Ventricular substrate identification using close-coupled paced electrogram feature analysis.

AIMS: Substrate based catheter ablation strategies are widely employed for treatment of scar-related ventricular tachycardia (VT). We analysed intracardiac electrograms (EGMs) from close-coupled paced extrastimuli extracted from the EnSite Precision mapping system. We sought to characterize EGM responses of ventricular myocardium to varying coupling intervals from the right ventricular apex (RVA) in both healthy individuals and patients presenting with VT for catheter ablation. METHODS AND RESULTS: Extrastimuli were delivered from the RVA after estimation of the ventricular effective refractory period. Electrograms were recorded from high-density mapping catheters in the left ventricle and exported for analysis to MATLAB. Observational data were collected from 14 patients with ischaemic VT (mean age 72.4 ± 6.3 years, one female) and five controls (mean age 59.4 ± 7.4 years, one female). These derived data were used to inform an interventional strategy on a further 10 patients (mean age 64.7 ± 10.0 years; two female). Significant differences were observed in EGM duration (ED) and latency (LT) at all coupling intervals between VT patients and controls. Significant increases in ED and LT with decreased RVA coupling interval were observed at VT isthmuses. Abnormal responses derived from control subject data were used to classify four types of ventricular EGM response. Targeting sites with abnormal LT and ED significantly reduced VT inducibility (5/14 derivation patients to 0/10 intervention patients; P = 0.03). CONCLUSION: Paced electrogram feature analysis is a novel tool to characterize the ischaemic substrate. Association with VT isthmuses and early ablation results suggest a possible role in substrate ablation for ischaemic VT.

Contact-Force Guided Pulmonary Vein Isolation does not Improve Success Rate in Persistent Atrial Fibrillation Patients and Severe Left Atrial Enlargement: A 12-month Follow-Up Study.

BACKGROUND: Catheter ablation is a cornerstone treatment strategy in atrial fibrillation (AF). Left atrial (LA) size is one of the contributors in development of AF recurrences. The impact of contact-forced (CF) guided catheter ablation on the success rate of persistent AF patients with severe enlarged LA has not been investigated yet. METHODS: Sixty-six patients with diagnosis of longstanding persistent AF undergoing catheter ablation were enrolled. All patients underwent a standard transthoracic echocardiography according to the guidelines. LA size was considered severely enlarged when LA diameter was ≥ 50 mm. CF catheter ablation with a Tacticath Quartz catheter (St Jude Medical, St. Paul, MN, USA) was used in all patients. RESULTS: The mean age was 61.9 ± 9.9 years, and LAD 47.8 ± 11.6 mm. Among 66 patients with persistent AF, 32 (48%) patients were diagnosed with AF recurrences. Twenty-eight (42%) patients had severely enlarged LA. The recurrence of AF was comparable in patients with and without severe enlarged LA (47% vs. 42%, p=0.79). The recurrence of AF was lower in patients who underwent CF-guided ablation with a normal LA dimension (36 %, p=0.54). Procedure duration was longer in patients with severely enlarged LA. LA dimension was not significantly different between patients with and without AF recurrence (49.8 ± 7.9 mm vs. 45.9 ± 7.5 mm, p=0.15). LAD and was significantly correlated with the time to recurrence of AF (r:-0.60, p=0.02). CONCLUSION: Our preliminary findings have demonstrated that CF guided ablation does not improve the success rate in longstanding persistent AF patients with severe LA enlargement.

Coring Recanalization of a Chronically Occluded Left Subclavian Vein.

A coring technique is an effective strategy to overcome short linear segmental chronic occlusions in subclavian veins caused by previously implanted leads. We present the case of an 82-year-old male who was transferred from a primary care center for consideration for implantable cardioverter-defibrillator placement following an episode of sustained monomorphic ventricular tachycardia and hemodynamic compromise that required direct-current cardioversion. A coring technique was successfully used in this patient.

Left Atrial Appendage characteristics in patients with Persistent Atrial Fibrillation undergoing catheter ablation (LAAPAF Study).

