Transient Entrainment Research Articles

Synchronization of oscillatory growth prepares fungal hyphae for fusion.

Communication is crucial for organismic interactions, from bacteria, to fungi, to humans. Humans may use the visual sense to monitor the environment before starting acoustic interactions. In comparison, fungi, lacking a visual system, rely on a cell-to-cell dialogue based on secreted signaling molecules to coordinate cell fusion and establish hyphal networks. Within this dialogue, hyphae alternate between sending and receiving signals. This pattern can be visualized via the putative signaling protein Soft (SofT), and the mitogen-activated protein kinase MAK-2 (MakB) which are recruited in an alternating oscillatory manner to the respective cytoplasmic membrane or nuclei of interacting hyphae. Here, we show that signal oscillations already occur in single hyphae of Arthrobotrys flagrans in the absence of potential fusion partners (cell monologue). They were in the same phase as growth oscillations. In contrast to the anti-phasic oscillations observed during the cell dialogue, SofT and MakB displayed synchronized oscillations in phase during the monologue. Once two fusion partners came into each other's vicinity, their oscillation frequencies slowed down (entrainment phase) and transit into anti-phasic synchronization of the two cells' oscillations with frequencies of 104±28 s and 117±19 s, respectively. Single-cell oscillations, transient entrainment, and anti-phasic oscillations were reproduced by a mathematical model where nearby hyphae can absorb and secrete a limited molecular signaling component into a shared extracellular space. We show that intracellular Ca2+ concentrations oscillate in two approaching hyphae, and depletion of Ca2+ from the medium affected vesicle-driven extension of the hyphal tip, abolished the cell monologue and the anti-phasic synchronization of two hyphae. Our results suggest that single hyphae engage in a 'monologue' that may be used for exploration of the environment and can dynamically shift their extracellular signaling systems into a 'dialogue' to initiate hyphal fusion.

Transient Bedload Transport During Flashflood Bores in a Desert Gravel‐Bed Channel

AbstractEvidence of the effect of unsteady flow on bedload sediment transport is meager, particularly in desert rivers, despite its scientific, environmental and engineering importance. Our study of the phenomenon was conducted in Nahal Eshtemoa, Israel, an ephemeral river located in a semi‐arid area and subjected to flash floods. During 4 years, we monitored bedload transport and contemporaneous hydraulics, focusing on two intervals during which flow changed most rapidly: (a) the arrival of flood bores over dry river beds and (b) the propagation of subsequent bores over flowing water. Monitoring involved deployment of plate microphones, video cameras, surface velocity radar and a 3D velocimeter, enabling synchronized and unique data acquisition at high temporal resolution. We hypothesized that turbulence would be considerably elevated during the arrival of a flood bore and that this would induce transient entrainment of bedload. Our results demonstrate that bedload is indeed transported by the bore front and ceases soon after the arrival of most bores, even though water depth continues to rise. Bores arriving on a dry river bed usually generate higher bedload fluxes than bores advancing over flowing water. Elevated values of shear stress, turbulent kinetic energy and water‐surface slope occur as a bore impinges but then decrease. This is likely to be the explanation for high transient rates of bedload transport. Once the threshold depth previously determined as inducing continuous bedload motion is attained (≈40 cm), transport rates rise considerably relative to those associated with the bores.

Kinetics and prey capture by a paddling jellyfish: three-dimensional simulation and Lagrangian coherent structure analysis

Abstract

Ablation of scar-related reentrant atrial tachycardias with epi-to-endo bridging is less successful

