An Old Disease Revisited Significance of Elevated Troponins in a case of Acute Rheumatic Fever

Introduction

Worldwide, there are 470,000 new cases of rheumatic fever and 233,000 deaths attributable to rheumatic fever or rheumatic heart disease each year; most occur in developing countries. Among indigenous groups and developing nations, over 15 million people are estimated to have rheumatic heart disease. ^{1 2}   In the United States and other developed countries, the incidence of ARF is much lower: 2-14 cases per 100,000. This is probably due to improved hygienic standards and routine use of antibiotics for acute pharyngitis. ^{3 4}  Troponins are clinical markers for myocardial damage that became available for clinical use in 1995.

Case Report

An 18 year old Hispanic male, with no significant past medical history, presented to the emergency room with three days of throat pain and difficulty swallowing. He also reported generalized body aches, pleuritic chest pain associated with tingling in the arms. He was seen one day earlier in the emergency room with similar complaints and fever of 101.4o F. His throat culture was done and he was discharged home with analgesics and antibiotics. Since he did not feel better, he returned to the hospital.

Physical exam was significant for erythema and exudates of the posterior pharyngeal wall. Electrocardiogram showed normal sinus rhythm at 65 beats per minute with left anterior fascicular block, which remained unchanged during the hospital course. Chest X- ray was normal. Echocardiogram was normal. Laboratory results revealed elevated troponin (2.4 ng/ml, normal 0-0.5 ng/ml) see below, antistreptolysin – O titer of >800 IU/ml (normal < 200 IU/ml), elevated erythrocyte sedimentation rate and high C-reactive protein. Throat culture grew many B-hemolytic streptococcus group A.

The patient was monitored in the ICU and started on penicillin for treatment of acute rheumatic fever, as he had evidence of carditis with elevated acute phase reactants in the setting of a pharyngeal group A streptococcal infection. Further laboratory tests included negative HIV test, mycoplasma antibody, lyme serology, toxoplasma antibody, Epstein – Barr virus antibody, and adenovirus antibody.
On day 4, the patient was discharged home on penicillin for at total of 10 days.  The patient was scheduled for a stress test but was lost to follow up.

Discussion

Three recent studies examined the levels of troponins in ARF. One study ⁵  examined stored sera from 22 patients with ARF diagnosed in 1944, a second ⁶  had 95 consecutive patients with ARF, and a third ⁷  examined 46 patients with valvular disease secondary to ARF. All these studies found no significant increases in troponin levels.

In view of these findings, as well as the lack of inflammation seen on cardiac biopsies, the mechanism of ARF has been redefined. Previously it was thought that there was an acute pancarditis that lead to valvular dysfunction. Now, the pathology is felt not to involve the myocytes but the endocardial surface that leads to valvular dysfunction.

However, in our case, the patient presents with chest pain and an abnormal EKG. Another case report ⁸  also describes a patient with ARF who presents with chest pain and an EKG with diffuse ST elevations. In both these cases the troponin levels were elevated and the echocardiogram showed no valvular disease.

This suggests that these two cases may represent a subgroup of patients with ARF that do have some cardiac myocyte damage and no valvular involvement. In these cases one can evoke the theory of molecular mimicry or epitope similarity between group A streptococcal M proteins and myosin. ⁹  The long term prognosis in these types of patients is unknown.

The pathogenesis of ARF is now felt to involve the myocardial surface causing valvular dysfunction, with normal troponin levels. Our case may represent a sub-group of patients that do not have valvular involvement but do have a myocarditis manifested by chest pain, abnormal EKG and elevated troponin levels.