Retrospective Window of Interest Annotation Provides New Insights Into Functional Channels in Ventricular Tachycardia Substrate.

BACKGROUND: Accurate annotation of local activation time is crucial in the functional assessment of ventricular tachycardia (VT) substrate. A major limitation of modern mapping systems is the standard prospective window of interest (sWOI) is limited to 490 to 500 milliseconds, preventing annotation of very late potentials (LPs). A novel retrospective window of interest (rWOI), which allows annotation of all diastolic potentials, was used to assess the functional VT substrate. OBJECTIVES: This study sought to investigate the utility of a novel rWOI, which allows accurate visualization and annotation of all LPs during VT substrate mapping. METHODS: Patients with high-density VT substrate maps and a defined isthmus were included. All electrograms were manually annotated to latest activation using a novel rWOI. Reannotated substrate maps were correlated to critical sites, with areas of late activation examined. Propagation patterns were examined to assess the functional aspects of the VT substrate. RESULTS: Forty-eight cases were identified with 1,820 ± 826 points per map. Using the novel rWOI, 31 maps (65%) demonstrated LPs beyond the sWOI limit. Two distinct patterns of channel activation were seen during substrate mapping: 1) functional block with unidirectional conduction into the channel (76%); and 2) wave front collision within the channel (24%). In addition, a novel marker termed the zone of early and late crowding was studied in the rWOI substrate maps and found to have a higher positive predictive value (85%) than traditional deceleration zones (69%) for detecting critical sites of re-entry. CONCLUSIONS: The standard WOI of contemporary mapping systems is arbitrarily limited and results in important very late potentials being excluded from annotation. Future versions of electroanatomical mapping systems should provide longer WOIs for accurate local activation time annotation.

The impact of coffee subtypes on incident cardiovascular disease, arrhythmias, and mortality: long-term outcomes from the UK Biobank.

AIMS: Epidemiological studies report the beneficial effects of habitual coffee consumption on incident arrhythmia, cardiovascular disease (CVD), and mortality. However, the impact of different coffee preparations on cardiovascular outcomes and survival is largely unknown. The aim of this study was to evaluate associations between coffee subtypes on incident outcomes, utilizing the UK Biobank. METHODS AND RESULTS: Coffee subtypes were defined as decaffeinated, ground, and instant, then divided into 0, <1, 1, 2-3, 4-5, and >5 cups/day, and compared with non-drinkers. Cardiovascular disease included coronary heart disease, cardiac failure, and ischaemic stroke. Cox regression modelling with hazard ratios (HRs) assessed associations with incident arrhythmia, CVD, and mortality. Outcomes were determined through ICD codes and death records. A total of 449 563 participants (median 58 years, 55.3% females) were followed over 12.5 ± 0.7 years. Ground and instant coffee consumption was associated with a significant reduction in arrhythmia at 1-5 cups/day but not for decaffeinated coffee. The lowest risk was 4-5 cups/day for ground coffee [HR 0.83, confidence interval (CI) 0.76-0.91, P < 0.0001] and 2-3 cups/day for instant coffee (HR 0.88, CI 0.85-0.92, P < 0.0001). All coffee subtypes were associated with a reduction in incident CVD (the lowest risk was 2-3 cups/day for decaffeinated, P = 0.0093; ground, P < 0.0001; and instant coffee, P < 0.0001) vs. non-drinkers. All-cause mortality was significantly reduced for all coffee subtypes, with the greatest risk reduction seen with 2-3 cups/day for decaffeinated (HR 0.86, CI 0.81-0.91, P < 0.0001); ground (HR 0.73, CI 0.69-0.78, P < 0.0001); and instant coffee (HR 0.89, CI 0.86-0.93, P < 0.0001). CONCLUSION: Decaffeinated, ground, and instant coffee, particularly at 2-3 cups/day, were associated with significant reductions in incident CVD and mortality. Ground and instant but not decaffeinated coffee was associated with reduced arrhythmia.

