Comparison of Atrial Remodeling Caused by Sustained Atrial Flutter Versus Atrial Fibrillation.

BACKGROUND: Atrial flutter (AFL) and atrial fibrillation (AF) are associated with AF-promoting atrial remodeling, but no experimental studies have addressed remodeling with sustained AFL. OBJECTIVES: This study aimed to define the atrial remodeling caused by sustained atrial flutter (AFL) and/or atrial fibrillation (AF). METHODS: Intercaval radiofrequency lesions created a substrate for sustained isthmus-dependent AFL, confirmed by endocavity mapping. Four groups (6 dogs per group) were followed for 3 weeks: sustained AFL; sustained AF (600 beats/min atrial tachypacing); AF superimposed on an AFL substrate (AF+AFLs); sinus rhythm (SR) with an AFL substrate (SR+AFLs; control group). All dogs had atrioventricular-node ablation and ventricular pacemakers at 80 beats/min to control ventricular rate. RESULTS: Monitoring confirmed spontaneous AFL maintenance >99% of the time in dogs with AFL. At terminal open-chest study, left-atrial (LA) effective refractory period was reduced similarly with AFL, AF+AFLs and AF, while AF vulnerability to extrastimuli increased in parallel. Induced AF duration increased significantly in AF+AFLs and AF, but not AFL. Dogs with AF+AFLs had shorter cycle lengths and substantial irregularity versus dogs with AFL. LA volume increased in AF+AFLs and AF, but not dogs with AFL, versus SR+AFLs. Optical mapping showed significant conduction slowing in AF+AFLs and AF but not AFL, paralleling atrial fibrosis and collagen-gene upregulation. Left-ventricular function did not change in any group. Transcriptomic analysis revealed substantial dysregulation of inflammatory and extracellular matrix-signaling pathways with AF and AF+ALs but not AFL. CONCLUSIONS: Sustained AFL causes atrial repolarization changes like those in AF but, unlike AF or AF+AFLs, does not induce structural remodeling. These results provide novel insights into AFL-induced remodeling and suggest that early intervention may be important to prevent irreversible fibrosis when AF intervenes in a patient with AFL.

Catheter Ablation Lesion Visualization With Intracardiac Strain Imaging in Canines and Humans.

Catheter ablation is a common treatment for arrhythmia, but can fail if lesion lines are noncontiguous. Identification of gaps and nontransmural lesions can reduce the likelihood of treatment failure and recurrent arrhythmia. Intracardiac myocardial elastography (IME) is a strain imaging technique that provides visualization of the lesion line. Estimation of lesion size and gap resolution were evaluated in an open-chest canine model ( n = 3 ), and clinical feasibility was investigated in patients undergoing ablation to treat typical cavotricuspid isthmus (CTI) atrial flutter ( n = 5 ). A lesion line consisting of three lesions and two gaps was generated on the canine left ventricle via epicardial ablation. One lesion was generated in one canine right ventricle. Average lesion and gap areas were measured with high agreement (33 ± 14 and 30 ± 15 mm2, respectively) when compared against gross pathology (34 ± 19 and 26 ± 11 mm2, respectively). Gaps as small as 11 mm2 (3.6 mm on epicardial surface) were identifiable. Absolute error and relative error in estimated lesion area were 9.3 ± 8.4 mm2 and 31% ± 34%; error in estimated gap area was 11 ± 9.0 mm2 and 40% ± 29%. Flutter patients were imaged throughout the procedure. Strain was shown to be capable of differentiating between baseline and after ablation completion as confirmed by conduction block. In all patients, strain decreased in the CTI after ablation (mean paired difference of -17% ± 11%, ). IME could potentially become a useful ablation monitoring tool in health facilities.

Open-Label Two-Dose Pilot Study of Landiolol for the Treatment of Atrial Fibrillation/Atrial Flutter in Caucasian Patients.

