[Sinus node syndrome].

The sick sinus syndrome is caused by dysfunction of the sinus node and includes various forms of arrhythmia. In its chronic form the underlying disease may affect not only the sinus node but also the atrial, junctional and intraventricular conduction tissue. The most important clinical symptoms are, in decreasing order, dizziness, syncope, palpitations, cardiac failure, systemic embolism, and cerebrovascular insult. The main diseases causing dysfunction of the sinus node are coronary heart disease, myocarditis, and rheumatic fever. The diagnosis is based on history, clinical findings, ECG, specific provocative tests and, if necessary, long-term ECG monitoring. The sick sinus syndrome is most frequently seen in patients aged over 50 years. Treatment with drugs alone, such as atropin, catecholamines, digitalis or antiarrhythmic drugs is often difficult becuase of the frequent changes between bradycardic and tachycardic arrhythmia. In chronic and progressive cases, the best treatment is implantation of a cardiac pacemaker.