We report a case of acute rheumatic fever in a 46-year-old man in whom cardiovascular magnetic resonance imaging (CMRI) played a critical role. Rheumatic carditis may be subclinical and difficult to diagnose by conventional methods. This case illustrates the use of contrast CMRI in the detection of carditis, one of the major Jones criteria1 in the diagnosis of acute rheumatic fever.
A 46-year-old previously healthy fireman consulted his primary physician for acute onset of fever, sore throat, and night sweats. He received amoxicillin for a positive rapid streptococcal test. He lived with his 3 children aged 5, 7, and 9 years, who have been diagnosed with streptococcal throat infections in the past but not recently. Six days after the onset of his original symptoms, he presented to an outside hospital complaining of 2 hours of left retrosternal nonpositional chest pain. Electrocardiogram showed left ventricular hypertrophy but no ischemic changes; however, cardiac isoenzymes were elevated with peak troponin I of 10.9 ng/mL. He received aspirin and sublingual nitroglycerin without significant relief. He was then transferred to our institution for a cardiac catheterization.
During further questioning, the patient reported associated symptoms including shoulder, hand, and knee arthralgias. The arthralgias were severe enough that he could not enjoy his hobby as a bagpipe player. On examination, he was hemodynamically stable, with a temperature of 36.8°C. He had an erythematous nonexudative pharynx, joints without objective evidence of arthritis, and no rashes. Cardiovascular examination revealed a nondisplaced point of maximal impulse and normal S1 and S2 without murmurs or rubs.
Cardiac catheterization demonstrated angiographically normal coronary arteries and mild anterolateral hypokinesis. Transthoracic echocardiogram was only significant for borderline reduced left ventricular function. The patient's chest pain resolved, and an acute coronary syndrome had been ruled out; however, the anterolateral hypokinesis warranted further investigation. Hence, a contrast CMRI (Fig. 1) was obtained which revealed lateral wall hyperenhancement consistent with myocarditis as well as a low normal left ventricular ejection fraction of 55%. Erythrocyte sedimentation rate was elevated at 42 mm/h, and antistreptolysin O was elevated at 378 IU/mL. Acute rheumatic fever was diagnosed by 1 major Jones criterion1 (carditis) and 3 minor criteria (fever, arthralgias, and elevated erythrocyte and sedimentation rate), plus supporting evidence of antecedent group A streptococcal infection including elevated antistreptolysin O and positive rapid streptococcal test. He was treated with high-dose aspirin and penicillin V. Prophylaxis was initiated as an outpatient with penicillin V 500 mg once daily. After 1 month, the patient had a second contrast CMRI that revealed decreased myocardial inflammation. After 2 months, the patient was evaluated with electrocardiogram and transthoracic echocardiogram; both of which were normal. The patient experienced no further chest pain. He returned to active duty as a fireman.
Acute rheumatic fever, a nonsuppurative syndrome after group A streptococcal upper respiratory tract infection, requires a specific combination of signs and symptoms for diagnosis as defined by the Jones criteria. To facilitate the diagnosis of acute rheumatic fever, Jones2 first published his criteria, divided into major and minor categories, in JAMA in 1944. The American Heart Association updates these criteria, most recently in 1992, with the additional requirement of evidence of antecedent group A streptococcal infection.1 Acute rheumatic fever demands strict diagnostic criteria because of its infrequency in developed countries and the consequence of long-term prophylaxis that the diagnosis carries. The major criteria of polyarthritis, chorea, subcutaneous nodules, and erythema marginatum may be more clinically apparent, but carditis can be diagnostically elusive. Carditis occurs in 30% of adult cases3 and may manifest as a new regurgitant heart murmur, cardiac enlargement, congestive heart failure, pericardial friction rub, and pericardial effusion, or infrequently may mimic unstable angina.4 However, carditis may be asymptomatic, yet of all the major criteria, carries the greatest potential for morbidity and mortality.
