Alcohol Abstinence in Drinkers with Atrial Fibrillation.

BACKGROUND: Excessive alcohol consumption is associated with incident atrial fibrillation and adverse atrial remodeling; however, the effect of abstinence from alcohol on secondary prevention of atrial fibrillation is unclear. METHODS: We conducted a multicenter, prospective, open-label, randomized, controlled trial at six hospitals in Australia. Adults who consumed 10 or more standard drinks (with 1 standard drink containing approximately 12 g of pure alcohol) per week and who had paroxysmal or persistent atrial fibrillation in sinus rhythm at baseline were randomly assigned in a 1:1 ratio to either abstain from alcohol or continue their usual alcohol consumption. The two primary end points were freedom from recurrence of atrial fibrillation (after a 2-week "blanking period") and total atrial fibrillation burden (proportion of time in atrial fibrillation) during 6 months of follow-up. RESULTS: Of 140 patients who underwent randomization (85% men; mean [±SD] age, 62±9 years), 70 were assigned to the abstinence group and 70 to the control group. Patients in the abstinence group reduced their alcohol intake from 16.8±7.7 to 2.1±3.7 standard drinks per week (a reduction of 87.5%), and patients in the control group reduced their alcohol intake from 16.4±6.9 to 13.2±6.5 drinks per week (a reduction of 19.5%). After a 2-week blanking period, atrial fibrillation recurred in 37 of 70 patients (53%) in the abstinence group and in 51 of 70 patients (73%) in the control group. The abstinence group had a longer period before recurrence of atrial fibrillation than the control group (hazard ratio, 0.55; 95% confidence interval, 0.36 to 0.84; P = 0.005). The atrial fibrillation burden over 6 months of follow-up was significantly lower in the abstinence group than in the control group (median percentage of time in atrial fibrillation, 0.5% [interquartile range, 0.0 to 3.0] vs. 1.2% [interquartile range, 0.0 to 10.3]; P = 0.01). CONCLUSIONS: Abstinence from alcohol reduced arrhythmia recurrences in regular drinkers with atrial fibrillation. (Funded by the Government of Victoria Operational Infrastructure Support Program and others; Australian New Zealand Clinical Trials Registry number, ACTRN12616000256471.).

Finding a cause in sudden cardiac arrest survivors: Getting the testing right.

Sudden cardiac arrest (SCA) survivors are optimally managed by a multidisciplinary team with expertise in cardiac electrophysiology and cardiac genetics with the capacity to deal with both the medical and psychological needs of patients and their families. Consideration is given to an appropriate selection of second-line investigation, genetic testing, and cascade testing.

Sleep apnoea has a dose-dependent effect on atrial remodelling in paroxysmal but not persistent atrial fibrillation: a high-density mapping study.

AIMS: Obstructive sleep apnoea (OSA) associates with atrial fibrillation (AF), but the relationship of OSA severity and AF phenotype with the atrial substrate remains poorly defined. We sought to define the atrial substrate across the spectrum of OSA severity utilizing high-density mapping. METHODS AND RESULTS: Sixty-six consecutive patients (male 71%, age 61 ± 9) having AF ablation (paroxysmal AF 36, persistent AF 30) were recruited. All patents underwent formal overnight polysomnography and high-density left atrial (LA) mapping (mean 2351 ± 1244 points) in paced rhythm. Apnoea-hypopnoea index (AHI) (mean 21 ± 18) associated with lower voltage (-0.34, P = 0.005), increased complex points (r = 0.43, P < 0.001), more low-voltage areas (r = 0.42, P < 0.001), and greater voltage heterogeneity (r = 0.39, P = 0.001), and persisted after multivariable adjustment. Atrial conduction heterogeneity (r = 0.24, P = 0.025) but not conduction velocity (r = -0.09, P = 0.50) associated with AHI. Patchy regions of low voltage that co-localized with slowed conduction defined the atrial substrate in paroxysmal AF, while a diffuse atrial substrate predominated in persistent AF. The association of AHI with remodelling was most apparent among paroxysmal AF [LA voltage: paroxysmal AF -0.015 (-0.025, -0.005), P = 0.004 vs. persistent AF -0.006 (-0.017, 0.005), P = 0.30]. Furthermore, in paroxysmal AF an AHI ≥ 30 defined a threshold at which atrial remodelling became most evident (nil-mild vs. moderate vs. severe: 1.92 ± 0.42 mV vs. 1.84 ± 0.28 mV vs. 1.34 ± 0.41 mV, P = 0.006). In contrast, significant remodelling was observed across all OSA categories in persistent AF (1.67 ± 0.55 mV vs. 1.50 ± 0.66 mV vs. 1.55 ± 0.67 mV, P = 0.82). CONCLUSION: High-density mapping observed that OSA associates with marked atrial remodelling, predominantly among paroxysmal AF cohorts with severe OSA. This may facilitate the identification of AF patients that stand to derive the greatest benefit from OSA management.