BACKGROUND: We investigated for the first time the suitability of landiolol, an ultra-short-acting ß1-specific ß-blocker, for the treatment of atrial fibrillation/atrial flutter (AF/AFL) in Caucasian patients.Methods and Results:The 20 study patients received landiolol as a continuous infusion (starting dose 40 µg/kg/min) with (B+CI) or without (CI) a preceding bolus dose (100 µg/kg/min administered over 1 min) in a prospective open-label study. The primary endpoint was the proportion of patients with sustained heart rate (HR) reduction ≥20% or to <90 beats/min within 16 min of starting the CI. Secondary endpoints were the pharmacodynamics, pharmacokinetics, AF/AFL symptoms, safety and tolerability of landiolol. At 16 min, HR was reduced in all patients treated with landiolol. The primary endpoint was met by 60% of patients in the CI group and 40% in the B+CI group without a significant group difference. Overall reduction of AF/AFL symptoms at 16 min was 72%. Safety and local tolerability of landiolol were excellent, and no serious adverse events occurred. CONCLUSIONS: Continuous infusion of landiolol with a starting dose of 40 µg/kg/min is suitable for the acute treatment of tachycardic AF/AFL in Caucasian patients. Administration of a preceding bolus seems unnecessary.

Inverse Correlation Between Left Atrial Appendage Function and CHA2DS2-VASc Score in Patients with Atrial Flutter.

Impaired left atrial appendage ejection fraction (LAA-EF) and peak LAA flow velocity (LAA-FV) are associated with high thromboembolic risks in patients with atrial fibrillation (AF). Herein, we examined LAA function among patients with atrial flutter (AFL) stratified by the CHA2DS2-VASc score using transesophageal echocardiography (TEE). Of 231 consecutive patients with typical AFL, 84 who fulfilled the inclusion criteria were enrolled. Among them, 57 had ongoing AFL and were divided into the isolated AFL (n = 38) and AFL with paroxysmal AF (PAF) (n = 19) groups, depending on whether they had sporadic AF before TEE. The remaining 27 patients with spontaneous sinus rhythm during TEE were designated as controls. Both the LAA-FV (31.9 cm/s vs. 51.5 cm/s, P = 0.004) and LAA-EF (28.4% vs. 36.5%, P = 0.024) measured during AFL were significantly lower in the AFL + PAF group than in the isolated AFL group. Significant inverse correlations between the CHA2DS2-VASc score and LAA-EF were identified in the AFL (P = 0.008) and AFL + PAF (P = 0.032) groups. We observed progressive LAA dysfunction in patients with AFL + PAF compared with that in patients with isolated AFL, and the LAA-EF was inversely correlated with the CHA2DS2-VASc score in these patients. Our findings may have implications on the application of thromboprophylactic therapy in patients with AFL.

Atrial flutter ablation by femoral approach in a woman with azygos continuation of an interrupted inferior vena cava and dual chamber pacemaker.

This report describes a case of isthmus-dependent atrial flutter ablation by the femoral approach in a 54-year-old woman with a previously unknown absence of the inferior vena cava (IVC) and dual chamber pacemaker. Despite looping of the catheters, ablation and termination of atrial flutter were performed successfully without function alteration of the pacemaker leads.  This is the first report of an inferior-to-superior approach for ablation of atrial flutter in the absence of the perihepatic IVC with the presence of chronic indwelling leads in the area targeted for radiofrequency.

Feasibility of Performing Radiofrequency Catheter Ablation and Endomyocardial Biopsy in the Same Setting.

