Are there cases of Legionella (Legionnaires' disease) causing myocarditis (inflammation of the heart muscle)?

From the Guidelines

Legionella infection can indeed cause myocarditis, though it is a relatively uncommon complication, as noted in the guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. Cases of Legionella-associated myocarditis have been documented in medical literature, typically occurring as part of a more severe presentation of Legionnaires' disease. The mechanism involves direct bacterial invasion of cardiac tissue and inflammatory responses triggered by the infection. Patients with Legionella myocarditis typically present with fever, respiratory symptoms, and cardiac manifestations such as chest pain, arrhythmias, or heart failure. Some key points to consider in the diagnosis and management of myocarditis include:

• The diagnosis requires a high index of suspicion and is confirmed through a combination of cardiac biomarkers (troponin, BNP), ECG changes, cardiac imaging (echocardiography, cardiac MRI), and confirmation of Legionella infection through urinary antigen testing or respiratory cultures.
• Treatment involves appropriate antibiotics for Legionella, typically azithromycin (500mg daily for 7-10 days) or levofloxacin (750mg daily for 7-14 days), along with supportive cardiac care, as suggested by the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1.
• The prognosis varies based on the severity of cardiac involvement and the patient's underlying health status, with complete recovery possible with prompt diagnosis and appropriate treatment. It's also important to note that myocarditis can occur due to a wide range of infectious agents, including viruses, bacteria, chlamydia, rickettsia, fungi, and protozoans, as well as toxic and hypersensitivity reactions, as mentioned in the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. Endomyocardial biopsy remains the gold standard for the definite diagnosis of myocarditis and should be performed especially in patients with a life-threatening course of the disease, as stated in the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. Cardiac magnetic resonance (CMR) is becoming routine and is a sensitive, non-invasive test for confirmation of acute myocarditis even before endomyocardial biopsy, as noted in the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. Essential first-line tests to confirm the diagnosis in patients with a clinical presentation consistent with myocarditis should include 12-lead ECG, transthoracic echocardiogram, and assessment of biomarker concentrations (including troponins), erythrocyte sedimentation rate, and C-reactive protein, as suggested by the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. The diagnosis of myocarditis should be based on the criteria summarized by Caforio et al., as mentioned in the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. In the acute stage of disease, myocarditis may be asymptomatic or present with an unrecognized non-specific course, as noted in the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. Considering malignant arrhythmias associated with myocarditis, two distinct clinical settings have to be distinguished: acute fulminant myocarditis with refractory malignant ventricular tachyarrhythmias in the context of severe acute heart failure, and adverse short-term prognosis with early death due to multisystem failure, and long-term evolution to inflammatory cardiomyopathy with left ventricular dysfunction and resulting in a high risk of sudden cardiac death similar to that for dilated cardiomyopathy, as stated in the guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1.

From the Research

Cases of Legionella Causing Myocarditis

• There have been reported cases of Legionella infection causing myocarditis, a rare extrapulmonary manifestation of legionellosis 2, 3, 4, 5.
• Myocardial involvement is the most common extrapulmonary manifestation of legionellosis and can result in left ventricular dysfunction 2.
• Legionella-induced myocarditis can occur with or without pneumonia, and cases have been reported in both immunocompetent and immunocompromised hosts 3, 4, 5.
• The clinical manifestations of Legionella-induced myocarditis can be dramatic, and early recognition is crucial for timely initiation of appropriate antibiotics 2, 3.
• Layer-specific two-dimensional longitudinal speckle-tracking analysis can be useful in diagnosing and monitoring Legionella-induced myocarditis 3.
• Treatment of Legionella-induced myocarditis typically involves antibiotics, such as levofloxacin, and supportive care 6.