Cryoenergy Application Research Articles

Efficiency and safety in AF ablation using a novel loop-shaped cryoablation catheter

Abstract Background Different single shot ablation systems are under development to improve the efficiency and safety of pulmonary vein isolation for the treatment of atrial fibrillation (AF). Purpose Evaluation of effectiveness and safety of a novel cryoloop catheter (figure 1) for pulmonary vein isolation. Methods In a single centre prospective registry, patients with drug-refactory AF underwent pulmonary vein isolation (PVI) using a novel loop-shaped cryoablation catheter. For efficiency assessment the following parameters were registered: 1: the number of successfully isolated pulmonary veins (PV) confirmed by entrance- and exit block; 2: total procedure time, left atrial dwell time, total cryoablation time and applications as well as total fluoroscopy time; 3: freedom from atrial arrhythmia after 6 months. For safety assessment the following parameters were studied: 1: periinterventional adverse events like pericardial effusion, thromboembolic events and bleedings according to BARC classification; 2: endoscopic detected esophageal lesions (EDEL); 3: phrenic nerve palsy; 4: computed tomography angiography (CTA) detected PV stenosis until 6 months after PVI. Results In total, 25 subjects were enrolled in the current registry and received PVI with the loop-shaped cryoablation catheter. In terms of efficiency, successful acute PVI could be achieved in 91/100 treated PVs. Total procedure, atrial dwell, cryoablation and total fluoroscopy times were 130.5 ± 24.2 min, 101.4 ± 19.8 min, 40.8 ± 11.0 min and 22.5 ± 5.5 min, respectively. On average, 4.5 cryoenergy applications per PV were required for acute PVI. Out of the blanking period of 3 months, after 6 months 18/25 subjects (72%) were free from any atrial arrhythmia. With respect to safety, no pericardial effusion, thromboembolic event or bleeding complication occurred. 2/25 subjects experienced a transient phrenic nerve palsy. Additionally, no EDEL or PV stenosis could be detected. Conclusion The present single centre registry confirmed the effectiveness and safety of the novel loop-shaped cryoablation catheter for the treatment of atrial fibrillation.Figure 1: cryoloop catheter

Study of the Impact of the Patient Rhythm during Cryoballoon Ablation on the Acute Biophysical Parameters

Background: Pulmonary vein isolation by means of cryoballoon is a well-established way of treatment of atrial fibrillation. The aim of the study was to compare the acute cryoballoon biophysical parameters attained during energy applications to the individual pulmonary vein during sinus rhythm versus atrial fibrillation. Methods: 100 Patients who underwent their first-time PVI using second-generation cryoballoon for symptomatic and drug-refractory AF, between the beginning of March to end of August 2016, were initially screened. 61 patients with paroxysmal AF were included in the present study. 39 patients with persistent AF were excluded. No pre-procedural anatomical imaging was reported. Results: A total of 61 patients (male 80%, age 59.3 ± 13.4 years) were included in the present analysis. A total of 243 pulmonary veins were isolated with an average of 1.87 ± 1.14 cryo energy applications per individual vein. During cryo application, there were no significant differences between applications delivered during sinus rhythm or ongoing AF in the rate of temperature drop at 5 and 30 s, rate of warming at 5 s after freezing stop or achieved balloon nadir temperature. The same also was observed for both the balloon cooling rate and warming times. Conclusions: The present analysis shows no impact of the patient baseline rhythm at the time of energy application upon the acute balloon biophysical parameters in patients with normal sinus rhythm and those with ongoing atrial fibrillation using the second-generation cryoballoon.

Temperature-guided ablation with the second-generation cryoballoon for paroxysmal atrial fibrillation: 3-year follow-up in a multicenter experience.