In patients with unexplained cardiomyopathy, electroanatomical mapping can identify abnormal tissue to target during electrophysiology-guided endomyocardial biopsy (EP-guided EMB). The objective of this study is to determine whether catheter ablation performed in the same setting as EP-guided EMB increases procedural risk. Sixty-seven patients (mean age 54.4 ± 13.8, 57% male) undergoing EP-guided EMB were included. Radiofrequency catheter ablation was performed in 17 patients (25%) for ventricular arrhythmias and in 2 (3%) for typical atrial flutter. Femoral arterial access was obtained in 90% ablation patients and 40% biopsy-only patients; vascular access complications were more common in the ablation group than in the EMB-only group (p = 0.02). There were no significant differences in rate of tricuspid regurgitation, thromboembolism, or pericardial effusion, whether procedural anticoagulation was used. In conclusion, catheter ablation and procedural anticoagulation can be combined with EP-guided EMB with an increased risk of vascular access complications, but no significant increase in intracardiac complications.

Catheter ablation of atypical atrial flutter: a novel 3D anatomic mapping approach to quickly localize and terminate atypical atrial flutter.

PURPOSE: This study aims to describe a novel method of High Density Activation Sequence Mapping combined with Voltage Gradient Mapping Overlay (HD-VGM) to quickly localize and terminate atypical atrial flutter. METHODS: Twenty-one patients presenting with 26 different atypical atrial flutter circuits after a previous catheter or surgical AF ablation were studied. HD-VGM was performed with a commercially available impedance-based mapping system to locate and successfully ablate the critical isthmus of each tachycardia circuit. The results were compared to 21 consecutive historical control patients who had undergone an atypical flutter ablation without HD-VGM. RESULTS: Twenty-six different atypical flutter circuits were evaluated. An average 3D anatomic mapping time of 12.39 ± 4.71 min was needed to collect 2996 ± 690 total points and 1016 ± 172 used mapping points. A mean of 195 ± 75 s of radiofrequency (RF) energy was needed to terminate the arrhythmias. The mean procedure time was 135 ± 46 min. With a mean follow-up 16 ± 9 months, 90% are in normal rhythm. In comparison to the control cohort, the study cohort had a shorter procedure time (135 ± 46 vs. 210 ± 41 min, p = 0.0009), fluoroscopy time (8.5 ± 3.7 vs. 17.7 ± 7.7 min, p = 0.0021), and success in termination of the arrhythmia during the procedure (100 vs. 68.2%, p = 0.0230). CONCLUSIONS: Ablation of atypical atrial flutter is challenging and time consuming. This case series shows that HD-VGM mapping can quickly localize and terminate an atypical flutter circuit.

Cavotricuspid-Isthmus Dependent Flutter or Left-Sided Atrial Tachycardia?

A 52-year-old man with previous mitral valve replacement, cavotricuspid isthmus, and left-sided roof-line ablation for previous typical atrial flutter and tachycardia presented with recurrence of symptoms with an atrial tachycardia measuring 260 ms cycle length on electrocardiogram. Rhythmia electroanatomical mapping (Boston Scientific) was performed to understand the mechanism of arrhythmia and to guide ablative treatment.

Facial Drooping, Aphasia, and an Incidental Lung Mass in a Nonsmoker.

BACKGROUND: Atrial fibrillation and atrial flutter are atrial tachycardias associated with embolic strokes. To date, there have only been a few reports highlighting the incidence of these atrial tachycardias due to mechanical compression of myocardial structures and the pulmonary vasculature in certain mediastinal masses and cysts. CASE: We present a case of a 75-year-old gentleman who is a nonsmoker with a history of hypertension who presents with an acute embolic stroke due to atrial flutter likely from mechanical compression from an underlying squamous cell carcinoma of the lung. CONCLUSION: This case represents, to the best of our knowledge, a rare case of squamous cell carcinoma of the lung in a nonsmoker likely leading to mechanical compression and a resultant atrial tachycardia with an embolic stroke.

Anatomic characteristics of the mitral isthmus region: The left atrial appendage isthmus as a possible ablation target.

