BACKGROUND: Left ventricular noncompaction cardiomyopathy is one of the rare forms of primary cardiomyopathy with an unfavorable prognosis and disease course. The mortality among the adult population is approximately 50%. The clinical signs are not specific and the diagnostics in some cases takes a long period of time. In this article, based on an example of one of the variants of cardiomyopathy development, a path of setting the diagnosis and adjusting the treatment in real-life clinical practice is described. CLINICAL CASE DESCRIPTION: In the patient with a noncompaction cardiomyopathy in the left ventricle, the leading clinical symptoms were the complex cardiac rhythm disorders (ventricular extrasystoles of high grade, paroxysmal-persistent form of atrial fibrillation and flutter), the development and the progression of cardiac failure with the decreased ejection fraction down to 22%. The adjustment of the antiarrhythmic and the pulse-decreasing therapy was done, as well as the attempts of medicinal stabilization of the course of cardiac failure. Due to the inefficiency of conservative therapy with the development of uncontrolled rhythm disorders and the terminal cardiac failure, the orthotopic heart transplantation was carried out. CONCLUSION: The presented clinical case demonstrates a variation of the progressive course of the left ventricular noncompaction cardiomyopathy with the development of terminal cardiac failure within 4 years after the onset of the disease, requiring the heart transplantation. The clinicists and the functional and ultrasonic diagnostics specialists need to be aware of the rare forms of cardiomyopathies, including the asymptomatic variants, for the timely diagnostics and for adequate treatment.