Safety and Feasibility of Cryothermal Ablation Within the Mid‐ and Distal Coronary Sinus

Coronary Spasm Due to Pulsed Field Ablation: A State-of-the-Art Review

With the ever-growing population of patients undergoing cardiac ablation with pulsed electric fields, there is a need to understand secondary effects from the therapy. Coronary artery spasm is one such effect that has recently emerged as the subject of further investigation in electrophysiology literature. This review aims to elucidate the basic anatomy underlying vascular spasm due to pulsed electric fields and the effects of irreversible electroporation on coronary arteries. This review also aims to gather the current preclinical and clinical data regarding the physiology and function of coronary arteries following electroporation.

Catheter Ablation of Coronary Sinus Accessory Pathways in the Young

BACKGROUND

Accessory atrioventricular pathways (AP) are the most common tachycardia substrate for supraventricular tachycardia (SVT) in the young. Endocardial catheter ablation of AP may be unsuccessful in up to 5% due to a coronary sinus location.

OBJECTIVE

Data on ablation of accessory pathways within the coronary venous system (CVS) in the young is sparse.

METHODS

Analysis of feasibility, outcome, and safety in patients ≤18 years with coronary sinus accessory pathways (CS-AP) and catheter ablation via CVS in a tertiary pediatric electrophysiological referral center (05/2003-12/2021). Control group adjusted for age, weight, and pathway location was established from patients of the prospective European Multicenter Pediatric Ablation Registry who all had endocardial AP ablation.

RESULTS

24 individuals had mapping and intended AP ablation within the CVS (age: 2.7-17.3 years, body weight: 15.0-72.0 kg). Due to proximity to coronary artery, ablation was withheld in 2/24. Overall procedural success was achieved in 20/22 (90.9%) study patients and in 46/48 (95.8%) controls. Coronary artery injury after RF ablation was noted in 2/22 (9%) study patients and in 1/48 (2%) controls. In CVS patients repeat SVT occurred in 5/22 (23%) during a median follow-up of 8.5 years, 4/5 underwent reablation resulting in 94.4% overall success. Controls were free from SVT during follow-up of 12 months as defined by registry protocol.

CONCLUSIONS

Success of CS-AP ablation in the young was comparable to endocardial AP-ablation. Substantial risk of coronary artery injury should be considered when CS-AP ablation is performed in the young.

Ultralow temperature cryoablation using near-critical nitrogen for cavotricuspid isthmus-ablation, first-in-human results

INTRODUCTION

Cryoablation has evolved as a safe alternative to radiofrequency ablation in the treatment of several supraventricular arrhythmias and has potential advantages, yet is limited by the properties of the cryogen used. We investigated a novel ultralow temperature cryoablation (ULTC) system using nitrogen near its liquid-vapor critical point as a freezing source, achieving temperatures as low as -196 degrees Celsius in a long linear catheter with a continuous energy release. Initial safety, procedural and efficacy outcomes of ULTC are described in patients undergoing cavotricuspid isthmus (CTI) ablation.

METHODS AND RESULTS

The Cryocure studies (NCT02355106, NCT02839304) are prospective, single-arm, multi-center, first-in-human clinical studies in 17 patients with atrial flutter (AFL) and 13 patients with atrial fibrillation (AF). A total of 30 patients, mean age 65 ± 8 years old and 67% male, were enrolled and underwent ablation of the CTI. Acute success, defined as the confirmation of stable bidirectional conduction block across the CTI, was achieved in all 30 patients. After 12 months of follow-up, 14 out of 17 AFL patients remained free from any AFL. One (3.3%) procedure-related but not device-related serious adverse event was reported, involving transient inferolateral ST-elevation associated with temporary AV conduction block.

CONCLUSION

In this first-in-human clinical study the safety and performance results demonstrate the capabilities of ultralow temperature near-critical nitrogen as an effective energy source for CTI ablation. Ongoing, larger, studies should confirm our findings and evaluate the capabilities to create linear and focal transmural lesions in other arrhythmias.

Cryoablation of atrioventricular nodal re-entrant tachycardia: 7-year follow-up in 515 patients-confirmed safety but very late recurrences occur

Aims

Cryoablation is an alternative method to radiofrequency ablation for treatment of atrioventricular nodal re-entrant tachycardia (AVNRT). This study investigates the long-term safety and efficacy of cryoablation in AVNRT.

