Secondary myocarditis refers to inflammatory processes of the myocardium that arise in the context of systemic diseases. They do not result from direct infection of the cardiac tissue, but from autoimmune, paraneoplastic, toxic mechanisms or reactions to drugs. In some cases, secondary myocarditis may progress to secondary cardiomyopathy, characterized by chronic remodeling and dysfunction of the myocardium.
Classification of Secondary Myocarditis
Autoimmune Myocarditis
Autoimmune diseases can trigger myocardial inflammation through autoantibodies and immune activation. The main conditions include:
Systemic Lupus Erythematosus (SLE): diffuse myocardial inflammation, often associated with pericarditis.
Rheumatoid Arthritis: possible granulomatous myocarditis with cardiac fibrosis.
Scleroderma: vasculitic phenomena and progressive myocardial fibrosis.
Polymyositis and Dermatomyositis: lymphocytic infiltrates with progressive ventricular dysfunction.
Sjögren’s Syndrome: possible cardiac involvement with myocardial inflammation.
Vasculitides (e.g. Granulomatosis with Polyangiitis, Takayasu’s Disease): may cause myocardial ischemia and inflammation of the cardiac tissue.
Paraneoplastic Myocarditis
Neoplasms may induce myocarditis through autoimmune reactions or paraneoplastic inflammation:
Lung Carcinoma: autoimmune response with lymphocytic myocarditis.
Hematologic Neoplasms (Lymphomas, Leukemias): direct infiltration of the myocardium or autoimmune response.
Carcinoid Syndrome: release of mediators with myocardial fibrosis.
Melanoma: possible myocarditis through immune-mediated mechanisms.
Myocarditis Due to Drug and Vaccine Reactions
Certain drugs and vaccines can trigger immune-mediated reactions resulting in myocardial inflammation:
Checkpoint Inhibitors (Oncological Immunotherapy): autoimmune myocarditis with risk of severe ventricular dysfunction.
Anthracyclines (Chemotherapeutic Agents): dose-dependent toxicity with necrotizing myocarditis.
mRNA Vaccines (SARS-CoV-2): rare cases of post-vaccine myocarditis, often self-limiting.
Antipsychotics (e.g. Clozapine): documented risk of idiosyncratic myocarditis.
Secondary Myocarditis Due to Systemic Infectious Diseases
Some systemic infections do not directly affect the heart, but trigger a myocardial inflammatory response:
Sepsis: release of inflammatory cytokines with myocardial dysfunction.
HIV/AIDS: chronic lymphocytic myocarditis with ventricular dysfunction.
Kawasaki Disease: pediatric vasculitis with risk of coronary aneurysms.
Brucellosis: granulomatous myocarditis with valvular involvement.
Syphilis: myocardial inflammation with aortic aneurysms.
Complications of Secondary Myocarditis
Secondary myocarditis may lead to serious cardiac complications, including:
Acute heart failure: in the most aggressive forms with severe myocardial dysfunction.
Ventricular arrhythmias: increased risk of sudden death.
Cardiogenic shock: in cases of fulminant myocarditis.
Secondary myocarditis represents a heterogeneous group of conditions related to systemic diseases. Early recognition of the underlying condition is essential for treatment and prevention of cardiovascular complications. In cases where inflammation leaves fibrotic outcomes and chronic dysfunction, the picture may evolve into secondary cardiomyopathy, which requires a different therapeutic approach.
References
Caforio et al. Myocarditis: current clinical and diagnostic approaches. European Heart Journal. 2021; 42(36): 3873-3884.
Ammirati et al. Management of myocarditis related to immune checkpoint inhibitors. Journal of the American College of Cardiology. 2022; 79(3): 203-216.
Friedrich et al. Cardiac MRI in suspected myocarditis: clinical perspective and contemporary update. European Heart Journal. 2018; 39(21): 1904-1913.
Kindermann et al. Update on myocarditis. Journal of the American College of Cardiology. 2012; 59(9): 779-792.
Bachmaier et al. Autoimmune and inflammatory mechanisms in myocarditis: pathophysiology and clinical implications. Cardiology Clinics. 2022; 40(4): 579-595.
Bozkurt et al. Current diagnostic and treatment strategies for specific etiologies of myocarditis in adults. Current Cardiology Reports. 2021; 23(12): 175-188.
Peretto et al. Autoimmune myocarditis: clinical presentation, diagnosis, and management. Heart Failure Clinics. 2023; 19(1): 53-66.
Chimenti et al. Paraneoplastic and toxic myocarditis: new perspectives. European Journal of Heart Failure. 2021; 23(6): 948-955.
Mahmood et al. Myocarditis with immune checkpoint inhibitors: a systematic review. Circulation: Heart Failure. 2018; 11(3): e004917.
Seferović et al. Heart involvement in systemic autoimmune diseases. Rheumatology. 2021; 60(SI): SI3–SI13.
ESC Scientific Document Group. 2023 ESC Guidelines for the diagnosis and management of cardiovascular disease in patients with cancer. European Heart Journal. 2023; 44(41): 3548-3687.