Exploring environmental selection on genome size in angiosperms.

Angiosperms show a remarkable range in genome size (GS), yet most species have small genomes, despite the frequency of polyploidy and repeat amplification in the ancestries of most lineages. It has been suggested that larger genomes incur costs that have driven selection for GS reduction, although the nature of these costs and how they might impact selection remain unclear. We explore potential costs of increased GS encompassing impacts on minimum cell size with consequences for photosynthesis and water-use efficiency and effects of greater nitrogen and phosphorus demands of the nucleus leading to more severe trade-offs with photosynthesis. We suggest that nutrient-, water-, and/or CO2-stressed conditions might favour species with smaller genomes, with implications for species' ecological and evolutionary dynamics.

Extensive right atrial free wall low-voltage zone as the substrate for atrial fibrillation: successful ablation by scar homogenization.

AIMS: Prior studies have described a variety of mechanisms for atrial fibrillation (AF) originating in the right atrium (RA). In this study, we report a series of patients in whom an extensive right atrial free wall low-voltage zone (LVZ) served as the AF substrate. METHODS AND RESULTS: Five patients with a clinical syndrome of paroxysmal AF and atrial tachycardia (AT) underwent electrophysiologic evaluation. Five patients (3 M; age 52 ± 7 years) had symptomatic paroxysmal AF for (28 ± 17 months) not responsive to medical therapy. At the initial EP study, AT was inducible in four patients and was spontaneous in one patient. In all patients, tachycardia instability precluded detailed AT mapping. Sinus or pace maps indicated an extensive LVZ in the lateral RA trabeculated free wall which consisted of regions of low amplitude complex signals interspersed between electrically silent areas. Radiofrequency ablation aimed at rendering the LVZ electrical inert was successful in eliminating AF in four of five patients. At a follow-up of 28 ± 15 months, one patient had an isolated recurrence of AF. However, two patients required repeat ablation for recurrent AT. CONCLUSION: An extensive LVZ in the trabeculated RA free wall constitutes an unusual substrate for AF. These patients also demonstrate unstable ATs originating from the same zone. Radiofrequency ablation to render the low-voltage zone electrically inert is an effective strategy to manage AF and AT.

Position Statement on the Management of Cardiac Electrophysiology and Cardiac Implantable Electronic Devices in Australia During the COVID-19 Pandemic: A Living Document.

The COVID-19 pandemic poses a significant stress on health resources in Australia. The Heart Rhythm Council of the Cardiac Society of Australia and New Zealand aims to provide a framework for efficient resource utilisation balanced with competing risks when appropriately treating patients with cardiac arrhythmias. This document provides practical recommendations for the electrophysiology (EP) and cardiac implantable electronic devices (CIED) services in Australia. The document will be updated regularly as new evidence and knowledge is gained with time.

Dynamic Atrial Substrate During High-Density Mapping of Paroxysmal and Persistent AF: Implications for Substrate Ablation.

OBJECTIVES: This study sought to determine the impact of rate and direction on left atrial (LA) substrate. BACKGROUND: The extent to which substrate mapped in sinus rhythm varies according to cycle length and direction of wave front propagation is unknown. METHODS: A total of 73 consecutive patients with atrial fibrillation (AF) underwent electroanatomic LA mapping before pulmonary vein isolation using multipolar catheter during distal coronary sinus (CS) pacing at 600 ms and 300 ms. Additional maps were created during left superior pulmonary vein pacing at 300 ms. Bipolar voltage, conduction velocity (CV), and complex signals were determined. RESULTS: Mean age was 61 ± 9 years, 67% were men, and 53% had persistent AF. Global mean voltage was lower with CS pacing at 300 ms compared with 600 ms (1.56 ± 0.47 mV vs. 1.74 ± 0.48 mV; p < 0.001). This was seen in all LA segments. Global CV was reduced (30.4 ± 13.0 cm/s vs. 38.6 ± 14.0 cm/s; p < 0.001) with greater complex signals at 300 ms (8.9% vs. 5.3%; p < 0.005). Compared with CS pacing, left superior pulmonary vein pacing demonstrated highly regional changes with decreased voltage (1.04 ± 0.43 mV vs. 1.47 ± 0.53 mV; p = 0.01) and CV (24.4 ± 13.0 cm/s vs. 39.9 ± 16.6 cm/s; p = 0.008), and greater complex signals posteriorly. Longer AF duration in paroxysmal AF (p = 0.02) and shorter duration in persistent AF (p = 0.015) and left ventricular ejection fraction (p = 0.016) were independent predictors of voltage change. CONCLUSIONS: In patients with AF, variation in cycle length and direction of wave front activation produce both generalized and regional changes in voltage, CV, and complex fractionation, resulting in significant changes in substrate maps. This study highlights the potential limitations of static low-voltage maps to identify the AF ablation target zone.