BACKGROUND: Despite technological and scientific efforts, the recurrence rate of persistent atrial fibrillation (AF) remains high. Several studies have shown that in addition to pulmonary vein (PV) isolation other non-PV triggers, particularly left atrial appendage may be the source of initiation and maintenance of AF. There are few studies showing the role of left atrial appendage (LAA) isolation in order to obtain higher success rate in persistent AF patients. OBJECTIVE: We analyzed the LAA volume, volume index and shape relative to the LA in patients with persistent AF undergoing AF ablation. METHODS: Fifty-nine consecutive patients with persistent AF who underwent catheter ablation were enrolled. Computerized tomography (CT) was performed in order to assess left atrial and PV anatomy including the LAA. Digital subtraction software (GE Advantage Workstation 4.3) was used to separate the LAA from the LA and calculate: LA volume (LAV), LA volume index (LAV/body surface area), LAA volume (LAAV), LAA volume index (LAA volume/LA volume), and LAA morphology [chicken wing (CW) or non-chicken wing (NCW)]. RESULTS: The mean age was 64.6 ± 9.8 years, 44 % male, and LA diameter 47.6 ± 7.8 mm. Median follow-up (FU) was 13 months. All patients had antral isolation of PVs and ablation of complex fractionation ± linear ablation (roof line/superior coronary sinus/mitral line). Among 59 patients with persistent AF, 26 (44 %) patients were diagnosed with AF recurrences. Mean LAV was 145.0 ± 45.9 ml, LAVI 68.9 ± 20.0 ml/m2, LAAV 10.3 ± 4.0 ml, and LAAVI 7.3 ± 2.7 ml/m2. LAA shape was non-chicken wing (NCW) in the majority of patients (51 %). LAA parameters were not significantly different between patients with and without AF recurrence (LAAV 11.0 ± 4.3 ml vs. 9.7 ± 3.8 ml, p=0.26; LAAVI 7.5 ± 3.0 ml/m2 vs. 7.2 ± 2.5 ml/m2, p=0.71; LAA shape of NCW 50 % vs 52 %, p=0.75, respectively). LAV was significantly correlated with the LAAV (r: o.47, p=0.009). The incidence of NCW LAA was significantly higher in patients with previous stroke/TIA (80 % vs. 20 %, p=0.04). CONCLUSION: The LAA anatomical characteristics (volume/volume index and the shape) were comparable in patients with/out AF recurrence post PVI. It remains to be determined if additional LAA isolation will impact outcomes in patients with persistent AF.

Interatrial block and interatrial septal thickness in patients with paroxysmal atrial fibrillation undergoing catheter ablation: Long-term follow-up study.

BACKGROUND: Interatrial block (IAB) is a strong predictor of recurrence of atrial fibrillation (AF). IAB is a conduction delay through the Bachman region, which is located in the upper region of the interatrial space. During IAB, the impulse travels from the right atrium to the interatrial septum (IAS) and coronary sinus to finally reach the left atrium in a caudocranial direction. No relation between the presence of IAB and IAS thickness has been established yet. OBJECTIVE: To determine whether a correlation exists between the degree of IAB and the thickness of the IAS and to determine whether IAS thickness predicts AF recurrence. METHODS: Sixty-two patients with diagnosis of paroxysmal AF undergoing catheter ablation were enrolled. IAB was defined as P-wave duration ≥120 ms. IAS thickness was measured by cardiac computed tomography. RESULTS: Among 62 patients with paroxysmal AF, 45 patients (72%) were diagnosed with IAB. Advanced IAB was diagnosed in 24 patients (39%). Forty-seven patients were male. During a mean follow-up period of 49.8 ± 22 months (range 12-60 months), 32 patients (51%) developed AF recurrence. IAS thickness was similar in patients with and without IAB (4.5 ± 2.0 mm vs. 4.0 ± 1.4 mm; p = .45) and did not predict AF. Left atrial size was significantly enlarged in patients with IAB (40.9 ± 5.7 mm vs. 37.2 ± 4.0 mm; p = .03). Advanced IAB predicted AF recurrence after the ablation (OR: 3.34, CI: 1.12-9.93; p = .03). CONCLUSIONS: IAS thickness was not significantly correlated to IAB and did not predict AF recurrence. IAB as previously demonstrated was an independent predictor of AF recurrence.

Increased Incidence of Ventricular Arrhythmias in Patients With Advanced Cancer and Implantable Cardioverter-Defibrillators.

