Atrial fibrillation ablation by single ring isolation versus wide antral isolation: Effects on left atrial size and function.

BACKGROUND: Pulmonary vein isolation (PVI) by single ring isolation (SRI) has been demonstrated to reduce recurrence of atrial fibrillation (AF) compared to the standard technique of wide antral isolation (WAI). In this study, we examine the differential effect of these techniques on left atrial size and function. METHODS: We examined left atrial (LA) size (LA maximum and LA minimum volumes) and function (LA emptying fraction and LA expansion index) over a period of 6 months following PVI as measured by transthoracic echocardiography in 187 patients that were enrolled in a randomised controlled trial of SRI vs WAI. RESULTS: Compared to pre-ablation, at 6 months post-PVI, there was a small decrease in the LA maximum volume in the WAI group (67.3 vs 62.7 mL, p=0.02). The LA size did not change significantly over 6 months in the SRI group. Patients who underwent SRI had a small reduction in the LA expansion index at 6 months post-PVI compared to baseline (80.6 vs 66.6%, p=0.02). LA function did not change significantly over 6 months in the WAI group. However, at 6 months, there was no difference in any measure of LA size or function between the SRI and WAI groups. CONCLUSIONS: SRI, whilst previously demonstrated to be more effective than WAI in preventing AF recurrence, is associated with minimal adverse effects on left atrial function at medium term follow-up despite the isolation of a larger region of LA myocardium.

CSANZ Position Statement on Sedation for Cardiovascular Procedures (2014).

The Cardiac Society of Australia and New Zealand (CSANZ) Position Statement describes evidence-based standards of training, pre-procedural assessment, procedural conduct and post-procedure care with respect to sedation for cardiovascular procedures. It also describes the environment in which sedation for electrophysiological and other cardiac procedures may be performed. This Statement was developed by a Working Group of the Cardiac Society of Australia and New Zealand. It was reviewed by the Continuing Education and Recertification Committee and ratified at the CSANZ Board meeting held on Friday 7 March 2014.

Atrial ectopy predicts late recurrence of atrial fibrillation after pulmonary vein isolation.

BACKGROUND: Late recurrence of atrial fibrillation (AF) after radiofrequency ablation remains significant. Asymptomatic recurrence poses a difficult clinical problem as it is associated with an equally increased risk of stroke and death compared with symptomatic AF events. Meta-analyses reveal that no single preablation patient characteristic efficiently predicts these AF recurrences. This study aimed to evaluate the prognostic value of premature atrial complex (PAC) occurrence with regard to the risk of late AF recurrence after radiofrequency ablation. METHODS AND RESULTS: The study cohort consisted of 124 patients with 7-day Holter recordings at 6 months post radiofrequency ablation for AF. No patients had AF recurrence before this time. Patients were followed-up every 6 months. Holter-detected PACs were defined as any supraventricular complexes occurring >30% earlier than expected. During a median follow-up of 4.2 years (first quartile to third quartile [Q1-Q3]=1.6-4.5), 32 patients (26%) had late recurrences of AF at a median of 462 days (Q1-Q3=319-1026) post radiofrequency ablation. The number of PACs per 24 hours was 248 (Q1-Q3=62-1026) in patients with and 77 (Q1-Q3=24-448) in patients without recurrence of AF (P=0.02). Multivariate analysis of the risk of late AF recurrence found ≥142 PACs per 24 hours to have a hazard ratio 2.84 (confidence interval, 1.26-6.43), P=0.01. CONCLUSIONS: This study showed that occurrence of ≥142 PACs per day at 6 months after PVI was independently associated with a significantly increased risk of late AF recurrence. These results could have important clinical implications for the design of post-PVI follow-up. CLINICAL TRIAL REGISTRATION: URL: http://www.anzctr.org.au. Unique identifier: ACRTN12606000467538.

Posterior left atrial isolation for atrial fibrillation in left ventricular diastolic impairment is associated with better arrhythmia free survival.

