ECG Basics | Left Anterior Fascicular Block | LAFB electrophysiology| ECG Criteria of LAFB | скачать в хорошем качестве

ECG Basics | Left Anterior Fascicular Block | LAFB electrophysiology| ECG Criteria of LAFB |

Left anterior fascicular Block ECG criteria Left axis deviation (usually -45 to -90 degrees) qR complexes in leads I, aVL rS complexes in leads II, III, aVF Prolonged R wave peak time in aVL more than 45ms Electrophysiology In LAFB, impulses are conducted to the left ventricle (LV) via the posterior fascicle, which inserts into the inferoseptal wall of the LV along its endocardial surface Depolarisation spreads from endocardium to epicardium and thus the initial vector is directed downwards and rightwards, towards inferior leads. This produces small R waves in leads II, III and aVF, and small Q waves in leads I and aVL The major wave of depolarisation is slightly delayed and spreads upwards and leftwards, producing tall R waves in left-sided leads and deep S waves in inferior leads This overall delay of approximately 20ms (compared with normal simultaneous conduction via both fascicles) results in a slight widening of the QRS Because impulses reach the left-sided leads later than normal, there is an increase R wave peak time in aVL (time from onset of QRS to peak of R wave) Tip In LAFB, the QRS voltage in lead aVL may meet voltage criteria for LVH (R wave height more than 11 mm), but there will be no LV strain pattern.