Objectives: The study evaluates the clinical course and the development of systolic and diastolic left ventricular function in patients with chronic myocarditis with or without autoantibodies against cardiac myosin.
Background: Patients with myocarditis often show autoantibodies against cardiac myosin. The clinical and pathophysiologic significance of these antimyosin autoantibodies (AMAAB) is yet unknown. The results from studies comparing the clinical course and the development of left ventricular function in patients with chronic myocarditis with or without AMAAB are not yet available.
Methods: Thirty-three patients with biopsy proven chronic myocarditis underwent analysis of AMAAB, right and left heart catheterization and left ventriculography at baseline and after six months. Left ventricular volumes and ejection fraction as well as the time constant of left ventricular relaxation "tau" and the constant of myocardial stiffness "b" were determined at baseline and at follow-up.
Results: In 17 (52%) patients, AMAAB could be detected at baseline. After six months, AMAAB were still found in 13 (76%) initially antibody-positive patients. No initially antibody-negative (n = 16) patient developed AMAAB during follow-up. Clinical symptoms improved slightly in antibody-negative patients and remained stable in antibody-positive patients. Left ventricular ejection fraction developed significantly better in antibody-negative patients (+8.9 +/- 10.1%) compared with antibody-positive patients (-0.1 +/- 9.4%) (p < 0.012). Stroke volume (SV) and stroke volume index (SVI) also improved in antibody-negative patients (SV: +20 +/- 31 ml; SVI: +10 +/- 17 ml) compared with antibody-positive patients (SV: -14 +/- 43 ml; SVI: -8 +/- 22 ml) (SV: p < 0.015; SVI: p < 0.016). Left ventricular end-diastolic and end-systolic volumes and the time constant of left ventricular relaxation "tau" did not change significantly different in antibody-positive and antibody-negative patients. The constant of myocardial stiffness "b" improved significantly in antibody-negative patients (-6.1 +/- 10.8) compared with antibody-positive patients (+7.3 +/- 22.6) (p < 0.040). Analyzing only the persistently antibody-positive patients yielded essentially the same results.
Conclusions: Antimyosin autoantibodies are associated with worse development of left ventricular systolic function and diastolic stiffness in patients with chronic myocarditis.