Impact of artificial intelligence arrhythmia mapping on time to first ablation, procedure duration, and fluoroscopy use.

INTRODUCTION: Artificial intelligence (AI) ECG arrhythmia mapping provides arrhythmia source localization using 12-lead ECG data; whether this information impacts procedural efficiency is unknown. We performed a retrospective, case-control study to evaluate the hypothesis that AI ECG mapping may reduce time to ablation, procedural duration, and fluoroscopy. MATERIALS AND METHODS: Cases in which system output was used were retrospectively enrolled according to IRB-approved protocols at each site. Matched control cases were enrolled in reverse chronological order beginning on the last day for which the technology was unavailable. Controls were matched based upon physician, institution, arrhythmia, and a predetermined complexity rating. Procedural metrics, fluoroscopy data, and clinical outcomes were assessed from time-stamped medical records. RESULTS: The study group consisted of 28 patients (age 65 ± 11 years, 46% female, left atrial dimension 4.1 ± 0.9 cm, LVEF 50 ± 18%) and was similar to 28 controls. The most common arrhythmia types were atrial fibrillation (n = 10), premature ventricular complexes (n = 8), and ventricular tachycardia (n = 6). Use of the system was associated with a 19.0% reduction in time to ablation (133 ± 48 vs. 165 ± 49 min, p = 0.02), a 22.6% reduction in procedure duration (233 ± 51 vs. 301 ± 83 min, p < 0.001), and a 43.7% reduction in fluoroscopy (18.7 ± 13.3 vs. 33.2 ± 18.0 min, p < 0.001) versus controls. At 6 months follow-up, arrhythmia-free survival was 73.5% in the study group and 63.3% in the control group (p = 0.56). CONCLUSION: Use of forward-solution AI ECG mapping is associated with reductions in time to first ablation, procedure duration, and fluoroscopy without an adverse impact on procedure outcomes or complications.

Arrhythmias and sudden cardiac death in post-cardiac transplant patients.

PURPOSE OF REVIEW: Orthotopic heart transplantation (OHT) significantly improves morbidity and mortality in patients with end-stage heart disease. Despite advances in surgical technique, immunosuppressive therapies, and patient monitoring, long-term risk of arrhythmias and sudden cardiac death (SCD) in the denervated heart remains unchanged. RECENT FINDINGS: SCD is responsible for approximately 10% of all posttransplant deaths with a pooled incidence rate of 1.30 per 100 person years and is strongly associated with cardiac allograft vasculopathy (CAV). Risk factors for SCD and CAV include higher donor age, younger recipient age, and reduced left ventricular ejection fraction. Little is known about the time course between CAV and SCD. Although some registry data establish ventricular fibrillation as a documented terminal rhythm, the arrhythmia may not be the mechanism of SCD. SUMMARY: In this review, we identify risk factors and general independent predictors of arrhythmia and SCD and discuss the utility of implantable cardiac defibrillators in post-cardiac transplant patients.

Variants of accessory pathways.

Variant accessory pathways include atriofascicular, nodofascicular, nodoventricular, atrio-Hisian, and fasciculoventricular pathways. Atriofascicular pathways are the most common with others occurring rarely. The anatomical descriptions, electrocardiographic findings, electrophysiologic findings, and clincial manifestations are discussed.

Clinical factors associated with baseline history of atrial fibrillation and subsequent clinical outcomes following initial implantable cardioverter-defibrillator placement.

BACKGROUND: Atrial fibrillation (AF) is frequently present in patients with heart failure (HF) and an implantable cardioverter-defibrillator (ICD). This study aims to identify clinical factors associated with a baseline history of AF in ICD recipients, and compares subsequent clinical outcomes in those with and without a baseline history of AF. METHODS: We studied 566 consecutive first-time ICD recipients at an academic center between 2011 and 2018. Logistic regression multivariable analyses were used to identify clinical factors associated with a baseline history of AF at the time of ICD implant. Cox-proportional hazard regression models were constructed for multivariate analysis to examine associations between a baseline history of AF with subsequent clinical outcomes, including ICD therapies, HF readmission, and all-cause mortality. RESULTS: Of all patients, 201 (36%) had a baseline history of AF at the time of ICD implant. In multivariate analyses, clinical factors associated with a baseline history of AF included hypertension, valvular heart disease, body weight, PR interval, and serum creatinine level. After multivariate adjustment for potential confounders, a baseline history of AF was associated with an increased risk of anti-tachycardia pacing (HR = 1.84, 95% CI = 1.19-2.85, P = .006), appropriate ICD shocks (HR = 1.80, 95% CI = 1.05-3.09, P = .032), and inappropriate ICD shocks (HR = 3.72, 95% CI = 1.7-7.77, P = .0001), but not other adverse outcomes. CONCLUSION: Among first-time ICD recipients, specific clinical characteristics were associated with a baseline history of AF at the time of ICD implant. After adjustment for potential confounders, a baseline history of AF was associated with a higher risk of all ICD therapies in follow-up.