OBJECTIVES: This study evaluated the incidence of ventricular arrhythmia and implantable cardioverter-defibrillator (ICD) therapies in patients with a diagnosis of cancer. BACKGROUND: Cardiac disease and cancer are prevalent conditions and share common predisposing factors. No studies have assessed the impact of cancer on the burden of ventricular arrhythmia in patients with cancer and ICDs. METHODS: Retrospective study of patients with an ICD and cancer who were followed from January 2007 to June 2015. Rates of ventricular tachycardia (VT) and ventricular fibrillation (VF) before and after patients' cancers were diagnosed were evaluated by searching device data collection systems. Rates were adjusted for length of follow-up and compared using the Wilcoxon test, and times to first therapy following diagnosis (stages I to III vs. IV) were compared using Kaplan-Meier curves and log-rank test. RESULTS: Among 1,598 patients with an ICD, 209 patients (13.1%) had a pathological diagnosis of malignancy; and in 102 patients (6.4%), malignancy was diagnosed following device insertion. After the diagnosis of cancer, 32% of patients experienced VT/VF over 23.2 ± 23.6 months, and the frequency of arrhythmic events was significantly increased after the diagnosis (1.19 ± 0.32 vs. 0.12 ± 0.21 episodes per month, respectively; p = 0.03). The incidence of VT/VF was markedly higher in patients with stage IV cancer than in those with earlier stages (p = 0.03). In this group, the incidence of VT/VF was 41.2%, with an average of 7.2 ± 18.5 events per patient, all of whom received ICD shocks. The rate of ICD deactivation in stage IV patients was 35.3%. Inappropriate therapies occurred in 13.7%, and atrial fibrillation was the most frequent cause. CONCLUSIONS: One-third of patients who had received ICDs developed ventricular arrhythmia after a diagnosis of cancer. The incidence was significantly higher in those with advanced metastatic disease. Findings underscore the need to discuss ICD management as part of end-of-life care.

Failed anti-tachycardia pacing can be used to differentiate atrial arrhythmias from ventricular tachycardia in implantable cardioverter-defibrillators.

BACKGROUND: Atrial fibrillation/tachycardia (AF/AT) may result in inappropriate therapies in implantable cardioverter-defibrillators (ICDs). The post-pacing interval (PPI) and tachycardia cycle length difference (PPI - TCL) has been previously demonstrated to indicate the proximity of the pacing site to a tachycardia origin. AIMS: We postulated that the PPI and PPI - TCL would be greater in AT/AF vs. ventricular tachycardia (VT) after episodes of failed anti-tachycardia pacing (ATP). METHODS AND RESULTS: This was a single-centre, retrospective study evaluating consecutive patients implanted with dual (DR)/biventricular (BIV) ICDs. Stored electrograms were used to determine whether the ATP captured the arrhythmia and the arrhythmia did not present with primary or secondary termination. Measurements were done using manual calipers. A total of 155 patients were included. There were 79 BIV and 76 DR devices. In total, 39 episodes were identified in 20 patients over a 23-month follow-up period. A total of 76 sequences of ATP (burst/ramp) were delivered, 28 (37%) of them inappropriate. Fifty-one events (18 AT/AF and 33 VT) were compared. The mean PPI was 693 ± 96 vs. 512 ± 88 ms (P < 0.01) and the mean PPI - TCL was 330 ± 97 vs. 179 ± 103 ms (P < 0.01) for AT/AF and VT, respectively. Cut-offs of 615 ms for the PPI [area under curve (AUC) 0.93; 95% confidence interval (CI): 0.84-1.00; P < 0.01] and 260 ms for PPI - TCL (AUC 0.86; 95% CI: 0.74-0.98; P < 0.01) were identified. CONCLUSION: The PPI and PPI - TCL after failed ATP differs significantly between AF/AT and VT and are therefore useful indices to discriminate between supraventricular tachycardia and VT in ICDs.

Obstructive sleep apnea as a predictor of atrial fibrillation after coronary artery bypass grafting: a systematic review and meta-analysis.

