Ectopies from the superior vena cava after pulmonary vein isolation in patients with atrial fibrillation

Episodes of atrial fibrillation (AF) are mainly initiated by triggers from pulmonary veins (PVs). The superior vena cava (SVC) has been identified as a second major substrate of non-PV foci, but the electrophysiologic features of the SVC have not been fully investigated. We hypothesized that SVC ectopies are suppressed by predominant features of PV ectopies and tend to appear after PV isolation (PVI). We evaluated the electrophysiological characteristics and clinical implications of SVC ectopies in patients with AF during catheter ablation using high-dose isoproterenol and the atrial overdrive pacing maneuver. The manifestation patterns and modes of onset (coupling interval and appearance interval) of ectopies from both the PVs and SVC were investigated. 205 patients were enrolled [153 males and 52 females; mean age 64 +/- A 10 years; paroxysmal in 143 patients (69.8 %), persistent in 40 (19.5 %), and long-standing persistent in 22 patients (10.7 %)]. Before PVI, PV ectopies were detected in 182/205 patients (89 %). SVC ectopies were rarely observed before PVI but were significantly more frequent after the completion of PVI (3/205 vs. 14/205 patients, p = 0.011). The coupling interval (CI) and % CI (CI/preceding the A-A interval x 100) of PV ectopies were significantly shorter than those of SVC ectopies (211 +/- A 78 vs. 282 +/- A 106 ms, p = 0.021, and 34 +/- A 9 vs. 51 +/- A 17 %, p < 0.001, respectively). The appearance intervals of the PV ectopies were shorter than those of the SVC ectopies (6.3 +/- A 4.0 vs. 10.7 +/- A 6.7 s, p = 0.030). During repeat procedures, PVs with reconnection to the left atrium were less frequently observed in patients with SVC firing than in patients without SVC firing (1.7 +/- A 1.5 vs. 2.9 +/- A 1.1 PVs, p = 0.029). We demonstrated that PVI tends to manifest SVC ectopies with less spontaneous activity and that an elimination of predominant ectopies from the PVs may affect appearance of SVC ectopy.