A strategy based on the attainment of the specific parameter of - 40°C within the first 60s during cryoenergy applications in the setting of cryoballoon ablation (CB-A) without the use of an inner lumen mapping catheter (ILMC) (Achieve; Medtronic, USA) for the visualization of real-time recordings (RTR) has been previously described. The latter has proven to be very effective in guaranteeing freedom from atrial arrhythmias in patients affected by paroxysmal atrial fibrillation (PAF) at 1-year follow-up. The purpose of this retrospective observational study was to evaluate the clinical outcomes of this strategy in a multicenter experience on a long-term follow-up of 3years. A total of 192 patients having undergone CB ablation for paroxysmal AF (PAF) starting from September 2015 to November 2016 that underwent a temperature-guided approach were included. Mean procedural time was 68.77 ± 18.88. The mean number of freezes in the LSPV was 1.2 ± 0.4, 1.2 ± 0.4 in the LIPV, 1.1 ± 0.4 in the RSPV, and 1.2 ± 0.4 in the RIPV. Considering a blanking period of 3months, freedom from AF off-AAD was achieved in 77.6% (149/192) at mean 34.5 ± 5.5months and median 35.1months (IQR, 32.3-37.0months) follow-up after 1 procedure. A temperature-guided approach affords freedom from AF at a 3-year follow-up period in a large majority of patients affected by PAF having undergone a single CB-A procedure.

Biophysical properties, efficacy, and lesion characteristics of a new linear cryoablation catheter in a canine model

The cryoballoon (CB) catheter is an established tool for pulmonary vein isolation (PVI), but its use is limited for that purpose. The purpose of this study was to investigate the biophysical properties of a newly developed linear cryoablation catheter for creation of linear ablation lesions in an invivo model. Twenty-nine dogs (14 acutely ablated, 15 chronically followed) underwent cryoablation using the linear cryoablation catheter. Regions of interest included the cavotricuspid isthmus (CTI), mitral isthmus (MI), left atrial (LA) roof, and LA posterior wall in an acute study. Cryoablations for CTI and MI were performed in 14 atrial fibrillation animals after PVI and followed over 1 month in the chronic study. Tissue temperature during cryoablation was monitored using implanted thermocouples in the regions of interest. Gross and microscopic pathologic characteristics of the lesions were assessed. In acute animals, lesion length (transmurality) was CTI 34 ± 4 mm (89% ± 11%); MI 29 ± 4 mm (90% ± 13%); LA roof 19 ± 3 mm (90% ± 8%); and LA posterior wall 19 ± 2 mm (81% ± 13%), with 1 or 2 freezes. Chronic bidirectional block was achieved in 13 of 14 CTI (93%) and 10 of 14 MI (71%) ablations after 1-month follow-up and was consistent with lesion continuity and transmurality upon pathology. The lowest tissue temperature correlated well with the closest distance to the linear cryocatheter (r = 0.688; P <.001). This linear cryocatheter created continuous and transmural linear lesions with "single-shot" cryoenergy application and has the potential for clinical use in the setting of various arrhythmias.

The influence of epicardial and endocardial use of cryoenergy on the completeness of lesions in surgical ablation of atrial fibrillation.

IntroductionCryoenergy is the most commonly used method of lesion formation in patients who have undergone surgical ablation of atrial fibrillation. Despite frequent use, the clinical effect of cryoenergy in endocardial and epicardial approaches is unknown.AimTo compare the effect of various cryoenergy applications on the postoperative incidence of sinus rhythm and completeness of lesions performed.Material and methodsA total of 55 patients underwent concomitant atrial fibrillation surgical ablation using cryoenergy under various conditions: epicardially during cardiac arrest, epicardially on beating heart, and endocardially. In the postoperative period, patients were invited to attend an electrophysiological examination to assess the completeness of surgical ablation lesions and, if necessary, to complete catheter ablation.ResultsTwenty-four patients underwent epicardial ablation on the arrested heart (group 1), 12 patients underwent epicardial ablation on the beating heart (group 2), and 19 patients underwent endocardial ablation (group 3). In the electrophysiological examination, sinus rhythm was present in 71% vs. 83% vs. 89% of patients, respectively. The completeness of pulmonary vein isolation was confirmed in 31% vs. 25% vs. 95% of patients, complete box lesions in 15% vs. 0% vs. 79% of patients, respectively.ConclusionsDespite the similar clinical effect of surgical ablation in all three approaches, the morphologically most effective use of cryoenergy is endocardial ablation. This approach has a very good result. Our findings further support the endocardial use of cryoenergy during surgical ablation of atrial fibrillation.

