Archives

  • 2018-07
  • 2018-10
  • 2018-11
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • 2019-08
  • 2019-09
  • 2019-10
  • 2019-11
  • 2019-12
  • 2020-01
  • 2020-02
  • 2020-03
  • 2020-04
  • 2020-05
  • 2020-06
  • 2020-07
  • 2020-08
  • 2020-09
  • 2020-10
  • 2020-11
  • 2020-12
  • 2021-01
  • 2021-02
  • 2021-03
  • 2021-04
  • 2021-05
  • 2021-06
  • 2021-07
  • 2021-08
  • 2021-09
  • 2021-10
  • 2021-11
  • 2021-12
  • 2022-01
  • 2022-02
  • 2022-03
  • 2022-04
  • 2022-05
  • 2022-06
  • 2022-07
  • 2022-08
  • 2022-09
  • 2022-10
  • 2022-11
  • 2022-12
  • 2023-01
  • 2023-02
  • 2023-03
  • 2023-04
  • 2023-05
  • 2023-06
  • 2023-07
  • 2023-08
  • 2023-09
  • 2023-10
  • 2023-11
  • 2023-12
  • 2024-01
  • 2024-02
  • 2024-03
  • Successful and safe catheter ablation is facilitated by an a

    2019-06-10

    Successful and safe catheter ablation is facilitated by an appreciation for anatomical particularities and surgical details. Morphological analysis of clinically documented VT is also important. In these patients, VT usually shows a left bundle branch block-like QRS morphology and inferior frontal plane axis. A right bundle branch block-like morphology may be present if the exit of the reentry circuit is located on the septal aspect of the RV free wall (Fig. 1). Therefore, preprocedural planning should include a careful review of imaging studies (computed tomography and magnetic resonance imaging), original surgical and interventional records, and 12-lead electrocardiograms (ECGs) of all documented VTs. Low-voltage myocardium is often identified at the RVOT and septal area of the right ventricle. During voltage mapping, attention should be paid to confirm the presence or absence of a conduction isthmus, which can support the macroreentrant VT circuit in these patients. Four common conduction isthmuses have been proposed in the Ki16425 after ToF repair [5] (Fig. 2). Type 1 isthmus is located between the RVOT (or adjacent RV scar) and tricuspid annulus (TA), type 2 isthmus is located between the RVOT scar and pulmonary valve (PV), type 3 isthmus is located between the PV and septal scar, and type 4 isthmus is located between the septal scar and TA. Among them, type 1 isthmuses are the most common, followed by type 3 isthmuses. Type 4 isthmuses are less common, and importantly, a type 2 isthmus does not theoretically exist in patients in whom the RVOT is reconstructed using a transannular patch. Peak-to-peak bipolar amplitudes are displayed and color coded with electrograms in the 3D mapping system. Local electrograms <1.5mV are usually defined as low voltage, and electrograms <0.5mV are defined as very low voltage [13]. At low-amplitude sites, high-voltage pacing (unipolar pacing with 10mA at a 2-ms pulse width) should be performed to confirm whether the site is an electrically unexcitable scar (EUS) [14]. Anatomical isthmuses are usually defined as areas between the boundaries (such as pulmonary artery=PA, TA, VSD patch, or EUS). After voltage mapping, programmed electrical stimulation is performed to induce VT, which is highly inducible by such stimulation. During the VT, abnormal local electrograms (fragmentation, late potential, mid-diastolic potential, or continuous activity) are frequently recorded from the wider areas of low-voltage myocardium. However, these abnormal electrograms do not always function as the essential components of the reentry circuit. In patients with hemodynamically tolerated VT, activation and entrainment mapping is performed. If the mechanism of the induced VT is macroreentry, the whole activation sequence can be mapped in the right ventricle [15]. Entrainment pacing from the critical isthmus of the reentry circuit shows concealed fusion between the original VT activation and pacing impulse, and the difference between the postpacing interval and cycle length of VT is <30ms [16,17]. Diastolic electrical activity is often recorded from the critical isthmus of the VT. A single RF application at the site may terminate the VT, and this suggests that the site is on the essential part of the reentry circuit. However, such a simple termination by RF application is insufficient to prevent VT recurrence, as described later. For unmappable VT (hemodynamic instability or termination during mapping or entrainment pacing), the locations of isthmuses in the reentry circuit are estimated by the results of pace mapping. Critical isthmuses of the reentry circuit would be the sites where the QRS morphology matches that of the VT (in more than 10 of 12 ECG leads) with an interval from the pacing stimulus to the onset of QRS morphology of >40ms [18]. If VT can be briefly tolerated, the catheter is moved to the presumed isthmus site during basic rhythm, and the VT is reinduced to confirm whether the position is on the circuit, either by entrainment mapping or by termination during RF delivery [9,19].