[Bradycardia-induced syncope]

Bradyarrhythmias are the cause of syncope in 3 to 10% of cases. Marked bradycardia or asystole can be due to impaired function of the sinus node (sick sinus syndrome), high degree AV block or neurocardiogenic disorders (carotid sinus syndrome, vasovagal syncope). A precise history, ECG and 24-h. Holter recordings are the most helpful tools in diagnosis of bradyarrhythmia-induced syncope. An association between symptoms and documented ECG is essential for proper diagnosis. Sometimes an event-recorder may be helpful for this purpose. If a patient has normal physical examination, ECG, Holter, stress test, tilt-table test and echocardiography, no further electrophysiological investigation is needed. If the noninvasive tests show pathologic results that do not clearly explain the cause of syncope (sinus bradycardia, first-degree AV block, fascicular block, structural heart disease), then electrophysiological studies are recommended, which will also rule out ventricular tachyarrythmias in the differential diagnosis. If all diagnostic tests in a patient with syncope are normal, the prognosis is fairly good despite 30% recurrence rate. Treatment for symptomatic bradyarrhythmias is implantation of a pacemaker. The selection of an appropriate pacemaker system is very important. Dual-chamber systems (DDD) provide physiological stimulation by maintaining AV synchrony; thus, they should be preferred whenever possible.