Methods and results

We studied 515 consecutive patients (317 women, mean age 50 years, range 13-89 years) undergoing a first cryoablation for AVNRT between 2003 and 2008. Ablations were performed with a 6-mm Freezor Xtra catheter. Six patients were acute failures; 494 out of 509 (97%) primarily successfully ablated patients were followed up for a mean of 7.1 years (range 2-12 years). About 11% (54/494 patients) of patients had recurrences of the index arrhythmia. Time to recurrence varied from days to 9 years; 14 patients (3%) had recurrences later than 2 years, 8 patients (2%) later than 3 years, and 6 patients (2%) later than 4 years. Recurrence rate was higher in patients with slow-slow or fast-slow AVNRT (n = 24) compared with the common slow-fast variant (25 vs. 10%; P = 0.04). Recurrence rate was not higher in patients with residual slow pathway conduction (jump with or without echo beat, n = 199, 39%). Transient atrioventricular (AV) block of the first-, second-, or third-degree during ablation was observed in 45 patients but had no impact on the risk of AVNRT recurrence. No late AV block occurred. Single vs. multiple applications or total amount of cryoenergy delivered did not differ between patients with and without recurrences.

Conclusion

Cryoablation in AVNRT is safe with a long-term efficacy of 88%; however, very late recurrences occur.

[Cryoablation: Clinical applications in cardiac electrophysiology from their biophysical bases]

Cryoablation is an energy alternative to radiofrequency for ablation of various arrhythmias, where its unique biophysical properties offer a greater safety profile. Since its first use for the surgical treatment of different arrhythmias until its conceptualization in the current technical transcatheter, cryoablation has proven not to be only a safe source of energy, but also an effective source in the long-term. While the radiofrequency has been the energy most used for isolation of pulmonary veins in atrial fibrillation ablation, technological advances in cryoballon have managed to simplify the procedure without sacrificing its effectiveness. Cryoablation has been widely used for arrhythmias located in high-risk locations, such as the ablation of the atrioventricular nodal reentrant tachycardia and septal accessory pathways, due to its theoretical null risk of complete AV block. This review intends to give the clinical applications of the cryothermy through a thorough understanding of their biophysical basis.

Risk of Coronary Artery Injury With Radiofrequency Ablation and Cryoablation of Epicardial Posteroseptal Accessory Pathways Within the Coronary Venous System

Background—

Ablation of epicardial posteroseptal accessory pathways requires ablation within the coronary venous system. We assessed the risk of coronary artery (CA) injury with radiofrequency ablation (RFA) within the coronary venous system as a function of the distance between the CA and ablation site. We also examined the efficacy and safety of cryoablation close to a CA.

Methods and Results—

Two-hundred forty patients underwent ablation for epicardial posteroseptal accessory pathways. Coronary angiography was performed before ablation in the last 169 patients and was repeated after ablation if performed in the coronary venous system within 5 mm of a significant CA. The distance between the ideal ablation site and closest CA was <2 mm in 100 (59%), 3 to 5 mm in 28 (16%), and >5 mm in 41 of 169 (25%) patients. CA injury was observed in 11 of 22 (50%) and 1 of 15 (7%) patients when RFA was performed within 2 and 3 to 5 mm of a CA, respectively. Cryoablation was performed in 26 patients with a significant CA located within 5 mm. Cryoablation alone eliminated epicardial posteroseptal accessory pathway conduction in 17 of 26 (65%) patients and in 8 patients with additional RFA without CA narrowing in any patient. During a follow-up period of 3 to 6 months, single procedure success rates were 90% and 77% for RFA and cryoablation at the ideal site, respectively.

Conclusions—

The risk of CA injury with RFA is correlated inversely with the distance from the ablation site. Cryoablation is a safe and reasonably effective alternative when a significant CA is located close to the ideal ablation site.

