A cardiac conduction disorder occurs when the electrical signals that govern the heart’s rhythm are disrupted, leading to an irregular heartbeat. The heart functions like a pump, relying on precise electrical timing to ensure the upper and lower chambers contract in a coordinated way. When the electrical impulse is delayed, blocked, or misfired, the heart cannot effectively circulate oxygenated blood throughout the body.
Understanding the Heart’s Electrical Circuit
The heart’s electrical system is a specialized network responsible for generating and transmitting the signal that makes the heart contract. The process begins in the sinoatrial (SA) node, which is often called the heart’s natural pacemaker, located in the upper right chamber, or atrium. This node spontaneously generates an electrical impulse, typically between 60 and 100 times per minute in a resting adult. The signal then quickly spreads across both upper chambers, causing them to contract and push blood into the lower chambers.
The impulse next reaches the atrioventricular (AV) node, which acts as a gatekeeper positioned near the center of the heart. The AV node briefly delays the signal, allowing the upper chambers to fully empty their blood into the lower chambers, or ventricles, before the next contraction begins. After this short delay, the signal travels down the bundle of His and into the Purkinje fibers, which rapidly distribute the electrical signal throughout the muscular walls of the ventricles.
A conduction disorder represents a problem with this delicate timing mechanism. The issue can manifest as a block, where the signal is completely stopped, or a delay, where the signal slows down significantly at any point along the pathway, such as in a heart block or bundle branch block. These disruptions result in an abnormal heart rhythm, or arrhythmia, because the chambers are no longer contracting in the correct, synchronized sequence.
Recognizing the Signs
The lack of proper electrical timing in the heart can translate into several noticeable physical symptoms. One of the most common signs is experiencing palpitations, which are sensations of the heart fluttering, pounding, or skipping a beat. This feeling is a direct result of the heart’s chambers contracting irregularly or too quickly.
When the heart’s pumping action is compromised due to poor electrical coordination, the body may not receive enough blood flow, leading to feelings of lightheadedness or dizziness. A more serious manifestation of reduced blood flow to the brain is syncope, which is a sudden, temporary loss of consciousness, or fainting. Additionally, many people with a conduction disorder report persistent fatigue and shortness of breath, particularly during physical activity.
Confirming a Conduction Disorder
Physicians use specialized diagnostic procedures to objectively identify and classify problems within the heart’s electrical system. The most common initial tool is the Electrocardiogram (ECG or EKG), which is a non-invasive test that records the heart’s electrical activity over a short period. The ECG can immediately show if the heart rhythm is abnormal or if there is a delay in the electrical signal’s travel time.
Since conduction issues can be intermittent, a physician may order ambulatory monitoring, such as a Holter monitor or an event recorder. A Holter monitor is a portable device worn for 24 to 48 hours that continuously records the heart’s rhythm. An event recorder is activated by the patient only when symptoms occur, helping to capture less frequent abnormalities.
For a more detailed assessment, an Electrophysiology (EP) Study may be performed in a specialized lab. During an EP study, thin tubes with electrodes, called catheters, are threaded through blood vessels up to the heart to record the electrical signals directly from inside the chambers. This procedure allows the cardiologist to create a detailed map of the electrical pathways and pinpoint the exact location of a block, delay, or an abnormal circuit. The EP study is often performed to determine the best course of treatment, especially when considering advanced interventions like ablation.
Management and Treatment Options
Treatment for a conduction disorder is determined by the specific type and severity of the electrical problem. In some cases, such as a mild first-degree heart block or a bundle branch block with no symptoms, no intervention may be necessary, but regular monitoring is maintained. Managing underlying conditions, like high blood pressure or diabetes, can also help stabilize the heart’s overall health and electrical function.
For patients whose conduction disorder causes a heart rate that is dangerously slow, a permanent pacemaker is the standard treatment. This small, battery-powered device is typically implanted under the skin near the collarbone, with wires, or leads, extending to the heart chambers. The pacemaker constantly monitors the heart’s natural electrical activity, delivering a small electrical impulse to stimulate a contraction when it detects a beat that is too slow or missed entirely.
Another advanced treatment is catheter ablation, which is used to treat problems involving an abnormal “short circuit” or extra electrical pathway causing a fast heart rhythm. This minimally invasive procedure involves guiding a catheter to the area of faulty tissue identified during an EP study.
The catheter then delivers energy, often radiofrequency heat or cryoablation cold, to carefully destroy the small area of tissue causing the irregular signals. This process creates a tiny scar that blocks the abnormal electrical impulse, helping to restore a normal heart rhythm. For certain fast heart rhythms, antiarrhythmic medications may also be used to help control the rate or rhythm, though these are often considered alongside or before an ablation procedure.