Injectable loop recorder implantation in an ambulatory setting by advanced practice providers: Analysis of outcomes.

INTRODUCTION: Implantable loop recorder (ILR) insertion has historically been performed in a surgical environment such as the electrophysiology (EP) lab. The newest generation loop recorder (Medtronic Reveal LINQ™, Minneapolis, MN, USA) is injectable with potential for implantation in a non-EP lab setting by advanced practice providers (APPs) facilitating improved workflow and resource utilization. We report the safety and efficacy of injectable ILR placement in the ambulatory care setting by APPs. METHODS: A retrospective review was performed including all patients referred for injectable ILR placement from March 2014 to November 2015. All device placement procedures were performed in an ambulatory care setting using the standard manufacturer deployment kit with sterile technique and local anesthetic following a single dose of intravenous antibiotics. Acute procedural success and complication rates following injectable ILR placement in the ambulatory setting were reviewed. RESULTS: During the study period, 125 injectable ILRs were implanted. Acute procedural success with adequate sensing (R-waves ≥ 0.2 mV) occurred in 100% of patients. There were no acute procedural complications. Subacute complications occurred in two patients (1.6% of implantations), including one possible infection treated with oral antibiotics and one device removal due to pain at the implant site. CONCLUSION: In this retrospective single-center study, implantation of injectable ILR in an ambulatory care setting by APPs following a single dose of intravenous antibiotics and standard manufacturer technique yielded a low complication rate with high acute procedural success. Use of this implantation strategy may improve EP lab workflow while providing a safe and effective technique for device placement.

Concealed Accessory Pathways with a Single Ventricular and Two Discrete Atrial Insertion Sites.

BACKGROUND: Atrioventricular reciprocating tachycardia (AVRT) utilizing a concealed accessory pathway is common. It is well appreciated that some patients may have multiple accessory pathways with separate atrial and ventricular insertion sites. METHODS: We present three cases of AVRT utilizing concealed pathways with evidence that each utilizing a single ventricular insertion and two discrete atrial insertion sites. RESULTS: In case one, two discrete atrial insertion sites were mapped in two separate procedures, and only during the second ablation was the Kent potential identified. Ablation of the Kent potential at this site remote from the two atrial insertion sites resulted in the termination of the retrograde conduction in both pathways. Case two presented with supraventricular tachycardia (SVT) with alternating eccentric atrial activation patterns without alteration in the tachycardia cycle length. The two distinct atrial insertion sites during orthodromic AVRT and ventricular pacing were targeted and each of the two atrial insertion sites were successfully mapped and ablated. In case three, retrograde decremental conduction utilizing both atrial insertion sites was identified prior to ablation. After mapping and ablation of the first discrete atrial insertion site, tachycardia persisted utilizing the second atrial insertion site. Only after ablation of the second atrial insertion site was SVT noninducible, and VA conduction was no longer present. CONCLUSIONS: Concealed retrograde accessory pathways with discrete atrial insertion sites may have a common ventricular insertion site. Identification and ablation of the ventricular insertion site or the separate discrete atrial insertion sites result in successful treatment.

Contact force-sensing catheters.

PURPOSE OF REVIEW: The purpose of this review is to highlight recent research findings in contact force-sensing radiofrequency ablation catheters. RECENT FINDINGS: Contact force parameters evaluated during pulmonary vein isolation for treating atrial fibrillation correlated well with the presence of gaps in the wide area circumferential ablation lines at 3 months, decreased procedural times, and improved clinical outcome at 1 year. The contact force during pulmonary vein isolation should be a target of 10-20 g of force and a minimum force-time integral of 400 g/s for each new lesion. In the ventricle, contact force varied depending on whether a transseptal versus retrograde aortic approach was utilized: contact force use yielded more visible ablation lesions at necropsy. SUMMARY: Contact force-sensing catheters have demonstrated improved outcome after catheter ablation of atrial fibrillation. Future studies will focus on ventricular tachycardia ablation; preliminary data suggest more durable lesions with contact force-sensing catheters. Contact force catheters may enhance academic training by giving real-time feedback regarding catheter contact, increase safety, and may lead to a resurgence in remote navigation ablation systems.

