Gabriel Gregoratos, MD, FACC, Clinical Professor, Emeritus, Division of Cardiology, University of California, San Francisco, CA, USA.

Syncope accounts for six percent of all hospital patient admissions and is a common and frequently debilitating symptom in older patients. The common causes of syncope in older populations are orthostasis, cardiac arrhythmias, neurocardiogenic syncope, and carotid sinus hypersensitivity. The cause of syncope can usually be deduced or suspected by simple initial clinical evaluation. Arrhythmic syncope will usually require ambulatory ECG monitoring or possibly an implantable loop recorder for precise diagnosis. Neurocardiogenic syncope can be frequently confirmed with a tilt-table test and carotid sinus hypersensitivity by careful carotid sinus stimulation during ECG rhythm monitoring. A permanent pacemaker is indicated for all types of symptomatic bradycardia whether complete AV block, severe sinus bradycardia, or the bradycardia-tachycardia syndrome in patients with sinus node dysfunction. Pacemaker therapy is also indicated to prevent certain pause-dependent tachyarrhythmias, although its role in atrial fibrillation remains controversial unless there is clear evidence of bradycardia-tachycardia sequence. Pacing therapy can also effectively treat syncope due to carotid sinus hypersensitivity when the cardioinhibitory component (heart rate slowing) predominates. The role of pacing therapy for neurocardiogenic (vasovagal) syncope remains controversial.
Key words: syncope, pacemakers, neurocardiogenic, carotid sinus, bradycardia-tachycardia.

Physiologic Vs. Ventricular Pacing--Which is More Appropriate for Your Elderly Patient?

Tawfic Nessim Abu-Zahra, BSc, MSc

Cardiac pacemakers are widely used to treat the symptoms of cerebral hypoperfusion and hemodynamic decompen-sation that are caused by bradycardia.¹ Pacemaker implantation is indicated for diseases of the sino-atrial (SA or sinus) and the atrioventricular (AV) nodes. There are two different modes of cardiac pacing, ventricular and physiologic. Ventricular pacing involves the direct stimulation of the ventricular myocardium without interaction with the atria, whereas physiologic pacing stimulates either the atria alone (atrial pacing) or both the atria and ventricles together (dual pacing).

There are many theoretical reasons why physiologic pacing should be superior to ventricular pacing. Physiologic pacing maintains the synchrony of atrial and ventricular contraction and the dominance of the sinus node by stimulating both the atria and ventricles.² Physiologic pacing may prevent the pacemaker syndrome--a collection of symptoms associated with the asynchronous contraction of the heart that occurs with ventricular pacing.² In comparison to ventricular pacemakers, however, physiologic pacemakers are more expensive, and are more difficult to monitor.³

Despite the theoretical advantages of physiologic pacemakers, this mode of pacing is not widely used.