Arrhythmogenic cardiomyopathy. Prospects for assessing the degree of electrical instability in the damage zone

Introduction Arrhythmogenic cardiomyopathy (ACMP) is the leading cause of sudden death in athletes. However, its diagnosis is one of the most challenging tasks in modern cardiology, as this disease is a general term for pathological processes. Diagnosing the early manifestations of ACM before the development of fibrotic changes and in the absence of a proven genetic disorder is particularly important. Assessing the transport capacity of cardiomyocyte membranes and the activity of mitochondrial synthesis is of particular interest. Myocardial scintigraphy with the radiopharmaceutical Technetium (99mTc) Sestamibi - MIBI Tc 99 offers this capability. This drug penetrates cardiomyocytes and mitochondria via passive transmembrane diffusion, similar to potassium ions, and characterizes the functional activity and condition of membranes. Mechanisms of arrhythmia development in arrhythmogenic cardiomyopathy. Purpose To determine the possibility of identifying loci of limited or diffuse disturbance of the transport functions of cardiomyocyte membranes in athletes with ventricular extrasystole. Methods Group 1: Cyclic sports athletes, mean n=39, age 32.5±9.5 years, professional experience 10±4 years, with documented ventricular arrhythmias. Group 2: Control group: mean n=32, age 32±1 years, p>0.05. No cardiovascular abnormalities. Completed Medical history, clinical examination, ECG, Holter monitoring, echocardiography, and SPECT with Technetium (99mTc) Sestamibi - MIBI Tc 99 at a dose of 400-500 MBq at rest. Results In Group 1, all patients complained of fatigue during the last months of training and a decline in athletic performance. In Group 1, rare ventricular extrasystoles (less than 1,000 per day) were observed, with a pattern of complete left bundle branch block and superior axis in 35% of cases and inferior axis in 55% (5% of combinations). Ventricular extrasystoles with complete right bundle branch block and inferior axis were observed in 78% of cases and superior axis in 24% (4% of combinations). Combinations of right and left bundle branch blocks were observed in 36%. According to echocardiography, contractility and diastolic function of the left and right ventricles were normal. All patients in Group 1 had reproducible arrhythmia in response to stress testing. There were no abnormalities in Group 2. When performing SPECT, the number of sectors with unchanged RFP uptake >70% of the maximum in group 1 was 8.0±3.4, in group 2 - 18±2.6. The correlation of the number of sectors with the total number of ventricular extrasystoles r=0.3, p<0.05. Conclusion Impaired uptake of the radiopharmaceutical MIBI Tc 99 may indirectly reflect the presence of myocardial areas with impaired transport functions of cardiomyocytes in relation to the accumulation and/or excretion of electrolytes (potassium) and is a marker of electrical instability of the myocardium.