Moderate alcohol consumption is associated with atrial electrical and structural changes: Insights from high-density left atrial electroanatomic mapping.

BACKGROUND: Regular alcohol intake is an important modifiable risk factor associated with atrial fibrillation (AF) and left atrial (LA) dilation. OBJECTIVE: The purpose of this study was to determine the impact of different degrees of alcohol consumption on atrial remodeling using high-density electroanatomic mapping. METHODS: We enrolled 75 patients before AF ablation to undergo high-density LA mapping (CARTO, Biosense Webster) using a multipolar catheter. The Confidense algorithm was used to create maps during distal coronary sinus pacing at 600 ms. Bipolar voltage and complex atrial activity were assessed, and isochronal activation maps were created to determine global conduction velocity (CV). Patients were classified as lifelong nondrinkers, mild drinkers (2-7 drinks/week), or moderate drinkers (8-21 drinks/week). RESULTS: High-density electroanatomic mapping (mean 1016 ± 445 points per patient) was performed on 25 lifelong nondrinkers, 25 mild drinkers (4.4 ± 2.3 drinks/week), and 25 moderate drinkers (14.0 ± 4.2 drinks/week). Moderate drinkers had significantly lower mean global bipolar voltages (1.53 ± 0.62 mV vs 1.89 ± 0.45 mV; P = .02), slower CV (33.5 ± 14.4 cm/s vs 41.7 ± 12.1 cm/s; P = .04), and a higher proportion of complex atrial potentials (7.8% ± 4.7% vs 4.5% ± 2.7%; P = .004) compared to nondrinkers. Global voltage and CV did not differ significantly in mild drinkers, but there was a significant increase in global complex potentials (6.6% ± 4.6%; P = .04) and regional low-voltage zones (<0.5 mV) in the septum and lateral wall (P <.05) compared with nondrinkers. CONCLUSION: Regular moderate alcohol consumption, but not mild consumption, is an important modifiable risk factor for AF associated with lower atrial voltage and conduction slowing. These electrical and structural changes may explain the propensity to AF in regular drinkers.

Isolation of the posterior left atrium for patients with persistent atrial fibrillation: routine adenosine challenge for dormant posterior left atrial conduction improves long-term outcome.

