An electrical delay or blockage in the conduction pathway that sends impulses down the left anterior fascicle of the left bundle.
•Prolonged QRS (0.08-0.11 sec).
•Left axis deviation (usually > -45 degrees).
•Leads 1 and aVL: small Q waves and tall R waves.
•Leads 2, 3 and aVF: small R waves and deep S waves.
•No other obvious cause of these findings (e.g. left ventricular hypertrophy or inferior wall myocardial infarction).