Anatomical dilatation of the superior vena cava associated with an arrhythmogenic response induced by SVC scan pacing after atrial fibrillation ablation

Abstract

Background: The relationship between pulmonary vein (PV) arrhythmogenicity and its anatomy has been reported. However, that of the superior vena cava (SVC) has not been well discussed. Arrhythmogenic response induced by pacing stimulation at SVC might help with identifying SVC arrhythmogenicity. The purpose of this study was to investigate the relationship between the anatomical dilatation of SVC and the arrhythmogenic response induced by pacing at SVC.

Methods: Forty-three patients who underwent atrial fibrillation (AF) ablation were enrolled in this study. After PV isolation, scan pacing (up to triple extra stimulation following intrinsic sinus beats) was performed at SVC. The arrhythmogenic response was defined as following: (1) repetitive atrial responses, (2) non-sustained, and (3) sustained AF/ atrial tachycardia. To assess the dilatation of SVC, we measured the cross-sectional area of the SVC (SVC-area) using multi-planar reconstruction CT imaging.

Results: Arrhythmogenic responses were documented in 24 patients (Group 1). No arrhythmogenic responses were documented in the remaining 19 patients (Group 2). The SVC-area was significantly larger in Group 1 than Group 2 (3.1±0.9 vs. 2.2±0.8 cm², P=0.004). A multivariate analysis revealed only SVC-area was associated with arrhythmogenic responses (odds ratio=2.87, CI 1.05-7.82, P=0.04). Furthermore, AF recurrence rate was significantly higher in patients with SVC-area>2.56 cm² than those with SVC-area <2.56 cm² (9 [42.9%] of 21 vs. 3 [13.6%] of 22, P=0.026).

Conclusion: Dilatation of SVC was associated with an arrhythmogenic response, and the AF recurrence rate was significantly higher in patients with large SVC-area. Adjunctive catheter intervention for the SVC might be indicated in patients with a dilated SVC and an arrhythmogenic response.

Keywords: AF, atrial fibrillation; AT, atrial tachycardia; Arrhythmogenic response; Atrial fibrillation; CT, computed tomography; Catheter ablation; PV, pulmonary vein; SVC, superior vena cava; Scan pacing; Superior vena cava.

Fig. 1

Patient flow charts. Study flow diagram depicting the selection criteria for the patients included in the analysis. AF=atrial fibrillation, CT=computed tomography.

Fig. 2

“The scan single” protocol in the scan pacing indicate a single extrastimulus following intrinsic sinus beats with a coupling interval of 400 ms decreasing down to the atrial ERP. “The scan double” and “The scan triple” indicate double and triple extrastimuli following intrinsic beats, respectively. The black and shaded arrowheads indicate the intrinsic sinus beats and extrastimuli, respectively. S1, S2 and S3 indicate the first, second, and third extrastimuli, respectively.

Fig. 3

Measurement method of the SVC-area using a multi-planar reconstruction (MPR) CT image. A: The coronal view. The red line indicates the longitudinal axis of the SVC. B: The sagittal view. The red line indicates the longitudinal axis of the SVC. The yellow and blue lines indicate the LA roof and anterior wall level, respectively. C: The axial view at the LA roof level. The yellow circle indicates the SVC. D: The axial view at the LA anterior wall level. The blue circle indicates the SVC. Of note, The SVC was compressed by the dilated LA. SVC-area=cross-sectional area of the SVC, SVC=superior vena cava, LA=left atrium, Ao=ascending aorta.

Fig. 4

The arrhythmogenic responses induced by the SVC scan pacing. Overall, 24 (56%) of 43 patients were classified as “response positive” (Group 1), and the remaining 19 (44%) as “response negative” (Group 2). SVC=superior vena cava, NSAT/AF=non-sustained atrial tachycardia/ atrial fibrillation, RAR=repetitive atrial response.

Fig. 5

A: The SVC-area grouped by the SVC scan pacing response. The SVC-area was significantly larger in Group 1 (response positive) than Group 2 (response negative) (3.1±0.9 vs. 2.2±0.8 cm², P=0.004). B: The Kaplan–Meier analysis for the AF-free survival showed a significantly lower AF recurrence in patients with SVC-area <2.56 cm² than those with SVC-area>2.56 cm² (log-rank P=0.026). SVC-area=the cross-sectional area of the SVC, SVC=superior vena cava. AF=atrial fibrillation.

Fig. 6

Two representative cases. A: A patient with a large SVC in Group 1. Reproducible 6 beats RAR was induced by the SVC scan pacing (left panel). The red arrowheads indicate the RARs. Of note, the signal in the high right atrium (HRA) was followed by an SVC potential. B: A patient with a small SVC in Group 2. The SVC and RA were reconstructed three-dimensionally using the NavX system (right panel). SVC=superior vena cava, RAR=repetitive atrial response, HRA=high right atrium, RA=right atrium, CS=coronary sinus, p=proximal site, d=distal site, RV=right ventricle.