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Sick sinus syndrome.

The sick sinus syndrome describes a rather heterogeneous group of patients whose presenting symptoms are primarily cerebrovascular in nature (Stokes-Adams attacks, dizziness, and cerebrovascular accidents). The principal pathophysiological disturbance is "sinus node" dysfunction characterized by bradyarrhythmias (sinus bradycardia, sinoatrial block, sinus arrest) with or without associated tachyarrhythmias (tachycardia-bradycardia syndrome).1An interest in and an awareness of this syndrome is mandated by the frequency of these complaints. Historically, the first causal relationship delineated was between Stokes-Adams attacks and sinus bradycardia and sinoatrial block.2-4Later in 1954 Short5described syncope in patients with alternating bradyarrhythmias and tachyarrhythmias. Lown6actually coined the term "sick sinus" syndrome to describe a group of patients in whom, after electrical cardioversion, chaotic atrial activity, bradycardia, ectopic beats, and atrial and nodal tachycardia developed. Ferrer7ultimately grouped these patients with diverse symptoms and dysrhythmias together under the general heading "sick sinus syndrome" in