Transient complete atrioventricular block occurring 1 week after radiofrequency ablation for the treatment of atrioventricular nodal re-entrant tachycardia

Late reversible complete atrioventricular block and PR interval normalization after antegrade slow pathway ablation for atrioventricular nodal re-entrant tachycardia with pre-existing PR prolongation

Late complete atrioventricular block (CAVB) is a rare periprocedural complication in the treatment of atrioventricular (AV) nodal re-entrant tachycardia. However, it can necessitate permanent pacemaker implantation. We present a case of late CAVB that developed during the periprocedural period. Its pathogenesis was attributed to the indirect or functional effects on the fast pathway of the AV node due to the presence of paroxysmal supraventricular tachycardia with PR prolongation. Additionally, PR prolongation regressed to within the normal range after curing the late CAVB, and the advanced AV block with treadmill exercise stress test also improved 1:1 AV conduction with time. Periprocedural complications such as bradyarrhythmia may be reversible if late CAVB occurs within a few weeks after ablation. Thus, urgent permanent pacemaker implantation should be carefully considered.

Learning objective

Late high-grade atrioventricular (AV) blocks can develop during the periprocedural period even if antegrade slow pathway ablation does not result in a complete AV block. Late high-grade AV block is a relatively rare periprocedural complication. However, it can necessitate permanent pacemaker implantation. Additionally, if a late high-grade AV block develops within a few weeks after ablation, bradyarrhythmia—such as periprocedural complications—may be reversible and indicate that permanent pacemaker implantation should be carefully considered.

Coronary artery pathophysiology after radiofrequency catheter ablation: review and perspectives

BACKGROUND

Radiofrequency ablation (RFA) has proven to be an effective and safe treatment in patients with ventricular and atrial tachyarrhythmias. Among complications arising after RFA, the incidence of coronary artery (CA) injury is exceedingly low. When CA injury does occur, however, it can be clinically devastating. The proximity of CAs to common ablation sites suggests that the relationship between RFA and CA perfusion pathophysiology is important for optimal lesion formation and safe arrhythmia treatments.

OBJECTIVE

Although others have described the presentation and outcomes of patients with CA injury after ablation, a review that consolidates the mechanisms of CA injury after RFA has yet to be presented in the cardiology literature.

METHODS

We conducted an extensive literature search of studies published over the past 30 years that relate the biophysics of RFA with CA perfusion pathophysiology and injury.

RESULTS

We present a review of the dynamic relationship between RFA and CA perfusion. We describe RFA lesion pathology, mechanisms of CA injury from RFA, and factors that influence lesion formation, such as convective cooling and the shadow effect.

CONCLUSION

We summarize methods to mitigate CA injury after RFA and propose new research avenues to optimize lesion formation and safe arrhythmia treatments when tissue is ablated in the vicinity of CAs.

Cryoablation compared with radiofrequency ablation for atrioventricular nodal re-entrant tachycardia: analysis of factors contributing to acute and follow-up outcome

AIMS

The efficacy of transvenous Cryoablation (Cryo), for the treatment of atrioventricular nodal re-entry tachycardia (AVNRT), when compared with radiofrequency (RF) ablation, requires further investigation.

METHODS AND RESULTS

We sought to compare the acute- and follow-up results of 71 cases each of Cryo and RF for AVNRT using a retrospective matched case-control study design and aimed at identifying patient and procedural factors that may predict success with each strategy. Primary failure of Cryo (thus necessitating RF at the same sitting) was seen in 11 (15.4%) cases, whereas there were two (2.8%) primary failures with RF (P<0.01). Patients in the Cryo group had significantly higher arrhythmia recurrence [14 (19.8%)] when compared with the RF group [4 (5.6%)] (P<0.01). The incidence of recurrence following Cryo was significantly higher if an echo beat was still inducible after ablation than if complete slow pathway block was achieved (7/19, vs. 4/46, P<0.001). The median number of Cryo lesions was significantly lower in patients who had recurrence compared with those who did not (1.5 vs. 3.0, P=0.02).

CONCLUSION

We have observed a much higher primary failure and recurrence rate with Cryo when compared with RF for AVNRT. It may be possible to decrease this high recurrence rate by aiming to achieve complete slow pathway block and by increasing the number of Cryo lesions.

Change in Size of Lesions Over 3 Weeks After Radiofrequency Ablation of Left Ventricle

INTRODUCTION

The initial success or failure of radiofrequency ablation (RFA) does not always reflect the long-term outcome that can lead to complications such as late atrioventricular block or recurrence of accessory pathways. We hypothesize that these occurrences may be due to a change in lesion size over time.

METHODS AND RESULTS

Intramural RFAs were performed on five greyhounds at thoracotomy using an epicardial approach into the left ventricular (LV) wall. Twenty-one gauge needle electrode ablations were created in the anterior aspect of the left ventricle. Radiofrequency energy was delivered at 600 Hz for 60 seconds and at an electrode temperature of 90 degrees C. Eight ablations were created in each greyhound and the chest was closed. After 3 weeks, a further eight ablations were created under the same conditions in the lateral aspect of the LV, ensuring they were well away from the chronic lesions, and the dogs were sacrificed an hour later. All lesions were removed, stained with Gomori Trichrome and measured. There was no significant difference in lesion size detected in the 1-hour-old lesions compared with 3-week-old lesions. Acute lesions were well demarcated by an area of fibrous scar and a central necrotic region. Chronic lesions showed chronic inflammatory cells and strands of collagen.

CONCLUSIONS

This study shows no change in lesion dimension over time and hence a change in size may not contribute to a change in RFA outcome over time.

Prediction of Clinical Recurrence of Atrioventricular-Nodal Reentrant Tachycardia (AVNRT) After Successful Slow Pathway Ablation

BACKGROUND

Even after successful slow pathway (SP) ablation for atrioventricular-nodal reentrant tachycardia (AVNRT), there may be clinical recurrence in certain patients and it is clinically important to be able to predict that.

METHODS AND RESULTS

In 97 patients with common type AVNRT, the effective refractory period (ERP) of the fast pathway (FP), SP-ERP, and prolongation of the atrio-His (AH) interval (AH) at the time of jump-up phenomenon were investigated. In patients with residual SP, parameters were re-evaluated in a similar manner. SP was successfully ablated and AVNRT was not inducible in all the patients, but residual SP was observed in 54 of the 97 patients, and there was late clinical recurrence in 10 patients (10/54 patients with residual SP and 0/43 without residual SP, p=0.002). The changes in FP-ERP before and after ablation (DeltaFP-ERP) did not differ between recurrent and non-recurrent patients. Among the patients with residual SP, DeltaSP-ERP did not differ between the groups. However, the changes in DeltaAH before and after ablation (DeltaDeltaAH) were larger in non-recurrent (24+/-30 ms) than in the recurrent patients (4+/-7 ms, p=0.042).

CONCLUSIONS

In patients with AVNRT, the residual SP and changes in DeltaAH after successful SP ablation might be useful indices of clinical recurrence.