Mechanisms by which adenosine restores conduction in dormant canine pulmonary veins

Upregulation of adenosine A1 receptors facilitates sinoatrial node dysfunction in chronic canine heart failure by exacerbating nodal conduction abnormalities revealed by novel dual-sided intramural optical mapping

BACKGROUND

Although sinoatrial node (SAN) dysfunction is a hallmark of human heart failure (HF), the underlying mechanisms remain poorly understood. We aimed to examine the role of adenosine in SAN dysfunction and tachy-brady arrhythmias in chronic HF.

METHODS AND RESULTS

We applied multiple approaches to characterize SAN structure, SAN function, and adenosine A1 receptor expression in control (n=17) and 4-month tachypacing-induced chronic HF (n=18) dogs. Novel intramural optical mapping of coronary-perfused right atrial preparations revealed that adenosine (10 μmol/L) markedly prolonged postpacing SAN conduction time in HF by 206 ± 99 milliseconds (versus 66 ± 21 milliseconds in controls; P=0.02). Adenosine induced SAN intranodal conduction block or microreentry in 6 of 8 dogs with HF versus 0 of 7 controls (P=0.007). Adenosine-induced SAN conduction abnormalities and automaticity depression caused postpacing atrial pauses in HF versus control dogs (17.1 ± 28.9 versus 1.5 ± 1.3 seconds; P<0.001). Furthermore, 10 μmol/L adenosine shortened atrial repolarization and led to pacing-induced atrial fibrillation in 6 of 7 HF versus 0 of 7 control dogs (P=0.002). Adenosine-induced SAN dysfunction and atrial fibrillation were abolished or prevented by adenosine A1 receptor antagonists (50 μmol/L theophylline/1 μmol/L 8-cyclopentyl-1,3-dipropylxanthine). Adenosine A1 receptor protein expression was significantly upregulated during HF in the SAN (by 47 ± 19%) and surrounding atrial myocardium (by 90 ± 40%). Interstitial fibrosis was significantly increased within the SAN in HF versus control dogs (38 ± 4% versus 23 ± 4%; P<0.001).

CONCLUSIONS

In chronic HF, adenosine A1 receptor upregulation in SAN pacemaker and atrial cardiomyocytes may increase cardiac sensitivity to adenosine. This effect may exacerbate conduction abnormalities in the structurally impaired SAN, leading to SAN dysfunction, and potentiate atrial repolarization shortening, thereby facilitating atrial fibrillation. Atrial fibrillation may further depress SAN function and lead to tachy-brady arrhythmias in HF.

How To Achieve Durable Pulmonary Vein Antral Isolation?

The inability to achieve durable pulmonary vein isolation(PVI) remains a major limitation to a catheter ablation for thew treatment of atrial fibrillation(AF), potentially resulting in AF recurrence.In this review,we discuss the research performed investigating methods to improve lesion permanence for the goal of durable PVI.Investigations evaluted procedural techniques,various catheres utilized, adjunctive pharamacologic therapy and novel energy sources designed to improve ablation lesion permanence are discussed.

Radiofrequency ablation annotation algorithm reduces the incidence of linear gaps and reconnection after pulmonary vein isolation

BACKGROUND

A common mechanism of atrial fibrillation recurrence after catheter ablation is resumption of pulmonary vein (PV) conduction due to gaps in the ablation line. These gaps may go unrecognized owing to inadequate ablation lesion annotation.

OBJECTIVE

To examine the utility of an automated radiofrequency (RF) ablation annotation algorithm for the detection and treatment of ablation gaps during pulmonary vein isolation (PVI).

METHODS

Eighty-four patients with paroxysmal atrial fibrillation underwent PVI. In 42 patients (group A), RF ablation was guided by an automated algorithm with predefined criteria of catheter stability range of motion ≤2 mm and impedance decrease ≥5% for individual ablation applications. In 42 control patients (group B), ablation was guided by the operator. Successful PVI, conduction recovery, and dormant conduction with adenosine were compared between the groups.