AIMS: Catheter ablation to achieve posterior left atrial wall (PW) isolation may be performed as an adjunct to pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (AF). We aimed to determine whether routine adenosine challenge for dormant posterior wall conduction improved long-term outcome. METHODS AND RESULTS: A total of 161 patients with persistent AF (mean age 59 ± 9 years, AF duration 6 ± 5 years) underwent catheter ablation involving circumferential PVI followed by PW isolation. Posterior left atrial wall isolation was performed with a roof and inferior wall line with the endpoint of bidirectional block. In 54 patients, adenosine 15 mg was sequentially administered to assess reconnection of the pulmonary veins and PW. Sites of transient reconnection were ablated and adenosine was repeated until no further reconnection was present. Holter monitoring was performed at 6 and 12 months to assess for arrhythmia recurrence. Posterior left atrial wall isolation was successfully achieved in 91% of 161 patients (procedure duration 191 ± 49 min, mean RF time 40 ± 19 min). Adenosine-induced reconnection of the PW was demonstrated in 17%. The single procedure freedom from recurrent atrial arrhythmia was superior in the adenosine challenge group (65%) vs. no adenosine challenge (40%, P < 0.01) at a mean follow-up of 19 ± 8 months. After multiple procedures, there was significantly improved freedom from AF between patients with vs. without adenosine PW challenge (85 vs. 65%, P = 0.01). CONCLUSION: Posterior left atrial wall isolation in addition to PVI is a readily achievable ablation strategy in patients with persistent AF. Routine adenosine challenge for dormant posterior wall conduction was associated with an improvement in the success of catheter ablation for persistent AF.

High Incidence of Low Catheter-Tissue Contact Force at the Cavotricuspid Isthmus During Catheter Ablation of Atrial Flutter: Implications for Achieving Isthmus Block.

INTRODUCTION: Recurrent atrial flutter following cavotricuspid isthmus (CTI) ablation remains a significant problem. The prevalence of low contact force (CF) during CTI ablation using standard tools is unknown. Our aim was to characterize the prevalence of low CF applications when experienced operators performed CTI ablation using "traditional" markers of contact blinded to CF measurements. METHODS AND RESULTS: Average CF (grams, g) and force-time integral (FTI) was analyzed in 458 lesions in 17 patients undergoing CTI ablation. The isthmus was divided into the annular, mid and caval segments for region-specific analysis. Despite "good" contact using traditional markers, there was significant variability in CF within each isthmus segment (e.g., annular CTI 1-57 g). A high proportion of lesions had a CF <10 g (40%). Lowest CF was the annular (median 9 g), followed by the mid (12 g) and the caval CTI (18 g, P < 0.001). Sites of acute CTI re-connection had a lower average CF and FTI than nonreconnected sites (P < 0.05). Each 1 g increase in CF was associated with a 16% reduction in risk of recovered CTI conduction (95% confidence interval: 4-27%, P = 0.01). CONCLUSION: Use of surrogate markers of "good contact" during ablation by experienced operators in the absence of real-time CF sensing resulted in nearly half of all lesions being delivered with low CF with marked region-specific variability in CF. Low CF was implicated in longer time to achieve conduction block and increased risk of acute reconnection. These findings underscore the importance of real-time CF measurements for optimizing ablation of typical atrial flutter.

The transesophageal echo probe may contribute to esophageal injury after catheter ablation for paroxysmal atrial fibrillation under general anesthesia: a preliminary observation.

INTRODUCTION: The transesophageal echo probe (TEE) is commonly used before and during atrial fibrillation (AF) ablation under general anesthesia (GA). We sought to determine the potential contribution of the TEE probe to esophageal injury after pulmonary vein isolation (PVI) alone for paroxysmal AF. METHODS AND RESULTS: Seventy-six patients undergoing PVI with TEE, PVI/TEE, 16 undergoing PVI without TEE (PVI/No TEE), and 27 undergoing TEE without any left atrial ablation (TEE/No LA ablation) under GA were included. Posterior wall ablation was power (20-25 W) and time limited (electrogram attenuation or ≤30 s). Esophageal capsule endoscopy (n = 206) was performed pre- and post-procedure and at 2 weeks. Esophageal lesions were seen in 30% of PVI/TEE, 0% of patients in the PVI/No TEE (P = 0.009), and 22% of TEE/No LA ablation groups (P = 0.47 vs. PVI/TEE). There were no instances of esophageal bleeding, perforation, or need for gastrointestinal intervention. Self-resolving dysphagia was the only reported symptom (5%). All lesions healed within 2 weeks. There was no significant difference in the location or morphological appearance of esophageal lesions seen in the PVI/TEE versus TEE/No LA ablation groups. CONCLUSIONS: Esophageal lesions were seen in 30% of patients undergoing PVI alone under GA with use of TEE and in a similar proportion (22%) of patients undergoing TEE in the absence of left atrial ablation. This study makes the preliminary observation that one must be cognizant of the TEE probe as a potential contributor to esophageal injury after AF ablation. Larger studies are needed to confirm these findings.

