Acute Streptococcal Myocarditis Presenting as Acute ST-Elevation Myocardial Infarction

ABSTRACT: Acute streptococcal myocarditis is an uncommon diagnosis in the developed world. Its presentation masquerading as acute myocardial infarction is still uncommon. We describe a case of a young male presenting with a recent diagnosis of streptococcal pharyngitis followed by a classical presentation of post streptococcal myocarditis. This is an unusual presentation of acute rheumatic fever (ARF) masquerading as acute myocardial infarction, with a discussion on its diagnosis and management. J INVASIVE CARDIOL 2010;22:E189–E191 Key words: acute infarction streptococcal myocarditis; acute rheumatic fever ————————————————————————————— Acute post streptococcal myocarditis is a well-defined and well-recognized phenomenon. This condition, however, appears to be diagnosed more commonly in the developing world than in the United States. This may partly be due to the geographic prevalence of streptococcal infection and its resultant complications, but lack of awareness of the presenting features of post streptococcal carditis may be, in part, responsible for the under diagnosis of this complex in first world countries. Acute post streptococcal focal myocarditis is a further uncommon presentation, which has been described and can mimic acute ST-elevation myocardial infarction. Early recognition of this uncommon entity in its association with the prior history would be ideal to reduce the rates of unnecessary diagnostic cardiac catheterizations in this population. Case Report. A 36-year old male presented to the emergency room with chest discomfort. One week prior, he had been prescribed amoxicillin for a diagnosis of streptococcal throat infection diagnosed by an in-office rapid screening test which is specific for Group A Streptococcal (GAS) infections. The emergency room presentation was for chest discomfort that was described as ill-defined precordial pressure with a pleuritic component starting 6 hours prior to presentation. This was accompanied with arthralgia of his left hand as well as small joint swelling resulting in the inability to remove his wedding band. He was noted to be afebrile at the time of evaluation but did give a history of being febrile 1 day prior to presentation. An ECG revealed focal ST-elevation localized to the lateral leads with reciprocal changes in the inferior leads (Figure 1). Cardiac catheterization was performed, revealing angiographically normal epicardial coronary arteries. The ejection fraction was estimated to be mildly reduced at 45% with a focal wall motion abnormality isolated to the lateral wall of the left ventricle. Due to a history of shellfish allergy, catheterization was preceded with use of intravenous steroids (Hydrocortisone hemisuccinate) as per institutional protocol. Echocardiography performed during this admission did not reveal any valvular pathology. Laboratory data showed CPK elevation (peak 720 U/L; Normal 39–308 U/L) with associated CK-MB elevation (Peak 82.83 ng/ml; Normal Discussion. Diagnosis of acute post streptococcal myocarditis (APSM) or Acute Rheumatic Fever (ARF) may be made on clinical grounds.^1,2 Pathologically, this is characterized by an abnormal autoimmune reaction to a pharyngeal group A streptococcal infection with a resulting systemic inflammatory response. Any part of the body can be affected, and although it can occur at any age, it typically presents in childhood, just before adolescence, with a female predominance. The incidence in the United States is low due to improved hygiene as well as early availability of antibiotics. There is no single, gold standard diagnostic evaluation for APSM. The diagnosis of the initial acute attack is therefore clinically based using the revised Jones criteria (Table 1). The present gold standard for diagnosis of myocarditis has traditionally been endomyocardial biopsy, evaluated according to the ‘Dallas criteria.’^3–5 During the acute phase, interstitial edema, lymphocyte infiltration of the myocardium and myocyte necrosis is shown, but isolation of infectious etiology is rare.⁶ Endomyocardial biopsy has low sensitivity due to the focal and heterogeneous involvement of the myocardial disease and can be associated with major complications, particularly in the pediatric age group. Sensitivity has been estimated at between 50 to 63%,⁷ although this may be increased by biventricular samples and analysis of 6 or more samples per patient. Contrast media-enhanced MRI, however, can be used for the visualization of myocarditis, i.e., the localization, activity and extent of the inflammation. The inflammatory process evolves from a focal to a disseminated process during the first two weeks of inflammation, which was first described by Friedrich.⁷ This was followed by an evaluation of use of Gd-enhanced T1 weighted MRI imaging in early as well as late myocarditis.⁹ The contrast agent used, gadolinium, accumulates in inflammatory lesions; it penetrates into extracellular fluid space but not into living cells. The accumulations provide an estimate of the sum of increased blood flow, acute cell damage and extravasation of fluid in areas of inflammation. The evolution of the inflammatory process is characteristic of myocarditis, but not of myocardial infarction. MRI, therefore, appears to be evolving as an excellent non-invasive diagnostic tool in diagnosing myocarditis. Our patient had classic features of acute focal myocarditis clinically which was subsequently confirmed with MRI imaging. The extent of myocardial inflammation can be significantly underestimated clinically, however, MRI imaging revealed significant inflammatory changes in the septum as well as in the lateral wall which is typical of the more generalized carditis resulting from an immune mediated pathophysiology. Optimal treatment of ARF remains unclear, largely because of a lack of randomized controlled trials. Due to the presumed inflammatory nature of the condition, anti-inflammatory agents including corticosteroids are frequently used, although a recent Cochrane review showed no benefit in reducing cardiac complications at 1 year in patients treated with corticosteroids or immunoglobulins compared with placebo.⁸ Salicylates lead to resolution of fever, arthritis, and arthralgia although their use in acute carditis is not recommended, and the search continues for an effective treatment of ARF. To prevent recurrences of ARF and carditis, long-term antibiotic prophylaxis is recommended, with a view to reduce the risk of recurrence. Since our patient was asymptomatic, he was discharged home on ACE inhibition and beta-blockers due to the presence of a cardiomyopathy. He has done well clinically and remains asymptomatic 6 months after his acute illness. Conclusion. Acute streptococcal myocarditis is an uncommon condition in the developed world and a high clinical suspicion is necessary for its appropriate diagnosis. Atypical presentations should be considered in view of the varied presentations. Contrast-enhanced MRI imaging appears to be a suitable non invasive diagnostic modality. Given the long-term adverse sequelae of this disease process, accurate and appropriate diagnosis is essential to continue active long term prophylactic antibiotic therapy.

