Anodal left ventricular capture

Tracing
N° 7
Manufacturer Abbott Device CRT Field Left ventricular pacing
Patient

This 74-year-old man suffering from dilated cardiomyopathy with LBBB received a Abbott Unify Assura triple chamber defibrillator with implantation of bipolar RV and LV leads. LV stimulation was programmed with a distal LV –RV anode configuration. The LV stimulation threshold was measured.

Graph and trace

When the stimulation configuration was distal LV- RV ring (anode), RV capture was anodal. The ECG changed distinctly with LV stimulation only, with variations of the QRS between BiV (distal LV + RV ring captures) and LV only morphology (distal LV capture) at a <4 V pulse amplitude. The identification of anodal capture during BiV (actually pseudo-triventricular: anode RV + cathode RV + distal LV) stimulation is more challenging than during standard (cathode RV + distal LV) BiV stimulation. In this patient, the terminal QRS complex in some precordial ECG leads was slightly different. The true LV stimulation threshold was <1.0 V/0.4 ms. In absence of demonstrable hemodynamic superiority of an anodal capture, given the minimal changes in the ECG, and with a view to save energy, a pulse amplitude of 2.5 V/0.4 ms (without anodal capture) was programmed.

Comments

When the stimulation configuration was distal LV- RV ring (anode), RV capture was anodal. The ECG changed distinctly with LV stimulation only, with variations of the QRS between BiV (distal LV + RV ring captures) and LV only morphology (distal LV capture) at a <4 V pulse amplitude. The identification of anodal capture during BiV (actually pseudo-triventricular: anode RV + cathode RV + distal LV) stimulation is more challenging than during standard (cathode RV + distal LV) BiV stimulation. In this patient, the terminal QRS complex in some precordial ECG leads was slightly different. The true LV stimulation threshold was <1.0 V/0.4 ms. In absence of demonstrable hemodynamic superiority of an anodal capture, given the minimal changes in the ECG, and with a view to save energy, a pulse amplitude of 2.5 V/0.4 ms (without anodal capture) was programmed.

Message to remember

The measurement was made with LV stimulation programmed (distal LV - RV anode).

  1. atrial and LV stimulation; morphology similar to that of BiV stimulation (not shown on this tracing).
  2. marked widening of the stimulated QRS.
  3. LV stimulation with the second QRS morphology consistently present.
  4. loss of LV capture at a threshold at 0.75 V.
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