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.

Successful Noninvasive 12-Lead ECG Mapping-Guided Radiotherapy of Inaccessible Ventricular Tachycardia Substrate Due to Mechanical Valves.

In patients presenting with refractory ventricular tachycardia (VT) and aortic and mitral mechanical prosthetic valves, traditional catheter ablation is challenging. We describe a case in which a novel noninvasive computational electrocardiogram mapping algorithm localized VT sources originating from substrate near the mechanical valves, in which stereotactic ablative radiotherapy eliminated VT in 1.5-year follow-up. (Level of Difficulty: Advanced.).

Combined pulsed field ablation with ultra-low temperature cryoablation: A preclinical experience.

BACKGROUND: Combining pulsed field ablation (PFA) with ultra-low temperature cryoablation (ULTC) represents a novel energy source which may create more transmural cardiac lesions. We sought to assess the feasibility of lesions created by combined cryoablation and pulsed field ablation (PFCA) versus PFA alone. METHODS: Ablations were performed using a custom PFA generator, ULTC console, and an ablation catheter with insertable stylets. PFA was delivered in a biphasic, bipolar train. PFCA precooled the tissue for 30 s followed by a concurrent PFA train. Benchtop testing using Schlieren imaging and microbubble volume assessment were used to compare PFA and PFCA. PFA and PFCA lesions using pre-optimized and optimized ablation protocols were studied in 6 swine. Pre and post-ECGs were recorded for each ablation and a gross necropsy was performed at 14 days. RESULTS: Consistent with benchtop comparisons of heat and microbubble generation, PFA deliveries in the animals were accompanied by muscle contractions and significant microbubbles (Grade 2-3) visible on intracardiac echo while neither occurred during PFCA at higher voltage levels. Both PFA and PFCA acutely eliminated or highly attenuated (>80%) local atrial electrograms. Histology of PFA and PFCA lesions indicated depth up to 6-7 mm and nearly all lesions were transmural. Optimized PFCA produced wider cavotricuspid isthmus lesions with evidence of tissue selectivity. CONCLUSION: A novel technology combining PFA and ULTC into one energy source demonstrated in-vivo feasibility for PFCA ablation. PFCA had a more favorable thermal profile and did not produce muscle contraction or microbubbles while extending lesion depth beyond cryoablation.

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.

Computational ECG mapping and respiratory gating to optimize stereotactic ablative radiotherapy workflow for refractory ventricular tachycardia.

BACKGROUND: Stereotactic ablative radiotherapy (SAbR) is an emerging therapy for refractory ventricular tachycardia (VT). However, the current workflow is complicated, and the precision and safety in patients with significant cardiorespiratory motion and VT targets near the stomach may be suboptimal. OBJECTIVE: We hypothesized that automated 12-lead electrocardiogram (ECG) mapping and respiratory-gated therapy may improve the ease and precision of SAbR planning and facilitate safe radiation delivery in patients with refractory VT. METHODS: Consecutive patients with refractory VT were studied at 2 hospitals. VT exit sites were localized using a 3-D computational ECG algorithm noninvasively and compared to available prior invasive mapping. Radiotherapy (25 Gy) was delivered at end-expiration when cardiac respiratory motion was ≥0.6 cm or targets were ≤2 cm from the stomach. RESULTS: In 6 patients (ejection fraction 29% ± 13%), 4.2 ± 2.3 VT morphologies per patient were mapped. Overall, 7 out of 7 computational ECG mappings (100%) colocalized to the identical cardiac segment when prior invasive electrophysiology study was available. Respiratory gating was associated with smaller planning target volumes compared to nongated volumes (71 ± 7 vs 153 ± 35 cc, P < .01). In 2 patients with inferior wall VT targets close to the stomach (6 mm proximity) or significant respiratory motion (22 mm excursion), no GI complications were observed at 9- and 12-month follow-up. Implantable cardioverter-defibrillator shocks decreased from 23 ± 12 shocks/patient to 0.67 ± 1.0 (P < .001) post-SAbR at 6.0 ± 4.9 months follow-up. CONCLUSIONS: A workflow including computational ECG mapping and protocol-guided respiratory gating is feasible, is safe, and may improve the ease of SAbR planning. Studies to validate this workflow in larger populations are required.

