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PubMed1995

Activation of MAP kinase and translocation with HSP27 in bombesin-induced contraction of rectosigmoid smooth muscle.

We have investigated whether mitogen-activated protein (MAP) kinase cascade is essential for sustained contraction of smooth muscle cells of the rabbit rectosigmoid. We have identified MAP kinase as one of the enzymes activated by bombesin, performed immunologic studies blocking the activation of MAP kinase, and conducted confocal localization of MAP kinase in relation to heat-shock protein (HSP27), postulated to be involved in the sustained contraction of smooth muscle. Immunoblotting revealed two forms of MAP kinase (42 and 44 kDa). Activation of MAP kinase by bombesin was rapid, reaching a maximum in 30 s and subsequently declining. [D-Phe6,Leu13,psi(CH2NH),Phe14]BN-(6-14), a potent bombesin antagonist, and protein kinase C (PKC) inhibitors 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, calphostin C, and chelerythrine inhibited the increase in MAP kinase induced by bombesin. Immunofluorescent dual labeling and confocal microscopy indicate that these two proteins are closely distributed in resting cells and that during bombesin-induced contraction MAP kinase translocates accompanied by HSP27. In conclusion, a series of events involving PKC activation, MAP kinase activation, and MAP kinase-HSP27 translocation could be the signaling pathway involved in bombesin-induced sustained contraction.

Animals↗
PubMed1998

Inhibition of p42 and p44 MAP kinase does not alter smooth muscle contraction in swine carotid artery.

Caldesmon inhibits myosin ATPase activity; phosphorylation of caldesmon reverses the inhibition. The caldesmon kinase is believed to be mitogen-activated protein (MAP) kinase. MAP kinases are activated during vascular stimulation, but a cause-and-effect relationship between kinase activity and contraction has not been established. We examined the role of MAP kinase in contraction using PD-098059, an inhibitor of MAP kinase kinase (MEK). MAP kinase activity was assessed using an anti-active MAP kinase antibody and direct measurement of MAP kinase catalyzed phosphorylation of myelin basic protein, MBP-(95-98). MAP kinase phosphorylation, stimulated by histamine (50 microM) or phorbol 12,13-dibutyrate (PDBu, 0.1 microM), was inhibited by PD-098059 (100 microM). PD-098059 did not alter the sensitivity or the maximal level of force in smooth muscle stimulated by histamine or PDBu, nor did PD-098059 affect contraction of beta-escin-permeabilized tissue. Our data suggest that p44 and p42 MAP kinases are not involved in regulation of vascular smooth muscle contraction. These results do not, however, preclude a role for other isoforms of the MAP kinase family.

Animals↗
PubMed2000

Evidence for modulation of smooth muscle force by the p38 MAP kinase/HSP27 pathway.

Mitogen-activated protein (MAP) kinases signal to proteins that could modify smooth muscle contraction. Caldesmon is a substrate for extracellular signal-related kinases (ERK) and p38 MAP kinases in vitro and has been suggested to modulate actin-myosin interaction and contraction. Heat shock protein 27 (HSP27) is downstream of p38 MAP kinases presumably participating in the sustained phase of muscle contraction. We tested the role of caldesmon and HSP27 phosphorylation in the contractile response of vascular smooth muscle by using inhibitors of both MAP kinase pathways. In intact smooth muscle, PD-098059 abolished endothelin-1 (ET-1)-stimulated phosphorylation of ERK MAP kinases and caldesmon, but p38 MAP kinase activation and contractile response remained unaffected. SB-203580 reduced muscle contraction and inhibited p38 MAP kinase and HSP27 phosphorylation but had no effect on ERK MAP kinase and caldesmon phosphorylation. In permeabilized muscle fibers, SB-203580 and a polyclonal anti-HSP27 antibody attenuated ET-1-dependent contraction, whereas PD-098059 had no effect. These results suggest that ERK MAP kinases phosphorylate caldesmon in vivo but that activation of this pathway is unnecessary for force development. The generation of maximal force may be modulated by the p38 MAP kinase/HSP27 pathway.

Animals↗
PubMed1998

Hypertonicity activates MAP kinases and inhibits HCO-3 absorption via distinct pathways in thick ascending limb.