Left septal atrial tachycardias: electrocardiographic and electrophysiologic characterization of a paraseptal focus.

OBJECTIVE: The objective was to characterize the electrocardiographic and electrophysiological features of focal atrial tachycardia (FAT) originating from the left septum (LS). BACKGROUND: FAT is recognized to occur at predefined anatomic locations rather than randomly throughout the atria. We describe the ECG and EP features of ATs originating from the LS as an important site for apparent perinodal tachycardias. METHODS: Nine patients presenting with LS FAT from a consecutive series of 384 underwent EP/RFA for symptomatic FAT. RESULTS: The mean age was 56 ± 12 years; 7 female with symptoms for 36 ± 28 months. P wave morphology (PWM) was negative/positive in lead V1 and across the precordial leads and negative or negative/positive in inferior leads in all patients. Tachycardia was incessant in 6 out of 9 patients with a mean tachycardia cycle length 421 ± 56 milliseconds. His A was ahead of P wave in all patients (mean -15 ± 5 milliseconds) and earlier than CS proximal (mean 4 ± 9 milliseconds). Successful acute focal ablation achieved at a mean of 31 ± 12 milliseconds ahead of P wave with no recurrences at a mean follow-up of 30 ± 28 months. CONCLUSION: Although the left septum is an uncommon site for focal AT an awareness of this location for harboring foci is particularly important when mapping apparently right-sided septal tachycardias.

Right atrial remodeling is more advanced in patients with atrial flutter than with atrial fibrillation.

INTRODUCTION: Atrial fibrillation (AF) and atrial flutter (AFL) are related arrhythmias with common triggers, yet in individual patients either AF or AFL often predominates. We performed detailed electrophysiologic (EP) and electroanatomic (EA) studies of the right atrium (RA) in patients with AF and AFL to determine substrate differences that may explain the preferential expression of AF/AFL in individual patients. METHODS: Patients with AF (n = 13) were compared to patients with persistent AFL (n = 10). Detailed studies were performed, and 3-dimensional electroanatomic mapping studies were created and the RA was divided into 4 segments for regional analysis. Global, septal, lateral, anterior, and posterior segments were compared for analysis of: bipolar voltage; proportion of low-voltage areas and areas of electrical silence; conduction times; and proportion of abnormal signals (fractionated signals and double potentials). RESULTS: Compared to patients with AF, patients with AFL had (1) lower bipolar voltage and an increase in the proportion of low-voltage areas; (2) an increase in the proportion of complex signals; and (3) prolongation of activation times. CONCLUSIONS: Patients with AFL showed more advanced remodeling than patients with AF with slowed conduction, lower voltage areas with regions of electrical silence, and a greater proportion of complex signals, particularly in the posterior RA. These changes facilitate the stabilization of AFL and may explain why some patients are more likely to develop AFL as a sustained clinical arrhythmia.

Impact of collimation on radiation exposure during interventional electrophysiology.

AIMS: Fluoroscopy remains a cornerstone imaging technique in contemporary electrophysiology practice. We evaluated the impact of collimation to the 'minimal required field size' on clinically significant parameters of radiation exposure. METHODS AND RESULTS: Radiation dose measured by dose area product (DAP) and radiation dose rate measured by DAP per minute of fluoroscopy were determined for all 571 electrophysiology procedures performed in a single electrophysiology laboratory from January 2010 to December 2010. Data from 205 procedures performed by one interventional electrophysiologist, who instituted a practice of routinely collimating to the minimum required visual fluoroscopy field on a case-by-case basis, were compared with data from 366 procedures performed by the three other experienced interventional electrophysiologists using the laboratory who continued their existing practice of ad hoc collimation. Significant reductions in radiation exposure were seen with the practice of routine maximal collimation. The largest reductions were seen during 'simple' ablation procedures. CONCLUSION: A practice of routinely collimating to the minimum required visual fluoroscopy field results in significant reductions in radiation exposure when compared with a usual approach to collimation. This may have important implications for risk of malignancy in patients and operators.