Fasciculoventricular and atrioventricular accessory pathways in patients with Danon disease and preexcitation: A multicenter experience.

BACKGROUND: Studies have suggested that a fasciculoventricular pathway (FVP) may be the cause of preexcitation in patients with Danon disease, a rare X-linked dominant genetic disorder of hypertrophic cardiomyopathy. OBJECTIVE: The purpose of this study was to describe the prevalence of ventricular preexcitation on resting 12-lead electrocardiogram (ECG) in patients with Danon disease and the electrophysiological study (EPS) results of those with preexcitation. METHODS: Patients with confirmed Danon disease diagnosed with preexcitation (PR ≤120 ms, delta wave, QRS >110 ms) on ECG were included from a multicenter registry. The incidence of arrhythmias, implantable cardioverter-defibrillator (ICD) procedures, ICD shocks, and EPS results were collected. RESULTS: Thirteen of 40 patients (32.5%) with Danon disease were found to have preexcitation (mean age 17.3 years; 38% women). EPS performed in 9 of 13 patients (69%) demonstrated FVP only in 2 (22.2%), extranodal pathway without exclusion of FVP in 2 (22.2%), and both FVP and extranodal pathway in 5 (55.6%). Two patients had malignant accessory pathway (AP) properties. Over median follow-up of 842 days (interquartile range 138-1678), 11 patients (85%) had ICD placement, and 6 (46.1%) underwent heart transplantation. No patients required therapy for ventricular tachycardia, and 2 patients (15%) had paroxysmal atrial fibrillation. CONCLUSION: In a large multicenter cohort of patients with Danon disease, there was a high prevalence of FVP and extranodal pathways diagnosed on EPS in those with preexcitation. These findings suggest patients with preexcitation and Danon disease should undergo EPS to assess for FVP and potentially malignant extranodal AP.

Alternating wide complex tachycardia after surgical aortic valve replacement.

A 51-year-old male developed recurrent episodes of palpitations and pre-syncope after surgical aortic valve replacement. Electrocardiograms after surgery revealed a wide complex tachycardia with alternating left bundle branch and right bundle branch block morphologies. An electrophysiology study (EPS) demonstrated typical bundle branch reentry ventricular tachycardia (BBRVT) treated successfully with right bundle ablation. We demonstrate the key diagnostic features of BBRVT on EPS, describe the circuit of BBRVT with explanation of the HV pseudointerval, and highlight the association of BBRVT and valve replacement.

Effect of closed loop stimulation versus accelerometer on outcomes with cardiac resynchronization therapy: the CLASS trial.

PURPOSE: Chronotropic incompetence (CI) in patients with heart failure is common and associated with impaired exercise intolerance and adverse outcomes. This study sought to determine the effects of closed loop stimulation (CLS) rate-adaptive pacing on functional capacity in patients with heart failure with reduced ejection fraction (HFrEF) and CI implanted with cardiac resynchronization therapy (CRT) devices. METHODS: A randomized, blinded, cross-over designed trial enrolled patients with HFrEF and CI implanted with a Biotronik CRT-D to complete a quality of life questionnaire, 6-min walk distance (6MWD), and cardiopulmonary exercise testing after two programmed periods: 1-week period of CLS and 1-week period of standard accelerometer (DDDR). RESULTS: Nine patients (6 males, mean age 71.4 years, 7 with New York Heart Association Class III, mean ejection fraction 39 ± 8%) were enrolled. Quality of life trended higher in CLS as compared to DDDR (550.8 ± 123.9 vs 489.3 ± 164.9, p = 0.06). There were no differences between CLS and DDDR in 6MWD (293.1 ± 90.2 m vs 315.1 ± 95.5 m, p = 0.52), peak heart rate (HR) 110.7 ± 14.7 bpm vs 109.7 bpm ± 14.1, p = 0.67), or peak VO2 (12.3 ± 4.9 ml/kg/min vs 12.9 ± 5.9, p = 0.47). As tests were submaximal as indicated by low respiratory exchange ratios (0.98 ± 0.11 vs 1.0 ± 0.8, p = 0.35), VE/VCO2 slope also showed no difference between CLS and DDDR (35.8 ± 5.6 vs 35.4 ± 5.7, p = 0.65). Five patients (56%) preferred CLS programming (p = 1.0). CONCLUSIONS: In patients with HFrEF and CI implanted with a CRT-D, peak HR, peak VO2, and 6MWD were equivalent, while there was a trend toward improved quality of life in CLS as compared to DDDR. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT02693262.

