SEPTAL Q WAVES IN V6 LEAD DISAPPEAR DURINGNARROW QRS SUPRAVENTRICULAR TACHYCARDIA: ANEW ECG OBSERVATION

摘要

Background: Q waves in left precordial leads in normal hearts are generated by left-to-right activation of the ventricular septum. We present that Q waves in V6 disappear during narrow QRS supraventricular tachycardia (SVT), compared with the QRS in sinus rhythm (SR). Methods: Eighteen SVT patients showing Q waves in V6 during SR were enrolled. Q-wave depth in V6 was measured during SR versus SVT. Atrial extrastimulus (S1S2) testing was performed in 5 pts to see whether the Q-wave depth in V6 could be changed in response to premature (S2) stimulation. Results and Conclusions: During SR, the magnitudes of Q waves in V6 were 1.2+-0.6 mm. During SVT (cycle length, 338+-38), those were decreased to zero. With atrial extrastimulus testing, Q-wave completely disappeared at V1V2 intervals of approximately 400 msec. The onset of R wave gradually shifted to earlier timing relatively to septal Q activation, suggesting, "Q-wave masking" by the R wave.