Epicardial portions of the circuit of endocardial re-entrant tachycardias are well established phenomena in the ventricles, but little is known about a similar phenomenon in post lesion atrial tachycardia (AT). Higher spatial and voltage mapping capabilities may help identify extra-endocardial bridging (EEB) during tachycardia. We retrospectively analysed our database of 119 pts with AT cases with ultra-high density mapping between March 2015 and March 2018. Epi-to-endo breakthrough sites were diagnosed when endocardial activation started at a discrete point before spreading radially in every available direction. PPI after transient entrainment at these sites confirmed local participation in AT. In 20 out of the 119 pts (mean age 70 ± 9 yrs, always with ≥ 1 prior procedures), 2 types of EEB were found. Type 1 is a “myocardial” EEB ( n = 16). Subtype 1A ( Fig. 1 ) with a visible antidromic wavefront back to a line of block ( n = 10) whereas in subtype 1B activation starts immediately adjacent to a usually large line of block. Type 2 implied an extra-atrial “venous” bridging, either as a “shunt” over a line of block (subtype 2A, n = 6) or by using an epicardial vein as a major part of a circuit (subtype 2B, n = 1). In presence of EEB, AT termination was 17/22 (77%), significantly lower than our historical cohort of nonEEB AT (97%, P = 0.03). The most successful strategy was targeting epi-endo breakthrough site. Atrial EEB using either epicardial layers of the atrial wall, or extra-atrial venous structures is confirmed. Successful ablation at epi-to-endo breakthrough site proves the validity of the concept but results of ablation are inferior to nonEEB AT.

Productivity patterns in the equatorial Pacific over the last 30,000 years

AbstractThe equatorial Pacific traverses a number of productivity regimes, from the highly productive coastal upwelling along Peru to the near gyre‐like productivity lows along the international dateline, making it an ideal target for investigating how biogeochemical systems respond to changing oceanographic conditions over time. However, conflicting reconstructions of productivity during periods of rapid climate change, like the last deglaciation, render the spatiotemporal response of equatorial Pacific productivity ambiguous. In this study, surface productivity since the last glacial period (30,000 years ago) is reconstructed from seven cores near the Line Islands, central equatorial Pacific, and integrated with productivity records from across the equatorial Pacific. Three coherent deglacial patterns in productivity are identified: (1) a monotonic glacial‐Holocene increase in productivity, primarily along the Equator, associated with increasing nutrient concentrations over time; (2) a deglacial peak in productivity ~15,000 years ago due to transient entrainment of nutrient rich southern‐sourced deep waters; and (3) possible precessional cycles in productivity in the eastern equatorial Pacific that may be related to Intertropical Convergence Zone migration and potential interactions with El Niño–Southern Oscillation dynamics. These findings suggest that productivity was generally lower during the glacial period, a trend observed zonally across the equatorial Pacific, while deglacial peaks in productivity may be prominent only in the east.

Arrhythmogenic calmodulin mutations disrupt intracellular cardiomyocyte Ca2+ regulation by distinct mechanisms.

BackgroundCalmodulin (CaM) mutations have been identified recently in subjects with congenital long QT syndrome (LQTS) or catecholaminergic polymorphic ventricular tachycardia (CPVT), but the mechanisms responsible for these divergent arrhythmia‐susceptibility syndromes in this context are unknown. We tested the hypothesis that LQTS‐associated CaM mutants disrupt Ca2+ homeostasis in developing cardiomyocytes possibly by affecting either late Na current or Ca2+‐dependent inactivation of L‐type Ca2+ current.Methods and ResultsWe coexpressed CaM mutants with the human cardiac Na channel (NaV1.5) in tsA201 cells, and we used mammalian fetal ventricular cardiomyocytes to investigate LQTS‐ and CPVT‐associated CaM mutations (LQTS‐ and CPVT‐CaM). LQTS‐CaM mutants do not consistently affect L‐type Na current in heterologous cells or native cardiomyocytes, suggesting that the Na channel does not contribute to LQTS pathogenesis in the context of CaM mutations. LQTS‐CaM mutants (D96V, D130G, F142L) impaired Ca2+‐dependent inactivation, whereas the CPVT‐CaM mutant N54I had no effect on Ca2+‐dependent inactivation. LQTS‐CaM mutants led to loss of Ca2+‐transient entrainment with the rank order from greatest to least effect: CaM‐D130G~CaM‐D96V>>CaM‐F142L. This rank order follows measured Ca2+‐CaM affinities for wild‐type and mutant CaM. Acute isoproterenol restored entrainment for CaM‐130G and CaM‐D96V but caused irreversible cytosolic Ca2+ overload for cells expressing a CPVT‐CaM mutant.ConclusionsCaM mutations associated with LQTS may not affect L‐type Na+ current but may evoke defective Ca2+‐dependent inactivation of L‐type Ca2+ current.

