Abstract
Background
Recent studies have confirmed the feasibility and safety of cavotricuspid isthmus (CTI) ablation using either a pentaspline or a focal monopolar pulsed-field ablation catheter. However, no documented cases have reported irreversible heart block as a potential complication.
Case Summary
A 62-year-old woman with persistent atrial fibrillation underwent CTI ablation using a pentaspline pulsed-field catheter after pulmonary vein isolation. Immediately postablation, third-degree atrioventricular block occurred, transiently recovering to 2:1 block before reverting to complete heart block. A permanent pacemaker was subsequently implanted given irreversible conduction impairment.
Discussion
We report to our knowledge the first case of irreversible heart block after CTI ablation using a pentaspline pulsed-field ablation catheter, necessitating permanent pacemaker implantation after 13 hours of observation. This case underscores the need for caution when employing this technology for CTI ablation.
Take-Home Message
Irreversible heart block is a novel, albeit rare, complication of CTI ablation with a pentaspline pulsed-field catheter.
Key words: cavotricuspid isthmus ablation, irreversible heart block, pentaspline catheter, pulsed-field ablation
Graphical Abstract
Recent studies have established the feasibility and safety profile of pulsed-field ablation for the cavotricuspid isthmus (CTI), identifying coronary artery spasm and transient atrioventricular conduction disturbances as rare yet clinically significant complications.1,2 In the present case, however, an irreversible complete heart block occurred acutely after a single CTI ablation procedure using a pentaspline pulsed-field ablation catheter.
Case Presentation
A 62-year-old woman diagnosed with persistent atrial fibrillation was admitted to our institution. Her medical history was notable for hypertension, type 2 diabetes mellitus, and lacunar infarction. Electrocardiogram confirmed atrial fibrillation with a right bundle branch block morphology and a ventricular rate ranging between 60 and 200 beats/min (Figure 1A). Physical examination was unremarkable. Medication on admission included rivaroxaban, metoprolol, telmisartan, gliclazide, and metformin.
Figure 1.
Cavotricuspid Isthmus Ablation and Onset of Atrioventricular Block
(A) Admission ECG demonstrating atrial fibrillation with rapid ventricular rate. (B) Cavotricuspid isthmus ablation performed with a pentaspline pulsed-field ablation catheter (LAO 45° view). (C) Right atrial origin of atrial flutter. (D) Third-degree atrioventricular block after a single pulsed-field application. ECG = electrocardiogram; LAO = left anterior oblique; MV = mitral valve; TV = tricuspid valve.
Transthoracic echocardiography demonstrated moderate to severe mitral regurgitation and moderate tricuspid regurgitation, accompanied by biatrial enlargement. Left atrial dimensions measured 53 × 66 × 54 mm (anteroposterior × craniocaudal × transverse), and right atrial enlargement was indicated by a craniocaudal diameter of 55 mm.
The patient subsequently underwent ablation using the Farapulse PFA system (Boston Scientific) with a 35-mm pentaspline pulsed-field ablation catheter (Farawave; Boston Scientific). At the end of the uneventful pulmonary vein isolation, an atrial flutter occurred that originated from the right atrium (Figure 1C). After administration of 0.3 mg of intravenous nitroglycerin, a single application (peak voltage: 2.0 kV) in basket configuration was delivered at the lateral annular portion of the CTI (Figure 1B).
The patient presented acutely with third-degree atrioventricular block (AVB), accompanied by a junctional escape rhythm at a rate of 26 beats/min (Figure 1D). A decapolar catheter was subsequently positioned within the right ventricle, and intermittent pacing was delivered via the distal electrode to assess the recovery of atrioventricular conduction (Figure 2A). Dexamethasone and isoproterenol were administrated intravenously. Over the ensuing 1-hour observation period, the third-degree AVB evolved into second-degree AVB with 2:1 conduction, accompanied by a shortening of the PR interval from 329 to 202 ms (Figures 2B to 2D). A temporary transvenous pacing lead was thereafter placed for hemodynamic support and rhythm management. After a 12-hour observation period, the patient's rhythm reverted to third-degree AVB. Consequently, a permanent dual-chamber pacemaker was implanted and programmed in DDD mode with search AV algorithm enabled. Device interrogation performed 1 month after discharge revealed 100% ventricular pacing.
