What grade of murmur is first associated with a palpable thrill?

A Grade 4 murmur is the first level at which a palpable thrill is typically detected. Murmurs are classified on a scale from 1 to 6 based on their intensity, with Grade 1 being barely audible and Grade 6 being audible without a stethoscope. A palpable thrill signifies the presence of significant turbulence in the blood flow, often due to underlying heart pathology that produces a louder and more pronounced murmur.

At Grade 4, the murmur is considered loud enough not only to be heard with a stethoscope placed lightly on the skin but also strong enough to create vibrations that can be felt by hand. In terms of clinical significance, the presence of a palpable thrill usually suggests a higher degree of hemodynamic disturbance, which could indicate conditions such as severe regurgitation or stenosis. Grades 2 and 3 murmurs are typically softer and may not generate enough turbulence to create a palpable sensation. Grade 5 murmurs are very loud and can also be associated with thrills, but it is Grade 4 where this phenomenon first occurs.