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.
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.
The measurement was made with LV stimulation programmed (distal LV - RV anode).
- atrial and LV stimulation; morphology similar to that of BiV stimulation (not shown on this tracing).
- marked widening of the stimulated QRS.
- LV stimulation with the second QRS morphology consistently present.
- loss of LV capture at a threshold at 0.75 V.
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.