Overdrive pacing from downstream sites on multielectrode catheters to rapidly detect fusion and to diagnose macroreentrant atrial arrhythmias.

Entrainment criteria for macroreentrant arrhythmias are based on detecting fusion between tachycardia and paced wavefronts, but this is often difficult for atrial tachycardias (AT) after ablation of atrial fibrillation. With the use of a multipolar catheter, pacing was performed from electrodes within the coronary sinus showing activation later than adjacent electrodes (downstream overdrive pacing) during 66 ATs in 62 patients: 20 cavotricuspid isthmus-dependent ATs, 20 perimitral ATs, 13 focal ATs with sequential coronary sinus activation, and 13 other macroreentrant left atrial ATs. The paced cycle length was 10 to 30 milliseconds below the tachycardia cycle length (TCL), and activation at the neighboring upstream electrodes was assessed. Downstream overdrive pacing at 48 sites close to a macroreentrant circuit (PPI-TCL <40 milliseconds, where PPI is postpacing interval) produced constant fusion demonstrated by a long stimulus to upstream atrial electrogram interval (S-Au) >75% TCL and was consistent with orthodromic activation of the upstream site despite its close proximity to the pacing site. In contrast, downstream overdrive pacing at 18 sites during focal AT or remote from the macroreentrant AT circuit (PPI-TCL >40 milliseconds) always demonstrated a comparatively short S-Au <25% of TCL (12±4% versus 89±4% of TCL; P<0.001), consistent with direct activation. Selection of a downstream activation site for overdrive pacing can facilitate rapid recognition of macroreentry and proximity to the reentry circuit using a single multielectrode catheter by recognizing a PPI-TCL <40 milliseconds and S-Au >75% of TCL. Recognition of intracardiac constant fusion with this method is a novel criterion for transient entrainment.

The effect of transient conditions on synovial fluid protein aggregation lubrication

Little is known about the prevailing lubrication mechanisms in artificial articular joints and the way in which these mechanisms determine implant performance. The authors propose that interfacial film formation is determined by rheological changes local to the contact and is driven by aggregation of synovial fluid proteins within the contact inlet region. A direct relationship between contact film thickness and size of the protein aggregation within the inlet region has been observed.In this paper the latest experimental observations of the protein aggregation mechanism are presented for conditions which more closely mimic joint kinematics and loading. Lubricant films were measured for a series of bovine calf serum solutions for CoCrMo femoral component sliding against a glass disc. An optical interferometric apparatus was employed to study the effects of transient motion on lubricant film formation. Central film thickness was measured as a function of time for a series of transient entrainment conditions; start-up motion, steady-state and non-steady-state uni-directional sliding, and bi-directional sliding. The size of the inlet aggregations was found to be dependent upon the type of transient condition. Thick protective protein films were observed to build up within the main contact region for all uni-directional tests. In contrast the inlet aggregation was not observed for bi-directional tests. Contact film thickness and wear was found to be directly proportional to the presence of the inlet protein phase. The inlet phase and contact films were found to be fragile when disrupted by surface scratches or subjected to reversal of the sliding direction.