RESULTS

Ipsilateral PVI at the completion of the initial anatomical line was obtained in 90.5% of group A patients (76 of 84 ipsilateral pairs of PVs) but only in 66.7% of group B patients (56 of 84 ipsilateral pairs of PVs) (P = .0001). Ineffective energy delivery was detected in 23% (1005 of 4362) of group A applications but only in 9% (368 of 4071) of group B applications (P = .0001). The frequency of conduction recovery was lower in group A than in group B (5.9% vs 25%; P = .001). Arrhythmia-free survival at 6 months trended higher in group A (38 of 42 [90%]) than in group B (32 of 42 [76%]; P = .07).

CONCLUSION

Automated ablation lesion annotation provides real-time feedback of RF ablation that may improve effective energy delivery.

High-volume lesions using a new second-generation open irrigation radiofrequency catheter are associated with the development of inhomogeneous lesions

BACKGROUND

After catheter ablation there is often a discrepancy between acute and chronic success rates. We aimed to evaluate major determinants for lesion quality and understand different manifestations of lesion structures.

METHODS

In a canine thigh muscle model radiofrequency (RF) current was delivered for 60 seconds at 30 W (n = 39) or 50 W (n = 18) with 15-g contact force. A second-generation 12-hole gold open irrigation catheter (SGIT) and a first-generation six-hole platinum-iridium catheter (FGIT; Biotronik, Berlin, Germany) were used. Electrode and tissue temperatures (at the surface and 3.5-mm and 7-mm depth) were recorded and lesion dimensions were measured. Lesions with steam pops were excluded. Histological examination was performed to evaluate homogeneity of the lesions. Inhomogeneity was defined as a visual multiband lesion pattern indicating different histological characteristics.

RESULTS

In total 57 lesions were created. Seventeen lesions were excluded (steam pops) and 40 lesions were analyzed. A total number of 11 homogeneous and 29 inhomogeneous lesions were identified. Using the SGIT catheter 16.7% of the lesions was homogeneous and 83.3% inhomogeneous; for FGIT it was 43.8% and 56.2% (P = 0.065), respectively. Homogeneous lesions had lower volumes as compared to inhomogeneous lesions (514.0 ± 198.8 vs 914.8 ± 399.1 mm, P = 0.003). Multiple logistic regression analysis indicated that the SGIT catheter is a significant predictor for inhomogeneous lesions (odds ratio 6.5, 95% confidence interval 1.1-38.8; P = 0.040) independent from power setting and flow rate.

CONCLUSIONS

The development of inhomogeneous lesions after acute RF ablation is associated with higher lesion volumes and the use of the second-generation irrigation gold-tip catheter.

The effects of standard electrical PV isolation vs. "pace and ablate" on ATP-provoked PV reconnections

BACKGROUND

Catheter ablation procedures for atrial fibrillation (AF) often involve circumferential pulmonary vein isolation (PVI). Lack of reliable identification of conduction gaps along the ablation line necessitates additional ablation within previous lesion sets. We conducted a retrospective comparative study to determine the best PVI strategy for prevention of PV reconnections.

METHODS AND RESULTS

We compared the outcomes of PVI performed in two groups of patients with AF: those in whom a three-dimensional mapping system and irrigated tip radiofrequency catheter were used to electrically isolate the ipsilateral PVs (31 patients, electrical isolation group) and those in whom "pace and ablate" was performed in the PV antra until pacing at 10 mA and 2 ms no longer captured the atrial myocardium along the ablation line (31 patients, pace and ablate group). A bolus administration of 30 mg of adenosine triphosphate (ATP) revealed dormant PV reconnections more frequently in the electrical isolation group than in the pace and ablate group (28 [90%] of 31 patients vs. 16 [52%] of 31 patients, p = 0.0005). After re-isolation of the sites of dormant PV conduction, the post-ablation recurrence rates at 1 year were similar (26 vs. 26%, p = 1.000).

CONCLUSION

Electrical PVI can usually be achieved without complete circumferential ablation. However, the isolated PVs often show dormant conduction. These findings support the hypothesis that reversible tissue injury contributes to PVI that may be acute but not necessarily durable. Similar outcomes between the two ablation strategies suggest that ATP provocation tests remain necessary to unmask dormant PV conduction.

