In the heart, a specialized group of cells called the sinoatrial (SA) node acts as a natural pacemaker by sending an electrical impulse to the ventricles of the heart at a regular interval, usually between sixty and one hundred times a minute, making the ventricles contract and pump blood through the arteries. To travel through the heart properly, the electrical impulse must move along particular pathways of specialized tissue. One of these pathways is called the bundle of His, and this bundle splits, or branches, into two separate bundles of specialized tissue, one diverted to the left ventricle, and one diverted to the right ventricle. In a normally functioning heart, the impulse travels through these bundles and makes both the left and right ventricle contract at the same time. Sometimes, however, one of the branches responsible for transmitting the electrical impulse to the ventricles cannot successfully do so, because the electrical impulse is blocked. Right-sided bundle branch block occurs more frequently than left-sided bundle branch block, and is most always the result of a defect present from birth. Other culprits may include high blood pressure, coronary artery disease, valve disease, cardiomyopathy, or prior heart attack resulting in damage to the electrical pathway. Impulses that run into a block in one of the bundles must seek other pathways, causing a delay in the electrical activation of a portion of the heart muscle, resulting in slightly asynchronous pumping of blood by the ventricles.
It is not unusual for people with bundle branch block to notice no symptoms, although a test called an EKG (electrocardiogram) can show the abnormal electrical activity that results. This is often the only way that doctors become aware of bundle branch block in their patients.
In patients with two diseased bundles, the impulses may be blocked to the extent that no electrical activity reaches the ventricles and they must rely on their own electrical activity (idioventricular rhythm), which may be slow enough to cause symptoms such as weakness, lightheadedness, or even fainting.
If a patient has no discernable symptoms and there is nothing else wrong with the heart, but bundle branch block has been identified as the result of testing, the condition is generally not cause for alarm, and no treatment is indicated. However, doctors may perform tests such as echocardiograms or stress tests in an effort to find the cause of the abnormality.If bundle branch block occurs as a result of coronary artery disease, it may be necessary to treat the underlying condition. Treatment may be as simple as dietary modification and medication, or may include angioplasty, stents or surgery to clear arterial blockage.
For those who have suffered heart attack or other damage to the heart muscle causing blockage in both electrical bundles, an electronic device called a pacemaker may be used to generate the electrical impulse that the heart cannot properly generate itself. The pacemaker works by using wires that are attached to the heart wall and a small device called a pulse generator, containing a battery and several circuits, implanted in the body. After the implantation of a pacemaker, it is important to regularly check in with a doctor to make sure that both the device and the heart are working as they should be.
