Which murmur is associated with a thrill that can be palpated?

A Grade 4 murmur is indeed associated with a thrill that can be palpated. The grading scale for heart murmurs ranges from 1 to 6, with higher grades indicating louder sounds and additional characteristics. A Grade 4 murmur is defined as being loud and, importantly, accompanied by a palpable thrill. This means that not only is the sound generated by turbulent blood flow significant, but it is also strong enough that the vibration caused by the turbulent flow can be felt upon examination.

In comparison, a Grade 3 murmur is audible but typically lacks the intensity needed to produce a palpable thrill, whereas Grade 5 murmurs are characterized by a very loud sound that can be heard with a stethoscope partially off the chest but still may not guarantee the presence of a thrill. Grade 6 murmurs are even louder and can be heard without a stethoscope, but, like Grade 5, the association with a thrill is not explicitly defined in the grading itself, thus reinforcing the unique characteristic of a Grade 4 murmur.