Atrial fibrillation

Atrial fibrillation is the most common arrhythmia affecting patients today. Disease prevalence is increasing at an alarming rate worldwide, and is associated with often catastrophic and costly consequences, including heart failure, syncope, dementia, and stroke. Therapies including anticoagulants, anti-arrhythmic medications, devices, and non-pharmacologic procedures in the last 30 years have improved patients' functionality with the disease. Nonetheless, it remains imperative that further research into AF epidemiology, genetics, detection, and treatments continues to push forward rapidly as the worldwide population ages dramatically over the next 20 years.

Adenosine triphosphate-induced atrial fibrillation: the clinical significance and relevance to spontaneous atrial fibrillation

PURPOSE

Adenosine triphosphate (ATP) frequently triggers atrial fibrillation (AF), but the clinical significance of this phenomenon is unknown. The purpose of this study was to reveal the relevance between spontaneous AF and ATP-induced AF.

METHODS

In 81 AF patients undergoing pulmonary vein isolation (PVI), we injected 20 mg of ATP before PVI, and recorded triggering sites of the AF induced. We also injected 20 mg of ATP in 44 patients receiving ablation for atrioventricular reciprocating tachycardia (AVRT).

RESULTS

ATP provoked AF in 24 (29.6 %) of the 81 PVI patients and atrial ectopic beats in a further 48 (59.3 %). The trigger site of the AF was in the PV and the right atrium in 22 (91.7 %) and 2 patients, respectively. In 14 of those 24 patients, spontaneous AF arose from the same triggering site as the ATP-induced AF. In the 48 patients with ATP-provoked ectopic beats, spontaneous AF arose from the same site in 13. Conversely, among the 34 patients demonstrating spontaneous AF initiation, AF or ectopic beats were provoked by ATP from the same site in 14 (41.2 %) and 13 patients (38.2 %), respectively. ATP provoked AF in only 2 (4.5 %) of the AVRT patients. In summary, ATP provoked AF or atrial ectopic beats in 88.9 % of PVI patients, 36.1 % of whose triggering sites matched that of the spontaneous AF, while 79.4 % of spontaneous AF trigger sites matched ATP-provoked AF or ectopic beat sites.

CONCLUSIONS

ATP-induced AF was strongly associated with clinical AF, and ATP is useful for identifying arrhythmogenic sites.

Electrophysiological Evaluation of Thoracoscopic Pulmonary Vein Isolation

Although the majority of patients with atrial fibrillation and an indication for non-pharmacological therapy is treated with catheter ablation, thoracoscopic surgery is an emerging technique that aims at combining the results of the classic Cox Maze operation with a less invasive approach. Recurrences after thoracoscopic surgery have been mainly ascribed to incomplete ablation lines, but literature on electrophysiological confirmation of thoracoscopic pulmonary vein isolation is limited. Currently, surgical confirmation of uni- or bidirectional conduction block may be hampered by insufficient resolution of the mapping material available. Additionally uncertainty remains on the precise lesions sets required, and how to tailor them to individual patients. In hybrid procedures, electrophysiologists and surgeons join forces to combine their expertise and skills which may lead to increased procedural success rates by minimizing the chance of incomplete PV isolation or absence of conduction block across an alternative ablation line. Here we describe techniques for thoracoscopic mapping and present a literature review.

Pulmonary vein isolation using a pace-capture-guided versus an adenosine-guided approach: effect on dormant conduction and long-term freedom from recurrent atrial fibrillation--a prospective study

BACKGROUND

Atrial fibrillation recurrence after pulmonary vein (PV) isolation is associated with PV to left atrium reconduction. We prospectively studied the use of 2 procedural techniques designed to facilitate identification of residual gaps within the index ablation line.