BACKGROUND: Patients with left ventricular diastolic impairment (LVDI) have higher rates of arrhythmia recurrence following atrial fibrillation (AF) ablation. Past studies have implicated the posterior left atrium (LA) in atrial arrhythmia maintenance in conditions that cause LVDI. We prospectively compared posterior LA isolation (PLAI) with wide antral isolation (WAI) in patients with LVDI having AF ablation. METHODS: We conducted a sub-study of a previously published large randomized control study that compared PLAI with WAI. Two hundred and twenty consecutive consenting patients referred for catheter ablation of AF (paroxysmal 135, persistent 48, long standing persistent 37) were recruited (female 43, mean age 59 ± 10 years). Transthoracic echocardiography identified 50 (23%) patients with LVDI and preserved left ventricular systolic function (ejection fraction ≥ 50%). Cox regression analysis was utilized to identify independent predictors of atrial arrhythmia after ablation. RESULTS: Patients were followed for median 4.6 (inter quartile range 4.0-5.5) years. Patients with LVDI having PLAI had better arrhythmia free survival than patients randomized to conventional ablation (Log rank P=0.028). The only independent predictor of recurrence utilizing Cox regression analysis was ablation strategy (2.3 [1.15-4.74], P=0.026). CONCLUSION: Posterior isolation of the LA results in superior atrial arrhythmia free survival in patients with LVDI. Further investigation is required to determine potential mechanisms. CLINICAL TRIAL REGISTRATION: http://www.anzctr.org.au;ACTRN12606000467538.

Acoustic signal emission monitoring as a novel method to predict steam pops during radiofrequency ablation: preliminary observations.

UNLABELLED: Steam pop is an explosive rupture of cardiac tissue caused by tissue overheating above 100 °C, resulting in steam formation, predisposing to serious complications associated with radiofrequency (RF) ablations. However, there are currently no reliable techniques to predict the occurrence of steam pops. We propose the utility of acoustic signals emitted during RF ablation as a novel method to predict steam pop formation and potentially prevent serious complications. METHODS: Radiofrequency generator parameters (power, impedance, and temperature) were temporally recorded during ablations performed in an in vitro bovine myocardial model. The acoustic system consisted of HTI-96-min hydrophone, microphone preamplifier, and sound card connected to a laptop computer. The hydrophone has the frequency range of 2 Hz to 30 kHz and nominal sensitivity in the range -240 to -165 dB. The sound was sampled at 96 kHz with 24-bit resolution. Output signal from the hydrophone was fed into the camera audio input to synchronize the video stream. An automated system was developed for the detection and analysis of acoustic events. RESULTS: Nine steam pops were observed. Three distinct sounds were identified as warning signals, each indicating rapid steam formation and its release from tissue. These sounds had a broad frequency range up to 6 kHz with several spectral peaks around 2-3 kHz. Subjectively, these warning signals were perceived as separate loud clicks, a quick succession of clicks, or continuous squeaking noise. Characteristic acoustic signals were identified preceding 80% of pops occurrence. Six cardiologists were able to identify 65% of acoustic signals accurately preceding the pop. An automated system identified the characteristic warning signals in 85% of cases. The mean time from the first acoustic signal to pop occurrence was 46 ± 20 seconds. The automated system had 72.7% sensitivity and 88.9% specificity for predicting pops. CONCLUSIONS: Easily identifiable characteristic acoustic emissions predictably occur before imminent steam popping during RF ablations. Such acoustic emissions can be carefully monitored during an ablation and may be useful to prevent serious complications during RF delivery.

Electrogram-gated radiofrequency ablations with duty cycle power delivery negate effects of ablation catheter motion.

