Abstract: A system and method are provided for inducing ventricular tachycardia in a patient to enable testing to determine the optimum parameters for anti-tachycardia stimulation. The implantable device provides for overdrive pacing of the heart for a short sequence, followed by delivery of a series of pulse pairs. Each pulse pair has a first stimulus pulse delivered at the same or similar overdrive rate, and an inducing pulse which is delivered in timed relation to the evoked T-wave, preferably during the falling edge portion of the T-wave. In this way, each cycle the inducing pulse is timed for efficaciously inducing tachycardia. The timing of the inducing pulse is enhanced by near field sensing of the T-wave at about the location where the pulses are delivered, preferably using bipolar sensing and/or sense circuitry designed to recover the signal with an optimum time response.

Abstract: A device for detection and treatment of tachycardias, which is able to selectively identify the occurrence of re-entrant AV nodal tachycardia, and to distinguish it from sinus tachycardias. The apparatus monitors the occurrence of atrial and ventricular depolarizations during a detected tachycardia, and, in the event that a series of ventricular depolarizations occur which are each closely preceded or closely followed by an atrial depolarization, at an interval substantially less than would be expected in the case of a sinus tachycardia, re-entrant AV nodal tachycardia is identified, and an appropriate therapy regimen is triggered.

Abstract: A dual chamber pacemaker is provided, preferably either DDDR or DDIR, having logic hardware and/or software for normally carrying out the DDIR or DDDR mode of operation, and further having means for avoiding delivery of an atrial pace pulse in circumstances where normal atrial pacing could otherwise be competitive or result in loss of atrial capture. The pacemaker has means for detecting an atrial sense during PVARP, timing out a delay from the time of the early atrial sense, and inhibiting delivery of an atrial pulse during the delay. In a preferred embodiment, the ventricular rate, which may be established by a rate responsive sensor, is maintained, while atrial sync pulses are delivered whenever possible following an early atrial sense so as to provide synchronous pacing whenever that is consistent with safe atrial pacing and substantial regularity of the ventricular pacing.