Japan ablation registry: cryoablation in atrioventricular nodal reentrant tachycardia (“JARCANRET study”): results from large multicenter retrospective investigation

Cryoenergy has been demonstrated to be a safe alternative to radiofrequency ablation for catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT). This study aimed to evaluate the safety and efficacy of cryoablation in patients with AVNRT. A multicenter retrospective study was performed. Two hundred eighty-three consecutive patients with AVNRT underwent cryoablation. Cryomapping at - 30°C and - 80°C was performed to predict cryoablation outcome and ascertain antegrade conduction. Cryoenergy was delivered subsequently at the same spot (cryoablation at - 80°C) for 240s. Ablation procedure was acutely successful in 281 out of 283 patients (99.3%). Of note, 22 patients (10.1%) had transient AV block during the cryoablation, but no injurious effects on AV conduction were provoked during cryomapping. During a follow-up period of 367 ± 35days, the recurrence rate was 3.9% (11 out of 281). There were no significant differences among the patients with a complete elimination of slow pathway conduction, AH jump without an echo beat, and AH jump with a single echo beat, in terms of the long-term recurrence of AVNRT. Cryoablation of AVNRT appears to be effective both acutely and during the long-term with a minimal risk of unwanted injuries to the conduction system. It seems to be important to monitor the antegrade conduction during cryoenergy applications, even when cryomapping demonstrates a safe location for cryoablation. The recurrence rate of AVNRT did not differ according to the properties of the residual slow pathway conduction.

Double cryoenergy application (freeze-thaw-freeze) at growing myocardium: Lesion volume and effects on coronary arteries late after energy application. Implications for efficacy and safety in pediatric patients.

Cryoenergy is accepted as an alternative to radiofrequency ablation (RFA) in childen for ablation of supraventricular tachycardia substrates. Single cryoenergy application has been shown to be inferior to RFA. Double cryoenergy application has therefore been introduced into clinical practice, but experience concerning efficacy is limited. Coronary artery stenosis has been reported as serious complication after RFA for arrhythmia substrates but not after single cryoablation. The purpose of the study was to assess lesion volume (efficacy) and risk of coronary artery damage (safety), late, that is, 6 months, after double cryoenergy application in a piglet model. Two sequential cycles of cryoenergy were delivered at -75°C for 4 minutes at the atrioventricular groove in five piglets. Animals were restudied after 6 months by coronary angiography and intracoronary ultrasound (ICUS). Ablation lesions were examined histologically and lesion volume was determined by three-dimensional morphometric analysis. Cryolesion volume was 174.04 ± 67.18 mm3 for atrial and 238.69 ± 112.1 mm3 for ventricular lesions (P > .05). Ventricular lesions, 4.06 ± 1.05 mm, were significantly deeper than atrial lesions, 3.58 ± 0.78 mm, (P < .05). In two of the 29 lesions, cryoenergy induced minor coronary artery injury with mild medial and adventitial thickening as well as minimal intimal proliferation, which had neither been detected by coronary angiography nor by ICUS. Late after double cryoenergy application at growing myocardium, subclinical minor affection of the coronary artery wall could be detected with minimal intimal proliferation. As lifetime sequelae of this finding remains unknown, further studies are warranted to address safety of repeated cycles of cryoenergy application for tachycardia substrates in children.