BACKGROUND: Cardiac and respiratory movements cause catheter instability. Lateral catheter sliding over target endocardial surface can lead to poor tissue contact and unpredictable lesion formation. We describe a novel method of overcoming the effects of lateral catheter sliding movements using an electrogram-gated pulsed power ablation. METHODS AND RESULTS: All ablations were performed on a thermochromic gel myocardial phantom. Ablation settings were randomized to conventional (nongated) 30 W versus electrogram-gated at 20% duty cycle (30 W average power) at 0-, 3-, 6-, and 9-mm lateral sliding distances. Forty-eight radiofrequency ablations were performed. Deeper lesions were created in electrogram-gated versus conventional ablations at 3 mm (4.36±0.08 versus 4.05±0.17 mm; P=0.009), 6 mm (4.39±0.10 versus 3.44±0.15 mm; P<0.001), and 9 mm (4.41±0.06 versus 2.94±0.16 mm; P<<0.001) sliding distances. Electrogram-gated ablations created consistent lesions at a quicker rate of growth in depth when compared with conventional ablations (P<0.001). CONCLUSIONS: (1) Lesion depth decreases and length increases in conventional ablations with greater degrees of lateral catheter movements; (2) electrogram-gated pulsed radiofrequency delivery negated the effects from lateral catheter movement by creating consistently deeper lesions irrespective of the degree of catheter movement; and (3) target lesion depths were reached significantly faster in electrogram-gated than in conventional ablations.

Atrial tachycardias utilizing the Ligament of Marshall region following single ring pulmonary vein isolation for atrial fibrillation.

BACKGROUND: Organized atrial tachycardias (OATs) after pulmonary vein isolation (PVI) procedure are common. Arrhythmia mechanisms include mitral annular, ring gap, or roof-dependent gap-related flutters. In this series, we describe a mechanism of arrhythmia utilizing the ridge between left pulmonary vein (PV) and left atrial appendage (LAA) in the Ligament of Marshall (LOM) region. METHODS AND RESULTS: Five tachycardias involving the LOM region were identified from a group of 240 patients who underwent a single ring PVI procedure for symptomatic atrial fibrillation. The common characteristics of these tachycardias were the endocardial breakout over a broad area adjacent to the LOM region, presence of presystolic or mid-diastolic potentials, and abolition by ablation of the presystolic or mid-diastolic potentials remote from the endocardial breakout site. In all five cases, tachycardias were present after isolation of the veins and posterior left atria. All demonstrated characteristic areas of very slow conduction in the LOM region highlighted by presence of either low voltage, long duration fractionated potentials, or mid-diastolic potentials with a fixed temporal relationship to the subsequent endocardial activation. The pattern of activation and termination of tachycardia during ablation was consistent with an arrhythmia utilizing an electrically insulated tract within LOM and the PV-LAA ridge region. CONCLUSIONS: We identified a pattern of arrhythmias involving a concealed presystolic component and a broad endocardial breakout site related to the LOM region. Successful ablation site involved careful identification of small diastolic potentials in the LAA/ridge region or adjacent to the coronary sinus.

Sedation for electrophysiological procedures.

Administration of intravenous sedation (IVS) has become an integral component of procedural cardiac electrophysiology. IVS is employed in diagnostic and ablation procedures for transcutaneous treatment of cardiac arrhythmias, electrical cardioversion of arrhythmias, and the insertion of implantable electronic devices including pacemakers, defibrillators, and loop recorders. Sedation is frequently performed by nursing staff under the supervision of the proceduralist and in the absence of specialist anesthesiologists. The sedation requirements vary depending on the nature of the procedure. A wide range of sedation techniques have been reported with sedation from the near fully conscious to levels approaching that of general anesthesia. This review examines the methods employed and outcomes associated with reported sedation techniques. There is a large experience with the combination of benzodiazepines and narcotics. These drugs have a broad therapeutic range and the advantage of readily available reversal agents. More recently, the use of propofol without serious adverse events has been reported. The results provide a guide regarding the expected outcomes of these approaches. The complication rate and need for emergency assistance is low in reported series where sedation is administered by nonspecialist anesthesiology staff.

Circumflex coronary artery to left atrium fistula caused by mitral isthmus ablation.

