Cardiac Arrhythmia - Aberrant beats

                                                                
                 Cardiac Arrhythmia - Aberrant beats

A premature atrial contraction that occurs when the atrioventricular node is partially refractory will be conducted aberrantly and show a right bundle branch block morphology. Conduction passes down the septum after the left bundle branch has repolarised but before the right bundle branch has had time to do so. The impulse will thus be conducted normally through the left ventricle but will require aberrant pathways to depolarise the right ventricle.
The use of these abnormal pathways leads to a delay which consequently widens the QRS complex, which may exhibit an M-shaped R characteristic.

                                                                              Conduction

Electrocardiogram