Conventional diagnostic techniques such as electrocardiography, echocardiography, and cardiac isoenzymes may suggest carditis; however, carditis requires more precise definition. Scintigraphy is limited by decreased specificity,5 and the "gold standard" endomyocardial biopsy is an invasive procedure prone to sampling error in focal disease. Recognizing the limitations of conventional diagnostic tools, Friedrich et al6 used contrast CMRI to visualize the location and extent of inflammation induced by acute myocarditis. Furthermore, Mahrholdt et al7 described a newer contrast CMRI technique known as inversion recovery gradient echo, which increases the distinction between diseased and normal myocardium by up to 500% as compared with the technique used by Friedrich et al.6 Using this technique, Mahrholdt et al imaged 32 patients diagnosed clinically with myocarditis and found contrast enhancement in 28 patients (88%), most commonly located in the lateral free wall. Moreover, they found that the contrast enhancement was associated with active myocarditis as confirmed histopathologically by "CMRI-guided" endomyocardial biopsy in the areas of the contrast enhancement.
CMRI contrast agents are limited to the extracellular space. Disruption of membrane integrity with subsequent diffusion of contrast into the myocyte intracellular space is the hypothesized cellular-level mechanism of contrast enhancement. Intact sarcolemmal membranes prevent diffusion of contrast into the myocyte intracellular space; therefore, normal myocardium does not enhance.8 Both myocardial infarction and inflammatory heart disease cause membrane rupture, yet the patterns of contrast enhancement differ. Myocardial infarction contrast enhancement follows the distribution of a coronary artery and is subendocardial, whereas myocarditis contrast enhancement is patchy, irregular, and subepicardial. In addition, myocarditis contrast enhancement tends to be smaller and less bright than infarct contrast enhancement because the inflammation of myocarditis will usually contain more living myocytes between the islands of necrosis.7
The appearance of the gadolinium enhancement is not likely the result of imaging errors or false-positive hyperenhancement. Incorrect inversion times lead to either mild midwall enhancement or uniform gray-appearing myocardium, not the findings seen in this patient. The possibility of a concomitant viral myocarditis would be the most likely alternative explanation for the CMRI findings seen. Although it is true that traditionally diagnosed carditis is almost always associated with valvular abnormalities, the ability of CMRI to detect subclinical disease may eventually show that mild carditis, especially when not associated with valvular disease, is more common than previously thought. However, it may be that only carditis associated with valvular abnormalities carries the risk of future cardiac progression. Only future studies that examine the presence and significance of hyperenhancement in patients with acute rheumatic fever will be able to tell if subclinical carditis is a common or uncommon feature of the disease.
Contrast CMRI should be considered in cases of suspected carditis. This case demonstrates the use of contrast CMRI to diagnose carditis, a crucial major Jones criteria in the diagnosis of acute rheumatic fever.
1. Special Writing Group of the Committee of Rheumatic Fever, Endocarditis, and Kawasaki Disease of the Council on Cardiovascular Disease in the Young of the American Heart Association. Guidelines for the diagnosis of rheumatic fever: Jones criteria, 1992 update. JAMA
2. Jones TD. Diagnosis of rheumatic fever. JAMA
3. Wallace MR, Garst PD, Papadimos TJ, et al. The return of acute rheumatic fever in young adults. JAMA
4. Litvinova L, Nord J. Acute rheumatic fever presenting as unstable angina. South Med J
5. Yasuda T, Palacios IF, Dec GW, et al. Indium 111-monoclonal antimyosin antibody imaging in the diagnosis of acute myocarditis. Circulation
6. Friedrich MG, Strohm O, Schulz-Menger J, et al. Contrast media-enhanced magnetic resonance imaging visualizes myocardial changes in the course of viral myocarditis. Circulation
7. Mahrholdt H, Goedecke C, Wagner A, et al. Cardiovascular magnetic resonance assessment of human myocarditis a comparison to histology and molecular pathology. Circulation
8. Mahrholdt H, Wagner A, Judd RM, et al. Assessment of myocardial viability by cardiovascular magnetic resonance imaging. Eur Heart J