Rapid Access Arrhythmia Clinics (RAACs) Versus Usual Care: Improving Efficiency and Safety of Arrhythmia Management.

BACKGROUND: Rapid access cardiology services have been proposed for assessment of acute cardiac conditions via an outpatient model-of-care that potentially could reduce hospitalisations. We describe a new Rapid Access Arrhythmia Clinic (RAAC) and compare major safety endpoints to usual care. METHODS: We matched 312 adult patients with suspected arrhythmia in RAAC to historical age and sex-matched controls discharged from hospital within Western Sydney Local Health District with suspected arrhythmia. The primary endpoint was a composite of time to first unplanned cardiovascular hospitalisation or cardiac death over 12 months. RESULTS: The average age of RAAC patients was 52.2±18.8 years and 51.6±18.8 years for controls, and 48.4% were female in both groups. Mean time from referral to first attended RAAC appointment was 10.5 days. Most were referred from emergency (177, 56.7%) and cardiologists at time of discharge (65, 20.8%). The most common reason for referral was palpitations (180, 57.7%). In total, 155 (49.7%) had a documented arrhythmia, with the most common being atrial fibrillation/flutter (88, 28.2%). The primary endpoint occurred in 35 (11.2%) patients in the RAAC pathway (97.1[95% CI 70-131.3] per 1,000 person-years), compared to 72 (23.1%) patients for usual care controls (229.5[95% CI 180.2-288.1] per 1,000 person-years). Using a propensity score analysis, RAAC pathway significantly reduced the primary endpoint by 59% compared to usual care (HR 0.41, 95% CI 0.27-0.62; p<0.001). CONCLUSIONS: RAACs for the early investigation and management of suspected arrhythmia is superior to usual care in terms of reduction in unplanned cardiovascular hospitalisation and death.

Catheter ablation of ventricular arrhythmia guided by a high-density grid catheter.

INTRODUCTION: Minimal data exist on the Advisor HD Grid (HDG) catheter and the Precision electroanatomic mapping (EAM) system for ventricular arrhythmia (VA) procedures. Using the HDG catheter, the EAM uses the high-density (HD) wave mapping and best duplicate software to compare the maximum peak-to-peak bipolar voltages within a small zone independent of wavefront direction and catheter orientation. This study aimed to summarize the procedural experience for VAs using the HDG catheter. METHODS: Clinical and procedural characteristics of VA ablation procedures were retrospectively reviewed that used the HDG catheter and the Precision EAM over a 12-month period. RESULTS: A total of 22 patients, 18 with sustained ventricular tachycardia and 4 with premature ventricular contractions were included. Clinically indicated left and/or right ventricular (LV, RV, respectively), and aortic maps were created. LV substrate maps (n = 13) used a median 1700 points (interquartile range [IQR]25%-75% , 1427-2412) out of a median 18 573 (IQR25%-75% , 15 713-41 067) total points collected. RV substrate maps (n = 11) used a median 1435 points (IQR25%-75% , 1114-1871) out of a median 16 005 (IQR25%-75% , 11 063-21 405) total points collected. Total point utilization, used vs collected, was 9%. Mean mapping time was 43 ± 17 minutes (substrate, 34 ± 18 minutes; activation/pace mapping, 9 ± 13 minutes). Acute success was achieved in 56 (86%) and short-term success achieved in 16 patients (73%) at a median follow-up of 145 days (IQR25%-75% , 62-273 days). There were no procedural complications. CONCLUSION: HD wave mapping using the novel HDG catheter integrated with the Precision EAM is safe and feasible in VA procedures in the LV, RV, and aorta. Mapping times are consistent with other multielectrode mapping catheters.

