Left anterior fascicular block can cause ventricular tachycardia (arrhythmia) that may originate close to the anterior fascicle can be cured by RF ablation (radio frequency waves to remove blockage). The medical issue is electrophysiology so investigation remains mostly with EKG. A treadmill stress test can determine if blockage can be provoked by observing ekg output under stress. There can be a rhythm issue associated with abnormal postassium concentraction and blood test would be appropriate.
You don't provide much information such as your symptoms, if medicated during test, what was the heart rate during test, etc. Any other medical issues?