Title : Legionella pneumonia complicated by fulminant myocarditis
Abstract:
Background: Legionella pneumophila is a well-recognized cause of severe community-acquired pneumonia, particularly in patients presenting with hyponatremia and systemic inflammatory features. While pulmonary manifestations predominate, extrapulmonary involvement may occur. Cardiac complications, including myocarditis, are rare but potentially catastrophic and frequently underrecognized during the early management of Legionnaires’ disease. Fulminant myocarditis associated with Legionella infection carries a high risk of malignant arrhythmias, cardiogenic shock, and death.
Case Summary: A previously healthy 52-year-old man presented with one week of fever, diarrhea, progressive dyspnea, and lethargy. On admission, he was febrile (38.5°C) and hypoxic, requiring escalation to mechanical ventilation for acute hypoxemic respiratory failure. Laboratory evaluation revealed leukocytosis (22.8 ×10?/L), true hypotonic hyponatremia (serum sodium 128 mmol/L), elevated inflammatory markers, and a positive Legionella urinary antigen test. High-sensitivity cardiac troponin was markedly elevated, peaking at 12,960 ng/L. Electrocardiography demonstrated diffuse ST-segment depressions consistent with subendocardial injury. Transthoracic echocardiography revealed severe left ventricular systolic dysfunction with an ejection fraction of 20% and regional wall motion abnormalities. Coronary angiography excluded obstructive coronary artery disease.
Despite initiation of appropriate antimicrobial therapy and initial hemodynamic stability, the patient developed sudden ventricular fibrillation arrest on hospital day two, requiring prolonged resuscitation. Post-arrest echocardiography showed further deterioration of left ventricular function with persistent severe systolic dysfunction. He progressed to refractory cardiogenic shock necessitating escalating vasopressor support. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) was initiated for combined circulatory and respiratory support, and an intra-aortic balloon pump was placed for left ventricular unloading. Despite maximal mechanical and pharmacologic therapy, the patient’s condition continued to decline, culminating in multiorgan failure and death.
Discussion: This case illustrates the fulminant and lethal potential of Legionella-associated myocarditis. The diagnosis was supported by markedly elevated cardiac biomarkers, dynamic electrocardiographic changes, severe new-onset left ventricular dysfunction, and exclusion of ischemic disease. The pathophysiology is thought to involve direct bacterial invasion and immune-mediated myocardial injury. Although rare, cardiac involvement should be suspected in patients with severe Legionella pneumonia who demonstrate elevated troponins, arrhythmias, or hemodynamic instability. Early cardiac monitoring with serial electrocardiograms, troponins, and prompt echocardiography is essential. Rapid recognition of fulminant myocarditis may warrant early consideration of mechanical circulatory support. However, as demonstrated in this case, outcomes remain poor despite aggressive intervention, underscoring the need for heightened awareness and earlier risk stratification in this high-risk population.
