Publication date: Jul 30, 2026
Persistent cardiac symptoms are common in post-COVID syndrome, even without structural heart disease. Evidence implicates immune dysregulation, endothelial dysfunction and low-grade cardiovascular inflammation. Yet no targeted treatment exists. Myoflame-19 is a multicenter, double-blind clinical trial of 279 participants with inflammatory cardiac involvement defined by cardiovascular magnetic resonance, randomized 1:1 to losartan plus prednisolone (n = 139) or matching placebos (n = 140) for 16 weeks. The modified intention-to-treat population comprised 124 and 122 participants. The primary endpoint, change in left ventricular (LV) ejection fraction, was neutral: between-group difference 0. 74 percentage points (pp), 95%CI -0. 14 to 1. 62, p = 0. 10, unpaired t-test; supportive baseline-adjusted ANCOVA 0. 99, 95%CI 0. 15-1. 83, p = 0. 021. Among prespecified secondary endpoints, several symptom and imaging measures showed numerical differences favoring intervention, including Average Symptom Score components (modified Canadian Chest Pain Scale -4. 8 pp, 95%CI -17. 3 to 7. 6; NYHA class -8. 1 pp, -20. 6 to 4. 3; Long COVID symptom burden -7. 7 pp, -18. 9 to 3. 6), native T1 and T2 values (native T1 -2. 46 ms, -8. 35 to 3. 42; native T2 -0. 31 ms, -1. 16 to 0. 53), and LV end-diastolic volume ( + 1. 45 ml/m^2, -0. 09 to 3. 00); however, confidence intervals included the null value and these findings should be regarded as hypothesis-generating. Treatment was safe and well-tolerated. These findings indicate a neutral treatment effect on the primary endpoint. They inform targeted immunomodulation and design of future trials in post-COVID syndrome and inflammatory cardiac involvement. Trial registration: EudraCT 2022-001682-12; NCT05619653.