In patients with myxoma, what heart sound may be absent due to obstruction?

In patients with myxoma, the presence of a cardiac tumor can lead to obstruction of blood flow, particularly during diastole when the mitral valve is normally open. Myxomas are often found in the left atrium and can obstruct the mitral valve orifice, affecting the heart sounds associated with ventricular filling.

The gallop rhythm, characterized by additional heart sounds, typically occurs due to volume overload or changes in ventricular compliance. In the case of myxoma, the obstruction can hinder normal filling dynamics and prevent the formation of the third heart sound (S3) or a fourth heart sound (S4), which are part of a gallop rhythm. Therefore, the gallop rhythm may be absent in these patients due to the interference with normal atrial and ventricular filling caused by the tumor.

On the other hand, the first heart sound represents the closure of the mitral and tricuspid valves, while the second heart sound is associated with the closure of the aortic and pulmonic valves. A split S2 can occur but does not directly result from myxoma obstruction in the same manner as the gallop rhythm. Thus, understanding these relationships helps clarify why the absence of a gallop rhythm is the correct answer in the