Safety and Efficacy of Cryoablation in Patients With Ventricular Arrhythmias Originating From the Para-Hisian Region

This study aimed to assess the outcome of cryoablation in patients with ventricular arrhythmias (VAs) originating from the para-Hisian region. There are few data regarding the outcome of cryoablation in patients with VAs originating from the para-Hisian region, where there is the risk of injury to the conduction system. The study analyzed all patients undergoing cryoablation at the Mayo Clinic (Rochester, Minnesota) as part of an ablation for VAs originating from the para-Hisian region. The study population consisted of 10 patients (64 ± 15 years of age, 7 men). Cryoenergy was applied after an unsuccessful radiofrequency (RF) ablation in 8 (80%) patients. The VAs were successfully ablated with cryoablation in 7(70%) patients; RF ablation after an unsuccessful cryoablation eliminated the VAs at almost the same location with careful monitoring in 1 patient. The authors could not ablate the actual focus because a transient atrioventricular block developed during cryo- and RF energy applications, which led to an unsuccessful ablation in the remaining 2 patients. Acomplete atrioventricular block occurred during the cryoenergy application in 1 patient, who needed a permanent pacemaker implantation. There were no VA recurrences in 4 of 8 (50%) patients with procedural success during a median follow-up period of 122 days (interquartile range: 43 to 574 days). Cryoablation is clinically effective in some patients with VAs originating from the para-Hisian region, where there is the risk of injury to the conduction system, and therefore should be considered as an alternative to or inaddition to RF ablation in these cases. Cryoablation requires care because it can also lead to major complications.

Effects of Triple Cryoenergy Application on Lesion Formation and Coronary Arteries in the Developing Myocardium.

To improve long-term outcome after cryoablation of substrates of supraventricular tachycardia, application of two and three consecutive freeze-thaw cycles has been performed. The effect of triple freeze-thaw cycles on lesion formation within developing myocardium and coronary arteries, however, has not been studied yet. In eight piglets (mean age 15 weeks, weight 15-20kg), 30 cryolesions (three consecutive freeze-thaw cycles) were applied to the atrial aspect of both AV valve annuli (n = 18) as well as to ventricular myocardium below the valves (n = 12). Coronary angiography was performed before and after cryoenergy application. The animals were reevaluated by coronary angiography and intracoronary ultrasound (ICUS) after 48h. All hearts were removed for histological examination of the lesions subsequently. After staining (hematoxylin-eosin, desmin immunohistochemistry), lesions was measured by planimetry with a digital virtual miscroscope analysis system and volumes of the cryolesions were calculated. Mean atrial lesion volume was 190.68 ± 167.53 mm3 (n = 18), and mean ventricular lesion volume was 184.34 ± 107.42 mm3 (n = 12). Compared with previously reported data on lesion volumes after single and double freeze-thaw cycles, lesions were significantly larger. Coronary arteries were unaffected on coronary angiography as well as on ICUS. No affection of coronary arteries was found on histological examination. Application of three consecutive freeze-thaw cycles resulted in increased lesion volume compared with single and double freeze-thaw cycles. No affection of the coronary arteries was evident. To evaluate the clinical benefit and safety of triple cryoenergy application for catheter ablation, prospective randomized trials are required.

Second-generation cryoballoon ablation without the use of real-time recordings: A novel strategy based on a temperature-guided approach to ablation

The achievement of -40°C within the first 60 seconds during cryoenergy applications has proven to independently predict durable pulmonary vein (PV) isolation in the setting of second-generation cryoballoon (CB-A; Medtronic, Minneapolis, MN) ablation. We sought to evaluate a strategy based on the attainment of the specific parameter of -40°C within the first 60 seconds during cryoenergy applications in the setting of CB-A ablation without the use of an inner lumen mapping catheter (Achieve, Medtronic) for the visualization of real-time recordings. A total of 52 patients having undergone CB ablation for paroxysmal atrial fibrillation (AF) between 1 February 2015 and 30 June 2015 who underwent a temperature-guided approach based on achieving -40°C within 60 seconds without real-time recordings (wire group) were compared with a cohort of 52 propensity score-matched patients having undergone CB ablation performed with an inner lumen mapping catheter (Achieve group). All PVs were checked for electrical isolation at the end of the procedure with a circular mapping catheter in the wire group. Electrical isolation could be obtained in all patients in the Achieve group and in 99% of PVs in the wire group. Freedom from AF without antiarrhythmic drugs at a mean follow-up of 12.4 ± 3.0 months did not significantly differ between both groups (85% vs 88%, respectively; P = .56). A temperature-guided approach based on achieving -40°C within 60 seconds is effective in producing PV isolation and affords freedom from AF at 12-month follow-up in 85% of patients affected by paroxysmal AF after a 3-month blanking period.