METHODS AND RESULTS

After wide circumferential PV isolation, 40 patients received additional ablation targeted at locations of left atrial capture during high-output pacing (pace-capture group), while 40 patients underwent adenosine testing with targeted ablation at sites of dormant conduction (adenosine group). Patients were followed up at 3, 6, and 12 months. After PV isolation, high-output pace-capture was documented in 39 PVs (25%; 50% of patients) in the pace-capture group. Dormant conduction was unmasked in 34 PVs (22%; 53% of patients) in the adenosine group. A subset of 25 patients in the pace-capture group underwent adenosine testing without targeted ablation of dormant conduction. In these patients, only 10 out of 86 PVs (11.6%; 24% of patients) demonstrated dormant conduction after the elimination of local pace-capture. At a follow-up of 329±124 days, the single procedure off antiarrhythmic drug freedom from recurrent atrial fibrillation was 67.5% in the adenosine group and 65.0% in the pace-capture group (P=0.814). Procedure duration and fluoroscopy time were significantly longer in the pace-capture group (P=0.002 and P<0.001), whereas radiofrequency ablation time was comparable (P=0.192).

CONCLUSIONS

The use of high-output pacing post-PV isolation results in a significant reduction in the incidence of dormant conduction with a comparable long-term freedom from recurrent atrial fibrillation (versus adenosine-guided ablation). The use of these approaches requires evaluation in a long-term prospective randomized study. [corrected].

Long-term results of pulmonary vein antrum isolation in patients with atrial fibrillation: an analysis in regards to substrates and pulmonary vein reconnections

AIMS

To examine the impact of left atrial (LA) low-voltage zones (LVZs) on atrial fibrillation (AF) recurrence after pulmonary vein antrum isolation (PVAI) without LA substrate modification.

METHODS AND RESULTS

Seventy-six patients with AF (paroxysmal/persistent 65/11) were prospectively enroled. Left atrial voltage maps were constructed during sinus rhythm using NavX to identify LVZs (<0.5 mV), and PVAI without any LA substrate modification was performed using an open-irrigation catheter. After PVAI, 20 mg of adenosine triphosphate (ATP) was injected. Adenosine triphosphate-induced PV reconnections were eliminated by touch-up ablation when unmasked. Voltage maps revealed LVZs in 24 patients (32%) and no LVZs in 52 (68%). During 24 ± 7 months of follow-up, 15 patients (63%) with LVZs and 10 (19%) without had AF recurrences off antiarrhythmic drugs (log-rank P < 0.001). A multivariate logistic regression analysis revealed that LVZ areas [odds ratio (OR): 1.12 per 1 cm(2), 95% confidence interval (CI): 1.04-1.23, P = 0.001] and ATP-induced reconnection (OR: 2.08, 95% CI: 1.01-4.91, P = 0.046) were significant predictors of recurrence. In those with LVZs, the LVZ area was strongly correlated with the LA body volume (r = 0.81, P < 0.001) and a unique predictor of recurrence (OR: 1.17 per 1 cm(2), 95% CI: 1.01-1.55, P = 0.031), while in those without an LVZ, ATP-induced PV reconnection was a unique predictor (OR: 3.24, 95% CI: 1.15-15.39, P = 0.025).

CONCLUSION

The LVZ area was an independent predictor of recurrence after PVAI without any LA substrate modification. Adenosine triphosphate-induced PV reconnection was also an independent predictor, especially in those without LVZs.

Development of biophysically detailed electrophysiological models for pacemaking and non-pacemaking human pulmonary vein cardiomyocytes

Ectopic foci originating from the pulmonary veins (PVs) have been suggested as the underlying cause for generating atrial arrhythmias that include atrial fibrillation (AF). Recent experimental findings indicate two types of PV cells: pacemaking and non-pacemaking. In this study, we have developed two mathematical models for human PV cardiomyocytes with and without pacemaking activities. The models were reconstructed by modifying an existing model of the human right atrium to incorporate extant experimental data on the electrical differences between the two cell types. Differences in their action potential (AP) profiles and automaticity were reproduced by the models, which can be attributed to the observed differences in the current densities of I(NCX), I(to), I(Na) and I(Ca-L), as well as the difference in the channel kinetics of I(Ca-L) and inclusion of the I(f) and I(Ca-T) currents in the pacemaking cells. The developed models provide a useful tool suitable for studying the substrates for generating AF.

Corticosteroid use during pulmonary vein isolation is associated with a higher prevalence of dormant pulmonary vein conduction

BACKGROUND

Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is associated with PV to left atrium reconduction.

OBJECTIVE

The purpose of this study was to prospectively determine if the use of intraprocedural corticosteroids to limit the extent of tissue edema and/or inflammation alters the prevalence of spontaneous and adenosine-induced acute PV reconnection after PVI.

