Is it safe to program a long tachycardia detection interval?
Implantable cardioverter defibrillator (ICD) therapy is used frequently in patients with "slow" ventricular tachycardia (VT). Hence, the tachycardia detection interval is programmed within the range of the physiologic heart rate, but this may cause serious problems. If a fast VT is converted to sinus tachycardia with a cycle length shorter than the tachycardia detection interval, the episode is not terminated and the success counter is not reset. If this happens repeatedly, therapies will be exhausted without termination of the episode. If VT recurs within such an episode, it will not be treated. This report describes a patient who died suddenly in a scenario similar to the one described. Although all documented VT/ventricular fibrillation episodes were terminated by the device, the episode was not terminated because of the ongoing supraventricular tachycardia. Therefore, no further therapies were available and the patient probably died of fast untreated VT. Programming of a long tachycardia detection interval is dangerous in currently available ICDs.