Transcatheter mapping and ablation of arrhythmias in the coronary sinus

The coronary sinus (CS) is a complex structure of particular interest to cardiac electrophysiologists. It is exploited as an anatomical reference, a site to record left-sided atrial and ventricular signals and for cardiac resynchronization therapy. Perhaps less appreciated, it may itself serve as a substrate for arrhythmias. It is now increasingly recognized that arrhythmias may be targeted by transcatheter ablation within the CS. This review summarizes pertinent anatomic considerations, explores the relationship between the CS and various arrhythmia substrates, elaborates on current indications for intra CS ablation and addresses efficacy and safety concerns associated with transcatheter ablation.

Cryoablation of substrates adjacent to the atrioventricular node: acute and long-term safety of 1303 ablation procedures

AIMS

Radiofrequency (RF) ablation is effective for ablation of atrial arrhythmias. However, RF ablation in the vicinity of the atrioventricular (AV) node is associated with a risk of inadvertent, irreversible high-grade AV block, depending on the type of substrate. Cryoablation is an alternative method. The objective was to investigate the acute and long-term risks of AV block during cryoablation.

METHODS AND RESULTS

We studied 1303 consecutive cryoablations of substrates in the vicinity of the AV node in 1201 patients (median age 51 years, range 6-89 years) on acute and long-term impairment to the AV nodal conduction system. The arrhythmias treated were AV nodal reentrant tachycardias (n=1116), paraseptal and superoparaseptal accessory pathways (n=100), and focal atrial tachycardias (n=87). In 158 (12%) procedures, cryomapping (38 cases) or cryoablation (120 cases) were stopped due to transient AV block (first-degree AV block 74 cases, second-degree AV block 67 cases, and third-degree AV block 17 cases) after which another site was tested. Transient AV block occurred within seconds of mapping up to 3 min of ablation. The incidence of AV block was similar for different substrates. In most cases, AV nodal conduction was restored within seconds but in two cases transient AV block lasted 21 and 45 min, respectively. There were no cases of acute permanent AV blocks. No late AV blocks occurred during follow-up (mean 24 months, range 6-96 months).

CONCLUSION

Cryoablation adjacent to the AV node carries a negligible risk of permanent AV block. Transient AV block during ablation is a benign finding.

Recognition and Prevention of Complications During Epicardial Ablation

Although the transthoracic epicardial mapping and ablation technique is a relatively safe procedure, complications can and do occur. The possible complications associated with this technique should be well understood before the procedure. If these complications are recognized early and managed appropriately, the outcome is usually excellent. This review describes the details of how to recognize, prevent, and manage the complications that occur during pericardial access, mapping and ablation, and post procedure.

New techniques of mapping and ablation for tachyarrhythmias in children

Advancement in mapping and ablation technologies in the past decade has made arrhythmia treatment in children safer and more effective. Electroanatomical mapping systems with features of nonfluoroscopic navigation, 3D-geometry construction and color-coded arrhythmia mapping have been extensively used to map and ablate tachycardias in children. In addition, a variety of cooled radiofrequency ablation systems have been used in selected patients to create larger and deeper lesions. Cryoenergy ablation, with its reversible nature of tissue injury during the cooling phase, is emerging as the energy of choice for ablating perinodal arrhythmias to minimize the risk of inadvertent conduction block. Other evolving ablation systems, including cryoballoon, high-intensity focused ultrasound balloon and a hybrid catheter capable of delivering both radiofrequency and cryoenergy, are also under investigation. Finally, a remote navigation system that minimizes radiation exposure and will enable physicians of all skill levels to reach difficult target sites in children is on the horizon.

Cryoablation of Accessory Pathways in the Coronary Sinus in Young Patients: A Multicenter Study from the Pediatric and Congenital Electrophysiology Society's Working Group on Cryoablation

INTRODUCTION

This is a multicenter retrospective study evaluating the immediate- and mid-term outcomes of cryoablation of accessory pathways in the coronary sinus in children or in patients with congenital heart disease.

