To understand bundle branch blocks, let s start with what bundles mean and why they are there. Your heart is an organ of muscles which contract at different times to beat and keep blood flowing. For these muscles to contract in sequence, they need electrical impulses which travel through these bundles. So, the bundles are like electrical wires. Your heart has 3 bundles branches, one on the right side and 2, an anterior and a posterior on the left side. A bundle branch block refers to the blockage or transection of one of these bundles either by a heart attack, an inflammation, a scar or some other things. A single bundle branch block that is, a right bundle branch block, a left anterior fascicular block or a left posterior fascicular block usually not problematic at all. A double branch block keeps us on the look out for a triple bundle branch block which is also a complete heart block, one of the reasons people get pacemakers. Now, you have an idea about bundle branch blocks and the most important thing is to talk to your doctor and see if you need a stress test or something similar if you have risks for heart attacks like, age(men above 45, women above 55), family history, hypertension, diabetes, smoking, sedentary lifestyle, overweight or cholesterol problems.