The mitral isthmus is a part of the postero-inferior area of the lateral left atrial wall located between the mitral annulus and the left inferior pulmonary vein ostium. Linear ablation lesions are created within the mitral isthmus for the invasive treatment of left atrial arrhythmias. However, the anatomy of this region is not fully understood. The aim of this study has been to provide a detailed morphometric description of the mitral isthmus region and to propose another possible isthmus within the investigated heart area that may serve as a potential new ablation target. Two hundred autopsied, non-atrial fibrillation hearts (23.5% deriving from females) whose donors were a mean of 47.6±17.6years old were investigated. We macroscopically assessed the anatomy of the postero-inferior area of the lateral left atrial wall. The mean mitral isthmus length was 28.8±7.0mm and was significantly longer than the left atrial appendage (LAA) isthmus (14.2±4.8mm) (p=.00). The distance between the LAA orifice and the left inferior pulmonary vein ostium (18.4±4.8mm) was longer than the LAA isthmus (p=.00) and shorter than the mitral isthmus (p=.00). The LAA isthmus was longer in hearts with a common left pulmonary vein (p=.037). In 65.5% of all cases the area between the right and left mitral isthmus lines was completely smooth. In the remaining hearts, crevices and diverticula (18.0%), intertrabecular recesses (7.0%), trabecular bridges (3.5%), or co-existence of these structures (6%) could be observed. The LAA isthmus line was smooth in 95.5% of all cases, with only small crevices in the remaining 4.5%. In conclusion, regardless of the anatomical variants of the left-sided pulmonary veins, the mitral isthmus area is quite uniform in size. The LAA isthmus is considerably shorter than the mitral isthmus. The mitral isthmus line has many unwanted structures that may entrap the catheter, which is not the case for the LAA isthmus. We proposed the LAA isthmus line for potential clinical use.

Development, Preclinical Validation, and Clinical Translation of a Cardiac Magnetic Resonance - Electrophysiology System With Active Catheter Tracking for Ablation of Cardiac Arrhythmia.

OBJECTIVES: This study sought to develop an actively tracked cardiac magnetic resonance-guided electrophysiology (CMR-EP) system and perform first-in-human clinical ablation procedures. BACKGROUND: CMR-EP offers high-resolution anatomy, arrhythmia substrate, and ablation lesion visualization in the absence of ionizing radiation. Implementation of active tracking, where catheter position is continuously transmitted in a manner analogous to electroanatomic mapping (EAM), is crucial for CMR-EP to take the step from theoretical technology to practical clinical tool. METHODS: The setup integrated a clinical 1.5-T scanner, an EP recording and ablation system, and a real-time image guidance platform with components undergoing ex vivo validation. The full system was assessed using a preclinical study (5 pigs), including mapping and ablation with histological validation. For the clinical study, 10 human subjects with typical atrial flutter (age 62 ± 15 years) underwent MR-guided cavotricuspid isthmus (CTI) ablation. RESULTS: The components of the CMR-EP system were safe (magnetically induced torque, radiofrequency heating) and effective in the CMR environment (location precision). Targeted radiofrequency ablation was performed in all animals and 9 (90%) humans. Seven patients had CTI ablation completed using CMR guidance alone; 2 patients required completion under fluoroscopy, with 2 late flutter recurrences. Acute and chronic CMR imaging demonstrated efficacious lesion formation, verified with histology in animals. Anatomic shape of the CTI was an independent predictor of procedural success. CONCLUSIONS: CMR-EP using active catheter tracking is safe and feasible. The CMR-EP setup provides an effective workflow and has the potential to change the way in which ablation procedures may be performed.

The influence of cavotricuspid isthmus length on total radiofrequency energy to cure right atrial flutter.