METHODS AND RESULTS

Twenty-one patients (median age 13.0 years, range 2-40) from six institutions were included. The accessory pathways were concealed in 11 and manifest in 10. Of 12 patients who had coronary sinus angiography, two had large coronary sinus diverticula, one had a dilated coronary sinus due to a left superior vena cava to coronary sinus, and one had a "pouch" at the mouth of the coronary sinus. Six patients underwent ablation procedures with cryoablation alone, while in the remaining 15 patients, both cryoablation and radiofrequency ablation were utilized. The ablation procedure included left-sided endocardial mapping via a retrograde or transseptal approach in 13 (62%). Procedural success was achieved with cryoablation in the coronary sinus in 15/21 (71%). Four patients (19%) had successful radiofrequency ablation at the right or left posterior septum. Two patients (10%) had unsuccessful procedures. Of the 15 patients with initially successful cryoablation procedures, six (40%) had arrhythmia recurrences at a median of 17 days (range 1-120). Recurrences could not be explained by differences in patient or procedural variables.

CONCLUSION

Cryoablation in the coronary venous system in young patients is feasible but associated with a high arrhythmia recurrence rate. Cryoablation techniques and/or equipment need to be improved in order to safely create more permanent lesions in this arrhythmia substrate.

Radiofrequency catheter ablation within the coronary sinus eliminates a macro-reentrant atrial tachycardia: importance of mapping in the coronary sinus

We describe a patient who underwent radiofrequency (RF) catheter ablation of symptomatic atrial fibrillation. After left atrial (LA) catheter ablation and pulmonary vein isolation, a macro-reentrant atrial tachycardia (AT) with a critical isthmus at the mitral isthmus was induced by incremental atrial pacing from the coronary sinus. Extensive RF energy applications from endocardial sites using ablation catheters with 4 mm- and 8 mm- tips resulted in no discrete potentials being recorded from the endocardial sites of the isthmus, but the tachycardia could not be terminated. However, discrete potentials were recorded within the CS, and epicardial RF energy applications from the CS eliminated the tachycardia. Thus, mapping in the CS is useful for detecting residual conduction at epicardial sites along the mitral isthmus. RF catheter ablation within the CS should be considered when no distinct electrograms are recorded after extensive ablation from the endocardial sites and when distinct electrograms are recorded within the CS.

Impact of Catheter Ablation of the Coronary Sinus on Paroxysmal or Persistent Atrial Fibrillation

OBJECTIVES

This study evaluated the impact of catheter ablation of the coronary sinus (CS) region during paroxysmal and persistent atrial fibrillation (AF).

BACKGROUND

The CS musculature and connections have been implicated in the genesis of atrial arrhythmias.

METHODS

Forty-five patients undergoing catheter ablation of AF were studied. The CS was targeted if AF persisted after ablation of pulmonary veins and selected left atrial tissue. CS ablation was commenced endocardially by dragging along the inferior paramitral left atrium. Ablation was continued from within the vessel (epicardial) if CS electrograms had cycle lengths shorter than that of the left atrial appendage. RF energy was limited to 35 W endocardially and 25 W epicardially. The impact of ablation was evaluated on CS electrogram cycle length (CSCL) and activation sequence, atrial fibrillatory cycle length measured in the left atrial appendage (AFCL) and on perpetuation of AF.

RESULTS

Endocardial ablation significantly prolonged CSCL by 17 +/- 5 msec and organized the CS activation sequence (from 13% of patients before to 51% after ablation); subsequent epicardial ablation further increased local CSCL by 32 +/- 27 msec (P < 0.001). AFCL prolonged significantly both during endocardial and epicardial ablation (median: 152 to 167 msec P = 0.03) and was associated with AF termination in 16 (35%) patients (46% of paroxysmal and 30% of persistent AF). AFCL prolongation > or =5 msec and/or AF termination was associated with more rapid activity in the CS region originally: P < or = 0.04.

CONCLUSION

Catheter ablation targeting both the endocardial and epicardial aspects of the CS region significantly prolongs fibrillatory cycle length and terminates AF persisting after PV isolation in 35% of patients.

Epicardial catheter mapping and ablation of ventricular tachycardia

Percutaneous entry into the pericardial space allows epicardial catheter mapping and ablation in the electrophysiology laboratory, opening a perspective on cardiac electrophysiology that previously was limited largely to the operating room. Scar-related reentry after myocardial infarction usually involves the subendocardium but in some patients can only be ablated from the epicardium. Epicardial, scar-related reentry also is an important cause of ventricular tachycardia in nonischemic cardiomyopathies. Rare supraventricular tachycardias and idiopathic ventricular tachycardia that cannot be defined from the endocardium sometimes can be ablated from the epicardium. With appropriate precautions the procedural risks are low. Epicardial catheter techniques expand the options for investigating cardiac electrophysiology and treating arrhythmias in humans and may lead to insights into transmural properties influencing repolarization and the genesis of arrhythmias.