Mitogen-activated protein (MAP) kinases are activated by osmotic stress in a variety of cells, but their function and regulation in renal tubules is poorly understood. The present study was designed to examine the osmotic regulation of MAP kinases in the medullary thick ascending limb (MTAL) of the rat and to determine their possible role in the hyperosmotic inhibition of HCO-3 absorption in this segment. Tissues from the inner stripe of the outer medulla and microdissected MTALs were incubated at 37 degreesC in control (290 mosmol/kgH2O) or hyperosmotic (300 mM added mannitol) solution for 15 min. Activities of extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38 MAP kinase were then measured using immune complex assays. Hyperosmolality increased p38 MAP kinase activity (2.3-fold) and ERK activity (2.0-fold) but had no effect on JNK activity (1.1-fold). Exposure to hyperosmolality for various times showed that the activation of p38 MAP kinase was rapid (</=5 min) and was sustained for up to 60 min, whereas the activation of ERK was transient (ERK activity peaked at 15 min, then declined to basal levels at 30 min). Pretreatment with the MAP kinase kinase inhibitor PD98059 (15 microM) blocked the hyperosmotic activation of p38 MAP kinase and ERK but did not prevent hyperosmotic inhibition of HCO-3 absorption. These results show that hyperosmolality differentially activates p38 MAP kinase and ERK in the MTAL. In contrast, we found no evidence for involvement of JNK in the early response to hyperosmotic stress. Eliminating the activation of p38 MAP kinase and ERK does not prevent hyperosmotic inhibition of HCO-3 absorption, suggesting that hyperosmolality inhibits apical membrane Na+/H+ exchange (NHE3) activity via a signaling pathway distinct from these MAP kinase pathways.

Absorption↗
PubMed1997

Transcutaneous multielectrode basket catheter for endocardial mapping and ablation of ventricular tachycardia in the pig.

BACKGROUND: Endocardial mapping using standard electrode catheters is often technically limited in ventricular tachycardia and constitutes a major obstacle to successful ablation. We wished to examine the utility of a basket-shaped multielectrode mapping catheter (MMC) in the mapping and ablation of ventricular tachycardia. METHODS AND RESULTS: This study of sustained monomorphic ventricular tachycardia (SMVT) was conducted in two phases in the postinfarction pig model. In the first phase, the utility of the MMC in providing adequate localization of potential ablation site(s) of SMVT by different techniques (presystolic potentials, pace mapping, and concealed entrainment) was assessed in 21 pigs. In the second phase, ablation of induced SMVT was attempted in 10 pigs. Mapping of SMVT was performed after percutaneous introduction of the MMC to the LV. Comprehensive mapping was performed in 90 episodes of SMVT and required 2.0 to 25 seconds. Diastolic potentials were recorded during 86 episodes; good or identical pace maps (> or = 9 of 12 paced surface ECG leads identical to ventricular tachycardia surface ECG leads) were obtained in 25 of 31 maps, and entrainment was achieved during 28 of 42 SMVTs. In 10 pigs, 10 SMVTs were recorded at least twice and were considered for radiofrequency ablation. An 8-mm tip ablation catheter was advanced to potential ablation sites with a specially designed "homing" device, requiring a median time of 120 seconds. In these 10 pigs, either identical pace map (> or = 11 of 12, 6 SMVTs) or concealed entrainment (4 SMVTs) guided the ablation procedure. After ablation, 8 of 10 SMVTs were rendered noninducible, while 2 pigs died during energy application of degeneration of SMVT to ventricular fibrillation. CONCLUSIONS: The MMC allows rapid, comprehensive, and reliable endocardial mapping during SMVTs, which facilitates successful ablation in the porcine post-myocardial infarction model.

Animals↗
PubMed1998

Lysophosphatidylcholine stimulates MAP kinase activity in rat vascular smooth muscle cells.

