tachycardia Originating from the Superior Vena Cava: Evidence of Electrical Heterogeneity, Slow Conduction, and Possible Circus Movement ReentryJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2002DIPEN C. SHAH M.D. Superior Vena Cava Reentry. High-resolution mapping of a tachycardia originating from the superior vena cava (SVC) in a patient with atrial fibrillation is described. Unidirectional circuitous repetitive activation encompassing the full tachycardia cycle length was documented around a line of block within the myocardial sleeve of the SVC. Intermittent conduction to the right atrium resulted in an irregular atrial tachycardia. Evidence of electrical heterogeneity and slow conduction persisted in sinus rhythm and was exaggerated by premature stimulation but did not reproduce the activation pattern during tachycardia. All the available evidence is best compatible with circus movement reentry within the SVC, with marked slow and anisotropic conduction responsible for the restricted dimensions of the reentrant circuit. These findings may suggest a similar substrate and arrhythmia mechanism in the myocardium of the pulmonary veins. [source] Electroanatomic Analysis of Sinus Impulse Propagation in Normal Human AtriaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2002ROBERTO DE PONTI M.D. Sinus Impulse Propagation in Normal Human Atria.Introduction: Better understanding of atrial propagation during sinus rhythm (SR) in normal hearts under the most normal physiologic conditions may be propaedeutic to pathophysiologic studies of complex atrial arrhythmias. In this study, qualitative and quantitative analyses of sinus impulse propagation in both atria were performed by electroanatomic mapping in patients with no organic heart disease who were undergoing an electrophysiologic procedure. Methods and Results: Seven patients (5 men and 2 women; age 37 ± 11 years) undergoing ablation of a left-sided accessory pathway were considered. Associated heart disease and coexisting atrial arrhythmias were excluded. After obtaining informed consent, electroanatomic mapping of both atria was performed during SR using a nonfluoroscopic system in the postablation phase. Mapping was accomplished in all patients with no complications. Qualitative analysis showed that sinus impulse propagation gives a reproducible activation pattern with minor individual variations. During interatrial propagation, two breakthroughs (anterior and posterior) in the left atrium are observed in the majority of cases. The anterior breakthrough, which reflects conduction over Bachmann's bundle, is predominant and shows a peculiar "preexcitation-like" endocardial activation pattern. Quantitative analysis showed minimal individual variations of propagation time intervals. Atria are activated simultaneously for 65% ± 9% of the duration of the atrial systolic time interval. Conclusion: In normal humans, electroanatomic mapping of SR identifies a typical and reproducible propagation pattern during SR. Bachmann's bundle plays the most important role in interatrial propagation. Atria are activated simultaneously by sinus impulse for a relevant portion of the systolic time interval. [source] Comparison of TCA and ICA techniques in fMRI data processingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2004Xia Zhao MS Abstract Purpose To make a quantitative comparison of temporal cluster analysis (TCA) and independent component analysis (ICA) techniques in detecting brain activation by using simulated data and in vivo event-related functional MRI (fMRI) experiments. Materials and Methods A single-slice MRI image was replicated 150 times to simulate an fMRI time series. An event-related brain activation pattern with five different levels of intensity and Gaussian noise was superimposed on these images. Maximum contrast-to-noise ratio (CNR) of the signal change ranged from 1.0 to 2.0 by 0.25 increments. In vivo visual stimulation fMRI experiments were performed on a 1.9 T magnet. Six human volunteers participated in this study. All imaging data were analyzed using both TCA and ICA methods. Results Both simulated and in vivo data have shown that no statistically significant difference exists in the activation areas detected by both ICA and TCA techniques when CNR of fMRI signal is larger than 1.75. Conclusion TCA and ICA techniques are comparable in generating