Meta-analysis of the Usefulness of Catheter Ablation of Atrial Fibrillation in Patients With Heart Failure With Preserved Ejection Fraction.

Catheter ablation improves clinical outcomes in atrial fibrillation (AF) patients with heart failure (HF) with reduced ejection fraction (HFrEF). However, the role of catheter ablation in HF with a preserved ejection fraction (HFpEF) is less clear. We performed a literature search and systematic review of studies that compared AF recurrence at one year after catheter ablation of AF in patients with HFpEF versus those with HFrEF. Risk ratio (RR; where a RR <1.0 favors the HFpEF group) and mean difference (MD; where MD <0 favors the HFpEF group) 95% confidence intervals (CI) were measured for dichotomous and continuous variables, respectively. Six studies with a total of 1,505 patients were included, of which 764 (51%) had HFpEF and 741 (49%) had HFrEF. Patients with HFpEF experienced similar recurrence of AF 1 year after ablation on or off antiarrhythmic drugs compared with those with HFrEF (RR 1.01; 95% CI 0.76, 1.35). Fluoroscopy time was significantly shorter in the HFpEF group (MD -5.42; 95% CI -8.51, -2.34), but there was no significant difference in procedure time (MD 1.74; 95% CI -11.89, 15.37) or periprocedural adverse events between groups (RR 0.84; 95% CI 0.54,1.32). There was no significant difference in hospitalizations between groups (MD 1.18; 95% CI 0.90, 1.55), but HFpEF patients experienced significantly less mortality (MD 0.41; 95% CI 0.18, 0.94). In conclusion, based on the results of this meta-analysis, catheter ablation of AF in patients with HFpEF appears as safe and efficacious in maintaining sinus rhythm as in those with HFrEF.

Procedural Patterns and Safety of Atrial Fibrillation Ablation: Findings From Get With The Guidelines-Atrial Fibrillation.

BACKGROUND: Catheter ablation is an increasingly used treatment for symptomatic atrial fibrillation (AF). However, there are limited prospective, nationwide data on patient selection and procedural characteristics. This study describes patient characteristics, techniques, treatment patterns, and safety outcomes of patients undergoing AF ablation. METHODS: A total of 3139 patients undergoing AF ablation between 2016 and 2018 in the Get With The Guidelines-Atrial Fibrillation registry from 24 US centers were included. Patient demographics, medical history, procedural details, and complications were abstracted. Differences between paroxysmal and patients with persistent AF were compared using Pearson χ2 and Wilcoxon rank-sum tests. RESULTS: Patients undergoing AF ablation were predominantly male (63.9%) and White (93.2%) with a median age of 65. Hypertension was the most common comorbidity (67.6%), and patients with persistent AF had more comorbidities than patients with paroxysmal AF. Drug refractory, paroxysmal AF was the most common ablation indication (class I, 53.6%) followed by drug refractory, persistent AF (class I, 41.8%). Radiofrequency ablation with contact force sensing was the most common ablation modality (70.5%); 23.7% of patients underwent cryoballoon ablation. Pulmonary vein isolation was performed in 94.6% of de novo ablations; the most common adjunctive lesions included left atrial roof or posterior/inferior lines, and cavotricuspid isthmus ablation. Complications were uncommon (5.1%) and were life-threatening in 0.7% of cases. CONCLUSIONS: More than 98% of AF ablations among participating sites are performed for class I or class IIA indications. Contact force-guided radiofrequency ablation is the dominant technique and pulmonary vein isolation the principal lesion set. In-hospital complications are uncommon and rarely life-threatening.