Lysophosphatidylcholine (lyso-PC) has been implicated in atherogenesis and the inflammatory process. Although lyso-PC has been reported to contribute to the mitogenic effect of oxidized LDL on rat cultured vascular smooth muscle cells (VSMCs), the signaling mechanisms by which lyso-PC promotes its proliferation are poorly characterized. Mitogen-activated protein (MAP) kinases are important mediators involved in the intracellular network of interacting proteins that transduces extracellular cues to intracellular responses. We therefore examined the effect of lyso-PC on MAP kinase activation, proto-oncogene expression, and AP-1 binding activity using cultured rat VSMC. Marked activation of MAP kinase occurred within 10 minutes of lyso-PC treatment, whereupon rapid inactivation ensued. MAP kinase activation by lyso-PC was concentration-dependent (6.25 to 25 micromol/L). Pertussis toxin treatment did not affect lyso-PC-induced MAP kinase phosphorylation. Lyso-PC (25 micromol/L) also increased the mRNA expression of c-fos and c-jun genes. An electrophoretic mobility shift assay showed that AP-1 binding activity was enhanced by lyso-PC. To examine the upstream signaling of MAP kinase, we used several inhibitors on MAP kinase activation induced by lyso-PC. Although lyso-PC induced sustained increase in intracellular Ca2+ concentration, EGTA had no effect on MAP kinase activation induced by lyso-PC. However, protein kinase C inhibitor GF109203X and downregulation of protein kinase C activity by prolonged treatment with phorbol ester inhibited lyso-PC-induced MAP kinase activation. These data suggest that lyso-PC transmits its mitogenic activity through a MAP kinase-AP-1 pathway, which exists downstream of its protein kinase C activation in VSMCs.

Animals↗
PubMed2006

Dynamics and topographic organization of recursive self-organizing maps.

Recently there has been an outburst of interest in extending topographic maps of vectorial data to more general data structures, such as sequences or trees. However, there is no general consensus as to how best to process sequences using topographic maps, and this topic remains an active focus of neurocomputational research. The representational capabilities and internal representations of the models are not well understood. Here, we rigorously analyze a generalization of the self-organizing map (SOM) for processing sequential data, recursive SOM(RecSOM) (Voegtlin, 2002), as a nonautonomous dynamical system consisting of a set of fixed input maps. We argue that contractive fixed-input maps are likely to produce Markovian organizations of receptive fields on the RecSOM map. We derive bounds on parameter beta (weighting the importance of importing past information when processing sequences) under which contractiveness of the fixed-input maps is guaranteed. Some generalizations of SOM contain a dynamic module responsible for processing temporal contexts as an integral part of the model. We show that Markovian topographic maps of sequential data can be produced using a simple fixed (nonadaptable) dynamic module externally feeding a standard topographic model designed to process static vectorial data of fixed dimensionality (e.g., SOM). However, by allowing trainable feedback connections, one can obtain Markovian maps with superior memory depth and topography preservation. We elaborate on the importance of non-Markovian organizations in topographic maps of sequential data.

Algorithms↗
PubMed1990

Detection of the spatial distribution of late potentials by body surface mapping using forty-five unipolar, leads.

For evaluating the spatial location of late potentials (LPs), the authors designed a new system for the body surface mapping of signal-averaged, filtered ECGs using forty-five thoracic unipolar leads (5 x 9 array). The signals from patients with old myocardial infarction (MI, N = 7) and arrhythmogenic right ventricular dysplasia (ARVD, N = 1) were amplified and passed through a bandpass (100-300 Hz) filter. The departure maps, LP isopotential maps, and LP30 area maps were generated and superimposed. The LP30 duration was determined as the section between the filtered QRS endpoints and points thirty milliseconds (ms) before. Isopotential maps of the LPs showed distinct positive and negative regions. In 7 cases with MI, the extreme was related to the zones indicated by the departure maps, and the LP30 area maps also corresponded to the departure areas. In 1 case of ARVD, endocardial fragmented activity directly recorded at the right ventricle closely corresponded with the region on the LP30 area map. In conclusion, body surface LP isopotential maps and LP30 area maps may provide useful information concerning the spatial distribution of endocardial fragmentation.

Arrhythmias, Cardiac↗
PubMed2005

Web GIS in practice II: interactive SVG maps of diagnoses of sexually transmitted diseases by Primary Care Trust in London, 1997 - 2003.

