FROM THE EDITOR…

New indications for cardiac pacing are infrequent. The classic indication is, of course, atrioventricular block. It was not until 1967 that a case which we would, today, name sick sinus syndrome was treated with implanted cardiac pacing. Virtually until this day no additional indications have stood the test of searching inquiry and long-term evaluation. Antitachycardia pacing of the atrium (or of the ventricle) to terminate supraventricular tachycardia has heen long evaluated and despite some notable successes has found only limited utility. Pacing the ventricle for termination of ventricular tachycardia has proven to he sometimes effective, too frequently ineffective, and often dangerous, producing acceleration to a different tachycardia and even to ventricular fihrillation. Resurgence of its utility will be associated with implantahle defibrillation. Tachycardia termination by pacing will he attempted first. If pacing is unsuccessful or results in acceleration, a far larger shock will terminate the tachy-fibrillation. If AV hlock or sinus bradycardia occurs, ventricular antibradycardia pacing will occur. There are many reasons that antitachycardia pacing of the atrium has fallen into disfavor. Effective drugs exist, hut more importantly a technique has gradually evolved in which the unmanageable atrial rhythm is effectively blocked from passing its disordered or pathological rhythm to the ventricle. The technique is, of course, that of AV node ahlation hy one of a series of techniques, including direct electrical destruction. Such interventions have been reported from many centers, with a very high rate of success. While an occasional episode of late and totally unexpected sudden death has clouded the outlook, still it is hoped that this occurrence will he a rarity and not affect the overall utility of AV node ahlation. AV node ablation artificially produces AV block. A reentry pathway may be interrupted and a circus movement tachycardia prevented or an atrial arrhythmia may be prevented from heing conducted to the ventricle. The subsequent implantatibn of a single chamher rate modulated pacemaker restores a consistent rhythm to the ventricle, and provides rate variation in response to activity needs. The reliability and longevity expectation of modern lead systems and pulse generators is such that the purposeful production of irreversible AV block is a reasonable alternative to other methods of arrhythmia management. Once AV block is durable, late return of conduction has not heen reported (early return of conduction does demonstrate inadequate ablation), in effect cure of the arrhythmia is permanent. Medications previously required to slow the atrial arrhythmia, the ventricular response or slow AV conduction are no longer needed and the hurden of side effects is reduced. In young women who may want to become pregnant, the avoidance of cardioactive medications is highly desirable and has, in the past, heen an indication for atrial antitachycardia pacing with all of the uncertainties of that approach. AV node ahlation is a far more satisfactory approach. If undertaken in a young person the expectation is for many years of pacing. Each of us who has ohserved patients over a prolonged period knows that the longer a pacing system is in situ, the greater is the likelihood for some malfunction. Still, the likelihood is now small and the expectation is for prolonged, satisfactory management. Unless some late and unexpected complications become manifest, it is likely that a new indication for cardiac pacing now exists. With increasing confidence in the safety, efficacy and long-term reliahility of AV node ablation and skill in its minimally intrusive achievement we are likely to see increasingly widespread use in young and in older patients. Far from heing an arcane therapy, cardiac pacing is widely used, the technology is availahle throughout the industrialized world and it is a therapeutic intervention with a low complication rate. Even in the elderly the avoidance of long-term administration of medication is most beneficial. Overall, we will see progressively increasing utilization of AV node ahlation. Its combination with implanted pacing, especially rate modulated pacing, works very well, indeed.