Cryoballoon ablation of persistent atrial fibrillation: feasibility and safety of left atrial roof ablation with generation of conduction block in addition to antral pulmonary vein isolation.

Although the generation of linear lesions by ablation improves success rates in patients with persistent atrial fibrillation (AF), the procedure has been considered unsuitable for cryoablation balloon catheter technologies. We developed a technique for linear ablations, using second-generation cryoballoon technology. This was a single-arm, prospective study in 76 patients with persistent AF treated consecutively at our centre. Cryoablation was performed using a 28 mm second-generation cryoballoon. The first cryoenergy application was performed in close proximity to the position during isolation of the left superior pulmonary vein (PV). Sequential overlapping freezes were applied along the left atrial (LA) roof by slight clockwise rotation of the sheath in combination with slight retraction of the sheath and incremental advancement of the cryoballoon, until reaching the original position for right superior PV isolation. The acute endpoint was the creation of a roofline, defined as complete conduction block across the LA roof >120 ms and ascending activation across the posterior LA wall. Acute success in roofline generation was achieved in 88% of patients, applying on average five (median 4-6) freezes with nadir temperature of -40°C (-36 to -44°C). In five patients, conduction block could not be achieved. No phrenic nerve injuries occurred during roofline generation. Generation of linear roofline lesions is possible with the second-generation cryoballoon. The technique can be used in combination with PV isolation to treat persistent AF with good acute success rates, short procedure times, and acceptable safety concerns. If validated by further studies, the method would be an appealing alternative to radiofrequency ablation techniques.

Incidence of Significant Delayed Esophageal Temperature Drop After Cryoballoon-Based Pulmonary Vein Isolation.

The second-generation cryoballoon (CB2) has demonstrated superior clinical outcome. Potential procedural complications include esophageal thermal lesions due to excessive esophageal temperature (ET). Safety cut-offs for the ET have previously been published. A safety margin was incorporated due to a delayed esophageal temperature decline even after termination of the CB2 freeze cycle. The extent of these delayed temperature drops requires further systematic evaluation. The study enrolled 29 patients with paroxysmal or shortstanding persistent AF who underwent CB2-based PVI. Freeze cycle duration was 240 seconds. No bonus freeze was applied after successful PVI. The intraluminal ET was continuously measured via a transorally inserted probe (SensiTherm, St. Jude Medical, Inc.). The CB2 temperature and ET were recorded throughout the procedure using a camera setup. The mean number of freeze cycles per patient was 4.3 ± 2. A total of 147 cryoenergy applications were analyzed. A delayed decline in ET of >0.5 °C was recorded following termination of 23.1% of freeze cycles. The maximum drop in delayed ET was 6.4 °C. Excessive esophageal cooling during the freeze cycle exceeding 8.5 °C/min may result in ET ≤10 °C. Following termination of cryoenergy delivery, the ET may decline an additional 6.4 °C. Proposed ET safety cut-offs during CB2-based PVI need to account for a significant ET drop that may occur even after termination of the individual freeze cycle.

Effects of Triple Cryoenergy Application on Early Lesion Formation and Coronary Arteries in the Developing Myocardium

Objectives: Cryoenergy is an alternative energy source for the ablation of substrates of supraventricular tachycardias. Though acute procedural success rate is equal and procedural safety is higher compared with radiofrequency ablation, long-term success rates are lower with cryoenergy. To improve acute and long-term outcome, the application of two and recently three consecutive freeze-thaw cycles has been performed. The effect of triple freeze-thaw cycles on lesion formation and coronary arteries, however, has not been studied systematically yet.