Combination drug therapy for patients with intractable ventricular tachycardia associated with right ventricular cardiomyopathy.

BACKGROUND: Drug therapy for patients with right ventricular (RV) cardiomyopathy refractory to single-drug therapy and ablation has not been well defined. METHODS: We reviewed our entire RV cardiomyopathy database (31 patients) and found four patients presenting with ventricular arrhythmias of RV origin refractory to single-drug therapy. These patients underwent complete evaluation for arrhythmogenic right ventricular cardiomyopathy (ARVC). RESULTS: Following the revised 2010 task force criteria, of these four patients, three were diagnosed with ARVC, and one with cardiac sarcoidosis. These patients proved to be refractory to drug monotherapy and either failed or deemed to not be candidates for endocardial ablation. Their arrhythmias were ultimately controlled with combinations of sotalol, flecainide, and mexiletine. CONCLUSIONS: In our experience, combination drug therapy is an effective treatment strategy for patients with ventricular tachycardia refractory to monotherapy and, in some cases, ablation. In addition, flecainide appears to be safe and effective for those with RV cardiomyopathy without significant left ventricular dysfunction.

Infra-Hisian Conduction Disturbance and Alternating Left Anterior/Posterior Fascicular Block.

We present an unusual case of alternating left anterior and left posterior fascicular block. Given the known risk for progression to complete atrioventricular block with alternating right bundle and left bundle branch block, we performed an electrophysiological study. Findings were consistent with infra-Hisian disease, and the patient underwent pacemaker implantation.

Pulsed field ablation versus thermal energy ablation for atrial fibrillation: a systematic review and meta-analysis of procedural efficiency, safety, and efficacy.

BACKGROUND: Pulsed field ablation (PFA) induces cell death through electroporation using ultrarapid electrical pulses. We sought to compare the procedural efficiency characteristics, safety, and efficacy of ablation of atrial fibrillation (AF) using PFA compared with thermal energy ablation. METHODS: We performed an extensive literature search and systematic review of studies that compared ablation of AF with PFA versus thermal energy sources. Risk ratio (RR) 95% confidence intervals (CI) were measured for dichotomous variables and mean difference (MD) 95% CI were measured for continuous variables, where RR < 1 and MD < 0 favor the PFA group. RESULTS: We included 6 comparative studies for a total of 1012 patients who underwent ablation of AF: 43.6% with PFA (n = 441) and 56.4% (n = 571) with thermal energy sources. There were significantly shorter procedures times with PFA despite a protocolized 20-min dwell time (MD - 21.95, 95% CI - 33.77, - 10.14, p = 0.0003), but with significantly longer fluroscopy time (MD 5.71, 95% CI 1.13, 10.30, p = 0.01). There were no statistically significant differences in periprocedural complications (RR 1.20, 95% CI 0.59-2.44) or recurrence of atrial tachyarrhythmias (RR 0.64, 95% CI 0.31, 1.34) between the PFA and thermal ablation cohorts. CONCLUSIONS: Based on the results of this meta-analysis, PFA was associated with shorter procedural times and longer fluoroscopy times, but no difference in periprocedural complications or rates of recurrent AF when compared to ablation with thermal energy sources. However, larger randomized control trials are needed.

Current role of atrioventricular junction (AVJ) ablation.

Atrioventricular junction ablation with permanent pacemaker insertion is a highly effective treatment approach in patients with atrial fibrillation that is resistant to other treatment modalities, especially in the elderly or those with severe comorbidities. This effect likely reflects reversal of rapid ventricular rates and regularizing ventricular rates. There is increasing evidence that cardiac resynchronization therapy devices may be beneficial in selected populations after atrioventricular node ablation. The limitations of this approach include continued need for anticoagulation and lifelong pacemaker therapy.

Safety and efficacy of catheter ablation of atrial fibrillation in the very elderly (≥80 years old): Insights from the UC San Diego AF Ablation Registry.

