Comparison of Unipolar and Bipolar Voltage Mapping for Localization of Left Atrial Arrhythmogenic Substrate in Patients With Atrial Fibrillation

Figures

• 

  Figure 1. Voltage mapping in sinus rhythm: Three-dimensional distribution of bipolar and unipolar LVA in a patient during SR with a bipolar threshold <0.5 mV. The top row indicates the bipolar map, the middle row shows the unipolar map, and the bottom row is a map of the point by point comparison between the two maps: if both points are below their indicated voltage thresholds (LVA), the point is colored red, if both are above [high voltage areas (HVA)] in white and with different classification (bipolar low voltage, unipolar high voltage) in dark-blue and (bipolar high voltage, unipolar low voltage) in turquoise. In the left column, the anterior view is shown and on the right the posterior view. Each geometric shape represents a point on the map where the corresponding signal is shown in the middle column. The upper unipolar threshold values were obtained by determining which threshold provided the best match of points between unipolar and bipolar. For visualization, the lower value was manually optimized to obtain the best visual match.

• 

  Figure 2. Voltage mapping in atrial fibrillation: Three-dimensional distribution of bipolar and unipolar LVA in the same patient as Figure 1 during AF with a bipolar threshold <0.35 mV. The top row indicates the bipolar map, the middle row shows the unipolar map, and the bottom row is a map of the point by point comparison between the two maps: if both points are below their indicated voltage thresholds (LVA), the point is colored red, if both are above [high voltage areas (HVA)] in white and with different classification (bipolar low voltage, unipolar high voltage) in dark-blue and (bipolar high voltage, unipolar low voltage) in turquoise. In the left column, the anterior view is shown and on the right the posterior view. Each geometric shape represents a point on the map where the corresponding signal is shown in the middle column. The electrogram marked with a triangle is an example of “voltage cancelation” in the bipolar recording (0.13 mV), while the voltages on both unipolar recordings are high (0.98 and 0.91 mV); this occurs because the unipolar electrograms have the same shape and same timing and their subtraction results in a near-zero bipolar voltage value.The upper unipolar…

• 

  Figure 3. Regional agreement of unipolar and bipolar substrate classification. Eleven anatomical regions were annotated in all 28 patient geometries and analyzed in SR and AF. Each region visualized on this example geometry is colored according to the mean percentage of concordantly categorized mapping sites (unipolar vs. bipolar voltage mapping) with regard to LVA.

• 

  Figure 4. ROC curve regarding identification of LVA for each rhythm and bipolar threshold. Each line represents the sensitivity and specificity for varying unipolar thresholds for the four different bipolar voltage thresholds that are reported in literature for SR and AF. The optimal unipolar thresholds for the corresponding bipolar thresholds were found for each patient and the median value of these patient specific thresholds is given in the figure.

• 

  Figure 5. Relationship between the bipolar and unipolar threshold in SR (blue) and AF (red). The unipolar threshold with highest concordance to the bipolar map is shown for different bipolar thresholds and each individual patient (blue and red dots for SR and AF, respectively). Standard deviation is represented by bars. The optimal unipolar threshold is identified as the optimal point on the ROC curve of each bipolar threshold using all patients. Linear regression shown as dotted lines, depending on the rhythm (SR blue, AF red). Pearson correlation coefficient (r) is provided. For every unipolar threshold, >89% of points matched in SR and >86% in AF.

• 

  Figure 6. Violin plot showing the percentage of points which match between unipolar and bipolar classification. The results are shown for each rhythm and corresponding bipolar threshold over all patients. Results for a common unipolar threshold for all patients are shown in blue. Results for patient-individual unipolar thresholds are shown in pink. The green squares indicate the median value for each set.

• 

  Figure 7. Histogram and corresponding boxplot showing the percentage of points matched in SR (A) and AF (B) for each of the three electrode distance categories. Each category is shown in a different color: 2 mm (blue), 6 mm (red), all (green). p-value calculated with paired-sample t-test.