AIM: A detailed description of immune status abnormalities of adult patients with heart arrhythmia either idiopathic or in combination with primary heart disease such as chronic myocarditis and dilated cardiomyopathy (DCMP). MATERIAL AND METHODS: Eighty two consecutive patients aged 16-57 years admitted to the L.A. Myasnikov Institute of Clinical Cardiology (Moscow) for heart arrhythmia were studied. Among them 35 patients had idiopathic heart arrhythmia (IHA, group 1) with no evidence of any primary heart disease, while other 47 patients (group 2) had heart arrhythmia combined with primary heart disease (chronic myocarditis or DCMP). In group 1 ventricular arrhythmia was recorded in 27 patients (12 cases with ventricular tachyarrhrythmia ?VTA, 15 cases with ventricular extrasystolia- VE). Supraventricular heart arrhythmia was found in 6 patients (3 cases of constantly recurring supraventriccular tachycardia, 2 cases of paroxysmal and 1 with constant atrial fibrillation). The intermittent atrioventricular block of the second-third degree was recorded in 2 patients. The patients of group 2 were divided into subgroups 2a, 2b and 2c. In subgroup 2a (patients with DCMP without signs of heart failure) ventricular arrhythmia was found in 7 patients (VT ? 5, VE ? 2). Supraventricular arrhythmia was recorded in 7 patients 5 of which had constantly recurring supraventricular tachycardia, 1 ? paroxysmal and 1 constant atrial fibrillation. In subgroup 2b (DCMP patients with obvious signs of heart failure) ventricular arrhythmia was recorded in 12 patients, among them 6 had VT and 6 ? VE, 2 ? constant atrial fibrillation). In subgroup 2c (patients with chronic myocarditis) ventricular arrhythmia was in 7 patients (VT ? 5, VE ? 2), constant atrial fibrillation ? in 2, heart conduction abnormalities ? in 3 patients, atrioventricular block of the first or second degree ? in 2, sick sinus syndrome ? in 1. To verify the diagnosis, all the patients have undergone physical examination, blood cell counts and biochemical tests, urine clinical analysis, ECG and ultrasound heart examination as well as 24h ECG monitoring. On demand, bicycle exercise test or treadmill test, coronaroangiography, endomyocardial biopsy and invasive electrophysiological examination were made. RESULTS: Immune status abnormalities found in patients with heart arrhythmia both idiopathic and combined with primary heart diseases such as chronic myocarditis and DCMO correspond to immune defense response during chronic infection. Activation of different anti-infection defense mechanisms was recorded in patients with idiopathic heart rhythm and conductivity abnormalities. Immune deficiency was found in arrhythmia and conductivity abnormalities combined with primary heart diseases (chronic myocarditis or DCMP). A positive correlation exists between the degree of immune defense failure and reduction of myocardial contractility. CONCLUSION: There exists a characteristic pattern of immune status abnormalities in patients with arrhythmia, both idiopathic or combined with primary heart disease (myocarditis, DCMP). The abnormalities depend on severity of arrhythmia, intensity of inflammatory processes in the myocardium and on the degree of left ventricular contractility dysfunction in patients with primary heart diseases.