METHODS

Prior to wide circumferential PVI, 45 patients received a single intravenous (IV) bolus of hydrocortisone 250 mg immediately after transseptal access (steroid group). Another 45 consecutive patients underwent standard PVI without IV hydrocortisone (nonsteroid group). After PVI, all patients underwent adenosine testing to unmask dormant conduction. Patients were followed at 3, 6, and 12 months.

RESULTS

Dormant conduction was unmasked in a significantly higher proportion of PVs in the steroid group compared with the nonsteroid group (32.8% of PVs [60/183] vs 21.1% of PVs [37/175], P = .03). On multivariate generalized estimating equation analysis, steroid use remained independently associated with dormant PV conduction (P = .03). There was no difference in the segmental distribution of reconnection between the 2 groups. The 1-year freedom from recurrent AF did not differ between groups (P = .37). Radiofrequency time was significantly longer in the steroid group (58 ± 21 minutes vs 48 ± 18 minutes, P <.01), whereas procedure duration and fluoroscopy time were comparable (P = .55 and P = .44, respectively).

CONCLUSION

A single bolus of hydrocortisone 250 mg IV prior to PVI results in greater radiofrequency requirements for PVI and a higher prevalence of dormant PV conduction unmasked by adenosine. The utility of these approaches requires evaluation in a long-term prospective randomized study.

Current hot potatoes in atrial fibrillation ablation

Atrial fibrillation (AF) ablation has evolved to the treatment of choice for patients with drug-resistant and symptomatic AF. Pulmonary vein isolation at the ostial or antral level usually is sufficient for treatment of true paroxysmal AF. For persistent AF ablation, drivers and perpetuators outside of the pulmonary veins are responsible for AF maintenance and have to be targeted to achieve satisfying arrhythmia-free success rate. Both complex fractionated atrial electrogram (CFAE) ablation and linear ablation are added to pulmonary vein isolation for persistent AF ablation. Nevertheless, ablation failure and necessity of repeat ablations are still frequent, especially after persistent AF ablation. Pulmonary vein reconduction is the main reason for arrhythmia recurrence after paroxysmal and to a lesser extent after persistent AF ablation. Failure of persistent AF ablation mostly is a consequence of inadequate trigger ablation, substrate modification or incompletely ablated or reconducting linear lesions. In this review we will discuss these points responsible for AF recurrence after ablation and review current possibilities on how to overcome these limitations.

Adenosine testing in atrial flutter ablation: unmasking of dormant conduction across the cavotricuspid isthmus and risk of recurrence

BACKGROUND

Adenosine-induced hyperpolarization may identify pulmonary veins at risk of reconnection following electrical isolation for atrial fibrillation. The potential role of adenosine testing in other arrhythmic substrates, such as cavotricuspid isthmus (CTI)-dependent atrial flutter, remains unclear. We assessed whether dormant conduction across the CTI may be revealed by adenosine after ablation-induced bidirectional block, and its association with recurrent flutter.

METHODS AND RESULTS

Patients undergoing catheter ablation for CTI-dependent flutter were prospectively studied. After confirming bidirectional block across the CTI by standard pacing maneuvers, adenosine (≥ 12 mg IV) was administered to assess resumption of conduction, followed by isoproterenol (ISP) bolus. Further CTI ablation was performed for persistent (but not transient) resumption of conduction. Bidirectional block across the CTI was achieved in all 81 patients (63 males), age 61.2 ± 11.0 years. The trans-CTI time increased from 71.9 ± 18.1 milliseconds preablation to 166.2 ± 26.4 milliseconds postablation. Adenosine elicited resumption of conduction across the CTI in 7 patients (8.6%), 2 of whom had transient recovery. No additional patient with dormant conduction was identified by ISP. Over a follow-up of 11.8 ± 8.0 months, atrial flutter recurred in 4 (4.9%) patients, 3/7(42.9%) with a positive adenosine challenge versus 1/74 (1.3%) with a negative response, P = 0.0016 (relative risk 31.7).

