Case
presentation
A 76-year-old man had a surgery of aortic valve replacement, mitral
valve and tricuspid valve repair, and surgical pulmonary vein isolation
(for severe aortic valve regurgitation, mitral valve regurgitation and
paroxysmal atrial fibrillation). After the operation, he showed a low
left ventricular ejection faction (LVEF 27%) with a QRS prolongation
from 98 ms to 132 ms (Figure 1A). On the fourth postoperative day, he
had a wide QRS tachycardia of left bundle branch block (LBBB)-like and
superior axis deviation with a heart rate of 156 bpm. (Figure 1A). The
baseline AH and HV interval was 90ms and 76ms. Programed stimulation
from the right ventricular apex (RVA) produced a fragmented potential
(Fg) following a spike potential (spike-Fg) at the His bundle region
(Figure 1B). With extra-stimulations, the fragmented
component was prolonged and the
sequence of these potentials became reversed (Fg-spike), thereby
inducing the wide-QRS complex tachycardia. This tachycardia
showed a LBBB-like morphology and
superior axis deviation with the tachycardia cycle length (TCL) of 420
ms (Figure 1B) and atrioventricular (AV) dissociation. What is the
mechanism of the LBBB morphology tachycardia with AV dissociation? What
do the spike and Fg potentials produced by RVA stimulation indicate?