BACKGROUND: The rates of Sexually transmitted diseases (STDs) in England have been rising steadily since the mid 1990s, making them a major public health concern. In 2003, 672,718 people were diagnosed with an STD in England, and around one third of those cases were diagnosed in London. RESULTS: Using GeoReveal v1.1 for Windows, we produced Web-based interactive choropleth maps of diagnoses of STDs by Primary Care Trust (PCT) in London for the years from 1997 to 2003 http://healthcybermap.org/PCT/STDs/. These maps are in Scalable Vector Graphics (SVG) format and require a freely available Adobe SVG browser plug-in to be displayed. They are based on data obtained from the House of Commons Hansard Written Answers for 15 October 2004. They show steadily rising rates of STDs in London over the covered seven-year period. Also, one can clearly see on the maps that PCTs located in central London had the highest numbers of STD diagnoses throughout the mapped seven years. A companion bar chart allows users to instantly compare the STD figure of a given PCT for a given year against the average figure for all 25 mapped PCTs for the same year, and also compare those figures across all seven years. The maps offer users a rich set of useful features and functions, including the ability to change the classification method in use, the number of ranges in the map, and the colour theme, among others. CONCLUSIONS: Wizard-driven tools like GeoReveal have made it very easy to transform complex raw data into valuable decision support information products (interactive Web maps) in very little time and without requiring much expertise. The resultant interactive maps have the potential of further supporting health planners and decision makers in their planning and management tasks by allowing them to graphically interrogate data, instantly spot trends, and make quick and effective visual comparisons of geographically differentiated phenomena between different geographical areas and over time.SVG makes an ideal format for such maps. SVG is a World Wide Web Consortium non-proprietary, XML-based vector graphics format, and is an extremely powerful alternative to Macromedia(R) Flash and bitmap graphics.

Journal Article↗
PubMed1999

Dissociation of MAP kinase activation and MPF activation in hormone-stimulated maturation of Xenopus oocytes.

MAP kinase activation occurs during meiotic maturation of oocytes from all animals, but the requirement for MAP kinase activation in reinitiation of meiosis appears to vary between different classes. In particular, it has become accepted that MAP kinase activation is necessary for progesterone-stimulated meiotic maturation of Xenopus oocytes, while this is clearly not the case in other systems. In this paper, we demonstrate that MAP kinase activation in Xenopus oocytes is an early response to progesterone and can be temporally dissociated from MPF activation. We show that MAP kinase activation can be suppressed by treatment with geldanamycin or by overexpression of the MAP kinase phosphatase Pyst1. A transient and low-level early activation of MAP kinase increases the efficiency of cell cycle activation later on, when MAP kinase activity is no longer essential. Many oocytes can still undergo reinitiation of meiosis in the absence of active MAP kinase. Suppression of MAP kinase activation does not affect the formation or activation of Cdc2-cyclin B complexes, but reduces the level of active Cdc2 kinase. We discuss these findings in the context of a universal mechanism for meiotic maturation in oocytes throughout the animal kingdom.

Animals↗
PubMed1991

Spatial distribution of late potentials assessed by signal-averaged body surface mapping.

In order to evaluate the spatial location of late potentials (LPs), we designed a new system for the body surface mapping of signal-averaged, filtered ECG using 45 thoracic unipolar leads (5 X 9 array). Signals from patients with old myocardial infarction (MI, N = 8), arrhythmogenic right ventricular dysplasia (N = 1) and dilated cardiomyopathy (N = 2) were amplified and passed through a digital bandpass filter (60-300Hz). Departure maps, LP isopotential maps, and LP30 area maps were generated and superimposed. The LP30 duration was determined as the section between the filtered QRS endpoints and points 30 msec before. Isopotential maps of the LPs showed distinct positive and negative regions. In 8 cases with MI, the extreme was related to the zones indicated by departure maps, and LP30 area maps also corresponded to the departure areas. Most importantly, the spatial distribution for the LP30 area map was different for each type of disease. In conclusion, body surface LP isopotential maps and LP30 area maps may provide useful information concerning the spatial distribution of LPs.

Arrhythmias, Cardiac↗
PubMed2004

NRT-based versus behavioral-based MAP: a comparison of parameters and speech perception in young children.

