This paper reports the results of an electron microscopic study of the sinoatrial node in deceased patients with CHD in whom high-resolution rhythmocardiography revealed autonomous cardioneuropathy. Non-specific morphological changes in pacemaker cells of the sinoatrial node (swelling and disintegration of mitochondria, incorporation of calcium and accumulation of lipofuscin in mitochondria) can be regarded as manifestations of ischemic insufficiency of cardiac tissue perfusion. The rhythmocardiograms of such patients showed signs of autonomous cardioneuropathy manifest as the sharply decreased amplitude of all vegetative waves. The spectral power pattern was dominated by inefficient humoral-metabolic regulation due to suppression of protective parasympathetic regulation.