BACKGROUND: Catheter ablation improves outcomes in symptomatic atrial fibrillation (AF) patients. However, its safety and efficacy in the very elderly (≥80 years old) is not well described. HYPOTHESIS: Ablation of AF in the very elderly is safe and effective. METHODS: We performed a retrospective study of all patients who underwent catheter ablation enrolled in the University of California, San Diego AF Ablation Registry. The primary outcome was freedom from atrial arrhythmias on or off antiarrhythmic drugs (AADs). RESULTS: Of 847 patients, 42 (5.0%) were 80 years of age or greater with a median age of 81.5 (80-82.3) and 805 (95.0%) were less than 80 years of age with a median age of 64.4 (57.6-70.2). Among those who were ≥80 years old, 29 were undergoing de novo ablation (69.0%), whereas in the younger cohort, 518 (64.5%) were undergoing de novo ablation (p = .548). There were no statistically significant differences in fluoroscopy (p = .406) or total procedure times (p = .076), AAD use (p = .611), or procedural complications (p = .500) between groups. After multivariable adjustment, there were no statistically significant differences in recurrence of any atrial arrhythmias on or off AAD (adjusted hazard ratio [AHR]: 0.75; 95% confidence interval [CI]: 0.45-1.23; p = .252), all-cause hospitalizations (AHR: 0.86; 95% CI: 0.46-1.60; p = .626), or all-cause mortality (AHR: 4.48; 95% CI: 0.59-34.07; p = .147) between the very elderly and the younger cohort. CONCLUSION: In this registry analysis, catheter ablation of AF appears similarly effective and safe in patients 80 years or older when compared to a younger cohort.

Association of isoproterenol infusion during catheter ablation of atrial fibrillation with outcomes: insights from the UC San Diego AF Ablation Registry.

BACKGROUND: High-dose isoproterenol infusion is a useful provocative maneuver to elicit triggers of atrial fibrillation (AF) during ablation. We evaluated whether the use of isoproterenol infusion to elicit triggers of AF after ablation is associated with differential outcomes. METHODS: We performed a retrospective study of all patients who underwent de novo radiofrequency catheter ablation of AF enrolled in the University of California, San Diego AF Ablation Registry. The primary outcome was freedom from atrial arrhythmias on or off antiarrhythmic drugs (AAD). RESULTS: Of 314 patients undergoing AF ablation, 235 (74.8%) received isoproterenol while 79 (25.2%) did not. Among those who received isoproterenol, 11 (4.7%) had additional triggers identified. There were no statistically significant differences in procedure time (p = 0.432), antiarrhythmic drug use (p = 0.289), procedural complications (p = 0.279), recurrences of atrial arrhythmias on or off AAD [adjusted hazard ratio (AHR) 0.92 (95% CI 0.58-1.46); p = 0.714], all-cause hospitalizations [AHR 1.00 (95% CI 0.60-1.67); p = 0.986], or all-cause mortality [AHR 0.14 (95% CI 0.01-3.52); p = 0.229] between groups. CONCLUSIONS: In this registry analysis, use of isoproterenol is safe but was not associated with a reduction in recurrence of atrial arrhythmias.

Safety and acute efficacy of catheter ablation for atrial fibrillation with pulsed field ablation vs thermal energy ablation: A meta-analysis of single proportions.

Background: Pulsed field ablation (PFA) has emerged as a novel energy source for the ablation of atrial fibrillation (AF) using ultrarapid electrical pulses to induce cell death via electroporation. Objective: The purpose of this study was to compare the safety and acute efficacy of ablation for AF with PFA vs thermal energy sources. Methods: We performed an extensive literature search and systematic review of studies that evaluated the safety and efficacy of ablation for AF with PFA and compared them to landmark clinical trials for ablation of AF with thermal energy sources. Freeman-Tukey double arcsine transformation was used to establish variance of raw proportions followed by the inverse with the random-effects model to combine the transformed proportions and generate the pooled prevalence and 95% confidence interval (CI). Results: We included 24 studies for a total of 5203 patients who underwent AF ablation. Among these patients, 54.6% (n = 2842) underwent PFA and 45.4% (n = 2361) underwent thermal ablation. There were significantly fewer periprocedural complications in the PFA group (2.05%; 95% CI 0.94-3.46) compared to the thermal ablation group (7.75%; 95% CI 5.40-10.47) (P = .001). When comparing AF recurrence up to 1 year, there was a statistically insignificant trend toward a lower prevalence of recurrence in the PFA group (14.24%; 95% CI 6.97-23.35) compared to the thermal ablation group (25.98%; 95% CI 15.75-37.68) (P = .132). Conclusion: Based on the results of this meta-analysis, PFA was associated with lower rates of periprocedural complications and similar rates of acute procedural success and recurrent AF with up to 1 year of follow-up compared to ablation with thermal energy sources.