The present study was designed to evaluate the effect of neural response telemetry (NRT)-based cochlear implant (CI) programming versus behavioral-based programming on electrical stimulation parameters (MAP) threshold (T) and comfortable (C) levels and speech perception abilities in young children, during the first year of implant use. Ten congenitally deaf children at the age of 12-39 months (mean age: 25.2 months) implanted with the Nucleus 24R(CS) CI participated in the study. The group was randomly divided into two: (1) NRT-based MAP group (n = 5) consisted of children who were programmed using intra-operative NRT measurements; (2) behavioral-based MAP group (n = 5) consisted of children who were programmed using the behavioral responses of the patients. MAP parameters as well as sound-field aided thresholds and speech perception abilities were compared between the two groups at consecutive programming sessions: 1, 3, 6, and 12 months post initial stimulation. Results indicated no significant differences among NRT-based MAPs and behavioral-based MAPs. Although MAP profiles at initial stimulation differed in the apical region, these differences decreased with time. In addition, a gradual increase of T and C levels of NRT-based MAPs as well as those of behavioral-based MAPs was evident until the 1-month time point, thereafter stabilization occurred. Sound-field aided thresholds improved with time for both groups; however, they were found to be significantly better for the NRT-based MAP group. Despite these differences, speech perception abilities were comparable among groups at 12 months post initial stimulation. NRT-based programming was found to be significantly shorter than behavioral-based programming. In conclusion, for this small group of children, our findings support the use of NRT for programming of young children during the initial period after implantation.

Acoustic Stimulation↗
PubMed1987

Determination of the hypertrophic site of the left ventricle by body surface mapping in patients with hypertension.

To estimate the hypertrophic sites of the left ventricle by body surface mapping (MAP), we performed MAP in 55 patients with hypertension and compared the MAP data with echocardiographic findings. MAP data were analyzed using the departure map technique reported by Flowers et al. The mean and standard deviation (SD) of the normal control were obtained from 40 normal volunteers. We constructed departure maps at 20, 30, 40, 50 and 60 msec from the onset of the QRS. Each map indicates the area of abnormally increased potential outside the normal range at the time. Subjects were classified into 5 groups according to the appearance time of the abnormal positive area. Septal thickness was significantly increased in groups that had an abnormal positive area at 20 msec, and left ventricular posterior wall thickness was significantly increased in the groups that had an abnormal positive area at 60 msec. We postulate that the increased electrical potential due to hypertrophy of the interventricular septum is represented by the abnormal positive area at 20 msec, and the increased potential of the left ventricular posterior wall by the abnormal positive area at 60 msec. MAP, especially the departure map technique, is a useful method to detect the abnormal electrical potential distribution in patients with left ventricular hypertrophy.

Adult↗
PubMed1992

Quantitation of mapping uncertainty in Wolff-Parkinson-White syndrome. Implications for anatomic characterization and surgical division of accessory atrioventricular connections.

The purpose of this study was to quantitate the uncertainty inherent in the electrophysiologic mapping of ventricular preexcitation as seen in Wolff-Parkinson-White syndrome. An ink-coated needle electrode was constructed to serve as a point source of unipolar stimulation along the atrioventricular junction. Activation times for 11 ventricular mapping sites at the atrioventricular junction were measured for each stimulation point. Maps were successfully completed for 18 right free wall and 14 posterior septal stimulation points. The activation time at the mapping site closest to the stimulation point was termed the index activation time. Activation times identical to the index activation time were noted at 1.3 +/- 0.5 mapping sites for each free wall stimulation point and 1.9 +/- 0.9 mapping sites for each septal stimulation point (p < 0.05, septal versus free wall stimulation points). Activation times falling within 5 msec of the index activation time were noted at 2.4 +/- 1.0 mapping sites for each free wall stimulation point and at 3.9 +/- 1.4 mapping sites for each septal stimulation point (p < 0.05, septal versus free wall stimulation points). The uncertainty of electrophysiologic mapping can be quantitated, and this error should be considered when making inferences regarding the anatomy of accessory pathways based on electrophysiologic data. A knowledge of the uncertainty inherent in the localization of accessory atrioventricular connections by electrophysiologic mapping can be used to plan borders of surgical dissection that will account for this uncertainty at a 95% confidence level.

Animals↗
PubMedDate not supplied

[Heart potential mapping from the thoracic surface in healthy persons].

We have examined 56 normal subjects, 24 females and 32 males. We have calculated the average maps on the basis of 30 patients of the average age of 24.3 years (SD = 4.91). The aim of our studies was to settle the normal heart potentials mapping. The studies were realized in the Laboratory of Electrophysiology in the Department of Pathophysiology of Wrocław Medical Academy. In order to record the heart potential mapping we have used the HPM 7100 system (Fukuda Denshi). We have analyzed isopotential maps, isointegral maps and ventricular activation time maps. We have calculated the average maps using the information system "Heart-Map" Normal heart potential mapping are necessary for statistic analyzing of heart potentials mapping in patients suffering from the heart diseases.