Ventricular Tachycardia Storm Originating From Moderator Band Requiring Extracorporeal Membrane Oxygenation.

A 67-year-old man presented with dizziness secondary to ventricular tachycardia (VT) originating from the moderator band. The VT was refractory to multiple antiarrhythmic medications requiring extracorporeal membrane oxygenation and eventual curative ablation. We highlight a malignant form of idiopathic VT, unique electrocardiogram characteristics, and ablation considerations. (Level of Difficulty: Intermediate.).

Randomized controlled trial of Amigo® robotically controlled versus manually controlled ablation of the cavo-tricuspid isthmus using a contact force ablation catheter.

BACKGROUND: Radiofrequency catheter ablation (RFCA) of the cavo-tricuspid isthmus (CTI) is a common treatment for atrial flutter (AFL). However, achieving bi-directional CTI conduction block may be difficult, partly due to catheter instability. OBJECTIVE: To evaluate the safety and efficacy of the Amigo® Remote Catheter System (RCS) compared to manual catheter manipulation, during CTI ablation for AFL. METHODS: Fifty patients (pts) were prospectively randomized to robotically (25 pts) versus manually (25 pts) controlled catheter manipulation during CTI ablation, using a force-contact sensing, irrigated ablation catheter. The primary outcome was recurrence of CTI conduction after a 30-min waiting period. Secondary outcomes included total ablation, procedure, and fluoroscopy times, contact force measurement, and catheter stability. RESULTS: Recurrence of CTI conduction 30 min after ablation was less with robotically (0/25) versus manually (6/25) controlled ablation (p = 0.023). Total ablation and procedure times to achieve persistent CTI block (6.7 ± 3 vs. 7.4 ± 2.5 min and 14.9 ± 7.5 vs. 15.2 ± 7 min, respectively) were not significantly different (p = 0.35 and p = 0.91, respectively). There was a non-significant trend toward a greater force time integral (FTI in gm/s) with robotically versus manually controlled CTI ablation (571 ± 278 vs. 471 ± 179, p = 0.13). Fluoroscopy time was longer with robotically versus manually controlled CTI ablation (6.8 ± 4.4 min vs. 3.8 ± 2.3 min, p = 0.0027). There were no complications in either group. CONCLUSION: Robotically controlled CTI ablation resulted in fewer acute recurrences of CTI conduction compared to manually controlled CTI ablation, and a trend toward higher FTI. The longer fluoroscopy time during robotically controlled ablation was likely due to a steep learning curve. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT02467179.

Compatibility of Radiofrequency Surgical Sponge Detection Technology with Cardiac Implantable Electronic Devices and Temporary Pacemakers.

BACKGROUND: Radiofrequency (RF) technology has improved detection of retained surgical sponges with a reported 100% sensitivity and specificity. However, the potential for interactions of the RF signals emitted by the detection system with cardiac implantable electronic devices (CIEDs) or temporary pacemakers may limit its use in those patients with these devices. This study investigated whether RF detection technology causes interference or clinically significant changes in the programmed settings of implanted pacemakers and defibrillators or temporary epicardial pacemakers. METHODS: Fifty patients who were scheduled either for CIED removal or placement of a temporary epicardial pacemaker (at the time of open heart surgery) were recruited for this study. Device settings and measurements from separate interrogations before and after scanning with the RF detection system were compared. For the temporary pacemakers, we observed for any changes in hemodynamics or signs of pacing interference. RESULTS: Twenty (40%) pacemakers, 20 (40%) implantable cardioverter defibrillators, and 10 (20%) temporary pacemakers were analyzed in this study. During scanning, no signal interference was detected in any permanent device, and there were no significant changes in programmed settings after scanning with the RF detection system. However, pacing inhibition was detected with temporary pacing systems when programmed to a synchronous mode (DDD). CONCLUSIONS: RF detection technology can be safely used to scan for retained surgical sponges in patients with permanent CIEDs and temporary pacemakers set to asynchronous mode.