Effect of respiration on catheter-tissue contact force during ablation of atrial arrhythmias.

BACKGROUND: Catheter-tissue contact is important for effective lesion creation. OBJECTIVE: To assess the effect of respiration on contact force (CF) during atrial fibrillation and cavotricuspid isthmus (CTI)-dependent atrial flutter ablation. METHODS: Patients undergoing CTI ablation alone (n = 15) and pulmonary vein (PV) isolation alone (n = 12) under general anesthesia were recruited. Lesions were delivered under ventilation (30 seconds) alternating with lesions delivered under apnea (30 seconds) at an adjacent anatomical site at CTI or PV antra. The average force (F(av)), force-time integral (FTI), and force variability were measured in a region-specific manner by using a novel CF-sensing ablation catheter. Operators were blinded to CF data. RESULTS: F(av) and FTI were higher with apnea than with ventilation in all CTI and PV segments (P <.05), an effect attributed to drop in CF with each respiratory swing, resulting in greater force variability during ventilation (P <.05). Low FTI lesions (<500 g) were strongly associated with longer ablation time to achieve bidirectional CTI block (r(2) = .81; P <.001), left PVI (r(2) = .65; P = .009), and right PVI (r(2) = .41; P = .05). Sites with transient CTI block were associated with lower F(av) and FTI than were sites with persistent CTI block (P <.05). Sites of acute PV reconnection were associated with lower F(av) and FTI compared with non-reconnected sites (P <.001). CONCLUSIONS: Catheter-tissue CF is critically influenced by respiration; greater CF is observed with ablation during apnea. Poor CF is implicated in longer ablation time to achieve CTI block or PV isolation and in acute reconnection.

Electroanatomic remodeling of the left atrium in paroxysmal and persistent atrial fibrillation patients without structural heart disease.

INTRODUCTION: The nature of the atrial substrate thought to contribute toward maintaining atrial fibrillation (AF) outside the pulmonary veins remains poorly defined. Therefore, our objective was to determine whether patients with paroxysmal and persistent AF have an abnormal electroanatomic substrate within the left atrium (LA). METHODS AND RESULTS: Thirty-one patients with AF (17 paroxysmal AF and 14 persistent AF) were compared with 15 age-matched controls with left-sided supraventricular tachycardia (SVT). High-density 3-dimensional electroanatomic maps were created and the LA was divided into 8 segments for regional analysis. Bipolar voltage, conduction, and effective refractory periods (ERPs) of the posterior LA, left atrial appendage (LAA), and distal coronary sinus (CSd) and percentage complex signals were assessed. In the majority of LA regions, compared with controls, AF patients had: (1) lower mean voltage and a higher percentage low voltage; (2) slower conduction; and (3) more prevalent complex signals. Many of these changes were more marked in the persistent than the paroxysmal AF group. CONCLUSIONS: Patients with AF have lower regional voltage, increased proportion of low voltage, slowed conduction, and increased proportion of complex signals compared to controls. Many of these changes are more pronounced in persistent AF patients, suggesting there may be a progressive nature to the changes. Differences occurred in the absence of structural heart disease. These substrate abnormalities provide further insight into the progressive nature of atrial remodeling and the mechanisms involved in maintenance of AF.

Long-term omega-3 polyunsaturated fatty acid supplementation reduces the recurrence of persistent atrial fibrillation after electrical cardioversion.