Non-24-Hour Disorder in Blind Individuals Revisited: Variability and the Influence of Environmental Time Cues

To assess the interindividual and intraindividual variability in the circadian rhythms of blind individuals with non-24-h disorder and to quantify the influence of environmental time cues in blind subjects lacking entrainment (non-24-h individuals or N-24s). An observational study of 21 N-24s (11 females and 10 males, age 9-78 years) who kept a sleep/wake schedule of their choosing. Circadian phase was determined using the melatonin onset (MO) from plasma or saliva samples that were collected every 2 weeks. Melatonin concentrations were measured by radioimmunoassay. A total of 469 MO assessments were conducted over 5,536 days of study. The rate of drift of circadian phase was calculated using a series of MOs (total number of hours the MO drifted divided by the total number of days studied). Stability of the rest/activity rhythm was calculated using chi-squared periodogram analysis of wrist actigraphy data in 19 subjects. Academic medical center. Paid volunteers. N/A. Subjects lacked entrainment such that circadian phase drifted an average (± standard deviation) of 0.39 ± 0.29 h later per day; however, there was notable intersubject and intrasubject variability in the rate of drift including relative coordination and periods of transient entrainment during which there was little to no drift in the circadian phase. A regular, reproducible, and significant oscillation in the rate of drift was detected in 14 of the 21 subjects. A significant non-24-h rest/activity rhythm was detected in 18 of 19 subjects. There was a strong correlation (r = 0.793, P = 0.0001) between the non-24-h rest/activity rhythm and the rate of drift of the circadian phase. Most N-24s are influenced by unidentified environmental time cues and the non-entrained biological clock in such N-24s is reflected in their rest/activity rhythms. These findings may have diagnostic and treatment implications: this disorder might be diagnosed with actigraphy alone, relative coordination and transient entrainment may result in misdiagnosis and responsiveness to environmental time cues may influence treatment success with oral melatonin. Emens JS; Laurie AL; Songer JB; Lewy AJ. Non-24-hour disorder in blind individuals revisited: variability and the influence of environmental time cues. SLEEP 2013;36(7):1091-1100.

Atrioventricular Nodal Reentrant Tachycardia

Atrioventricular nodal reentrant tachycardia (AVNRT) represents the most common regular supraventricular arrhythmia in humans.1 The precise anatomic site and nature of the pathways involved have not yet been established, and several attempts to provide a reasonable hypothesis based on anatomic or anisotropic models have been made.2 There has been considerable evidence that the right and left inferior extensions of the human atrioventricular (AV) node and the atrionodal inputs they facilitate may provide the anatomic substrate of the slow pathway, and a comprehensive model of the tachycardia circuit for all forms of AVNRT based on the concept of atrionodal inputs has been proposed.2 Still, however, the circuit of AVNRT remains elusive. Recently, time-honored conventional schemes for the diagnosis and classification of the various forms of the arrhythmia have been refuted in part by evolving evidence. Recognition of the various types of AVNRT is important, however, to expedite diagnosis and allow implementation of appropriate ablation therapy without complications. We present an update on AVNRT with a particular emphasis on electrophysiological criteria used for the differential diagnosis of regular, supraventricular tachycardias. Typically, AVNRT is a narrow-complex tachycardia, ie, QRS duration <120 ms, unless aberrant conduction, which is usually of the right bundle-branch type, or a previous conduction defect exists. Tachycardia-related ST depression and RR-interval variation may be seen. RR alternans in AVNRT has been attributed to the proposed model of a figure of 8 reentry with continuous crossing over of antegrade activation through an inferior input to the contralateral superior input via the node.2 In the typical form of AVNRT (slow-fast), abnormal (retrograde) P′ waves are constantly related to the QRS and in the majority of cases are indiscernible or very close to the QRS complex (RP′/RR <0.5). Thus, P′ waves are either masked by the QRS complex or …

Assessment of Clockwise Cavotricuspid Isthmus Block Based on Conduction Times during Transient Entrainment: A Prospective Study