Action Potentials↗
PubMed2005

Using concept mapping to develop a logic model for the Prevention Research Centers Program.

INTRODUCTION: Concept mapping is a structured conceptualization process that provides a visual representation of relationships among ideas. Concept mapping was used to develop a logic model for the Centers for Disease Control and Prevention's Prevention Research Centers Program, which has a large and diverse group of stakeholders throughout the United States. No published studies have used concept mapping to develop a logic model for a national program. METHODS: Two logic models were constructed using the data from the concept mapping process and program documents: one for the national level and one for the local level. Concept mapping involved three phases: 1) developing questions to generate ideas about the program's purpose and function, 2) gathering input from 145 national stakeholders and 135 local stakeholders and sorting ideas into themes, and 3) using multivariate statistical analyses to generate concept maps. Logic models were refined using feedback received from stakeholders at regional meetings and conferences and from a structured feedback tool. RESULTS: The national concept map consisted of 9 clusters with 88 statements; the local concept map consisted of 11 clusters with 75 statements. Clusters were categorized into three logic model components: inputs, activities, and outcomes. Based on feedback, two draft logic models were combined and finalized into one for the Prevention Research Centers Program. CONCLUSION: Concept mapping provides a valuable data source, establishes a common view of a program, and identifies inputs, activities, and outcomes in a logic model. Our concept mapping process resulted in a logic model that is meaningful for stakeholders, incorporates input from the program's partners, and establishes important program expectations. Our methods may be beneficial for other programs that are developing logic models for evaluation planning.

Cluster Analysis↗
PubMed1991

[A bull's eye subtraction polar map for assessing thallium redistribution (1). Comparison with quantitative redistribution].

A new bull's eye subtraction polar (BS) map has been developed for quantitative assessment of redistribution on stress-delayed thallium-201 SPECT studies. BS map was created after subtraction of a normalized stress bull's eye polar map from a normalized delayed polar map in 10 normal subjects and 33 patients with coronary artery disease to compare BS map with qualitative redistribution scores. The BS map showed less than 15% in all of the 50 segments in the normal subjects. Of 27 segments exhibiting persistent defect without redistribution, the BS map showed less than 10% in 20 segments (74%) and 10-15% in 6 segments (22%). On the other hand, of 34 segments exhibiting redistribution, the BS map showed greater than or equal to 15% in 25 segments (74%) and 10-15% in the remaining 9 segments (26%). Thus, significant redistribution was evident in the areas showing greater than or equal to 10-15% on the BS map. We conclude that the BS map is valuable for quantitative assessment of redistribution on stress-delayed thallium-201 SPECT imaging.

Adult↗
PubMedDate not supplied

Can the MAP technique be applied to study triggered activities of the heart? Intracellular evidence in vivo.

Monophasic action potential (MAP) recording with contact electrode has been applied to study triggered activities of the heart. Intracellular evidence in vivo, however, of the MAP technique is lacking. In the present study, transmembrane action potential (TAP) recorded with floating glass microelectrode was compared with MAP in 18 cat hearts in vivo. The results were as follows. 1) In control conditions, the MAP duration at 50 and 90% repolarization was similar to that of TAP without any significant difference. 2) 10 sec after CsCl (0.5 mM/kg, i.v.), early afterdepolarization (EAD) appeared in the middle-late period of phase 3 both in the MAP and TAP; 30 sec after CsCl, the amplitude of MAP-EAD was 3.4 +/- 1.3 mV and that of TAP-EAD was 25.6 +/- 9.3 mV. Delayed afterdepolarization (DAD) was also induced by CsCl in phase 4 of the MAP and TAP simultaneously. The amplitude of MAP-DAD was 3.3 +/- 0.6 mV and that of TAP-DAD was 13.0 +/- 5.3 mV. 3) Triggered arrhythmias, including premature ventricular beat and tachycardia, induced by CsCl repeated injection were observed in the MAP and TAP recording synchronously. The present study not only provides an intracellular and direct evidence in vivo but also suggests that the contact electrode MAP technique could be applied to study triggered activities of the heart in vivo.

Action Potentials↗