Post-Diphtheritic Myocarditis with Right Ventricular Thrombus: A Rare Cardiac Complication

Myocarditis is a serious consequence of diphtheria; however, the occurrence of a subsequent right ventricular (RV) thrombus is exceedingly rare. We provide an uncommon case of post-diphtheritic myocarditis complicated by a right ventricular thrombus and secondary pneumonia, emphasizing its effective multi-modal therapy and subsequent recovery.

A 19-year-old female arrived at our emergency department with acute dyspnea and chest pain two weeks after a 3-day hospitalization for pharyngeal diphtheria at Galkacyo Regional Hospital. Laboratory analyses revealed increased Troponin I (2615 ng/L), CK (511 U/L), and severely high NT-proBNP (33,349.0 pg/mL). Chest radiography verified the presence of simultaneous right lower lobe pneumonia. Electrocardiography revealed low-voltage QRS complexes, whereas echocardiogram indicated worldwide hypokinesia (LVEF 40-45%) and a movable hypoechoic mass at the right ventricular apex, strongly suggesting the presence of a right ventricular thrombus.

The patient was admitted to a designated ICU bed and commenced on broad-spectrum antibiotics, guideline-recommended heart failure pharmacotherapy (metoprolol, furosemide, empagliflozin), and therapeutic anticoagulation with subcutaneous enoxaparin. She was released on a two-month regimen of oral anticoagulation. Five-month serial follow-up demonstrated total clearance of the right ventricular thrombus, a fully normalized ejection fraction, and complete remission of all symptoms.

This case demonstrates that patients continue to be susceptible to toxin-induced myocarditis and intracardiac thrombosis even in the convalescent phase. It highlights Virchow's Triad in post-diphtheritic conditions and illustrates that timely heart failure treatment, along with a systematic 2-month anticoagulation protocol, can result in remarkable myocardial healing and total thrombus clearance.