functional brain maps in event-related fMRI experiments. Although ICA has richer features in exploring the spatial and temporal information of the functional images, the TCA method has advantages in its computational efficiency, repeatability, and readiness to average data from group subjects. J. Magn. Reson. Imaging 2004;19:397,402. © 2004 Wiley-Liss, Inc. [source] Blood leucocyte cytokine production after LPS stimulation at different concentrations of glucose and/or insulinACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 2 2009S. BEITLAND Background: Previous studies have indicated that alterations in blood glucose and/or insulin levels modify the inflammatory response. The purpose of this study was to elucidate whether increased levels of glucose and/or insulin influence the activation pattern of blood leucocytes and their production of cytokines in vitro. Methods: Venous blood was obtained from eight healthy male volunteers after an overnight fast. Glucose and/or insulin were added to aliquots of whole blood to increase the blood glucose concentration by 5 or 20 mmol/l and/or the insulin concentration by 6 or 30 nmol/l, respectively, before stimulation with E. coli lipopolysaccharide (LPS) at concentrations of 10, 100 or 1000 ng/ml. The samples were subsequently incubated at 37 °C for 6 h before cytokine measurements. After centrifugation the levels of interleukins (IL)-1,, IL-6, IL-8, IL-10 and tumour necrosis factor (TNF)-, were measured in plasma using enzyme-linked immuno-sorbent assays. The results were compared with cytokine levels in parallel control samples to which only identical amounts of LPS were added. Results: The LPS-stimulated production of IL-1, was significantly reduced by on average 26% in samples to which glucose 20 mmol/l was added; addition of insulin and/or glucose 5 mmol/l had no apparent effect on the IL-1, production at any LPS concentration. The levels of IL-6, IL-8, IL-10 and TNF-, were not manifestly altered by addition of glucose and/or insulin at any LPS concentration. Conclusion: A substantial increase in blood glucose concentration changed the IL-1, production, but not the production of other cytokines, in response to LPS stimulation. [source] Whole-brain functional magnetic resonance imaging mapping of acute nociceptive responses induced by formalin in rats using atlas registration-based event-related analysisJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2008Yen-Yu I. Shih Abstract Nociceptive neuronal activation in subcortical regions has not been well investigated in functional magnetic resonance imaging (fMRI) studies. The present report aimed to use the blood oxygenation level-dependent (BOLD) fMRI technique to map nociceptive responses in both subcortical and cortical regions by employing a refined data processing method, the atlas registration-based event-related (ARBER) analysis technique. During fMRI acquisition, 5% formalin (50 ,l) was injected into the left hindpaw to induce nociception. ARBER was then used to normalize the data among rats, and images were analyzed using automatic selection of the atlas-based region of interest. It was found that formalin-induced nociceptive processing increased BOLD signals in both cortical and subcortical regions. The cortical activation was distributed over the cingulate, motor, somatosensory, insular, and visual cortices, and the subcortical activation involved the caudate putamen, hippocampus, periaqueductal gray, superior colliculus, thalamus, and hypothalamus. With the aid of ARBER, the present study revealed a detailed activation pattern that possibly indicated the recruitment of various parts of the nociceptive system. The results also demonstrated the utilization of ARBER in establishing an fMRI-based whole-brain nociceptive map. The formalin induced nociceptive images may serve as a template of central nociceptive responses, which can facilitate the future use of fMRI in evaluation of new drugs and preclinical therapies for pain. © 2008 Wiley-Liss, Inc. [source] Spontaneously changing muscular activation pattern in patients with cervical dystoniaMOVEMENT DISORDERS, Issue 6 2001A. Münchau MD Abstract The objective of this study was to determine stability of the neck muscle activation pattern in a given dystonic head position in patients with cervical dystonia (CD). We assessed 26 patients with CD and botulinum toxin (BT) treatment failure before surgical denervation. None of them had received BT injections for at least 4 months. To relate dystonic head position to underlying neck muscle activity, we used synchronised video and poly-electromyographic (EMG) recording over a period of 10 minutes. The muscle activation pattern during constant ("stable") maximal dystonic excursions was analysed. EMG data of nine patients was excluded from the analysis, as these patients had a constantly changing head position or marked head tremor. In the remaining 17 patients, who had a fairly stable dystonic position, muscular activation patterns during the recording spontaneously changed in nine (Group A) while in eight it remained stable (Group B). There was no significant difference in demographic variables between the two groups other than a male predominance in Group A. However, the retrospectively determined initial response to BT treatment (before BT treatment failure had occurred) was significantly worse in Group A as compared with Group B. Neck muscle activation patterns can spontaneously change in CD patients despite constant dystonic head position, implying an inherent variability of the underlying central motor program in some patients. This should be considered when BT treatment response is unsatisfactory, and should also be taken into account when interpreting results of EMG recordings of neck muscles in these patients. © 2001 Movement Disorder Society. [source] Variability in Postpacing Intervals Predicts Global Ventricular Activation Pattern during TachycardiaPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2010ILYAS K. COLOMBOWALA M.D. Introduction: Assessment of ventricular activation pattern is critical to the successful ablation of ventricular tachycardia (VT). We have previously shown that the global atrial activation pattern during tachycardia can be rapidly and accurately assessed by calculating the postpacing interval variability (PPIV); PPIV was minimal in circuitous tachycardias and highly variable in centrifugal tachycardias. In the present study, we use the PPIV to determine the ventricular global activation pattern during VT. Methods: Patients with mappable VT were included. We defined global ventricular activation as either centrifugal (arising from a focus with radial expansion) or circuitous (gross macro-reentrant circuit), based on the findings of electroanatomic mapping. PPIV was calculated as the difference in postpacing interval with right ventricular apical overdrive pacing during tachycardia at cycle lengths (CL) 10 ms and 30-ms shorter than tachycardia, regardless of the origin of the tachycardia. We studied 20 patients with 23 VTs (11 centrifugal, mean CL 390 ± 36.1 ms; 12 circuitous, mean CL 418 ± 75.7 ms). Results: The mean PPIV was 45 ± 16 ms for patients with centrifugal VT and 6.7 ± 4.1 ms for patients with circuitous VT. Rank sum analysis of PPIV showed a significant difference between the two groups (P < 0.05). Conclusions: Our data suggest that the global ventricular activation pattern during VT can be rapidly and accurately defined by assessing the PPIV. This technique allows for a rapid confirmation of the tachycardia activation and significantly facilitates mapping and ablation. (PACE 2010; 33:129,134) [source] Excitation of the Intrinsic Conduction System Through His and Interventricular Septal PacingPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2006TIMOTHY G LASKE Background: Direct His bundle pacing results in rapid synchronous ventricular activation. However, clinical experiences with such pacing have been associated with long procedure times and compromised pacing and sensing performance. Methods: We evaluated myocardial activation sequences (AS) for pacing of the His bundle and peri-His region and assessed acute pacing performance using custom-designed plunge electrodes. Unipolar pacing was performed in isolated swine hearts (n = 10) using four quadripolar stimulation/sensing electrodes implanted into the interventricular septum and equally spaced between the membranous septum and the coronary sinus ostium (zones 1,4, respectively; electrode depth (ED) 1 = most distal, ED 4 = most proximal). Optimal pacing sites were defined as: pacing thresholds ,1.5 V, a P-R ratio of ,0.5, and ,50% occurrence of an intrinsic midseptal left ventricular (LV) endocardial electrical breakout (BO) and