What murmur would you expect to hear in a patient with rheumatic fever and new onset atrial fibrillation?

In the context of rheumatic fever, the murmur most commonly associated with mitral stenosis would be expected. Rheumatic fever frequently results in valvular heart disease, particularly affecting the mitral valve, and can lead to stenosis over time. Mitral stenosis creates a characteristic diastolic murmur, which is best heard at the apex of the heart and may be accentuated by the presence of atrial fibrillation.

Atrial fibrillation often occurs in patients with mitral stenosis due to the increased pressure in the left atrium and the underlying atrial dilation that can occur as a result of this condition. The irregular rhythm of atrial fibrillation can cause alterations in the heart’s hemodynamics, increasing the likelihood of turbulence in the blood flow across a narrowed mitral valve, which is why the murmur would be prominent in this scenario.

Therefore, the combination of rheumatic heart disease leading to mitral stenosis along with the new onset of atrial fibrillation makes the diastolic murmur of mitral stenosis the most expected finding on examination.