Transient prominent anterior QRS forces in the setting ST segment elevation coronary syndrome: Left septal fascicular block.

Numerous successive publications have shown that transient prominent anterior QRS forces (PAF) in the setting of acute coronary syndrome (ACS) is suggestive of critical proximal obstruction of left anterior descending coronary artery (LAD) before its first septal perforator branch (S1). Transient ischemia of the left septal fascicle resulting in left septal fascicular block has been proposed as the causative mechanism. We present a case of acute inferior ST-elevation myocardial infarction caused by acute proximal occlusion of the right coronary artery associated with proximal critical obstruction of the left anterior descending coronary artery.