BACKGROUND: Post-coronary artery bypass grafting atrial fibrillation (PCAF) is associated with increased morbidity, mortality, and system costs. Few studies have explored obstructive sleep apnea (OSA) as a risk factor for PCAF. We aimed to systematically review and synthesize the evidence associating OSA with PCAF. METHODS: We conducted a search of MEDLINE, EMBASE, Google Scholar, and Web of Science, as well as abstracts, conference proceedings, and reference lists until June 2014. Eligible studies were in English, were conducted in humans, and assessed OSA with polysomnography (PSG) or a validated questionnaire. Two reviewers independently selected studies, with disagreement resolved by consensus. Piloted forms were used to extract data and assess risk of bias. RESULTS: Five prospective cohort studies were included (n = 642). There was agreement in study selection (κ statistic, 0.89; 95% confidence interval [CI], 0.75-1.00). OSA was associated with a higher risk of PCAF (odds ratio [OR], 1.86; 95% CI 1.24-2.80; P = 0.003; I(2) = 35%). We conducted 3 subgroup analyses. The associations increased for data that used PSG to assess OSA (OR, 2.34; 95% CI, 1.48-3.70), when severe OSA was included from 1 study (OR, 2.59; 95% CI, 1.63-4.11), and when adjusted analyses were pooled (OR, 2.38; 95% CI, 1.57-3.62; P < 0.001 in all), with no heterogeneity detected in any subgroup analysis (I(2) < 0.01% in all). CONCLUSIONS: OSA was shown to be a strong predictor of PCAF.

Celecoxib-induced change in atrial electrophysiologic substrate in arthritis patients.

BACKGROUND: Cyclooxygenase-2 inhibitors, the newest class of nonsteroidal antiinflammatories, pose an increased risk of adverse cardiovascular events, in particular atrial fibrillation (AF). We hypothesized that the COX-2 inhibitor celecoxib alters atrial electrophysiology, and thus promotes the development of AF. METHODS: Three prospective patient cohorts were created: Healthy patients (n = 35), inflammatory arthritis patients with no celecoxib use (n = 22), and inflammatory arthritis patients treated with celecoxib (n = 20). Patients were included in the arthritis cohorts if they were over the age of 18 and had a diagnosis of inflammatory arthritis. Patients in the celecoxib group must be actively treated with celecoxib for more than 2 months. Patients were excluded if they were taking antiarrhythmic mediation, had a diagnosis of AF, refractory hypertension, or congestive heart failure. High-resolution signal-averaged electrocardiogram was recorded and P-wave duration (PWD) was derived. RESULTS: PWD was significantly longer in inflammatory arthritis patients treated with celecoxib, compared to both healthy and inflammatory arthritis patients (P = 0.049, P = 0.036). There was no difference in the PWD of healthy patients as compared to inflammatory arthritis patients (P = 0.916). Mean PWD (standard error of the mean) of the inflammatory arthritis patients treated with celecoxib was 133.1 (2.7) ms as compared to 125.3 (1.6) ms in the healthy patients and 124.0 (2.9) ms in the inflammatory arthritis patients. CONCLUSIONS: Given that PWD is a well-accepted noninvasive marker of atrial electrophysiology, our results suggest that these patients demonstrate adverse atrial remodeling predisposing to atrial arrhythmia.

Heart rate variability and procedural outcome in catheter ablation for atrial fibrillation.

INTRODUCTION: In patients with normal hearts, increased vagal tone is associated with onset of paroxysmal atrial fibrillation (AF). Vagal denervation of the atria renders AF less inducible. Circumferential pulmonary vein isolation (CPVI) is effective for treating paroxysmal and persistent AF, and has been shown to impact heart rate variability (HRV) indices, in turn, reflecting vagal denervation. We examined the impact of CPVI on HRV indices, and evaluated the relationship between vagal modification and AF recurrence. METHODS: Electrocardiogram recordings were collected from 83 consecutive patients (63 male, 20 female, age 56.9 ± 9.3 years) undergoing CPVI for paroxysmal (n = 56) or persistent (n = 27) AF. Recordings were obtained over 10 minutes preprocedure, and at intervals up to 12 months. Antiarrhythmic medications were suspended prior to CPVI, and were resumed for 3 months following. Success was defined as no recurrence of atrial arrhythmia lasting longer than 30 seconds. RESULTS: In patients with successful procedures (n = 56, 42 paroxysmal, 14 persistent), HRV indices were significantly altered, with respect to preprocedure levels, over a sustained period. However, patients with recurrence (n = 27, 14 paroxysmal, 13 persistent) demonstrated similar HRV to their preprocedure levels over the follow-up period. CONCLUSION: Our results suggest that patients experiencing recurrence after a single CPVI have HRV attenuated by the procedure only intermittently, whereas patients with one successful CPVI experience a sustained change. A short-term HRV recording is a convenient and potentially important marker for recurrence of atrial arrhythmia in a population undergoing CPVI.