Phrenic nerve injury during ablation with the second-generation cryoballoon: analysis of the temperature drop behaviour in a large cohort of patients.

The present study sought to analyse the relationship between the temperature drop during the cryoenergy application and the occurrence of phrenic nerve injury (PNI) in a large cohort of patients having undergone second-generation cryoballoon ablation (CB-A). The first 550 consecutive patients having undergone CB-A for atrial fibrillation were enrolled. Attained temperatures at 20, 30, 40, and 60 s during cryoablation in the right-sided pulmonary veins (PVs) were collected. Diagnosis of PNI was made if reduced motility or paralysis of the hemidiaphragm was detected. The incidence of PNI in the study population was 7.3% (40/550); among them, only four (0.7%) did not resolve until discharge and one (0.2%) still persisted at 23 months. Patients with PNI exhibited significantly lower temperatures at 20, 30, and 40 s after the beginning of the cryoapplication in the right superior PV (RSPV) (P = 0.006, P = 0.003, and P = 0.003, respectively). The temperature drop expressed as Δ temperature/Δ time was also significantly higher in patients with PNI. Low temperature during the early phases of the freezing cycle (less than -38°C at 40 s) predicted PNI with a sensitivity of 80.5%, a specificity of 77%, and a negative predictive value of 97.9%. Among patients with a fast temperature drop during RSPV ablation, an RSPV diameter >23.55 × 17.95 mm significantly predicted PNI occurrence. The analysis of the temperature course within the first 40 s after the initiation of the freezing cycle showed that the temperature dropped significantly faster in patients with PNI during ablation in the RSPV.

Real time assessment of pulmonary vein isolation using the novel Achieve mapping catheter during cryoablation

Purpose: The Achieve inner lumen mapping catheter can be used with the cryoballoon to assess real-time isolation of pulmonary vein (PV) during cryoablation and to act as a supporting guidewire during balloon positioning. We sought to analyze the feasibility of this novel catheter and to assess real-time PV isolation during cryoablation. Methods: Patients undergoing 28-mm cryoballoon PVI using the Achieve catheter were included from two centers. Each application lasted 5 min. Real-time PV recording during freezing and time to PV isolation were analyzed. Lastly, the number of applications needed to achieve PV isolation was investigated. Results: 68 pts (47 male; 61±10 yo) were included. Averaged procedure duration and fluoroscopy times were 118±24 min and 29±10 min. During the first application, PV potentials could be detected during freezing in 95.2%, 75.0%, 81.5% and 31.2% of the left superior (LSPV), left inferior (LIPV), right superior (RSPV) and right inferior (RIPV) PVs, respectively. When PV potentials were detected, they appeared in 5±2, 4±2, 4±2, and 3±2 dipoles in and the first cryoenergy application was successful in 68.7%, 82.8%, 80.0% and 90.6% of the LSPVs, LIPVs, RSPVs, and RIPVs, respectively. PV deconnection occurred at -38.4±8.8°C/54.5±34.8sec, -33.3±10.5/46.9±30.4sec, -34.4±12.1/44.4±30.5sec and –37.4±18.0/52.7±27.1sec for the the LSPVs, LIPVs, RSPVs, and RIPVs, respectively. At the end of the procedure, 100% of the PVs were isolated after 1.2±0.6 applications (from 1 to 4). Conclusion: Cryoablation in conjunction with the novel Achieve catheter is feasible, leading to high acute PV isolation rates. Real-time PV recording during freezing can be performed in most of the left PVs and the RSPVs while recording of RIPV potentials is harder due to stability issues.