Cryoablation versus radiofrequency ablation for treatment of pediatric atrioventricular nodal reentrant tachycardia: Initial experience with 4-mm cryocatheter

BACKGROUND

Initial reports have shown cryoablation to be safe and efficacious for treatment of atrioventricular nodal reentrant tachycardia (AVNRT). No direct comparisons of cryoablation vs radiofrequency (RF) catheter ablation in pediatric patients have been made.

OBJECTIVES

The purpose of this study was to compare the outcomes of cryothermal vs RF catheter ablation for treatment of AVNRT in pediatric patients.

METHODS

We retrospectively reviewed consecutive ablation procedures for treatment of AVNRT at a single arrhythmia center. The RF group consisted of patients who underwent RF ablation from 2002 until cryothermy became available. The cryoablation group consisted of patients who underwent cryothermal ablation from 2004 to 2005. The groups were compared for procedural and electrophysiologic outcomes.

RESULTS

RF (n = 60, age 14 +/- 4 years) and cryoablation (n = 57, age 14 +/- 4 years) groups had similar demographic and baseline parameters. Procedural times were shorter in the RF group (RF ablation 112 +/- 31 minutes vs cryoablation 148 +/- 46 minutes, P < .001). Fluoroscopy times were comparable (RF ablation 21 +/- 15 minutes vs cryoablation 20 +/- 13 minutes, P = .77). In an intention-to-treat analysis, success of the procedure was 100% for RF ablation and 95% for cryoablation (P = .11). No permanent AV block occurred in either group. Recurrence rates were higher for the cryoablation group, but this did not reach statistical significance (RF ablation 2% vs cryoablation 8%, P = .19).

CONCLUSION

Cryoablation appears to be similar to RF for ablation of AVNRT with respect to short-term efficacy and safety of the procedure in a pediatric population. Recurrence rates are higher with cryoablation.

Anatomic Proximity of the Esophagus to the Coronary Sinus: Implication for Catheter Ablation Within the Coronary Sinus

INTRODUCTION

The anatomic proximity between the esophagus and the coronary sinus (CS) might render the esophagus vulnerable to thermal injury during ablation. Therefore, we investigated the anatomic relationship between the esophagus and the CS in patients with atrial fibrillation (AF).

METHODS AND RESULTS

Thirty patients (25 males, mean age = 54 +/- 11 years) with drug-refractory paroxysmal AF were included. Sixteen-slice multidetector computed tomography was performed to depict the course of the esophagus and relationship to the CS. The esophagus was in direct contact with the CS in 57% (17/30) of patients (group 1). The mean length of the contact was 6.1 +/- 3.4 mm. In the remaining 13 patients, the esophagus did not come in direct contact with the CS (group 2). The shortest distance between the esophagus and the CS was 4.0 +/- 2.6 mm. The CS diameter (9.4 +/- 1.8 vs 8.5 +/- 2.4 mm, P = 0.15), esophagus width (18.6 +/- 1.6 vs 18.6 +/- 1.7 mm, P = 0.87), anteroposterior diameter of the left atrium (35.9 +/- 3.8 vs 35.0 +/- 3.3 mm, P = 0.58), thickness of the anterior wall of the esophagus (2.9 +/- 0.6 vs 2.9 +/- 0.6 mm, P = 0.97), and shortest distance from the esophagus to the CS ostium (19.3 +/- 5.4 vs 25.0 +/- 6.2 mm, P = 0.02) and to the great cardiac vein (8.5 +/- 5.3 vs 12.1 +/- 6.9 mm, P = 0.10) were compared between the two groups.

CONCLUSIONS

In 57% of our patients, the esophagus was in direct contact with the CS, and a significantly shorter distance between the esophagus and the CS ostium was noted in these patients. It is important to prevent esophageal damage when applying energy within the CS.

Transvenous radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia and its pitfalls: A rationale for cryoablation?

