Clinical significance of troponin I efflux and troponin autoantibodies in patients with dilated cardiomyopathy.

BACKGROUND: The appearance of circulating autoantibodies against cardiac troponin I (cTnAbs) in patients with heart failure has been reported. We sought to evaluate the role of circulating cardiac troponin I (cTnI) and cTnAbs in the pathophysiology and prognosis of idiopathic dilated cardiomyopathy. METHODS AND
RESULTS: Circulating concentrations of cTnI and the presence of cTnAbs were determined in 95 patients with idiopathic dilated cardiomyopathy. The patients underwent laboratory testing, echocardiography, cardiopulmonary exercise testing, gated single photon emission computed tomography, and both-sided cardiac catheterization during a 3-day study period. Compared with cTnI- patients, the hearts of cTnI+ patients (cTnI > or = 0.01 ng/mL, n = 19) were significantly more dilated (left ventricular end-diastolic diameter 67 vs 61 mm, P < .05; left ventricular end-systolic dimension, 55 vs 49 mm, P < .01; echocardiography) and demonstrated greater intracardiac volumes (left ventricular end-diastolic volume 161 vs 132 mL, P = .060; left ventricular end-systolic volume 112 vs 82 mL, P < .05; gated single photon emission computed tomography), more disturbed systolic (ejection fraction 27 vs 33%, P < .05; gated single photon emission computed tomography) and cardiac sympathetic (123I-metaiodobenzylguanidine washout: 41% vs 34%; P < .05) function, and higher levels of vasoactive peptides (N-terminal proatrial natriuretic peptide 1030 vs 558 pmol/L, P < .05; N-terminal pro-B type natriuretic peptide 337 vs 115 pmol/L, P < .05). In addition, during a median follow-up time of 4.1 years, cTnI+ patients had clinical end points (cardiovascular death, heart transplantation, or clinical need for an automatic implantable cardioverter defibrillator) more often than cTnI- patients (37% vs 8%, P < .01). The presence of circulating cTnAbs (n = 15) was not associated with patients' clinical status or outcome.
CONCLUSION: Patients with idiopathic dilated cardiomyopathy with cTnI efflux demonstrate more prominent changes in the indices of left ventricular remodeling and function than patients without signs of cTnI efflux. Moreover, elevated serum cTnI is associated with poor clinical outcome. The presence of circulating cTnAbs seems to have less utility in the clinical assessment of these patients. However, their pathogenic role in disease progression in the long term cannot be excluded.