Background:

Catheter ablation of parahisian premature ventricular contractions (PVCs) can be challenging with high periprocedural risk of atrio-ventricular (AV) block. Catheter stability is the key prerequisite to provide a safe and effective catheter ablation in such vulnerable areas.

Case presentation:

A 57-year-old female patient with a history of Takotsubo syndrome presented to the emergency department with chest pain and palpitations. Acute myocardial ischemia was excluded by negative serial serum troponin levels. Electrocardiogram (ECG) showed sinus rhythm with frequent monomorphic PVCs (bigeminy). PVC morphology showed a narrow QRS complex (QRS width of 100 ms) with nearly identical axis compared to the QRS complexes in sinus rhythm and a left bundle branch block (LBBB) pattern, suggesting a parahisian origin.

The patient had a known history of highly symptomatic PVCs with a burden of 27 % per 24 hours on Holter ECG. Initial betablocker therapy had to be stopped due to symptomatic sinus bradycardia and syncope.

An electrophysiologic (EP) study was performed after written informed consent including the increased high risk of periprocedural AV-block with need for pacemaker implantation.

The EP study was performed using an electroanatomic 3D mapping system, a contact force sensing irrigated 3.5mm tip RF catheter and a long non-steerable sheath. The earliest activation area of the PVC was detected in the right ventricle (RV), slightly inferior to the His bundle. Earliest activation was 23 ms to the onset of the QRS in lead II. Unipolar EGM showed QS morphology. A His potential was detected only 3,5 mm to the site of PVC origin, where pace mapping showed a 97% pattern matching to the clinical PVC.

Shortly after the start of power-controlled irrigated RF applications with an energy titration of 10 to 15 Watts, multiple junctional beats with intermittent AV block appeared. Ablation was stopped immediately. A total of 5 attempts of RF applications had to be stopped abruptly after 5 to 10 seconds, due to intermittent AV block, all with complete recovery of the AV block, but also the PVCs. Further attempts more distant to the His bundle showed no effect on the PVC.

Eventually, successful ablation of the parahisian PVC could be performed after using the “reversed C-curve” technique for positioning of the ablation catheter (forming a reversed C letter), providing excellent catheter stability. The clinical PVC disappeared after 5 seconds of RF time during the 1^st RF application. Continuously stable junctional complexes at this site without appearance of any AV block could be recorded, therefore a second bonus application was added. In total two RF applications (each 60 seconds, with 15 to 30 Watt) were applied.

Holter ECG on the first postoperative day revealed a significant decreased PVC burden less than 1 % in 24 hours, without any further AV conduction disorders which was related to improved clinical symptoms.

Conclusion:  Utilization of the “reversed C-curve” technique to improve catheter stability at the site of origin may increase success and safety during ablation of parahisian PVCs.

Figure 1. 3D-activation map of the parahisian PVC from the RVOT (in LL projection on the left), visualization of tag points in glass mode (in RAO projection on the right). Ablation catheter in “reversed C-curve” position.

LL: left lateral, RAO: right anterior oblique, yellow tags: His Bundle, white tags: RF application sites.