Cardioversion of atrial fibrillation in obese patients: Results from the Cardioversion-BMI randomized controlled trial.

AIMS: Obesity is associated with higher electrical cardioversion (ECV) failure in persistent atrial fibrillation (PeAF). For ease-of-use, many centers prefer patches over paddles. We assessed the optimum modality and shock vector, as well as the safety and efficacy of the Manual Pressure Augmentation (MPA) technique. METHODS: Patients with obesity (BMI ≥ 30) and PeAF undergoing ECV using a biphasic defibrillator were randomized into one of four arms by modality (adhesive patches or handheld paddles) and shock vector (anteroposterior [AP] or anteroapical [AA]). If the first two shocks (100 and 200 J) failed, then patients received a 200-J shock using the alternative modality (patch or paddle). Shock vector remained unchanged. In an observational substudy, 20 patients with BMI of 35 or more, and who failed ECV at 200 J using both patches/paddles underwent a trial of MPA. RESULTS: In total, 125 patients were randomized between July 2016 and March 2018. First or second shock success was 43 of 63 (68.2%) for patches and 56 of 62 (90.3%) for paddles (P = 0.002). There were 20 crossovers from patches to paddles (12 of 20 third shock success with paddles) and six crossovers from paddles to patches (three of six third shock success with patches). Paddles successfully cardioverted 68 of 82 patients compared with 46 of 69 using patches (82.9% vs 66.7%; P = 0.02). Shock vector did not influence first or second shock success rates (82.0% AP vs 76.6% AA; P = 0.46). MPA was successful in 16 of 20 (80%) who failed in both (patches/paddles), with 360 J required in six of seven cases. CONCLUSION: Routine use of adhesive patches at 200 J is inadequate in obesity. Strategies that improve success include the use of paddles, MPA, and escalation to 360 J.

Subclinical device-detected atrial fibrillation and stroke risk: a systematic review and meta-analysis.

Aims: To determine stroke risk in subclinical atrial fibrillation (AF) and temporal association between subclinical AF and stroke. Methods and results: Pubmed/Embase was searched for studies reporting stroke in subclinical AF in patients with cardiac implantable electronic devices (CIEDs). After exclusions, 11 studies were analysed. Of these seven studies reported prevalence of subclinical AF, two studies reported association between subclinical and clinical AF, seven studies reported stroke risk in subclinical AF, and five studies reported temporal relationship between subclinical AF and stroke. Subclinical AF was noted after CIEDs implant in 35% [interquartile range (IQR) 34-42] of unselected patients with pacing indication over 1-2.5 years. The definition and cut-off duration (for stroke risk) of subclinical AF varied across studies. Subclinical AF was strongly associated with clinical AF (OR 5.7, 95% CI 4.0-8.0, P < 0.001, I2 = 0%). The annual stroke rate in patients with subclinical AF > defined cut-off duration was 1.89/100 person-year (95% CI 1.02-3.52) with 2.4-fold (95% CI 1.8-3.3, P < 0.001, I2 = 0%) increased risk of stroke as compared to patients with subclinical AF < cut-off duration (absolute risk was 0.93/100 person-year). Three studies provided mean CHADS2 score. In these studies, with mean CHADS2 score of 2.1 ± 0.1, subclinical AF was associated with annual stroke rate of 2.76/100 person-years (95% CI 1.46-5.23). After excluding patients without AF, only 17% strokes occurred in presence of ongoing AF. Subclinical AF was noted in 29% [IQR 8-57] within 30 days preceding stroke. Conclusion: Subclinical AF strongly predicts clinical AF and is associated with elevated absolute stroke risk albeit lower than risk described for clinical AF.