CONCLUSION

Adenosine challenge following atrial flutter ablation provoked transient or persistent resumption of conduction across the CTI in almost 9% of patients and identified a subgroup at higher risk of flutter recurrence. It remains to be determined whether additional ablation guided by adenosine testing during the index procedure may further improve procedural outcomes.

Clinical impact of adenosine triphosphate injection on arrhythmogenic superior vena cava in the context of atrial fibrillation ablation

BACKGROUND

Superior vena cava (SVC) is an infrequent yet an important source of atrial fibrillation. The clinical impact of ATP injection on arrhythmogenic SVC has not been evaluated.

METHODS AND RESULTS

A total of 43 patients (59±11 years; men, 32) who underwent ATP test for arrhythmogenic SVC after the electric isolation at either initial procedure or repeat procedure were included. Pulmonary vein antrum isolation was performed at index procedure in all patients. SVC was isolated after identifying the arrhythmogenicity at index and repeat atrial fibrillation ablation procedure in 34 (79.1%) and 9 (20.9%) patients, respectively. Atrial fibrillation originated from the SVC spontaneously and under isoproterenol infusion in 30 (75.0%) patients, and immediately after ATP injection in 10 (25.0%) patients. Tachycardia persistently confined to SVC was recorded after electric isolation in 13 (30.2%) patients. SVC reconnection was provoked by ATP test in 7 of 36 (19.4%) patients at acute phase. At median 4.0 (2.25-7.5) months after SVC isolation, reconnection was observed in 12 of 15 (80.0%) patients at repeat procedure. Among 12 patients with reconnection at baseline, SVC reconnection was provoked by ATP test after reisolation in 1 (8.3%) patient. Among 3 patients without SVC reconnection at baseline, reconnection was provoked by ATP test at chronic phase in 1 patient.

CONCLUSIONS

Dormant conduction between an arrhythmogenic SVC and the right atrium can be exposed by ATP administration both immediately and late after isolation, potentially facilitating detection and ablation for isolation.

Clinical utility of adenosine-infusion test at a repeat atrial fibrillation ablation procedure

BACKGROUND

The majority of patients with recurrence of arrhythmia after the initial atrial fibrillation (AF) ablation procedure have resumption of pulmonary vein (PV) conduction. Adenosine-infusion test after PV isolation identifies acute dormant PV conduction during the index procedure.

OBJECTIVE

To evaluate the utility of adenosine-infusion test at a repeat AF ablation procedure.

METHODS

This study included 50 consecutive patients (38 men; mean age 65 ± 9 years) who underwent second ablation procedure for recurrent atrial tachyarrhythmia(s). At the index procedure, which was undertaken for paroxysmal AF, all patients underwent PV isolation and 48 of 50 (96%) underwent superior vena cava (SVC) isolation followed by adenosine infusion. PV and SVC were reisolated-if found reconnected-at the start of the second procedure. Thereafter, adenosine-infusion test was undertaken for all PVs in all patients.

RESULTS

At the index procedure, adenosine infusion revealed dormant PV conduction in 15 of 50 (30%) patients. At the second procedure, after 10 ± 10 months, PV and SVC reconnections were observed in 46 of 50 (92%) and 33 of 48 (68.8%) patients and they were reisolated. Subsequently, adenosine-infusion test revealed dormant PV conduction in 9 of 50 (18%) patients, including 3 of 50 (6%) who had no PV reconnection at the start of the procedure. In these 3 patients, transient AF resulted after adenosine infusion, and at mean 8.0 ± 3.4 months, they were free from any atrial arrhythmia after the elimination of dormant PV conduction alone.

CONCLUSIONS

Adenosine-infusion test reveals dormant thoracic vein conduction associated with arrhythmia recurrence in the chronic phase after the initial PV isolation.

Drug-induced atrial fibrillation

INTRODUCTION

Atrial fibrillation (AF) is the most common arrhythmia and an important cause of hospitalization, morbidity, and mortality. A myriad of drugs can induce AF. However, drug-induced AF (DIAF) receives little attention. Thus, this review is an attempt to attract the attention on this adverse effect.

AREAS COVERED

Published reports of drug-induced AF (DIAF) are reviewed in this paper, from January 1974 to December 2011, using the PubMed/Medline database and lateral references.