Mitral isthmus ablation is an important component of catheter ablation for persistent atrial fibrillation and mitral isthmus dependent flutters. We describe a case where mitral isthmus ablation caused a fistula between the left circumflex artery and the left atrium and symptomatic ischaemia. The fistula was successfully closed with a covered stent.

What is the optimal left ventricular ejection fraction cut-off for risk stratification for primary prevention of sudden cardiac death early after myocardial infarction?

AIMS: The optimal left ventricular ejection fraction (LVEF) to select patients early post myocardial infarction (MI) for risk stratification for prevention of sudden cardiac death (SCD) in the era of primary percutaneous coronary intervention (PPCI) is unknown. METHODS AND RESULTS: Consecutive patients (n = 1722) treated with PPCI for ST-elevation MI underwent early (median 4 days) LVEF assessment. An electrophysiological study (EPS) was performed if LVEF ≤40% and a prophylactic implantable-cardioverter defibrillator (ICD) implanted for a positive [inducible monomorphic ventricular tachycardia (VT)], but not a negative, result. According to an early LVEF, a primary endpoint of inducible VT at EPS and a secondary endpoint of death or arrhythmia (SCD, resuscitated cardiac arrest or ECG-documented VT/ventricular fibrillation) were determined. The proportion of patients with early LVEF >40, 36-40, 31-35, and ≤30% were 75% (n = 1286), 7% (n = 128), 8% (n = 136), and 10% (n = 172), respectively. Inducible VT occurred in 22, 25, and 40% of patients with LVEF 36-40, 31-35, and ≤30%, respectively (P = 0.014). Three-year death or arrhythmia occurred in 6.6 ± 0.8, 8.1 ± 2.6, 18.0 ± 3.4, and 37.4 ± 3.9% of patients with LVEF >40, 36-40, 31-35, and ≤30%, respectively (overall P<0.001; LVEF 36-40% vs. LVEF > 40% P = 0.265). The number of EPS-positive patients implanted with an ICD to treat one or more arrhythmic event (95% confidence interval) was 18.3 ± 2.4, 11.5 ± 3.0, and 4.2 ± 5.6 if LVEF is 36-40, 31-35, and ≤30%, respectively. CONCLUSION: A cut-off LVEF of ≤40% selects patients with a high incidence of inducible VT post-PPCI. Patients with LVEF ≤35% and inducible VT appear to derive a greater benefit from prophylactic ICD implantation due to their higher risk of death or arrhythmia.

Significance of repeat programmed ventricular stimulation at electrophysiology study for arrhythmia prediction after acute myocardial infarction.

BACKGROUND: The prognostic significance of a second programmed ventricular stimulation (PVS) at electrophysiology study (EPS), when the first PVS is negative for inducible ventricular tachycardia (VT), in patients following myocardial infarction (MI) is unknown. METHODS: Consecutive ST-elevation MI patients with left ventricular ejection fraction ≤ 40% following revascularization underwent early EPS. An implantable cardioverter defibrillator (ICD) was implanted for a positive (inducible monomorphic VT) but not a negative (no arrhythmia or inducible ventricular fibrillation [VF]/flutter) EPS. The combined primary end point of death or arrhythmia (sudden death, resuscitated cardiac arrest, and spontaneous VT/VF) was assessed in EPS-positive patients grouped according to if VT was induced on the first PVS application, or the second PVS application, when the first was negative. RESULTS: EPS performed a median 8 days post-MI in 290 patients was negative in 70% (n = 203) and positive in 30% (n = 87). In patients with a positive EPS, VT was induced on the first PVS in 67% (n = 58) and the second PVS, after the first was negative, in 33% (n = 29). Predischarge ICD was implanted in 79 of 87 patients with a positive EPS. Three-year primary end point occurred in 20.9 ± 5.6% and 38.3 ± 9.7% of patients with VT induced by the first and second PVS, respectively (P = 0.042) and in 6.3 ± 1.9% of electrophysiology-negative patients (P < 0.001). CONCLUSIONS: In patients with post-MI left ventricular dysfunction, VT can be induced in a significant proportion with a second PVS when negative on the first. These patients have a similar higher risk of death or arrhythmia compared to patients with VT induced on the first PVS.