Clinical Outcomes of Cardiac Resynchronization with Epicardial Left Ventricular Lead.

BACKGROUND: Left ventricular (LV) pacing in cardiac resynchronization therapy (CRT) can be achieved via a transvenous or epicardial route. A surgically implanted epicardial LV (eLV) lead is used after a standard transvenous LV (tLV) lead implantation has failed. However, studies of clinical outcomes in patients with eLV leads and comparisons of outcome between tLV and eLV-CRT are sparse. Therefore, the purpose of this study is to compare clinical response between tLV-CRT and eLV-CRT, as well as to understand the differences within the eLV-CRT population. METHODS: Forty-four patients received eLV-CRT following unsuccessful attempts of tLV-CRT implantation between 2002 and 2013 at the University of California, San Diego (UCSD) and Mayo Clinics. These patients were matched for age, gender, and etiology of cardiomyopathy in a 1:2 ratio with a cohort of patients who received tLV-CRT during the same time period. RESULTS: During a mean follow-up of 57 months, similar clinical outcomes and survival rate were noted between tLV and eLV-CRT patients (all P > 0.05). Within the eLV-CRT group, dilated cardiomyopathy patients had significant improvement in New York Heart Association class and ejection fraction (both P < 0.05), while ischemic cardiomyopathy patients did not (both P > 0.05). eLV-CRT patients with nonanterior lead location had significantly improved survival (P < 0.001). There was also a trend for improved survival in those with nonapical lead location (P = 0.09). CONCLUSION: In this case-matched two-centered study, comparable improvements were noted in patients with tLV-CRT and eLV-CRT. Operators should target nonanterior and nonapical locations during eLV-CRT implantation. Use of eLV-CRT should be considered a viable alternative for CRT candidates.

Evaluation of the safety and effectiveness of the CryoMedix cryoablation catheter system for the treatment of atrial flutter and fibrillation.

BACKGROUND: Catheter ablation of atrial flutter and fibrillation (AFL and AF) has typically been performed with radiofrequency energy. Cryoablation has recently been used for AF and AFL, but its success has been limited by the nadir temperature achievable using nitrous oxide as a refrigerant. In this study, a novel approach allowing for use of a liquid refrigerant capable of achieving lower nadir temperatures was tested in a canine model with cavo-tricuspid isthmus (CTI) and left atrial (LA) ablation. METHODS AND RESULTS: In six dogs, under general anesthesia, standard catheters were placed in the coronary sinus and right ventricular apex, and the CryoMedix cryoablation catheter (CAC) in the right (CTI) and left atrium (for ablation, across the LA roof, mitral isthmus, and LA septum). Double-freezes up to 2 min each were performed, with a 30-s thaw cycle between freezes. Ablated areas were subsequently grossly inspected and photographed and tissues fixed in formalin for histologic analysis to determine if the lesions were contiguous and transmural. In all animals, long linear (from 4-8 cm) transmural atrial lesions were observed on gross and histological examination in the left atrial roof, septum and mitral isthmus, and across the cavo-trisucpid isthmus. In all animals, bi-directional cavo-tricuspid isthmus block was observed after ablation, during pacing from the coronary sinus ostium and low lateral right atrium, respectively. Up to 50% thickness lesions were observed in the right ventricle below the tricuspid valve in all animals. There were no acute complications noted in any animals. CONCLUSIONS: The CAC system produces extremely negative freezing temperatures, significantly lower than those reported for nitrous oxide based systems. The CTI was easily ablated with the CAC system, producing bi-directional conduction block, suggesting a potential role for the system in the treatment of isthmus-dependent atrial flutter. Transmural LA lesions were also produced with the CAC system, suggesting a potential role in treating AF.

Recovery of mitral isthmus conduction leads to the development of macro-reentrant tachycardia after left atrial linear ablation for atrial fibrillation.