The Impact of Diet and Lifestyle on Atrial Fibrillation.

PURPOSE OF REVIEW: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans, affecting more than 33 million people globally. Its association with complex, resource intensive medical conditions such as stroke, heart failure and dementia have had profound impacts across existing health care structures. The global prevalence of AF has enjoyed significant growth despite significant improvement in our armamentarium for arrhythmia treatment. RECENT FINDINGS: Efforts aimed at curtailing the incidence, prevalence, or progression of AF have prompted re-evaluation of traditional frameworks for understanding and managing this debilitating disease. It is in this context that focus has shifted toward lifestyle-associated factors such as obesity, hypertension, sleep apnoea, exercise, alcohol and diet, as mechanistic drivers and putative targets for therapy. Compelling evidence exists for weight loss and management of associated risk factors to improve outcomes of AF treatment. This review will address the epidemiologic and mechanistic evidence that link lifestyle-associated factors with AF and in light of this analysis evaluate the clinical impacts of their upstream management. Traditional paradigms of AF are shifting in light of emerging evidence, such that risk factor modification has become positioned as the fourth pillar of AF management.

Pericardial adipose and aromatase: A new translational target for aging, obesity and arrhythmogenesis?

A correlation exists between the extent of pericardial adipose and atrial fibrillation (AF) risk, though the underlying mechanisms remain unclear. Selected adipose depots express high levels of aromatase, capable of converting androgens to estrogens - no studies have investigated aromatase occurrence/expression regulation in pericardial adipose. The Women's Health Initiative reported that estrogen-only therapy in women elevated AF incidence, indicating augmented estrogenic influence may exacerbate cardiac vulnerability. The aim of this study was to identify the occurrence of pericardial adipose aromatase, evaluate the age- and sex-dependency of local cardiac steroid synthesis capacity and seek preliminary experimental evidence of a link between pericardial adipose aromatase capacity and arrhythmogenic vulnerability. Both human atrial appendage and epicardial adipose exhibited immunoblot aromatase expression. In rodents, myocardium and pericardial adipose aromatase expression increased >20-fold relative to young controls. Comparing young, aged and aged-high fat diet animals, a significant positive correlation was determined between the total aromatase content of pericardial adipose and the occurrence/duration of triggered atrial arrhythmias. Incidence and duration of arrhythmias were increased in hearts perfused with 17ß-estradiol. This study provides novel report of pericardial adipose aromatase expression. We show that aromatase expression is remarkably upregulated with aging, and aromatase estrogen conversion capacity significantly elevated with obesity-related cardiac adiposity. Our studies suggest an association between adiposity, aromatase estrogenic capacity and atrial arrhythmogenicity - additional investigation is required to establish causality. The potential impact of these findings may be considerable, and suggests that focus on local cardiac steroid conversion (rather than systemic levels) may yield translational outcomes.

A comparison of the electrophysiologic and electroanatomic characteristics between the right and left atrium in persistent atrial fibrillation: Is the right atrium a window into the left?

