Left bundle branch block with intermittent QRS axis switching: Observation of a hypertensive patient for 18 years

Abstract

A 64-year-old man who had been prescribed antihypertensive drugs since 1971 attended our clinic in 1988 with hypertension and electrocardiographic abnormalities. An electrocardiogram revealed left axis deviation (LAD) in 1988 and slightly prolonged PQ intervals in 1993. Complete left bundle branch block (CLBBB) with LAD developed in May 1995. The wide QRS of the CLBBB had never returned to the normal narrow QRS and had intermittently alternated between LAD and normal axis. The PQ intervals were longer when the QRS axis showed LAD compared to that with normal QRS axis. The QRS complexes in leads V1-V3 revealed an R wave at LAD and a QS pattern at normal axis. During a deep breathing test, the QRS axis switched from normal axis to LAD at the end of forced expiration and also switched from normal axis to LAD within a few minutes after the exercise test. These results suggest that the shift of the QRS axis might be related to the tone of the autonomic nervous system.