“PSM” is not a commonly used medical abbreviation for a heart murmur. However, based on your description, it appears you are referring to “Pansystolic Murmur” (PSM) or “Holosystolic Murmur.”
In a pansystolic or holosystolic murmur, the murmur is heard throughout the entire systolic phase of the cardiac cycle. This means the abnormal sound starts at the beginning of systole (after the first heart sound, S1) and continues until the end of systole (before the second heart sound, S2).
The characteristics you mentioned, where S1 is indistinct or soft, indicate that the murmur is louder or more prominent than the normal heart sounds, making it difficult to distinguish the first heart sound clearly.
Pansystolic or holosystolic murmurs are typically associated with regurgitant heart valve conditions. The most common examples are mitral regurgitation and tricuspid regurgitation. In these conditions, there is an abnormal backflow of blood through the respective valves during systole, resulting in the continuous murmur throughout the systolic phase.
It’s important to note that an accurate diagnosis requires a thorough evaluation by a healthcare professional, including a detailed medical history, physical examination, and possibly additional tests such as echocardiography, to determine the exact cause and severity of the murmur and guide appropriate treatment.