activation pattern. Results: Pacing thresholds improved with greater depth of electrode location within the septum (ED 1: 1.51 ± 0.8 V vs ED 4: 5.2 ± 3.8 V, P < 0.001), as did the P-R ratio (0.34 ± 0.6 vs 0.78 ± 1.0, P < 0.05). His potentials were only observed in zone 1 and 2 electrodes (0.12 and 0.02 mV, respectively). Only electrodes in zones 1 and 2 produced LV endocardial electrical BOs in the midseptal region that demonstrated an intrinsic-like endocardial AS. Depth 1 and 2 electrodes (11.75 and 8.75 mm, respectively) in zone 1 satisfied all three optimal pacing site requirements. Conclusions: This study has shown that LV activation patterns similar to sinus rhythm may be achieved without direct activation of the His bundle, while maintaining acceptable pacing and sensing performance. These data indicate that pacing systems designed to stimulate the tissues below the point at which the His bundle penetrates the central fibrous body may provide improved system efficiency and LV performance in comparison to both direct His bundle pacing and traditional pacing sites. [source] Opposite Effects of Myocardial Stretch and Verapamil on the Complexity of the Ventricular Fibrillatory Pattern: An Experimental StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2000FRANCISCO J. CHORRO CHORRO, F.J., et al.: Opposite Effects of Myocardial Stretch And Verapamil on The Complexity of The Ventricular Fibrillatory Pattern: An Experimental Study. An experimental model is used to analyze the effects of ventricular stretching and verapamil on the activation patterns during VF. Ten Langendorff-perfused rabbit hearts were used to record VF activity with an epicardial multiple electrode before, during, and after stretching with an intraventricular balloon, under both control conditions and during verapamil (Vp) infusion (0.4,0.8 ,mol). The analyzed parameters were dominant frequency (FrD) spectral analysis, the median (MN) of the VF intervals, and the type of activation maps during VF (I = one wavelet without block lines, II = two simultaneous wavelets with block lines, III = three or more wavelets with block lines). Stretch accelerates VF (FrD: 22.8 ± 6.4 vs 15.2 ± 1.0 Hz, P < 0.01; MN: 48 ± 13 vs 68 ± 6 ms, P < 0.01). On fitting the FrD time changes to an exponential model after applying and suppressing stretch, the time constants (stretch: 101.2 ± 19.6 s; stretch suppression: 97.8 ± 33.2 s) do not differ significantly. Stretching induces a significant variation in the complexity of the VF activation maps with type III increments and type I and II decrements (control: I = 17.5%, II = 50.5%, III = 32%; stretch: I = 7%, II = 36.5%, III = 56.5%, P < 0.001). Vp accelerates VF (FrD: 20.9 ± 1.9 Hz, P < 0.001 vs control; MN: 50 ± 5 ms, P < 0.001 vs control) and diminishes activation maps complexity (I = 25.5%, II = 60.5%, III = 14%, P < 0.001 vs control). On applying stretch during Vp perfusion, the fibrillatory process is not accelerated to any greater degree. However, type I and II map decrements and type III increments are recorded, though reaching percentages similar to control (I = 16.5%, II = 53%, III = 30.5%, NS vs control). The following conclusions were found: (1) myocardial stretching accelerates VF and increases the complexity of the VF activation pattern; (2) time changes in the FrD of VF during and upon suppressing stretch fit an exponential model with similar time constants; and (3) although stretching and verapamil accelerate the VF process, they exert opposite effects upon the complexity of the fibrillatory pattern. [source] Abnormal Myocardial and Coronary Vasculature Development in Experimental HypoxiaTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 10 2008Ondrej Nanka Freshly isolated quail embryonic heart at Hamburger-Hamilton stage 28, stained with voltage sensitive dye and optically mapped to reveal ventricular activation pattern (indicated by color isochrones in 1 ms intervals). The activation wave sweeps from left to right in the direction of the arrow. Maturation of ventricular activation patterns is accelerated by hypoxic incubation, as described in detail together with other changes in ventricular angio- and myoarchitecture. From "Abnormal Myocardial and coronary Vasculature Development in Experimental Hypoxia," by Ondrej Nanka, et al., on page 1187, in this issue. [source] | |||||||||||||||||||||||||||||||||||||