on behalf of EP-Europace)This article is published simultaneously in Europace and is available online at http://dx. PrevalenceThe two constantly growing global health problems (that is, HF and AF) often co-exist, or may precipitate one another. Recent registry-based reports show that ∼40% of patients hospitalized for

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Thirty-one patients with nonischemic dilated cardiomyopathy either idiopathic or due to regurgitant valvular disease were studied in the cardiac electrophysiology lab. The indications for study were sustained ventricular tachycardia (VT) in 16, ventricular fibrillation (VF) in 11, and syncope of unknown etiology in 4. Sustained VT was reproducibly induced in 17 patients, including 12 with a history of sustained VT, 2 with VF and 3 with syncope. Of 15 patients undergoing serial antiarrhythmic drug studies, sustained VT was rendered noninducible or nonsustained in 13. Three had recurrent arrhythmic events while on therapy predicted to be effective. One of 2 patients discharged on a regimen predicted to be ineffective had a recurrence of sustained VT that resulted in cardiac arrest. Of 14 patients in whom sustained VT could not be reproducibly induced, 2 subsequently had spontaneous occurrences of sustained VT, and 2 experienced aborted sudden death. These results suggest the following: (1) the induction of sustained VT in the setting of nonischemic dilated cardiomyopathy is dependent on the clinical presentation; (2) antiarrhythmic drugs frequently render sustained VT noninducible or nonsustained; (3) antiarrhythmic drug suppression of inducible sustained VT predicts long-term prevention of spontaneous recurrences; and (4) noninducibility of sustained VT in the baseline state does not predict freedom from subsequent episodes of VT or sudden death.

The relationship between heart rate response and the dynamic changes in the PR interval was assessed in 631 patients undergoing routine cardiac exercise tests for a variety of clinical indications. Patients were stratified into four subsets: nonmedicated normals (n = 437), patients on beta-antagonist agents (n = 118), those on antiarrhythmic agents alone (n = 61) and those with a clinical diagnosis of advanced (New York Heart Association [NYHA] Class III or IV) congestive heart failure. All patients were in stable sinus rhythm throughout the test. PR intervals were measured at rest, at mid-exercise and at peak exercise. Mean PR intervals shortened to a statistically significant degree in most subgroups. This effect was predominantly observed in the earlier stages of exercise. In patients with advanced heart failure, there was no statistically significant shortening of exercise PR intervals later in exercise, demonstrating a parallel with their relatively blunted heart rate response. These changes in exercise PR intervals suggest that implanted pacemaker algorithms may be constructed to maximize hemodynamic benefit in patients requiring physiological pacemakers.

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Thirteen patients were implanted with the Telectronics 4210 ATP implantable cardioverter defibrillator (ICD) for ventricular tachycardia or ventricular fibrillation. This device has multiprogrammable antitachycardia pacing, bradycardia pacing, and shock therapies. In addition, there is extensive data logging and ECG snapshot capability for arrhythmia confirmation and response to therapy. These features permit easy retrieval of all detected and treated events, whatever the eventual outcome. In this study, the data logged at predischarge electrophysiological testing was compared to the data recorded in a standard manner. The bulk of the data, however, was derived from long-term follow-up of spontaneous events over a mean period of 203 days (range 154-257). During this period, a total of 6,193 arrhythmia detections were made: 20 were classified as ventricular fibrillation, and 6,173 as ventricular tachycardia. The vast majority of these (93%) terminated spontaneously without ICD intervention (5,738), underscoring the benefit of a standard second confirmation prior to therapy delivery (noncommitted system). There were 394 arrhythmia episodes treated with antitachycardia pacing; of these a total of 8.3% accelerated to either more rapid ventricular tachycardia or ventricular fibrillation (4.3% and 4.0%, respectively). Events were reported in an "episode log" format, listing all arrhythmia detections with time/date annotation; or in a "sense history" format, detailing each episode from start to conclusion. These data demonstrate that this advanced, "tiered" ICD with data recall contributes to better patient management, and permits a more tailored termination prescription for the individual patient.