BACKGROUND: Persistent atrial fibrillation (AF) is associated with a high risk of recurrence after electrical cardioversion. OBJECTIVE: We examined if long-term supplementation with omega-3 polyunsaturated fatty acids in fish oils commenced >1 month prior to electrical cardioversion and continued thereafter reduces recurrence of persistent AF. METHODS: This was an open-label, randomized study of 178 patients with persistent AF >1-month duration. Participants were assigned to control group (n = 87) or omega-3 group (6 g/d fish oil; n = 91) and underwent cardioversion 1 month later. Concurrent antiarrhythmic use of sotalol or amiodarone was permitted. Fish oil was continued till return of persistent AF or a maximum of 1 year. Intention-to-treat analysis was performed for the primary end point defined as the recurrence of persistent AF. RESULTS: Mean duration of fish oil intake was 56 days precardioversion and a total of 242 days in follow-up. Eicosapentaenoic acid and docosahexaenoic acid, the active components of fish oils, were 1.8-fold and 2.1-fold higher, respectively, in the omega-3 group compared with controls at the time of cardioversion (P <.001). At 90 days, 38.5% of the patients receiving omega-3 fatty acid supplement had AF recurrence compared with 77.5% of the controls (hazard ratio [omega-3 vs control] 0.38; 95% confidence interval 0.27-0.56; P <.001). Omega-3 intake was associated with a significant reduction in AF recurrence with or without concurrent antiarrhythmic drugs. CONCLUSIONS: Omega-3 polyunsaturated fatty acid supplementation commenced >1 month prior to electrical cardioversion and continued thereafter reduces the recurrence of persistent AF. Randomized controlled trials on long-term fish oil supplementation are needed to confirm these findings.

Electroanatomic properties of the pulmonary veins: slowed conduction, low voltage and altered refractoriness in AF patients.

INTRODUCTION: Rapid PV activity is critical in initiating and maintaining AF. The underlying substrate responsible for this remains uncertain. We sought to identify if patients with paroxysmal (PAF) and persistent atrial fibrillation (PeAF) have an abnormal substrate within the pulmonary veins (PVs). METHODS AND RESULTS: Thirty-nine patients with AF (21 PAF, 18 PeAF) were compared with 15 age-matched controls with left-sided accessory pathways (AVRT). High-density 3D electroanatomic maps of the PVs were created. PV voltage, conduction, PV muscle sleeve length, effective refractory periods (ERPs) of the PVs, posterior left atrium (PLA), left atrial appendage (LAA) and distal coronary sinus (CSd), and signal complexity were assessed. Compared with controls, the PVs of AF patients had (1) lower mean-voltage and a higher % low-voltage; (2) shorter PV muscle sleeves; (3) slower conduction; (4) shorter ERP; and (5) more prevalent complex signals. Compared with the PAF group, the PeAF group had (1) higher % low voltage; (2) slower conduction; and (3) more complex signals. In PAF patients, the PLA and LAA ERPs were longer than controls and the PV ERP was shorter than controls; in PeAF patients PLA and LAA ERPs were reduced, but to a lesser extent than in the PVs. AF induction occurred during PV ERP testing in both AF groups, but not controls. CONCLUSIONS: PAF and PeAF patients demonstrate electrical and electroanatomic remodeling of the PVs compared to control patients without prior AF. Some of these changes were more marked in PeAF.

The relationship between complex fractionated electrograms and atrial low-voltage zones during atrial fibrillation and paced rhythm.

