Pathophysiological characteristics, diagnostic problems and assessment of sinus node dysfunction.

Based on clinical and experimental experience, sick sinus syndrome can be divided into two groups: intrinsic and autonomic neurovegetative pacemaker dysfunction. Sinus node activity is characterized electrophysiologically by automaticity, recovery and sinoatrial conduction. The automaticity of the sinus pacemaker cell groups and sinus recovery can be differentiated properly under experimental conditions. Studies of the electrophysiological characteristics showed the basic functional parameters to be normal in autonomic sinus dysfunction. Diagnosis is either based on clinical observation or on the data of Holter monitoring, the electrophysiological methods being inadequate for diagnosing this neurovegetative form of sick sinus syndrome. On the other hand, intrinsic-organic sinus dysfunction can be diagnosed by electrophysiological tests. If completed by complex pharmacological studies, in this organic form of sick sinus syndrome, even the severity of the intrinsic injuries can be assessed quantitatively. This division provides a logical basis for a proper selection and evaluation of the differential diagnostic procedures, while information on the aetiopathology of sinus dysfunction and on the degree of the functional injuries of the electrophysiological structure of the heart provides an adequate basis for therapy.