[The sick sinus syndrome. What causes it?]

The basic disorder in sinoatrial disease is a functional and/or anatomical defect in the sinus node and the atrium respectively. The clinical feature includes palpitations, angina pectoris, heart failure, giddiness and systemic emboli. Associated diseases are coronary heart disease, hypertension, diphtheria, myocarditis or rheumatic fever. Diagnosis is primarily made by clinical symptoms and conventional or long term ECG-monitoring. However, impaired sinus node function including sinusbradycardia, sinus arrest, sinoatrial block and the bradycardia-tachycardia syndrome cannot easily be assessed, when rhythm disturbances are occurring intermittently, as the recording of electrical activity of sinus node pacemaker cells is not available in man. Therefore methods of provocative atrial stimulation (rapid atrial stimulation, premature atrial stimulation) have been developed for (indirect) estimation of sinus node recovery time and sinoatrial conduction time. Treatment depends on symptoms. In most cases implantation of an electric pacemaker is mandatory since drug treatment usually is unsatisfactory. The natural history of the sinoatrial disease is imperfectly known but probably covers 5--10 years.