Radiofrequency catheter ablation for the treatment of idiopathic premature ventricular contractions originating from the right ventricular outflow tract: a systematic review and meta-analysis.

BACKGROUND: Frequent idiopathic premature ventricular contractions (PVCs) have been associated with left ventricular cardiomyopathy. Idiopathic PVCs often originate from the right ventricular outflow tract (RVOT), and radiofrequency catheter ablation (RFCA) is being used as a treatment to alleviate symptoms. A meta-analysis was performed to evaluate RFCA for the treatment of frequent idiopathic PVCs on heart function. METHODS AND RESULTS: A literature search was conducted using Medline and Embase to identify studies evaluating the effects of RFCA as treatment for PVCs originating from the RVOT. Articles were chosen if they reported the effect of RFCA on the quantity of PVCs or ventricular function. Only studies in English were included. Articles were excluded if they did not separate results for PVCs originating from areas other than the RVOT. A total of 450 articles were retrieved from electronic searches, and 14 articles were included in this systematic review. Six of these were meta-analyzed (N = 70) and showed a reduction in the total number of PVCs in 24 hours after RFCA by a mean of -30089.44 confidence interval [CI]: -31658.47, -28520.40, P < 0.00001). Left ventricular ejection fraction (LVEF) was reported in five of the 14 studies, which included 108 patients. RFCA significantly improved LVEF by a mean of 10.36 (CI: 8.75, 11.97, P < 0.00001) in patients with frequent PVCs from the RVOT. The remaining studies reported their results differently and were not included in the meta-analyses but were described separately. CONCLUSIONS: RFCA reduces the number of PVCs and improves the cardiac function in patients with idiopathic frequent PVCs originating from the RVOT.

Cardiac rhythm device contact dermatitis.

We present a series of three cases of patch testing confirmed cardiac rhythm device induced contact dermatitis. In the first two cases, there was complete resolution with device extraction and reimplantation with another device with either an absence of the offending agent or a coating with another resin or metal. These cases illustrate the difficulties in diagnosing pain, tenderness, and dermatological manifestations in patients with cardiac rhythm devices (pacemakers and implantable cardioverter defibrillators).

Validation of a novel algorithm for quantification of the percentage of signal fractionation in atrial fibrillation.

AIMS: Catheter ablation for paroxysmal atrial fibrillation (AF) is rapidly becoming a standard practice. There is literature to support that catheter ablation of persistent AF requires additional 'substrate modification'. In clinical practice, operators rely on automated fractionation maps created by three-dimensional anatomic mapping systems to rapidly assess complex 'fractionated' signals (CFAE). These systems use differing algorithms to automate the process. The agreement between operators and contemporary algorithms has not been examined. We sought to assess the agreement between operators and a novel method of quantification calculating percentage fractionation (PF). METHODS AND RESULTS: Expert opinion on 80 atrial electrogram 4 s signals of varying levels of activity were gathered and pooled for comparison. Twelve independent experts visually quantified the signal fractionation and offered a threshold level for ablation. We developed an algorithm to find sites with high continuous electrical activity, or high PF. Correlation between experts and PF was 0.78 [P < 0.01, 95% confidence interval (CI) (0.68-0.86)]. Receiver operating characteristics curve sensitivity and specificity for PF were 0.7727 and 0.8103 at the optimal cut-off point of 58.45 PF with area under curve 0.89 CI (0.80-0.99). CONCLUSION: The PF statistic represents a more robust and intuitive measure to represent fractionated atrial activity; importantly it demonstrates excellent agreement with expert users and presents a new standard for algorithm assessment. Use of a PF statistic should be considered in automated mapping systems.

Reverse atrial electrical remodelling induced by continuous positive airway pressure in patients with severe obstructive sleep apnoea.