In typical counterclockwise atrial flutter (AFL), the route of impulse propagation to anteroinferior right atrium (AIRA) during transient entrainment (TE) from the coronary sinus (CS) is expected to be similar to that during pacing from the same CS site during sinus rhythm (SR) when cavotricuspid isthmus (CTI) block has occurred. This could be used to identify CTI block during ablation procedures. Thirty-six patients with AFL (cycle length [CL], 240 +/- 25 ms) underwent CTI ablation during AFL. CS pacing was performed at a CL of 20 ms less than AFL CL before ablation (n = 36), and at several CL during SR with conduction through the CTI (n = 21) and after CTI block (n = 36). TE with orthodromic activation of AIRA occurred in all 36 patients. Conduction time from CS to AIRA during TE (T-entr, 199 +/- 29 ms) was significantly longer than during pacing in SR (T-CTI) at the same rate not only with CTI conduction (T-CTI-C, 135 +/- 24 ms, P < 0.001), but also with CTI block (T-CTI-B, 186 +/- 24 ms, P < 0.01). T-entr did not correlate with T-CTI-C, but there was an excellent correlation between T-entr and T-CTI-B (r = 0.874, P < 0.001). A "TE index" that corrected T-CTI for individual T-entr identified CTI block with 97% sensitivity and 91% specificity. T-CTI at low rates differed from T-CTI at high rates but correlated significantly with them. Comparison of conduction times during TE from the CS and during pacing from the same site and rate in SR can help to establish whether clockwise CTI block has been achieved in patients with typical AFL.

Two Steady‐Entrainment Phases and Graded Masking Effects by Light Generate Different Circadian Chronotypes in Octodon degus

Processes involved in the operation of the circadian pacemaker are well characterized; however; little is known about what mechanisms drive the overt diurnal, nocturnal, or crepuscular behavior in a species. In this context, dual‐phasing rodents, such as Octodon degus, emerge as a useful model to decipher these keys. Two main chronotypes, nocturnal and diurnal, have been traditionally described in laboratory‐housed degus based on the percentage of activity displayed by the animals during the scotophase or photophase. However, if one considers also the entrainment phase angle during the first days following a change from LD to DD conditions, a third chronotype (intermediate)—or more properly, a continuous grading of circadian expressions between diurnal and nocturnal chronotype—can be observed. Our experiments suggest the pacemaker of the diurnal animal is entrained to the photophase, and light does not exert a negative masking effect. The pacemaker of the nocturnal degus, on the other hand, is entrained to the scotophase, and light exerts a strong negative masking effect. Finally, the intermediate chronotype is characterized by variable negative masking effect of light overlapping a pacemaker entrained to the photophase. The phase shift inversion from diurnal to nocturnal chronotype is related to the availability of a wheel in the cage, and the effect may be located downstream from the clock. However, body temperature rhythm recordings, less affected by masking effects, point to an involvement of the circadian pacemaker in chronotype differentiation, as transient entrainment cycles, and not an abrupt phase shift, were detected after providing access to the wheel. The diurnality of degus seems to be the result of a variety of mechanisms, which may explain how different processes can lead to similar chronotypes.

Successful catheter ablation of a ventricular tachycardia storm originating from the left ventricular posterior papillary muscle involved with a remote myocardial infarction

A 61-year-old man with a remote posterior myocardial infarction underwent electrophysiological testing for a ventricular tachycardia (VT) storm. Repeated cardioversions terminated the VT with immediate resumption after one sinus beat. Pacing neither terminated the VT nor demonstrated transient entrainment. Echocardiographically guided electroanatomic mapping revealed a centrifugal activation from the septal mid-apical region of the left ventricle on the septal portion of the posterior papillary muscle where a high frequency potential was observed within the local ventricular electrogram. Irrigated radiofrequency current at this site eliminated the VT. This case suggested that papillary muscles may be a target for catheter ablation of electrical storms after myocardial infarctions.