Double Cryoenergy Application (Freeze‐Thaw‐Freeze) at Growing Myocardium: Lesion Volume and Effects on Coronary Arteries Early After Energy Application. Implications for Efficacy and Safety in Pediatric Patients

Data on radiofrequency current application (RFA) at growing myocardium suggest that coronary artery stenosis may occur with a low incidence. Cryoenergy has emerged as an effective alternative to RFA. Although already used in clinical practice, experience with cryoenergy is low due to lack of data concerning effects of a modified double cryoenergy application, a freeze-thaw-freeze cycle, at growing myocardium. Purpose of the study was to assess lesion volume (efficacy) and risk of coronary artery damage (safety) early, 48hours, after modified double cryoenergy application in a piglet model. In 5 piglets, following selective coronary angiography, two sequential cycles of cryoenergy were delivered at -75 °C for 4 minutes, interrupted by thawing for one minute, at the atrioventricular groove. Piglets were restudied after 48hours by coronary angiography and intracoronary ultrasound (ICUS). Ablation lesions were examined morphologically and lesion volume was determined by 3-dimensional morphometric analysis. Lesion volume was 109.21± 39.61mm(3) for atrial and 150.30± 53.21mm(3) (P= 0.02) for ventricular lesions. Lesion depth was not significantly different for atrial, 3.07± 1.08mm, versus ventricular lesions, 3.56± 1.3mm. Cryoenergy induced minor coronary artery damage with medial and adventitial necrosis but a preserved intimal layer was present in 2/31 lesions, which had not been detected by coronary angiography or ICUS. Early after double cryoenergy application, subclinical minor changes of the coronary artery wall could be detected occasionally whereas the intimal layer remained intact. These findings may have implications on efficacy and safety when cryoenergy is applied for tachycardia substrates in pediatric patients.

Luminal esophageal temperature predicts esophageal lesions after second-generation cryoballoon pulmonary vein isolation

The novel second-generation cryoballoon (CB) facilitates pulmonary vein isolation (PVI) by improved surface cooling. The impact of this redesign on collateral damage is unknown. To investigate the incidence of esophageal lesions after PVI using the second-generation CB and the role of luminal esophageal temperature (LET) measurement as a predictor of lesion formation. Thirty-two consecutive patients underwent PVI using the second-generation 28 mm CB. Target application time was 2 × 240 seconds. Ninety-two percent of the PVs were isolated after 1 cryoenergy application. Complete PVI was achieved in all patients. LET with 3 thermocouples was continuously measured during cryoenergy application. Freezing was interrupted only if weakening/loss of phrenic nerve function or low LET (<5 °C) was observed. The lowest measured LET was-12 °C (despite cryoapplication interruption). Postprocedural gastroesophagoscopy was performed after 1-3 days in all patients and showed lesions in 6 of 32 (19%) patients. A minimum LET of≤12 °C predicted esophageal lesions with 100% sensitivity and 92% specificity (area under the receiver-operator characteristic curve 0.97; 95% CI 0.93-1.02; P = .001). Persistent phrenic nerve palsy occurred in 2 (6%) patients during ablation at the right inferior pulmonary vein. Repeat gastroesophagoscopy confirmed healing of lesions after 16 ± 14 days. Second-generation 28 mm CB PVI is associated with significant esophageal cooling, resulting in lesion formation in 19% of the patients. LET measurement accurately predicts lesion formation and may enhance the safety of the novel device.

Cryoballoon Pulmonary Vein Isolation Supported by Intracardiac Echocardiography: Integration of a Nonfluoroscopic Imaging Technique in Atrial Fibrillation Ablation

