AR does not occur in the absence of MR. MR is due to a combination of valvulitis, chorditis and annulitis.

The LV systolic function is normal in ARF unlike in viral myocarditis. The LVEF and shortening fraction are normal. HF and LV dilatation tend to normalize within a short period following valve surgery. Chordal inflammation can lead to lengthening and sometimes rupture leading to prolapse of the anterior mitral leaflet. Chordal rupture can produce flail anterior mitral leaflet and acute severe MR.

High sensitivity cardiac troponins, which are highly sensitive markers of myocardial necrosis, are not significantly elevated in rheumatic carditis. Limited cardiac MR studies during the acute phase have also failed to demonstrate significant myocarditis. Studies from South Africa have demonstrated that valve reconstruction and replacement are effective and safe life-saving options in sick children with severe HF following ARF. Clinically significant myocarditis does not occur in acute ARF.