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Electrophysiological Illustration of Unidirectional Conduction Block in the Right Upper Pulmonary Vein after Pulmonary Vein Isolation

https://doi.org/10.1007/s00392-025-02625-4

Oleg Dubrovin (Jena)1, C. Schulze (Jena)2, R. Surber (Jena)2, A. Große (Jena)2, C. M. Gross (Hansestadt Stendal)3, U. Zacharzowsky (Stendal)4

1Universitätsklinikum Jena ZIM1, Kardiologie Jena, Deutschland; 2Universitätsklinikum Jena Klinik für Innere Medizin I - Kardiologie Jena, Deutschland; 3Johanniter Akut- und Schwerpunktkrankenhaus Stendal gGmbH Zentrum Innere Medizin, Kardiologie, Angiologie und Rheumatologie Hansestadt Stendal, Deutschland; 4Johanniter Krankenhaus Stendal Stendal, Deutschland

 

Abstract:

Pulmonary vein isolation (PVI) is an established treatment method for rhythm control in patients with atrial fibrillation. In these procedures, verifying the success of pulmonary vein (PV) isolation is the goal of the intervention. In the current case, we observed a rare electrophysiological phenomenon with unidirectional block (exit block) from the right upper PV, evidenced by stimulation from the right upper PV ostium after the PVI.

Case Description:

Brief Patient Presentation

Patient A, 64 years old, has suffered from paroxysmal symptomatic (EHRA 3) atrial fibrillation and from typical atrial flutter for two years. A radiofrequency pulmonary vein isolation (RFA) was planned. The patient was taking NOAC due to a CHA₂DS₂-VASc score of 1 (hypertension). Other than arterial hypertension, the patient had no other significant comorbidities.

Electrophysiologic Procedure Description

After circumferencial RFA ablation of the right PV, persistent double potentials were observed on the lasso catheter electrograms despite prolonged ablation. These potentials could represent PV potentials or, less likely, far-field signals from the right atrium. The interval between this potential and the onset of the P-wave was 32 ms, which is near the borderline value relative to the known criterion for distinguishing far-field signals from the right atrium (30 ms).

During intravenous stimulation from the lasso catheter, positioned in the right PV ostium, we observed a spike directly following the stimulation artifact, suggesting capture of the PV myocardium but without atrial capture. This indicates a loss of conduction from the PV to the left atrium (Figure, arrow 3).

The PV stimulation artifacts coincided with intrinsic sinus activity. Here, the lasso catheter’s PV electrograms varied based on the refractory period of the venous myocardium following stimulation: a small, monospike appearance (far field from the atrium) was seen within the refractory period after stimulation (Figure, arrow 4), while fractionated double potentials were observed outside the refractory period (Figure, arrow 3). These double potentials resembled those seen during sinus rhythm without stimulation (Figure, arrows 5 and 1). Additionally, absence of PV capture was observed when the stimulus coincided with venous activation from sinus rhythm (Figure, arrow 2). This case illustrates the presence of unidirectional conduction toward the PV and absence of conduction from the PV into the atrium.

Ablation was continued until complete PV isolation with bidirectional block was achieved. After completing the procedure, dissociated PV activity was observed.

 

Conclusions:
In summary, the characteristics of unidirectional isolation of the PV are:

  1. Presence of double potentials in venous electrograms during sinus rhythm.
  2. Lack of atrial capture upon stimulation from the veins.
  3. Variation in PV electrograms during intrinsic rhythm (with overlapping stimulation) depending on the PV refractory period.
  4. Inconsistent capture of the PV due to potential overlap of stimulation with the refractory period following intrinsic atrial activation.

Unidirectional block from the PV underscores the importance of detailed analysis of venous electrograms.



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