Long-term arrhythmia-free survival in patients with severe left ventricular dysfunction and no inducible ventricular tachycardia after myocardial infarction.

BACKGROUND: A negative electrophysiology study (EPS) may delineate a subgroup of patients with severely impaired left ventricular ejection fraction (LVEF) whose care can be safely managed long-term without an implantable cardioverter-defibrillator. METHODS AND RESULTS: Consecutive patients treated with primary percutaneous coronary intervention for ST-segment-elevation myocardial infarction underwent early (median 4 days) LVEF assessment. Patients with LVEF ≤40% underwent EPS. A prophylactic implantable cardioverter-defibrillator was implanted for a positive (inducible monomorphic ventricular tachycardia) but not a negative (no inducible ventricular tachycardia or inducible ventricular fibrillation/flutter) EPS result. Patients who would have become eligible for a late primary prevention implantable cardioverter-defibrillator with LVEF ≤30% or ≤35% with New York Heart Association class II/III heart failure were included and analyzed according to EPS result. Patients with LVEF >40%, ineligible for EPS, were followed up as control subjects (n=1286). The primary end point was survival free of death or arrhythmia (resuscitated cardiac arrest or sustained ventricular tachycardia/ventricular fibrillation). EPS performed in 128 patients with LVEF ≤30% or with LVEF ≤35% and heart failure was negative in 63% (n=80) and positive in 37% (n=48). Implantable-cardioverter defibrillators were implanted in <0.1%, 4%, and 90% of control, EPS-negative, and EPS-positive patients, respectively. The distribution of time to death or arrhythmia was comparable in control patients and EPS-negative patients with LVEF ≤30% or with LVEF ≤35% and heart failure (P=0.738), who both differed significantly from EPS-positive patients (P<0.001). At 3 years, 91.8 ± 3.2%, 93.4 ± 1.0%, and 62.7 ± 7.5% of control, EPS-negative, and EPS-positive patients were free of death or arrhythmia, respectively. CONCLUSIONS: Revascularized patients with ST-segment-elevation myocardial infarction with severely impaired left ventricular function but no inducible ventricular tachycardia have a favorable long-term prognosis without the protection of an implantable cardioverter-defibrillator.

Primary radiofrequency ablation of ventricular tachycardia early after myocardial infarction: evaluation in an ovine model.

BACKGROUND: Ventricular tachycardia (VT) is a significant complication of myocardial infarction. Radiofrequency ablation for postinfarct VT is reserved for drug refractory VT or VT storms. Our hypothesis is that radiofrequency ablation in the early postinfarct period could abolish or diminish late recurrences of VT. METHODS AND RESULTS: Myocardial infarct was induced by balloon occlusion of the left anterior descending artery in 35 sheep. The 25 survivors underwent programmed ventricular stimulation and electroanatomical mapping 8 days postinfarct. Animals with inducible VT (12 out of 25 animals) underwent immediate radiofrequency ablation. Further VT inductions were performed 100 and 200 days postinfarct. At day 8, 3.0±0.9 VT morphologies per animal were inducible. All were successfully ablated with 24±6 applications of radiofrequency energy. All had ablations on the left ventricular endocardium, and 67% had ablations on the right ventricular aspect of the interventricular septum. All targeted arrhythmias were successfully ablated acutely. One animal was euthanized because of hypotension from a serious pericardial effusion. The other 11 survived and remained arrhythmia free on subsequent inductions on the 100th and 200th days (P<0.001). The 13 animals without inducible VT remained noninducible at the subsequent studies. A historical control arm of 9 animals with inducible VT at day 8 remained inducible at day 100. CONCLUSIONS: Radiofrequency ablation on the eighth day after infarction abolished inducibility of VT at late induction studies ≤200 days in an ovine model. Early identification and ablation of VT after infarction may prevent or reduce late ventricular arrhythmias but needs to be validated in clinical studies.

