The myocardium is the layer of muscle that forms the walls of the heart, contracting and relaxing to pump blood. The heart contains four chambers, and the right ventricle is the lower right chamber. It is the most forward-facing chamber of the heart, positioned directly behind the sternum.
Anatomical Characteristics of the Right Ventricular Myocardium
The right ventricular myocardium has a structure adapted to its workload. Its wall is thinner than that of the left ventricle, measuring 3 to 5 millimeters in adults. This difference contributes to its crescent-like shape in cross-section, as it wraps around the larger, conical left ventricle.
Internally, the surface of the right ventricular myocardium is characterized by muscular ridges known as trabeculae carneae. Among these is the moderator band, a muscular band found only in the right ventricle. This band stretches from the interventricular septum—the wall separating the ventricles—to the base of the anterior papillary muscle and plays a role in the heart’s electrical conduction system.
The blood supply to the right ventricular muscle is delivered by the right coronary artery. This artery and its marginal branches perfuse the majority of the right ventricular free wall. The anterior portion also receives blood from branches of the left anterior descending artery, demonstrating a shared blood supply.
The Role in Pulmonary Circulation
The primary function of the right ventricular myocardium is to propel deoxygenated blood into the pulmonary circulation. When the myocardium contracts, it sends this blood through the pulmonary valve and into the pulmonary artery, which carries it to the lungs for oxygenation.
This process occurs under lower pressure compared to the circulation for the rest of the body. The pulmonary system is a low-resistance pathway, so the right ventricle does not need to generate as much force to move blood through it. This low-pressure requirement is the direct reason for the right ventricular myocardium’s thinner and less muscular build compared to the left ventricle.
In contrast, the left ventricle’s myocardium is much thicker because it must pump oxygenated blood into the high-pressure systemic circulation, which supplies the entire body. This task requires a more robust muscular wall to overcome the greater resistance.
Conditions Affecting the Right Ventricle’s Muscle
Several medical conditions can impact the structure and function of the right ventricular myocardium. One is right ventricular hypertrophy, which involves a thickening of the muscular wall. This is a response to an increased workload, caused by high blood pressure in the lungs (pulmonary hypertension). As the right ventricle works harder to pump blood against elevated pressure, its muscle tissue enlarges.
Another condition is arrhythmogenic right ventricular cardiomyopathy (ARVC). This is a genetic disorder where the muscle tissue of the right ventricle is progressively replaced by fatty and fibrous scar tissue. This change weakens the ventricle’s wall and disrupts the heart’s electrical signaling, increasing the risk of arrhythmias, or irregular heartbeats.
Both scenarios can compromise the right ventricle’s ability to efficiently pump blood to the lungs, which may lead to broader cardiovascular complications.