INTRODUCTION: The right atrium (RA) is readily accessible; however, it is unclear whether changes in the RA are representative of the LA. We performed detailed biatrial electroanatomic mapping to determine the electrophysiological relationship between the atria. METHODS AND RESULTS: Consecutive patients with persistent AF underwent biatrial electroanatomical mapping with a contact force catheter acquiring points with a CF >10 g prior to ablation. Points were analyzed for tissue voltage, complex electrograms, low voltage (<0.5 mV), scar (<0.05 mV), and conduction velocity (CV). Forty patients (mean age 59 ± 9.2 years, AF duration 12.9 ± 9.2 months, LA area: 28 ± 5.2, RA area: 25 ± 6.4 mm2 , LVEF: 44 ± 15%) underwent mapping during CS pacing. Bipolar voltage (R = 0.57, P <0.001), unipolar voltage (R = 0.68, P <0.001), low voltage (<0.5 nV) (R = 0.48, P = 0.002), fractionation (R = 0.73, P <0.001), and CV (R = 0.49, P = 0.001) correlated well between atria. There was no difference in global bipolar voltage (LA 1.89 ± 0.77 vs. RA 1.77 ± 0.57 mV, P = 0.57); complex electrograms (LA 20% vs. RA 20%, P = 0.99) or low voltage (LA 15% vs. RA 16%, P = 0.84). Global unipolar voltage was significantly higher in the LA compared to the RA (2.95 ± 1.14 vs. 2.28 ± 0.65 mV, P = 0.002) and CV was significantly slower in the RA compared to the LA (0.93 ± 0.15 m/s vs. 1.01 ± 0.19 m/s, P = 0.001). CONCLUSION: AF is associated with remodeling processes affecting both atria. The more accessible RA provides an insight into the biatrial process associated with AF in various disease states without trans-septal access.

Determining the Optimal Dose of Adenosine for Unmasking Dormant Pulmonary Vein Conduction Following Atrial Fibrillation Ablation: Electrophysiological and Hemodynamic Assessment. DORMANT-AF Study.

INTRODUCTION: ELECTROPHYSIOLOGICAL AND HEMODYNAMIC ASSESSMENT. DORMANT-AF STUDY: The significance of adenosine induced dormant pulmonary vein (PV) conduction in atrial fibrillation (AF) ablation remains controversial. The optimal dose of adenosine to determine dormant PV conduction is yet to be systematically explored. METHODS AND RESULTS: ELECTROPHYSIOLOGICAL AND HEMODYNAMIC ASSESSMENT. DORMANT-AF STUDY: Consecutive patients undergoing index AF ablation received 3 adenosine doses (12, 18, and 24 mg) in a randomized blinded order, immediately after pulmonary vein isolation (PVI). Electrophysiological (PR prolongation, AV block (AVB) and PV reconnection) and hemodynamic (BP) parameters were measured. A total, 339 doses (113/dose) assessed 191 PVs in 50 patients (66% male, 72% PAF, 52% hypertensive). Dormant PV conduction occurred in 28% of patients (16.5% [32] of PVs). All cases were associated with AVB (AVB: PV reconnection vs. no PV reconnection 100% vs. 83%, P = 0.007). AVB occurred more frequently at 24 mg versus 12 mg (92% vs. 82%, P = 0.019) but not versus 18 mg (91%, P = 0.62). AVB duration progressed between 12 mg (12.0 ± 8.9 seconds), 18 mg (16.1 ± 9.1 seconds, P = 0.001), and 24 mg (19.0 ± 9.3 seconds, P < 0.001) doses. MBP fell further at 24 mg (ΔMBP: 27 ± 12 mmHg) and 18 mg (26 ± 13 mmHg) doses compared to 12 mg (22 ± 10 mmHg vs., P < 0.001). A significant reduction in AVB in patients >110 kg (65% vs. 91% in 70-110 kg group, P < 0.001) in response to adenosine was seen. CONCLUSION: ELECTROPHYSIOLOGICAL AND HEMODYNAMIC ASSESSMENT. DORMANT-AF STUDY: An adenosine dose producing AVB is required to unmask dormant PV conduction. AVB is significantly reduced in patients >110 kg. Weight and dosing variability may in part explain the conflicting results of studies evaluating the clinical utility of adenosine in PVI.

Five seconds of 50-60 W radio frequency atrial ablations were transmural and safe: an in vitro mechanistic assessment and force-controlled in vivo validation.