Evolution of ventricular tachycardia and its electrophysiological substrate early after myocardial infarction: an ovine model.

BACKGROUND: Sudden arrhythmic death after myocardial infarction (MI) is most frequent in the first month. Early programmed ventricular stimulation (within 1 week) post-MI has been able to identify long-term ventricular tachycardia (VT) occurrence. We aimed to determine the timing of development and stabilization of VT circuits after MI and how the evolution of the underlying substrate differs with VT inducibility. METHODS AND RESULTS: MIs were induced in 36 sheep. The 21 survivors underwent serial electroanatomic mapping and programmed ventricular stimulation. Animals were classified as VTpos (inducible VT) or VTneg (noninducible VT) at day 8. Forty-three percent of MI survivors were VTpos on day 8 (9/21), and all remained inducible on day 100 with 1.5 (1.0-2.0) and 1.0 (1.0-2.0) morphologies per animal on days 8 and 100, respectively. Twelve-lead electrocardiogram matched in 15 of 19 VTs between days 8 and 100. The earliest presystolic ventricular activations during VT circuits were in similar locations at the 2 time points. The 12 VTneg animals remained noninducible on day 100. There was no difference in voltage or velocity substrate with time or inducibility. The area with fractionated signals increased with time and VT inducibility. VTpos animals had more linear regions of slowed conduction forming conducting channels. CONCLUSIONS: The inducibility and earliest presystolic endocardial activation sites of VT as well as voltage and velocity substrate on day 8 predicted those on day 100 postinfarct, indicating early formation and stabilization of the arrhythmogenic substrate. VT inducibility was influenced by the distribution of conducting channels and increased complex fractionated signals.

Significance of inducible very fast ventricular tachycardia (cycle length 200-230 ms) after early reperfusion for ST-segment-elevation myocardial infarction.

BACKGROUND: Electrophysiological study (EPS) after myocardial infarction may have a role in identifying patients at risk of sudden cardiac death. It has been shown previously that inducible very fast ventricular tachycardia (VT; cycle length [CL], 200-230 ms) is predictive of arrhythmia recurrence; however, its significance early after reperfusion in ST-segment-elevation myocardial infarction is unknown. METHODS AND RESULTS: Consecutive patients with ST-segment-elevation myocardial infarction treated with primary percutaneous coronary intervention with a left ventricular ejection fraction ≤40% underwent early EPS with an implantable-cardioverter defibrillator implanted for inducible VT, but not for a negative EPS. The end point was the cumulative incidence of death or first arrhythmic event (defined as resuscitated cardiac arrest or spontaneous ventricular tachyarrhythmia). A total of 1721 patients with ST-segment-elevation myocardial infarction underwent early left ventricular ejection fraction assessment (median, 4 days after myocardial infarction) with a left ventricular ejection fraction≤40% in 24%. EPS was performed in 290 eligible patients with no arrhythmia or ventricular fibrillation/flutter (CL<200 ms) induced in 203 patients (EPS negative, group 1), monomorphic VT induced in 87 patients, consisting of very fast VT in 67% (group 2; n=58), and standard VT (CL>230 ms) in 33% (group 3; n=29). Kaplan-Meier 4-year cumulative incidence of death or arrhythmia was 8.2±2.3%, 33.1±7.1%, and 37.0±10.2% in groups 1, 2, and 3, respectively (P<0.001). CONCLUSIONS: The majority of inducible VT in patients who have been reperfused early after ST-segment-elevation myocardial infarction is very fast VT (CL, 200-230 ms). This very fast VT incurs at least a similar risk of arrhythmia or death as inducible standard VT (CL>230 ms) and a significantly higher risk than patients with a negative EPS.

High spatial resolution thermal mapping of radiofrequency ablation lesions using a novel thermochromic liquid crystal myocardial phantom.