AIMS: Mapping of atrial fibrillation (AF) involves identification of low-voltage regions associated with complex fractionated electrograms (CFE) which theoretically represent abnormal substrate and targets for ablation. Whether low-voltage CFE areas also identify abnormal substrate during paced rhythm is unknown. METHODS AND RESULTS: Twelve patients with persistent AF undergoing ablation of AF had high-density three-dimensional electroanatomic maps created during AF and paced rhythm (24 maps) and the mean voltage during AF and paced rhythm was compared for eight segments of the left atrium (LA). The following were correlated during AF and paced rhythm: regional mean voltage; %low voltage (defined as <0.5 mV); and extent of CFE. In addition, the relationship between the extent of CFE in AF: (i) %low voltage and (ii) conduction during paced rhythm were determined. Mean voltage was lower during AF than paced rhythm for all regions and globally (0.7 ± 0.2 mV vs. 2.1 ± 0.6 mV, P < 0.001). The regional and overall %low voltage of the LA was greater during AF than paced rhythm (53 ± 19% vs. 9 ± 2%, P < 0.001). There was no correlation between mean voltage or %low voltage during AF and paced rhythm. Complex fractionated electrograms were prevalent throughout all regions during AF, but did not correlate with %low voltage, fractionation, or slowed conduction during paced rhythm. CONCLUSION: Areas of CFE and low voltage recorded during AF frequently demonstrate normal atrial myocardial characteristics (normal conduction, electrograms, and voltage) during sinus rhythm. Therefore, AF CFE sites do not necessarily identify regions of an abnormal atrial substrate. However, this does not exclude the possibility that CFE might identify a focal driver or source occurring in a region of normal atrial myocardium.

Evidence for functional divergence in arbuscular mycorrhizal fungi from contrasting climatic origins.

A considerable amount of phenotypic, genetic and symbiotic functional variability has been documented in arbuscular mycorrhizal fungi (AMF). However, little is known about whether distinct AMF ecotypes have evolved within their geographic range. We tested the hypothesis that AMF growing at temperatures closer to those prevalent within their origin would benefit their host and grow more than isolates distant from their native conditions. For each of six AMF species, we chose pairs of isolates that originated from distant areas with contrasting climates. Each isolate was grown in association with two grass species of different thermal optima at two temperature settings. Thus, we also tested whether AMF from different climatic origins were dependent on the thermal adaptation of the host plant species or to temperature per se. Although fungal growth was not directly affected by temperature, we found that AMF isolates originating from contrasting climates consistently and differentially altered plant growth. Our results suggest that AMF from contrasting climates have altered symbiotic function, thus linking an abiotic factor to ecotypic differentiation of putatively important symbionts.

Prevalence of fractionated electrograms in the coronary sinus: comparison between patients with persistent or paroxysmal atrial fibrillation and a control population.

BACKGROUND: Complex fractionated atrial electrograms (CFAEs) are often identified as targets for radiofrequency ablation in the coronary sinus (CS) of patients with atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to determine whether similar features are present in a normal control population. METHODS: Twenty-four patients with AF (12 paroxysmal, 12 persistent) were compared with 12 controls (undergoing radiofrequency ablation for supraventricular tachycardia) in whom at least 1 minute of AF was induced by rapid atrial pacing. Electrogram comparisons during sinus rhythm and AF were made offline. A random 10-second window of AF was used for analysis of fractionation and dominant frequency. RESULTS: The three groups were age matched. CFAEs during AF were less prevalent in the control versus the AF groups (control = 30% +/- 28%, paroxysmal AF = 63% +/- 34%, persistent AF = 62% +/- 29%, P = .01). This difference was significant for the proximal to mid-CS only. Conduction velocity within the CS was slower in AF versus control patients (paroxysmal AF = 51 +/- 6 cm/s, persistent AF = 52 +/- 6 cm/s, control = 73 +/- 11 cm/s, P <.001). Minimum AF cycle length was shorter in the AF groups versus the control group (paroxysmal AF = 132 +/- 34 ms, persistent AF = 127 +/- 34 ms, control = 168 +/- 30 ms, P = .01). No differences in dominant frequency or prevalence of sinus rhythm CFAE was seen among the three groups. CONCLUSION: AF patients have a higher prevalence of CFAE and short cycle length activation within the proximal CS than control patients with nonclinical AF. CFAE are associated with slowed CS conduction in AF patients. No difference in the dominant frequency during AF was seen. CS CFAEs are common in a control population with induced AF and are unlikely to signify clinically important AF drivers in this setting.