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Abstract:
Bradyarrhythmias are due to disturbance of impulse formation and conduction in the heart. The sick sinus syndrome consists of both forms, sinusbradycardia being the most common type of arrhythmia, followed by sinus arrest and sinuatrial block. There is a wide range of the reported frequency of concomitant intermittent supraventricular tachycardia. Most patients have additional atrioventricular conduction disturbances. Diagnostic methods include measurement of the sinus node recovery time and sinoatrial conduction time, but therapy, i.e. pacemaker implantation depends largely on documentation of significant reduction of heart rate with clinical symptoms. The largest group of bradycardias is due to high degree atrioventricular block. As the prognosis of Mobitz Type II block is unfavorable in regard to development of complete distal av-block, differentiation between type I and II is of clinical importance, particularly in patients with additional fascicular block. Although exact localization of conduction disturbance with the Hisbundle-electrogram is possible, proof or exclusion of block distal to the Hisbundle including high frequency testing with atrial stimulation does not give the sole indication for therapeutic measures as follow up studies of patients with intraventricular conduction disturbances with and without distal block have demonstrated, that progression to complete av-block is difficult to predict.