Today, radiofrequency (RF) catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) is accompanied by a high success, a low recurrence, and a low complication rate. Despite the fact that over the years this technique has been refined, several shortcomings still remain. In this overview, the most important pitfalls in the treatment of AVNRT with RF energy are discussed. Cryotherapy has the ability to overcome some of them. Both ice mapping and cryo-adherence are important characteristics of this energy source to study prospective ablation sites before a definitive and irreversible lesion is created. Theoretically, this could lead to less applications with less tissue damage and abolish the risk for permanent conduction disturbances. The early experience with this technique will be described. Until now, it still has to be proven that in a large cohort of patients, cryotherapy is at least as effective, and safer than RF.

Isolation of Pulmonary Veins Using a Transvenous Curvilinear Cryoablation Catheter: Feasibility, Initial Experience, and Analysis of Recurrences

INTRODUCTION

Pulmonary vein isolation (PVI) using focal cryothermal catheters is safe and moderately effective, but associated with long procedure times. We hypothesized that a linear freezing segment could shorten fluoroscopic and procedure times. We report our initial experience with a novel circular cryothermal catheter.

METHODS AND RESULTS

Complete PV isolation (PVI) was achieved in 41 of 45 PVs by cryoablation (91%) in 18 patients who underwent Lasso-guided cryothermal using a novel 7 F circular catheter (2.5 +/- 0.7 veins per patient). A mean of 27.2 +/- 11 applications per patient (9.2 +/- 4.7 per vein) with a mean temperature -79.8 +/- 4 degrees C were delivered. Recorded temperatures did not predict complete or incomplete isolation. Focal cryothermal ablation using a 7 F 4-mm tip was required in the remainder for isolation. During 14.8 +/- 6.2 month follow-up, 4 (22%) had no recurrence of AF, and 7/18 (39%) had >90% reduction in symptoms without antiarrhythmic agents (AAA). Computed tomography scans at 3 months showed no stenosis (14.1 +/- 2.5 mm, 13.9 +/- 2.4 mm; P = 0.2). Eight patients underwent repeat ablation. Mapping demonstrated 13 of 14 (93%) previously isolated veins had recovery of over 64 +/- 24% of the ostium. All were successfully isolated with RF and 7 of 8 were arrhythmia free 6.0 +/- 2.9 months after ablation. Overall, 14 of 18 (78%) patients had their arrhythmia clinically controlled without drugs after one or two procedures.

CONCLUSIONS

Our initial experience demonstrates safety and feasibility of circular cryothermal ablation with less fluoroscopic and procedure times as compared to focal cryothermy. As with RF, complete and permanent isolation of the PVs is not easily achieved. Reducing heat load due to PV flow may improve results.

Catheter Ablation of Atypical Atrial Flutter and Atrial Tachycardia Within the Coronary Sinus After Left Atrial Ablation for Atrial Fibrillation

OBJECTIVES

The goal of this study was to describe the prevalence and ablation of coronary sinus (CS) arrhythmias after left atrial ablation for atrial fibrillation (AF).

BACKGROUND

The CS has been implicated in a variety of supraventricular arrhythmias.

METHODS

Thirty-eight patients underwent mapping and ablation of atypical flutter that developed during (n = 5) or after (n = 33) ablation for AF. Also included were two patients with focal CS arrhythmias that occurred during an AF ablation procedure. A tachycardia was considered to be originating from the CS if the post-pacing interval in the CS matched the tachycardia cycle length and/or if it terminated during ablation in the CS.

RESULTS

Among the 33 patients who developed atypical flutter late after AF ablation, 9 (27%) were found to have a CS origin. Overall, 16 of the 40 patients in this study had a CS arrhythmia. The tachycardia was macro-re-entrant in 14 patients (88%) and focal in two patients. Radiofrequency ablation with an 8-mm-tip catheter was successful in 15 patients (94%) without complication. In eight patients (50%), > or = 45 W was required for successful ablation. Thirteen of the 15 patients (87%) with a successful ablation acutely remained arrhythmia-free during 5 +/- 5 months of follow-up.

CONCLUSIONS

The musculature of the CS serves as a critical component of the re-entry circuit in approximately 25% of patients with atypical flutter after ablation for AF. The CS may also generate focal atrial arrhythmias that may play a role in triggering and/or maintaining AF. Catheter ablation of these arrhythmias in the CS can be performed safely.