显微镜下可清楚地见到特殊的炎性肉芽肿形态(被称为Aschoff小体)，急性风湿性心脏炎的特征。肉芽肿多发生在血管周围的间质中。严重的心肌炎可能导致充血性心力衰竭。
Microscopically, acute rheumatic carditis is marked by a peculiar form of granulomatous inflammation with so-called "Aschoff nodules" seen best in myocardium. These are centered in interstitium around vessels as shown here. The myocarditis may be severe enough to cause congestive heart failure.