AIMS: Longer procedural time is associated with complications in radiofrequency atrial fibrillation ablation. We sought to reduce ablation time and thereby potentially reduce complications. The aim was to compare the dimensions and complications of 40 W/30 s setting to that of high-power ablations (50-80 W) for 5 s in the in vitro and in vivo models. METHODS AND RESULTS: In vitro ablations-40 W/30 s were compared with 40-80 W powers for 5 s. In vivo ablations-40 W/30 s were compared with 50-80 W powers for 5 s. All in vivo ablations were performed with 10 g contact force and 30 mL/min irrigation rate. Steam pops and depth of lung lesions identified post-mortem were noted as complications. A total of 72 lesions on the non-trabeculated part of right atrium were performed in 10 Ovine. All in vitro ablations except for the 40 W/5 s setting achieved the critical lesion depth of 2 mm. For in vivo ablations, all lesions were transmural, and the lesion depths for the settings of 40 W/30 s, 50 W/5 s, 60 W/5 s, 70 W/5 s, and 80 W/5 s were 2.2 ± 0.5, 2.3 ± 0.5, 2.1 ± 0.4, 2.0 ± 0.3, and 2.3 ± 0.7 mm, respectively. The lesion depths of short-duration ablations were similar to that of the conventional ablation. Steam pops occurred in the ablation settings of 40 W/30 s and 80 W/5 s in 8 and 11% of ablations, respectively. Complications were absent in short-duration ablations of 50 and 60 W. CONCLUSION: High-power, short-duration atrial ablation was as safe and effective as the conventional ablation. Compared with the conventional 40 W/30 s setting, 50 and 60 W ablation for 5 s achieved transmurality and had fewer complications.

The role of obesity in atrial fibrillation.

Atrial fibrillation (AF) is commonly associated with overweight and obesity. Both conditions have been identified as major global epidemics associated with increased mortality and morbidity. Overweight populations have higher incidence, prevalence, severity, and progression of AF compared with their normal weight counterparts. Additionally, weight change appears to accompany alteration of arrhythmia profile, raising overweight, and obesity as potential targets for intervention. Recent clinical data confirm hypothesis drawn from epidemiological studies that durable weight reduction strategies facilitate effective management of AF. Stable weight loss decreases AF burden and AF recurrence following treatment. Structural remodelling in response to weight loss suggests that reverse remodelling of the AF substrate mediates improvement of arrhythmia profile. Obesity often co-exists with multiple AF risk factors that improve in response to weight loss, making a consolidated approach of weight loss and AF risk factor management preferable. However, weight loss for AF remains in its infancy, and its broad adoption as a management strategy for AF remains to be defined.

Ninety Seconds Could be the Optimal Duration for Ventricular Radiofrequency Ablation - Results From a Myocardial Phantom Model.

BACKGROUND: Shallow lesions could be the predominant factor affecting the efficacy of ventricular radiofrequency (RF) ablations. The objective of this study was to assess lesion dimensions and overheating in extended RF ablations up to 180seconds and compare with that of conventional 30seconds ablations. METHODS: The Navistar Thermocool irrigated catheter (Biosense Webster, CA, USA) was used in a previously validated myocardial phantom. Ablations were performed with 20W, 30W, 40W and 50W powers for 180seconds. The volume of lesion and overheating were measured at 530C and 800C isotherms respectively. RESULTS: A total of 110 RF lesions were analysed. The lesion depth increment when ablation was extended from the conventional 30seconds to 90seconds were 31.2±0.2, 33.6±0.6, 36.3±1.8% of that at 30seconds, respectively for powers 30W, 40W and 50W. During 30W ablations, at 90seconds the lesion width and depth were 95.4±1.2%, 91.8±1.6% respectively of the final dimensions at 180seconds. Similar proportions were observed for 40W and 50W. During 40W ablations, the volume of overheating was 113±6% and 184±11% higher at 90seconds and 180seconds respectively compared to that at 30seconds and was 142±9% and 194±9% for 50W ablations. CONCLUSION: Extending RF ablations up to 90seconds significantly increased the lesion depth (30-40%), however, overheating was present at 40W and 50W powers. Ablations beyond 90seconds provided little incremental value.

Obstructive Sleep Apnea Treatment and Atrial Fibrillation: A Need for Definitive Evidence.