BACKGROUND AND AIM: The complexity and success rate of right atrial flutter ablation is highly dependent on anatomical structures. METHODS: The study comprised 35 consecutive patients (33-77 years old; 30 men) who underwent ablation of typical atrial flutter. The linear ablation line was measured offline as a surrogate for the cavotricuspid isthmus (CTI) length with the help of a three-dimensional mapping and navigation system (Ensite™). Biophysical parameters, such as total radiofrequency (RF) energy and time of the ablation procedure, were analysed to test the hypothesis that any of these variables show a correlation with the length of the ablation line. RESULTS: Bidirectional isthmus block was achieved in all cases. The isthmus length had a mean value of 32 ± 12 mm with a range of 14-57 mm. The linear regression between the CTI length and the total RF energy was not significant. There was no significant difference in energy (32.281 ± 25.587 vs. 37.136 ± 24.250 W-s, p = NS) or in the total ablation time (759 ± 646 vs. 802 ± 533 s, p = NS) between the group with short (< 29 mm; n = 17) vs. long CTI (≥ 29 mm, n = 18). When comparing different ablation technologies, total RF energy delivered with 8-mm catheter technology (group I) was significantly lower than in patients with cross over from 8-mm to cooled ablation technology (group III) (29.615 ± 12.331 vs. 62.674 ± 28.735 W-s, p = 0.01). The same was true for the comparison between cooled ablation technology (group II) and group III (19.879 ± 13.669 vs. 62.674 ± 28.735 W-s, p = 0.002). CONCLUSIONS: The length of the CTI as measured with help of a three-dimensional mapping system may reflect only a weak indicator for the complexity of flutter ablation procedures. The thickness of musculature and specific anatomy of the CTI seem to be the main challenges in performing a linear ablation to achieve bidirectional block.

Long-term Prognosis of Paroxysmal Atrial Fibrillation and Predictors for Progression to Persistnt or Chronic Atrial Fibrillation in the Korean Population.

Little is known about the long-term prognosis of or predictors for the different clinical types of atrial fibrillation (AF) in Korean populations. The aim of this study was to validate a risk stratification to assess the probability of AF progression from paroxysmal AF (PAF) to persistent AF (PeAF) or permanent AF. A total of 434 patients with PAF were consecutively enrolled (mean age; 71.7 ± 10.7 yr, 60.6% male). PeAF was defined as episodes that are sustained > 7 days and not self-terminating, while permanent AF was defined as an ongoing long-term episode. Atrial arrhythmia during follow-up was defined as atrial premature complex, atrial tachycardia, and atrial flutter. During a mean follow-up of 72.7 ± 58.3 months, 168 patients (38.7%) with PAF progressed to PeAF or permanent AF. The mean annual AF progression was 10.7% per year. In univariate analysis, age at diagnosis, body mass index, atrial arrhythmia during follow-up, left ventricular ejection fraction, concentric left ventricular hypertrophy, left atrial diameter (LAD), and severe mitral regurgitation (MR) were significantly associated with AF progression. In multivariate analysis, age at diagnosis (P = 0.009), atrial arrhythmia during follow-up (P = 0.015), LAD (P = 0.002) and MR grade (P = 0.026) were independent risk factors for AF progression. Patients with younger age at diagnosis, atrial arrhythmia during follow-up, larger left atrial chamber size, and severe MR grade are more likely to progress to PeAF or permanent AF, suggesting more intensive medical therapy with close clinical follow-up would be required in those patients.

A zero-fluoroscopy approach to cavotricuspid isthmus catheter ablation: comparative analysis of two electroanatomical mapping systems.