Characteristics and outcomes of recurrent atrial fibrillation after prior failed pulmonary vein isolation.

BACKGROUND: The mechanisms for atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) catheter ablation are unclear. Non-PV organized atrial arrhythmias (PAC, AT, macro-reentrant AFL) are possible contributors; however the prevalence and effect of their ablation on recurrent AF are unknown. We hypothesize that the identification and ablation of non-PV organized atrial arrhythmias were associated with less AF recurrence. METHODS: Patients who underwent repeat ablation for recurrent AF after prior PVI were retrospectively enrolled. The prevalence and characteristics of PV reconnections and non-PV organized atrial arrhythmias were identified. The outcomes of time to clinical AF recurrence, heart failure (HF) hospitalization, and mortality were analyzed in patients using multivariable adjusted Cox regression. RESULTS: In 74 patients with recurrent AF (age 66 ± 9 years, left atrial volume index 38 ± 10 ml/m2, 59% persistent AF), PV reconnections were found in 46 patients (61%), macro-reentrant atrial flutter in 27 patients (36%), and focal tachycardia in 12 patients (16%). Mapping and ablation of non-PV organized atrial arrhythmias were associated with a reduced recurrence of late clinical AF (adjusted HR 0.26, CI 0.08-0.85, p = 0.03) and the composite outcome of recurrence of late AF, HF hospitalization, and mortality (adjusted HR 0.38, CI 0.17-0.85, p = 0.02), with median follow-up of 1.6 (IQR 0.7-6.3) years. The presence of PV reconnections or empiric linear ablation was not associated with reduction in clinical AF or composite endpoints. CONCLUSION: The ablation of non-PV organized atrial arrhythmias resulted in a reduction of late clinical AF recurrence and composite outcome. In this challenging population, alternate mechanisms beyond PV reconnections need to be considered. Prospective studies are needed.

Ablation of mitral annular flutter ablation utilizing a left atrial anterior line versus a lateral mitral isthmus line: a systematic review and meta-analysis.

PURPOSE: Mitral annular flutter (MAF) is a common arrhythmia after atrial fibrillation ablation. We sought to compare the efficacy and safety of catheter ablation utilizing either a left atrial anterior wall (LAAW) line or a lateral mitral isthmus (LMI) line. METHODS: We performed a systematic review for all studies that compared LAAW versus LMI lines. Risk ratio (RR) and mean difference (MD) 95% confidence intervals were measured for dichotomous and continuous variables, respectively. RESULTS: Four studies with a total of 594 patients were included, one of which was a randomized control trial. In the LMI ablation group, 40% of patients required CS ablation. There were no significant differences in bidirectional block (RR 1.26; 95% CI, 0.94-1.69) or ablation time (MD -1.5; 95% CI, -6.11-3.11), but LAAW ablation was associated with longer ablation line length (MD 11.42; 95% CI, 10.69-12.14) and longer LAA activation delay (MD 67.68; 95% CI, 33.47-101.89.14) when compared to LMI. There was no significant difference in pericardial effusions (RR 0.36; 95% CI, 0.39-20.75) between groups and more patients were maintained sinus rhythm (RR 1.19; 95% CI, 1.03-1.37, p = 0.02) who underwent LAAW compared to LMI. CONCLUSION: Ablation of mitral annular flutter with a LAAW line compared to a LMI line showed no difference in rates of acute bidirectional block, ablation time, or pericardial effusion. However, LAAW ablation required a longer ablation line length, resulted in greater LAA activation delayed and was associated with more sinus rhythm maintenance, with the added advantage of avoiding ablation in the CS.

Association between early recurrences of atrial tachyarrhythmias and long-term outcomes in patients after repeat atrial fibrillation ablation.