References

1. Jones TD, Diagnosis of rheumatic fever. JAMA 1944;126: 481–484. 2. Special Writing Group of the Committee on 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 1992;268:2069–2073 3. Mason JW, O’Connel JB. Clinical merit of endomyocardial biopsy. Circulation 1989; 79:971–979. 4. Aretz HT. Myocarditis: The Dallas criteria. Hum Pathol 1987;18:617–624. 5. Lieberman EB, Hutchins GM, Herskowitz A, et al. Clinicopathologic description of myocarditis. J Am Coll Cardiol 1991;18:1617–1626. 6. Billingham M. Acute myocarditis: A diagnostic dilemma. Br Heart J 1987;58:6–8. 7. 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 1998;978:1802–1809. 8. Cilliers AM, Manyemba J, Saloojee H. Anti inflammatory treatment for carditis in acute rheumatic fever. Cochrane Database Syst Rev 2003;(2):CD003176. 9. Laissy JP, Messin B, Varenne O, et al. MRI of acute myocarditis. Chest 2002;122:1638–1648.

—————————————————————————— From Scranton Temple Residence Program, and ^*Great Valley Cardiology, Scranton, Pennsylvania. The authors report no conflicts of interest regarding the content herein. Manuscript submitted January 7, 2010, provisional acceptance given February 8, 2010, final version accepted March 2, 2010. Address for correspondence: Sridhar Sampath Kumar, MD, Great Valley Cardiology, 746 Jefferson Avenue Suite 305, Scranton PA 18510. E-mail: sridharsk@gmail.com