BACKGROUND: Left atrial linear ablation for atrial fibrillation (AF) may be proarrhythmic, leading to left atrial macro-reentrant tachycardia (LAT). Whether due to failure to achieve block initially or to recovery of conduction after ablation is unknown. This study was designed to evaluate the frequency of recovery of mitral isthmus (MI) conduction compared with cavo-tricuspid isthmus (CTI) conduction, and the relationship between recovery of MI conduction and postablation LAT. METHODS AND RESULTS: Of 163 patients with AF who underwent circumferential pulmonary vein ablation plus left atrial linear ablation, in whom MI and CTI ablation produced bidirectional conduction block, 52 underwent repeat ablation for recurrent atrial arrhythmias (AF or LAT). Of these 52 patients, coronary sinus ablation was required in 48 to achieve bidirectional MI block at the index ablation. During repeat ablation, MI and CTI conduction was assessed in sinus rhythm. At repeat ablation, MI conduction had recovered in 38 of 52 patients, as compared with CTI conduction which recovered in only 12 of 52 patients (P=0.001). At repeat ablation, the recurrent clinical arrhythmia in 12 patients was MI-dependent LAT. Recovery of MI conduction was associated with development of MI-dependent LAT (P=0.01). CONCLUSIONS: Despite using bidirectional conduction block as a procedural end point, recovery of MI conduction is common and may lead to LAT after left atrial linear ablation for AF. The reason for greater recovery of MI versus CTI conduction is unknown but could be due to differences in isthmus anatomy or lower power used for ablation in the left versus right atrium.

Determinants of lesion dimensions during transcatheter microwave ablation.

BACKGROUND: Transcatheter microwave ablation is a novel technique for treating cardiac arrhythmias. METHODS: We investigated the effects of catheter temperature, application duration, and antenna length on lesion dimensions during catheter-based microwave ablation. In a swine thigh muscle preparation, microwave was delivered at targeted temperatures of 60 degrees C (n = 18), 70 degrees C (n = 27), 80 degrees C (n = 43), or 90 degrees C (n = 18) for 120 seconds with 10-mm antenna; and at targeted temperatures of 80 degrees C for 120 seconds (n = 22), 150 seconds (n = 18), 180 seconds (n = 18), 210 seconds (n = 18), and 240 seconds (n = 17) with 20-mm antenna using 10 F catheter (MedWaves, San Diego, CA, USA) during parallel orientation. Conventional radiofrequency ablation (RF) using a 4-mm tip electrode was performed as control. RESULTS: With 120-second energy applications, lesion length and depth were significantly larger with targeted temperatures of 80 degrees C and 90 degrees C than 60 degrees C (P< 0.05). Furthermore, lesion depth and width, but not length, were significantly increased by prolonging energy application duration from 120 to 240 seconds at targeted temperature of 80 degrees C (P< 0.05). Compared to RF, microwave lesions were significantly longer but had comparable depth and width. A 20-mm microwave antenna produced longer lesions than either a 10-mm antenna or RF ablation catheter. Multivariate analysis demonstrated that targeted temperature >or=80 degrees C, application duration >or=150 seconds, and use of 20-mm antenna were independent predictors for lesion depth and width (P< 0.05). Surface dessication was observed in 4/18 (22%) lesions at 90 degrees C, as compared with 1/136 (0.7%) at 80 degrees C targeted tip temperature (P < 0.05). CONCLUSIONS: This study demonstrated that lesions size with transcatheter microwave ablation can be controlled by adjusting targeted temperature, energy application duration, and antenna length. A targeted temperature of 80 degrees C for more than 150 seconds should provide optimal lesion dimensions and lower risk of surface dessication or charring.

Acute and long-term efficacy and safety of catheter cryoablation of the cavotricuspid isthmus for treatment of type 1 atrial flutter.