BACKGROUND: Electroanatomical mapping systems have reduced the amount of fluoroscopy required to ablate the cavotricuspid isthmus. The aims of this study are to evaluate the feasibility and safety of a zero-fluoroscopy approach to cavotricuspid isthmus catheter ablation using the Carto®3 system (Biosense Webster, Diamond Bar, CA, USA) and to compare the results of this approach with those of the zero-fluoroscopy approach using the Ensite-NavX™ system (St. Jude Medical, St. Paul, MN, USA). METHODS: Twenty consecutive procedures guided by the Carto®3 system (Group A) were compared with two case-control groups matched from 146 procedures guided with the Ensite-NavX™ system. Group B consisted of 20 matched procedures from the first 50 procedures performed in the electrophysiology unit, and Group C consisted of 20 matched procedures from the last 50 procedures. Acute success (bidirectional block), complications, and recurrences were analyzed. The procedure times were also compared. RESULTS: There were no differences in the rates of acute success (95%, 100%, and 100%, respectively), complications (0%, 5%, and 0%), and recurrences (5.2%, 0%, and 5%) in the three groups. A zero-fluoroscopy approach was attempted in all procedures, and electroanatomical mapping made it possible to successfully avoid fluoroscopy in 90% of the procedures in Group A, 85% in B, and 95% in C. The total procedure time was shorter in Group C. The fluoroscopy and radiofrequency times were not different. CONCLUSIONS: A zero-fluoroscopy approach to cavotricuspid isthmus catheter ablation using the Carto®3 system is feasible in most procedures. This approach has similar results to the zero-fluoroscopy approach using the Ensite-NavX™ system.

Counterclockwise heart rotation affects variation in successful ablation line position in common atrial flutter.

BACKGROUND: Linear ablation of atrial flutter usually targets a 6 o'clock position on the cavotricuspid isthmus on left anterior oblique view, but the difficulty of the ablation often requires a variation in successful ablation line position from 5 to 7 o'clock. METHODS AND RESULTS: This study included 94 patients without structural heart disease. A linear lesion was created in turn at the 6, 7, and 5 o'clock positions until bidirectional block of the isthmus was completed; the final lesion was defined as the successful ablation line. The degree of counterclockwise heart rotation (CCW-HR) was evaluated in a blinded fashion according to the angle between the vertical line crossing the His bundle catheter and the line connecting the His bundle catheter and coronary sinus ostium. Successful ablation lines were obtained at the 6 o'clock position in 59 patients (63%); the 7 o'clock position in 19 patients (20%; the oldest group with a moderate radiofrequency burden); and the 5 o'clock position in the remaining 16 (17%; the youngest group with the largest radiofrequency burden). Age-related increase in CCW-HR was the only independent predictor of a more septal successful ablation line (OR, 7.1; 95% CI: 3.3-14.3; P<0.01). CONCLUSIONS: Variation in successful ablation line position was affected by age-related CCW-HR; its evaluation might reduce radiofrequency burden, especially in the young and elderly.

Two-dimensional echocardiographic features of the inferior right atrial isthmus: the role of vestibular thickness in catheter ablation of atrial flutter.

OBJECTIVES: The aim of this study was to examine the feasibility of transthoracic two-dimensional (2D)-echocardiography in defining the cavo-tricuspid isthmus (CTI) anatomy and its value concerning the ease of catheter ablation of isthmic atrial flutter (AF). METHODS: CTI analysis was accomplished in 39 cases: 16 necropsy specimens and 23 patients. Sixteen were patients with isthmus-dependent AF and seven controls with other supraventricular re-entrant tachycardias. Two-dimensional transthoracic echocardiography and a right atrium angiogram were performed before radiofrequency catheter ablation (RFCA). RESULTS: The measurements of the CTI with angiography were compared with those taken with echocardiography and correlation was excellent (r= 0.91; P < 0.0001). In normal patients, the dimension of the vestibular thickness was successfully compared and validated with the histological examination of the necropsy specimens: histology median 6.8 mm, range 4.4-10.5 vs. echo median 6.2 mm, range 5.4-8.7; P: NS. Vestibular thickness was greater in complex than in simple RFCA (13.6 ± 1.9 mm vs. 10.0 ± 2.3 mm; P = 0.01). When vestibular thickness ≥11.5 mm, the ablation prone to be complex (sensitivity 83.3%, specificity 80%, positive predictive value 71.4%, and negative predictive value 88.9%). CONCLUSIONS: Two-dimensional transthoracic echocardiography clearly depicts the inferior isthmus and, displaying the thickness of the tricuspid vestibule, it was related with complexity of the ablation procedure in isthmus-dependent AF.