EXPERT OPINION

In most cases, DIAF is paroxysmal and terminates spontaneously, but sometimes AF persists and it is necessary to perform a cardioversion to restore sinus rhythm and avoid progression to persistent AF. Because of the short duration of DIAF, in addition to physicians/patients not being knowledgeable about this side effect, the real incidence and clinical consequences of DIAF are presently unknown. DIAF is an increasing problem, as some widely prescribed drugs can present this adverse effect. The risk is expected to increase in the elderly and in patients with comorbidities. It is important that physicians understand the significance of DIAF, to increase the collaboration between cardiac and non-cardiac professionals, and to educate patients to make them aware of this adverse side effect.

Clinical implication of adenosine test at repeat atrial fibrillation ablation procedure: the importance of detecting dormant thoracic vein conduction

BACKGROUND

Pulmonary vein reconnection after electrical isolation is commonly observed in the context of atrial fibrillation ablation and is associated with recurrent atrial tachyarrhythmias. Adenosine test was been performed to identify acute dormant conduction immediately after pulmonary vein isolation at index procedure. However, the utility of adenosine test at repeat procedure has not been reported.

METHODS AND RESULTS

We report 5 paroxysmal atrial fibrillation cases without any structural heart disease in which dormant thoracic vein conduction was associated with recurrent atrial tachyarrhythmias. All patients had undergone circumferential ipsilateral pulmonary vein isolation at the index procedure. Superior vena cava isolation was performed if superior vena cava-triggered atrial fibrillation was identified. At the index procedure, adenosine test did not provoke venous reconduction. At the repeat procedure, adenosine provoked clinical arrhythmia in 4 out of 5 cases after transient reconnection between culprit thoracic vein and atrium despite absence of reconnection at the start of the procedure. After the elimination of the dormant conduction gaps, all patients were free from recurrent arrhythmia.

CONCLUSIONS

Adenosine provokes dormant thoracic vein conduction associated with the late recurrence of atrial tachyarrhythmias after previous thoracic vein isolation. Thus, adenosine provocation test can specifically help identify and target the cause of recurrent atrial arrhythmia.

2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design

This is a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation, developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology and the European Cardiac Arrhythmia Society (ECAS), and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). This is endorsed by the governing bodies of the ACC Foundation, the AHA, the ECAS, the EHRA, the STS, the APHRS, and the HRS.

Adenosine plus dipyridamole: a novel strategy to enhance adenosine-induced conduction recovery after pulmonary vein isolation

AIMS

Intravenous administration of adenosine after a pulmonary vein (PV) isolation procedure can unmask residual, so-called 'dormant', conduction that would otherwise remain unnoticed. Elimination of these dormant potentials is challenging because of the transient effect of adenosine, often requiring repeated injections. We tested the hypothesis that dipyridamole, a drug which inhibits adenosine deamination, can provoke longer-lasting unmasking of dormant conduction.

METHODS AND RESULTS

In 191 patients with drug refractory paroxysmal atrial fibrillation, a bolus of 12-24 mg of adenosine was administered after all 764 PVs were isolated. In the case of transient dormant conduction, a short infusion of dipyridamole 50 mg was given and a bolus of adenosine was repeated. In all cases, re-isolation was attempted guided by the activation pattern in the PV on a circular mapping catheter. Duration of adenosine-induced dormant conduction before and after dipyridamole was recorded as the time between administration of adenosine and cessation of dormant conduction either spontaneously or by catheter ablation. Transient dormant conduction was re-established by a single bolus of adenosine in 24 of 191 patients (12.6%). Mean duration of adenosine-induced dormant conduction before dipyridamole was 13.1 ± 6.4 s, whereas it was significantly longer at 218.9 ± 165.6 s after dipyridamole (P < 0.0001). Eighteen of the 24 PVs were re-isolated by catheter ablation before spontaneous cessation of dormant conduction, and in 6 cases dormant conduction disappeared spontaneously before PV re-isolation was achieved.

CONCLUSION

Dipyridamole significantly prolongs the effect of adenosine to unmask dormant conduction after PV isolation and may thus facilitate its elimination by catheter ablation.