Conduction characteristics in the left atrium of patients with perimitral atrial tachycardia post–pulmonary vein isolation

Figures

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  Figure 1. Anterograde and retrograde propagation maps. Step 1: An activation map was created while pacing from the high right atrium at 100 ppm. The earliest and latest activation sites (green dot) were marked on the map (anterograde propagation map) (Supplemental Video 1). Step 2: The ablation catheter was placed at the latest left atrial (LA) activation site (green dot) on the anterograde propagation map, and pacing at 100 ppm was performed. The LA activation map was created (retrograde propagation map) (Supplemental Video 2). Step 3: Induction test by burst pacing from the 3 atrial sites. AF = atrial fibrillation; AP = anteroposterior; AT = atrial tachycardia; LPV = left pulmonary vein; MVA = mitral valve annulus; PA = posteroanterior; PVI = pulmonary vein isolation; RPV = right pulmonary vein.

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  Figure 2. Conduction velocity measurements. A: The left atrium (LA) was divided into 7 segments. B: Example of conduction velocity measurement in the lateral segment of the LA. Left: Isochronal map of excitation propagation, with the distance between the earliest and latest activation sites in the lateral segment measured as 31.4 mm based on endocardial tracing. White arrows indicate the direction of conduction. Middleand Right: Acquired mapping points visualized as a mesh, revealing a time difference of 36 (113–77) ms between the 2 points. Consequently, conduction velocity was calculated as 31.4/36 = 0.87 m/s.

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  Figure 3. Flow chart of the study. After pulmonary vein isolation (PVI) in 179 patients with atrial fibrillation (AF), anterograde and retrograde propagation maps were created for all patients. Atrial burst pacing induced atrial tachycardia (AT) in 38 patients. Among those patients, perimitral atrial tachycardia (PMAT) was induced in 11 (PMAT group). No atrial tachyarrhythmias were induced in 56 patients (no induction group). LA = left atrium.

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  Figure 4. Segmental conduction velocity (CV) in each left atrial (LA) segment during anterograde and retrograde propagation. Green boxes indicate the no induction group. Red boxes indicate the perimitral atrial tachycardia (PMAT) group. ∗P <.05.

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  Figure 5. Direction-dependent conduction velocity (CV) changes and low-voltage areas (LVAs). A: Extent of LVAs (small, moderate, large) and corresponding anterograde and retrograde CVs in each LA segment are shown. Red line represents the perimitral atrial tachycardia group. Green line represents the no induction group. Even when the LVA extent was small, direction-dependent CV changes were significantly observed in the septum, lateral, and bottom segments. B: Representative case with direction-dependent CV changes. Left: Voltage map shows no LVA in the left atrium (LA). Middle: Anterograde CV in the LA lateral was normal (1.24 m/s). Right: Retrograde conduction map shows significant conduction delay in the LA lateral segment (0.46 m/s).

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  Figure 6. Relationship between direction-dependent conduction velocity (CV) changes and rotational direction of perimitral atrial tachycardia (PMAT). A: Representative case with induction of clockwise PMAT. Top: Anterograde propagation map shows slow conduction in the anterior left atrium (LA) (0.34 m/s), whereas the retrograde propagation map shows CV at the same segment was 0.55 m/s. Burst pacing induced a clockwise rotational PMAT (Supplemental Video 3). Bottom: Anterograde and retrograde CV in the anterior LA via a pacing study in patients with clockwise PMAT induction. B: Case of counterclockwise PMAT induction. Top: Anterograde propagation map did not show any slow conduction in the anterior LA (0.93 m/s); however, significant conduction delay (0.58 m/s) was observed in the retrograde propagation map. Burst pacing induced a counterclockwise rotational PMAT (Supplemental Video 4). Bottom: In 4 of 5 patients with a counterclockwise PMAT, the retrograde CVs were slower than the anterograde CVs.

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  Figure 7. Atrial tachycardia/atrial fibrillation (AT/AF) recurrence during follow-up. Kaplan-Meier curves for AT/AF recurrence in the 3 groups: the group that underwent ablation of the induced perimitral atrial tachycardia (PMAT), the group that did not undergo ablation of the induced PMAT, and the no induction group. ABL= catheter ablation.