BACKGROUND: Obstructive sleep apnoea (OSA) is associated with cardiovascular morbidity and mortality, including atrial arrhythmias. Continuous positive airway pressure (CPAP) is the gold standard treatment for OSA; its impact on atrial electrical remodelling has not been fully investigated. Signal-averaged p-wave (SAPW) duration is an accepted marker for atrial electrical remodelling. OBJECTIVE: The objective of this study is to determine whether CPAP induces reverse atrial electrical remodelling in patients with severe OSA. METHODS: Consecutive patients attending the Sleep Disorder Clinic at Kingston General Hospital underwent full polysomnography. OSA-negative controls and severe OSA were defined as apnoea-hypopnea index (AHI) < 5 events/hour and AHI ≥ 30 events/hour, respectively. SAPW duration was determined at baseline and after 4-6 weeks of CPAP in severe OSA patients or without intervention controls. RESULTS: Nineteen severe OSA patients and 10 controls were included in the analysis. Mean AHI and minimum oxygen saturation were 41.4 ± 10.1 events/hour and 80.5 ± 6.5 % in severe OSA patients and 2.8 ± 1.2 events/hour and 91.4 ± 2.1 % in controls. At baseline, severe OSA patients had a greater SAPW duration than controls (131.9 ± 10.4 vs 122.8 ± 10.5 ms; p = 0.02). After CPAP, there was a significant reduction of SAPW duration in severe OSA patients (131.9 ± 10.4 to 126.2 ± 8.8 ms; p < 0.001), while SAPW duration did not change after 4-6 weeks in controls. CONCLUSION: CPAP induced reverse atrial electrical remodelling in patients with severe OSA as represented by a significant reduction in SAPW duration.

Maximal electric separation-guided placement of right ventricular lead improves responders in cardiac resynchronization defibrillator therapy.

BACKGROUND: Cardiac resynchronization therapy is widely used for the treatment of heart failure. Recent data suggest that electric separation during left ventricular pacing varies within the right ventricle (RV). We hypothesized that placement of the RV lead guided by maximal electric separation (MES) would improve response to cardiac resynchronization therapy compared with standard apical placement. METHODS AND RESULTS: A single-blind, randomized controlled trial was conducted. Patients eligible for cardiac resynchronization therapy-D were enrolled. Left ventricular lead placement was performed at the coronary sinus branch. The RV outflow tract, septum, and apex were mapped during left ventricular pacing and MES recorded. Patients were randomized to receive either apical placement or RV lead placement at the site mapping MES. Left ventricular ejection fraction, 6-minute walk distance, and New York Heart Association functional class were recorded at baseline and 3 months by blinded observers. Response was defined as at least one of the following: 5% absolute increase in ejection fraction, 50 m increase in 6-minute walk distance, or an increase by >1 functional class. Primary end point was improvement in ejection fraction at 3 months. Fifty patients were randomized (25 MES-guided and 25 apical). Baseline characteristics were similar in the 2 groups. Electric separation was lower in the apex (143 ± 23 versus 168 ± 25 ms in MES group; P=0.01). MES was most commonly septal and rarely apical (4/50 patients). Responders in the MES-guided versus apical group are as follows: Echo 21 versus 13 patients (P=0.032), 6-minute walk distance 19 versus 12 patients (P=0.079), and functional class 22 versus 15 patients (P=0.051). No dislodgment or reposition for suboptimal defibrillation tests was reported. CONCLUSIONS: MES-guided placement of the RV lead improves cardiac resynchronization therapy responders compared with standard apical placement.

Electrocardiographic findings associated with cocaine use in humans: a systematic review.

Cocaine remains highly prevalent and accessible in the general population, continues to represent one of the most commonly reported substances in drug-related presentations to emergency departments, and is frequently implicated in drug-related deaths. Fatal cardiac arrhythmias are often suspected in the latter cases. In spite of this, its complex effects on the human cardiac conduction system remain poorly elucidated. In this article we sought to systematically review the medical literature to identify the electrocardiographic findings that have been linked to cocaine use in humans in an effort to highlight what physicians can expect to encounter when managing patients using the drug. The evidence is discussed, common findings are emphasized and clinical recommendations are proposed.