ELL TO BEDSIDE IMPLICATIONS ASSOCIATE EDITOR : STANLEY NATTEL ge , gender , and supraventricular arrhythmias : Roles of on channels , connexins , and tissue architecture ?

i o s d s d H t W A w o t t i u The results reported in this issue of Heart Rhythm by orter et al suggest that AV nodal reentrant tachycardia AVNRT) is more common in women than men and that ging makes AV reciprocating tachycardia less likely and VNRT and focal atrial tachycardia (AT) more likely. hese observations imply differences in the basic electrohysiology of the AV node, the atrium, and the accessory athways that are determined by age and gender. Changes in on channel function and/or regulation (e.g., by the autoomic nervous system), in connexin distribution, and in issue architecture all could be involved. Aging importantly changes basic cardiac electrophysilogic properties. Resting potential, action potential ampliude, and phase 0 upstroke velocity are not altered in atrial ardiomyocytes of elderly dogs, but the plateau is more egative and the action potential duration is longer. L-type a currents are reduced in right atrial cells from elderly ogs, although maximally stimulated current in the presence f isoproterenol is unchanged. Much less is known about currents, although the transient outward current system eems to be increased in elderly dogs. Innervation of the ardiac conduction system decreases with advancing age, s does the ability of adrenergic stimulation to antagonize holinergic effects. A consistently reported change in elerly atria is an increase in fibrous tissue, which is associted with an increased ability to maintain atrial fibrillaion. Myofiber width increases with aging, and ntermyocyte fat cell infiltration occurs. Studies of conexin43 changes have provided conflicting results, with one howing reduced connexin expression in lateral cell memranes and another increased lateral expression. Transerse conduction is selectively reduced, and “zigzag” onduction patterns that can lead to microreentry are faored. There is an interesting interaction between age and aploinsufficiency of the gene encoding the cardiac Na