Can lafb cause tachycardia? is medication the first and/or best treatment option?

Possibly: Left anterior fascicular block is blockage of one of the electrical branches that delivers electrical signals to part of the left ventricle. There aren't a lot of great studies but some small studies that suggest it is associated with increased risk of atrial fibrillation(which can be a form of tachycardia), hypertension, heart failure, and sudden cardiac death. There is no treatment.

LAFB: if you mean left anterior fascicular block - then no. It does not cause tachycardia. But can be a sign of myocardial ischemia and may precede ventricular tachycardia in the setting of a myocaridal infarction.