A right ventricular conduction delay describes a slowdown in the heart’s electrical signal as it travels to the right lower chamber, or ventricle. This delay causes the right ventricle to contract slightly later than the left, disrupting the synchronized timing required for efficient pumping. The medical term for a significant form of this delay is Right Bundle Branch Block (RBBB). This condition is an electrical abnormality, not a physical obstruction of a blood vessel or valve.
The Heart’s Electrical Wiring: How Conduction Works Normally
The heart functions as a muscular pump regulated by an intrinsic electrical system. This system begins with the sinoatrial (SA) node, the heart’s natural pacemaker, located in the upper right atrium. The SA node generates an electrical impulse that spreads across both upper chambers, causing them to contract and push blood into the ventricles.
The signal then pauses briefly at the atrioventricular (AV) node, ensuring the ventricles have time to fill completely before contraction. The impulse continues down the Bundle of His, which divides into the left and right bundle branches. These branches rapidly distribute the signal to the muscle tissue of the left and right ventricles.
Normally, the signal travels down both branches simultaneously, causing the ventricles to contract in near-perfect synchrony. When a delay occurs in the right bundle branch, the electrical signal is blocked or slowed, forcing the impulse to take a detour. This detour means the right ventricle is activated slowly by the signal spreading from the left ventricle, causing the right side’s contraction to be delayed.
What Causes the Delay in the Right Ventricle?
The causes of a right ventricular conduction delay range from benign findings in healthy individuals to signs of serious underlying heart or lung disease. Many cases are considered idiopathic, meaning no clear underlying disease is found. This finding is often considered a normal variation, especially as people age, with up to 11% of the population having this by age 80.
Acquired causes develop later in life, often due to conditions that strain the right side of the heart. An acute cause is a pulmonary embolism, a blood clot in the lung that suddenly increases pressure on the right ventricle. Chronic conditions causing long-term strain, such as pulmonary hypertension or severe chronic obstructive pulmonary disease (COPD), can also lead to a delay by causing the right ventricle to enlarge.
Structural heart diseases, both acquired and congenital, also contribute to this delay. Examples include right ventricular hypertrophy (thickening of the right ventricular muscle) or congenital conditions like an atrial septal defect (ASD). Rarely, the delay is linked to inherited rhythm disorders such as Brugada syndrome. Furthermore, certain cardiac procedures, like right heart catheterization, can temporarily or permanently cause a conduction delay.
Detecting Right Ventricular Conduction Delay
The primary method for detecting a right ventricular conduction delay is an electrocardiogram (ECG or EKG). This simple, non-invasive test records the electrical activity of the heart and pinpoints the timing issue. The delay is visible on the ECG because the electrical impulse takes longer to complete the circuit, resulting in a wider QRS complex.
A widened QRS complex is the hallmark of this condition, often defined as a duration of 120 milliseconds or more for a complete block. The characteristic pattern seen on the ECG is sometimes described as a distinctive “rabbit ears” or “M-shaped” pattern in the chest leads. This specific shape represents the initial, normal activation of the left ventricle followed by the delayed, slow activation of the right ventricle.
Since the delay is often found incidentally during routine screening, secondary diagnostic tools are frequently used to check for an underlying cause. An echocardiogram uses sound waves to create moving images of the heart and is often performed to look for structural issues like right ventricular enlargement. Other tests, such as stress tests or blood tests, may also be used to evaluate the patient’s overall heart health and rule out conditions like coronary artery disease.
Prognosis and Treatment Options
For many people, an isolated right ventricular conduction delay is considered a benign finding, especially if they have no symptoms or underlying heart disease. In these cases, the outlook is favorable, and no specific treatment is required for the electrical delay itself. Doctors typically recommend annual clinical evaluation with an ECG to monitor the condition.
When the delay is a symptom of a larger problem, the focus shifts to treating the underlying disease. For example, if the delay is caused by a pulmonary embolism, the patient receives medications to dissolve the clot. If the delay is accompanied by heart failure, treatment involves optimizing medical therapies for heart failure.
A permanent pacemaker is rarely needed for an isolated right ventricular conduction delay. Pacing may be considered if the delay progresses to combine with other electrical blocks, or if the patient experiences syncope (fainting) suggesting a higher risk of complete heart block. In specific cases of heart failure with reduced pumping ability, cardiac resynchronization therapy might be considered, though its benefit is limited compared to delays on the left side.