The angle of the tines before the pull and hold test predicts engagement of the tines in Micra leadless pacemaker implantation

Figures

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  FIGURE 1. Micra leadless pacemaker and tine angles. (A) Micra leadless pacemaker and its tines. Four electrically isolated nitinol tines are placed at the tip of the device. Nitinol is a shape memory metal, and all tines are pre‐shaped to directed inward toward the body of the device. (B) Assessment of the angle of the tines with right anterior oblique (RAO) view of the cine‐image. The angle between each visible tine and the body of the pacemaker was calculated before the pull and hold test. In this representative case, the upper tine with an angle of 3.4 degrees was engaged. On the contrary, the bottom tine with an angle of 16.4 degrees was not engaged. The differences in tine angles of the opposing pair of tines were also calculated (16.4–3.4 = 13 degrees in this patient).

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  FIGURE 2. The angle of the tines with and without engagement. The angle of the engaged tines was significantly lower than the non‐engaged tines. All tines with angles <10 degrees were engaged.

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  FIGURE 3. Receiver operating characteristic (ROC) curve for prediction of tine engagement. (A) ROC curve of the tine angles for prediction of tine engagement. Area under the curve (AUC) was calculated to be 0.854 (95% CI: 0.815–0.894). (B) ROC curve of the differences in tine angles between contralateral tines for prediction of tine engagement. AUC was calculated to be 0.876 (95% CI: 0.817–0.936).

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  FIGURE 4. Differences in tine angles between the contralateral tines. The visible tines were paired with contralateral tines. The tines with lower angles compared to the contralateral tines were selected and analyzed for possible engagement. The differences between the engaged tines were significantly higher than the non‐engaged tines. All tines in which the tine angle was >5 degrees lower than the opposing tines were engaged.

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  FIGURE 5. The tine angles between the contralateral tines in different engagement statuses of contralateral tines. The data of difference in tine angle between opposing tines were divided into three groups and compared. Group 1: both sides not engaged. Group 2: only one side engaged. Group 3: both sides engaged. The differences of tine angles between contralateral tines were significantly different between the three groups (p = .0001).

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  FIGURE 6. Tines in which the engagement could have been predicted before the pull and hold test. In total, 143 (43.9%) tines could have been predicted as engaged tines before the pull and hold test.

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  FIGURE 7. Example of the open tine in LAO view. The septal tine (red circle) is visually open before the pull and hold test with a clear difference between the opposing tine.