Pattern | QRS morphology | Origin of ectopic beat | Comment | Figure |
Common patterns in athletes | ||||
Infundibular | LBBB with late precordial transition (R/S=1 after V3) and inferior axis. | Right ventricular outflow tract. | Usually benign. | Figure 1A |
LBBB and inferior axis but with small R-waves in V1 and early precordial transition (R/S=1 by V2 or V3). | Left ventricular outflow tract. | Usually benign. | Figure 1B | |
Fascicular | Typical RBBB with superior axis and QRS <130 ms. | Left posterior fascicle of the left bundle branch. | Usually benign. | Figure 1C |
Typical RBBB with inferior axis and QRS <130 ms. | Left anterior fascicle of the left bundle branch. | Usually benign. | Figure 1D | |
Uncommon patterns in athletes | ||||
Atypical RBBB and QRS ≥130 ms. | Mitral valve annulus, papillary muscles or left ventricle. | May be associated with myocardial disease. | Figures 3 and 5 | |
LBBB with superior or intermediate axis. | Right ventricular free wall or interventricular septum. | May be associated with myocardial disease. | Figure 4 |
LBBB: negative QRS complex in lead V1.
Atypical RBBB: positive QRS complex in lead V1 not resembling a typical RBBB.
Typical RBBB: rSR’ pattern in lead V1 and an S-wave wider than R-wave in lead V6.
Inferior QRS axis: positive QRS in the inferior leads (II, II, aVF).
Superior QRS axis: negative QRS in the inferior leads aVF.
Intermediate QRS axis: positive QRS complexes in both aVF and aVL.
Precordial transition: precordial lead in which the QRS complex becomes predominantly positive.
LBBB, left bundle branch block; RBBB, right bundle branch block.