PURPOSE: Early recurrence of atrial tachyarrhythmia (ER) is predictive of late recurrence of atrial tachyarrhythmia (LR) after first-time atrial fibrillation (AF) ablation, but the association in patients undergoing repeat AF ablation is unknown. We aim to determine the incidence and prognostic significance of ER after repeat ablation. METHODS: A total of 259 consecutive patients (mean age 64 years, 75.3% male) undergoing repeat AF ablation with complete follow-up data were included at a single institution from 2010 to 2015. ER and LR were defined as atrial tachyarrhythmia (AF, atrial flutter or atrial tachycardia) > 30 s within the 3-month blanking period (BP) and after the 3-month BP, respectively. RESULTS: ER occurred in 79/259 (30.5%), and LR occurred in 138/259 (53%) at a median follow-up of 1221 (IQR: 523-1712) days. Four-year freedom from LR was 22% and 56% in patients with and without ER, respectively (p < 0.001). After multivariate adjustment, ER was strongly associated with LR, cardioversion post BP, and repeat ablation, but not associated with hospitalization. Compared to those with no ER, there was a higher risk of LR when ER occurred within the first month of the BP [month 1: hazard ratio (HR) 2.32, confidence interval (CI) 1.57-3.74, p < 0.001; month 2: HR 2.01, CI 1.13-3.83, p = 0.02; month 3: HR 1.46, CI 0.5-3.36, p = 0.37], however the prediction of LR based on timing within the BP was poor (area under curve 0.64). CONCLUSION: Following repeat AF ablation, ER is strongly associated with LR, cardioversion post BP, and repeat ablation.

Forward-Solution Noninvasive Computational Arrhythmia Mapping: The VMAP Study.

BACKGROUND: The accuracy of noninvasive arrhythmia source localization using a forward-solution computational mapping system has not yet been evaluated in blinded, multicenter analysis. This study tested the hypothesis that a computational mapping system incorporating a comprehensive arrhythmia simulation library would provide accurate localization of the site-of-origin for atrial and ventricular arrhythmias and pacing using 12-lead ECG data when compared with the gold standard of invasive electrophysiology study and ablation. METHODS: The VMAP study (Vectorcardiographic Mapping of Arrhythmogenic Probability) was a blinded, multicenter evaluation with final data analysis performed by an independent core laboratory. Eligible episodes included atrial and ventricular: tachycardia, fibrillation, pacing, premature atrial and ventricular complexes, and orthodromic atrioventricular reentrant tachycardia. Mapping system results were compared with the gold standard site of successful ablation or pacing during electrophysiology study and ablation. Mapping time was assessed from time-stamped logs. Prespecified performance goals were used for statistical comparisons. RESULTS: A total of 255 episodes from 225 patients were enrolled from 4 centers. Regional accuracy for ventricular tachycardia and premature ventricular complexes in patients without significant structural heart disease (n=75, primary end point) was 98.7% (95% CI, 96.0%-100%; P<0.001 to reject predefined H0 <0.80). Regional accuracy for all episodes (secondary end point 1) was 96.9% (95% CI, 94.7%-99.0%; P<0.001 to reject predefined H0 <0.75). Accuracy for the exact or neighboring segment for all episodes (secondary end point 2) was 97.3% (95% CI, 95.2%-99.3%; P<0.001 to reject predefined H0 <0.70). Median spatial accuracy was 15 mm (n=255, interquartile range, 7-25 mm). The mapping process was completed in a median of 0.8 minutes (interquartile range, 0.4-1.4 minutes). CONCLUSIONS: Computational ECG mapping using a forward-solution approach exceeded prespecified accuracy goals for arrhythmia and pacing localization. Spatial accuracy analysis demonstrated clinically actionable results. This rapid, noninvasive mapping technology may facilitate catheter-based and noninvasive targeted arrhythmia therapies. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT04559061.

Predictors of unusual ECG characteristics in cavotricuspid isthmus-dependent atrial flutter ablation.

BACKGROUND: An unusual 12-lead electrocardiographic pattern may be present in patients with cavotricuspid isthmus (CTI)-dependent flutter. OBJECTIVE: Using baseline patient characteristics and echocardiography, we sought to study predictors of unusual electrocardiogram (ECG) characteristics in patients with CTI-dependent atrial flutter. METHODS: This was a dual-center, retrospective cohort study of 147 patients undergoing electrophysiology study and ablation for CTI-dependent atrial flutter. RESULTS: Among this cohort, 23 patients (16%) had unusual 12-lead ECG characteristics. Using multivariate logistic regression, we found two clinical predictors for having an unusual ECG pattern. A clockwise (CW) pattern at time of electrophysiology study was the strongest predictor of an unusual ECG pattern (odds ratio 15.3, 95% confidence interval [CI] 4.0-59.4, P < 0.005). In addition, patients with decreased systolic function had a 3.5 greater odds (95% CI 1.1-11.5, P = 0.037) of having an unusual ECG pattern. CONCLUSIONS: Our data demonstrate that among patients suffering from CTI-dependent atrial flutter who are referred for ablation, 16% will have unusual ECG patterns. Patients with CW atrial activation and left ventricle dysfunction have greater odds of manifesting unusual patterns by surface electrocardiogram.