Reprogramming the tachycardia parameters with long-detection strategy in patients with pre-existing implantable cardioverter-defibrillator

Background: A long-detection interval (LDI) programming has been proved to reduce shock therapy in patients who underwent de novo implantable cardioverter defibrillator (ICD) implantation. We aimed to evaluate effectiveness and safety of this new strategy in old ICD recipients. Methods: We included 147 primary prevention patients with ischaemic and non-ischaemic aetiology. Conventional setting parameters (18 of 24 intervals to detect ventricular arrhythmias (VA's)) were reprogrammed with LDI strategy (30 of 40 intervals to detect VA's). One monitoring zone (between 360 and 330 ms) and two therapy zones were programmed, treating all rhythms of cycle length <330 ms that met the duration criterion of 30/40 intervals and were discriminated as ventricular tachycardia/ventricular fibrillation (VT/VF). The supraventricular tachycardia (SVT) discriminators were used in all patients. Results: At a median follow-up of 24 months, 12.9% (n = 19) of patients received shock therapies (± antitachycardia pacing (ATP)). Appropriate and inappropriate shocks occurred in 7.5 and 5.4% of patients during follow-up, respectively. Only one patient experienced an arrhythmic syncope during the follow-up period. There was no death related to LDI programming. The LDI programming helped to stop unnecessary in 10 patients (6.8%), who otherwise would have been treated in the conventional programming. Conclusions: LDI programming was found safe and effective. Hence, old ICD recipients will benefit from this strategy.

Comparing pleasure and pain: the fundamental mathematical equivalence of reward gain and shock reduction under variable interval schedules

The relationship between positive and negative reinforcement and the symmetry of Thorndike's law of effect are unresolved issues in operant psychology. Here we show that, for a given pattern of responding on variable interval (VI) schedules with the same programmed rate of food rewards (positive reinforcement VI) or electric shocks (negative reinforcement VI), there is a fundamental mathematical equivalence between reward gain and shock reduction. We also provide the first normative account of how animals should respond on a negative VI schedule, showing that it is better to space responses evenly than to respond with a variable interresponse time (IRT). Published data from rats, however, indicate that these animals respond irregularly, often with a burst of activity immediately following a shock. While this is irrational in the experimental setting, it may represent an appropriate response to the heterogeneity of stimuli commonly encountered in natural environments. We discuss the broader implications of our analysis for understanding how animals evaluate appetitive and aversive stimuli.