cryoballoon ablation has been adopted for pulmonary vein (PV) isolation (PVI) in many centers. Complete occlusion of PV by an adequately sized balloon is crucial for effectiveness of cryoenergy delivery. The aim of this study was to evaluate intracardiac echocardiography (ICE) as an alternative imaging technique compared to angiographic imaging in cryoballoon PVI. a total of 75 PVs were treated in 22 patients (61 ± 13 years, 17 male) undergoing PV cryoballoon ablation for drug refractory paroxysmal atrial fibrillation. Decision for an adequate balloon size was based on diameters of the PV antra assessed by ICE and PV angiography. Per PV 2.4 ± 0.4 cryoenergy pulses were applied. Decision for the balloon size was similar either based upon angiography or on ICE. A single 23 or 28 mm balloon was chosen in 10 and 3 patients, respectively. Two different sized balloons were used in 9 patients. PVI was evaluated after 2 cryoenergy applications. Total occlusion of the PV confirmed by ICE color flow Doppler (CFD) during ablation predicted successful PVI in 70 of 75 (93%) and unsuccessful PVI in 8 of 8 (100%). PV flow registered by pulsed wave Doppler at the PV ostium pre- and postablation was 0.48 ± 0.10 and 0.51 ± 0.12 m/s, respectively (n.s.). PVI was finally confirmed by entrance block in all PVs. No procedural complications occurred. ICE is a feasible novel imaging technique in cryoballoon ablation procedures. It allows decision for adequate balloon size, exact balloon placement, prediction of acute ablation success, and excludes acute narrowing of PV ostia.

Cryoablation at Growing Myocardium: No Evidence of Coronary Artery Obstruction or Intimal Plaque Formation Early and Late after Energy Application

Animal studies and clinical observations have demonstrated that radiofrequency current application at growing myocardium may result in coronary artery obstruction. Recently, cryoenergy has emerged as an effective alternative to radiofrequency ablation of arrhythmogenic substrates in pediatric patients. Up to now, there has been a lack of experimental data concerning the effects of cryoenergy application at growing myocardium. During general anesthesia, selective coronary angiography of the right and left coronary artery was performed in 10 piglets (age: 6 weeks, body weight: 14-18 kg). Subsequently, cryoenergy was delivered at -75 degrees C for 4 minutes using a 7-F catheter with a 6-mm-tip electrode at the atrial aspect of the tricuspid valve annulus in a posterior and lateral position. Additional cryoenergy lesions were induced via a retrograde approach at the lateral and posterior atrial and ventricular aspect of the mitral valve annulus, respectively. Five animals were restudied after 48 hours by coronary angiography and intracoronary ultrasound and in the remaining five piglets after 3 and 6 months, respectively. Selective coronary angiography and intracoronary ultrasound studies did not demonstrate any evidence for coronary artery obstruction after 48 hours, 3 months, or 6 months after cryoenergy application. In addition, histological examinations of the cryolesions after 48 hours and after 6 months did not demonstrate any intimal proliferations of the coronary arteries, respectively. By means of the present study, we did not observe any affection of the coronary arteries after cryoenergy application at growing myocardium in young piglets.

Esophageal Contour Changes during Cryoablation of Atrial Fibrillation

We have observed contour changes of the barium-filled esophagus during atrial fibrillation (AF) ablation with cryo-energy delivered in direct proximity to the esophagus. To evaluate the frequency, location, and severity of esophageal contour changes during cryo-energy application close to the esophagus. We retrospectively analyzed cine-fluoroscopic images acquired during hybrid cryo-radiofrequency AF ablation in 100 consecutive patients with cryo-energy delivered only in direct proximity to the esophagus. Esophageal contour changes were observed in 28 (32%) of 89 patients (and 74 [6.2%] of 1,191 of all cryo applications). They were more frequent in the left common pulmonary vein (PV) (50%) and less so in the right common PV and the upper PVs (4-5%). The distance of the ablation catheter from the endoesophageal contour prior to cryo-energy applications associated with contour changes was 1.8 +/- 1.5 mm, which increased to 4.1 +/- 1.6 mm at the time of peak contour change (P < 0.001). The esophageal contour deformation was 2.3 +/- 0.9 mm. There were no apparent complications related to cryo-energy application for 3-4 minutes, even if associated with contour changes. Esophageal contour changes were observed in >6% of cryo applications in direct proximity to the esophagus (32% of patients) and were most frequent in the posterior aspect of the left common and right lower PV ostium when cryo-energy was delivered at a distance of <or=5 mm from the esophageal contrast silhouette. No overt esophageal injury occurred. However, the safety of cryo-energy application in direct proximity to the esophagus remains to be further confirmed.