BACKGROUND: Radiofrequency (RF) ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF ablations were performed. This comprised 17 ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be <300 µm. CONCLUSIONS: High spatial resolution thermal mapping of in vitro RF lesions with spatial resolution of at least 300 µm is possible using a thermochromic liquid crystal myocardial phantom model, with a good correlation to in vivo RF ablations. This model may be useful for assessing the thermal characteristics of RF lesions created using different ablation parameters and catheter technologies.

Clinical evaluation of a new technique to monitor return electrode skin temperature during radiofrequency ablation.

PURPOSE: Return electrode burns occur occasionally in cardiac radiofrequency ablation and more frequently in tumor radiofrequency ablation. A return electrode incorporating a thermochromic liquid crystal (TLC) layer, which changes color with temperature, has been shown in sheep studies to accurately indicate underlying skin temperature. We aimed to validate the accuracy of TLC-coated return electrodes in indicating skin temperature in the clinical setting of cardiac radiofrequency ablation. METHODS AND RESULTS: The top layer of a standard return electrode was replaced with TLC. Fluoro-optic thermometer (FOT) probes were laid on the skin side of the return electrode, which was then placed on the left lateral mid-thigh of 18 patients (mean age = 61 ± 12 years, 12 men) undergoing cardiac radiofrequency ablation. Return electrode photographs were taken when FOT temperature exceeded 35 °C. TLC color changes, observed in 11 patients, were converted to temperature and compared with FOT temperature. TLC temperature correlated well with FOT temperature (Pearson's coefficient = 0.97 ± 0.03). Bland-Altman analysis showed good agreement (mean temperature difference = -0.04 ± 0.08 °C, upper limit of agreement = 0.11 ± 0.005 °C, lower limit of agreement = -0.19 ± 0.005 °C). The maximum FOT temperature recorded was 39.6 °C. There was no thermal injury at the return electrode site on any patients, when assessed immediately after and the day following the procedure. CONCLUSION: TLC-coated return electrodes accurately indicate underlying skin temperature in cardiac radiofrequency ablation and may help prevent burns. This technology might be essential in high energy radiofrequency ablation.

Single-ring posterior left atrial (box) isolation results in a different mode of recurrence compared with wide antral pulmonary vein isolation on long-term follow-up: longer atrial fibrillation-free survival time but similar survival time free of any atrial arrhythmia.

BACKGROUND: Electric isolation of the pulmonary veins and posterior left atrium with a single ring of radiofrequency lesions (single-ring isolation [SRI]) may result in fewer atrial fibrillation (AF) recurrences than wide antral pulmonary vein isolation (wide antral isolation [WAI]) by abolishing extravenous AF triggers. The effect of mitral isthmus line (MIL) ablation on outcomes after SRI has not previously been assessed. METHODS AND RESULTS: We randomly assigned 220 consecutive patients (58 ± 10 years old; 82% men) with highly symptomatic AF (61% paroxysmal, 39% persistent/longstanding persistent) to undergo either SRI or WAI. Half of each cohort was also randomly allocated to have left lateral MIL ablation (2 ×2 factorial study design). Patients were followed clinically and with 7-day Holter studies for arrhythmia recurrences. The primary end points were recurrence of AF and organized atrial tachyarrhythmias. AF-free survival at 2 years was better after SRI (74% [95% CI, 65%-82%]) than WAI (61% [51%-70%]; P=0.031). Organized atrial tachyarrhythmia-free survival was similar after SRI and WAI (67% [57%-75%] ersus 64% [54%-72%], respectively, at 2 years; P=0.988). MIL ablation resulted in better 2-year organized atrial tachyarrhythmia-free survival (71% [62%-79%] versus 60% [50%-69%]; P=0.07), which approached statistical significance. Survival free of any atrial arrhythmia after one procedure was not significantly affected by isolation technique or MIL ablation. Conclusions- SRI resulted in fewer AF recurrences compared with WAI on long-term follow-up but did not reduce the recurrence of all atrial arrhythmias. MIL ablation may reduce organized atrial tachyarrhythmia recurrences. Clinical Trial Registration- http://www.anzctr.org.au; ACTRN12606000467538.