BACKGROUND: Atrial flutter (AFL) is commonly treated by radiofrequency catheter ablation. Catheter-based cryoablation may be an effective alternative with potential advantages. OBJECTIVE: The purpose of this study was to study the acute and long-term safety and efficacy of catheter-based cryoablation for treatment of cavotricuspid isthmus-dependent (typical and reverse typical) AFL. METHODS: Catheter-based cryoablation was performed with a 10Fr catheter in 160 patients with cavotricuspid isthmus-dependent AFL (122 men and 38 women; mean age 63.1 +/- 9.3 years, mean left ventricular ejection fraction 54.6% +/- 10.4%); 94 (58.8%) of these patients also had atrial fibrillation (AF). All patients underwent right atrial (RA) activation mapping and pacing at the cavotricuspid isthmus to demonstrate concealed entrainment and confirm cavotricuspid isthmus dependence of AFL. Catheter-based cryoablation of the cavotricuspid isthmus was performed with multiple freezes (average freeze time 2.3 +/- 0.5 minutes) until bidirectional block was demonstrated during pacing from the low lateral RA and coronary sinus, respectively. Patients were evaluated at 1, 3, and 6 months and underwent weekly and symptomatic event monitoring. Acute procedural success was defined as cavotricuspid isthmus block persisting 30 minutes after ablation. Long-term success was defined as absence of AFL during follow-up. RESULTS: Acute success was achieved in 140 (87.5%) of 160 patients. Total procedure time was 200 +/- 71 minutes, ablation time (including a 30-minute waiting period after ablation) was 139 +/- 62 minutes, and fluoroscopy time was 35 +/- 26 minutes. An average of 20.5 +/- 11.3 freezes, for a total ablation time of 47.4 +/- 24.3 minutes, were required to achieve cavotricuspid isthmus block, with average and nadir temperatures of -81.5 degrees C +/- 3.7 degrees C and -85.6 degrees +/- 3.6 degrees C, respectively. Four patients (2.5%) had procedure-related adverse events. Of 132 patients with acute efficacy who completed 6-month follow-up, 8 (6%) were lost to follow-up or were noncompliant with event recordings. Using survival analysis, 106 (80.3%) remained free of AFL on strict analysis of event recordings only, and 119 (90.2%) remained clinically free of AFL. CONCLUSION: This large pivotal study demonstrated the acute and long-term efficacy and safety of catheter-based cryoablation for cavotricuspid isthmus-dependent AFL, similar to rates previously reported for radiofrequency catheter ablation.

Preliminary results with percutaneous transcatheter microwave ablation of typical atrial flutter.

BACKGROUND: Linear microwave ablation has been shown to be effective for treatment of atrial fibrillation during open-heart surgery by producing transmural lesions in the atrium to isolate the pulmonary veins. However, the safety and efficacy of percutaneous, transcatheter, linear microwave ablation for atrial arrhythmias, while demonstrated in animal models, is unknown in humans. Therefore, we studied the safety and efficacy of linear microwave ablation of the cavotricuspid isthmus (CTI) in humans with typical atrial flutter, utilizing a 2-cm long microwave antenna mounted on a steerable 9-French catheter. METHODS AND RESULTS: In seven consecutive patients, multielectrode catheters were positioned at the His bundle (quadripolar) and around the TV annulus (duo-decapolar) for pacing and recording atrial activation sequence before and after ablation. The microwave antenna was withdrawn gradually from tricuspid annulus towards inferior vena cava to ablate the CTI. Intracardiac ultrasound was used to ensure adequate endocardial contact of the microwave ablation catheter with the CTI. Microwave energy was applied at a power of 18 to 21 W at each ablation point for 120 seconds. Ablation was repeated until bidirectional CTI block was confirmed by demonstrating a descending activation wavefront in the contralateral atrial wall during pacing from the coronary sinus ostium or low lateral right atrium, respectively. Bidirectional isthmus block was achieved in all patients, after a mean number of 27.4 +/- 14.7 energy applications per patients. There were no acute procedural complications. CONCLUSIONS: Percutaneous, transcatheter microwave ablation of CTI dependent atrial flutter was demonstrated to be safe and effective in this preliminary feasibility study.