Successful Radiofrequency Catheter Ablation of Ventricular Tachycardia Originating from Underneath the Mechanical Prosthetic Aortic Valve

A 67-year-old man who developed sustained ventricular tachycardia (VT) 4 years after a prosthetic aortic valve replacement, underwent electrophysiologic testing and catheter ablation. The mechanism of the VT was suggested to be triggered activity because the VT could be induced by programmed ventricular stimulation, and burst ventricular pacing demonstrated overdrive suppression without a transient entrainment. Successful catheter ablation using a transseptal approach was achieved underneath the mechanical prosthetic aortic valve on the blind side for that approach. This case demonstrated that catheter mapping and ablation of the entire LV using a transseptal approach might be possible.

Ventricular Tachycardia Originating From the Posterior Papillary Muscle in the Left Ventricle

Background— Several distinct forms of focal ventricular tachycardia (VT) from the left ventricle (LV) have been described. We report a new syndrome of VT arising from the base of the posterior papillary muscle in the LV. Methods and Results— Among 290 consecutive patients who underwent ablation for VT or symptomatic premature ventricular complexes (PVCs) based on a focal mechanism, 7 patients were found to have an ablation site at the base of the posterior papillary muscle in the LV. All patients had normal LV systolic function and a normal baseline electrocardiogram. The electrocardiogram during VT or PVCs demonstrated a right bundle-branch block and superior-axis QRS morphology in all patients. VT was not inducible by programmed atrial or ventricular stimulation. In 2 patients with sustained VT, overdrive pacing neither terminated VT nor demonstrated any criterion for transient entrainment. Activation mapping localized the earliest site of activation to the base of the posterior papillary muscle in all patients. When Purkinje potentials were recorded at the site of successful ablation, these potentials preceded local ventricular muscle potentials during sinus rhythm. During VT or PVCs, however, the ventricular muscle potential always preceded the Purkinje potentials. After recurrence of VT or PVCs with standard radiofrequency ablation, irrigated ablation was successful in eliminating the arrhythmia in all patients. Over a mean follow-up period of 9 months, all patients have been free of PVCs and VT. Conclusion— We present a distinct syndrome of VT arising from the base of the posterior papillary muscle in the LV by a nonreentrant mechanism. Ablation can be challenging, and irrigated ablation may be necessary for long-term success.

Macroreentrant atrial tachycardia: Pathophysiological concepts

C T T hich n role i the r trial t key f r arc a ial p ved a req e of t cuit h p well d ded b c p H a ntroduction he term macroreentrant atrial tachycardia (MRAT) i echanistic way of categorizing an arrhythmia indep ently of its electrocardiogram (ECG) characteristics. 1 Alhough the ECG aspect of this arrhythmia is most frequ hat of a flutter (no return to baseline in at least one l an be that of an atrial tachycardia (return to baseline eads) especially in the case of a diseased heart. By d ion, the requirements for an atrial macroreentry to occu large circuit, an area of slow conduction, and a zo nidirectional block. In the atria, these requirements pontaneously determined by anatomical structures such ulmonary venous ostia or tricuspid or mitral rings o reas of electrical disturbances induced by cardiac surg y previous ablation, or spontaneously. Identification of a reentrant arrhythmia is based on rophysiological characteristics. In the presence of RAT, transient entrainment is always possible, and trial activation covering the entire cycle almost always e recorded. After the last entrained beat, a postpa nterval within 20 ms of the tachycardia cycle length ifies the pacing site as a site inside the circuit. Contr icroreentry, macroreentry is confirmed if exact return les are recorded from at least two atrial sites separate t least 2 cm. Before ablation of MRAT, identification rotected isthmus inside the circuit can be crucial sinc s usually the target site. A protected isthmus is iden f pacing slightly faster than the tachycardia rate d red at that site produces concealed entrainment, tha ndocardial atrial activation sequence and surface aves identical to those observed during spontane achycardia (Figure 1) . In addition, the interval betw he spike of stimulation and the surface P wave d acing should be identical to the interval between the lectrogram and the surface P wave site during tachyca ll of these electrophysiologic characteristics are requi o identify a protected isthmus.

