Background-The recent availability of implantable cardioverter-defibrillators (ICDs) that record 1024 R-R intervals preceding a ventricular tachyarrhythmia (VTA) provides a unique opportunity to analyze heart rate variability (HRV) before the onset of VTA. Methods and Results-Fifty-eight post-myocardial infarction patients with an implanted ICD for recurrent VTA provided 2 sets of 98 heart rate recordings in sinus rhythm: (1) before a VTA and (2) during control conditions. Three subgroups were considered according to the antiarrhythmic (AA) drug regimen. A state of sympathoexcitation was suggested by the significant reduction in HRV before VTA onset compared with control conditions. ␤-Blockers and dl-sotalol enhanced HRV in control recordings; nevertheless, HRV declined before VTA independent of AA drugs. A gradual increase in heart rate and decrease in sinus arrhythmia at VTA onset were specific findings of patients who received dl-sotalol. Conclusions-The peculiar heart rate dynamics observed before VTA onset are suggestive of a state of sympathoexcitation that is independent of AA drugs.

High frequency alternating current ablation of an accessory pathway was performed in a patient with incessant circus movement tachycardia using a right-sided, free wall accessory pathway. Antiarrhythmic drugs, antitachycardia pacing and transvenous catheter ablation using high energy direct current shocks could not control the supraventricular tachycardia. A 7F bipolar electrode catheter with an interelectrode distance of 1.2 cm was positioned at the site of earliest retrograde activation during circus movement tachycardia. At this area, two alternating current high frequency impulses were delivered with an energy output of 50 W through the distal tip of the bipolar catheter, while the patient was awake. After the first shock supraventricular tachycardia terminated and accessory pathway conduction was absent without altering anterograde conduction in the normal atrioventricular (AV) conduction system. No reports of pain or other complications were noted. In short-term follow-up of 5 months, the patient had been free of arrhythmias without antiarrhythmic medication. Thus, high frequency alternating current ablation was performed for the first time in the treatment of an arrhythmia incorporating an accessory pathway in a human. This technique may be an attractive alternative to the available transcatheter ablation techniques and to antitachycardia surgery.

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To assess the efficacy of map-guided antitachycardia surgery, induction of ventricular tachycardia has mostly been performed using endocardial stimulation. In addition, epicardial stimulation can be done using temporary epicardial wires, thus not requiring post-operative catheterization. However, the diagnostic value of epicardial versus endocardial stimulation for the post-operative evaluation of patients undergoing map-guided surgery for drug-refractory ventricular tachycardia is not known, especially with regard to the induction of non-clinical tachyarrhythmias. Therefore, we compared the results of epicardial and endocardial programmed ventricular stimulation in 58 consecutive patients in whom pairs of steel wires were placed over the right ventricle during surgery. The stimulation protocol consisted of single and/or double premature stimuli during sinus rhythm and paced ventricular drives of 500, 430, 370 and 330 ms. Pre-operatively, all patients had inducible monomorphic ventricular tachycardia by endocardial stimulation. Post-operatively, 36 patients were not inducible by either epicardial or endocardial programmed ventricular stimulation, whereas epicardial and endocardial stimulation induced the clinical ventricular tachycardia in six patients and non-clinical ventricular tachycardia in three patients (45/58 patients, 77% concordant). However, in two patients the clinical ventricular tachycardia was induced only by endocardial programmed ventricular stimulation. Non-clinical ventricular tachycardia was inducible in three patients by epicardial stimulation only, and in eight patients by endocardial stimulation only (13/58 patients, 23% discordant). Thus, in 77% of patients an identical result of programmed ventricular stimulation was obtained using epicardial and endocardial stimulation, whereas the results were discordant in 23%. Therefore, epicardial stimulation alone is not sufficient for the post-operative evaluation after map-guided surgery.