Cardiology · Inflammatory Heart Disease
The facts most likely to be tested
Coxsackievirus B is the most common viral etiology of myocarditis in developed countries.
Patients typically present with a viral prodrome followed by symptoms of acute heart failure or chest pain mimicking myocardial infarction.
Endomyocardial biopsy remains the gold standard for definitive diagnosis, though it is reserved for cases with unexplained progressive heart failure.
Cardiac MRI is the preferred non-invasive diagnostic modality, demonstrating late gadolinium enhancement in a non-coronary distribution.
Physical examination often reveals a new S3 gallop or a holosystolic murmur secondary to functional mitral regurgitation.
Electrocardiogram findings are non-specific but frequently show diffuse ST-segment elevations or T-wave inversions.
Management is primarily supportive care with beta-blockers and ACE inhibitors for heart failure, while avoiding NSAIDs due to potential for worsening myocardial inflammation.
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A 24-year-old male presents to the emergency department with three days of fatigue, dyspnea, and substernal chest pain. He reports a recent episode of fever and myalgias two weeks ago. Physical examination reveals a new S3 gallop and bilateral crackles on lung auscultation. An ECG shows diffuse ST-segment elevations without reciprocal changes. Cardiac biomarkers are elevated, and a cardiac MRI reveals late gadolinium enhancement in the mid-myocardial and epicardial layers.
What is the most likely diagnosis?
Myocarditis
The patient's presentation of a viral prodrome followed by signs of heart failure, combined with the classic cardiac MRI finding of non-coronary distribution late gadolinium enhancement, is pathognomonic for myocarditis.
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Etiology / Epidemiology
Most commonly viral (Coxsackie B). Affects young, healthy adults following a recent URI.
Clinical Manifestations
Presents as heart failure or unexplained arrhythmias. Look for S3 gallop.
Diagnosis
Endomyocardial biopsy is the gold standard. Cardiac MRI is the preferred non-invasive test.
Treatment
Supportive care (ACEi/Beta-blockers). Avoid NSAIDs as they worsen myocardial inflammation.
Prognosis
Variable; ranges from full recovery to dilated cardiomyopathy and sudden cardiac death.
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Epidemiology & Etiology
Most cases are idiopathic or secondary to viral infections, specifically Coxsackie B, Adenovirus, or Parvovirus B19. Non-viral causes include Lyme disease, Chagas disease, and hypersensitivity reactions to drugs like clozapine.
Pertinent Anatomy
Inflammation involves the myocardium, leading to focal or diffuse myocyte necrosis. This structural damage impairs systolic function and disrupts the electrical conduction system.
Pathophysiology
Direct viral invasion or immune-mediated injury triggers a cytokine storm and lymphocytic infiltration. This leads to myocyte necrosis, interstitial edema, and subsequent ventricular remodeling. The resulting ventricular dilation reduces stroke volume and cardiac output.
Clinical Manifestations
Patients often present with viral prodrome (fever, myalgias) followed by signs of acute heart failure (dyspnea, orthopnea). Physical exam may reveal a S3 gallop, tachycardia, or a new murmur. Red flags include syncope, sustained ventricular arrhythmias, or cardiogenic shock.
Diagnosis
Endomyocardial biopsy remains the gold standard for definitive diagnosis. Cardiac MRI is the preferred non-invasive modality, showing late gadolinium enhancement in a non-coronary distribution. ECG often shows diffuse ST-segment elevations or T-wave inversions.
Treatment
Management is primarily supportive care with standard heart failure therapy including ACE inhibitors and beta-blockers. Avoid NSAIDs as they increase mortality and exacerbate inflammation. In cases of fulminant disease, mechanical circulatory support (e.g., ECMO) may be required.
Prognosis
Most patients recover with supportive therapy. However, a subset progresses to dilated cardiomyopathy or chronic heart failure. Long-term monitoring for arrhythmias is essential.
Differential Diagnosis
Acute Myocardial Infarction: typically presents with localized ST-elevation and regional wall motion abnormalities
Pericarditis: characterized by pleuritic chest pain relieved by leaning forward
Takotsubo Cardiomyopathy: triggered by intense emotional stress with apical ballooning
Acute Rheumatic Fever: associated with recent Group A Strep infection and Jones criteria
Dilated Cardiomyopathy: chronic presentation with global ventricular enlargement