Prevalence rates of atrial fibrillation (AF) and obstructive sleep apnea (OSA) are rising on a global scale. Epidemiological data have consistently demonstrated an independent association between the 2 conditions. Investigators pose that pathophysiologic features of OSA enable progression of the AF substrate; these features include abnormalities of gas exchange, autonomic remodeling, atrial stretch, and inflammation. Furthermore, many of the mechanistic perturbations that impact the AF substrate in OSA can be substantially attenuated by effective treatment with continuous positive airway pressure (CPAP). Clear associations of OSA treatment and improved AF control have been observed across multiple clinical contexts. However, the precision and generalizability of these findings are unclear in view of the data's observational nature. Although risk factor management has emerged as a critical component of AF treatment, effective control of many AF risk factors can be challenging in the longer term. In view of the efficacy and sustainability of CPAP therapy, OSA raises its profile as a prime candidate for intervention. However, translation of this strategy to the broader framework for AF management requires robust data from randomized controlled trials.

Circuit Impedance Could Be a Crucial Factor Influencing Radiofrequency Ablation Efficacy and Safety: A Myocardial Phantom Study of the Problem and its Correction.

BACKGROUND: Circuit impedance could affect the safety and efficacy of radiofrequency (RF) ablation. AIM: To perform irrigated RF ablations with graded impedance to compare (1) lesion dimensions and overheated dimensions in fixed power ablations (2) and in power corrected ablations. METHODS: Ablations were performed with irrigated Navistar Thermocool catheter and Stockert EP shuttle generator at settings of 40 W power for 60 seconds, in a previously validated myocardial phantom. The impedance of the circuit was set at 60 Ω, 80 Ω, 100 Ω, 120 Ω, 140 Ω, and 160 Ω. The lesion and overheated dimensions were measured at 53 °C and 80 °C isotherms, respectively. In the second set of ablations, power was corrected according to circuit impedance. RESULTS: In total, 70 ablations were performed. The lesion volume was 72.0 ± 4.8% and 44.7 ± 4.6% higher at 80 Ω and 100 Ω, respectively, compared to that at 120 Ω and it was 15.4 ± 1.2%, 28.1 ± 2.0%, and 38.0 ± 1.8% lower at 140 Ω, 160 Ω, and 180 Ω, respectively. The overheated volume was four times larger when impedance was reduced to 80 Ω from 100 Ω. It was absent at 120 Ω and above. In the power corrected ablations, the lesion volumes were similar to that of 40 W/120 Ω ablations and there was no evidence of overheating. CONCLUSION: The lesion and overheated dimensions were significantly larger with lower circuit impedance during irrigated RF ablation and the lesion size was smaller in high impedance ablations. Power delivery adjusted to impedance using a simple equation improved the consistency of lesion formation and prevented overheating.

Observations on Attenuation of Local Electrogram Amplitude and Circuit Impedance During Atrial Radiofrequency Ablation: An In vivo Investigation Using a Novel Direct Endocardial Visualization Catheter.

AIMS: To define the temporal characteristics of atrial lesion growth (lesion surface area), local electrogram amplitude attenuation, and circuit impedance decrement during in vivo radiofrequency (RF) ablation with direct endocardial visualization (DEV). METHODS AND RESULTS: A direct endocardial visualization catheter was used for real-time endoscopic visualization of atrial endocardial surface during RF ablation. Videos of lesion growth (surface area), circuit impedance, and local electrogram amplitude were recorded during ablation in 11 ovine. Fifty-two atrial ablations at 12 W, 14 W, and 16 W power for 30 seconds were analyzed. During 30-second RF ablation, the lesion matured (90% of final lesion dimension) in the first 23.0 ± 5.8 seconds. The local electrogram amplitude attenuation (80% decrement) and circuit impedance attenuation (20% decrement from initial) occurred 13.8 ± 8.2 seconds and 13.1 ± 7.9 seconds, respectively, before lesion maturity in a significant proportion of 30 second atrial ablations. CONCLUSION: The DEV observations suggest that in smooth atrial surface ablations with significant local electrogram and impedance decrement in the first 10 seconds, further extension of ablation for 10-15 seconds could deliver optimal surface dimensions; however, real-time measurement of depth was not possible.

