A bundle branch block is a condition affecting the heart’s internal electrical wiring system. It represents an issue with the electrical signals that coordinate the heart’s pumping action, rather than a physical blockage of blood flow within the heart’s arteries. This condition causes a delay or interruption in the electrical impulses as they travel through specific pathways in the heart.
The Heart’s Electrical System and Bundle Branch Block
The heart’s ability to pump blood relies on a coordinated electrical system. An electrical impulse originates in the sinoatrial (SA) node, often called the heart’s natural pacemaker, located in the upper right chamber. This initial signal spreads across the heart’s upper chambers, causing them to contract and push blood into the lower chambers. The impulse then travels to the atrioventricular (AV) node, where it pauses briefly before continuing its journey.
From the AV node, the electrical signal moves down the bundle of His. This bundle then divides into two branches: the right bundle branch and the left bundle branch. These bundle branches extend into the heart’s lower chambers, the ventricles, where they transmit the electrical impulses to specialized fibers called Purkinje fibers. This network ensures that the left and right ventricles contract in a synchronized manner, pumping blood out of the heart.
A bundle branch block occurs when there is a delay or interruption in the electrical signal traveling along either the right or the left bundle branch. If the right bundle branch is affected, it’s called a right bundle branch block (RBBB), delaying the electrical activation of the right ventricle. Conversely, if the left bundle branch is disrupted, it’s a left bundle branch block (LBBB), delaying the electrical signal’s reach to the left ventricle. This electrical delay means the ventricle with the block will contract slightly later than the other, leading to uncoordinated contractions.
Recognizing Bundle Branch Block
Many individuals with a bundle branch block experience no noticeable symptoms. The condition is often discovered incidentally during a routine medical examination, such as an electrocardiogram (ECG or EKG). If symptoms do occur, they are typically related to an underlying heart condition rather than the block itself. These symptoms might include dizziness, fainting, or shortness of breath.
The main method for diagnosing a bundle branch block is an electrocardiogram. An ECG is a test that records the heart’s electrical activity. This diagnostic tool can detect patterns in the heart’s electrical signals that indicate a delay or blockage in one of the bundle branches. The ECG helps determine which side of the heart is affected and the extent of the electrical delay.
Underlying Causes and Next Steps
A bundle branch block can arise from various underlying heart conditions. Common causes include coronary artery disease, which narrows the heart’s arteries, or a previous heart attack that may have damaged heart muscle. High blood pressure, heart valve diseases, and conditions that weaken or stiffen the heart muscle, known as cardiomyopathies, can also cause a bundle branch block. Inflammation of the heart muscle (myocarditis) or certain congenital heart defects can also be causes.
A bundle branch block itself often does not require specific treatment. Instead, treatment focuses on identifying and treating any underlying heart condition causing the block. For instance, managing high blood pressure or addressing heart failure symptoms is prioritized. If a right bundle branch block is found in an otherwise healthy individual, treatment may not be necessary beyond regular monitoring.
However, in certain situations, such as when a bundle branch block leads to fainting spells or occurs with heart failure, a pacemaker may be considered to regulate the heart’s rhythm. Patients diagnosed with a bundle branch block should have regular medical follow-ups. Informing all healthcare providers about the condition is also important, as a bundle branch block can influence the interpretation of other cardiac tests.