Another Way to Prove the Presence and Participation of an Accessory Pathway in Supraventricular Tachycardia?

Another Way to Prove the Presence and Participation of an Accessory Pathway in Supraventricular Tachycardia?

P3-76: A prospective study to assess clockwise cavotricuspid isthmus block based on conduction times during transient entrainment

P3-76: A prospective study to assess clockwise cavotricuspid isthmus block based on conduction times during transient entrainment

First postpacing interval after tachycardia entrainment with correction for atrioventricular node delay: A simple maneuver for differential diagnosis of atrioventricular nodal reentrant tachycardias versus orthodromic reciprocating tachycardias

The difference between the first postpacing interval (PPI) after tachycardia entrainment from the right ventricular apex and the tachycardia cycle length (TCL) can be used as an index of proximity to the circuit. The purpose of this study was to determine whether the response to entrainment of tachycardia during ventricular stimulation with correction for AV node delay is a useful, simple maneuver for differentiating AV nodal reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) using a concealed accessory pathway. The study consisted of 193 consecutive patients who underwent electrophysiologic study and ablation of regular paroxysmal supraventricular tachycardia without preexcitation during sinus rhythm. Tachycardia entrainment was attempted through trains of 5 to 15 right ventricular apex pacing pulses. The increment in AV nodal conduction time in the first PPI was subtracted from the PPI-TCL difference (corrected PPI-TCL). Electrophysiologic study demonstrated ORT in 84 patients and AVNRT in 109 patients. Transient entrainment was achieved in all but 12 patients. The mean corrected PPI-TCL difference was significantly shorter in 77 patients with ORT (66 +/- 27 ms) than in 104 AVNRT patients (151 +/- 28 ms; P <.0001). Patients with septal accessory pathways had shorter corrected PPI-TCL differences than patients with free-wall accessory pathways. The presence of a corrected PPI-TCL difference <110 ms identified all but one patient with ORT, and no patients with AVNRT had such a difference. The return cycle after tachycardia entrainment by right ventricular apex stimulation with correction for AV node delay is a rapid, useful maneuver for differential diagnosis of AVNRT vs ORT in patients without preexcitation. The presence of a corrected PPI-TCL <110 ms accurately identified with high reliability those patients with ORT.

Left Atrionodal Connections in Typical and Atypical Atrioventricular Nodal Reentrant Tachycardias: Activation Sequence in the Coronary Sinus and Results of Radiofrequency Catheter Ablation

The presence of atrionodal connections and coronary sinus (CS) breakthrough in atrioventricular nodal reentrant tachycardia (AVNRT) has been suggested. However, the incidence, anatomic relationship with reentrant circuit, and results of catheter ablation are unknown. Fifty-two patients with typical slow/fast AVNRT and 10 patients with atypical slow/intermediate or fast/slow AVNRT were included. Eccentric activation of the CS (EACS) was observed in 3 of 52 patients with typical and 8 of 10 patients with atypical AVNRT. The earliest CS activation in patients with an EACS was recorded at a site 10-20 mm inside the CS ostium. The postpacing interval after transient entrainment at the proximal CS in patients with EACS was 23 +/- 21 msec longer than the pacing cycle length. Modification or ablation of the slow pathway was successful in all patients with typical slow/fast AVNRT and in 7 of 9 patients with atypical AVNRT by RF energy delivered at the right septal tricuspid annulus (TA). In 2 patients with atypical AVNRT and an EACS, RF delivery inside the CS targeting the earliest CS activation eliminated the sustained AVNRT. Eccentric coronary sinus activation is observed in some rare cases of typical AVNRT, and in a majority of atypical AVNRT. Entrainment results suggest that the proximal coronary sinus may be part of the reentrant circuit. RF ablation of atypical AVNRT, if it fails from the standard right-side approach, can be targeted at the site of earliest retrograde atrial activation inside the CS.