Figure 2.
Evolution of Atrioventricular Conduction Disturbances
(A) Intermittent pacing from the right ventricular outflow tract. (B to D) Second-degree atrioventricular block with 2:1 conduction, demonstrating PR interval shortening from 329 to 202 ms.
Discussion
CTI ablation is routinely recommended during atrial fibrillation ablation procedures if CTI-dependent atrial flutter has been documented historically or is induced intraprocedurally.3,4 Although radiofrequency ablation remains the standard safe and effective energy source for CTI ablation, emerging evidence on the tissue selectivity of pulsed-field ablation suggests that this nonthermal technology may represent a promising alternative to thermal ablation modalities.5
Multiple studies have demonstrated the safety and feasibility of CTI ablation using either pentaspline or monopolar focal pulsed-field ablation catheters. Conduction disturbance has been reported as an uncommon but reversible complication. In a cohort study by Farnir et al,1 2 patients (2%) exhibited transient complete AVB during the procedure, with recovery postoperatively; 5 patients (5%) showed PR-interval prolongation that persisted for up to 3 months. Similarly, Andrikopoulos et al6 described a case of transient conduction disturbances—including PR prolongation, new-onset right bundle branch block, and left posterior fascicular block—occurring acutely after pulsed-field CTI ablation using a 31-mm pentaspline Farawave catheter, which resolved spontaneously within 12 hours.
Potential mechanisms of atrioventricular disturbance during CTI ablation include acute right coronary artery (RCA) spasm,7,8 vagally mediated conduction delay,9 or direct injury to the atrioventricular node.10 Malyshev et al11 reported that during focal pulsed-field CTI ablation, RCA vasospasm occurred in 80% (4/5) of patients without nitroglycerin. Administration of repetitive nitroglycerin boluses (2-3 mg every 2 minutes) reduced the incidence to 20% (2/10), whereas a single bolus (3 mg) followed by continuous infusion (1 mg/min) resulted in severe or mild-moderate spasm in 40% (4/10), as assessed by fractional flow reserve. In the Farnir et al1 study, prophylactic nitroglycerin (0.15-0.4 mg) followed by additional boluses (0.2-1.0 mg) led to transient ST-segment elevation (lasting 2-15 minutes) in 5% (4/82) of patients. In the present case, a single intravenous nitroglycerin bolus (0.3 mg) was administered, and no ST-T segment changes were observed, making RCA spasm unlikely. Epicardial vagal fibers and ganglia are also densely distributed within the CTI region. Pulsed-field application near cardiac ganglionated plexi frequently induces a vagal response during pulmonary vein isolation, which is typically transient. In the present case, normal atrioventricular conduction was not restored after 48 hours of observation, making injury to ganglionated plexi an unlikely mechanism. Unlike radiofrequency ablation, pulsed-field ablation generates broader tissue lesions within the electric field and is less dependent on catheter contact force.12 Consequently, the patient likely sustained direct injury to the atrioventricular node despite CTI-targeted ablation. Preprocedural echocardiography showed biatrial enlargement, and electroanatomic mapping identified a large left atrial low-voltage area, both of which may heighten susceptibility to injury at the atrioventricular junction. Therefore, achieving stable catheter position at the medial CTI using multiplanar fluoroscopy (eg, left anterior oblique 45°, right anterior oblique 30°views) and performing detailed anatomical mapping prior to ablation are critical for safety.
Conclusions
This case represents to our knowledge the first documented instance of irreversible heart block as a potential, albeit rare, complication of cavotricuspid isthmus ablation performed with a pentaspline pulsed-field ablation catheter.
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Take-Home Message
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•
This case reports irreversible heart block as a novel, albeit rare, complication of cavotricuspid isthmus ablation with a pentaspline pulsed-field catheter.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
Contributor Information
Shimo Dai, Email: dai.shimo@zs-hospital.sh.cn.
Junbo Ge, Email: ge.junbo@zs-hospital.sh.cn.
References
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