Clinical significance of early atrial arrhythmia type and timing after single ring isolation of the pulmonary veins.

AIMS: Early atrial arrhythmia following atrial fibrillation (AF) ablation is associated with higher recurrence rates. Few studies explore the impact of early AF (EAF) and atrial tachycardia (EAT) on long-term outcomes. Furthermore, EAF/EAT have not been characterized after wide pulmonary vein isolation. We aimed to characterize EAF and EAT and its impact on late AF (LAF) and AT (LAT) after single ring isolation (SRI). METHODS AND RESULTS: We recruited 119 (females 21, age 58 ± 10 years) consecutive patients with AF (paroxysmal 76, persistent 43) undergoing SRI. Early atrial fibrillation/ early atrial tachycardia was defined as AF/AT within 3 months post-procedure (blanking period). Patients were followed for median 2.8[2.2-4] years. Early atrial fibrillation occurred in 28% (n = 33) and EAT in 25% (n = 30). At follow-up, 25% (n = 30) had LAF and 28% (n = 33) had LAT. Patients with EAF and EAT had higher rates of LAF (48 vs. 16%, P<0.0001) and LAT (60 vs. 16%, P < 0.0001), respectively. Independent predictors of LAF were EAF (3.53(1.72-7.29) P = 0.001); and of LAT were EAT (5.62(2.88-10.95) P < 0.0001) and procedure time (1.38/ h(1.07-1.78) P = 0.04). Importantly, EAF did not predict LAT and EAT did not predict LAF. Early atrial fibrillation late in the blanking period was associated with higher rates of LAF (73% for month 3 vs. 25% for Months 1-2, P = 0.004). However, EAT timing did not predict LAT. CONCLUSION: Early atrial fibrillation and EAT are predictive of LAF and LAT, respectively. Early atrial fibrillation late in the blanking period has greater predictive significance for LAF. This timing is not relevant for LAT. Early arrhythmia type and timing have important prognostic significance following SRI. CLINICAL TRIAL REGISTRATION: http://www.anzctr.org.au;ACTRN12606000467538.

Coronary artery reperfusion for ST elevation myocardial infarction is associated with shorter cycle length ventricular tachycardia and fewer spontaneous arrhythmias.

AIMS: Ventricular tachycardia (VT) induction at electrophysiological (EP) study early after ST elevation myocardial infarction (STEMI) has been a predictor of spontaneous ventricular arrhythmia. Reperfusion therapy for STEMI may have resulted in altered VT character. We attempted to determine differences in VT cycle length (CL) and VT recurrence rates, in patients who received early and late reperfusion treatment for STEMI. METHODS AND RESULTS: Of 180 consecutive patients with left ventricular ejection fraction < 40%, 77 patients had positive EP studies. Forty-nine patients receiving early reperfusion treatment (group 1, n = 49) were compared with 28 patients who received late reperfusion (group 2; n = 28). Seventy-five patients had defibrillators implanted for primary prevention of sudden death. Patients were followed for up to 6 years to assess long-term rates of spontaneous ventricular tachyarrhythmia. Patients who received early reperfusion demonstrated shorter CL inducible VT (231 ± 43 ms vs. 252 ± 56 ms; P = 0.016). They also had fewer spontaneous arrhythmias (adjusted hazard ratio of 2.94, 95% confidence interval: 1.07-8.13; P = 0.03) with shorter CL spontaneous VT (266 ± 54 ms vs. 320 ± 80 ms; P = 0.02) at 53 ± 33 months. Ventricular tachycardia CL was the only independent predictor of spontaneous arrhythmia or sudden cardiac death (1.22, 1.07-1.47; P = 0.016). CONCLUSIONS: Patients receiving early reperfusion for STEMI had faster inducible and spontaneous VT and fewer spontaneous recurrences. This may be due to changes in the myocardial substrate as a result of early coronary artery reperfusion.